[www-releases] r242418 - Add 3.6.2 docs.
Tom Stellard
thomas.stellard at amd.com
Thu Jul 16 09:56:03 PDT 2015
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-config.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-config.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-config.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-config.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,176 @@
+llvm-config - Print LLVM compilation options
+============================================
+
+
+SYNOPSIS
+--------
+
+
+**llvm-config** *option* [*components*...]
+
+
+DESCRIPTION
+-----------
+
+
+**llvm-config** makes it easier to build applications that use LLVM. It can
+print the compiler flags, linker flags and object libraries needed to link
+against LLVM.
+
+
+EXAMPLES
+--------
+
+
+To link against the JIT:
+
+
+.. code-block:: sh
+
+ g++ `llvm-config --cxxflags` -o HowToUseJIT.o -c HowToUseJIT.cpp
+ g++ `llvm-config --ldflags` -o HowToUseJIT HowToUseJIT.o \
+ `llvm-config --libs engine bcreader scalaropts`
+
+
+
+OPTIONS
+-------
+
+
+
+**--version**
+
+ Print the version number of LLVM.
+
+
+
+**-help**
+
+ Print a summary of **llvm-config** arguments.
+
+
+
+**--prefix**
+
+ Print the installation prefix for LLVM.
+
+
+
+**--src-root**
+
+ Print the source root from which LLVM was built.
+
+
+
+**--obj-root**
+
+ Print the object root used to build LLVM.
+
+
+
+**--bindir**
+
+ Print the installation directory for LLVM binaries.
+
+
+
+**--includedir**
+
+ Print the installation directory for LLVM headers.
+
+
+
+**--libdir**
+
+ Print the installation directory for LLVM libraries.
+
+
+
+**--cxxflags**
+
+ Print the C++ compiler flags needed to use LLVM headers.
+
+
+
+**--ldflags**
+
+ Print the flags needed to link against LLVM libraries.
+
+
+
+**--libs**
+
+ Print all the libraries needed to link against the specified LLVM
+ *components*, including any dependencies.
+
+
+
+**--libnames**
+
+ Similar to **--libs**, but prints the bare filenames of the libraries
+ without **-l** or pathnames. Useful for linking against a not-yet-installed
+ copy of LLVM.
+
+
+
+**--libfiles**
+
+ Similar to **--libs**, but print the full path to each library file. This is
+ useful when creating makefile dependencies, to ensure that a tool is relinked if
+ any library it uses changes.
+
+
+
+**--components**
+
+ Print all valid component names.
+
+
+
+**--targets-built**
+
+ Print the component names for all targets supported by this copy of LLVM.
+
+
+
+**--build-mode**
+
+ Print the build mode used when LLVM was built (e.g. Debug or Release)
+
+
+
+
+COMPONENTS
+----------
+
+
+To print a list of all available components, run **llvm-config
+--components**. In most cases, components correspond directly to LLVM
+libraries. Useful "virtual" components include:
+
+
+**all**
+
+ Includes all LLVM libraries. The default if no components are specified.
+
+
+
+**backend**
+
+ Includes either a native backend or the C backend.
+
+
+
+**engine**
+
+ Includes either a native JIT or the bitcode interpreter.
+
+
+
+
+EXIT STATUS
+-----------
+
+
+If **llvm-config** succeeds, it will exit with 0. Otherwise, if an error
+occurs, it will exit with a non-zero value.
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-cov.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-cov.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-cov.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-cov.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,127 @@
+llvm-cov - emit coverage information
+====================================
+
+SYNOPSIS
+--------
+
+:program:`llvm-cov` [options] SOURCEFILE
+
+DESCRIPTION
+-----------
+
+The :program:`llvm-cov` tool reads code coverage data files and displays the
+coverage information for a specified source file. It is compatible with the
+``gcov`` tool from version 4.2 of ``GCC`` and may also be compatible with
+some later versions of ``gcov``.
+
+To use llvm-cov, you must first build an instrumented version of your
+application that collects coverage data as it runs. Compile with the
+``-fprofile-arcs`` and ``-ftest-coverage`` options to add the
+instrumentation. (Alternatively, you can use the ``--coverage`` option, which
+includes both of those other options.) You should compile with debugging
+information (``-g``) and without optimization (``-O0``); otherwise, the
+coverage data cannot be accurately mapped back to the source code.
+
+At the time you compile the instrumented code, a ``.gcno`` data file will be
+generated for each object file. These ``.gcno`` files contain half of the
+coverage data. The other half of the data comes from ``.gcda`` files that are
+generated when you run the instrumented program, with a separate ``.gcda``
+file for each object file. Each time you run the program, the execution counts
+are summed into any existing ``.gcda`` files, so be sure to remove any old
+files if you do not want their contents to be included.
+
+By default, the ``.gcda`` files are written into the same directory as the
+object files, but you can override that by setting the ``GCOV_PREFIX`` and
+``GCOV_PREFIX_STRIP`` environment variables. The ``GCOV_PREFIX_STRIP``
+variable specifies a number of directory components to be removed from the
+start of the absolute path to the object file directory. After stripping those
+directories, the prefix from the ``GCOV_PREFIX`` variable is added. These
+environment variables allow you to run the instrumented program on a machine
+where the original object file directories are not accessible, but you will
+then need to copy the ``.gcda`` files back to the object file directories
+where llvm-cov expects to find them.
+
+Once you have generated the coverage data files, run llvm-cov for each main
+source file where you want to examine the coverage results. This should be run
+from the same directory where you previously ran the compiler. The results for
+the specified source file are written to a file named by appending a ``.gcov``
+suffix. A separate output file is also created for each file included by the
+main source file, also with a ``.gcov`` suffix added.
+
+The basic content of an llvm-cov output file is a copy of the source file with
+an execution count and line number prepended to every line. The execution
+count is shown as ``-`` if a line does not contain any executable code. If
+a line contains code but that code was never executed, the count is displayed
+as ``#####``.
+
+
+OPTIONS
+-------
+
+.. option:: -a, --all-blocks
+
+ Display all basic blocks. If there are multiple blocks for a single line of
+ source code, this option causes llvm-cov to show the count for each block
+ instead of just one count for the entire line.
+
+.. option:: -b, --branch-probabilities
+
+ Display conditional branch probabilities and a summary of branch information.
+
+.. option:: -c, --branch-counts
+
+ Display branch counts instead of probabilities (requires -b).
+
+.. option:: -f, --function-summaries
+
+ Show a summary of coverage for each function instead of just one summary for
+ an entire source file.
+
+.. option:: --help
+
+ Display available options (--help-hidden for more).
+
+.. option:: -l, --long-file-names
+
+ For coverage output of files included from the main source file, add the
+ main file name followed by ``##`` as a prefix to the output file names. This
+ can be combined with the --preserve-paths option to use complete paths for
+ both the main file and the included file.
+
+.. option:: -n, --no-output
+
+ Do not output any ``.gcov`` files. Summary information is still
+ displayed.
+
+.. option:: -o=<DIR|FILE>, --object-directory=<DIR>, --object-file=<FILE>
+
+ Find objects in DIR or based on FILE's path. If you specify a particular
+ object file, the coverage data files are expected to have the same base name
+ with ``.gcno`` and ``.gcda`` extensions. If you specify a directory, the
+ files are expected in that directory with the same base name as the source
+ file.
+
+.. option:: -p, --preserve-paths
+
+ Preserve path components when naming the coverage output files. In addition
+ to the source file name, include the directories from the path to that
+ file. The directories are separate by ``#`` characters, with ``.`` directories
+ removed and ``..`` directories replaced by ``^`` characters. When used with
+ the --long-file-names option, this applies to both the main file name and the
+ included file name.
+
+.. option:: -u, --unconditional-branches
+
+ Include unconditional branches in the output for the --branch-probabilities
+ option.
+
+.. option:: -version
+
+ Display the version of llvm-cov.
+
+EXIT STATUS
+-----------
+
+:program:`llvm-cov` returns 1 if it cannot read input files. Otherwise, it
+exits with zero.
+
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-diff.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-diff.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-diff.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-diff.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,56 @@
+llvm-diff - LLVM structural 'diff'
+==================================
+
+
+SYNOPSIS
+--------
+
+
+**llvm-diff** [*options*] *module 1* *module 2* [*global name ...*]
+
+
+DESCRIPTION
+-----------
+
+
+**llvm-diff** compares the structure of two LLVM modules, primarily
+focusing on differences in function definitions. Insignificant
+differences, such as changes in the ordering of globals or in the
+names of local values, are ignored.
+
+An input module will be interpreted as an assembly file if its name
+ends in '.ll'; otherwise it will be read in as a bitcode file.
+
+If a list of global names is given, just the values with those names
+are compared; otherwise, all global values are compared, and
+diagnostics are produced for globals which only appear in one module
+or the other.
+
+**llvm-diff** compares two functions by comparing their basic blocks,
+beginning with the entry blocks. If the terminators seem to match,
+then the corresponding successors are compared; otherwise they are
+ignored. This algorithm is very sensitive to changes in control flow,
+which tend to stop any downstream changes from being detected.
+
+**llvm-diff** is intended as a debugging tool for writers of LLVM
+passes and frontends. It does not have a stable output format.
+
+
+EXIT STATUS
+-----------
+
+
+If **llvm-diff** finds no differences between the modules, it will exit
+with 0 and produce no output. Otherwise it will exit with a non-zero
+value.
+
+
+BUGS
+----
+
+
+Many important differences, like changes in linkage or function
+attributes, are not diagnosed.
+
+Changes in memory behavior (for example, coalescing loads) can cause
+massive detected differences in blocks.
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-dis.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-dis.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-dis.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-dis.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,69 @@
+llvm-dis - LLVM disassembler
+============================
+
+
+SYNOPSIS
+--------
+
+
+**llvm-dis** [*options*] [*filename*]
+
+
+DESCRIPTION
+-----------
+
+
+The **llvm-dis** command is the LLVM disassembler. It takes an LLVM
+bitcode file and converts it into human-readable LLVM assembly language.
+
+If filename is omitted or specified as ``-``, **llvm-dis** reads its
+input from standard input.
+
+If the input is being read from standard input, then **llvm-dis**
+will send its output to standard output by default. Otherwise, the
+output will be written to a file named after the input file, with
+a ``.ll`` suffix added (any existing ``.bc`` suffix will first be
+removed). You can override the choice of output file using the
+**-o** option.
+
+
+OPTIONS
+-------
+
+
+
+**-f**
+
+ Enable binary output on terminals. Normally, **llvm-dis** will refuse to
+ write raw bitcode output if the output stream is a terminal. With this option,
+ **llvm-dis** will write raw bitcode regardless of the output device.
+
+
+
+**-help**
+
+ Print a summary of command line options.
+
+
+
+**-o** *filename*
+
+ Specify the output file name. If *filename* is -, then the output is sent
+ to standard output.
+
+
+
+
+EXIT STATUS
+-----------
+
+
+If **llvm-dis** succeeds, it will exit with 0. Otherwise, if an error
+occurs, it will exit with a non-zero value.
+
+
+SEE ALSO
+--------
+
+
+llvm-as|llvm-as
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-dwarfdump.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-dwarfdump.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-dwarfdump.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-dwarfdump.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,30 @@
+llvm-dwarfdump - print contents of DWARF sections
+=================================================
+
+SYNOPSIS
+--------
+
+:program:`llvm-dwarfdump` [*options*] [*filenames...*]
+
+DESCRIPTION
+-----------
+
+:program:`llvm-dwarfdump` parses DWARF sections in the object files
+and prints their contents in human-readable form.
+
+OPTIONS
+-------
+
+.. option:: -debug-dump=section
+
+ Specify the DWARF section to dump.
+ For example, use ``abbrev`` to dump the contents of ``.debug_abbrev`` section,
+ ``loc.dwo`` to dump the contents of ``.debug_loc.dwo`` etc.
+ See ``llvm-dwarfdump --help`` for the complete list of supported sections.
+ Use ``all`` to dump all DWARF sections. It is the default.
+
+EXIT STATUS
+-----------
+
+:program:`llvm-dwarfdump` returns 0. Other exit codes imply internal
+program error.
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-extract.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-extract.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-extract.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-extract.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,79 @@
+llvm-extract - extract a function from an LLVM module
+=====================================================
+
+SYNOPSIS
+--------
+
+:program:`llvm-extract` [*options*] **--func** *function-name* [*filename*]
+
+DESCRIPTION
+-----------
+
+The :program:`llvm-extract` command takes the name of a function and extracts
+it from the specified LLVM bitcode file. It is primarily used as a debugging
+tool to reduce test cases from larger programs that are triggering a bug.
+
+In addition to extracting the bitcode of the specified function,
+:program:`llvm-extract` will also remove unreachable global variables,
+prototypes, and unused types.
+
+The :program:`llvm-extract` command reads its input from standard input if
+filename is omitted or if filename is ``-``. The output is always written to
+standard output, unless the **-o** option is specified (see below).
+
+OPTIONS
+-------
+
+**-f**
+
+ Enable binary output on terminals. Normally, :program:`llvm-extract` will
+ refuse to write raw bitcode output if the output stream is a terminal. With
+ this option, :program:`llvm-extract` will write raw bitcode regardless of the
+ output device.
+
+**--func** *function-name*
+
+ Extract the function named *function-name* from the LLVM bitcode. May be
+ specified multiple times to extract multiple functions at once.
+
+**--rfunc** *function-regular-expr*
+
+ Extract the function(s) matching *function-regular-expr* from the LLVM bitcode.
+ All functions matching the regular expression will be extracted. May be
+ specified multiple times.
+
+**--glob** *global-name*
+
+ Extract the global variable named *global-name* from the LLVM bitcode. May be
+ specified multiple times to extract multiple global variables at once.
+
+**--rglob** *glob-regular-expr*
+
+ Extract the global variable(s) matching *global-regular-expr* from the LLVM
+ bitcode. All global variables matching the regular expression will be
+ extracted. May be specified multiple times.
+
+**-help**
+
+ Print a summary of command line options.
+
+**-o** *filename*
+
+ Specify the output filename. If filename is "-" (the default), then
+ :program:`llvm-extract` sends its output to standard output.
+
+**-S**
+
+ Write output in LLVM intermediate language (instead of bitcode).
+
+EXIT STATUS
+-----------
+
+If :program:`llvm-extract` succeeds, it will exit with 0. Otherwise, if an error
+occurs, it will exit with a non-zero value.
+
+SEE ALSO
+--------
+
+bugpoint
+
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-link.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-link.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-link.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-link.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,56 @@
+llvm-link - LLVM bitcode linker
+===============================
+
+SYNOPSIS
+--------
+
+:program:`llvm-link` [*options*] *filename ...*
+
+DESCRIPTION
+-----------
+
+:program:`llvm-link` takes several LLVM bitcode files and links them together
+into a single LLVM bitcode file. It writes the output file to standard output,
+unless the :option:`-o` option is used to specify a filename.
+
+OPTIONS
+-------
+
+.. option:: -f
+
+ Enable binary output on terminals. Normally, :program:`llvm-link` will refuse
+ to write raw bitcode output if the output stream is a terminal. With this
+ option, :program:`llvm-link` will write raw bitcode regardless of the output
+ device.
+
+.. option:: -o filename
+
+ Specify the output file name. If ``filename`` is "``-``", then
+ :program:`llvm-link` will write its output to standard output.
+
+.. option:: -S
+
+ Write output in LLVM intermediate language (instead of bitcode).
+
+.. option:: -d
+
+ If specified, :program:`llvm-link` prints a human-readable version of the
+ output bitcode file to standard error.
+
+.. option:: -help
+
+ Print a summary of command line options.
+
+.. option:: -v
+
+ Verbose mode. Print information about what :program:`llvm-link` is doing.
+ This typically includes a message for each bitcode file linked in and for each
+ library found.
+
+EXIT STATUS
+-----------
+
+If :program:`llvm-link` succeeds, it will exit with 0. Otherwise, if an error
+occurs, it will exit with a non-zero value.
+
+
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-nm.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-nm.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-nm.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-nm.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,146 @@
+llvm-nm - list LLVM bitcode and object file's symbol table
+==========================================================
+
+SYNOPSIS
+--------
+
+:program:`llvm-nm` [*options*] [*filenames...*]
+
+DESCRIPTION
+-----------
+
+The :program:`llvm-nm` utility lists the names of symbols from the LLVM bitcode
+files, object files, or :program:`ar` archives containing them, named on the
+command line. Each symbol is listed along with some simple information about
+its provenance. If no file name is specified, or *-* is used as a file name,
+:program:`llvm-nm` will process a file on its standard input stream.
+
+:program:`llvm-nm`'s default output format is the traditional BSD :program:`nm`
+output format. Each such output record consists of an (optional) 8-digit
+hexadecimal address, followed by a type code character, followed by a name, for
+each symbol. One record is printed per line; fields are separated by spaces.
+When the address is omitted, it is replaced by 8 spaces.
+
+Type code characters currently supported, and their meanings, are as follows:
+
+U
+
+ Named object is referenced but undefined in this bitcode file
+
+C
+
+ Common (multiple definitions link together into one def)
+
+W
+
+ Weak reference (multiple definitions link together into zero or one definitions)
+
+t
+
+ Local function (text) object
+
+T
+
+ Global function (text) object
+
+d
+
+ Local data object
+
+D
+
+ Global data object
+
+?
+
+ Something unrecognizable
+
+Because LLVM bitcode files typically contain objects that are not considered to
+have addresses until they are linked into an executable image or dynamically
+compiled "just-in-time", :program:`llvm-nm` does not print an address for any
+symbol in an LLVM bitcode file, even symbols which are defined in the bitcode
+file.
+
+OPTIONS
+-------
+
+.. program:: llvm-nm
+
+.. option:: -B (default)
+
+ Use BSD output format. Alias for :option:`--format=bsd`.
+
+.. option:: -P
+
+ Use POSIX.2 output format. Alias for :option:`--format=posix`.
+
+.. option:: --debug-syms, -a
+
+ Show all symbols, even debugger only.
+
+.. option:: --defined-only
+
+ Print only symbols defined in this file (as opposed to
+ symbols which may be referenced by objects in this file, but not
+ defined in this file.)
+
+.. option:: --dynamic, -D
+
+ Display dynamic symbols instead of normal symbols.
+
+.. option:: --extern-only, -g
+
+ Print only symbols whose definitions are external; that is, accessible
+ from other files.
+
+.. option:: --format=format, -f format
+
+ Select an output format; *format* may be *sysv*, *posix*, or *bsd*. The default
+ is *bsd*.
+
+.. option:: -help
+
+ Print a summary of command-line options and their meanings.
+
+.. option:: --no-sort, -p
+
+ Shows symbols in order encountered.
+
+.. option:: --numeric-sort, -n, -v
+
+ Sort symbols by address.
+
+.. option:: --print-file-name, -A, -o
+
+ Precede each symbol with the file it came from.
+
+.. option:: --print-size, -S
+
+ Show symbol size instead of address.
+
+.. option:: --size-sort
+
+ Sort symbols by size.
+
+.. option:: --undefined-only, -u
+
+ Print only symbols referenced but not defined in this file.
+
+BUGS
+----
+
+ * :program:`llvm-nm` cannot demangle C++ mangled names, like GNU :program:`nm`
+ can.
+
+ * :program:`llvm-nm` does not support the full set of arguments that GNU
+ :program:`nm` does.
+
+EXIT STATUS
+-----------
+
+:program:`llvm-nm` exits with an exit code of zero.
+
+SEE ALSO
+--------
+
+llvm-dis, ar(1), nm(1)
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-profdata.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-profdata.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-profdata.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-profdata.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,102 @@
+llvm-profdata - Profile data tool
+=================================
+
+SYNOPSIS
+--------
+
+:program:`llvm-profdata` *command* [*args...*]
+
+DESCRIPTION
+-----------
+
+The :program:`llvm-profdata` tool is a small utility for working with profile
+data files.
+
+COMMANDS
+--------
+
+* `merge <profdata_merge_>`_
+* `show <profdata_show_>`_
+
+.. program:: llvm-profdata merge
+
+.. _profdata_merge:
+
+MERGE
+-----
+
+SYNOPSIS
+^^^^^^^^
+
+:program:`llvm-profdata merge` [*options*] [*filenames...*]
+
+DESCRIPTION
+^^^^^^^^^^^
+
+:program:`llvm-profdata merge` takes several profile data files
+generated by PGO instrumentation and merges them together into a single
+indexed profile data file.
+
+OPTIONS
+^^^^^^^
+
+.. option:: -help
+
+ Print a summary of command line options.
+
+.. option:: -output=output, -o=output
+
+ Specify the output file name. *Output* cannot be ``-`` as the resulting
+ indexed profile data can't be written to standard output.
+
+.. program:: llvm-profdata show
+
+.. _profdata_show:
+
+SHOW
+----
+
+SYNOPSIS
+^^^^^^^^
+
+:program:`llvm-profdata show` [*options*] [*filename*]
+
+DESCRIPTION
+^^^^^^^^^^^
+
+:program:`llvm-profdata show` takes a profile data file and displays the
+information about the profile counters for this file and
+for any of the specified function(s).
+
+If *filename* is omitted or is ``-``, then **llvm-profdata show** reads its
+input from standard input.
+
+OPTIONS
+^^^^^^^
+
+.. option:: -all-functions
+
+ Print details for every function.
+
+.. option:: -counts
+
+ Print the counter values for the displayed functions.
+
+.. option:: -function=string
+
+ Print details for a function if the function's name contains the given string.
+
+.. option:: -help
+
+ Print a summary of command line options.
+
+.. option:: -output=output, -o=output
+
+ Specify the output file name. If *output* is ``-`` or it isn't specified,
+ then the output is sent to standard output.
+
+EXIT STATUS
+-----------
+
+:program:`llvm-profdata` returns 1 if the command is omitted or is invalid,
+if it cannot read input files, or if there is a mismatch between their data.
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-readobj.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-readobj.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-readobj.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-readobj.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,86 @@
+llvm-readobj - LLVM Object Reader
+=================================
+
+SYNOPSIS
+--------
+
+:program:`llvm-readobj` [*options*] [*input...*]
+
+DESCRIPTION
+-----------
+
+The :program:`llvm-readobj` tool displays low-level format-specific information
+about one or more object files. The tool and its output is primarily designed
+for use in FileCheck-based tests.
+
+OPTIONS
+-------
+
+If ``input`` is "``-``" or omitted, :program:`llvm-readobj` reads from standard
+input. Otherwise, it will read from the specified ``filenames``.
+
+.. option:: -help
+
+ Print a summary of command line options.
+
+.. option:: -version
+
+ Display the version of this program
+
+.. option:: -file-headers, -h
+
+ Display file headers.
+
+.. option:: -sections, -s
+
+ Display all sections.
+
+.. option:: -section-data, -sd
+
+ When used with ``-sections``, display section data for each section shown.
+
+.. option:: -section-relocations, -sr
+
+ When used with ``-sections``, display relocations for each section shown.
+
+.. option:: -section-symbols, -st
+
+ When used with ``-sections``, display symbols for each section shown.
+
+.. option:: -relocations, -r
+
+ Display the relocation entries in the file.
+
+.. option:: -symbols, -t
+
+ Display the symbol table.
+
+.. option:: -dyn-symbols
+
+ Display the dynamic symbol table (only for ELF object files).
+
+.. option:: -unwind, -u
+
+ Display unwind information.
+
+.. option:: -expand-relocs
+
+ When used with ``-relocations``, display each relocation in an expanded
+ multi-line format.
+
+.. option:: -dynamic-table
+
+ Display the ELF .dynamic section table (only for ELF object files).
+
+.. option:: -needed-libs
+
+ Display the needed libraries (only for ELF object files).
+
+.. option:: -program-headers
+
+ Display the ELF program headers (only for ELF object files).
+
+EXIT STATUS
+-----------
+
+:program:`llvm-readobj` returns 0.
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-stress.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-stress.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-stress.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-stress.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,34 @@
+llvm-stress - generate random .ll files
+=======================================
+
+SYNOPSIS
+--------
+
+:program:`llvm-stress` [-size=filesize] [-seed=initialseed] [-o=outfile]
+
+DESCRIPTION
+-----------
+
+The :program:`llvm-stress` tool is used to generate random ``.ll`` files that
+can be used to test different components of LLVM.
+
+OPTIONS
+-------
+
+.. option:: -o filename
+
+ Specify the output filename.
+
+.. option:: -size size
+
+ Specify the size of the generated ``.ll`` file.
+
+.. option:: -seed seed
+
+ Specify the seed to be used for the randomly generated instructions.
+
+EXIT STATUS
+-----------
+
+:program:`llvm-stress` returns 0.
+
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-symbolizer.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-symbolizer.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-symbolizer.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/llvm-symbolizer.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,105 @@
+llvm-symbolizer - convert addresses into source code locations
+==============================================================
+
+SYNOPSIS
+--------
+
+:program:`llvm-symbolizer` [options]
+
+DESCRIPTION
+-----------
+
+:program:`llvm-symbolizer` reads object file names and addresses from standard
+input and prints corresponding source code locations to standard output.
+If object file is specified in command line, :program:`llvm-symbolizer` reads
+only addresses from standard input. This
+program uses debug info sections and symbol table in the object files.
+
+EXAMPLE
+--------
+
+.. code-block:: console
+
+ $ cat addr.txt
+ a.out 0x4004f4
+ /tmp/b.out 0x400528
+ /tmp/c.so 0x710
+ /tmp/mach_universal_binary:i386 0x1f84
+ /tmp/mach_universal_binary:x86_64 0x100000f24
+ $ llvm-symbolizer < addr.txt
+ main
+ /tmp/a.cc:4
+
+ f(int, int)
+ /tmp/b.cc:11
+
+ h_inlined_into_g
+ /tmp/header.h:2
+ g_inlined_into_f
+ /tmp/header.h:7
+ f_inlined_into_main
+ /tmp/source.cc:3
+ main
+ /tmp/source.cc:8
+
+ _main
+ /tmp/source_i386.cc:8
+
+ _main
+ /tmp/source_x86_64.cc:8
+ $ cat addr2.txt
+ 0x4004f4
+ 0x401000
+ $ llvm-symbolizer -obj=a.out < addr2.txt
+ main
+ /tmp/a.cc:4
+
+ foo(int)
+ /tmp/a.cc:12
+
+OPTIONS
+-------
+
+.. option:: -obj
+
+ Path to object file to be symbolized.
+
+.. option:: -functions=[none|short|linkage]
+
+ Specify the way function names are printed (omit function name,
+ print short function name, or print full linkage name, respectively).
+ Defaults to ``linkage``.
+
+.. option:: -use-symbol-table
+
+ Prefer function names stored in symbol table to function names
+ in debug info sections. Defaults to true.
+
+.. option:: -demangle
+
+ Print demangled function names. Defaults to true.
+
+.. option:: -inlining
+
+ If a source code location is in an inlined function, prints all the
+ inlnied frames. Defaults to true.
+
+.. option:: -default-arch
+
+ If a binary contains object files for multiple architectures (e.g. it is a
+ Mach-O universal binary), symbolize the object file for a given architecture.
+ You can also specify architecture by writing ``binary_name:arch_name`` in the
+ input (see example above). If architecture is not specified in either way,
+ address will not be symbolized. Defaults to empty string.
+
+.. option:: -dsym-hint=<path/to/file.dSYM>
+
+ (Darwin-only flag). If the debug info for a binary isn't present in the default
+ location, look for the debug info at the .dSYM path provided via the
+ ``-dsym-hint`` flag. This flag can be used multiple times.
+
+
+EXIT STATUS
+-----------
+
+:program:`llvm-symbolizer` returns 0. Other exit codes imply internal program error.
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/opt.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/opt.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/opt.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/opt.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,123 @@
+opt - LLVM optimizer
+====================
+
+SYNOPSIS
+--------
+
+:program:`opt` [*options*] [*filename*]
+
+DESCRIPTION
+-----------
+
+The :program:`opt` command is the modular LLVM optimizer and analyzer. It
+takes LLVM source files as input, runs the specified optimizations or analyses
+on it, and then outputs the optimized file or the analysis results. The
+function of :program:`opt` depends on whether the :option:`-analyze` option is
+given.
+
+When :option:`-analyze` is specified, :program:`opt` performs various analyses
+of the input source. It will usually print the results on standard output, but
+in a few cases, it will print output to standard error or generate a file with
+the analysis output, which is usually done when the output is meant for another
+program.
+
+While :option:`-analyze` is *not* given, :program:`opt` attempts to produce an
+optimized output file. The optimizations available via :program:`opt` depend
+upon what libraries were linked into it as well as any additional libraries
+that have been loaded with the :option:`-load` option. Use the :option:`-help`
+option to determine what optimizations you can use.
+
+If ``filename`` is omitted from the command line or is "``-``", :program:`opt`
+reads its input from standard input. Inputs can be in either the LLVM assembly
+language format (``.ll``) or the LLVM bitcode format (``.bc``).
+
+If an output filename is not specified with the :option:`-o` option,
+:program:`opt` writes its output to the standard output.
+
+OPTIONS
+-------
+
+.. option:: -f
+
+ Enable binary output on terminals. Normally, :program:`opt` will refuse to
+ write raw bitcode output if the output stream is a terminal. With this option,
+ :program:`opt` will write raw bitcode regardless of the output device.
+
+.. option:: -help
+
+ Print a summary of command line options.
+
+.. option:: -o <filename>
+
+ Specify the output filename.
+
+.. option:: -S
+
+ Write output in LLVM intermediate language (instead of bitcode).
+
+.. option:: -{passname}
+
+ :program:`opt` provides the ability to run any of LLVM's optimization or
+ analysis passes in any order. The :option:`-help` option lists all the passes
+ available. The order in which the options occur on the command line are the
+ order in which they are executed (within pass constraints).
+
+.. option:: -disable-inlining
+
+ This option simply removes the inlining pass from the standard list.
+
+.. option:: -disable-opt
+
+ This option is only meaningful when :option:`-std-link-opts` is given. It
+ disables most passes.
+
+.. option:: -strip-debug
+
+ This option causes opt to strip debug information from the module before
+ applying other optimizations. It is essentially the same as :option:`-strip`
+ but it ensures that stripping of debug information is done first.
+
+.. option:: -verify-each
+
+ This option causes opt to add a verify pass after every pass otherwise
+ specified on the command line (including :option:`-verify`). This is useful
+ for cases where it is suspected that a pass is creating an invalid module but
+ it is not clear which pass is doing it.
+
+.. option:: -stats
+
+ Print statistics.
+
+.. option:: -time-passes
+
+ Record the amount of time needed for each pass and print it to standard
+ error.
+
+.. option:: -debug
+
+ If this is a debug build, this option will enable debug printouts from passes
+ which use the ``DEBUG()`` macro. See the `LLVM Programmer's Manual
+ <../ProgrammersManual.html>`_, section ``#DEBUG`` for more information.
+
+.. option:: -load=<plugin>
+
+ Load the dynamic object ``plugin``. This object should register new
+ optimization or analysis passes. Once loaded, the object will add new command
+ line options to enable various optimizations or analyses. To see the new
+ complete list of optimizations, use the :option:`-help` and :option:`-load`
+ options together. For example:
+
+ .. code-block:: sh
+
+ opt -load=plugin.so -help
+
+.. option:: -p
+
+ Print module after each transformation.
+
+EXIT STATUS
+-----------
+
+If :program:`opt` succeeds, it will exit with 0. Otherwise, if an error
+occurs, it will exit with a non-zero value.
+
Added: www-releases/trunk/3.6.2/docs/_sources/CommandGuide/tblgen.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandGuide/tblgen.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandGuide/tblgen.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandGuide/tblgen.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,132 @@
+tblgen - Target Description To C++ Code Generator
+=================================================
+
+SYNOPSIS
+--------
+
+:program:`tblgen` [*options*] [*filename*]
+
+DESCRIPTION
+-----------
+
+:program:`tblgen` translates from target description (``.td``) files into C++
+code that can be included in the definition of an LLVM target library. Most
+users of LLVM will not need to use this program. It is only for assisting with
+writing an LLVM target backend.
+
+The input and output of :program:`tblgen` is beyond the scope of this short
+introduction; please see the :doc:`introduction to TableGen
+<../TableGen/index>`.
+
+The *filename* argument specifies the name of a Target Description (``.td``)
+file to read as input.
+
+OPTIONS
+-------
+
+.. program:: tblgen
+
+.. option:: -help
+
+ Print a summary of command line options.
+
+.. option:: -o filename
+
+ Specify the output file name. If ``filename`` is ``-``, then
+ :program:`tblgen` sends its output to standard output.
+
+.. option:: -I directory
+
+ Specify where to find other target description files for inclusion. The
+ ``directory`` value should be a full or partial path to a directory that
+ contains target description files.
+
+.. option:: -asmparsernum N
+
+ Make -gen-asm-parser emit assembly writer number ``N``.
+
+.. option:: -asmwriternum N
+
+ Make -gen-asm-writer emit assembly writer number ``N``.
+
+.. option:: -class className
+
+ Print the enumeration list for this class.
+
+.. option:: -print-records
+
+ Print all records to standard output (default).
+
+.. option:: -print-enums
+
+ Print enumeration values for a class.
+
+.. option:: -print-sets
+
+ Print expanded sets for testing DAG exprs.
+
+.. option:: -gen-emitter
+
+ Generate machine code emitter.
+
+.. option:: -gen-register-info
+
+ Generate registers and register classes info.
+
+.. option:: -gen-instr-info
+
+ Generate instruction descriptions.
+
+.. option:: -gen-asm-writer
+
+ Generate the assembly writer.
+
+.. option:: -gen-disassembler
+
+ Generate disassembler.
+
+.. option:: -gen-pseudo-lowering
+
+ Generate pseudo instruction lowering.
+
+.. option:: -gen-dag-isel
+
+ Generate a DAG (Directed Acycle Graph) instruction selector.
+
+.. option:: -gen-asm-matcher
+
+ Generate assembly instruction matcher.
+
+.. option:: -gen-dfa-packetizer
+
+ Generate DFA Packetizer for VLIW targets.
+
+.. option:: -gen-fast-isel
+
+ Generate a "fast" instruction selector.
+
+.. option:: -gen-subtarget
+
+ Generate subtarget enumerations.
+
+.. option:: -gen-intrinsic
+
+ Generate intrinsic information.
+
+.. option:: -gen-tgt-intrinsic
+
+ Generate target intrinsic information.
+
+.. option:: -gen-enhanced-disassembly-info
+
+ Generate enhanced disassembly info.
+
+.. option:: -version
+
+ Show the version number of this program.
+
+EXIT STATUS
+-----------
+
+If :program:`tblgen` succeeds, it will exit with 0. Otherwise, if an error
+occurs, it will exit with a non-zero value.
Added: www-releases/trunk/3.6.2/docs/_sources/CommandLine.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CommandLine.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CommandLine.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CommandLine.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,1743 @@
+==============================
+CommandLine 2.0 Library Manual
+==============================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+This document describes the CommandLine argument processing library. It will
+show you how to use it, and what it can do. The CommandLine library uses a
+declarative approach to specifying the command line options that your program
+takes. By default, these options declarations implicitly hold the value parsed
+for the option declared (of course this `can be changed`_).
+
+Although there are a **lot** of command line argument parsing libraries out
+there in many different languages, none of them fit well with what I needed. By
+looking at the features and problems of other libraries, I designed the
+CommandLine library to have the following features:
+
+#. Speed: The CommandLine library is very quick and uses little resources. The
+ parsing time of the library is directly proportional to the number of
+ arguments parsed, not the number of options recognized. Additionally,
+ command line argument values are captured transparently into user defined
+ global variables, which can be accessed like any other variable (and with the
+ same performance).
+
+#. Type Safe: As a user of CommandLine, you don't have to worry about
+ remembering the type of arguments that you want (is it an int? a string? a
+ bool? an enum?) and keep casting it around. Not only does this help prevent
+ error prone constructs, it also leads to dramatically cleaner source code.
+
+#. No subclasses required: To use CommandLine, you instantiate variables that
+ correspond to the arguments that you would like to capture, you don't
+ subclass a parser. This means that you don't have to write **any**
+ boilerplate code.
+
+#. Globally accessible: Libraries can specify command line arguments that are
+ automatically enabled in any tool that links to the library. This is
+ possible because the application doesn't have to keep a list of arguments to
+ pass to the parser. This also makes supporting `dynamically loaded options`_
+ trivial.
+
+#. Cleaner: CommandLine supports enum and other types directly, meaning that
+ there is less error and more security built into the library. You don't have
+ to worry about whether your integral command line argument accidentally got
+ assigned a value that is not valid for your enum type.
+
+#. Powerful: The CommandLine library supports many different types of arguments,
+ from simple `boolean flags`_ to `scalars arguments`_ (`strings`_,
+ `integers`_, `enums`_, `doubles`_), to `lists of arguments`_. This is
+ possible because CommandLine is...
+
+#. Extensible: It is very simple to add a new argument type to CommandLine.
+ Simply specify the parser that you want to use with the command line option
+ when you declare it. `Custom parsers`_ are no problem.
+
+#. Labor Saving: The CommandLine library cuts down on the amount of grunt work
+ that you, the user, have to do. For example, it automatically provides a
+ ``-help`` option that shows the available command line options for your tool.
+ Additionally, it does most of the basic correctness checking for you.
+
+#. Capable: The CommandLine library can handle lots of different forms of
+ options often found in real programs. For example, `positional`_ arguments,
+ ``ls`` style `grouping`_ options (to allow processing '``ls -lad``'
+ naturally), ``ld`` style `prefix`_ options (to parse '``-lmalloc
+ -L/usr/lib``'), and interpreter style options.
+
+This document will hopefully let you jump in and start using CommandLine in your
+utility quickly and painlessly. Additionally it should be a simple reference
+manual to figure out how stuff works.
+
+Quick Start Guide
+=================
+
+This section of the manual runs through a simple CommandLine'ification of a
+basic compiler tool. This is intended to show you how to jump into using the
+CommandLine library in your own program, and show you some of the cool things it
+can do.
+
+To start out, you need to include the CommandLine header file into your program:
+
+.. code-block:: c++
+
+ #include "llvm/Support/CommandLine.h"
+
+Additionally, you need to add this as the first line of your main program:
+
+.. code-block:: c++
+
+ int main(int argc, char **argv) {
+ cl::ParseCommandLineOptions(argc, argv);
+ ...
+ }
+
+... which actually parses the arguments and fills in the variable declarations.
+
+Now that you are ready to support command line arguments, we need to tell the
+system which ones we want, and what type of arguments they are. The CommandLine
+library uses a declarative syntax to model command line arguments with the
+global variable declarations that capture the parsed values. This means that
+for every command line option that you would like to support, there should be a
+global variable declaration to capture the result. For example, in a compiler,
+we would like to support the Unix-standard '``-o <filename>``' option to specify
+where to put the output. With the CommandLine library, this is represented like
+this:
+
+.. _scalars arguments:
+.. _here:
+
+.. code-block:: c++
+
+ cl::opt<string> OutputFilename("o", cl::desc("Specify output filename"), cl::value_desc("filename"));
+
+This declares a global variable "``OutputFilename``" that is used to capture the
+result of the "``o``" argument (first parameter). We specify that this is a
+simple scalar option by using the "``cl::opt``" template (as opposed to the
+"``cl::list``" template), and tell the CommandLine library that the data
+type that we are parsing is a string.
+
+The second and third parameters (which are optional) are used to specify what to
+output for the "``-help``" option. In this case, we get a line that looks like
+this:
+
+::
+
+ USAGE: compiler [options]
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+
+Because we specified that the command line option should parse using the
+``string`` data type, the variable declared is automatically usable as a real
+string in all contexts that a normal C++ string object may be used. For
+example:
+
+.. code-block:: c++
+
+ ...
+ std::ofstream Output(OutputFilename.c_str());
+ if (Output.good()) ...
+ ...
+
+There are many different options that you can use to customize the command line
+option handling library, but the above example shows the general interface to
+these options. The options can be specified in any order, and are specified
+with helper functions like `cl::desc(...)`_, so there are no positional
+dependencies to remember. The available options are discussed in detail in the
+`Reference Guide`_.
+
+Continuing the example, we would like to have our compiler take an input
+filename as well as an output filename, but we do not want the input filename to
+be specified with a hyphen (ie, not ``-filename.c``). To support this style of
+argument, the CommandLine library allows for `positional`_ arguments to be
+specified for the program. These positional arguments are filled with command
+line parameters that are not in option form. We use this feature like this:
+
+.. code-block:: c++
+
+
+ cl::opt<string> InputFilename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
+
+This declaration indicates that the first positional argument should be treated
+as the input filename. Here we use the `cl::init`_ option to specify an initial
+value for the command line option, which is used if the option is not specified
+(if you do not specify a `cl::init`_ modifier for an option, then the default
+constructor for the data type is used to initialize the value). Command line
+options default to being optional, so if we would like to require that the user
+always specify an input filename, we would add the `cl::Required`_ flag, and we
+could eliminate the `cl::init`_ modifier, like this:
+
+.. code-block:: c++
+
+ cl::opt<string> InputFilename(cl::Positional, cl::desc("<input file>"), cl::Required);
+
+Again, the CommandLine library does not require the options to be specified in
+any particular order, so the above declaration is equivalent to:
+
+.. code-block:: c++
+
+ cl::opt<string> InputFilename(cl::Positional, cl::Required, cl::desc("<input file>"));
+
+By simply adding the `cl::Required`_ flag, the CommandLine library will
+automatically issue an error if the argument is not specified, which shifts all
+of the command line option verification code out of your application into the
+library. This is just one example of how using flags can alter the default
+behaviour of the library, on a per-option basis. By adding one of the
+declarations above, the ``-help`` option synopsis is now extended to:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+
+... indicating that an input filename is expected.
+
+Boolean Arguments
+-----------------
+
+In addition to input and output filenames, we would like the compiler example to
+support three boolean flags: "``-f``" to force writing binary output to a
+terminal, "``--quiet``" to enable quiet mode, and "``-q``" for backwards
+compatibility with some of our users. We can support these by declaring options
+of boolean type like this:
+
+.. code-block:: c++
+
+ cl::opt<bool> Force ("f", cl::desc("Enable binary output on terminals"));
+ cl::opt<bool> Quiet ("quiet", cl::desc("Don't print informational messages"));
+ cl::opt<bool> Quiet2("q", cl::desc("Don't print informational messages"), cl::Hidden);
+
+This does what you would expect: it declares three boolean variables
+("``Force``", "``Quiet``", and "``Quiet2``") to recognize these options. Note
+that the "``-q``" option is specified with the "`cl::Hidden`_" flag. This
+modifier prevents it from being shown by the standard "``-help``" output (note
+that it is still shown in the "``-help-hidden``" output).
+
+The CommandLine library uses a `different parser`_ for different data types.
+For example, in the string case, the argument passed to the option is copied
+literally into the content of the string variable... we obviously cannot do that
+in the boolean case, however, so we must use a smarter parser. In the case of
+the boolean parser, it allows no options (in which case it assigns the value of
+true to the variable), or it allows the values "``true``" or "``false``" to be
+specified, allowing any of the following inputs:
+
+::
+
+ compiler -f # No value, 'Force' == true
+ compiler -f=true # Value specified, 'Force' == true
+ compiler -f=TRUE # Value specified, 'Force' == true
+ compiler -f=FALSE # Value specified, 'Force' == false
+
+... you get the idea. The `bool parser`_ just turns the string values into
+boolean values, and rejects things like '``compiler -f=foo``'. Similarly, the
+`float`_, `double`_, and `int`_ parsers work like you would expect, using the
+'``strtol``' and '``strtod``' C library calls to parse the string value into the
+specified data type.
+
+With the declarations above, "``compiler -help``" emits this:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ -f - Enable binary output on terminals
+ -o - Override output filename
+ -quiet - Don't print informational messages
+ -help - display available options (-help-hidden for more)
+
+and "``compiler -help-hidden``" prints this:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ -f - Enable binary output on terminals
+ -o - Override output filename
+ -q - Don't print informational messages
+ -quiet - Don't print informational messages
+ -help - display available options (-help-hidden for more)
+
+This brief example has shown you how to use the '`cl::opt`_' class to parse
+simple scalar command line arguments. In addition to simple scalar arguments,
+the CommandLine library also provides primitives to support CommandLine option
+`aliases`_, and `lists`_ of options.
+
+.. _aliases:
+
+Argument Aliases
+----------------
+
+So far, the example works well, except for the fact that we need to check the
+quiet condition like this now:
+
+.. code-block:: c++
+
+ ...
+ if (!Quiet && !Quiet2) printInformationalMessage(...);
+ ...
+
+... which is a real pain! Instead of defining two values for the same
+condition, we can use the "`cl::alias`_" class to make the "``-q``" option an
+**alias** for the "``-quiet``" option, instead of providing a value itself:
+
+.. code-block:: c++
+
+ cl::opt<bool> Force ("f", cl::desc("Overwrite output files"));
+ cl::opt<bool> Quiet ("quiet", cl::desc("Don't print informational messages"));
+ cl::alias QuietA("q", cl::desc("Alias for -quiet"), cl::aliasopt(Quiet));
+
+The third line (which is the only one we modified from above) defines a "``-q``"
+alias that updates the "``Quiet``" variable (as specified by the `cl::aliasopt`_
+modifier) whenever it is specified. Because aliases do not hold state, the only
+thing the program has to query is the ``Quiet`` variable now. Another nice
+feature of aliases is that they automatically hide themselves from the ``-help``
+output (although, again, they are still visible in the ``-help-hidden output``).
+
+Now the application code can simply use:
+
+.. code-block:: c++
+
+ ...
+ if (!Quiet) printInformationalMessage(...);
+ ...
+
+... which is much nicer! The "`cl::alias`_" can be used to specify an
+alternative name for any variable type, and has many uses.
+
+.. _unnamed alternatives using the generic parser:
+
+Selecting an alternative from a set of possibilities
+----------------------------------------------------
+
+So far we have seen how the CommandLine library handles builtin types like
+``std::string``, ``bool`` and ``int``, but how does it handle things it doesn't
+know about, like enums or '``int*``'s?
+
+The answer is that it uses a table-driven generic parser (unless you specify
+your own parser, as described in the `Extension Guide`_). This parser maps
+literal strings to whatever type is required, and requires you to tell it what
+this mapping should be.
+
+Let's say that we would like to add four optimization levels to our optimizer,
+using the standard flags "``-g``", "``-O0``", "``-O1``", and "``-O2``". We
+could easily implement this with boolean options like above, but there are
+several problems with this strategy:
+
+#. A user could specify more than one of the options at a time, for example,
+ "``compiler -O3 -O2``". The CommandLine library would not be able to catch
+ this erroneous input for us.
+
+#. We would have to test 4 different variables to see which ones are set.
+
+#. This doesn't map to the numeric levels that we want... so we cannot easily
+ see if some level >= "``-O1``" is enabled.
+
+To cope with these problems, we can use an enum value, and have the CommandLine
+library fill it in with the appropriate level directly, which is used like this:
+
+.. code-block:: c++
+
+ enum OptLevel {
+ g, O1, O2, O3
+ };
+
+ cl::opt<OptLevel> OptimizationLevel(cl::desc("Choose optimization level:"),
+ cl::values(
+ clEnumVal(g , "No optimizations, enable debugging"),
+ clEnumVal(O1, "Enable trivial optimizations"),
+ clEnumVal(O2, "Enable default optimizations"),
+ clEnumVal(O3, "Enable expensive optimizations"),
+ clEnumValEnd));
+
+ ...
+ if (OptimizationLevel >= O2) doPartialRedundancyElimination(...);
+ ...
+
+This declaration defines a variable "``OptimizationLevel``" of the
+"``OptLevel``" enum type. This variable can be assigned any of the values that
+are listed in the declaration (Note that the declaration list must be terminated
+with the "``clEnumValEnd``" argument!). The CommandLine library enforces that
+the user can only specify one of the options, and it ensure that only valid enum
+values can be specified. The "``clEnumVal``" macros ensure that the command
+line arguments matched the enum values. With this option added, our help output
+now is:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ Choose optimization level:
+ -g - No optimizations, enable debugging
+ -O1 - Enable trivial optimizations
+ -O2 - Enable default optimizations
+ -O3 - Enable expensive optimizations
+ -f - Enable binary output on terminals
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+ -quiet - Don't print informational messages
+
+In this case, it is sort of awkward that flag names correspond directly to enum
+names, because we probably don't want a enum definition named "``g``" in our
+program. Because of this, we can alternatively write this example like this:
+
+.. code-block:: c++
+
+ enum OptLevel {
+ Debug, O1, O2, O3
+ };
+
+ cl::opt<OptLevel> OptimizationLevel(cl::desc("Choose optimization level:"),
+ cl::values(
+ clEnumValN(Debug, "g", "No optimizations, enable debugging"),
+ clEnumVal(O1 , "Enable trivial optimizations"),
+ clEnumVal(O2 , "Enable default optimizations"),
+ clEnumVal(O3 , "Enable expensive optimizations"),
+ clEnumValEnd));
+
+ ...
+ if (OptimizationLevel == Debug) outputDebugInfo(...);
+ ...
+
+By using the "``clEnumValN``" macro instead of "``clEnumVal``", we can directly
+specify the name that the flag should get. In general a direct mapping is nice,
+but sometimes you can't or don't want to preserve the mapping, which is when you
+would use it.
+
+Named Alternatives
+------------------
+
+Another useful argument form is a named alternative style. We shall use this
+style in our compiler to specify different debug levels that can be used.
+Instead of each debug level being its own switch, we want to support the
+following options, of which only one can be specified at a time:
+"``--debug-level=none``", "``--debug-level=quick``",
+"``--debug-level=detailed``". To do this, we use the exact same format as our
+optimization level flags, but we also specify an option name. For this case,
+the code looks like this:
+
+.. code-block:: c++
+
+ enum DebugLev {
+ nodebuginfo, quick, detailed
+ };
+
+ // Enable Debug Options to be specified on the command line
+ cl::opt<DebugLev> DebugLevel("debug_level", cl::desc("Set the debugging level:"),
+ cl::values(
+ clEnumValN(nodebuginfo, "none", "disable debug information"),
+ clEnumVal(quick, "enable quick debug information"),
+ clEnumVal(detailed, "enable detailed debug information"),
+ clEnumValEnd));
+
+This definition defines an enumerated command line variable of type "``enum
+DebugLev``", which works exactly the same way as before. The difference here is
+just the interface exposed to the user of your program and the help output by
+the "``-help``" option:
+
+::
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ Choose optimization level:
+ -g - No optimizations, enable debugging
+ -O1 - Enable trivial optimizations
+ -O2 - Enable default optimizations
+ -O3 - Enable expensive optimizations
+ -debug_level - Set the debugging level:
+ =none - disable debug information
+ =quick - enable quick debug information
+ =detailed - enable detailed debug information
+ -f - Enable binary output on terminals
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+ -quiet - Don't print informational messages
+
+Again, the only structural difference between the debug level declaration and
+the optimization level declaration is that the debug level declaration includes
+an option name (``"debug_level"``), which automatically changes how the library
+processes the argument. The CommandLine library supports both forms so that you
+can choose the form most appropriate for your application.
+
+.. _lists:
+
+Parsing a list of options
+-------------------------
+
+Now that we have the standard run-of-the-mill argument types out of the way,
+lets get a little wild and crazy. Lets say that we want our optimizer to accept
+a **list** of optimizations to perform, allowing duplicates. For example, we
+might want to run: "``compiler -dce -constprop -inline -dce -strip``". In this
+case, the order of the arguments and the number of appearances is very
+important. This is what the "``cl::list``" template is for. First, start by
+defining an enum of the optimizations that you would like to perform:
+
+.. code-block:: c++
+
+ enum Opts {
+ // 'inline' is a C++ keyword, so name it 'inlining'
+ dce, constprop, inlining, strip
+ };
+
+Then define your "``cl::list``" variable:
+
+.. code-block:: c++
+
+ cl::list<Opts> OptimizationList(cl::desc("Available Optimizations:"),
+ cl::values(
+ clEnumVal(dce , "Dead Code Elimination"),
+ clEnumVal(constprop , "Constant Propagation"),
+ clEnumValN(inlining, "inline", "Procedure Integration"),
+ clEnumVal(strip , "Strip Symbols"),
+ clEnumValEnd));
+
+This defines a variable that is conceptually of the type
+"``std::vector<enum Opts>``". Thus, you can access it with standard vector
+methods:
+
+.. code-block:: c++
+
+ for (unsigned i = 0; i != OptimizationList.size(); ++i)
+ switch (OptimizationList[i])
+ ...
+
+... to iterate through the list of options specified.
+
+Note that the "``cl::list``" template is completely general and may be used with
+any data types or other arguments that you can use with the "``cl::opt``"
+template. One especially useful way to use a list is to capture all of the
+positional arguments together if there may be more than one specified. In the
+case of a linker, for example, the linker takes several '``.o``' files, and
+needs to capture them into a list. This is naturally specified as:
+
+.. code-block:: c++
+
+ ...
+ cl::list<std::string> InputFilenames(cl::Positional, cl::desc("<Input files>"), cl::OneOrMore);
+ ...
+
+This variable works just like a "``vector<string>``" object. As such, accessing
+the list is simple, just like above. In this example, we used the
+`cl::OneOrMore`_ modifier to inform the CommandLine library that it is an error
+if the user does not specify any ``.o`` files on our command line. Again, this
+just reduces the amount of checking we have to do.
+
+Collecting options as a set of flags
+------------------------------------
+
+Instead of collecting sets of options in a list, it is also possible to gather
+information for enum values in a **bit vector**. The representation used by the
+`cl::bits`_ class is an ``unsigned`` integer. An enum value is represented by a
+0/1 in the enum's ordinal value bit position. 1 indicating that the enum was
+specified, 0 otherwise. As each specified value is parsed, the resulting enum's
+bit is set in the option's bit vector:
+
+.. code-block:: c++
+
+ bits |= 1 << (unsigned)enum;
+
+Options that are specified multiple times are redundant. Any instances after
+the first are discarded.
+
+Reworking the above list example, we could replace `cl::list`_ with `cl::bits`_:
+
+.. code-block:: c++
+
+ cl::bits<Opts> OptimizationBits(cl::desc("Available Optimizations:"),
+ cl::values(
+ clEnumVal(dce , "Dead Code Elimination"),
+ clEnumVal(constprop , "Constant Propagation"),
+ clEnumValN(inlining, "inline", "Procedure Integration"),
+ clEnumVal(strip , "Strip Symbols"),
+ clEnumValEnd));
+
+To test to see if ``constprop`` was specified, we can use the ``cl:bits::isSet``
+function:
+
+.. code-block:: c++
+
+ if (OptimizationBits.isSet(constprop)) {
+ ...
+ }
+
+It's also possible to get the raw bit vector using the ``cl::bits::getBits``
+function:
+
+.. code-block:: c++
+
+ unsigned bits = OptimizationBits.getBits();
+
+Finally, if external storage is used, then the location specified must be of
+**type** ``unsigned``. In all other ways a `cl::bits`_ option is equivalent to a
+`cl::list`_ option.
+
+.. _additional extra text:
+
+Adding freeform text to help output
+-----------------------------------
+
+As our program grows and becomes more mature, we may decide to put summary
+information about what it does into the help output. The help output is styled
+to look similar to a Unix ``man`` page, providing concise information about a
+program. Unix ``man`` pages, however often have a description about what the
+program does. To add this to your CommandLine program, simply pass a third
+argument to the `cl::ParseCommandLineOptions`_ call in main. This additional
+argument is then printed as the overview information for your program, allowing
+you to include any additional information that you want. For example:
+
+.. code-block:: c++
+
+ int main(int argc, char **argv) {
+ cl::ParseCommandLineOptions(argc, argv, " CommandLine compiler example\n\n"
+ " This program blah blah blah...\n");
+ ...
+ }
+
+would yield the help output:
+
+::
+
+ **OVERVIEW: CommandLine compiler example
+
+ This program blah blah blah...**
+
+ USAGE: compiler [options] <input file>
+
+ OPTIONS:
+ ...
+ -help - display available options (-help-hidden for more)
+ -o <filename> - Specify output filename
+
+.. _grouping options into categories:
+
+Grouping options into categories
+--------------------------------
+
+If our program has a large number of options it may become difficult for users
+of our tool to navigate the output of ``-help``. To alleviate this problem we
+can put our options into categories. This can be done by declaring option
+categories (`cl::OptionCategory`_ objects) and then placing our options into
+these categories using the `cl::cat`_ option attribute. For example:
+
+.. code-block:: c++
+
+ cl::OptionCategory StageSelectionCat("Stage Selection Options",
+ "These control which stages are run.");
+
+ cl::opt<bool> Preprocessor("E",cl::desc("Run preprocessor stage."),
+ cl::cat(StageSelectionCat));
+
+ cl::opt<bool> NoLink("c",cl::desc("Run all stages except linking."),
+ cl::cat(StageSelectionCat));
+
+The output of ``-help`` will become categorized if an option category is
+declared. The output looks something like ::
+
+ OVERVIEW: This is a small program to demo the LLVM CommandLine API
+ USAGE: Sample [options]
+
+ OPTIONS:
+
+ General options:
+
+ -help - Display available options (-help-hidden for more)
+ -help-list - Display list of available options (-help-list-hidden for more)
+
+
+ Stage Selection Options:
+ These control which stages are run.
+
+ -E - Run preprocessor stage.
+ -c - Run all stages except linking.
+
+In addition to the behaviour of ``-help`` changing when an option category is
+declared, the command line option ``-help-list`` becomes visible which will
+print the command line options as uncategorized list.
+
+Note that Options that are not explicitly categorized will be placed in the
+``cl::GeneralCategory`` category.
+
+.. _Reference Guide:
+
+Reference Guide
+===============
+
+Now that you know the basics of how to use the CommandLine library, this section
+will give you the detailed information you need to tune how command line options
+work, as well as information on more "advanced" command line option processing
+capabilities.
+
+.. _positional:
+.. _positional argument:
+.. _Positional Arguments:
+.. _Positional arguments section:
+.. _positional options:
+
+Positional Arguments
+--------------------
+
+Positional arguments are those arguments that are not named, and are not
+specified with a hyphen. Positional arguments should be used when an option is
+specified by its position alone. For example, the standard Unix ``grep`` tool
+takes a regular expression argument, and an optional filename to search through
+(which defaults to standard input if a filename is not specified). Using the
+CommandLine library, this would be specified as:
+
+.. code-block:: c++
+
+ cl::opt<string> Regex (cl::Positional, cl::desc("<regular expression>"), cl::Required);
+ cl::opt<string> Filename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
+
+Given these two option declarations, the ``-help`` output for our grep
+replacement would look like this:
+
+::
+
+ USAGE: spiffygrep [options] <regular expression> <input file>
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+
+... and the resultant program could be used just like the standard ``grep``
+tool.
+
+Positional arguments are sorted by their order of construction. This means that
+command line options will be ordered according to how they are listed in a .cpp
+file, but will not have an ordering defined if the positional arguments are
+defined in multiple .cpp files. The fix for this problem is simply to define
+all of your positional arguments in one .cpp file.
+
+Specifying positional options with hyphens
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Sometimes you may want to specify a value to your positional argument that
+starts with a hyphen (for example, searching for '``-foo``' in a file). At
+first, you will have trouble doing this, because it will try to find an argument
+named '``-foo``', and will fail (and single quotes will not save you). Note
+that the system ``grep`` has the same problem:
+
+::
+
+ $ spiffygrep '-foo' test.txt
+ Unknown command line argument '-foo'. Try: spiffygrep -help'
+
+ $ grep '-foo' test.txt
+ grep: illegal option -- f
+ grep: illegal option -- o
+ grep: illegal option -- o
+ Usage: grep -hblcnsviw pattern file . . .
+
+The solution for this problem is the same for both your tool and the system
+version: use the '``--``' marker. When the user specifies '``--``' on the
+command line, it is telling the program that all options after the '``--``'
+should be treated as positional arguments, not options. Thus, we can use it
+like this:
+
+::
+
+ $ spiffygrep -- -foo test.txt
+ ...output...
+
+Determining absolute position with getPosition()
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Sometimes an option can affect or modify the meaning of another option. For
+example, consider ``gcc``'s ``-x LANG`` option. This tells ``gcc`` to ignore the
+suffix of subsequent positional arguments and force the file to be interpreted
+as if it contained source code in language ``LANG``. In order to handle this
+properly, you need to know the absolute position of each argument, especially
+those in lists, so their interaction(s) can be applied correctly. This is also
+useful for options like ``-llibname`` which is actually a positional argument
+that starts with a dash.
+
+So, generally, the problem is that you have two ``cl::list`` variables that
+interact in some way. To ensure the correct interaction, you can use the
+``cl::list::getPosition(optnum)`` method. This method returns the absolute
+position (as found on the command line) of the ``optnum`` item in the
+``cl::list``.
+
+The idiom for usage is like this:
+
+.. code-block:: c++
+
+ static cl::list<std::string> Files(cl::Positional, cl::OneOrMore);
+ static cl::list<std::string> Libraries("l", cl::ZeroOrMore);
+
+ int main(int argc, char**argv) {
+ // ...
+ std::vector<std::string>::iterator fileIt = Files.begin();
+ std::vector<std::string>::iterator libIt = Libraries.begin();
+ unsigned libPos = 0, filePos = 0;
+ while ( 1 ) {
+ if ( libIt != Libraries.end() )
+ libPos = Libraries.getPosition( libIt - Libraries.begin() );
+ else
+ libPos = 0;
+ if ( fileIt != Files.end() )
+ filePos = Files.getPosition( fileIt - Files.begin() );
+ else
+ filePos = 0;
+
+ if ( filePos != 0 && (libPos == 0 || filePos < libPos) ) {
+ // Source File Is next
+ ++fileIt;
+ }
+ else if ( libPos != 0 && (filePos == 0 || libPos < filePos) ) {
+ // Library is next
+ ++libIt;
+ }
+ else
+ break; // we're done with the list
+ }
+ }
+
+Note that, for compatibility reasons, the ``cl::opt`` also supports an
+``unsigned getPosition()`` option that will provide the absolute position of
+that option. You can apply the same approach as above with a ``cl::opt`` and a
+``cl::list`` option as you can with two lists.
+
+.. _interpreter style options:
+.. _cl::ConsumeAfter:
+.. _this section for more information:
+
+The ``cl::ConsumeAfter`` modifier
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::ConsumeAfter`` `formatting option`_ is used to construct programs that
+use "interpreter style" option processing. With this style of option
+processing, all arguments specified after the last positional argument are
+treated as special interpreter arguments that are not interpreted by the command
+line argument.
+
+As a concrete example, lets say we are developing a replacement for the standard
+Unix Bourne shell (``/bin/sh``). To run ``/bin/sh``, first you specify options
+to the shell itself (like ``-x`` which turns on trace output), then you specify
+the name of the script to run, then you specify arguments to the script. These
+arguments to the script are parsed by the Bourne shell command line option
+processor, but are not interpreted as options to the shell itself. Using the
+CommandLine library, we would specify this as:
+
+.. code-block:: c++
+
+ cl::opt<string> Script(cl::Positional, cl::desc("<input script>"), cl::init("-"));
+ cl::list<string> Argv(cl::ConsumeAfter, cl::desc("<program arguments>..."));
+ cl::opt<bool> Trace("x", cl::desc("Enable trace output"));
+
+which automatically provides the help output:
+
+::
+
+ USAGE: spiffysh [options] <input script> <program arguments>...
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+ -x - Enable trace output
+
+At runtime, if we run our new shell replacement as ```spiffysh -x test.sh -a -x
+-y bar``', the ``Trace`` variable will be set to true, the ``Script`` variable
+will be set to "``test.sh``", and the ``Argv`` list will contain ``["-a", "-x",
+"-y", "bar"]``, because they were specified after the last positional argument
+(which is the script name).
+
+There are several limitations to when ``cl::ConsumeAfter`` options can be
+specified. For example, only one ``cl::ConsumeAfter`` can be specified per
+program, there must be at least one `positional argument`_ specified, there must
+not be any `cl::list`_ positional arguments, and the ``cl::ConsumeAfter`` option
+should be a `cl::list`_ option.
+
+.. _can be changed:
+.. _Internal vs External Storage:
+
+Internal vs External Storage
+----------------------------
+
+By default, all command line options automatically hold the value that they
+parse from the command line. This is very convenient in the common case,
+especially when combined with the ability to define command line options in the
+files that use them. This is called the internal storage model.
+
+Sometimes, however, it is nice to separate the command line option processing
+code from the storage of the value parsed. For example, lets say that we have a
+'``-debug``' option that we would like to use to enable debug information across
+the entire body of our program. In this case, the boolean value controlling the
+debug code should be globally accessible (in a header file, for example) yet the
+command line option processing code should not be exposed to all of these
+clients (requiring lots of .cpp files to ``#include CommandLine.h``).
+
+To do this, set up your .h file with your option, like this for example:
+
+.. code-block:: c++
+
+ // DebugFlag.h - Get access to the '-debug' command line option
+ //
+
+ // DebugFlag - This boolean is set to true if the '-debug' command line option
+ // is specified. This should probably not be referenced directly, instead, use
+ // the DEBUG macro below.
+ //
+ extern bool DebugFlag;
+
+ // DEBUG macro - This macro should be used by code to emit debug information.
+ // In the '-debug' option is specified on the command line, and if this is a
+ // debug build, then the code specified as the option to the macro will be
+ // executed. Otherwise it will not be.
+ #ifdef NDEBUG
+ #define DEBUG(X)
+ #else
+ #define DEBUG(X) do { if (DebugFlag) { X; } } while (0)
+ #endif
+
+This allows clients to blissfully use the ``DEBUG()`` macro, or the
+``DebugFlag`` explicitly if they want to. Now we just need to be able to set
+the ``DebugFlag`` boolean when the option is set. To do this, we pass an
+additional argument to our command line argument processor, and we specify where
+to fill in with the `cl::location`_ attribute:
+
+.. code-block:: c++
+
+ bool DebugFlag; // the actual value
+ static cl::opt<bool, true> // The parser
+ Debug("debug", cl::desc("Enable debug output"), cl::Hidden, cl::location(DebugFlag));
+
+In the above example, we specify "``true``" as the second argument to the
+`cl::opt`_ template, indicating that the template should not maintain a copy of
+the value itself. In addition to this, we specify the `cl::location`_
+attribute, so that ``DebugFlag`` is automatically set.
+
+Option Attributes
+-----------------
+
+This section describes the basic attributes that you can specify on options.
+
+* The option name attribute (which is required for all options, except
+ `positional options`_) specifies what the option name is. This option is
+ specified in simple double quotes:
+
+ .. code-block:: c++
+
+ cl::opt<bool> Quiet("quiet");
+
+.. _cl::desc(...):
+
+* The **cl::desc** attribute specifies a description for the option to be
+ shown in the ``-help`` output for the program. This attribute supports
+ multi-line descriptions with lines separated by '\n'.
+
+.. _cl::value_desc:
+
+* The **cl::value_desc** attribute specifies a string that can be used to
+ fine tune the ``-help`` output for a command line option. Look `here`_ for an
+ example.
+
+.. _cl::init:
+
+* The **cl::init** attribute specifies an initial value for a `scalar`_
+ option. If this attribute is not specified then the command line option value
+ defaults to the value created by the default constructor for the
+ type.
+
+ .. warning::
+
+ If you specify both **cl::init** and **cl::location** for an option, you
+ must specify **cl::location** first, so that when the command-line parser
+ sees **cl::init**, it knows where to put the initial value. (You will get an
+ error at runtime if you don't put them in the right order.)
+
+.. _cl::location:
+
+* The **cl::location** attribute where to store the value for a parsed command
+ line option if using external storage. See the section on `Internal vs
+ External Storage`_ for more information.
+
+.. _cl::aliasopt:
+
+* The **cl::aliasopt** attribute specifies which option a `cl::alias`_ option is
+ an alias for.
+
+.. _cl::values:
+
+* The **cl::values** attribute specifies the string-to-value mapping to be used
+ by the generic parser. It takes a **clEnumValEnd terminated** list of
+ (option, value, description) triplets that specify the option name, the value
+ mapped to, and the description shown in the ``-help`` for the tool. Because
+ the generic parser is used most frequently with enum values, two macros are
+ often useful:
+
+ #. The **clEnumVal** macro is used as a nice simple way to specify a triplet
+ for an enum. This macro automatically makes the option name be the same as
+ the enum name. The first option to the macro is the enum, the second is
+ the description for the command line option.
+
+ #. The **clEnumValN** macro is used to specify macro options where the option
+ name doesn't equal the enum name. For this macro, the first argument is
+ the enum value, the second is the flag name, and the second is the
+ description.
+
+ You will get a compile time error if you try to use cl::values with a parser
+ that does not support it.
+
+.. _cl::multi_val:
+
+* The **cl::multi_val** attribute specifies that this option takes has multiple
+ values (example: ``-sectalign segname sectname sectvalue``). This attribute
+ takes one unsigned argument - the number of values for the option. This
+ attribute is valid only on ``cl::list`` options (and will fail with compile
+ error if you try to use it with other option types). It is allowed to use all
+ of the usual modifiers on multi-valued options (besides
+ ``cl::ValueDisallowed``, obviously).
+
+.. _cl::cat:
+
+* The **cl::cat** attribute specifies the option category that the option
+ belongs to. The category should be a `cl::OptionCategory`_ object.
+
+Option Modifiers
+----------------
+
+Option modifiers are the flags and expressions that you pass into the
+constructors for `cl::opt`_ and `cl::list`_. These modifiers give you the
+ability to tweak how options are parsed and how ``-help`` output is generated to
+fit your application well.
+
+These options fall into five main categories:
+
+#. Hiding an option from ``-help`` output
+
+#. Controlling the number of occurrences required and allowed
+
+#. Controlling whether or not a value must be specified
+
+#. Controlling other formatting options
+
+#. Miscellaneous option modifiers
+
+It is not possible to specify two options from the same category (you'll get a
+runtime error) to a single option, except for options in the miscellaneous
+category. The CommandLine library specifies defaults for all of these settings
+that are the most useful in practice and the most common, which mean that you
+usually shouldn't have to worry about these.
+
+Hiding an option from ``-help`` output
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::NotHidden``, ``cl::Hidden``, and ``cl::ReallyHidden`` modifiers are
+used to control whether or not an option appears in the ``-help`` and
+``-help-hidden`` output for the compiled program:
+
+.. _cl::NotHidden:
+
+* The **cl::NotHidden** modifier (which is the default for `cl::opt`_ and
+ `cl::list`_ options) indicates the option is to appear in both help
+ listings.
+
+.. _cl::Hidden:
+
+* The **cl::Hidden** modifier (which is the default for `cl::alias`_ options)
+ indicates that the option should not appear in the ``-help`` output, but
+ should appear in the ``-help-hidden`` output.
+
+.. _cl::ReallyHidden:
+
+* The **cl::ReallyHidden** modifier indicates that the option should not appear
+ in any help output.
+
+Controlling the number of occurrences required and allowed
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This group of options is used to control how many time an option is allowed (or
+required) to be specified on the command line of your program. Specifying a
+value for this setting allows the CommandLine library to do error checking for
+you.
+
+The allowed values for this option group are:
+
+.. _cl::Optional:
+
+* The **cl::Optional** modifier (which is the default for the `cl::opt`_ and
+ `cl::alias`_ classes) indicates that your program will allow either zero or
+ one occurrence of the option to be specified.
+
+.. _cl::ZeroOrMore:
+
+* The **cl::ZeroOrMore** modifier (which is the default for the `cl::list`_
+ class) indicates that your program will allow the option to be specified zero
+ or more times.
+
+.. _cl::Required:
+
+* The **cl::Required** modifier indicates that the specified option must be
+ specified exactly one time.
+
+.. _cl::OneOrMore:
+
+* The **cl::OneOrMore** modifier indicates that the option must be specified at
+ least one time.
+
+* The **cl::ConsumeAfter** modifier is described in the `Positional arguments
+ section`_.
+
+If an option is not specified, then the value of the option is equal to the
+value specified by the `cl::init`_ attribute. If the ``cl::init`` attribute is
+not specified, the option value is initialized with the default constructor for
+the data type.
+
+If an option is specified multiple times for an option of the `cl::opt`_ class,
+only the last value will be retained.
+
+Controlling whether or not a value must be specified
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This group of options is used to control whether or not the option allows a
+value to be present. In the case of the CommandLine library, a value is either
+specified with an equal sign (e.g. '``-index-depth=17``') or as a trailing
+string (e.g. '``-o a.out``').
+
+The allowed values for this option group are:
+
+.. _cl::ValueOptional:
+
+* The **cl::ValueOptional** modifier (which is the default for ``bool`` typed
+ options) specifies that it is acceptable to have a value, or not. A boolean
+ argument can be enabled just by appearing on the command line, or it can have
+ an explicit '``-foo=true``'. If an option is specified with this mode, it is
+ illegal for the value to be provided without the equal sign. Therefore
+ '``-foo true``' is illegal. To get this behavior, you must use
+ the `cl::ValueRequired`_ modifier.
+
+.. _cl::ValueRequired:
+
+* The **cl::ValueRequired** modifier (which is the default for all other types
+ except for `unnamed alternatives using the generic parser`_) specifies that a
+ value must be provided. This mode informs the command line library that if an
+ option is not provides with an equal sign, that the next argument provided
+ must be the value. This allows things like '``-o a.out``' to work.
+
+.. _cl::ValueDisallowed:
+
+* The **cl::ValueDisallowed** modifier (which is the default for `unnamed
+ alternatives using the generic parser`_) indicates that it is a runtime error
+ for the user to specify a value. This can be provided to disallow users from
+ providing options to boolean options (like '``-foo=true``').
+
+In general, the default values for this option group work just like you would
+want them to. As mentioned above, you can specify the `cl::ValueDisallowed`_
+modifier to a boolean argument to restrict your command line parser. These
+options are mostly useful when `extending the library`_.
+
+.. _formatting option:
+
+Controlling other formatting options
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The formatting option group is used to specify that the command line option has
+special abilities and is otherwise different from other command line arguments.
+As usual, you can only specify one of these arguments at most.
+
+.. _cl::NormalFormatting:
+
+* The **cl::NormalFormatting** modifier (which is the default all options)
+ specifies that this option is "normal".
+
+.. _cl::Positional:
+
+* The **cl::Positional** modifier specifies that this is a positional argument
+ that does not have a command line option associated with it. See the
+ `Positional Arguments`_ section for more information.
+
+* The **cl::ConsumeAfter** modifier specifies that this option is used to
+ capture "interpreter style" arguments. See `this section for more
+ information`_.
+
+.. _prefix:
+.. _cl::Prefix:
+
+* The **cl::Prefix** modifier specifies that this option prefixes its value.
+ With 'Prefix' options, the equal sign does not separate the value from the
+ option name specified. Instead, the value is everything after the prefix,
+ including any equal sign if present. This is useful for processing odd
+ arguments like ``-lmalloc`` and ``-L/usr/lib`` in a linker tool or
+ ``-DNAME=value`` in a compiler tool. Here, the '``l``', '``D``' and '``L``'
+ options are normal string (or list) options, that have the **cl::Prefix**
+ modifier added to allow the CommandLine library to recognize them. Note that
+ **cl::Prefix** options must not have the **cl::ValueDisallowed** modifier
+ specified.
+
+.. _grouping:
+.. _cl::Grouping:
+
+* The **cl::Grouping** modifier is used to implement Unix-style tools (like
+ ``ls``) that have lots of single letter arguments, but only require a single
+ dash. For example, the '``ls -labF``' command actually enables four different
+ options, all of which are single letters. Note that **cl::Grouping** options
+ cannot have values.
+
+The CommandLine library does not restrict how you use the **cl::Prefix** or
+**cl::Grouping** modifiers, but it is possible to specify ambiguous argument
+settings. Thus, it is possible to have multiple letter options that are prefix
+or grouping options, and they will still work as designed.
+
+To do this, the CommandLine library uses a greedy algorithm to parse the input
+option into (potentially multiple) prefix and grouping options. The strategy
+basically looks like this:
+
+::
+
+ parse(string OrigInput) {
+
+ 1. string input = OrigInput;
+ 2. if (isOption(input)) return getOption(input).parse(); // Normal option
+ 3. while (!isOption(input) && !input.empty()) input.pop_back(); // Remove the last letter
+ 4. if (input.empty()) return error(); // No matching option
+ 5. if (getOption(input).isPrefix())
+ return getOption(input).parse(input);
+ 6. while (!input.empty()) { // Must be grouping options
+ getOption(input).parse();
+ OrigInput.erase(OrigInput.begin(), OrigInput.begin()+input.length());
+ input = OrigInput;
+ while (!isOption(input) && !input.empty()) input.pop_back();
+ }
+ 7. if (!OrigInput.empty()) error();
+
+ }
+
+Miscellaneous option modifiers
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The miscellaneous option modifiers are the only flags where you can specify more
+than one flag from the set: they are not mutually exclusive. These flags
+specify boolean properties that modify the option.
+
+.. _cl::CommaSeparated:
+
+* The **cl::CommaSeparated** modifier indicates that any commas specified for an
+ option's value should be used to split the value up into multiple values for
+ the option. For example, these two options are equivalent when
+ ``cl::CommaSeparated`` is specified: "``-foo=a -foo=b -foo=c``" and
+ "``-foo=a,b,c``". This option only makes sense to be used in a case where the
+ option is allowed to accept one or more values (i.e. it is a `cl::list`_
+ option).
+
+.. _cl::PositionalEatsArgs:
+
+* The **cl::PositionalEatsArgs** modifier (which only applies to positional
+ arguments, and only makes sense for lists) indicates that positional argument
+ should consume any strings after it (including strings that start with a "-")
+ up until another recognized positional argument. For example, if you have two
+ "eating" positional arguments, "``pos1``" and "``pos2``", the string "``-pos1
+ -foo -bar baz -pos2 -bork``" would cause the "``-foo -bar -baz``" strings to
+ be applied to the "``-pos1``" option and the "``-bork``" string to be applied
+ to the "``-pos2``" option.
+
+.. _cl::Sink:
+
+* The **cl::Sink** modifier is used to handle unknown options. If there is at
+ least one option with ``cl::Sink`` modifier specified, the parser passes
+ unrecognized option strings to it as values instead of signaling an error. As
+ with ``cl::CommaSeparated``, this modifier only makes sense with a `cl::list`_
+ option.
+
+So far, these are the only three miscellaneous option modifiers.
+
+.. _response files:
+
+Response files
+^^^^^^^^^^^^^^
+
+Some systems, such as certain variants of Microsoft Windows and some older
+Unices have a relatively low limit on command-line length. It is therefore
+customary to use the so-called 'response files' to circumvent this
+restriction. These files are mentioned on the command-line (using the "@file")
+syntax. The program reads these files and inserts the contents into argv,
+thereby working around the command-line length limits. Response files are
+enabled by an optional fourth argument to `cl::ParseEnvironmentOptions`_ and
+`cl::ParseCommandLineOptions`_.
+
+Top-Level Classes and Functions
+-------------------------------
+
+Despite all of the built-in flexibility, the CommandLine option library really
+only consists of one function `cl::ParseCommandLineOptions`_) and three main
+classes: `cl::opt`_, `cl::list`_, and `cl::alias`_. This section describes
+these three classes in detail.
+
+.. _cl::getRegisteredOptions:
+
+The ``cl::getRegisteredOptions`` function
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::getRegisteredOptions`` function is designed to give a programmer
+access to declared non-positional command line options so that how they appear
+in ``-help`` can be modified prior to calling `cl::ParseCommandLineOptions`_.
+Note this method should not be called during any static initialisation because
+it cannot be guaranteed that all options will have been initialised. Hence it
+should be called from ``main``.
+
+This function can be used to gain access to options declared in libraries that
+the tool writter may not have direct access to.
+
+The function retrieves a :ref:`StringMap <dss_stringmap>` that maps the option
+string (e.g. ``-help``) to an ``Option*``.
+
+Here is an example of how the function could be used:
+
+.. code-block:: c++
+
+ using namespace llvm;
+ int main(int argc, char **argv) {
+ cl::OptionCategory AnotherCategory("Some options");
+
+ StringMap<cl::Option*> Map;
+ cl::getRegisteredOptions(Map);
+
+ //Unhide useful option and put it in a different category
+ assert(Map.count("print-all-options") > 0);
+ Map["print-all-options"]->setHiddenFlag(cl::NotHidden);
+ Map["print-all-options"]->setCategory(AnotherCategory);
+
+ //Hide an option we don't want to see
+ assert(Map.count("enable-no-infs-fp-math") > 0);
+ Map["enable-no-infs-fp-math"]->setHiddenFlag(cl::Hidden);
+
+ //Change --version to --show-version
+ assert(Map.count("version") > 0);
+ Map["version"]->setArgStr("show-version");
+
+ //Change --help description
+ assert(Map.count("help") > 0);
+ Map["help"]->setDescription("Shows help");
+
+ cl::ParseCommandLineOptions(argc, argv, "This is a small program to demo the LLVM CommandLine API");
+ ...
+ }
+
+
+.. _cl::ParseCommandLineOptions:
+
+The ``cl::ParseCommandLineOptions`` function
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::ParseCommandLineOptions`` function is designed to be called directly
+from ``main``, and is used to fill in the values of all of the command line
+option variables once ``argc`` and ``argv`` are available.
+
+The ``cl::ParseCommandLineOptions`` function requires two parameters (``argc``
+and ``argv``), but may also take an optional third parameter which holds
+`additional extra text`_ to emit when the ``-help`` option is invoked, and a
+fourth boolean parameter that enables `response files`_.
+
+.. _cl::ParseEnvironmentOptions:
+
+The ``cl::ParseEnvironmentOptions`` function
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::ParseEnvironmentOptions`` function has mostly the same effects as
+`cl::ParseCommandLineOptions`_, except that it is designed to take values for
+options from an environment variable, for those cases in which reading the
+command line is not convenient or desired. It fills in the values of all the
+command line option variables just like `cl::ParseCommandLineOptions`_ does.
+
+It takes four parameters: the name of the program (since ``argv`` may not be
+available, it can't just look in ``argv[0]``), the name of the environment
+variable to examine, the optional `additional extra text`_ to emit when the
+``-help`` option is invoked, and the boolean switch that controls whether
+`response files`_ should be read.
+
+``cl::ParseEnvironmentOptions`` will break the environment variable's value up
+into words and then process them using `cl::ParseCommandLineOptions`_.
+**Note:** Currently ``cl::ParseEnvironmentOptions`` does not support quoting, so
+an environment variable containing ``-option "foo bar"`` will be parsed as three
+words, ``-option``, ``"foo``, and ``bar"``, which is different from what you
+would get from the shell with the same input.
+
+The ``cl::SetVersionPrinter`` function
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::SetVersionPrinter`` function is designed to be called directly from
+``main`` and *before* ``cl::ParseCommandLineOptions``. Its use is optional. It
+simply arranges for a function to be called in response to the ``--version``
+option instead of having the ``CommandLine`` library print out the usual version
+string for LLVM. This is useful for programs that are not part of LLVM but wish
+to use the ``CommandLine`` facilities. Such programs should just define a small
+function that takes no arguments and returns ``void`` and that prints out
+whatever version information is appropriate for the program. Pass the address of
+that function to ``cl::SetVersionPrinter`` to arrange for it to be called when
+the ``--version`` option is given by the user.
+
+.. _cl::opt:
+.. _scalar:
+
+The ``cl::opt`` class
+^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::opt`` class is the class used to represent scalar command line
+options, and is the one used most of the time. It is a templated class which
+can take up to three arguments (all except for the first have default values
+though):
+
+.. code-block:: c++
+
+ namespace cl {
+ template <class DataType, bool ExternalStorage = false,
+ class ParserClass = parser<DataType> >
+ class opt;
+ }
+
+The first template argument specifies what underlying data type the command line
+argument is, and is used to select a default parser implementation. The second
+template argument is used to specify whether the option should contain the
+storage for the option (the default) or whether external storage should be used
+to contain the value parsed for the option (see `Internal vs External Storage`_
+for more information).
+
+The third template argument specifies which parser to use. The default value
+selects an instantiation of the ``parser`` class based on the underlying data
+type of the option. In general, this default works well for most applications,
+so this option is only used when using a `custom parser`_.
+
+.. _lists of arguments:
+.. _cl::list:
+
+The ``cl::list`` class
+^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::list`` class is the class used to represent a list of command line
+options. It too is a templated class which can take up to three arguments:
+
+.. code-block:: c++
+
+ namespace cl {
+ template <class DataType, class Storage = bool,
+ class ParserClass = parser<DataType> >
+ class list;
+ }
+
+This class works the exact same as the `cl::opt`_ class, except that the second
+argument is the **type** of the external storage, not a boolean value. For this
+class, the marker type '``bool``' is used to indicate that internal storage
+should be used.
+
+.. _cl::bits:
+
+The ``cl::bits`` class
+^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::bits`` class is the class used to represent a list of command line
+options in the form of a bit vector. It is also a templated class which can
+take up to three arguments:
+
+.. code-block:: c++
+
+ namespace cl {
+ template <class DataType, class Storage = bool,
+ class ParserClass = parser<DataType> >
+ class bits;
+ }
+
+This class works the exact same as the `cl::list`_ class, except that the second
+argument must be of **type** ``unsigned`` if external storage is used.
+
+.. _cl::alias:
+
+The ``cl::alias`` class
+^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::alias`` class is a nontemplated class that is used to form aliases for
+other arguments.
+
+.. code-block:: c++
+
+ namespace cl {
+ class alias;
+ }
+
+The `cl::aliasopt`_ attribute should be used to specify which option this is an
+alias for. Alias arguments default to being `cl::Hidden`_, and use the aliased
+options parser to do the conversion from string to data.
+
+.. _cl::extrahelp:
+
+The ``cl::extrahelp`` class
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::extrahelp`` class is a nontemplated class that allows extra help text
+to be printed out for the ``-help`` option.
+
+.. code-block:: c++
+
+ namespace cl {
+ struct extrahelp;
+ }
+
+To use the extrahelp, simply construct one with a ``const char*`` parameter to
+the constructor. The text passed to the constructor will be printed at the
+bottom of the help message, verbatim. Note that multiple ``cl::extrahelp``
+**can** be used, but this practice is discouraged. If your tool needs to print
+additional help information, put all that help into a single ``cl::extrahelp``
+instance.
+
+For example:
+
+.. code-block:: c++
+
+ cl::extrahelp("\nADDITIONAL HELP:\n\n This is the extra help\n");
+
+.. _cl::OptionCategory:
+
+The ``cl::OptionCategory`` class
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``cl::OptionCategory`` class is a simple class for declaring
+option categories.
+
+.. code-block:: c++
+
+ namespace cl {
+ class OptionCategory;
+ }
+
+An option category must have a name and optionally a description which are
+passed to the constructor as ``const char*``.
+
+Note that declaring an option category and associating it with an option before
+parsing options (e.g. statically) will change the output of ``-help`` from
+uncategorized to categorized. If an option category is declared but not
+associated with an option then it will be hidden from the output of ``-help``
+but will be shown in the output of ``-help-hidden``.
+
+.. _different parser:
+.. _discussed previously:
+
+Builtin parsers
+---------------
+
+Parsers control how the string value taken from the command line is translated
+into a typed value, suitable for use in a C++ program. By default, the
+CommandLine library uses an instance of ``parser<type>`` if the command line
+option specifies that it uses values of type '``type``'. Because of this,
+custom option processing is specified with specializations of the '``parser``'
+class.
+
+The CommandLine library provides the following builtin parser specializations,
+which are sufficient for most applications. It can, however, also be extended to
+work with new data types and new ways of interpreting the same data. See the
+`Writing a Custom Parser`_ for more details on this type of library extension.
+
+.. _enums:
+.. _cl::parser:
+
+* The generic ``parser<t>`` parser can be used to map strings values to any data
+ type, through the use of the `cl::values`_ property, which specifies the
+ mapping information. The most common use of this parser is for parsing enum
+ values, which allows you to use the CommandLine library for all of the error
+ checking to make sure that only valid enum values are specified (as opposed to
+ accepting arbitrary strings). Despite this, however, the generic parser class
+ can be used for any data type.
+
+.. _boolean flags:
+.. _bool parser:
+
+* The **parser<bool> specialization** is used to convert boolean strings to a
+ boolean value. Currently accepted strings are "``true``", "``TRUE``",
+ "``True``", "``1``", "``false``", "``FALSE``", "``False``", and "``0``".
+
+* The **parser<boolOrDefault> specialization** is used for cases where the value
+ is boolean, but we also need to know whether the option was specified at all.
+ boolOrDefault is an enum with 3 values, BOU_UNSET, BOU_TRUE and BOU_FALSE.
+ This parser accepts the same strings as **``parser<bool>``**.
+
+.. _strings:
+
+* The **parser<string> specialization** simply stores the parsed string into the
+ string value specified. No conversion or modification of the data is
+ performed.
+
+.. _integers:
+.. _int:
+
+* The **parser<int> specialization** uses the C ``strtol`` function to parse the
+ string input. As such, it will accept a decimal number (with an optional '+'
+ or '-' prefix) which must start with a non-zero digit. It accepts octal
+ numbers, which are identified with a '``0``' prefix digit, and hexadecimal
+ numbers with a prefix of '``0x``' or '``0X``'.
+
+.. _doubles:
+.. _float:
+.. _double:
+
+* The **parser<double>** and **parser<float> specializations** use the standard
+ C ``strtod`` function to convert floating point strings into floating point
+ values. As such, a broad range of string formats is supported, including
+ exponential notation (ex: ``1.7e15``) and properly supports locales.
+
+.. _Extension Guide:
+.. _extending the library:
+
+Extension Guide
+===============
+
+Although the CommandLine library has a lot of functionality built into it
+already (as discussed previously), one of its true strengths lie in its
+extensibility. This section discusses how the CommandLine library works under
+the covers and illustrates how to do some simple, common, extensions.
+
+.. _Custom parsers:
+.. _custom parser:
+.. _Writing a Custom Parser:
+
+Writing a custom parser
+-----------------------
+
+One of the simplest and most common extensions is the use of a custom parser.
+As `discussed previously`_, parsers are the portion of the CommandLine library
+that turns string input from the user into a particular parsed data type,
+validating the input in the process.
+
+There are two ways to use a new parser:
+
+#. Specialize the `cl::parser`_ template for your custom data type.
+
+ This approach has the advantage that users of your custom data type will
+ automatically use your custom parser whenever they define an option with a
+ value type of your data type. The disadvantage of this approach is that it
+ doesn't work if your fundamental data type is something that is already
+ supported.
+
+#. Write an independent class, using it explicitly from options that need it.
+
+ This approach works well in situations where you would line to parse an
+ option using special syntax for a not-very-special data-type. The drawback
+ of this approach is that users of your parser have to be aware that they are
+ using your parser instead of the builtin ones.
+
+To guide the discussion, we will discuss a custom parser that accepts file
+sizes, specified with an optional unit after the numeric size. For example, we
+would like to parse "102kb", "41M", "1G" into the appropriate integer value. In
+this case, the underlying data type we want to parse into is '``unsigned``'. We
+choose approach #2 above because we don't want to make this the default for all
+``unsigned`` options.
+
+To start out, we declare our new ``FileSizeParser`` class:
+
+.. code-block:: c++
+
+ struct FileSizeParser : public cl::parser<unsigned> {
+ // parse - Return true on error.
+ bool parse(cl::Option &O, StringRef ArgName, const std::string &ArgValue,
+ unsigned &Val);
+ };
+
+Our new class inherits from the ``cl::parser`` template class to fill in
+the default, boiler plate code for us. We give it the data type that we parse
+into, the last argument to the ``parse`` method, so that clients of our custom
+parser know what object type to pass in to the parse method. (Here we declare
+that we parse into '``unsigned``' variables.)
+
+For most purposes, the only method that must be implemented in a custom parser
+is the ``parse`` method. The ``parse`` method is called whenever the option is
+invoked, passing in the option itself, the option name, the string to parse, and
+a reference to a return value. If the string to parse is not well-formed, the
+parser should output an error message and return true. Otherwise it should
+return false and set '``Val``' to the parsed value. In our example, we
+implement ``parse`` as:
+
+.. code-block:: c++
+
+ bool FileSizeParser::parse(cl::Option &O, StringRef ArgName,
+ const std::string &Arg, unsigned &Val) {
+ const char *ArgStart = Arg.c_str();
+ char *End;
+
+ // Parse integer part, leaving 'End' pointing to the first non-integer char
+ Val = (unsigned)strtol(ArgStart, &End, 0);
+
+ while (1) {
+ switch (*End++) {
+ case 0: return false; // No error
+ case 'i': // Ignore the 'i' in KiB if people use that
+ case 'b': case 'B': // Ignore B suffix
+ break;
+
+ case 'g': case 'G': Val *= 1024*1024*1024; break;
+ case 'm': case 'M': Val *= 1024*1024; break;
+ case 'k': case 'K': Val *= 1024; break;
+
+ default:
+ // Print an error message if unrecognized character!
+ return O.error("'" + Arg + "' value invalid for file size argument!");
+ }
+ }
+ }
+
+This function implements a very simple parser for the kinds of strings we are
+interested in. Although it has some holes (it allows "``123KKK``" for example),
+it is good enough for this example. Note that we use the option itself to print
+out the error message (the ``error`` method always returns true) in order to get
+a nice error message (shown below). Now that we have our parser class, we can
+use it like this:
+
+.. code-block:: c++
+
+ static cl::opt<unsigned, false, FileSizeParser>
+ MFS("max-file-size", cl::desc("Maximum file size to accept"),
+ cl::value_desc("size"));
+
+Which adds this to the output of our program:
+
+::
+
+ OPTIONS:
+ -help - display available options (-help-hidden for more)
+ ...
+ -max-file-size=<size> - Maximum file size to accept
+
+And we can test that our parse works correctly now (the test program just prints
+out the max-file-size argument value):
+
+::
+
+ $ ./test
+ MFS: 0
+ $ ./test -max-file-size=123MB
+ MFS: 128974848
+ $ ./test -max-file-size=3G
+ MFS: 3221225472
+ $ ./test -max-file-size=dog
+ -max-file-size option: 'dog' value invalid for file size argument!
+
+It looks like it works. The error message that we get is nice and helpful, and
+we seem to accept reasonable file sizes. This wraps up the "custom parser"
+tutorial.
+
+Exploiting external storage
+---------------------------
+
+Several of the LLVM libraries define static ``cl::opt`` instances that will
+automatically be included in any program that links with that library. This is
+a feature. However, sometimes it is necessary to know the value of the command
+line option outside of the library. In these cases the library does or should
+provide an external storage location that is accessible to users of the
+library. Examples of this include the ``llvm::DebugFlag`` exported by the
+``lib/Support/Debug.cpp`` file and the ``llvm::TimePassesIsEnabled`` flag
+exported by the ``lib/VMCore/PassManager.cpp`` file.
+
+.. todo::
+
+ TODO: complete this section
+
+.. _dynamically loaded options:
+
+Dynamically adding command line options
+
+.. todo::
+
+ TODO: fill in this section
Added: www-releases/trunk/3.6.2/docs/_sources/CompilerWriterInfo.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CompilerWriterInfo.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CompilerWriterInfo.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CompilerWriterInfo.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,163 @@
+========================================================
+Architecture & Platform Information for Compiler Writers
+========================================================
+
+.. contents::
+ :local:
+
+.. note::
+
+ This document is a work-in-progress. Additions and clarifications are
+ welcome.
+
+Hardware
+========
+
+ARM
+---
+
+* `ARM documentation <http://www.arm.com/documentation/>`_ (`Processor Cores <http://www.arm.com/documentation/ARMProcessor_Cores/>`_ Cores)
+
+* `ABI <http://www.arm.com/products/DevTools/ABI.html>`_
+
+* `ABI Addenda and Errata <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0045d/IHI0045D_ABI_addenda.pdf>`_
+
+* `ARM C Language Extensions <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053a/IHI0053A_acle.pdf>`_
+
+AArch64
+-------
+
+* `ARMv8 Instruction Set Overview <http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.genc010197a/index.html>`_
+
+* `ARM C Language Extensions <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053a/IHI0053A_acle.pdf>`_
+
+Itanium (ia64)
+--------------
+
+* `Itanium documentation <http://developer.intel.com/design/itanium2/documentation.htm>`_
+
+MIPS
+----
+
+* `MIPS Processor Architecture <http://imgtec.com/mips/mips-architectures.asp>`_
+
+PowerPC
+-------
+
+IBM - Official manuals and docs
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* `Power Instruction Set Architecture, Versions 2.03 through 2.06 (authentication required, free sign-up) <https://www.power.org/technology-introduction/standards-specifications>`_
+
+* `PowerPC Compiler Writer's Guide <http://www.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF7785256996007558C6>`_
+
+* `Intro to PowerPC Architecture <http://www.ibm.com/developerworks/linux/library/l-powarch/>`_
+
+* `PowerPC Processor Manuals (embedded) <http://www.ibm.com/chips/techlib/techlib.nsf/products/PowerPC>`_
+
+* `Various IBM specifications and white papers <https://www.power.org/documentation/?document_company=105&document_category=all&publish_year=all&grid_order=DESC&grid_sort=title>`_
+
+* `IBM AIX/5L for POWER Assembly Reference <http://publibn.boulder.ibm.com/doc_link/en_US/a_doc_lib/aixassem/alangref/alangreftfrm.htm>`_
+
+Other documents, collections, notes
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* `PowerPC ABI documents <http://penguinppc.org/dev/#library>`_
+* `PowerPC64 alignment of long doubles (from GCC) <http://gcc.gnu.org/ml/gcc-patches/2003-09/msg00997.html>`_
+* `Long branch stubs for powerpc64-linux (from binutils) <http://sources.redhat.com/ml/binutils/2002-04/msg00573.html>`_
+
+R600
+----
+
+* `AMD R6xx shader ISA <http://developer.amd.com/wordpress/media/2012/10/R600_Instruction_Set_Architecture.pdf>`_
+* `AMD R7xx shader ISA <http://developer.amd.com/wordpress/media/2012/10/R700-Family_Instruction_Set_Architecture.pdf>`_
+* `AMD Evergreen shader ISA <http://developer.amd.com/wordpress/media/2012/10/AMD_Evergreen-Family_Instruction_Set_Architecture.pdf>`_
+* `AMD Cayman/Trinity shader ISA <http://developer.amd.com/wordpress/media/2012/10/AMD_HD_6900_Series_Instruction_Set_Architecture.pdf>`_
+* `AMD Southern Islands Series ISA <http://developer.amd.com/wordpress/media/2012/12/AMD_Southern_Islands_Instruction_Set_Architecture.pdf>`_
+* `AMD Sea Islands Series ISA <http://developer.amd.com/wordpress/media/2013/07/AMD_Sea_Islands_Instruction_Set_Architecture.pdf>`_
+* `AMD GPU Programming Guide <http://developer.amd.com/download/AMD_Accelerated_Parallel_Processing_OpenCL_Programming_Guide.pdf>`_
+* `AMD Compute Resources <http://developer.amd.com/tools/heterogeneous-computing/amd-accelerated-parallel-processing-app-sdk/documentation/>`_
+
+SPARC
+-----
+
+* `SPARC standards <http://sparc.org/standards>`_
+* `SPARC V9 ABI <http://sparc.org/standards/64.psabi.1.35.ps.Z>`_
+* `SPARC V8 ABI <http://sparc.org/standards/psABI3rd.pdf>`_
+
+SystemZ
+-------
+
+* `z/Architecture Principles of Operation (registration required, free sign-up) <http://www-01.ibm.com/support/docview.wss?uid=isg2b9de5f05a9d57819852571c500428f9a>`_
+
+X86
+---
+
+AMD - Official manuals and docs
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* `AMD processor manuals <http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_739,00.html>`_
+* `X86-64 ABI <http://www.x86-64.org/documentation>`_
+
+Intel - Official manuals and docs
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* `Intel 64 and IA-32 manuals <http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html>`_
+* `Intel Itanium documentation <http://www.intel.com/design/itanium/documentation.htm?iid=ipp_srvr_proc_itanium2+techdocs>`_
+
+Other x86-specific information
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* `Calling conventions for different C++ compilers and operating systems <http://www.agner.org/optimize/calling_conventions.pdf>`_
+
+XCore
+-----
+
+* `The XMOS XS1 Architecture (ISA) <https://www.xmos.com/en/download/public/The-XMOS-XS1-Architecture%28X7879A%29.pdf>`_
+* `Tools Development Guide (includes ABI) <https://www.xmos.com/download/public/Tools-Development-Guide%28X9114A%29.pdf>`_
+
+Other relevant lists
+--------------------
+
+* `GCC reading list <http://gcc.gnu.org/readings.html>`_
+
+ABI
+===
+
+* `System V Application Binary Interface <http://www.sco.com/developers/gabi/latest/contents.html>`_
+* `Itanium C++ ABI <http://mentorembedded.github.io/cxx-abi/>`_
+
+Linux
+-----
+
+* `PowerPC 64-bit ELF ABI Supplement <http://www.linuxbase.org/spec/ELF/ppc64/>`_
+* `Procedure Call Standard for the AArch64 Architecture <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055a/IHI0055A_aapcs64.pdf>`_
+* `ELF for the ARM Architecture <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044e/IHI0044E_aaelf.pdf>`_
+* `ELF for the ARM 64-bit Architecture (AArch64) <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0056a/IHI0056A_aaelf64.pdf>`_
+* `System z ELF ABI Supplement <http://legacy.redhat.com/pub/redhat/linux/7.1/es/os/s390x/doc/lzsabi0.pdf>`_
+
+OS X
+----
+
+* `Mach-O Runtime Architecture <http://developer.apple.com/documentation/Darwin/RuntimeArchitecture-date.html>`_
+* `Notes on Mach-O ABI <http://www.unsanity.org/archives/000044.php>`_
+
+Windows
+-------
+
+* `Microsoft PE/COFF Specification <http://www.microsoft.com/whdc/system/platform/firmware/pecoff.mspx>`_
+
+NVPTX
+=====
+
+* `CUDA Documentation <http://docs.nvidia.com/cuda/index.html>`_ includes the PTX
+ ISA and Driver API documentation
+
+Miscellaneous Resources
+=======================
+
+* `Executable File Format library <http://www.nondot.org/sabre/os/articles/ExecutableFileFormats/>`_
+
+* `GCC prefetch project <http://gcc.gnu.org/projects/prefetch.html>`_ page has a
+ good survey of the prefetching capabilities of a variety of modern
+ processors.
Added: www-releases/trunk/3.6.2/docs/_sources/CoverageMappingFormat.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/CoverageMappingFormat.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/CoverageMappingFormat.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/CoverageMappingFormat.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,576 @@
+.. role:: raw-html(raw)
+ :format: html
+
+=================================
+LLVM Code Coverage Mapping Format
+=================================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+LLVM's code coverage mapping format is used to provide code coverage
+analysis using LLVM's and Clang's instrumenation based profiling
+(Clang's ``-fprofile-instr-generate`` option).
+
+This document is aimed at those who use LLVM's code coverage mapping to provide
+code coverage analysis for their own programs, and for those who would like
+to know how it works under the hood. A prior knowledge of how Clang's profile
+guided optimization works is useful, but not required.
+
+We start by showing how to use LLVM and Clang for code coverage analysis,
+then we briefly desribe LLVM's code coverage mapping format and the
+way that Clang and LLVM's code coverage tool work with this format. After
+the basics are down, more advanced features of the coverage mapping format
+are discussed - such as the data structures, LLVM IR representation and
+the binary encoding.
+
+Quick Start
+===========
+
+Here's a short story that describes how to generate code coverage overview
+for a sample source file called *test.c*.
+
+* First, compile an instrumented version of your program using Clang's
+ ``-fprofile-instr-generate`` option with the additional ``-fcoverage-mapping``
+ option:
+
+ ``clang -o test -fprofile-instr-generate -fcoverage-mapping test.c``
+* Then, run the instrumented binary. The runtime will produce a file called
+ *default.profraw* containing the raw profile instrumentation data:
+
+ ``./test``
+* After that, merge the profile data using the *llvm-profdata* tool:
+
+ ``llvm-profdata merge -o test.profdata default.profraw``
+* Finally, run LLVM's code coverage tool (*llvm-cov*) to produce the code
+ coverage overview for the sample source file:
+
+ ``llvm-cov show ./test -instr-profile=test.profdata test.c``
+
+High Level Overview
+===================
+
+LLVM's code coverage mapping format is designed to be a self contained
+data format, that can be embedded into the LLVM IR and object files.
+It's described in this document as a **mapping** format because its goal is
+to store the data that is required for a code coverage tool to map between
+the specific source ranges in a file and the execution counts obtained
+after running the instrumented version of the program.
+
+The mapping data is used in two places in the code coverage process:
+
+1. When clang compiles a source file with ``-fcoverage-mapping``, it
+ generates the mapping information that describes the mapping between the
+ source ranges and the profiling instrumentation counters.
+ This information gets embedded into the LLVM IR and conveniently
+ ends up in the final executable file when the program is linked.
+
+2. It is also used by *llvm-cov* - the mapping information is extracted from an
+ object file and is used to associate the execution counts (the values of the
+ profile instrumentation counters), and the source ranges in a file.
+ After that, the tool is able to generate various code coverage reports
+ for the program.
+
+The coverage mapping format aims to be a "universal format" that would be
+suitable for usage by any frontend, and not just by Clang. It also aims to
+provide the frontend the possibility of generating the minimal coverage mapping
+data in order to reduce the size of the IR and object files - for example,
+instead of emitting mapping information for each statement in a function, the
+frontend is allowed to group the statements with the same execution count into
+regions of code, and emit the mapping information only for those regions.
+
+Advanced Concepts
+=================
+
+The remainder of this guide is meant to give you insight into the way the
+coverage mapping format works.
+
+The coverage mapping format operates on a per-function level as the
+profile instrumentation counters are associated with a specific function.
+For each function that requires code coverage, the frontend has to create
+coverage mapping data that can map between the source code ranges and
+the profile instrumentation counters for that function.
+
+Mapping Region
+--------------
+
+The function's coverage mapping data contains an array of mapping regions.
+A mapping region stores the `source code range`_ that is covered by this region,
+the `file id <coverage file id_>`_, the `coverage mapping counter`_ and
+the region's kind.
+There are several kinds of mapping regions:
+
+* Code regions associate portions of source code and `coverage mapping
+ counters`_. They make up the majority of the mapping regions. They are used
+ by the code coverage tool to compute the execution counts for lines,
+ highlight the regions of code that were never executed, and to obtain
+ the various code coverage statistics for a function.
+ For example:
+
+ :raw-html:`<pre class='highlight' style='line-height:initial;'><span>int main(int argc, const char *argv[]) </span><span style='background-color:#4A789C'>{ </span> <span class='c1'>// Code Region from 1:40 to 9:2</span>
+ <span style='background-color:#4A789C'> </span>
+ <span style='background-color:#4A789C'> if (argc > 1) </span><span style='background-color:#85C1F5'>{ </span> <span class='c1'>// Code Region from 3:17 to 5:4</span>
+ <span style='background-color:#85C1F5'> printf("%s\n", argv[1]); </span>
+ <span style='background-color:#85C1F5'> }</span><span style='background-color:#4A789C'> else </span><span style='background-color:#F6D55D'>{ </span> <span class='c1'>// Code Region from 5:10 to 7:4</span>
+ <span style='background-color:#F6D55D'> printf("\n"); </span>
+ <span style='background-color:#F6D55D'> }</span><span style='background-color:#4A789C'> </span>
+ <span style='background-color:#4A789C'> return 0; </span>
+ <span style='background-color:#4A789C'>}</span>
+ </pre>`
+* Skipped regions are used to represent source ranges that were skipped
+ by Clang's preprocessor. They don't associate with
+ `coverage mapping counters`_, as the frontend knows that they are never
+ executed. They are used by the code coverage tool to mark the skipped lines
+ inside a function as non-code lines that don't have execution counts.
+ For example:
+
+ :raw-html:`<pre class='highlight' style='line-height:initial;'><span>int main() </span><span style='background-color:#4A789C'>{ </span> <span class='c1'>// Code Region from 1:12 to 6:2</span>
+ <span style='background-color:#85C1F5'>#ifdef DEBUG </span> <span class='c1'>// Skipped Region from 2:1 to 4:2</span>
+ <span style='background-color:#85C1F5'> printf("Hello world"); </span>
+ <span style='background-color:#85C1F5'>#</span><span style='background-color:#4A789C'>endif </span>
+ <span style='background-color:#4A789C'> return 0; </span>
+ <span style='background-color:#4A789C'>}</span>
+ </pre>`
+* Expansion regions are used to represent Clang's macro expansions. They
+ have an additional property - *expanded file id*. This property can be
+ used by the code coverage tool to find the mapping regions that are created
+ as a result of this macro expansion, by checking if their file id matches the
+ expanded file id. They don't associate with `coverage mapping counters`_,
+ as the code coverage tool can determine the execution count for this region
+ by looking up the execution count of the first region with a corresponding
+ file id.
+ For example:
+
+ :raw-html:`<pre class='highlight' style='line-height:initial;'><span>int func(int x) </span><span style='background-color:#4A789C'>{ </span>
+ <span style='background-color:#4A789C'> #define MAX(x,y) </span><span style='background-color:#85C1F5'>((x) > (y)? </span><span style='background-color:#F6D55D'>(x)</span><span style='background-color:#85C1F5'> : </span><span style='background-color:#F4BA70'>(y)</span><span style='background-color:#85C1F5'>)</span><span style='background-color:#4A789C'> </span>
+ <span style='background-color:#4A789C'> return </span><span style='background-color:#7FCA9F'>MAX</span><span style='background-color:#4A789C'>(x, 42); </span> <span class='c1'>// Expansion Region from 3:10 to 3:13</span>
+ <span style='background-color:#4A789C'>}</span>
+ </pre>`
+
+.. _source code range:
+
+Source Range:
+^^^^^^^^^^^^^
+
+The source range record contains the starting and ending location of a certain
+mapping region. Both locations include the line and the column numbers.
+
+.. _coverage file id:
+
+File ID:
+^^^^^^^^
+
+The file id an integer value that tells us
+in which source file or macro expansion is this region located.
+It enables Clang to produce mapping information for the code
+defined inside macros, like this example demonstrates:
+
+:raw-html:`<pre class='highlight' style='line-height:initial;'><span>void func(const char *str) </span><span style='background-color:#4A789C'>{ </span> <span class='c1'>// Code Region from 1:28 to 6:2 with file id 0</span>
+<span style='background-color:#4A789C'> #define PUT </span><span style='background-color:#85C1F5'>printf("%s\n", str)</span><span style='background-color:#4A789C'> </span> <span class='c1'>// 2 Code Regions from 2:15 to 2:34 with file ids 1 and 2</span>
+<span style='background-color:#4A789C'> if(*str) </span>
+<span style='background-color:#4A789C'> </span><span style='background-color:#F6D55D'>PUT</span><span style='background-color:#4A789C'>; </span> <span class='c1'>// Expansion Region from 4:5 to 4:8 with file id 0 that expands a macro with file id 1</span>
+<span style='background-color:#4A789C'> </span><span style='background-color:#F6D55D'>PUT</span><span style='background-color:#4A789C'>; </span> <span class='c1'>// Expansion Region from 5:3 to 5:6 with file id 0 that expands a macro with file id 2</span>
+<span style='background-color:#4A789C'>}</span>
+</pre>`
+
+.. _coverage mapping counter:
+.. _coverage mapping counters:
+
+Counter:
+^^^^^^^^
+
+A coverage mapping counter can represents a reference to the profile
+instrumentation counter. The execution count for a region with such counter
+is determined by looking up the value of the corresponding profile
+instrumentation counter.
+
+It can also represent a binary arithmetical expression that operates on
+coverage mapping counters or other expressions.
+The execution count for a region with an expression counter is determined by
+evaluating the expression's arguments and then adding them together or
+subtracting them from one another.
+In the example below, a subtraction expression is used to compute the execution
+count for the compound statement that follows the *else* keyword:
+
+:raw-html:`<pre class='highlight' style='line-height:initial;'><span>int main(int argc, const char *argv[]) </span><span style='background-color:#4A789C'>{ </span> <span class='c1'>// Region's counter is a reference to the profile counter #0</span>
+<span style='background-color:#4A789C'> </span>
+<span style='background-color:#4A789C'> if (argc > 1) </span><span style='background-color:#85C1F5'>{ </span> <span class='c1'>// Region's counter is a reference to the profile counter #1</span>
+<span style='background-color:#85C1F5'> printf("%s\n", argv[1]); </span><span> </span>
+<span style='background-color:#85C1F5'> }</span><span style='background-color:#4A789C'> else </span><span style='background-color:#F6D55D'>{ </span> <span class='c1'>// Region's counter is an expression (reference to the profile counter #0 - reference to the profile counter #1)</span>
+<span style='background-color:#F6D55D'> printf("\n"); </span>
+<span style='background-color:#F6D55D'> }</span><span style='background-color:#4A789C'> </span>
+<span style='background-color:#4A789C'> return 0; </span>
+<span style='background-color:#4A789C'>}</span>
+</pre>`
+
+Finally, a coverage mapping counter can also represent an execution count of
+of zero. The zero counter is used to provide coverage mapping for
+unreachable statements and expressions, like in the example below:
+
+:raw-html:`<pre class='highlight' style='line-height:initial;'><span>int main() </span><span style='background-color:#4A789C'>{ </span>
+<span style='background-color:#4A789C'> return 0; </span>
+<span style='background-color:#4A789C'> </span><span style='background-color:#85C1F5'>printf("Hello world!\n")</span><span style='background-color:#4A789C'>; </span> <span class='c1'>// Unreachable region's counter is zero</span>
+<span style='background-color:#4A789C'>}</span>
+</pre>`
+
+The zero counters allow the code coverage tool to display proper line execution
+counts for the unreachable lines and highlight the unreachable code.
+Without them, the tool would think that those lines and regions were still
+executed, as it doesn't possess the frontend's knowledge.
+
+LLVM IR Representation
+======================
+
+The coverage mapping data is stored in the LLVM IR using a single global
+constant structure variable called *__llvm_coverage_mapping*
+with the *__llvm_covmap* section specifier.
+
+For example, letâs consider a C file and how it gets compiled to LLVM:
+
+.. _coverage mapping sample:
+
+.. code-block:: c
+
+ int foo() {
+ return 42;
+ }
+ int bar() {
+ return 13;
+ }
+
+The coverage mapping variable generated by Clang is:
+
+.. code-block:: llvm
+
+ @__llvm_coverage_mapping = internal constant { i32, i32, i32, i32, [2 x { i8*, i32, i32 }], [40 x i8] }
+ { i32 2, ; The number of function records
+ i32 20, ; The length of the string that contains the encoded translation unit filenames
+ i32 20, ; The length of the string that contains the encoded coverage mapping data
+ i32 0, ; Coverage mapping format version
+ [2 x { i8*, i32, i32 }] [ ; Function records
+ { i8*, i32, i32 } { i8* getelementptr inbounds ([3 x i8]* @__llvm_profile_name_foo, i32 0, i32 0), ; Function's name
+ i32 3, ; Function's name length
+ i32 9 ; Function's encoded coverage mapping data string length
+ },
+ { i8*, i32, i32 } { i8* getelementptr inbounds ([3 x i8]* @__llvm_profile_name_bar, i32 0, i32 0), ; Function's name
+ i32 3, ; Function's name length
+ i32 9 ; Function's encoded coverage mapping data string length
+ }],
+ [40 x i8] c"..." ; Encoded data (dissected later)
+ }, section "__llvm_covmap", align 8
+
+Version:
+--------
+
+The coverage mapping version number can have the following values:
+
+* 0 â The first (current) version of the coverage mapping format.
+
+.. _function records:
+
+Function record:
+----------------
+
+A function record is a structure of the following type:
+
+.. code-block:: llvm
+
+ { i8*, i32, i32 }
+
+It contains the pointer to the function's name, function's name length,
+and the length of the encoded mapping data for that function.
+
+Encoded data:
+-------------
+
+The encoded data is stored in a single string that contains
+the encoded filenames used by this translation unit and the encoded coverage
+mapping data for each function in this translation unit.
+
+The encoded data has the following structure:
+
+``[filenames, coverageMappingDataForFunctionRecord0, coverageMappingDataForFunctionRecord1, ..., padding]``
+
+If necessary, the encoded data is padded with zeroes so that the size
+of the data string is rounded up to the nearest multiple of 8 bytes.
+
+Dissecting the sample:
+^^^^^^^^^^^^^^^^^^^^^^
+
+Here's an overview of the encoded data that was stored in the
+IR for the `coverage mapping sample`_ that was shown earlier:
+
+* The IR contains the following string constant that represents the encoded
+ coverage mapping data for the sample translation unit:
+
+ .. code-block:: llvm
+
+ c"\01\12/Users/alex/test.c\01\00\00\01\01\01\0C\02\02\01\00\00\01\01\04\0C\02\02\00\00"
+
+* The string contains values that are encoded in the LEB128 format, which is
+ used throughout for storing integers. It also contains a string value.
+
+* The length of the substring that contains the encoded translation unit
+ filenames is the value of the second field in the *__llvm_coverage_mapping*
+ structure, which is 20, thus the filenames are encoded in this string:
+
+ .. code-block:: llvm
+
+ c"\01\12/Users/alex/test.c"
+
+ This string contains the following data:
+
+ * Its first byte has a value of ``0x01``. It stores the number of filenames
+ contained in this string.
+ * Its second byte stores the length of the first filename in this string.
+ * The remaining 18 bytes are used to store the first filename.
+
+* The length of the substring that contains the encoded coverage mapping data
+ for the first function is the value of the third field in the first
+ structure in an array of `function records`_ stored in the
+ fifth field of the *__llvm_coverage_mapping* structure, which is the 9.
+ Therefore, the coverage mapping for the first function record is encoded
+ in this string:
+
+ .. code-block:: llvm
+
+ c"\01\00\00\01\01\01\0C\02\02"
+
+ This string consists of the following bytes:
+
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x01`` | The number of file ids used by this function. There is only one file id used by the mapping data in this function. |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x00`` | An index into the filenames array which corresponds to the file "/Users/alex/test.c". |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x00`` | The number of counter expressions used by this function. This function doesn't use any expressions. |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x01`` | The number of mapping regions that are stored in an array for the function's file id #0. |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x01`` | The coverage mapping counter for the first region in this function. The value of 1 tells us that it's a coverage |
+ | | mapping counter that is a reference ot the profile instrumentation counter with an index of 0. |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x01`` | The starting line of the first mapping region in this function. |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x0C`` | The starting column of the first mapping region in this function. |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x02`` | The ending line of the first mapping region in this function. |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+ | ``0x02`` | The ending column of the first mapping region in this function. |
+ +----------+-------------------------------------------------------------------------------------------------------------------------+
+
+* The length of the substring that contains the encoded coverage mapping data
+ for the second function record is also 9. It's structured like the mapping data
+ for the first function record.
+
+* The two trailing bytes are zeroes and are used to pad the coverage mapping
+ data to give it the 8 byte alignment.
+
+Encoding
+========
+
+The per-function coverage mapping data is encoded as a stream of bytes,
+with a simple structure. The structure consists of the encoding
+`types <cvmtypes_>`_ like variable-length unsigned integers, that
+are used to encode `File ID Mapping`_, `Counter Expressions`_ and
+the `Mapping Regions`_.
+
+The format of the structure follows:
+
+ ``[file id mapping, counter expressions, mapping regions]``
+
+The translation unit filenames are encoded using the same encoding
+`types <cvmtypes_>`_ as the per-function coverage mapping data, with the
+following structure:
+
+ ``[numFilenames : LEB128, filename0 : string, filename1 : string, ...]``
+
+.. _cvmtypes:
+
+Types
+-----
+
+This section describes the basic types that are used by the encoding format
+and can appear after ``:`` in the ``[foo : type]`` description.
+
+.. _LEB128:
+
+LEB128
+^^^^^^
+
+LEB128 is an unsigned interger value that is encoded using DWARF's LEB128
+encoding, optimizing for the case where values are small
+(1 byte for values less than 128).
+
+.. _strings:
+
+Strings
+^^^^^^^
+
+``[length : LEB128, characters...]``
+
+String values are encoded with a `LEB value <LEB128_>`_ for the length
+of the string and a sequence of bytes for its characters.
+
+.. _file id mapping:
+
+File ID Mapping
+---------------
+
+``[numIndices : LEB128, filenameIndex0 : LEB128, filenameIndex1 : LEB128, ...]``
+
+File id mapping in a function's coverage mapping stream
+contains the indices into the translation unit's filenames array.
+
+Counter
+-------
+
+``[value : LEB128]``
+
+A `coverage mapping counter`_ is stored in a single `LEB value <LEB128_>`_.
+It is composed of two things --- the `tag <counter-tag_>`_
+which is stored in the lowest 2 bits, and the `counter data`_ which is stored
+in the remaining bits.
+
+.. _counter-tag:
+
+Tag:
+^^^^
+
+The counter's tag encodes the counter's kind
+and, if the counter is an expression, the expression's kind.
+The possible tag values are:
+
+* 0 - The counter is zero.
+
+* 1 - The counter is a reference to the profile instrumentation counter.
+
+* 2 - The counter is a subtraction expression.
+
+* 3 - The counter is an addition expression.
+
+.. _counter data:
+
+Data:
+^^^^^
+
+The counter's data is interpreted in the following manner:
+
+* When the counter is a reference to the profile instrumentation counter,
+ then the counter's data is the id of the profile counter.
+* When the counter is an expression, then the counter's data
+ is the index into the array of counter expressions.
+
+.. _Counter Expressions:
+
+Counter Expressions
+-------------------
+
+``[numExpressions : LEB128, expr0LHS : LEB128, expr0RHS : LEB128, expr1LHS : LEB128, expr1RHS : LEB128, ...]``
+
+Counter expressions consist of two counters as they
+represent binary arithmetic operations.
+The expression's kind is determined from the `tag <counter-tag_>`_ of the
+counter that references this expression.
+
+.. _Mapping Regions:
+
+Mapping Regions
+---------------
+
+``[numRegionArrays : LEB128, regionsForFile0, regionsForFile1, ...]``
+
+The mapping regions are stored in an array of sub-arrays where every
+region in a particular sub-array has the same file id.
+
+The file id for a sub-array of regions is the index of that
+sub-array in the main array e.g. The first sub-array will have the file id
+of 0.
+
+Sub-Array of Regions
+^^^^^^^^^^^^^^^^^^^^
+
+``[numRegions : LEB128, region0, region1, ...]``
+
+The mapping regions for a specific file id are stored in an array that is
+sorted in an ascending order by the region's starting location.
+
+Mapping Region
+^^^^^^^^^^^^^^
+
+``[header, source range]``
+
+The mapping region record contains two sub-records ---
+the `header`_, which stores the counter and/or the region's kind,
+and the `source range`_ that contains the starting and ending
+location of this region.
+
+.. _header:
+
+Header
+^^^^^^
+
+``[counter]``
+
+or
+
+``[pseudo-counter]``
+
+The header encodes the region's counter and the region's kind.
+
+The value of the counter's tag distinguishes between the counters and
+pseudo-counters --- if the tag is zero, than this header contains a
+pseudo-counter, otherwise this header contains an ordinary counter.
+
+Counter:
+""""""""
+
+A mapping region whose header has a counter with a non-zero tag is
+a code region.
+
+Pseudo-Counter:
+"""""""""""""""
+
+``[value : LEB128]``
+
+A pseudo-counter is stored in a single `LEB value <LEB128_>`_, just like
+the ordinary counter. It has the following interpretation:
+
+* bits 0-1: tag, which is always 0.
+
+* bit 2: expansionRegionTag. If this bit is set, then this mapping region
+ is an expansion region.
+
+* remaining bits: data. If this region is an expansion region, then the data
+ contains the expanded file id of that region.
+
+ Otherwise, the data contains the region's kind. The possible region
+ kind values are:
+
+ * 0 - This mapping region is a code region with a counter of zero.
+ * 2 - This mapping region is a skipped region.
+
+.. _source range:
+
+Source Range
+^^^^^^^^^^^^
+
+``[deltaLineStart : LEB128, columnStart : LEB128, numLines : LEB128, columnEnd : LEB128]``
+
+The source range record contains the following fields:
+
+* *deltaLineStart*: The difference between the starting line of the
+ current mapping region and the starting line of the previous mapping region.
+
+ If the current mapping region is the first region in the current
+ sub-array, then it stores the starting line of that region.
+
+* *columnStart*: The starting column of the mapping region.
+
+* *numLines*: The difference between the ending line and the starting line
+ of the current mapping region.
+
+* *columnEnd*: The ending column of the mapping region.
Added: www-releases/trunk/3.6.2/docs/_sources/DebuggingJITedCode.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/DebuggingJITedCode.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/DebuggingJITedCode.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/DebuggingJITedCode.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,143 @@
+==============================
+Debugging JIT-ed Code With GDB
+==============================
+
+Background
+==========
+
+Without special runtime support, debugging dynamically generated code with
+GDB (as well as most debuggers) can be quite painful. Debuggers generally
+read debug information from the object file of the code, but for JITed
+code, there is no such file to look for.
+
+In order to communicate the necessary debug info to GDB, an interface for
+registering JITed code with debuggers has been designed and implemented for
+GDB and LLVM MCJIT. At a high level, whenever MCJIT generates new machine code,
+it does so in an in-memory object file that contains the debug information in
+DWARF format. MCJIT then adds this in-memory object file to a global list of
+dynamically generated object files and calls a special function
+(``__jit_debug_register_code``) marked noinline that GDB knows about. When
+GDB attaches to a process, it puts a breakpoint in this function and loads all
+of the object files in the global list. When MCJIT calls the registration
+function, GDB catches the breakpoint signal, loads the new object file from
+the inferior's memory, and resumes the execution. In this way, GDB can get the
+necessary debug information.
+
+GDB Version
+===========
+
+In order to debug code JIT-ed by LLVM, you need GDB 7.0 or newer, which is
+available on most modern distributions of Linux. The version of GDB that
+Apple ships with Xcode has been frozen at 6.3 for a while. LLDB may be a
+better option for debugging JIT-ed code on Mac OS X.
+
+
+Debugging MCJIT-ed code
+=======================
+
+The emerging MCJIT component of LLVM allows full debugging of JIT-ed code with
+GDB. This is due to MCJIT's ability to use the MC emitter to provide full
+DWARF debugging information to GDB.
+
+Note that lli has to be passed the ``-use-mcjit`` flag to JIT the code with
+MCJIT instead of the old JIT.
+
+Example
+-------
+
+Consider the following C code (with line numbers added to make the example
+easier to follow):
+
+..
+ FIXME:
+ Sphinx has the ability to automatically number these lines by adding
+ :linenos: on the line immediately following the `.. code-block:: c`, but
+ it looks like garbage; the line numbers don't even line up with the
+ lines. Is this a Sphinx bug, or is it a CSS problem?
+
+.. code-block:: c
+
+ 1 int compute_factorial(int n)
+ 2 {
+ 3 if (n <= 1)
+ 4 return 1;
+ 5
+ 6 int f = n;
+ 7 while (--n > 1)
+ 8 f *= n;
+ 9 return f;
+ 10 }
+ 11
+ 12
+ 13 int main(int argc, char** argv)
+ 14 {
+ 15 if (argc < 2)
+ 16 return -1;
+ 17 char firstletter = argv[1][0];
+ 18 int result = compute_factorial(firstletter - '0');
+ 19
+ 20 // Returned result is clipped at 255...
+ 21 return result;
+ 22 }
+
+Here is a sample command line session that shows how to build and run this
+code via ``lli`` inside GDB:
+
+.. code-block:: bash
+
+ $ $BINPATH/clang -cc1 -O0 -g -emit-llvm showdebug.c
+ $ gdb --quiet --args $BINPATH/lli -use-mcjit showdebug.ll 5
+ Reading symbols from $BINPATH/lli...done.
+ (gdb) b showdebug.c:6
+ No source file named showdebug.c.
+ Make breakpoint pending on future shared library load? (y or [n]) y
+ Breakpoint 1 (showdebug.c:6) pending.
+ (gdb) r
+ Starting program: $BINPATH/lli -use-mcjit showdebug.ll 5
+ [Thread debugging using libthread_db enabled]
+
+ Breakpoint 1, compute_factorial (n=5) at showdebug.c:6
+ 6 int f = n;
+ (gdb) p n
+ $1 = 5
+ (gdb) p f
+ $2 = 0
+ (gdb) n
+ 7 while (--n > 1)
+ (gdb) p f
+ $3 = 5
+ (gdb) b showdebug.c:9
+ Breakpoint 2 at 0x7ffff7ed404c: file showdebug.c, line 9.
+ (gdb) c
+ Continuing.
+
+ Breakpoint 2, compute_factorial (n=1) at showdebug.c:9
+ 9 return f;
+ (gdb) p f
+ $4 = 120
+ (gdb) bt
+ #0 compute_factorial (n=1) at showdebug.c:9
+ #1 0x00007ffff7ed40a9 in main (argc=2, argv=0x16677e0) at showdebug.c:18
+ #2 0x3500000001652748 in ?? ()
+ #3 0x00000000016677e0 in ?? ()
+ #4 0x0000000000000002 in ?? ()
+ #5 0x0000000000d953b3 in llvm::MCJIT::runFunction (this=0x16151f0, F=0x1603020, ArgValues=...) at /home/ebenders_test/llvm_svn_rw/lib/ExecutionEngine/MCJIT/MCJIT.cpp:161
+ #6 0x0000000000dc8872 in llvm::ExecutionEngine::runFunctionAsMain (this=0x16151f0, Fn=0x1603020, argv=..., envp=0x7fffffffe040)
+ at /home/ebenders_test/llvm_svn_rw/lib/ExecutionEngine/ExecutionEngine.cpp:397
+ #7 0x000000000059c583 in main (argc=4, argv=0x7fffffffe018, envp=0x7fffffffe040) at /home/ebenders_test/llvm_svn_rw/tools/lli/lli.cpp:324
+ (gdb) finish
+ Run till exit from #0 compute_factorial (n=1) at showdebug.c:9
+ 0x00007ffff7ed40a9 in main (argc=2, argv=0x16677e0) at showdebug.c:18
+ 18 int result = compute_factorial(firstletter - '0');
+ Value returned is $5 = 120
+ (gdb) p result
+ $6 = 23406408
+ (gdb) n
+ 21 return result;
+ (gdb) p result
+ $7 = 120
+ (gdb) c
+ Continuing.
+
+ Program exited with code 0170.
+ (gdb)
Added: www-releases/trunk/3.6.2/docs/_sources/DeveloperPolicy.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/DeveloperPolicy.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/DeveloperPolicy.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/DeveloperPolicy.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,569 @@
+=====================
+LLVM Developer Policy
+=====================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+This document contains the LLVM Developer Policy which defines the project's
+policy towards developers and their contributions. The intent of this policy is
+to eliminate miscommunication, rework, and confusion that might arise from the
+distributed nature of LLVM's development. By stating the policy in clear terms,
+we hope each developer can know ahead of time what to expect when making LLVM
+contributions. This policy covers all llvm.org subprojects, including Clang,
+LLDB, libc++, etc.
+
+This policy is also designed to accomplish the following objectives:
+
+#. Attract both users and developers to the LLVM project.
+
+#. Make life as simple and easy for contributors as possible.
+
+#. Keep the top of Subversion trees as stable as possible.
+
+#. Establish awareness of the project's :ref:`copyright, license, and patent
+ policies <copyright-license-patents>` with contributors to the project.
+
+This policy is aimed at frequent contributors to LLVM. People interested in
+contributing one-off patches can do so in an informal way by sending them to the
+`llvm-commits mailing list
+<http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>`_ and engaging another
+developer to see it through the process.
+
+Developer Policies
+==================
+
+This section contains policies that pertain to frequent LLVM developers. We
+always welcome `one-off patches`_ from people who do not routinely contribute to
+LLVM, but we expect more from frequent contributors to keep the system as
+efficient as possible for everyone. Frequent LLVM contributors are expected to
+meet the following requirements in order for LLVM to maintain a high standard of
+quality.
+
+Stay Informed
+-------------
+
+Developers should stay informed by reading at least the "dev" mailing list for
+the projects you are interested in, such as `llvmdev
+<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>`_ for LLVM, `cfe-dev
+<http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev>`_ for Clang, or `lldb-dev
+<http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev>`_ for LLDB. If you are
+doing anything more than just casual work on LLVM, it is suggested that you also
+subscribe to the "commits" mailing list for the subproject you're interested in,
+such as `llvm-commits
+<http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>`_, `cfe-commits
+<http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits>`_, or `lldb-commits
+<http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits>`_. Reading the
+"commits" list and paying attention to changes being made by others is a good
+way to see what other people are interested in and watching the flow of the
+project as a whole.
+
+We recommend that active developers register an email account with `LLVM
+Bugzilla <http://llvm.org/bugs/>`_ and preferably subscribe to the `llvm-bugs
+<http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs>`_ email list to keep track
+of bugs and enhancements occurring in LLVM. We really appreciate people who are
+proactive at catching incoming bugs in their components and dealing with them
+promptly.
+
+Please be aware that all public LLVM mailing lists are public and archived, and
+that notices of confidentiality or non-disclosure cannot be respected.
+
+.. _patch:
+.. _one-off patches:
+
+Making and Submitting a Patch
+-----------------------------
+
+When making a patch for review, the goal is to make it as easy for the reviewer
+to read it as possible. As such, we recommend that you:
+
+#. Make your patch against the Subversion trunk, not a branch, and not an old
+ version of LLVM. This makes it easy to apply the patch. For information on
+ how to check out SVN trunk, please see the `Getting Started
+ Guide <GettingStarted.html#checkout>`_.
+
+#. Similarly, patches should be submitted soon after they are generated. Old
+ patches may not apply correctly if the underlying code changes between the
+ time the patch was created and the time it is applied.
+
+#. Patches should be made with ``svn diff``, or similar. If you use a
+ different tool, make sure it uses the ``diff -u`` format and that it
+ doesn't contain clutter which makes it hard to read.
+
+#. If you are modifying generated files, such as the top-level ``configure``
+ script, please separate out those changes into a separate patch from the rest
+ of your changes.
+
+Once your patch is ready, submit it by emailing it to the appropriate project's
+commit mailing list (or commit it directly if applicable). Alternatively, some
+patches get sent to the project's development list or component of the LLVM bug
+tracker, but the commit list is the primary place for reviews and should
+generally be preferred.
+
+When sending a patch to a mailing list, it is a good idea to send it as an
+*attachment* to the message, not embedded into the text of the message. This
+ensures that your mailer will not mangle the patch when it sends it (e.g. by
+making whitespace changes or by wrapping lines).
+
+*For Thunderbird users:* Before submitting a patch, please open *Preferences >
+Advanced > General > Config Editor*, find the key
+``mail.content_disposition_type``, and set its value to ``1``. Without this
+setting, Thunderbird sends your attachment using ``Content-Disposition: inline``
+rather than ``Content-Disposition: attachment``. Apple Mail gamely displays such
+a file inline, making it difficult to work with for reviewers using that
+program.
+
+When submitting patches, please do not add confidentiality or non-disclosure
+notices to the patches themselves. These notices conflict with the `LLVM
+License`_ and may result in your contribution being excluded.
+
+.. _code review:
+
+Code Reviews
+------------
+
+LLVM has a code review policy. Code review is one way to increase the quality of
+software. We generally follow these policies:
+
+#. All developers are required to have significant changes reviewed before they
+ are committed to the repository.
+
+#. Code reviews are conducted by email on the relevant project's commit mailing
+ list, or alternatively on the project's development list or bug tracker.
+
+#. Code can be reviewed either before it is committed or after. We expect major
+ changes to be reviewed before being committed, but smaller changes (or
+ changes where the developer owns the component) can be reviewed after commit.
+
+#. The developer responsible for a code change is also responsible for making
+ all necessary review-related changes.
+
+#. Code review can be an iterative process, which continues until the patch is
+ ready to be committed. Specifically, once a patch is sent out for review, it
+ needs an explicit "looks good" before it is submitted. Do not assume silent
+ approval, or request active objections to the patch with a deadline.
+
+Sometimes code reviews will take longer than you would hope for, especially for
+larger features. Accepted ways to speed up review times for your patches are:
+
+* Review other people's patches. If you help out, everybody will be more
+ willing to do the same for you; goodwill is our currency.
+* Ping the patch. If it is urgent, provide reasons why it is important to you to
+ get this patch landed and ping it every couple of days. If it is
+ not urgent, the common courtesy ping rate is one week. Remember that you're
+ asking for valuable time from other professional developers.
+* Ask for help on IRC. Developers on IRC will be able to either help you
+ directly, or tell you who might be a good reviewer.
+* Split your patch into multiple smaller patches that build on each other. The
+ smaller your patch, the higher the probability that somebody will take a quick
+ look at it.
+
+Developers should participate in code reviews as both reviewers and
+reviewees. If someone is kind enough to review your code, you should return the
+favor for someone else. Note that anyone is welcome to review and give feedback
+on a patch, but only people with Subversion write access can approve it.
+
+There is a web based code review tool that can optionally be used
+for code reviews. See :doc:`Phabricator`.
+
+Code Owners
+-----------
+
+The LLVM Project relies on two features of its process to maintain rapid
+development in addition to the high quality of its source base: the combination
+of code review plus post-commit review for trusted maintainers. Having both is
+a great way for the project to take advantage of the fact that most people do
+the right thing most of the time, and only commit patches without pre-commit
+review when they are confident they are right.
+
+The trick to this is that the project has to guarantee that all patches that are
+committed are reviewed after they go in: you don't want everyone to assume
+someone else will review it, allowing the patch to go unreviewed. To solve this
+problem, we have a notion of an 'owner' for a piece of the code. The sole
+responsibility of a code owner is to ensure that a commit to their area of the
+code is appropriately reviewed, either by themself or by someone else. The list
+of current code owners can be found in the file
+`CODE_OWNERS.TXT <http://llvm.org/viewvc/llvm-project/llvm/trunk/CODE_OWNERS.TXT?view=markup>`_
+in the root of the LLVM source tree.
+
+Note that code ownership is completely different than reviewers: anyone can
+review a piece of code, and we welcome code review from anyone who is
+interested. Code owners are the "last line of defense" to guarantee that all
+patches that are committed are actually reviewed.
+
+Being a code owner is a somewhat unglamorous position, but it is incredibly
+important for the ongoing success of the project. Because people get busy,
+interests change, and unexpected things happen, code ownership is purely opt-in,
+and anyone can choose to resign their "title" at any time. For now, we do not
+have an official policy on how one gets elected to be a code owner.
+
+.. _include a testcase:
+
+Test Cases
+----------
+
+Developers are required to create test cases for any bugs fixed and any new
+features added. Some tips for getting your testcase approved:
+
+* All feature and regression test cases are added to the ``llvm/test``
+ directory. The appropriate sub-directory should be selected (see the
+ :doc:`Testing Guide <TestingGuide>` for details).
+
+* Test cases should be written in :doc:`LLVM assembly language <LangRef>`.
+
+* Test cases, especially for regressions, should be reduced as much as possible,
+ by :doc:`bugpoint <Bugpoint>` or manually. It is unacceptable to place an
+ entire failing program into ``llvm/test`` as this creates a *time-to-test*
+ burden on all developers. Please keep them short.
+
+Note that llvm/test and clang/test are designed for regression and small feature
+tests only. More extensive test cases (e.g., entire applications, benchmarks,
+etc) should be added to the ``llvm-test`` test suite. The llvm-test suite is
+for coverage (correctness, performance, etc) testing, not feature or regression
+testing.
+
+Quality
+-------
+
+The minimum quality standards that any change must satisfy before being
+committed to the main development branch are:
+
+#. Code must adhere to the `LLVM Coding Standards <CodingStandards.html>`_.
+
+#. Code must compile cleanly (no errors, no warnings) on at least one platform.
+
+#. Bug fixes and new features should `include a testcase`_ so we know if the
+ fix/feature ever regresses in the future.
+
+#. Code must pass the ``llvm/test`` test suite.
+
+#. The code must not cause regressions on a reasonable subset of llvm-test,
+ where "reasonable" depends on the contributor's judgement and the scope of
+ the change (more invasive changes require more testing). A reasonable subset
+ might be something like "``llvm-test/MultiSource/Benchmarks``".
+
+Additionally, the committer is responsible for addressing any problems found in
+the future that the change is responsible for. For example:
+
+* The code should compile cleanly on all supported platforms.
+
+* The changes should not cause any correctness regressions in the ``llvm-test``
+ suite and must not cause any major performance regressions.
+
+* The change set should not cause performance or correctness regressions for the
+ LLVM tools.
+
+* The changes should not cause performance or correctness regressions in code
+ compiled by LLVM on all applicable targets.
+
+* You are expected to address any `Bugzilla bugs <http://llvm.org/bugs/>`_ that
+ result from your change.
+
+We prefer for this to be handled before submission but understand that it isn't
+possible to test all of this for every submission. Our build bots and nightly
+testing infrastructure normally finds these problems. A good rule of thumb is
+to check the nightly testers for regressions the day after your change. Build
+bots will directly email you if a group of commits that included yours caused a
+failure. You are expected to check the build bot messages to see if they are
+your fault and, if so, fix the breakage.
+
+Commits that violate these quality standards (e.g. are very broken) may be
+reverted. This is necessary when the change blocks other developers from making
+progress. The developer is welcome to re-commit the change after the problem has
+been fixed.
+
+Obtaining Commit Access
+-----------------------
+
+We grant commit access to contributors with a track record of submitting high
+quality patches. If you would like commit access, please send an email to
+`Chris <mailto:sabre at nondot.org>`_ with the following information:
+
+#. The user name you want to commit with, e.g. "hacker".
+
+#. The full name and email address you want message to llvm-commits to come
+ from, e.g. "J. Random Hacker <hacker at yoyodyne.com>".
+
+#. A "password hash" of the password you want to use, e.g. "``2ACR96qjUqsyM``".
+ Note that you don't ever tell us what your password is; you just give it to
+ us in an encrypted form. To get this, run "``htpasswd``" (a utility that
+ comes with apache) in crypt mode (often enabled with "``-d``"), or find a web
+ page that will do it for you.
+
+Once you've been granted commit access, you should be able to check out an LLVM
+tree with an SVN URL of "https://username@llvm.org/..." instead of the normal
+anonymous URL of "http://llvm.org/...". The first time you commit you'll have
+to type in your password. Note that you may get a warning from SVN about an
+untrusted key; you can ignore this. To verify that your commit access works,
+please do a test commit (e.g. change a comment or add a blank line). Your first
+commit to a repository may require the autogenerated email to be approved by a
+mailing list. This is normal and will be done when the mailing list owner has
+time.
+
+If you have recently been granted commit access, these policies apply:
+
+#. You are granted *commit-after-approval* to all parts of LLVM. To get
+ approval, submit a `patch`_ to `llvm-commits
+ <http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>`_. When approved,
+ you may commit it yourself.
+
+#. You are allowed to commit patches without approval which you think are
+ obvious. This is clearly a subjective decision --- we simply expect you to
+ use good judgement. Examples include: fixing build breakage, reverting
+ obviously broken patches, documentation/comment changes, any other minor
+ changes.
+
+#. You are allowed to commit patches without approval to those portions of LLVM
+ that you have contributed or maintain (i.e., have been assigned
+ responsibility for), with the proviso that such commits must not break the
+ build. This is a "trust but verify" policy, and commits of this nature are
+ reviewed after they are committed.
+
+#. Multiple violations of these policies or a single egregious violation may
+ cause commit access to be revoked.
+
+In any case, your changes are still subject to `code review`_ (either before or
+after they are committed, depending on the nature of the change). You are
+encouraged to review other peoples' patches as well, but you aren't required
+to do so.
+
+.. _discuss the change/gather consensus:
+
+Making a Major Change
+---------------------
+
+When a developer begins a major new project with the aim of contributing it back
+to LLVM, they should inform the community with an email to the `llvmdev
+<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>`_ email list, to the extent
+possible. The reason for this is to:
+
+#. keep the community informed about future changes to LLVM,
+
+#. avoid duplication of effort by preventing multiple parties working on the
+ same thing and not knowing about it, and
+
+#. ensure that any technical issues around the proposed work are discussed and
+ resolved before any significant work is done.
+
+The design of LLVM is carefully controlled to ensure that all the pieces fit
+together well and are as consistent as possible. If you plan to make a major
+change to the way LLVM works or want to add a major new extension, it is a good
+idea to get consensus with the development community before you start working on
+it.
+
+Once the design of the new feature is finalized, the work itself should be done
+as a series of `incremental changes`_, not as a long-term development branch.
+
+.. _incremental changes:
+
+Incremental Development
+-----------------------
+
+In the LLVM project, we do all significant changes as a series of incremental
+patches. We have a strong dislike for huge changes or long-term development
+branches. Long-term development branches have a number of drawbacks:
+
+#. Branches must have mainline merged into them periodically. If the branch
+ development and mainline development occur in the same pieces of code,
+ resolving merge conflicts can take a lot of time.
+
+#. Other people in the community tend to ignore work on branches.
+
+#. Huge changes (produced when a branch is merged back onto mainline) are
+ extremely difficult to `code review`_.
+
+#. Branches are not routinely tested by our nightly tester infrastructure.
+
+#. Changes developed as monolithic large changes often don't work until the
+ entire set of changes is done. Breaking it down into a set of smaller
+ changes increases the odds that any of the work will be committed to the main
+ repository.
+
+To address these problems, LLVM uses an incremental development style and we
+require contributors to follow this practice when making a large/invasive
+change. Some tips:
+
+* Large/invasive changes usually have a number of secondary changes that are
+ required before the big change can be made (e.g. API cleanup, etc). These
+ sorts of changes can often be done before the major change is done,
+ independently of that work.
+
+* The remaining inter-related work should be decomposed into unrelated sets of
+ changes if possible. Once this is done, define the first increment and get
+ consensus on what the end goal of the change is.
+
+* Each change in the set can be stand alone (e.g. to fix a bug), or part of a
+ planned series of changes that works towards the development goal.
+
+* Each change should be kept as small as possible. This simplifies your work
+ (into a logical progression), simplifies code review and reduces the chance
+ that you will get negative feedback on the change. Small increments also
+ facilitate the maintenance of a high quality code base.
+
+* Often, an independent precursor to a big change is to add a new API and slowly
+ migrate clients to use the new API. Each change to use the new API is often
+ "obvious" and can be committed without review. Once the new API is in place
+ and used, it is much easier to replace the underlying implementation of the
+ API. This implementation change is logically separate from the API
+ change.
+
+If you are interested in making a large change, and this scares you, please make
+sure to first `discuss the change/gather consensus`_ then ask about the best way
+to go about making the change.
+
+Attribution of Changes
+----------------------
+
+When contributors submit a patch to an LLVM project, other developers with
+commit access may commit it for the author once appropriate (based on the
+progression of code review, etc.). When doing so, it is important to retain
+correct attribution of contributions to their contributors. However, we do not
+want the source code to be littered with random attributions "this code written
+by J. Random Hacker" (this is noisy and distracting). In practice, the revision
+control system keeps a perfect history of who changed what, and the CREDITS.txt
+file describes higher-level contributions. If you commit a patch for someone
+else, please say "patch contributed by J. Random Hacker!" in the commit
+message. Overall, please do not add contributor names to the source code.
+
+Also, don't commit patches authored by others unless they have submitted the
+patch to the project or you have been authorized to submit them on their behalf
+(you work together and your company authorized you to contribute the patches,
+etc.). The author should first submit them to the relevant project's commit
+list, development list, or LLVM bug tracker component. If someone sends you
+a patch privately, encourage them to submit it to the appropriate list first.
+
+
+IR Backwards Compatibility
+--------------------------
+
+When the IR format has to be changed, keep in mind that we try to maintain some
+backwards compatibility. The rules are intended as a balance between convenience
+for llvm users and not imposing a big burden on llvm developers:
+
+* The textual format is not backwards compatible. We don't change it too often,
+ but there are no specific promises.
+
+* The bitcode format produced by a X.Y release will be readable by all following
+ X.Z releases and the (X+1).0 release.
+
+* Newer releases can ignore features from older releases, but they cannot
+ miscompile them. For example, if nsw is ever replaced with something else,
+ dropping it would be a valid way to upgrade the IR.
+
+* Debug metadata is special in that it is currently dropped during upgrades.
+
+* Non-debug metadata is defined to be safe to drop, so a valid way to upgrade
+ it is to drop it. That is not very user friendly and a bit more effort is
+ expected, but no promises are made.
+
+.. _copyright-license-patents:
+
+Copyright, License, and Patents
+===============================
+
+.. note::
+
+ This section deals with legal matters but does not provide legal advice. We
+ are not lawyers --- please seek legal counsel from an attorney.
+
+This section addresses the issues of copyright, license and patents for the LLVM
+project. The copyright for the code is held by the individual contributors of
+the code and the terms of its license to LLVM users and developers is the
+`University of Illinois/NCSA Open Source License
+<http://www.opensource.org/licenses/UoI-NCSA.php>`_ (with portions dual licensed
+under the `MIT License <http://www.opensource.org/licenses/mit-license.php>`_,
+see below). As contributor to the LLVM project, you agree to allow any
+contributions to the project to licensed under these terms.
+
+Copyright
+---------
+
+The LLVM project does not require copyright assignments, which means that the
+copyright for the code in the project is held by its respective contributors who
+have each agreed to release their contributed code under the terms of the `LLVM
+License`_.
+
+An implication of this is that the LLVM license is unlikely to ever change:
+changing it would require tracking down all the contributors to LLVM and getting
+them to agree that a license change is acceptable for their contribution. Since
+there are no plans to change the license, this is not a cause for concern.
+
+As a contributor to the project, this means that you (or your company) retain
+ownership of the code you contribute, that it cannot be used in a way that
+contradicts the license (which is a liberal BSD-style license), and that the
+license for your contributions won't change without your approval in the
+future.
+
+.. _LLVM License:
+
+License
+-------
+
+We intend to keep LLVM perpetually open source and to use a liberal open source
+license. **As a contributor to the project, you agree that any contributions be
+licensed under the terms of the corresponding subproject.** All of the code in
+LLVM is available under the `University of Illinois/NCSA Open Source License
+<http://www.opensource.org/licenses/UoI-NCSA.php>`_, which boils down to
+this:
+
+* You can freely distribute LLVM.
+* You must retain the copyright notice if you redistribute LLVM.
+* Binaries derived from LLVM must reproduce the copyright notice (e.g. in an
+ included readme file).
+* You can't use our names to promote your LLVM derived products.
+* There's no warranty on LLVM at all.
+
+We believe this fosters the widest adoption of LLVM because it **allows
+commercial products to be derived from LLVM** with few restrictions and without
+a requirement for making any derived works also open source (i.e. LLVM's
+license is not a "copyleft" license like the GPL). We suggest that you read the
+`License <http://www.opensource.org/licenses/UoI-NCSA.php>`_ if further
+clarification is needed.
+
+In addition to the UIUC license, the runtime library components of LLVM
+(**compiler_rt, libc++, and libclc**) are also licensed under the `MIT License
+<http://www.opensource.org/licenses/mit-license.php>`_, which does not contain
+the binary redistribution clause. As a user of these runtime libraries, it
+means that you can choose to use the code under either license (and thus don't
+need the binary redistribution clause), and as a contributor to the code that
+you agree that any contributions to these libraries be licensed under both
+licenses. We feel that this is important for runtime libraries, because they
+are implicitly linked into applications and therefore should not subject those
+applications to the binary redistribution clause. This also means that it is ok
+to move code from (e.g.) libc++ to the LLVM core without concern, but that code
+cannot be moved from the LLVM core to libc++ without the copyright owner's
+permission.
+
+Note that the LLVM Project does distribute dragonegg, **which is
+GPL.** This means that anything "linked" into dragonegg must itself be compatible
+with the GPL, and must be releasable under the terms of the GPL. This implies
+that **any code linked into dragonegg and distributed to others may be subject to
+the viral aspects of the GPL** (for example, a proprietary code generator linked
+into dragonegg must be made available under the GPL). This is not a problem for
+code already distributed under a more liberal license (like the UIUC license),
+and GPL-containing subprojects are kept in separate SVN repositories whose
+LICENSE.txt files specifically indicate that they contain GPL code.
+
+We have no plans to change the license of LLVM. If you have questions or
+comments about the license, please contact the `LLVM Developer's Mailing
+List <mailto:llvmdev at cs.uiuc.edu>`_.
+
+Patents
+-------
+
+To the best of our knowledge, LLVM does not infringe on any patents (we have
+actually removed code from LLVM in the past that was found to infringe). Having
+code in LLVM that infringes on patents would violate an important goal of the
+project by making it hard or impossible to reuse the code for arbitrary purposes
+(including commercial use).
+
+When contributing code, we expect contributors to notify us of any potential for
+patent-related trouble with their changes (including from third parties). If
+you or your employer own the rights to a patent and would like to contribute
+code to LLVM that relies on it, we require that the copyright owner sign an
+agreement that allows any other user of LLVM to freely use your patent. Please
+contact the `oversight group <mailto:llvm-oversight at cs.uiuc.edu>`_ for more
+details.
Added: www-releases/trunk/3.6.2/docs/_sources/ExceptionHandling.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/ExceptionHandling.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/ExceptionHandling.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/ExceptionHandling.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,422 @@
+==========================
+Exception Handling in LLVM
+==========================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+This document is the central repository for all information pertaining to
+exception handling in LLVM. It describes the format that LLVM exception
+handling information takes, which is useful for those interested in creating
+front-ends or dealing directly with the information. Further, this document
+provides specific examples of what exception handling information is used for in
+C and C++.
+
+Itanium ABI Zero-cost Exception Handling
+----------------------------------------
+
+Exception handling for most programming languages is designed to recover from
+conditions that rarely occur during general use of an application. To that end,
+exception handling should not interfere with the main flow of an application's
+algorithm by performing checkpointing tasks, such as saving the current pc or
+register state.
+
+The Itanium ABI Exception Handling Specification defines a methodology for
+providing outlying data in the form of exception tables without inlining
+speculative exception handling code in the flow of an application's main
+algorithm. Thus, the specification is said to add "zero-cost" to the normal
+execution of an application.
+
+A more complete description of the Itanium ABI exception handling runtime
+support of can be found at `Itanium C++ ABI: Exception Handling
+<http://mentorembedded.github.com/cxx-abi/abi-eh.html>`_. A description of the
+exception frame format can be found at `Exception Frames
+<http://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html>`_,
+with details of the DWARF 4 specification at `DWARF 4 Standard
+<http://dwarfstd.org/Dwarf4Std.php>`_. A description for the C++ exception
+table formats can be found at `Exception Handling Tables
+<http://mentorembedded.github.com/cxx-abi/exceptions.pdf>`_.
+
+Setjmp/Longjmp Exception Handling
+---------------------------------
+
+Setjmp/Longjmp (SJLJ) based exception handling uses LLVM intrinsics
+`llvm.eh.sjlj.setjmp`_ and `llvm.eh.sjlj.longjmp`_ to handle control flow for
+exception handling.
+
+For each function which does exception processing --- be it ``try``/``catch``
+blocks or cleanups --- that function registers itself on a global frame
+list. When exceptions are unwinding, the runtime uses this list to identify
+which functions need processing.
+
+Landing pad selection is encoded in the call site entry of the function
+context. The runtime returns to the function via `llvm.eh.sjlj.longjmp`_, where
+a switch table transfers control to the appropriate landing pad based on the
+index stored in the function context.
+
+In contrast to DWARF exception handling, which encodes exception regions and
+frame information in out-of-line tables, SJLJ exception handling builds and
+removes the unwind frame context at runtime. This results in faster exception
+handling at the expense of slower execution when no exceptions are thrown. As
+exceptions are, by their nature, intended for uncommon code paths, DWARF
+exception handling is generally preferred to SJLJ.
+
+Overview
+--------
+
+When an exception is thrown in LLVM code, the runtime does its best to find a
+handler suited to processing the circumstance.
+
+The runtime first attempts to find an *exception frame* corresponding to the
+function where the exception was thrown. If the programming language supports
+exception handling (e.g. C++), the exception frame contains a reference to an
+exception table describing how to process the exception. If the language does
+not support exception handling (e.g. C), or if the exception needs to be
+forwarded to a prior activation, the exception frame contains information about
+how to unwind the current activation and restore the state of the prior
+activation. This process is repeated until the exception is handled. If the
+exception is not handled and no activations remain, then the application is
+terminated with an appropriate error message.
+
+Because different programming languages have different behaviors when handling
+exceptions, the exception handling ABI provides a mechanism for
+supplying *personalities*. An exception handling personality is defined by
+way of a *personality function* (e.g. ``__gxx_personality_v0`` in C++),
+which receives the context of the exception, an *exception structure*
+containing the exception object type and value, and a reference to the exception
+table for the current function. The personality function for the current
+compile unit is specified in a *common exception frame*.
+
+The organization of an exception table is language dependent. For C++, an
+exception table is organized as a series of code ranges defining what to do if
+an exception occurs in that range. Typically, the information associated with a
+range defines which types of exception objects (using C++ *type info*) that are
+handled in that range, and an associated action that should take place. Actions
+typically pass control to a *landing pad*.
+
+A landing pad corresponds roughly to the code found in the ``catch`` portion of
+a ``try``/``catch`` sequence. When execution resumes at a landing pad, it
+receives an *exception structure* and a *selector value* corresponding to the
+*type* of exception thrown. The selector is then used to determine which *catch*
+should actually process the exception.
+
+LLVM Code Generation
+====================
+
+From a C++ developer's perspective, exceptions are defined in terms of the
+``throw`` and ``try``/``catch`` statements. In this section we will describe the
+implementation of LLVM exception handling in terms of C++ examples.
+
+Throw
+-----
+
+Languages that support exception handling typically provide a ``throw``
+operation to initiate the exception process. Internally, a ``throw`` operation
+breaks down into two steps.
+
+#. A request is made to allocate exception space for an exception structure.
+ This structure needs to survive beyond the current activation. This structure
+ will contain the type and value of the object being thrown.
+
+#. A call is made to the runtime to raise the exception, passing the exception
+ structure as an argument.
+
+In C++, the allocation of the exception structure is done by the
+``__cxa_allocate_exception`` runtime function. The exception raising is handled
+by ``__cxa_throw``. The type of the exception is represented using a C++ RTTI
+structure.
+
+Try/Catch
+---------
+
+A call within the scope of a *try* statement can potentially raise an
+exception. In those circumstances, the LLVM C++ front-end replaces the call with
+an ``invoke`` instruction. Unlike a call, the ``invoke`` has two potential
+continuation points:
+
+#. where to continue when the call succeeds as per normal, and
+
+#. where to continue if the call raises an exception, either by a throw or the
+ unwinding of a throw
+
+The term used to define the place where an ``invoke`` continues after an
+exception is called a *landing pad*. LLVM landing pads are conceptually
+alternative function entry points where an exception structure reference and a
+type info index are passed in as arguments. The landing pad saves the exception
+structure reference and then proceeds to select the catch block that corresponds
+to the type info of the exception object.
+
+The LLVM :ref:`i_landingpad` is used to convey information about the landing
+pad to the back end. For C++, the ``landingpad`` instruction returns a pointer
+and integer pair corresponding to the pointer to the *exception structure* and
+the *selector value* respectively.
+
+The ``landingpad`` instruction takes a reference to the personality function to
+be used for this ``try``/``catch`` sequence. The remainder of the instruction is
+a list of *cleanup*, *catch*, and *filter* clauses. The exception is tested
+against the clauses sequentially from first to last. The clauses have the
+following meanings:
+
+- ``catch <type> @ExcType``
+
+ - This clause means that the landingpad block should be entered if the
+ exception being thrown is of type ``@ExcType`` or a subtype of
+ ``@ExcType``. For C++, ``@ExcType`` is a pointer to the ``std::type_info``
+ object (an RTTI object) representing the C++ exception type.
+
+ - If ``@ExcType`` is ``null``, any exception matches, so the landingpad
+ should always be entered. This is used for C++ catch-all blocks ("``catch
+ (...)``").
+
+ - When this clause is matched, the selector value will be equal to the value
+ returned by "``@llvm.eh.typeid.for(i8* @ExcType)``". This will always be a
+ positive value.
+
+- ``filter <type> [<type> @ExcType1, ..., <type> @ExcTypeN]``
+
+ - This clause means that the landingpad should be entered if the exception
+ being thrown does *not* match any of the types in the list (which, for C++,
+ are again specified as ``std::type_info`` pointers).
+
+ - C++ front-ends use this to implement C++ exception specifications, such as
+ "``void foo() throw (ExcType1, ..., ExcTypeN) { ... }``".
+
+ - When this clause is matched, the selector value will be negative.
+
+ - The array argument to ``filter`` may be empty; for example, "``[0 x i8**]
+ undef``". This means that the landingpad should always be entered. (Note
+ that such a ``filter`` would not be equivalent to "``catch i8* null``",
+ because ``filter`` and ``catch`` produce negative and positive selector
+ values respectively.)
+
+- ``cleanup``
+
+ - This clause means that the landingpad should always be entered.
+
+ - C++ front-ends use this for calling objects' destructors.
+
+ - When this clause is matched, the selector value will be zero.
+
+ - The runtime may treat "``cleanup``" differently from "``catch <type>
+ null``".
+
+ In C++, if an unhandled exception occurs, the language runtime will call
+ ``std::terminate()``, but it is implementation-defined whether the runtime
+ unwinds the stack and calls object destructors first. For example, the GNU
+ C++ unwinder does not call object destructors when an unhandled exception
+ occurs. The reason for this is to improve debuggability: it ensures that
+ ``std::terminate()`` is called from the context of the ``throw``, so that
+ this context is not lost by unwinding the stack. A runtime will typically
+ implement this by searching for a matching non-``cleanup`` clause, and
+ aborting if it does not find one, before entering any landingpad blocks.
+
+Once the landing pad has the type info selector, the code branches to the code
+for the first catch. The catch then checks the value of the type info selector
+against the index of type info for that catch. Since the type info index is not
+known until all the type infos have been gathered in the backend, the catch code
+must call the `llvm.eh.typeid.for`_ intrinsic to determine the index for a given
+type info. If the catch fails to match the selector then control is passed on to
+the next catch.
+
+Finally, the entry and exit of catch code is bracketed with calls to
+``__cxa_begin_catch`` and ``__cxa_end_catch``.
+
+* ``__cxa_begin_catch`` takes an exception structure reference as an argument
+ and returns the value of the exception object.
+
+* ``__cxa_end_catch`` takes no arguments. This function:
+
+ #. Locates the most recently caught exception and decrements its handler
+ count,
+
+ #. Removes the exception from the *caught* stack if the handler count goes to
+ zero, and
+
+ #. Destroys the exception if the handler count goes to zero and the exception
+ was not re-thrown by throw.
+
+ .. note::
+
+ a rethrow from within the catch may replace this call with a
+ ``__cxa_rethrow``.
+
+Cleanups
+--------
+
+A cleanup is extra code which needs to be run as part of unwinding a scope. C++
+destructors are a typical example, but other languages and language extensions
+provide a variety of different kinds of cleanups. In general, a landing pad may
+need to run arbitrary amounts of cleanup code before actually entering a catch
+block. To indicate the presence of cleanups, a :ref:`i_landingpad` should have
+a *cleanup* clause. Otherwise, the unwinder will not stop at the landing pad if
+there are no catches or filters that require it to.
+
+.. note::
+
+ Do not allow a new exception to propagate out of the execution of a
+ cleanup. This can corrupt the internal state of the unwinder. Different
+ languages describe different high-level semantics for these situations: for
+ example, C++ requires that the process be terminated, whereas Ada cancels both
+ exceptions and throws a third.
+
+When all cleanups are finished, if the exception is not handled by the current
+function, resume unwinding by calling the `resume
+instruction <LangRef.html#i_resume>`_, passing in the result of the
+``landingpad`` instruction for the original landing pad.
+
+Throw Filters
+-------------
+
+C++ allows the specification of which exception types may be thrown from a
+function. To represent this, a top level landing pad may exist to filter out
+invalid types. To express this in LLVM code the :ref:`i_landingpad` will have a
+filter clause. The clause consists of an array of type infos.
+``landingpad`` will return a negative value
+if the exception does not match any of the type infos. If no match is found then
+a call to ``__cxa_call_unexpected`` should be made, otherwise
+``_Unwind_Resume``. Each of these functions requires a reference to the
+exception structure. Note that the most general form of a ``landingpad``
+instruction can have any number of catch, cleanup, and filter clauses (though
+having more than one cleanup is pointless). The LLVM C++ front-end can generate
+such ``landingpad`` instructions due to inlining creating nested exception
+handling scopes.
+
+.. _undefined:
+
+Restrictions
+------------
+
+The unwinder delegates the decision of whether to stop in a call frame to that
+call frame's language-specific personality function. Not all unwinders guarantee
+that they will stop to perform cleanups. For example, the GNU C++ unwinder
+doesn't do so unless the exception is actually caught somewhere further up the
+stack.
+
+In order for inlining to behave correctly, landing pads must be prepared to
+handle selector results that they did not originally advertise. Suppose that a
+function catches exceptions of type ``A``, and it's inlined into a function that
+catches exceptions of type ``B``. The inliner will update the ``landingpad``
+instruction for the inlined landing pad to include the fact that ``B`` is also
+caught. If that landing pad assumes that it will only be entered to catch an
+``A``, it's in for a rude awakening. Consequently, landing pads must test for
+the selector results they understand and then resume exception propagation with
+the `resume instruction <LangRef.html#i_resume>`_ if none of the conditions
+match.
+
+Exception Handling Intrinsics
+=============================
+
+In addition to the ``landingpad`` and ``resume`` instructions, LLVM uses several
+intrinsic functions (name prefixed with ``llvm.eh``) to provide exception
+handling information at various points in generated code.
+
+.. _llvm.eh.typeid.for:
+
+``llvm.eh.typeid.for``
+----------------------
+
+.. code-block:: llvm
+
+ i32 @llvm.eh.typeid.for(i8* %type_info)
+
+
+This intrinsic returns the type info index in the exception table of the current
+function. This value can be used to compare against the result of
+``landingpad`` instruction. The single argument is a reference to a type info.
+
+Uses of this intrinsic are generated by the C++ front-end.
+
+SJLJ Intrinsics
+---------------
+
+The ``llvm.eh.sjlj`` intrinsics are used internally within LLVM's
+backend. Uses of them are generated by the backend's
+``SjLjEHPrepare`` pass.
+
+.. _llvm.eh.sjlj.setjmp:
+
+``llvm.eh.sjlj.setjmp``
+~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code-block:: llvm
+
+ i32 @llvm.eh.sjlj.setjmp(i8* %setjmp_buf)
+
+For SJLJ based exception handling, this intrinsic forces register saving for the
+current function and stores the address of the following instruction for use as
+a destination address by `llvm.eh.sjlj.longjmp`_. The buffer format and the
+overall functioning of this intrinsic is compatible with the GCC
+``__builtin_setjmp`` implementation allowing code built with the clang and GCC
+to interoperate.
+
+The single parameter is a pointer to a five word buffer in which the calling
+context is saved. The front end places the frame pointer in the first word, and
+the target implementation of this intrinsic should place the destination address
+for a `llvm.eh.sjlj.longjmp`_ in the second word. The following three words are
+available for use in a target-specific manner.
+
+.. _llvm.eh.sjlj.longjmp:
+
+``llvm.eh.sjlj.longjmp``
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code-block:: llvm
+
+ void @llvm.eh.sjlj.longjmp(i8* %setjmp_buf)
+
+For SJLJ based exception handling, the ``llvm.eh.sjlj.longjmp`` intrinsic is
+used to implement ``__builtin_longjmp()``. The single parameter is a pointer to
+a buffer populated by `llvm.eh.sjlj.setjmp`_. The frame pointer and stack
+pointer are restored from the buffer, then control is transferred to the
+destination address.
+
+``llvm.eh.sjlj.lsda``
+~~~~~~~~~~~~~~~~~~~~~
+
+.. code-block:: llvm
+
+ i8* @llvm.eh.sjlj.lsda()
+
+For SJLJ based exception handling, the ``llvm.eh.sjlj.lsda`` intrinsic returns
+the address of the Language Specific Data Area (LSDA) for the current
+function. The SJLJ front-end code stores this address in the exception handling
+function context for use by the runtime.
+
+``llvm.eh.sjlj.callsite``
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code-block:: llvm
+
+ void @llvm.eh.sjlj.callsite(i32 %call_site_num)
+
+For SJLJ based exception handling, the ``llvm.eh.sjlj.callsite`` intrinsic
+identifies the callsite value associated with the following ``invoke``
+instruction. This is used to ensure that landing pad entries in the LSDA are
+generated in matching order.
+
+Asm Table Formats
+=================
+
+There are two tables that are used by the exception handling runtime to
+determine which actions should be taken when an exception is thrown.
+
+Exception Handling Frame
+------------------------
+
+An exception handling frame ``eh_frame`` is very similar to the unwind frame
+used by DWARF debug info. The frame contains all the information necessary to
+tear down the current frame and restore the state of the prior frame. There is
+an exception handling frame for each function in a compile unit, plus a common
+exception handling frame that defines information common to all functions in the
+unit.
+
+Exception Tables
+----------------
+
+An exception table contains information about what actions to take when an
+exception is thrown in a particular part of a function's code. There is one
+exception table per function, except leaf functions and functions that have
+calls only to non-throwing functions. They do not need an exception table.
Added: www-releases/trunk/3.6.2/docs/_sources/ExtendingLLVM.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/ExtendingLLVM.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/ExtendingLLVM.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/ExtendingLLVM.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,304 @@
+============================================================
+Extending LLVM: Adding instructions, intrinsics, types, etc.
+============================================================
+
+Introduction and Warning
+========================
+
+
+During the course of using LLVM, you may wish to customize it for your research
+project or for experimentation. At this point, you may realize that you need to
+add something to LLVM, whether it be a new fundamental type, a new intrinsic
+function, or a whole new instruction.
+
+When you come to this realization, stop and think. Do you really need to extend
+LLVM? Is it a new fundamental capability that LLVM does not support at its
+current incarnation or can it be synthesized from already pre-existing LLVM
+elements? If you are not sure, ask on the `LLVM-dev
+<http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev>`_ list. The reason is that
+extending LLVM will get involved as you need to update all the different passes
+that you intend to use with your extension, and there are ``many`` LLVM analyses
+and transformations, so it may be quite a bit of work.
+
+Adding an `intrinsic function`_ is far easier than adding an
+instruction, and is transparent to optimization passes. If your added
+functionality can be expressed as a function call, an intrinsic function is the
+method of choice for LLVM extension.
+
+Before you invest a significant amount of effort into a non-trivial extension,
+**ask on the list** if what you are looking to do can be done with
+already-existing infrastructure, or if maybe someone else is already working on
+it. You will save yourself a lot of time and effort by doing so.
+
+.. _intrinsic function:
+
+Adding a new intrinsic function
+===============================
+
+Adding a new intrinsic function to LLVM is much easier than adding a new
+instruction. Almost all extensions to LLVM should start as an intrinsic
+function and then be turned into an instruction if warranted.
+
+#. ``llvm/docs/LangRef.html``:
+
+ Document the intrinsic. Decide whether it is code generator specific and
+ what the restrictions are. Talk to other people about it so that you are
+ sure it's a good idea.
+
+#. ``llvm/include/llvm/IR/Intrinsics*.td``:
+
+ Add an entry for your intrinsic. Describe its memory access characteristics
+ for optimization (this controls whether it will be DCE'd, CSE'd, etc). Note
+ that any intrinsic using the ``llvm_int_ty`` type for an argument will
+ be deemed by ``tblgen`` as overloaded and the corresponding suffix will
+ be required on the intrinsic's name.
+
+#. ``llvm/lib/Analysis/ConstantFolding.cpp``:
+
+ If it is possible to constant fold your intrinsic, add support to it in the
+ ``canConstantFoldCallTo`` and ``ConstantFoldCall`` functions.
+
+#. ``llvm/test/*``:
+
+ Add test cases for your test cases to the test suite
+
+Once the intrinsic has been added to the system, you must add code generator
+support for it. Generally you must do the following steps:
+
+Add support to the .td file for the target(s) of your choice in
+``lib/Target/*/*.td``.
+
+ This is usually a matter of adding a pattern to the .td file that matches the
+ intrinsic, though it may obviously require adding the instructions you want to
+ generate as well. There are lots of examples in the PowerPC and X86 backend
+ to follow.
+
+Adding a new SelectionDAG node
+==============================
+
+As with intrinsics, adding a new SelectionDAG node to LLVM is much easier than
+adding a new instruction. New nodes are often added to help represent
+instructions common to many targets. These nodes often map to an LLVM
+instruction (add, sub) or intrinsic (byteswap, population count). In other
+cases, new nodes have been added to allow many targets to perform a common task
+(converting between floating point and integer representation) or capture more
+complicated behavior in a single node (rotate).
+
+#. ``include/llvm/CodeGen/ISDOpcodes.h``:
+
+ Add an enum value for the new SelectionDAG node.
+
+#. ``lib/CodeGen/SelectionDAG/SelectionDAG.cpp``:
+
+ Add code to print the node to ``getOperationName``. If your new node can be
+ evaluated at compile time when given constant arguments (such as an add of a
+ constant with another constant), find the ``getNode`` method that takes the
+ appropriate number of arguments, and add a case for your node to the switch
+ statement that performs constant folding for nodes that take the same number
+ of arguments as your new node.
+
+#. ``lib/CodeGen/SelectionDAG/LegalizeDAG.cpp``:
+
+ Add code to `legalize, promote, and expand
+ <CodeGenerator.html#selectiondag_legalize>`_ the node as necessary. At a
+ minimum, you will need to add a case statement for your node in
+ ``LegalizeOp`` which calls LegalizeOp on the node's operands, and returns a
+ new node if any of the operands changed as a result of being legalized. It
+ is likely that not all targets supported by the SelectionDAG framework will
+ natively support the new node. In this case, you must also add code in your
+ node's case statement in ``LegalizeOp`` to Expand your node into simpler,
+ legal operations. The case for ``ISD::UREM`` for expanding a remainder into
+ a divide, multiply, and a subtract is a good example.
+
+#. ``lib/CodeGen/SelectionDAG/LegalizeDAG.cpp``:
+
+ If targets may support the new node being added only at certain sizes, you
+ will also need to add code to your node's case statement in ``LegalizeOp``
+ to Promote your node's operands to a larger size, and perform the correct
+ operation. You will also need to add code to ``PromoteOp`` to do this as
+ well. For a good example, see ``ISD::BSWAP``, which promotes its operand to
+ a wider size, performs the byteswap, and then shifts the correct bytes right
+ to emulate the narrower byteswap in the wider type.
+
+#. ``lib/CodeGen/SelectionDAG/LegalizeDAG.cpp``:
+
+ Add a case for your node in ``ExpandOp`` to teach the legalizer how to
+ perform the action represented by the new node on a value that has been split
+ into high and low halves. This case will be used to support your node with a
+ 64 bit operand on a 32 bit target.
+
+#. ``lib/CodeGen/SelectionDAG/DAGCombiner.cpp``:
+
+ If your node can be combined with itself, or other existing nodes in a
+ peephole-like fashion, add a visit function for it, and call that function
+ from. There are several good examples for simple combines you can do;
+ ``visitFABS`` and ``visitSRL`` are good starting places.
+
+#. ``lib/Target/PowerPC/PPCISelLowering.cpp``:
+
+ Each target has an implementation of the ``TargetLowering`` class, usually in
+ its own file (although some targets include it in the same file as the
+ DAGToDAGISel). The default behavior for a target is to assume that your new
+ node is legal for all types that are legal for that target. If this target
+ does not natively support your node, then tell the target to either Promote
+ it (if it is supported at a larger type) or Expand it. This will cause the
+ code you wrote in ``LegalizeOp`` above to decompose your new node into other
+ legal nodes for this target.
+
+#. ``lib/Target/TargetSelectionDAG.td``:
+
+ Most current targets supported by LLVM generate code using the DAGToDAG
+ method, where SelectionDAG nodes are pattern matched to target-specific
+ nodes, which represent individual instructions. In order for the targets to
+ match an instruction to your new node, you must add a def for that node to
+ the list in this file, with the appropriate type constraints. Look at
+ ``add``, ``bswap``, and ``fadd`` for examples.
+
+#. ``lib/Target/PowerPC/PPCInstrInfo.td``:
+
+ Each target has a tablegen file that describes the target's instruction set.
+ For targets that use the DAGToDAG instruction selection framework, add a
+ pattern for your new node that uses one or more target nodes. Documentation
+ for this is a bit sparse right now, but there are several decent examples.
+ See the patterns for ``rotl`` in ``PPCInstrInfo.td``.
+
+#. TODO: document complex patterns.
+
+#. ``llvm/test/CodeGen/*``:
+
+ Add test cases for your new node to the test suite.
+ ``llvm/test/CodeGen/X86/bswap.ll`` is a good example.
+
+Adding a new instruction
+========================
+
+.. warning::
+
+ Adding instructions changes the bitcode format, and it will take some effort
+ to maintain compatibility with the previous version. Only add an instruction
+ if it is absolutely necessary.
+
+#. ``llvm/include/llvm/Instruction.def``:
+
+ add a number for your instruction and an enum name
+
+#. ``llvm/include/llvm/Instructions.h``:
+
+ add a definition for the class that will represent your instruction
+
+#. ``llvm/include/llvm/Support/InstVisitor.h``:
+
+ add a prototype for a visitor to your new instruction type
+
+#. ``llvm/lib/AsmParser/Lexer.l``:
+
+ add a new token to parse your instruction from assembly text file
+
+#. ``llvm/lib/AsmParser/llvmAsmParser.y``:
+
+ add the grammar on how your instruction can be read and what it will
+ construct as a result
+
+#. ``llvm/lib/Bitcode/Reader/Reader.cpp``:
+
+ add a case for your instruction and how it will be parsed from bitcode
+
+#. ``llvm/lib/VMCore/Instruction.cpp``:
+
+ add a case for how your instruction will be printed out to assembly
+
+#. ``llvm/lib/VMCore/Instructions.cpp``:
+
+ implement the class you defined in ``llvm/include/llvm/Instructions.h``
+
+#. Test your instruction
+
+#. ``llvm/lib/Target/*``:
+
+ add support for your instruction to code generators, or add a lowering pass.
+
+#. ``llvm/test/*``:
+
+ add your test cases to the test suite.
+
+Also, you need to implement (or modify) any analyses or passes that you want to
+understand this new instruction.
+
+Adding a new type
+=================
+
+.. warning::
+
+ Adding new types changes the bitcode format, and will break compatibility with
+ currently-existing LLVM installations. Only add new types if it is absolutely
+ necessary.
+
+Adding a fundamental type
+-------------------------
+
+#. ``llvm/include/llvm/Type.h``:
+
+ add enum for the new type; add static ``Type*`` for this type
+
+#. ``llvm/lib/VMCore/Type.cpp``:
+
+ add mapping from ``TypeID`` => ``Type*``; initialize the static ``Type*``
+
+#. ``llvm/lib/AsmReader/Lexer.l``:
+
+ add ability to parse in the type from text assembly
+
+#. ``llvm/lib/AsmReader/llvmAsmParser.y``:
+
+ add a token for that type
+
+Adding a derived type
+---------------------
+
+#. ``llvm/include/llvm/Type.h``:
+
+ add enum for the new type; add a forward declaration of the type also
+
+#. ``llvm/include/llvm/DerivedTypes.h``:
+
+ add new class to represent new class in the hierarchy; add forward
+ declaration to the TypeMap value type
+
+#. ``llvm/lib/VMCore/Type.cpp``:
+
+ add support for derived type to:
+
+ .. code-block:: c++
+
+ std::string getTypeDescription(const Type &Ty,
+ std::vector<const Type*> &TypeStack)
+ bool TypesEqual(const Type *Ty, const Type *Ty2,
+ std::map<const Type*, const Type*> &EqTypes)
+
+ add necessary member functions for type, and factory methods
+
+#. ``llvm/lib/AsmReader/Lexer.l``:
+
+ add ability to parse in the type from text assembly
+
+#. ``llvm/lib/Bitcode/Writer/Writer.cpp``:
+
+ modify ``void BitcodeWriter::outputType(const Type *T)`` to serialize your
+ type
+
+#. ``llvm/lib/Bitcode/Reader/Reader.cpp``:
+
+ modify ``const Type *BitcodeReader::ParseType()`` to read your data type
+
+#. ``llvm/lib/VMCore/AsmWriter.cpp``:
+
+ modify
+
+ .. code-block:: c++
+
+ void calcTypeName(const Type *Ty,
+ std::vector<const Type*> &TypeStack,
+ std::map<const Type*,std::string> &TypeNames,
+ std::string &Result)
+
+ to output the new derived type
Added: www-releases/trunk/3.6.2/docs/_sources/Extensions.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/Extensions.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/Extensions.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/Extensions.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,211 @@
+===============
+LLVM Extensions
+===============
+
+.. contents::
+ :local:
+
+.. toctree::
+ :hidden:
+
+Introduction
+============
+
+This document describes extensions to tools and formats LLVM seeks compatibility
+with.
+
+General Assembly Syntax
+===========================
+
+C99-style Hexadecimal Floating-point Constants
+----------------------------------------------
+
+LLVM's assemblers allow floating-point constants to be written in C99's
+hexadecimal format instead of decimal if desired.
+
+.. code-block:: gas
+
+ .section .data
+ .float 0x1c2.2ap3
+
+Machine-specific Assembly Syntax
+================================
+
+X86/COFF-Dependent
+------------------
+
+Relocations
+^^^^^^^^^^^
+
+The following additional relocation types are supported:
+
+**@IMGREL** (AT&T syntax only) generates an image-relative relocation that
+corresponds to the COFF relocation types ``IMAGE_REL_I386_DIR32NB`` (32-bit) or
+``IMAGE_REL_AMD64_ADDR32NB`` (64-bit).
+
+.. code-block:: gas
+
+ .text
+ fun:
+ mov foo at IMGREL(%ebx, %ecx, 4), %eax
+
+ .section .pdata
+ .long fun at IMGREL
+ .long (fun at imgrel + 0x3F)
+ .long $unwind$fun at imgrel
+
+**.secrel32** generates a relocation that corresponds to the COFF relocation
+types ``IMAGE_REL_I386_SECREL`` (32-bit) or ``IMAGE_REL_AMD64_SECREL`` (64-bit).
+
+**.secidx** relocation generates an index of the section that contains
+the target. It corresponds to the COFF relocation types
+``IMAGE_REL_I386_SECTION`` (32-bit) or ``IMAGE_REL_AMD64_SECTION`` (64-bit).
+
+.. code-block:: gas
+
+ .section .debug$S,"rn"
+ .long 4
+ .long 242
+ .long 40
+ .secrel32 _function_name
+ .secidx _function_name
+ ...
+
+``.linkonce`` Directive
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+
+ ``.linkonce [ comdat type ]``
+
+Supported COMDAT types:
+
+``discard``
+ Discards duplicate sections with the same COMDAT symbol. This is the default
+ if no type is specified.
+
+``one_only``
+ If the symbol is defined multiple times, the linker issues an error.
+
+``same_size``
+ Duplicates are discarded, but the linker issues an error if any have
+ different sizes.
+
+``same_contents``
+ Duplicates are discarded, but the linker issues an error if any duplicates
+ do not have exactly the same content.
+
+``largest``
+ Links the largest section from among the duplicates.
+
+``newest``
+ Links the newest section from among the duplicates.
+
+
+.. code-block:: gas
+
+ .section .text$foo
+ .linkonce
+ ...
+
+``.section`` Directive
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+MC supports passing the information in ``.linkonce`` at the end of
+``.section``. For example, these two codes are equivalent
+
+.. code-block:: gas
+
+ .section secName, "dr", discard, "Symbol1"
+ .globl Symbol1
+ Symbol1:
+ .long 1
+
+.. code-block:: gas
+
+ .section secName, "dr"
+ .linkonce discard
+ .globl Symbol1
+ Symbol1:
+ .long 1
+
+Note that in the combined form the COMDAT symbol is explicit. This
+extension exists to support multiple sections with the same name in
+different COMDATs:
+
+
+.. code-block:: gas
+
+ .section secName, "dr", discard, "Symbol1"
+ .globl Symbol1
+ Symbol1:
+ .long 1
+
+ .section secName, "dr", discard, "Symbol2"
+ .globl Symbol2
+ Symbol2:
+ .long 1
+
+In addition to the types allowed with ``.linkonce``, ``.section`` also accepts
+``associative``. The meaning is that the section is linked if a certain other
+COMDAT section is linked. This other section is indicated by the comdat symbol
+in this directive. It can be any symbol defined in the associated section, but
+is usually the associated section's comdat.
+
+ The following restrictions apply to the associated section:
+
+ 1. It must be a COMDAT section.
+ 2. It cannot be another associative COMDAT section.
+
+In the following example the symobl ``sym`` is the comdat symbol of ``.foo``
+and ``.bar`` is associated to ``.foo``.
+
+.. code-block:: gas
+
+ .section .foo,"bw",discard, "sym"
+ .section .bar,"rd",associative, "sym"
+
+Target Specific Behaviour
+=========================
+
+Windows on ARM
+--------------
+
+Stack Probe Emission
+^^^^^^^^^^^^^^^^^^^^
+
+The reference implementation (Microsoft Visual Studio 2012) emits stack probes
+in the following fashion:
+
+.. code-block:: gas
+
+ movw r4, #constant
+ bl __chkstk
+ sub.w sp, sp, r4
+
+However, this has the limitation of 32 MiB (±16MiB). In order to accommodate
+larger binaries, LLVM supports the use of ``-mcode-model=large`` to allow a 4GiB
+range via a slight deviation. It will generate an indirect jump as follows:
+
+.. code-block:: gas
+
+ movw r4, #constant
+ movw r12, :lower16:__chkstk
+ movt r12, :upper16:__chkstk
+ blx r12
+ sub.w sp, sp, r4
+
+Variable Length Arrays
+^^^^^^^^^^^^^^^^^^^^^^
+
+The reference implementation (Microsoft Visual Studio 2012) does not permit the
+emission of Variable Length Arrays (VLAs).
+
+The Windows ARM Itanium ABI extends the base ABI by adding support for emitting
+a dynamic stack allocation. When emitting a variable stack allocation, a call
+to ``__chkstk`` is emitted unconditionally to ensure that guard pages are setup
+properly. The emission of this stack probe emission is handled similar to the
+standard stack probe emission.
+
+The MSVC environment does not emit code for VLAs currently.
+
Added: www-releases/trunk/3.6.2/docs/_sources/FAQ.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/FAQ.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/FAQ.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/FAQ.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,477 @@
+================================
+Frequently Asked Questions (FAQ)
+================================
+
+.. contents::
+ :local:
+
+
+License
+=======
+
+Does the University of Illinois Open Source License really qualify as an "open source" license?
+-----------------------------------------------------------------------------------------------
+Yes, the license is `certified
+<http://www.opensource.org/licenses/UoI-NCSA.php>`_ by the Open Source
+Initiative (OSI).
+
+
+Can I modify LLVM source code and redistribute the modified source?
+-------------------------------------------------------------------
+Yes. The modified source distribution must retain the copyright notice and
+follow the three bulletted conditions listed in the `LLVM license
+<http://llvm.org/svn/llvm-project/llvm/trunk/LICENSE.TXT>`_.
+
+
+Can I modify the LLVM source code and redistribute binaries or other tools based on it, without redistributing the source?
+--------------------------------------------------------------------------------------------------------------------------
+Yes. This is why we distribute LLVM under a less restrictive license than GPL,
+as explained in the first question above.
+
+
+Source Code
+===========
+
+In what language is LLVM written?
+---------------------------------
+All of the LLVM tools and libraries are written in C++ with extensive use of
+the STL.
+
+
+How portable is the LLVM source code?
+-------------------------------------
+The LLVM source code should be portable to most modern Unix-like operating
+systems. Most of the code is written in standard C++ with operating system
+services abstracted to a support library. The tools required to build and
+test LLVM have been ported to a plethora of platforms.
+
+Some porting problems may exist in the following areas:
+
+* The autoconf/makefile build system relies heavily on UNIX shell tools,
+ like the Bourne Shell and sed. Porting to systems without these tools
+ (MacOS 9, Plan 9) will require more effort.
+
+What API do I use to store a value to one of the virtual registers in LLVM IR's SSA representation?
+---------------------------------------------------------------------------------------------------
+
+In short: you can't. It's actually kind of a silly question once you grok
+what's going on. Basically, in code like:
+
+.. code-block:: llvm
+
+ %result = add i32 %foo, %bar
+
+, ``%result`` is just a name given to the ``Value`` of the ``add``
+instruction. In other words, ``%result`` *is* the add instruction. The
+"assignment" doesn't explicitly "store" anything to any "virtual register";
+the "``=``" is more like the mathematical sense of equality.
+
+Longer explanation: In order to generate a textual representation of the
+IR, some kind of name has to be given to each instruction so that other
+instructions can textually reference it. However, the isomorphic in-memory
+representation that you manipulate from C++ has no such restriction since
+instructions can simply keep pointers to any other ``Value``'s that they
+reference. In fact, the names of dummy numbered temporaries like ``%1`` are
+not explicitly represented in the in-memory representation at all (see
+``Value::getName()``).
+
+Build Problems
+==============
+
+When I run configure, it finds the wrong C compiler.
+----------------------------------------------------
+The ``configure`` script attempts to locate first ``gcc`` and then ``cc``,
+unless it finds compiler paths set in ``CC`` and ``CXX`` for the C and C++
+compiler, respectively.
+
+If ``configure`` finds the wrong compiler, either adjust your ``PATH``
+environment variable or set ``CC`` and ``CXX`` explicitly.
+
+
+The ``configure`` script finds the right C compiler, but it uses the LLVM tools from a previous build. What do I do?
+---------------------------------------------------------------------------------------------------------------------
+The ``configure`` script uses the ``PATH`` to find executables, so if it's
+grabbing the wrong linker/assembler/etc, there are two ways to fix it:
+
+#. Adjust your ``PATH`` environment variable so that the correct program
+ appears first in the ``PATH``. This may work, but may not be convenient
+ when you want them *first* in your path for other work.
+
+#. Run ``configure`` with an alternative ``PATH`` that is correct. In a
+ Bourne compatible shell, the syntax would be:
+
+.. code-block:: console
+
+ % PATH=[the path without the bad program] ./configure ...
+
+This is still somewhat inconvenient, but it allows ``configure`` to do its
+work without having to adjust your ``PATH`` permanently.
+
+
+When creating a dynamic library, I get a strange GLIBC error.
+-------------------------------------------------------------
+Under some operating systems (i.e. Linux), libtool does not work correctly if
+GCC was compiled with the ``--disable-shared option``. To work around this,
+install your own version of GCC that has shared libraries enabled by default.
+
+
+I've updated my source tree from Subversion, and now my build is trying to use a file/directory that doesn't exist.
+-------------------------------------------------------------------------------------------------------------------
+You need to re-run configure in your object directory. When new Makefiles
+are added to the source tree, they have to be copied over to the object tree
+in order to be used by the build.
+
+
+I've modified a Makefile in my source tree, but my build tree keeps using the old version. What do I do?
+---------------------------------------------------------------------------------------------------------
+If the Makefile already exists in your object tree, you can just run the
+following command in the top level directory of your object tree:
+
+.. code-block:: console
+
+ % ./config.status <relative path to Makefile>;
+
+If the Makefile is new, you will have to modify the configure script to copy
+it over.
+
+
+I've upgraded to a new version of LLVM, and I get strange build errors.
+-----------------------------------------------------------------------
+Sometimes, changes to the LLVM source code alters how the build system works.
+Changes in ``libtool``, ``autoconf``, or header file dependencies are
+especially prone to this sort of problem.
+
+The best thing to try is to remove the old files and re-build. In most cases,
+this takes care of the problem. To do this, just type ``make clean`` and then
+``make`` in the directory that fails to build.
+
+
+I've built LLVM and am testing it, but the tests freeze.
+--------------------------------------------------------
+This is most likely occurring because you built a profile or release
+(optimized) build of LLVM and have not specified the same information on the
+``gmake`` command line.
+
+For example, if you built LLVM with the command:
+
+.. code-block:: console
+
+ % gmake ENABLE_PROFILING=1
+
+...then you must run the tests with the following commands:
+
+.. code-block:: console
+
+ % cd llvm/test
+ % gmake ENABLE_PROFILING=1
+
+Why do test results differ when I perform different types of builds?
+--------------------------------------------------------------------
+The LLVM test suite is dependent upon several features of the LLVM tools and
+libraries.
+
+First, the debugging assertions in code are not enabled in optimized or
+profiling builds. Hence, tests that used to fail may pass.
+
+Second, some tests may rely upon debugging options or behavior that is only
+available in the debug build. These tests will fail in an optimized or
+profile build.
+
+
+Compiling LLVM with GCC 3.3.2 fails, what should I do?
+------------------------------------------------------
+This is `a bug in GCC <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13392>`_,
+and affects projects other than LLVM. Try upgrading or downgrading your GCC.
+
+
+After Subversion update, rebuilding gives the error "No rule to make target".
+-----------------------------------------------------------------------------
+If the error is of the form:
+
+.. code-block:: console
+
+ gmake[2]: *** No rule to make target `/path/to/somefile',
+ needed by `/path/to/another/file.d'.
+ Stop.
+
+This may occur anytime files are moved within the Subversion repository or
+removed entirely. In this case, the best solution is to erase all ``.d``
+files, which list dependencies for source files, and rebuild:
+
+.. code-block:: console
+
+ % cd $LLVM_OBJ_DIR
+ % rm -f `find . -name \*\.d`
+ % gmake
+
+In other cases, it may be necessary to run ``make clean`` before rebuilding.
+
+
+Source Languages
+================
+
+What source languages are supported?
+------------------------------------
+LLVM currently has full support for C and C++ source languages. These are
+available through both `Clang <http://clang.llvm.org/>`_ and `DragonEgg
+<http://dragonegg.llvm.org/>`_.
+
+The PyPy developers are working on integrating LLVM into the PyPy backend so
+that PyPy language can translate to LLVM.
+
+
+I'd like to write a self-hosting LLVM compiler. How should I interface with the LLVM middle-end optimizers and back-end code generators?
+----------------------------------------------------------------------------------------------------------------------------------------
+Your compiler front-end will communicate with LLVM by creating a module in the
+LLVM intermediate representation (IR) format. Assuming you want to write your
+language's compiler in the language itself (rather than C++), there are 3
+major ways to tackle generating LLVM IR from a front-end:
+
+1. **Call into the LLVM libraries code using your language's FFI (foreign
+ function interface).**
+
+ * *for:* best tracks changes to the LLVM IR, .ll syntax, and .bc format
+
+ * *for:* enables running LLVM optimization passes without a emit/parse
+ overhead
+
+ * *for:* adapts well to a JIT context
+
+ * *against:* lots of ugly glue code to write
+
+2. **Emit LLVM assembly from your compiler's native language.**
+
+ * *for:* very straightforward to get started
+
+ * *against:* the .ll parser is slower than the bitcode reader when
+ interfacing to the middle end
+
+ * *against:* it may be harder to track changes to the IR
+
+3. **Emit LLVM bitcode from your compiler's native language.**
+
+ * *for:* can use the more-efficient bitcode reader when interfacing to the
+ middle end
+
+ * *against:* you'll have to re-engineer the LLVM IR object model and bitcode
+ writer in your language
+
+ * *against:* it may be harder to track changes to the IR
+
+If you go with the first option, the C bindings in include/llvm-c should help
+a lot, since most languages have strong support for interfacing with C. The
+most common hurdle with calling C from managed code is interfacing with the
+garbage collector. The C interface was designed to require very little memory
+management, and so is straightforward in this regard.
+
+What support is there for a higher level source language constructs for building a compiler?
+--------------------------------------------------------------------------------------------
+Currently, there isn't much. LLVM supports an intermediate representation
+which is useful for code representation but will not support the high level
+(abstract syntax tree) representation needed by most compilers. There are no
+facilities for lexical nor semantic analysis.
+
+
+I don't understand the ``GetElementPtr`` instruction. Help!
+-----------------------------------------------------------
+See `The Often Misunderstood GEP Instruction <GetElementPtr.html>`_.
+
+
+Using the C and C++ Front Ends
+==============================
+
+Can I compile C or C++ code to platform-independent LLVM bitcode?
+-----------------------------------------------------------------
+No. C and C++ are inherently platform-dependent languages. The most obvious
+example of this is the preprocessor. A very common way that C code is made
+portable is by using the preprocessor to include platform-specific code. In
+practice, information about other platforms is lost after preprocessing, so
+the result is inherently dependent on the platform that the preprocessing was
+targeting.
+
+Another example is ``sizeof``. It's common for ``sizeof(long)`` to vary
+between platforms. In most C front-ends, ``sizeof`` is expanded to a
+constant immediately, thus hard-wiring a platform-specific detail.
+
+Also, since many platforms define their ABIs in terms of C, and since LLVM is
+lower-level than C, front-ends currently must emit platform-specific IR in
+order to have the result conform to the platform ABI.
+
+
+Questions about code generated by the demo page
+===============================================
+
+What is this ``llvm.global_ctors`` and ``_GLOBAL__I_a...`` stuff that happens when I ``#include <iostream>``?
+-------------------------------------------------------------------------------------------------------------
+If you ``#include`` the ``<iostream>`` header into a C++ translation unit,
+the file will probably use the ``std::cin``/``std::cout``/... global objects.
+However, C++ does not guarantee an order of initialization between static
+objects in different translation units, so if a static ctor/dtor in your .cpp
+file used ``std::cout``, for example, the object would not necessarily be
+automatically initialized before your use.
+
+To make ``std::cout`` and friends work correctly in these scenarios, the STL
+that we use declares a static object that gets created in every translation
+unit that includes ``<iostream>``. This object has a static constructor
+and destructor that initializes and destroys the global iostream objects
+before they could possibly be used in the file. The code that you see in the
+``.ll`` file corresponds to the constructor and destructor registration code.
+
+If you would like to make it easier to *understand* the LLVM code generated
+by the compiler in the demo page, consider using ``printf()`` instead of
+``iostream``\s to print values.
+
+
+Where did all of my code go??
+-----------------------------
+If you are using the LLVM demo page, you may often wonder what happened to
+all of the code that you typed in. Remember that the demo script is running
+the code through the LLVM optimizers, so if your code doesn't actually do
+anything useful, it might all be deleted.
+
+To prevent this, make sure that the code is actually needed. For example, if
+you are computing some expression, return the value from the function instead
+of leaving it in a local variable. If you really want to constrain the
+optimizer, you can read from and assign to ``volatile`` global variables.
+
+
+What is this "``undef``" thing that shows up in my code?
+--------------------------------------------------------
+``undef`` is the LLVM way of representing a value that is not defined. You
+can get these if you do not initialize a variable before you use it. For
+example, the C function:
+
+.. code-block:: c
+
+ int X() { int i; return i; }
+
+Is compiled to "``ret i32 undef``" because "``i``" never has a value specified
+for it.
+
+
+Why does instcombine + simplifycfg turn a call to a function with a mismatched calling convention into "unreachable"? Why not make the verifier reject it?
+----------------------------------------------------------------------------------------------------------------------------------------------------------
+This is a common problem run into by authors of front-ends that are using
+custom calling conventions: you need to make sure to set the right calling
+convention on both the function and on each call to the function. For
+example, this code:
+
+.. code-block:: llvm
+
+ define fastcc void @foo() {
+ ret void
+ }
+ define void @bar() {
+ call void @foo()
+ ret void
+ }
+
+Is optimized to:
+
+.. code-block:: llvm
+
+ define fastcc void @foo() {
+ ret void
+ }
+ define void @bar() {
+ unreachable
+ }
+
+... with "``opt -instcombine -simplifycfg``". This often bites people because
+"all their code disappears". Setting the calling convention on the caller and
+callee is required for indirect calls to work, so people often ask why not
+make the verifier reject this sort of thing.
+
+The answer is that this code has undefined behavior, but it is not illegal.
+If we made it illegal, then every transformation that could potentially create
+this would have to ensure that it doesn't, and there is valid code that can
+create this sort of construct (in dead code). The sorts of things that can
+cause this to happen are fairly contrived, but we still need to accept them.
+Here's an example:
+
+.. code-block:: llvm
+
+ define fastcc void @foo() {
+ ret void
+ }
+ define internal void @bar(void()* %FP, i1 %cond) {
+ br i1 %cond, label %T, label %F
+ T:
+ call void %FP()
+ ret void
+ F:
+ call fastcc void %FP()
+ ret void
+ }
+ define void @test() {
+ %X = or i1 false, false
+ call void @bar(void()* @foo, i1 %X)
+ ret void
+ }
+
+In this example, "test" always passes ``@foo``/``false`` into ``bar``, which
+ensures that it is dynamically called with the right calling conv (thus, the
+code is perfectly well defined). If you run this through the inliner, you
+get this (the explicit "or" is there so that the inliner doesn't dead code
+eliminate a bunch of stuff):
+
+.. code-block:: llvm
+
+ define fastcc void @foo() {
+ ret void
+ }
+ define void @test() {
+ %X = or i1 false, false
+ br i1 %X, label %T.i, label %F.i
+ T.i:
+ call void @foo()
+ br label %bar.exit
+ F.i:
+ call fastcc void @foo()
+ br label %bar.exit
+ bar.exit:
+ ret void
+ }
+
+Here you can see that the inlining pass made an undefined call to ``@foo``
+with the wrong calling convention. We really don't want to make the inliner
+have to know about this sort of thing, so it needs to be valid code. In this
+case, dead code elimination can trivially remove the undefined code. However,
+if ``%X`` was an input argument to ``@test``, the inliner would produce this:
+
+.. code-block:: llvm
+
+ define fastcc void @foo() {
+ ret void
+ }
+
+ define void @test(i1 %X) {
+ br i1 %X, label %T.i, label %F.i
+ T.i:
+ call void @foo()
+ br label %bar.exit
+ F.i:
+ call fastcc void @foo()
+ br label %bar.exit
+ bar.exit:
+ ret void
+ }
+
+The interesting thing about this is that ``%X`` *must* be false for the
+code to be well-defined, but no amount of dead code elimination will be able
+to delete the broken call as unreachable. However, since
+``instcombine``/``simplifycfg`` turns the undefined call into unreachable, we
+end up with a branch on a condition that goes to unreachable: a branch to
+unreachable can never happen, so "``-inline -instcombine -simplifycfg``" is
+able to produce:
+
+.. code-block:: llvm
+
+ define fastcc void @foo() {
+ ret void
+ }
+ define void @test(i1 %X) {
+ F.i:
+ call fastcc void @foo()
+ ret void
+ }
Added: www-releases/trunk/3.6.2/docs/_sources/Frontend/PerformanceTips.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/Frontend/PerformanceTips.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/Frontend/PerformanceTips.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/Frontend/PerformanceTips.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,183 @@
+=====================================
+Performance Tips for Frontend Authors
+=====================================
+
+.. contents::
+ :local:
+ :depth: 2
+
+Abstract
+========
+
+The intended audience of this document is developers of language frontends
+targeting LLVM IR. This document is home to a collection of tips on how to
+generate IR that optimizes well. As with any optimizer, LLVM has its strengths
+and weaknesses. In some cases, surprisingly small changes in the source IR
+can have a large effect on the generated code.
+
+Avoid loads and stores of large aggregate type
+================================================
+
+LLVM currently does not optimize well loads and stores of large :ref:`aggregate
+types <t_aggregate>` (i.e. structs and arrays). As an alternative, consider
+loading individual fields from memory.
+
+Aggregates that are smaller than the largest (performant) load or store
+instruction supported by the targeted hardware are well supported. These can
+be an effective way to represent collections of small packed fields.
+
+Prefer zext over sext when legal
+==================================
+
+On some architectures (X86_64 is one), sign extension can involve an extra
+instruction whereas zero extension can be folded into a load. LLVM will try to
+replace a sext with a zext when it can be proven safe, but if you have
+information in your source language about the range of a integer value, it can
+be profitable to use a zext rather than a sext.
+
+Alternatively, you can :ref:`specify the range of the value using metadata
+<range-metadata>` and LLVM can do the sext to zext conversion for you.
+
+Zext GEP indices to machine register width
+============================================
+
+Internally, LLVM often promotes the width of GEP indices to machine register
+width. When it does so, it will default to using sign extension (sext)
+operations for safety. If your source language provides information about
+the range of the index, you may wish to manually extend indices to machine
+register width using a zext instruction.
+
+Other things to consider
+=========================
+
+#. Make sure that a DataLayout is provided (this will likely become required in
+ the near future, but is certainly important for optimization).
+
+#. Add nsw/nuw flags as appropriate. Reasoning about overflow is
+ generally hard for an optimizer so providing these facts from the frontend
+ can be very impactful.
+
+#. Use fast-math flags on floating point operations if legal. If you don't
+ need strict IEEE floating point semantics, there are a number of additional
+ optimizations that can be performed. This can be highly impactful for
+ floating point intensive computations.
+
+#. Use inbounds on geps. This can help to disambiguate some aliasing queries.
+
+#. Add noalias/align/dereferenceable/nonnull to function arguments and return
+ values as appropriate
+
+#. Mark functions as readnone/readonly or noreturn/nounwind when known. The
+ optimizer will try to infer these flags, but may not always be able to.
+ Manual annotations are particularly important for external functions that
+ the optimizer can not analyze.
+
+#. Use ptrtoint/inttoptr sparingly (they interfere with pointer aliasing
+ analysis), prefer GEPs
+
+#. Use the lifetime.start/lifetime.end and invariant.start/invariant.end
+ intrinsics where possible. Common profitable uses are for stack like data
+ structures (thus allowing dead store elimination) and for describing
+ life times of allocas (thus allowing smaller stack sizes).
+
+#. Use pointer aliasing metadata, especially tbaa metadata, to communicate
+ otherwise-non-deducible pointer aliasing facts
+
+#. Use the "most-private" possible linkage types for the functions being defined
+ (private, internal or linkonce_odr preferably)
+
+#. Mark invariant locations using !invariant.load and TBAA's constant flags
+
+#. Prefer globals over inttoptr of a constant address - this gives you
+ dereferencability information. In MCJIT, use getSymbolAddress to provide
+ actual address.
+
+#. Be wary of ordered and atomic memory operations. They are hard to optimize
+ and may not be well optimized by the current optimizer. Depending on your
+ source language, you may consider using fences instead.
+
+#. If calling a function which is known to throw an exception (unwind), use
+ an invoke with a normal destination which contains an unreachable
+ instruction. This form conveys to the optimizer that the call returns
+ abnormally. For an invoke which neither returns normally or requires unwind
+ code in the current function, you can use a noreturn call instruction if
+ desired. This is generally not required because the optimizer will convert
+ an invoke with an unreachable unwind destination to a call instruction.
+
+#. If you language uses range checks, consider using the IRCE pass. It is not
+ currently part of the standard pass order.
+
+#. For languages with numerous rarely executed guard conditions (e.g. null
+ checks, type checks, range checks) consider adding an extra execution or
+ two of LoopUnswith and LICM to your pass order. The standard pass order,
+ which is tuned for C and C++ applications, may not be sufficient to remove
+ all dischargeable checks from loops.
+
+#. Use profile metadata to indicate statically known cold paths, even if
+ dynamic profiling information is not available. This can make a large
+ difference in code placement and thus the performance of tight loops.
+
+#. When generating code for loops, try to avoid terminating the header block of
+ the loop earlier than necessary. If the terminator of the loop header
+ block is a loop exiting conditional branch, the effectiveness of LICM will
+ be limited for loads not in the header. (This is due to the fact that LLVM
+ may not know such a load is safe to speculatively execute and thus can't
+ lift an otherwise loop invariant load unless it can prove the exiting
+ condition is not taken.) It can be profitable, in some cases, to emit such
+ instructions into the header even if they are not used along a rarely
+ executed path that exits the loop. This guidance specifically does not
+ apply if the condition which terminates the loop header is itself invariant,
+ or can be easily discharged by inspecting the loop index variables.
+
+#. In hot loops, consider duplicating instructions from small basic blocks
+ which end in highly predictable terminators into their successor blocks.
+ If a hot successor block contains instructions which can be vectorized
+ with the duplicated ones, this can provide a noticeable throughput
+ improvement. Note that this is not always profitable and does involve a
+ potentially large increase in code size.
+
+#. Avoid high in-degree basic blocks (e.g. basic blocks with dozens or hundreds
+ of predecessors). Among other issues, the register allocator is known to
+ perform badly with confronted with such structures. The only exception to
+ this guidance is that a unified return block with high in-degree is fine.
+
+#. When checking a value against a constant, emit the check using a consistent
+ comparison type. The GVN pass *will* optimize redundant equalities even if
+ the type of comparison is inverted, but GVN only runs late in the pipeline.
+ As a result, you may miss the opportunity to run other important
+ optimizations. Improvements to EarlyCSE to remove this issue are tracked in
+ Bug 23333.
+
+#. Avoid using arithmetic intrinsics unless you are *required* by your source
+ language specification to emit a particular code sequence. The optimizer
+ is quite good at reasoning about general control flow and arithmetic, it is
+ not anywhere near as strong at reasoning about the various intrinsics. If
+ profitable for code generation purposes, the optimizer will likely form the
+ intrinsics itself late in the optimization pipeline. It is *very* rarely
+ profitable to emit these directly in the language frontend. This item
+ explicitly includes the use of the :ref:`overflow intrinsics <int_overflow>`.
+
+#. Avoid using the :ref:`assume intrinsic <int_assume>` until you've
+ established that a) there's no other way to express the given fact and b)
+ that fact is critical for optimization purposes. Assumes are a great
+ prototyping mechanism, but they can have negative effects on both compile
+ time and optimization effectiveness. The former is fixable with enough
+ effort, but the later is fairly fundamental to their designed purpose.
+
+p.s. If you want to help improve this document, patches expanding any of the
+above items into standalone sections of their own with a more complete
+discussion would be very welcome.
+
+
+Adding to this document
+=======================
+
+If you run across a case that you feel deserves to be covered here, please send
+a patch to `llvm-commits
+<http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>`_ for review.
+
+If you have questions on these items, please direct them to `llvmdev
+<http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev>`_. The more relevant
+context you are able to give to your question, the more likely it is to be
+answered.
+
Added: www-releases/trunk/3.6.2/docs/_sources/GarbageCollection.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/GarbageCollection.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/GarbageCollection.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/GarbageCollection.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,1014 @@
+=====================================
+Accurate Garbage Collection with LLVM
+=====================================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+Garbage collection is a widely used technique that frees the programmer from
+having to know the lifetimes of heap objects, making software easier to produce
+and maintain. Many programming languages rely on garbage collection for
+automatic memory management. There are two primary forms of garbage collection:
+conservative and accurate.
+
+Conservative garbage collection often does not require any special support from
+either the language or the compiler: it can handle non-type-safe programming
+languages (such as C/C++) and does not require any special information from the
+compiler. The `Boehm collector
+<http://www.hpl.hp.com/personal/Hans_Boehm/gc/>`__ is an example of a
+state-of-the-art conservative collector.
+
+Accurate garbage collection requires the ability to identify all pointers in the
+program at run-time (which requires that the source-language be type-safe in
+most cases). Identifying pointers at run-time requires compiler support to
+locate all places that hold live pointer variables at run-time, including the
+:ref:`processor stack and registers <gcroot>`.
+
+Conservative garbage collection is attractive because it does not require any
+special compiler support, but it does have problems. In particular, because the
+conservative garbage collector cannot *know* that a particular word in the
+machine is a pointer, it cannot move live objects in the heap (preventing the
+use of compacting and generational GC algorithms) and it can occasionally suffer
+from memory leaks due to integer values that happen to point to objects in the
+program. In addition, some aggressive compiler transformations can break
+conservative garbage collectors (though these seem rare in practice).
+
+Accurate garbage collectors do not suffer from any of these problems, but they
+can suffer from degraded scalar optimization of the program. In particular,
+because the runtime must be able to identify and update all pointers active in
+the program, some optimizations are less effective. In practice, however, the
+locality and performance benefits of using aggressive garbage collection
+techniques dominates any low-level losses.
+
+This document describes the mechanisms and interfaces provided by LLVM to
+support accurate garbage collection.
+
+Goals and non-goals
+-------------------
+
+LLVM's intermediate representation provides :ref:`garbage collection intrinsics
+<gc_intrinsics>` that offer support for a broad class of collector models. For
+instance, the intrinsics permit:
+
+* semi-space collectors
+
+* mark-sweep collectors
+
+* generational collectors
+
+* reference counting
+
+* incremental collectors
+
+* concurrent collectors
+
+* cooperative collectors
+
+We hope that the primitive support built into the LLVM IR is sufficient to
+support a broad class of garbage collected languages including Scheme, ML, Java,
+C#, Perl, Python, Lua, Ruby, other scripting languages, and more.
+
+However, LLVM does not itself provide a garbage collector --- this should be
+part of your language's runtime library. LLVM provides a framework for compile
+time :ref:`code generation plugins <plugin>`. The role of these plugins is to
+generate code and data structures which conforms to the *binary interface*
+specified by the *runtime library*. This is similar to the relationship between
+LLVM and DWARF debugging info, for example. The difference primarily lies in
+the lack of an established standard in the domain of garbage collection --- thus
+the plugins.
+
+The aspects of the binary interface with which LLVM's GC support is
+concerned are:
+
+* Creation of GC-safe points within code where collection is allowed to execute
+ safely.
+
+* Computation of the stack map. For each safe point in the code, object
+ references within the stack frame must be identified so that the collector may
+ traverse and perhaps update them.
+
+* Write barriers when storing object references to the heap. These are commonly
+ used to optimize incremental scans in generational collectors.
+
+* Emission of read barriers when loading object references. These are useful
+ for interoperating with concurrent collectors.
+
+There are additional areas that LLVM does not directly address:
+
+* Registration of global roots with the runtime.
+
+* Registration of stack map entries with the runtime.
+
+* The functions used by the program to allocate memory, trigger a collection,
+ etc.
+
+* Computation or compilation of type maps, or registration of them with the
+ runtime. These are used to crawl the heap for object references.
+
+In general, LLVM's support for GC does not include features which can be
+adequately addressed with other features of the IR and does not specify a
+particular binary interface. On the plus side, this means that you should be
+able to integrate LLVM with an existing runtime. On the other hand, it leaves a
+lot of work for the developer of a novel language. However, it's easy to get
+started quickly and scale up to a more sophisticated implementation as your
+compiler matures.
+
+Getting started
+===============
+
+Using a GC with LLVM implies many things, for example:
+
+* Write a runtime library or find an existing one which implements a GC heap.
+
+ #. Implement a memory allocator.
+
+ #. Design a binary interface for the stack map, used to identify references
+ within a stack frame on the machine stack.\*
+
+ #. Implement a stack crawler to discover functions on the call stack.\*
+
+ #. Implement a registry for global roots.
+
+ #. Design a binary interface for type maps, used to identify references
+ within heap objects.
+
+ #. Implement a collection routine bringing together all of the above.
+
+* Emit compatible code from your compiler.
+
+ * Initialization in the main function.
+
+ * Use the ``gc "..."`` attribute to enable GC code generation (or
+ ``F.setGC("...")``).
+
+ * Use ``@llvm.gcroot`` to mark stack roots.
+
+ * Use ``@llvm.gcread`` and/or ``@llvm.gcwrite`` to manipulate GC references,
+ if necessary.
+
+ * Allocate memory using the GC allocation routine provided by the runtime
+ library.
+
+ * Generate type maps according to your runtime's binary interface.
+
+* Write a compiler plugin to interface LLVM with the runtime library.\*
+
+ * Lower ``@llvm.gcread`` and ``@llvm.gcwrite`` to appropriate code
+ sequences.\*
+
+ * Compile LLVM's stack map to the binary form expected by the runtime.
+
+* Load the plugin into the compiler. Use ``llc -load`` or link the plugin
+ statically with your language's compiler.\*
+
+* Link program executables with the runtime.
+
+To help with several of these tasks (those indicated with a \*), LLVM includes a
+highly portable, built-in ShadowStack code generator. It is compiled into
+``llc`` and works even with the interpreter and C backends.
+
+In your compiler
+----------------
+
+To turn the shadow stack on for your functions, first call:
+
+.. code-block:: c++
+
+ F.setGC("shadow-stack");
+
+for each function your compiler emits. Since the shadow stack is built into
+LLVM, you do not need to load a plugin.
+
+Your compiler must also use ``@llvm.gcroot`` as documented. Don't forget to
+create a root for each intermediate value that is generated when evaluating an
+expression. In ``h(f(), g())``, the result of ``f()`` could easily be collected
+if evaluating ``g()`` triggers a collection.
+
+There's no need to use ``@llvm.gcread`` and ``@llvm.gcwrite`` over plain
+``load`` and ``store`` for now. You will need them when switching to a more
+advanced GC.
+
+In your runtime
+---------------
+
+The shadow stack doesn't imply a memory allocation algorithm. A semispace
+collector or building atop ``malloc`` are great places to start, and can be
+implemented with very little code.
+
+When it comes time to collect, however, your runtime needs to traverse the stack
+roots, and for this it needs to integrate with the shadow stack. Luckily, doing
+so is very simple. (This code is heavily commented to help you understand the
+data structure, but there are only 20 lines of meaningful code.)
+
+.. code-block:: c++
+
+ /// @brief The map for a single function's stack frame. One of these is
+ /// compiled as constant data into the executable for each function.
+ ///
+ /// Storage of metadata values is elided if the %metadata parameter to
+ /// @llvm.gcroot is null.
+ struct FrameMap {
+ int32_t NumRoots; //< Number of roots in stack frame.
+ int32_t NumMeta; //< Number of metadata entries. May be < NumRoots.
+ const void *Meta[0]; //< Metadata for each root.
+ };
+
+ /// @brief A link in the dynamic shadow stack. One of these is embedded in
+ /// the stack frame of each function on the call stack.
+ struct StackEntry {
+ StackEntry *Next; //< Link to next stack entry (the caller's).
+ const FrameMap *Map; //< Pointer to constant FrameMap.
+ void *Roots[0]; //< Stack roots (in-place array).
+ };
+
+ /// @brief The head of the singly-linked list of StackEntries. Functions push
+ /// and pop onto this in their prologue and epilogue.
+ ///
+ /// Since there is only a global list, this technique is not threadsafe.
+ StackEntry *llvm_gc_root_chain;
+
+ /// @brief Calls Visitor(root, meta) for each GC root on the stack.
+ /// root and meta are exactly the values passed to
+ /// @llvm.gcroot.
+ ///
+ /// Visitor could be a function to recursively mark live objects. Or it
+ /// might copy them to another heap or generation.
+ ///
+ /// @param Visitor A function to invoke for every GC root on the stack.
+ void visitGCRoots(void (*Visitor)(void **Root, const void *Meta)) {
+ for (StackEntry *R = llvm_gc_root_chain; R; R = R->Next) {
+ unsigned i = 0;
+
+ // For roots [0, NumMeta), the metadata pointer is in the FrameMap.
+ for (unsigned e = R->Map->NumMeta; i != e; ++i)
+ Visitor(&R->Roots[i], R->Map->Meta[i]);
+
+ // For roots [NumMeta, NumRoots), the metadata pointer is null.
+ for (unsigned e = R->Map->NumRoots; i != e; ++i)
+ Visitor(&R->Roots[i], NULL);
+ }
+ }
+
+About the shadow stack
+----------------------
+
+Unlike many GC algorithms which rely on a cooperative code generator to compile
+stack maps, this algorithm carefully maintains a linked list of stack roots
+[:ref:`Henderson2002 <henderson02>`]. This so-called "shadow stack" mirrors the
+machine stack. Maintaining this data structure is slower than using a stack map
+compiled into the executable as constant data, but has a significant portability
+advantage because it requires no special support from the target code generator,
+and does not require tricky platform-specific code to crawl the machine stack.
+
+The tradeoff for this simplicity and portability is:
+
+* High overhead per function call.
+
+* Not thread-safe.
+
+Still, it's an easy way to get started. After your compiler and runtime are up
+and running, writing a :ref:`plugin <plugin>` will allow you to take advantage
+of :ref:`more advanced GC features <collector-algos>` of LLVM in order to
+improve performance.
+
+.. _gc_intrinsics:
+
+IR features
+===========
+
+This section describes the garbage collection facilities provided by the
+:doc:`LLVM intermediate representation <LangRef>`. The exact behavior of these
+IR features is specified by the binary interface implemented by a :ref:`code
+generation plugin <plugin>`, not by this document.
+
+These facilities are limited to those strictly necessary; they are not intended
+to be a complete interface to any garbage collector. A program will need to
+interface with the GC library using the facilities provided by that program.
+
+Specifying GC code generation: ``gc "..."``
+-------------------------------------------
+
+.. code-block:: llvm
+
+ define ty @name(...) gc "name" { ...
+
+The ``gc`` function attribute is used to specify the desired GC style to the
+compiler. Its programmatic equivalent is the ``setGC`` method of ``Function``.
+
+Setting ``gc "name"`` on a function triggers a search for a matching code
+generation plugin "*name*"; it is that plugin which defines the exact nature of
+the code generated to support GC. If none is found, the compiler will raise an
+error.
+
+Specifying the GC style on a per-function basis allows LLVM to link together
+programs that use different garbage collection algorithms (or none at all).
+
+.. _gcroot:
+
+Identifying GC roots on the stack: ``llvm.gcroot``
+--------------------------------------------------
+
+.. code-block:: llvm
+
+ void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
+
+The ``llvm.gcroot`` intrinsic is used to inform LLVM that a stack variable
+references an object on the heap and is to be tracked for garbage collection.
+The exact impact on generated code is specified by a :ref:`compiler plugin
+<plugin>`. All calls to ``llvm.gcroot`` **must** reside inside the first basic
+block.
+
+A compiler which uses mem2reg to raise imperative code using ``alloca`` into SSA
+form need only add a call to ``@llvm.gcroot`` for those variables which a
+pointers into the GC heap.
+
+It is also important to mark intermediate values with ``llvm.gcroot``. For
+example, consider ``h(f(), g())``. Beware leaking the result of ``f()`` in the
+case that ``g()`` triggers a collection. Note, that stack variables must be
+initialized and marked with ``llvm.gcroot`` in function's prologue.
+
+The first argument **must** be a value referring to an alloca instruction or a
+bitcast of an alloca. The second contains a pointer to metadata that should be
+associated with the pointer, and **must** be a constant or global value
+address. If your target collector uses tags, use a null pointer for metadata.
+
+The ``%metadata`` argument can be used to avoid requiring heap objects to have
+'isa' pointers or tag bits. [Appel89_, Goldberg91_, Tolmach94_] If specified,
+its value will be tracked along with the location of the pointer in the stack
+frame.
+
+Consider the following fragment of Java code:
+
+.. code-block:: java
+
+ {
+ Object X; // A null-initialized reference to an object
+ ...
+ }
+
+This block (which may be located in the middle of a function or in a loop nest),
+could be compiled to this LLVM code:
+
+.. code-block:: llvm
+
+ Entry:
+ ;; In the entry block for the function, allocate the
+ ;; stack space for X, which is an LLVM pointer.
+ %X = alloca %Object*
+
+ ;; Tell LLVM that the stack space is a stack root.
+ ;; Java has type-tags on objects, so we pass null as metadata.
+ %tmp = bitcast %Object** %X to i8**
+ call void @llvm.gcroot(i8** %tmp, i8* null)
+ ...
+
+ ;; "CodeBlock" is the block corresponding to the start
+ ;; of the scope above.
+ CodeBlock:
+ ;; Java null-initializes pointers.
+ store %Object* null, %Object** %X
+
+ ...
+
+ ;; As the pointer goes out of scope, store a null value into
+ ;; it, to indicate that the value is no longer live.
+ store %Object* null, %Object** %X
+ ...
+
+Reading and writing references in the heap
+------------------------------------------
+
+Some collectors need to be informed when the mutator (the program that needs
+garbage collection) either reads a pointer from or writes a pointer to a field
+of a heap object. The code fragments inserted at these points are called *read
+barriers* and *write barriers*, respectively. The amount of code that needs to
+be executed is usually quite small and not on the critical path of any
+computation, so the overall performance impact of the barrier is tolerable.
+
+Barriers often require access to the *object pointer* rather than the *derived
+pointer* (which is a pointer to the field within the object). Accordingly,
+these intrinsics take both pointers as separate arguments for completeness. In
+this snippet, ``%object`` is the object pointer, and ``%derived`` is the derived
+pointer:
+
+.. code-block:: llvm
+
+ ;; An array type.
+ %class.Array = type { %class.Object, i32, [0 x %class.Object*] }
+ ...
+
+ ;; Load the object pointer from a gcroot.
+ %object = load %class.Array** %object_addr
+
+ ;; Compute the derived pointer.
+ %derived = getelementptr %object, i32 0, i32 2, i32 %n
+
+LLVM does not enforce this relationship between the object and derived pointer
+(although a :ref:`plugin <plugin>` might). However, it would be an unusual
+collector that violated it.
+
+The use of these intrinsics is naturally optional if the target GC does require
+the corresponding barrier. Such a GC plugin will replace the intrinsic calls
+with the corresponding ``load`` or ``store`` instruction if they are used.
+
+Write barrier: ``llvm.gcwrite``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: llvm
+
+ void @llvm.gcwrite(i8* %value, i8* %object, i8** %derived)
+
+For write barriers, LLVM provides the ``llvm.gcwrite`` intrinsic function. It
+has exactly the same semantics as a non-volatile ``store`` to the derived
+pointer (the third argument). The exact code generated is specified by a
+compiler :ref:`plugin <plugin>`.
+
+Many important algorithms require write barriers, including generational and
+concurrent collectors. Additionally, write barriers could be used to implement
+reference counting.
+
+Read barrier: ``llvm.gcread``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: llvm
+
+ i8* @llvm.gcread(i8* %object, i8** %derived)
+
+For read barriers, LLVM provides the ``llvm.gcread`` intrinsic function. It has
+exactly the same semantics as a non-volatile ``load`` from the derived pointer
+(the second argument). The exact code generated is specified by a
+:ref:`compiler plugin <plugin>`.
+
+Read barriers are needed by fewer algorithms than write barriers, and may have a
+greater performance impact since pointer reads are more frequent than writes.
+
+.. _plugin:
+
+Implementing a collector plugin
+===============================
+
+User code specifies which GC code generation to use with the ``gc`` function
+attribute or, equivalently, with the ``setGC`` method of ``Function``.
+
+To implement a GC plugin, it is necessary to subclass ``llvm::GCStrategy``,
+which can be accomplished in a few lines of boilerplate code. LLVM's
+infrastructure provides access to several important algorithms. For an
+uncontroversial collector, all that remains may be to compile LLVM's computed
+stack map to assembly code (using the binary representation expected by the
+runtime library). This can be accomplished in about 100 lines of code.
+
+This is not the appropriate place to implement a garbage collected heap or a
+garbage collector itself. That code should exist in the language's runtime
+library. The compiler plugin is responsible for generating code which conforms
+to the binary interface defined by library, most essentially the :ref:`stack map
+<stack-map>`.
+
+To subclass ``llvm::GCStrategy`` and register it with the compiler:
+
+.. code-block:: c++
+
+ // lib/MyGC/MyGC.cpp - Example LLVM GC plugin
+
+ #include "llvm/CodeGen/GCStrategy.h"
+ #include "llvm/CodeGen/GCMetadata.h"
+ #include "llvm/Support/Compiler.h"
+
+ using namespace llvm;
+
+ namespace {
+ class LLVM_LIBRARY_VISIBILITY MyGC : public GCStrategy {
+ public:
+ MyGC() {}
+ };
+
+ GCRegistry::Add<MyGC>
+ X("mygc", "My bespoke garbage collector.");
+ }
+
+This boilerplate collector does nothing. More specifically:
+
+* ``llvm.gcread`` calls are replaced with the corresponding ``load``
+ instruction.
+
+* ``llvm.gcwrite`` calls are replaced with the corresponding ``store``
+ instruction.
+
+* No safe points are added to the code.
+
+* The stack map is not compiled into the executable.
+
+Using the LLVM makefiles, this code
+can be compiled as a plugin using a simple makefile:
+
+.. code-block:: make
+
+ # lib/MyGC/Makefile
+
+ LEVEL := ../..
+ LIBRARYNAME = MyGC
+ LOADABLE_MODULE = 1
+
+ include $(LEVEL)/Makefile.common
+
+Once the plugin is compiled, code using it may be compiled using ``llc
+-load=MyGC.so`` (though MyGC.so may have some other platform-specific
+extension):
+
+::
+
+ $ cat sample.ll
+ define void @f() gc "mygc" {
+ entry:
+ ret void
+ }
+ $ llvm-as < sample.ll | llc -load=MyGC.so
+
+It is also possible to statically link the collector plugin into tools, such as
+a language-specific compiler front-end.
+
+.. _collector-algos:
+
+Overview of available features
+------------------------------
+
+``GCStrategy`` provides a range of features through which a plugin may do useful
+work. Some of these are callbacks, some are algorithms that can be enabled,
+disabled, or customized. This matrix summarizes the supported (and planned)
+features and correlates them with the collection techniques which typically
+require them.
+
+.. |v| unicode:: 0x2714
+ :trim:
+
+.. |x| unicode:: 0x2718
+ :trim:
+
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| Algorithm | Done | Shadow | refcount | mark- | copying | incremental | threaded | concurrent |
+| | | stack | | sweep | | | | |
++============+======+========+==========+=======+=========+=============+==========+============+
+| stack map | |v| | | | |x| | |x| | |x| | |x| | |x| |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| initialize | |v| | |x| | |x| | |x| | |x| | |x| | |x| | |x| |
+| roots | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| derived | NO | | | | | | **N**\* | **N**\* |
+| pointers | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| **custom | |v| | | | | | | | |
+| lowering** | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *gcroot* | |v| | |x| | |x| | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *gcwrite* | |v| | | |x| | | | |x| | | |x| |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *gcread* | |v| | | | | | | | |x| |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| **safe | | | | | | | | |
+| points** | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *in | |v| | | | |x| | |x| | |x| | |x| | |x| |
+| calls* | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *before | |v| | | | | | | |x| | |x| |
+| calls* | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *for | NO | | | | | | **N** | **N** |
+| loops* | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *before | |v| | | | | | | |x| | |x| |
+| escape* | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| emit code | NO | | | | | | **N** | **N** |
+| at safe | | | | | | | | |
+| points | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| **output** | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *assembly* | |v| | | | |x| | |x| | |x| | |x| | |x| |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *JIT* | NO | | | **?** | **?** | **?** | **?** | **?** |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| *obj* | NO | | | **?** | **?** | **?** | **?** | **?** |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| live | NO | | | **?** | **?** | **?** | **?** | **?** |
+| analysis | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| register | NO | | | **?** | **?** | **?** | **?** | **?** |
+| map | | | | | | | | |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| \* Derived pointers only pose a hasard to copying collections. |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+| **?** denotes a feature which could be utilized if available. |
++------------+------+--------+----------+-------+---------+-------------+----------+------------+
+
+To be clear, the collection techniques above are defined as:
+
+Shadow Stack
+ The mutator carefully maintains a linked list of stack roots.
+
+Reference Counting
+ The mutator maintains a reference count for each object and frees an object
+ when its count falls to zero.
+
+Mark-Sweep
+ When the heap is exhausted, the collector marks reachable objects starting
+ from the roots, then deallocates unreachable objects in a sweep phase.
+
+Copying
+ As reachability analysis proceeds, the collector copies objects from one heap
+ area to another, compacting them in the process. Copying collectors enable
+ highly efficient "bump pointer" allocation and can improve locality of
+ reference.
+
+Incremental
+ (Including generational collectors.) Incremental collectors generally have all
+ the properties of a copying collector (regardless of whether the mature heap
+ is compacting), but bring the added complexity of requiring write barriers.
+
+Threaded
+ Denotes a multithreaded mutator; the collector must still stop the mutator
+ ("stop the world") before beginning reachability analysis. Stopping a
+ multithreaded mutator is a complicated problem. It generally requires highly
+ platform-specific code in the runtime, and the production of carefully
+ designed machine code at safe points.
+
+Concurrent
+ In this technique, the mutator and the collector run concurrently, with the
+ goal of eliminating pause times. In a *cooperative* collector, the mutator
+ further aids with collection should a pause occur, allowing collection to take
+ advantage of multiprocessor hosts. The "stop the world" problem of threaded
+ collectors is generally still present to a limited extent. Sophisticated
+ marking algorithms are necessary. Read barriers may be necessary.
+
+As the matrix indicates, LLVM's garbage collection infrastructure is already
+suitable for a wide variety of collectors, but does not currently extend to
+multithreaded programs. This will be added in the future as there is
+interest.
+
+.. _stack-map:
+
+Computing stack maps
+--------------------
+
+LLVM automatically computes a stack map. One of the most important features
+of a ``GCStrategy`` is to compile this information into the executable in
+the binary representation expected by the runtime library.
+
+The stack map consists of the location and identity of each GC root in the
+each function in the module. For each root:
+
+* ``RootNum``: The index of the root.
+
+* ``StackOffset``: The offset of the object relative to the frame pointer.
+
+* ``RootMetadata``: The value passed as the ``%metadata`` parameter to the
+ ``@llvm.gcroot`` intrinsic.
+
+Also, for the function as a whole:
+
+* ``getFrameSize()``: The overall size of the function's initial stack frame,
+ not accounting for any dynamic allocation.
+
+* ``roots_size()``: The count of roots in the function.
+
+To access the stack map, use ``GCFunctionMetadata::roots_begin()`` and
+-``end()`` from the :ref:`GCMetadataPrinter <assembly>`:
+
+.. code-block:: c++
+
+ for (iterator I = begin(), E = end(); I != E; ++I) {
+ GCFunctionInfo *FI = *I;
+ unsigned FrameSize = FI->getFrameSize();
+ size_t RootCount = FI->roots_size();
+
+ for (GCFunctionInfo::roots_iterator RI = FI->roots_begin(),
+ RE = FI->roots_end();
+ RI != RE; ++RI) {
+ int RootNum = RI->Num;
+ int RootStackOffset = RI->StackOffset;
+ Constant *RootMetadata = RI->Metadata;
+ }
+ }
+
+If the ``llvm.gcroot`` intrinsic is eliminated before code generation by a
+custom lowering pass, LLVM will compute an empty stack map. This may be useful
+for collector plugins which implement reference counting or a shadow stack.
+
+.. _init-roots:
+
+Initializing roots to null: ``InitRoots``
+-----------------------------------------
+
+.. code-block:: c++
+
+ MyGC::MyGC() {
+ InitRoots = true;
+ }
+
+When set, LLVM will automatically initialize each root to ``null`` upon entry to
+the function. This prevents the GC's sweep phase from visiting uninitialized
+pointers, which will almost certainly cause it to crash. This initialization
+occurs before custom lowering, so the two may be used together.
+
+Since LLVM does not yet compute liveness information, there is no means of
+distinguishing an uninitialized stack root from an initialized one. Therefore,
+this feature should be used by all GC plugins. It is enabled by default.
+
+Custom lowering of intrinsics: ``CustomRoots``, ``CustomReadBarriers``, and ``CustomWriteBarriers``
+---------------------------------------------------------------------------------------------------
+
+For GCs which use barriers or unusual treatment of stack roots, these flags
+allow the collector to perform arbitrary transformations of the LLVM IR:
+
+.. code-block:: c++
+
+ class MyGC : public GCStrategy {
+ public:
+ MyGC() {
+ CustomRoots = true;
+ CustomReadBarriers = true;
+ CustomWriteBarriers = true;
+ }
+
+ virtual bool initializeCustomLowering(Module &M);
+ virtual bool performCustomLowering(Function &F);
+ };
+
+If any of these flags are set, then LLVM suppresses its default lowering for the
+corresponding intrinsics and instead calls ``performCustomLowering``.
+
+LLVM's default action for each intrinsic is as follows:
+
+* ``llvm.gcroot``: Leave it alone. The code generator must see it or the stack
+ map will not be computed.
+
+* ``llvm.gcread``: Substitute a ``load`` instruction.
+
+* ``llvm.gcwrite``: Substitute a ``store`` instruction.
+
+If ``CustomReadBarriers`` or ``CustomWriteBarriers`` are specified, then
+``performCustomLowering`` **must** eliminate the corresponding barriers.
+
+``performCustomLowering`` must comply with the same restrictions as
+:ref:`FunctionPass::runOnFunction <writing-an-llvm-pass-runOnFunction>`
+Likewise, ``initializeCustomLowering`` has the same semantics as
+:ref:`Pass::doInitialization(Module&)
+<writing-an-llvm-pass-doInitialization-mod>`
+
+The following can be used as a template:
+
+.. code-block:: c++
+
+ #include "llvm/IR/Module.h"
+ #include "llvm/IR/IntrinsicInst.h"
+
+ bool MyGC::initializeCustomLowering(Module &M) {
+ return false;
+ }
+
+ bool MyGC::performCustomLowering(Function &F) {
+ bool MadeChange = false;
+
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; )
+ if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++))
+ if (Function *F = CI->getCalledFunction())
+ switch (F->getIntrinsicID()) {
+ case Intrinsic::gcwrite:
+ // Handle llvm.gcwrite.
+ CI->eraseFromParent();
+ MadeChange = true;
+ break;
+ case Intrinsic::gcread:
+ // Handle llvm.gcread.
+ CI->eraseFromParent();
+ MadeChange = true;
+ break;
+ case Intrinsic::gcroot:
+ // Handle llvm.gcroot.
+ CI->eraseFromParent();
+ MadeChange = true;
+ break;
+ }
+
+ return MadeChange;
+ }
+
+.. _safe-points:
+
+Generating safe points: ``NeededSafePoints``
+--------------------------------------------
+
+LLVM can compute four kinds of safe points:
+
+.. code-block:: c++
+
+ namespace GC {
+ /// PointKind - The type of a collector-safe point.
+ ///
+ enum PointKind {
+ Loop, //< Instr is a loop (backwards branch).
+ Return, //< Instr is a return instruction.
+ PreCall, //< Instr is a call instruction.
+ PostCall //< Instr is the return address of a call.
+ };
+ }
+
+A collector can request any combination of the four by setting the
+``NeededSafePoints`` mask:
+
+.. code-block:: c++
+
+ MyGC::MyGC() {
+ NeededSafePoints = 1 << GC::Loop
+ | 1 << GC::Return
+ | 1 << GC::PreCall
+ | 1 << GC::PostCall;
+ }
+
+It can then use the following routines to access safe points.
+
+.. code-block:: c++
+
+ for (iterator I = begin(), E = end(); I != E; ++I) {
+ GCFunctionInfo *MD = *I;
+ size_t PointCount = MD->size();
+
+ for (GCFunctionInfo::iterator PI = MD->begin(),
+ PE = MD->end(); PI != PE; ++PI) {
+ GC::PointKind PointKind = PI->Kind;
+ unsigned PointNum = PI->Num;
+ }
+ }
+
+Almost every collector requires ``PostCall`` safe points, since these correspond
+to the moments when the function is suspended during a call to a subroutine.
+
+Threaded programs generally require ``Loop`` safe points to guarantee that the
+application will reach a safe point within a bounded amount of time, even if it
+is executing a long-running loop which contains no function calls.
+
+Threaded collectors may also require ``Return`` and ``PreCall`` safe points to
+implement "stop the world" techniques using self-modifying code, where it is
+important that the program not exit the function without reaching a safe point
+(because only the topmost function has been patched).
+
+.. _assembly:
+
+Emitting assembly code: ``GCMetadataPrinter``
+---------------------------------------------
+
+LLVM allows a plugin to print arbitrary assembly code before and after the rest
+of a module's assembly code. At the end of the module, the GC can compile the
+LLVM stack map into assembly code. (At the beginning, this information is not
+yet computed.)
+
+Since AsmWriter and CodeGen are separate components of LLVM, a separate abstract
+base class and registry is provided for printing assembly code, the
+``GCMetadaPrinter`` and ``GCMetadataPrinterRegistry``. The AsmWriter will look
+for such a subclass if the ``GCStrategy`` sets ``UsesMetadata``:
+
+.. code-block:: c++
+
+ MyGC::MyGC() {
+ UsesMetadata = true;
+ }
+
+This separation allows JIT-only clients to be smaller.
+
+Note that LLVM does not currently have analogous APIs to support code generation
+in the JIT, nor using the object writers.
+
+.. code-block:: c++
+
+ // lib/MyGC/MyGCPrinter.cpp - Example LLVM GC printer
+
+ #include "llvm/CodeGen/GCMetadataPrinter.h"
+ #include "llvm/Support/Compiler.h"
+
+ using namespace llvm;
+
+ namespace {
+ class LLVM_LIBRARY_VISIBILITY MyGCPrinter : public GCMetadataPrinter {
+ public:
+ virtual void beginAssembly(AsmPrinter &AP);
+
+ virtual void finishAssembly(AsmPrinter &AP);
+ };
+
+ GCMetadataPrinterRegistry::Add<MyGCPrinter>
+ X("mygc", "My bespoke garbage collector.");
+ }
+
+The collector should use ``AsmPrinter`` to print portable assembly code. The
+collector itself contains the stack map for the entire module, and may access
+the ``GCFunctionInfo`` using its own ``begin()`` and ``end()`` methods. Here's
+a realistic example:
+
+.. code-block:: c++
+
+ #include "llvm/CodeGen/AsmPrinter.h"
+ #include "llvm/IR/Function.h"
+ #include "llvm/IR/DataLayout.h"
+ #include "llvm/Target/TargetAsmInfo.h"
+ #include "llvm/Target/TargetMachine.h"
+
+ void MyGCPrinter::beginAssembly(AsmPrinter &AP) {
+ // Nothing to do.
+ }
+
+ void MyGCPrinter::finishAssembly(AsmPrinter &AP) {
+ MCStreamer &OS = AP.OutStreamer;
+ unsigned IntPtrSize = AP.TM.getSubtargetImpl()->getDataLayout()->getPointerSize();
+
+ // Put this in the data section.
+ OS.SwitchSection(AP.getObjFileLowering().getDataSection());
+
+ // For each function...
+ for (iterator FI = begin(), FE = end(); FI != FE; ++FI) {
+ GCFunctionInfo &MD = **FI;
+
+ // A compact GC layout. Emit this data structure:
+ //
+ // struct {
+ // int32_t PointCount;
+ // void *SafePointAddress[PointCount];
+ // int32_t StackFrameSize; // in words
+ // int32_t StackArity;
+ // int32_t LiveCount;
+ // int32_t LiveOffsets[LiveCount];
+ // } __gcmap_<FUNCTIONNAME>;
+
+ // Align to address width.
+ AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
+
+ // Emit PointCount.
+ OS.AddComment("safe point count");
+ AP.EmitInt32(MD.size());
+
+ // And each safe point...
+ for (GCFunctionInfo::iterator PI = MD.begin(),
+ PE = MD.end(); PI != PE; ++PI) {
+ // Emit the address of the safe point.
+ OS.AddComment("safe point address");
+ MCSymbol *Label = PI->Label;
+ AP.EmitLabelPlusOffset(Label/*Hi*/, 0/*Offset*/, 4/*Size*/);
+ }
+
+ // Stack information never change in safe points! Only print info from the
+ // first call-site.
+ GCFunctionInfo::iterator PI = MD.begin();
+
+ // Emit the stack frame size.
+ OS.AddComment("stack frame size (in words)");
+ AP.EmitInt32(MD.getFrameSize() / IntPtrSize);
+
+ // Emit stack arity, i.e. the number of stacked arguments.
+ unsigned RegisteredArgs = IntPtrSize == 4 ? 5 : 6;
+ unsigned StackArity = MD.getFunction().arg_size() > RegisteredArgs ?
+ MD.getFunction().arg_size() - RegisteredArgs : 0;
+ OS.AddComment("stack arity");
+ AP.EmitInt32(StackArity);
+
+ // Emit the number of live roots in the function.
+ OS.AddComment("live root count");
+ AP.EmitInt32(MD.live_size(PI));
+
+ // And for each live root...
+ for (GCFunctionInfo::live_iterator LI = MD.live_begin(PI),
+ LE = MD.live_end(PI);
+ LI != LE; ++LI) {
+ // Emit live root's offset within the stack frame.
+ OS.AddComment("stack index (offset / wordsize)");
+ AP.EmitInt32(LI->StackOffset);
+ }
+ }
+ }
+
+References
+==========
+
+.. _appel89:
+
+[Appel89] Runtime Tags Aren't Necessary. Andrew W. Appel. Lisp and Symbolic
+Computation 19(7):703-705, July 1989.
+
+.. _goldberg91:
+
+[Goldberg91] Tag-free garbage collection for strongly typed programming
+languages. Benjamin Goldberg. ACM SIGPLAN PLDI'91.
+
+.. _tolmach94:
+
+[Tolmach94] Tag-free garbage collection using explicit type parameters. Andrew
+Tolmach. Proceedings of the 1994 ACM conference on LISP and functional
+programming.
+
+.. _henderson02:
+
+[Henderson2002] `Accurate Garbage Collection in an Uncooperative Environment
+<http://citeseer.ist.psu.edu/henderson02accurate.html>`__
Added: www-releases/trunk/3.6.2/docs/_sources/GetElementPtr.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/GetElementPtr.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/GetElementPtr.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/GetElementPtr.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,536 @@
+=======================================
+The Often Misunderstood GEP Instruction
+=======================================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+This document seeks to dispel the mystery and confusion surrounding LLVM's
+`GetElementPtr <LangRef.html#i_getelementptr>`_ (GEP) instruction. Questions
+about the wily GEP instruction are probably the most frequently occurring
+questions once a developer gets down to coding with LLVM. Here we lay out the
+sources of confusion and show that the GEP instruction is really quite simple.
+
+Address Computation
+===================
+
+When people are first confronted with the GEP instruction, they tend to relate
+it to known concepts from other programming paradigms, most notably C array
+indexing and field selection. GEP closely resembles C array indexing and field
+selection, however it is a little different and this leads to the following
+questions.
+
+What is the first index of the GEP instruction?
+-----------------------------------------------
+
+Quick answer: The index stepping through the first operand.
+
+The confusion with the first index usually arises from thinking about the
+GetElementPtr instruction as if it was a C index operator. They aren't the
+same. For example, when we write, in "C":
+
+.. code-block:: c++
+
+ AType *Foo;
+ ...
+ X = &Foo->F;
+
+it is natural to think that there is only one index, the selection of the field
+``F``. However, in this example, ``Foo`` is a pointer. That pointer
+must be indexed explicitly in LLVM. C, on the other hand, indices through it
+transparently. To arrive at the same address location as the C code, you would
+provide the GEP instruction with two index operands. The first operand indexes
+through the pointer; the second operand indexes the field ``F`` of the
+structure, just as if you wrote:
+
+.. code-block:: c++
+
+ X = &Foo[0].F;
+
+Sometimes this question gets rephrased as:
+
+.. _GEP index through first pointer:
+
+ *Why is it okay to index through the first pointer, but subsequent pointers
+ won't be dereferenced?*
+
+The answer is simply because memory does not have to be accessed to perform the
+computation. The first operand to the GEP instruction must be a value of a
+pointer type. The value of the pointer is provided directly to the GEP
+instruction as an operand without any need for accessing memory. It must,
+therefore be indexed and requires an index operand. Consider this example:
+
+.. code-block:: c++
+
+ struct munger_struct {
+ int f1;
+ int f2;
+ };
+ void munge(struct munger_struct *P) {
+ P[0].f1 = P[1].f1 + P[2].f2;
+ }
+ ...
+ munger_struct Array[3];
+ ...
+ munge(Array);
+
+In this "C" example, the front end compiler (Clang) will generate three GEP
+instructions for the three indices through "P" in the assignment statement. The
+function argument ``P`` will be the first operand of each of these GEP
+instructions. The second operand indexes through that pointer. The third
+operand will be the field offset into the ``struct munger_struct`` type, for
+either the ``f1`` or ``f2`` field. So, in LLVM assembly the ``munge`` function
+looks like:
+
+.. code-block:: llvm
+
+ void %munge(%struct.munger_struct* %P) {
+ entry:
+ %tmp = getelementptr %struct.munger_struct* %P, i32 1, i32 0
+ %tmp = load i32* %tmp
+ %tmp6 = getelementptr %struct.munger_struct* %P, i32 2, i32 1
+ %tmp7 = load i32* %tmp6
+ %tmp8 = add i32 %tmp7, %tmp
+ %tmp9 = getelementptr %struct.munger_struct* %P, i32 0, i32 0
+ store i32 %tmp8, i32* %tmp9
+ ret void
+ }
+
+In each case the first operand is the pointer through which the GEP instruction
+starts. The same is true whether the first operand is an argument, allocated
+memory, or a global variable.
+
+To make this clear, let's consider a more obtuse example:
+
+.. code-block:: llvm
+
+ %MyVar = uninitialized global i32
+ ...
+ %idx1 = getelementptr i32* %MyVar, i64 0
+ %idx2 = getelementptr i32* %MyVar, i64 1
+ %idx3 = getelementptr i32* %MyVar, i64 2
+
+These GEP instructions are simply making address computations from the base
+address of ``MyVar``. They compute, as follows (using C syntax):
+
+.. code-block:: c++
+
+ idx1 = (char*) &MyVar + 0
+ idx2 = (char*) &MyVar + 4
+ idx3 = (char*) &MyVar + 8
+
+Since the type ``i32`` is known to be four bytes long, the indices 0, 1 and 2
+translate into memory offsets of 0, 4, and 8, respectively. No memory is
+accessed to make these computations because the address of ``%MyVar`` is passed
+directly to the GEP instructions.
+
+The obtuse part of this example is in the cases of ``%idx2`` and ``%idx3``. They
+result in the computation of addresses that point to memory past the end of the
+``%MyVar`` global, which is only one ``i32`` long, not three ``i32``\s long.
+While this is legal in LLVM, it is inadvisable because any load or store with
+the pointer that results from these GEP instructions would produce undefined
+results.
+
+Why is the extra 0 index required?
+----------------------------------
+
+Quick answer: there are no superfluous indices.
+
+This question arises most often when the GEP instruction is applied to a global
+variable which is always a pointer type. For example, consider this:
+
+.. code-block:: llvm
+
+ %MyStruct = uninitialized global { float*, i32 }
+ ...
+ %idx = getelementptr { float*, i32 }* %MyStruct, i64 0, i32 1
+
+The GEP above yields an ``i32*`` by indexing the ``i32`` typed field of the
+structure ``%MyStruct``. When people first look at it, they wonder why the ``i64
+0`` index is needed. However, a closer inspection of how globals and GEPs work
+reveals the need. Becoming aware of the following facts will dispel the
+confusion:
+
+#. The type of ``%MyStruct`` is *not* ``{ float*, i32 }`` but rather ``{ float*,
+ i32 }*``. That is, ``%MyStruct`` is a pointer to a structure containing a
+ pointer to a ``float`` and an ``i32``.
+
+#. Point #1 is evidenced by noticing the type of the first operand of the GEP
+ instruction (``%MyStruct``) which is ``{ float*, i32 }*``.
+
+#. The first index, ``i64 0`` is required to step over the global variable
+ ``%MyStruct``. Since the first argument to the GEP instruction must always
+ be a value of pointer type, the first index steps through that pointer. A
+ value of 0 means 0 elements offset from that pointer.
+
+#. The second index, ``i32 1`` selects the second field of the structure (the
+ ``i32``).
+
+What is dereferenced by GEP?
+----------------------------
+
+Quick answer: nothing.
+
+The GetElementPtr instruction dereferences nothing. That is, it doesn't access
+memory in any way. That's what the Load and Store instructions are for. GEP is
+only involved in the computation of addresses. For example, consider this:
+
+.. code-block:: llvm
+
+ %MyVar = uninitialized global { [40 x i32 ]* }
+ ...
+ %idx = getelementptr { [40 x i32]* }* %MyVar, i64 0, i32 0, i64 0, i64 17
+
+In this example, we have a global variable, ``%MyVar`` that is a pointer to a
+structure containing a pointer to an array of 40 ints. The GEP instruction seems
+to be accessing the 18th integer of the structure's array of ints. However, this
+is actually an illegal GEP instruction. It won't compile. The reason is that the
+pointer in the structure *must* be dereferenced in order to index into the
+array of 40 ints. Since the GEP instruction never accesses memory, it is
+illegal.
+
+In order to access the 18th integer in the array, you would need to do the
+following:
+
+.. code-block:: llvm
+
+ %idx = getelementptr { [40 x i32]* }* %, i64 0, i32 0
+ %arr = load [40 x i32]** %idx
+ %idx = getelementptr [40 x i32]* %arr, i64 0, i64 17
+
+In this case, we have to load the pointer in the structure with a load
+instruction before we can index into the array. If the example was changed to:
+
+.. code-block:: llvm
+
+ %MyVar = uninitialized global { [40 x i32 ] }
+ ...
+ %idx = getelementptr { [40 x i32] }*, i64 0, i32 0, i64 17
+
+then everything works fine. In this case, the structure does not contain a
+pointer and the GEP instruction can index through the global variable, into the
+first field of the structure and access the 18th ``i32`` in the array there.
+
+Why don't GEP x,0,0,1 and GEP x,1 alias?
+----------------------------------------
+
+Quick Answer: They compute different address locations.
+
+If you look at the first indices in these GEP instructions you find that they
+are different (0 and 1), therefore the address computation diverges with that
+index. Consider this example:
+
+.. code-block:: llvm
+
+ %MyVar = global { [10 x i32 ] }
+ %idx1 = getelementptr { [10 x i32 ] }* %MyVar, i64 0, i32 0, i64 1
+ %idx2 = getelementptr { [10 x i32 ] }* %MyVar, i64 1
+
+In this example, ``idx1`` computes the address of the second integer in the
+array that is in the structure in ``%MyVar``, that is ``MyVar+4``. The type of
+``idx1`` is ``i32*``. However, ``idx2`` computes the address of *the next*
+structure after ``%MyVar``. The type of ``idx2`` is ``{ [10 x i32] }*`` and its
+value is equivalent to ``MyVar + 40`` because it indexes past the ten 4-byte
+integers in ``MyVar``. Obviously, in such a situation, the pointers don't
+alias.
+
+Why do GEP x,1,0,0 and GEP x,1 alias?
+-------------------------------------
+
+Quick Answer: They compute the same address location.
+
+These two GEP instructions will compute the same address because indexing
+through the 0th element does not change the address. However, it does change the
+type. Consider this example:
+
+.. code-block:: llvm
+
+ %MyVar = global { [10 x i32 ] }
+ %idx1 = getelementptr { [10 x i32 ] }* %MyVar, i64 1, i32 0, i64 0
+ %idx2 = getelementptr { [10 x i32 ] }* %MyVar, i64 1
+
+In this example, the value of ``%idx1`` is ``%MyVar+40`` and its type is
+``i32*``. The value of ``%idx2`` is also ``MyVar+40`` but its type is ``{ [10 x
+i32] }*``.
+
+Can GEP index into vector elements?
+-----------------------------------
+
+This hasn't always been forcefully disallowed, though it's not recommended. It
+leads to awkward special cases in the optimizers, and fundamental inconsistency
+in the IR. In the future, it will probably be outright disallowed.
+
+What effect do address spaces have on GEPs?
+-------------------------------------------
+
+None, except that the address space qualifier on the first operand pointer type
+always matches the address space qualifier on the result type.
+
+How is GEP different from ``ptrtoint``, arithmetic, and ``inttoptr``?
+---------------------------------------------------------------------
+
+It's very similar; there are only subtle differences.
+
+With ptrtoint, you have to pick an integer type. One approach is to pick i64;
+this is safe on everything LLVM supports (LLVM internally assumes pointers are
+never wider than 64 bits in many places), and the optimizer will actually narrow
+the i64 arithmetic down to the actual pointer size on targets which don't
+support 64-bit arithmetic in most cases. However, there are some cases where it
+doesn't do this. With GEP you can avoid this problem.
+
+Also, GEP carries additional pointer aliasing rules. It's invalid to take a GEP
+from one object, address into a different separately allocated object, and
+dereference it. IR producers (front-ends) must follow this rule, and consumers
+(optimizers, specifically alias analysis) benefit from being able to rely on
+it. See the `Rules`_ section for more information.
+
+And, GEP is more concise in common cases.
+
+However, for the underlying integer computation implied, there is no
+difference.
+
+
+I'm writing a backend for a target which needs custom lowering for GEP. How do I do this?
+-----------------------------------------------------------------------------------------
+
+You don't. The integer computation implied by a GEP is target-independent.
+Typically what you'll need to do is make your backend pattern-match expressions
+trees involving ADD, MUL, etc., which are what GEP is lowered into. This has the
+advantage of letting your code work correctly in more cases.
+
+GEP does use target-dependent parameters for the size and layout of data types,
+which targets can customize.
+
+If you require support for addressing units which are not 8 bits, you'll need to
+fix a lot of code in the backend, with GEP lowering being only a small piece of
+the overall picture.
+
+How does VLA addressing work with GEPs?
+---------------------------------------
+
+GEPs don't natively support VLAs. LLVM's type system is entirely static, and GEP
+address computations are guided by an LLVM type.
+
+VLA indices can be implemented as linearized indices. For example, an expression
+like ``X[a][b][c]``, must be effectively lowered into a form like
+``X[a*m+b*n+c]``, so that it appears to the GEP as a single-dimensional array
+reference.
+
+This means if you want to write an analysis which understands array indices and
+you want to support VLAs, your code will have to be prepared to reverse-engineer
+the linearization. One way to solve this problem is to use the ScalarEvolution
+library, which always presents VLA and non-VLA indexing in the same manner.
+
+.. _Rules:
+
+Rules
+=====
+
+What happens if an array index is out of bounds?
+------------------------------------------------
+
+There are two senses in which an array index can be out of bounds.
+
+First, there's the array type which comes from the (static) type of the first
+operand to the GEP. Indices greater than the number of elements in the
+corresponding static array type are valid. There is no problem with out of
+bounds indices in this sense. Indexing into an array only depends on the size of
+the array element, not the number of elements.
+
+A common example of how this is used is arrays where the size is not known.
+It's common to use array types with zero length to represent these. The fact
+that the static type says there are zero elements is irrelevant; it's perfectly
+valid to compute arbitrary element indices, as the computation only depends on
+the size of the array element, not the number of elements. Note that zero-sized
+arrays are not a special case here.
+
+This sense is unconnected with ``inbounds`` keyword. The ``inbounds`` keyword is
+designed to describe low-level pointer arithmetic overflow conditions, rather
+than high-level array indexing rules.
+
+Analysis passes which wish to understand array indexing should not assume that
+the static array type bounds are respected.
+
+The second sense of being out of bounds is computing an address that's beyond
+the actual underlying allocated object.
+
+With the ``inbounds`` keyword, the result value of the GEP is undefined if the
+address is outside the actual underlying allocated object and not the address
+one-past-the-end.
+
+Without the ``inbounds`` keyword, there are no restrictions on computing
+out-of-bounds addresses. Obviously, performing a load or a store requires an
+address of allocated and sufficiently aligned memory. But the GEP itself is only
+concerned with computing addresses.
+
+Can array indices be negative?
+------------------------------
+
+Yes. This is basically a special case of array indices being out of bounds.
+
+Can I compare two values computed with GEPs?
+--------------------------------------------
+
+Yes. If both addresses are within the same allocated object, or
+one-past-the-end, you'll get the comparison result you expect. If either is
+outside of it, integer arithmetic wrapping may occur, so the comparison may not
+be meaningful.
+
+Can I do GEP with a different pointer type than the type of the underlying object?
+----------------------------------------------------------------------------------
+
+Yes. There are no restrictions on bitcasting a pointer value to an arbitrary
+pointer type. The types in a GEP serve only to define the parameters for the
+underlying integer computation. They need not correspond with the actual type of
+the underlying object.
+
+Furthermore, loads and stores don't have to use the same types as the type of
+the underlying object. Types in this context serve only to specify memory size
+and alignment. Beyond that there are merely a hint to the optimizer indicating
+how the value will likely be used.
+
+Can I cast an object's address to integer and add it to null?
+-------------------------------------------------------------
+
+You can compute an address that way, but if you use GEP to do the add, you can't
+use that pointer to actually access the object, unless the object is managed
+outside of LLVM.
+
+The underlying integer computation is sufficiently defined; null has a defined
+value --- zero --- and you can add whatever value you want to it.
+
+However, it's invalid to access (load from or store to) an LLVM-aware object
+with such a pointer. This includes ``GlobalVariables``, ``Allocas``, and objects
+pointed to by noalias pointers.
+
+If you really need this functionality, you can do the arithmetic with explicit
+integer instructions, and use inttoptr to convert the result to an address. Most
+of GEP's special aliasing rules do not apply to pointers computed from ptrtoint,
+arithmetic, and inttoptr sequences.
+
+Can I compute the distance between two objects, and add that value to one address to compute the other address?
+---------------------------------------------------------------------------------------------------------------
+
+As with arithmetic on null, you can use GEP to compute an address that way, but
+you can't use that pointer to actually access the object if you do, unless the
+object is managed outside of LLVM.
+
+Also as above, ptrtoint and inttoptr provide an alternative way to do this which
+do not have this restriction.
+
+Can I do type-based alias analysis on LLVM IR?
+----------------------------------------------
+
+You can't do type-based alias analysis using LLVM's built-in type system,
+because LLVM has no restrictions on mixing types in addressing, loads or stores.
+
+LLVM's type-based alias analysis pass uses metadata to describe a different type
+system (such as the C type system), and performs type-based aliasing on top of
+that. Further details are in the `language reference <LangRef.html#tbaa>`_.
+
+What happens if a GEP computation overflows?
+--------------------------------------------
+
+If the GEP lacks the ``inbounds`` keyword, the value is the result from
+evaluating the implied two's complement integer computation. However, since
+there's no guarantee of where an object will be allocated in the address space,
+such values have limited meaning.
+
+If the GEP has the ``inbounds`` keyword, the result value is undefined (a "trap
+value") if the GEP overflows (i.e. wraps around the end of the address space).
+
+As such, there are some ramifications of this for inbounds GEPs: scales implied
+by array/vector/pointer indices are always known to be "nsw" since they are
+signed values that are scaled by the element size. These values are also
+allowed to be negative (e.g. "``gep i32 *%P, i32 -1``") but the pointer itself
+is logically treated as an unsigned value. This means that GEPs have an
+asymmetric relation between the pointer base (which is treated as unsigned) and
+the offset applied to it (which is treated as signed). The result of the
+additions within the offset calculation cannot have signed overflow, but when
+applied to the base pointer, there can be signed overflow.
+
+How can I tell if my front-end is following the rules?
+------------------------------------------------------
+
+There is currently no checker for the getelementptr rules. Currently, the only
+way to do this is to manually check each place in your front-end where
+GetElementPtr operators are created.
+
+It's not possible to write a checker which could find all rule violations
+statically. It would be possible to write a checker which works by instrumenting
+the code with dynamic checks though. Alternatively, it would be possible to
+write a static checker which catches a subset of possible problems. However, no
+such checker exists today.
+
+Rationale
+=========
+
+Why is GEP designed this way?
+-----------------------------
+
+The design of GEP has the following goals, in rough unofficial order of
+priority:
+
+* Support C, C-like languages, and languages which can be conceptually lowered
+ into C (this covers a lot).
+
+* Support optimizations such as those that are common in C compilers. In
+ particular, GEP is a cornerstone of LLVM's `pointer aliasing
+ model <LangRef.html#pointeraliasing>`_.
+
+* Provide a consistent method for computing addresses so that address
+ computations don't need to be a part of load and store instructions in the IR.
+
+* Support non-C-like languages, to the extent that it doesn't interfere with
+ other goals.
+
+* Minimize target-specific information in the IR.
+
+Why do struct member indices always use ``i32``?
+------------------------------------------------
+
+The specific type i32 is probably just a historical artifact, however it's wide
+enough for all practical purposes, so there's been no need to change it. It
+doesn't necessarily imply i32 address arithmetic; it's just an identifier which
+identifies a field in a struct. Requiring that all struct indices be the same
+reduces the range of possibilities for cases where two GEPs are effectively the
+same but have distinct operand types.
+
+What's an uglygep?
+------------------
+
+Some LLVM optimizers operate on GEPs by internally lowering them into more
+primitive integer expressions, which allows them to be combined with other
+integer expressions and/or split into multiple separate integer expressions. If
+they've made non-trivial changes, translating back into LLVM IR can involve
+reverse-engineering the structure of the addressing in order to fit it into the
+static type of the original first operand. It isn't always possibly to fully
+reconstruct this structure; sometimes the underlying addressing doesn't
+correspond with the static type at all. In such cases the optimizer instead will
+emit a GEP with the base pointer casted to a simple address-unit pointer, using
+the name "uglygep". This isn't pretty, but it's just as valid, and it's
+sufficient to preserve the pointer aliasing guarantees that GEP provides.
+
+Summary
+=======
+
+In summary, here's some things to always remember about the GetElementPtr
+instruction:
+
+
+#. The GEP instruction never accesses memory, it only provides pointer
+ computations.
+
+#. The first operand to the GEP instruction is always a pointer and it must be
+ indexed.
+
+#. There are no superfluous indices for the GEP instruction.
+
+#. Trailing zero indices are superfluous for pointer aliasing, but not for the
+ types of the pointers.
+
+#. Leading zero indices are not superfluous for pointer aliasing nor the types
+ of the pointers.
Added: www-releases/trunk/3.6.2/docs/_sources/GettingStarted.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/GettingStarted.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/GettingStarted.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/GettingStarted.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,1341 @@
+====================================
+Getting Started with the LLVM System
+====================================
+
+.. contents::
+ :local:
+
+Overview
+========
+
+Welcome to LLVM! In order to get started, you first need to know some basic
+information.
+
+First, LLVM comes in three pieces. The first piece is the LLVM suite. This
+contains all of the tools, libraries, and header files needed to use LLVM. It
+contains an assembler, disassembler, bitcode analyzer and bitcode optimizer. It
+also contains basic regression tests that can be used to test the LLVM tools and
+the Clang front end.
+
+The second piece is the `Clang <http://clang.llvm.org/>`_ front end. This
+component compiles C, C++, Objective C, and Objective C++ code into LLVM
+bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the
+LLVM tools from the LLVM suite.
+
+There is a third, optional piece called Test Suite. It is a suite of programs
+with a testing harness that can be used to further test LLVM's functionality
+and performance.
+
+Getting Started Quickly (A Summary)
+===================================
+
+The LLVM Getting Started documentation may be out of date. So, the `Clang
+Getting Started <http://clang.llvm.org/get_started.html>`_ page might also be a
+good place to start.
+
+Here's the short story for getting up and running quickly with LLVM:
+
+#. Read the documentation.
+#. Read the documentation.
+#. Remember that you were warned twice about reading the documentation.
+#. Checkout LLVM:
+
+ * ``cd where-you-want-llvm-to-live``
+ * ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
+
+#. Checkout Clang:
+
+ * ``cd where-you-want-llvm-to-live``
+ * ``cd llvm/tools``
+ * ``svn co http://llvm.org/svn/llvm-project/cfe/trunk clang``
+
+#. Checkout Compiler-RT:
+
+ * ``cd where-you-want-llvm-to-live``
+ * ``cd llvm/projects``
+ * ``svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk compiler-rt``
+
+#. Get the Test Suite Source Code **[Optional]**
+
+ * ``cd where-you-want-llvm-to-live``
+ * ``cd llvm/projects``
+ * ``svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite``
+
+#. Configure and build LLVM and Clang:
+
+ * ``cd where-you-want-to-build-llvm``
+ * ``mkdir build`` (for building without polluting the source dir)
+ * ``cd build``
+ * ``../llvm/configure [options]``
+ Some common options:
+
+ * ``--prefix=directory`` --- Specify for *directory* the full pathname of
+ where you want the LLVM tools and libraries to be installed (default
+ ``/usr/local``).
+
+ * ``--enable-optimized`` --- Compile with optimizations enabled (default
+ is NO).
+
+ * ``--enable-assertions`` --- Compile with assertion checks enabled
+ (default is YES).
+
+ * ``make [-j]`` --- The ``-j`` specifies the number of jobs (commands) to run
+ simultaneously. This builds both LLVM and Clang for Debug+Asserts mode.
+ The ``--enable-optimized`` configure option is used to specify a Release
+ build.
+
+ * ``make check-all`` --- This run the regression tests to ensure everything
+ is in working order.
+
+ * It is also possible to use `CMake <CMake.html>`_ instead of the makefiles.
+ With CMake it is possible to generate project files for several IDEs:
+ Xcode, Eclipse CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks
+ generator), KDevelop3.
+
+ * If you get an "internal compiler error (ICE)" or test failures, see
+ `below`.
+
+Consult the `Getting Started with LLVM`_ section for detailed information on
+configuring and compiling LLVM. See `Setting Up Your Environment`_ for tips
+that simplify working with the Clang front end and LLVM tools. Go to `Program
+Layout`_ to learn about the layout of the source code tree.
+
+Requirements
+============
+
+Before you begin to use the LLVM system, review the requirements given below.
+This may save you some trouble by knowing ahead of time what hardware and
+software you will need.
+
+Hardware
+--------
+
+LLVM is known to work on the following host platforms:
+
+================== ===================== =============
+OS Arch Compilers
+================== ===================== =============
+Linux x86\ :sup:`1` GCC, Clang
+Linux amd64 GCC, Clang
+Linux ARM\ :sup:`4` GCC, Clang
+Linux PowerPC GCC, Clang
+Solaris V9 (Ultrasparc) GCC
+FreeBSD x86\ :sup:`1` GCC, Clang
+FreeBSD amd64 GCC, Clang
+MacOS X\ :sup:`2` PowerPC GCC
+MacOS X x86 GCC, Clang
+Cygwin/Win32 x86\ :sup:`1, 3` GCC
+Windows x86\ :sup:`1` Visual Studio
+Windows x64 x86-64 Visual Studio
+================== ===================== =============
+
+.. note::
+
+ #. Code generation supported for Pentium processors and up
+ #. Code generation supported for 32-bit ABI only
+ #. To use LLVM modules on Win32-based system, you may configure LLVM
+ with ``--enable-shared``.
+ #. MCJIT not working well pre-v7, old JIT engine not supported any more.
+
+Note that you will need about 1-3 GB of space for a full LLVM build in Debug
+mode, depending on the system (it is so large because of all the debugging
+information and the fact that the libraries are statically linked into multiple
+tools). If you do not need many of the tools and you are space-conscious, you
+can pass ``ONLY_TOOLS="tools you need"`` to make. The Release build requires
+considerably less space.
+
+The LLVM suite *may* compile on other platforms, but it is not guaranteed to do
+so. If compilation is successful, the LLVM utilities should be able to
+assemble, disassemble, analyze, and optimize LLVM bitcode. Code generation
+should work as well, although the generated native code may not work on your
+platform.
+
+Software
+--------
+
+Compiling LLVM requires that you have several software packages installed. The
+table below lists those required packages. The Package column is the usual name
+for the software package that LLVM depends on. The Version column provides
+"known to work" versions of the package. The Notes column describes how LLVM
+uses the package and provides other details.
+
+=========================================================== ============ ==========================================
+Package Version Notes
+=========================================================== ============ ==========================================
+`GNU Make <http://savannah.gnu.org/projects/make>`_ 3.79, 3.79.1 Makefile/build processor
+`GCC <http://gcc.gnu.org/>`_ >=4.7.0 C/C++ compiler\ :sup:`1`
+`python <http://www.python.org/>`_ >=2.7 Automated test suite\ :sup:`2`
+`GNU M4 <http://savannah.gnu.org/projects/m4>`_ 1.4 Macro processor for configuration\ :sup:`3`
+`GNU Autoconf <http://www.gnu.org/software/autoconf/>`_ 2.60 Configuration script builder\ :sup:`3`
+`GNU Automake <http://www.gnu.org/software/automake/>`_ 1.9.6 aclocal macro generator\ :sup:`3`
+`libtool <http://savannah.gnu.org/projects/libtool>`_ 1.5.22 Shared library manager\ :sup:`3`
+`zlib <http://zlib.net>`_ >=1.2.3.4 Compression library\ :sup:`4`
+=========================================================== ============ ==========================================
+
+.. note::
+
+ #. Only the C and C++ languages are needed so there's no need to build the
+ other languages for LLVM's purposes. See `below` for specific version
+ info.
+ #. Only needed if you want to run the automated test suite in the
+ ``llvm/test`` directory.
+ #. If you want to make changes to the configure scripts, you will need GNU
+ autoconf (2.60), and consequently, GNU M4 (version 1.4 or higher). You
+ will also need automake (1.9.6). We only use aclocal from that package.
+ #. Optional, adds compression / uncompression capabilities to selected LLVM
+ tools.
+
+Additionally, your compilation host is expected to have the usual plethora of
+Unix utilities. Specifically:
+
+* **ar** --- archive library builder
+* **bzip2** --- bzip2 command for distribution generation
+* **bunzip2** --- bunzip2 command for distribution checking
+* **chmod** --- change permissions on a file
+* **cat** --- output concatenation utility
+* **cp** --- copy files
+* **date** --- print the current date/time
+* **echo** --- print to standard output
+* **egrep** --- extended regular expression search utility
+* **find** --- find files/dirs in a file system
+* **grep** --- regular expression search utility
+* **gzip** --- gzip command for distribution generation
+* **gunzip** --- gunzip command for distribution checking
+* **install** --- install directories/files
+* **mkdir** --- create a directory
+* **mv** --- move (rename) files
+* **ranlib** --- symbol table builder for archive libraries
+* **rm** --- remove (delete) files and directories
+* **sed** --- stream editor for transforming output
+* **sh** --- Bourne shell for make build scripts
+* **tar** --- tape archive for distribution generation
+* **test** --- test things in file system
+* **unzip** --- unzip command for distribution checking
+* **zip** --- zip command for distribution generation
+
+.. _below:
+.. _check here:
+
+Host C++ Toolchain, both Compiler and Standard Library
+------------------------------------------------------
+
+LLVM is very demanding of the host C++ compiler, and as such tends to expose
+bugs in the compiler. We are also planning to follow improvements and
+developments in the C++ language and library reasonably closely. As such, we
+require a modern host C++ toolchain, both compiler and standard library, in
+order to build LLVM.
+
+For the most popular host toolchains we check for specific minimum versions in
+our build systems:
+
+* Clang 3.1
+* GCC 4.7
+* Visual Studio 2012
+
+Anything older than these toolchains *may* work, but will require forcing the
+build system with a special option and is not really a supported host platform.
+Also note that older versions of these compilers have often crashed or
+miscompiled LLVM.
+
+For less widely used host toolchains such as ICC or xlC, be aware that a very
+recent version may be required to support all of the C++ features used in LLVM.
+
+We track certain versions of software that are *known* to fail when used as
+part of the host toolchain. These even include linkers at times.
+
+**GCC 4.6.3 on ARM**: Miscompiles ``llvm-readobj`` at ``-O3``. A test failure
+in ``test/Object/readobj-shared-object.test`` is one symptom of the problem.
+
+**GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
+warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
+defined in a discarded section. You can safely ignore these messages as they are
+erroneous and the linkage is correct. These messages disappear using ld 2.17.
+
+**GNU binutils 2.17**: Binutils 2.17 contains `a bug
+<http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
+times (minutes instead of seconds) when building LLVM. We recommend upgrading
+to a newer version (2.17.50.0.4 or later).
+
+**GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
+<http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
+intermittent failures when building LLVM with position independent code. The
+symptom is an error about cyclic dependencies. We recommend upgrading to a
+newer version of Gold.
+
+**Clang 3.0 with libstdc++ 4.7.x**: a few Linux distributions (Ubuntu 12.10,
+Fedora 17) have both Clang 3.0 and libstdc++ 4.7 in their repositories. Clang
+3.0 does not implement a few builtins that are used in this library. We
+recommend using the system GCC to compile LLVM and Clang in this case.
+
+**Clang 3.0 on Mageia 2**. There's a packaging issue: Clang can not find at
+least some (``cxxabi.h``) libstdc++ headers.
+
+**Clang in C++11 mode and libstdc++ 4.7.2**. This version of libstdc++
+contained `a bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53841>`__ which
+causes Clang to refuse to compile condition_variable header file. At the time
+of writing, this breaks LLD build.
+
+Getting a Modern Host C++ Toolchain
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This section mostly applies to Linux and older BSDs. On Mac OS X, you should
+have a sufficiently modern Xcode, or you will likely need to upgrade until you
+do. On Windows, just use Visual Studio 2012 as the host compiler, it is
+explicitly supported and widely available. FreeBSD 10.0 and newer have a modern
+Clang as the system compiler.
+
+However, some Linux distributions and some other or older BSDs sometimes have
+extremely old versions of GCC. These steps attempt to help you upgrade you
+compiler even on such a system. However, if at all possible, we encourage you
+to use a recent version of a distribution with a modern system compiler that
+meets these requirements. Note that it is tempting to to install a prior
+version of Clang and libc++ to be the host compiler, however libc++ was not
+well tested or set up to build on Linux until relatively recently. As
+a consequence, this guide suggests just using libstdc++ and a modern GCC as the
+initial host in a bootstrap, and then using Clang (and potentially libc++).
+
+The first step is to get a recent GCC toolchain installed. The most common
+distribution on which users have struggled with the version requirements is
+Ubuntu Precise, 12.04 LTS. For this distribution, one easy option is to install
+the `toolchain testing PPA`_ and use it to install a modern GCC. There is
+a really nice discussions of this on the `ask ubuntu stack exchange`_. However,
+not all users can use PPAs and there are many other distributions, so it may be
+necessary (or just useful, if you're here you *are* doing compiler development
+after all) to build and install GCC from source. It is also quite easy to do
+these days.
+
+.. _toolchain testing PPA:
+ https://launchpad.net/~ubuntu-toolchain-r/+archive/test
+.. _ask ubuntu stack exchange:
+ http://askubuntu.com/questions/271388/how-to-install-gcc-4-8-in-ubuntu-12-04-from-the-terminal
+
+Easy steps for installing GCC 4.8.2:
+
+.. code-block:: console
+
+ % wget ftp://ftp.gnu.org/gnu/gcc/gcc-4.8.2/gcc-4.8.2.tar.bz2
+ % tar -xvjf gcc-4.8.2.tar.bz2
+ % cd gcc-4.8.2
+ % ./contrib/download_prerequisites
+ % cd ..
+ % mkdir gcc-4.8.2-build
+ % cd gcc-4.8.2-build
+ % $PWD/../gcc-4.8.2/configure --prefix=$HOME/toolchains --enable-languages=c,c++
+ % make -j$(nproc)
+ % make install
+
+For more details, check out the excellent `GCC wiki entry`_, where I got most
+of this information from.
+
+.. _GCC wiki entry:
+ http://gcc.gnu.org/wiki/InstallingGCC
+
+Once you have a GCC toolchain, configure your build of LLVM to use the new
+toolchain for your host compiler and C++ standard library. Because the new
+version of libstdc++ is not on the system library search path, you need to pass
+extra linker flags so that it can be found at link time (``-L``) and at runtime
+(``-rpath``). If you are using CMake, this invocation should produce working
+binaries:
+
+.. code-block:: console
+
+ % mkdir build
+ % cd build
+ % CC=$HOME/toolchains/bin/gcc CXX=$HOME/toolchains/bin/g++ \
+ cmake .. -DCMAKE_CXX_LINK_FLAGS="-Wl,-rpath,$HOME/toolchains/lib64 -L$HOME/toolchains/lib64"
+
+If you fail to set rpath, most LLVM binaries will fail on startup with a message
+from the loader similar to ``libstdc++.so.6: version `GLIBCXX_3.4.20' not
+found``. This means you need to tweak the -rpath linker flag.
+
+When you build Clang, you will need to give *it* access to modern C++11
+standard library in order to use it as your new host in part of a bootstrap.
+There are two easy ways to do this, either build (and install) libc++ along
+with Clang and then use it with the ``-stdlib=libc++`` compile and link flag,
+or install Clang into the same prefix (``$HOME/toolchains`` above) as GCC.
+Clang will look within its own prefix for libstdc++ and use it if found. You
+can also add an explicit prefix for Clang to look in for a GCC toolchain with
+the ``--gcc-toolchain=/opt/my/gcc/prefix`` flag, passing it to both compile and
+link commands when using your just-built-Clang to bootstrap.
+
+.. _Getting Started with LLVM:
+
+Getting Started with LLVM
+=========================
+
+The remainder of this guide is meant to get you up and running with LLVM and to
+give you some basic information about the LLVM environment.
+
+The later sections of this guide describe the `general layout`_ of the LLVM
+source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
+more information about LLVM or to get help via e-mail.
+
+Terminology and Notation
+------------------------
+
+Throughout this manual, the following names are used to denote paths specific to
+the local system and working environment. *These are not environment variables
+you need to set but just strings used in the rest of this document below*. In
+any of the examples below, simply replace each of these names with the
+appropriate pathname on your local system. All these paths are absolute:
+
+``SRC_ROOT``
+
+ This is the top level directory of the LLVM source tree.
+
+``OBJ_ROOT``
+
+ This is the top level directory of the LLVM object tree (i.e. the tree where
+ object files and compiled programs will be placed. It can be the same as
+ SRC_ROOT).
+
+.. _Setting Up Your Environment:
+
+Setting Up Your Environment
+---------------------------
+
+In order to compile and use LLVM, you may need to set some environment
+variables.
+
+``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
+
+ [Optional] This environment variable helps LLVM linking tools find the
+ locations of your bitcode libraries. It is provided only as a convenience
+ since you can specify the paths using the -L options of the tools and the
+ C/C++ front-end will automatically use the bitcode files installed in its
+ ``lib`` directory.
+
+Unpacking the LLVM Archives
+---------------------------
+
+If you have the LLVM distribution, you will need to unpack it before you can
+begin to compile it. LLVM is distributed as a set of two files: the LLVM suite
+and the LLVM GCC front end compiled for your platform. There is an additional
+test suite that is optional. Each file is a TAR archive that is compressed with
+the gzip program.
+
+The files are as follows, with *x.y* marking the version number:
+
+``llvm-x.y.tar.gz``
+
+ Source release for the LLVM libraries and tools.
+
+``llvm-test-x.y.tar.gz``
+
+ Source release for the LLVM test-suite.
+
+.. _checkout:
+
+Checkout LLVM from Subversion
+-----------------------------
+
+If you have access to our Subversion repository, you can get a fresh copy of the
+entire source code. All you need to do is check it out from Subversion as
+follows:
+
+* ``cd where-you-want-llvm-to-live``
+* Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
+* Read-Write:``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
+
+This will create an '``llvm``' directory in the current directory and fully
+populate it with the LLVM source code, Makefiles, test directories, and local
+copies of documentation files.
+
+If you want to get a specific release (as opposed to the most recent revision),
+you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
+following releases are located in the following subdirectories of the '``tags``'
+directory:
+
+* Release 3.4: **RELEASE_34/final**
+* Release 3.3: **RELEASE_33/final**
+* Release 3.2: **RELEASE_32/final**
+* Release 3.1: **RELEASE_31/final**
+* Release 3.0: **RELEASE_30/final**
+* Release 2.9: **RELEASE_29/final**
+* Release 2.8: **RELEASE_28**
+* Release 2.7: **RELEASE_27**
+* Release 2.6: **RELEASE_26**
+* Release 2.5: **RELEASE_25**
+* Release 2.4: **RELEASE_24**
+* Release 2.3: **RELEASE_23**
+* Release 2.2: **RELEASE_22**
+* Release 2.1: **RELEASE_21**
+* Release 2.0: **RELEASE_20**
+* Release 1.9: **RELEASE_19**
+* Release 1.8: **RELEASE_18**
+* Release 1.7: **RELEASE_17**
+* Release 1.6: **RELEASE_16**
+* Release 1.5: **RELEASE_15**
+* Release 1.4: **RELEASE_14**
+* Release 1.3: **RELEASE_13**
+* Release 1.2: **RELEASE_12**
+* Release 1.1: **RELEASE_11**
+* Release 1.0: **RELEASE_1**
+
+If you would like to get the LLVM test suite (a separate package as of 1.4), you
+get it from the Subversion repository:
+
+.. code-block:: console
+
+ % cd llvm/projects
+ % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
+
+By placing it in the ``llvm/projects``, it will be automatically configured by
+the LLVM configure script as well as automatically updated when you run ``svn
+update``.
+
+Git Mirror
+----------
+
+Git mirrors are available for a number of LLVM subprojects. These mirrors sync
+automatically with each Subversion commit and contain all necessary git-svn
+marks (so, you can recreate git-svn metadata locally). Note that right now
+mirrors reflect only ``trunk`` for each project. You can do the read-only Git
+clone of LLVM via:
+
+.. code-block:: console
+
+ % git clone http://llvm.org/git/llvm.git
+
+If you want to check out clang too, run:
+
+.. code-block:: console
+
+ % cd llvm/tools
+ % git clone http://llvm.org/git/clang.git
+
+If you want to check out compiler-rt too, run:
+
+.. code-block:: console
+
+ % cd llvm/projects
+ % git clone http://llvm.org/git/compiler-rt.git
+
+If you want to check out the Test Suite Source Code (optional), run:
+
+.. code-block:: console
+
+ % cd llvm/projects
+ % git clone http://llvm.org/git/test-suite.git
+
+Since the upstream repository is in Subversion, you should use ``git
+pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
+in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
+master branch, run the following command:
+
+.. code-block:: console
+
+ % git config branch.master.rebase true
+
+Sending patches with Git
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
+
+Assume ``master`` points the upstream and ``mybranch`` points your working
+branch, and ``mybranch`` is rebased onto ``master``. At first you may check
+sanity of whitespaces:
+
+.. code-block:: console
+
+ % git diff --check master..mybranch
+
+The easiest way to generate a patch is as below:
+
+.. code-block:: console
+
+ % git diff master..mybranch > /path/to/mybranch.diff
+
+It is a little different from svn-generated diff. git-diff-generated diff has
+prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
+could be accepted with ``patch -p1 -N``.
+
+But you may generate patchset with git-format-patch. It generates by-each-commit
+patchset. To generate patch files to attach to your article:
+
+.. code-block:: console
+
+ % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
+
+If you would like to send patches directly, you may use git-send-email or
+git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
+
+.. code-block:: console
+
+ % git format-patch --attach master..mybranch --stdout | git imap-send
+
+Then, your .git/config should have [imap] sections.
+
+.. code-block:: ini
+
+ [imap]
+ host = imaps://imap.gmail.com
+ user = your.gmail.account at gmail.com
+ pass = himitsu!
+ port = 993
+ sslverify = false
+ ; in English
+ folder = "[Gmail]/Drafts"
+ ; example for Japanese, "Modified UTF-7" encoded.
+ folder = "[Gmail]/&Tgtm+DBN-"
+ ; example for Traditional Chinese
+ folder = "[Gmail]/&g0l6Pw-"
+
+For developers to work with git-svn
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+To set up clone from which you can submit code using ``git-svn``, run:
+
+.. code-block:: console
+
+ % git clone http://llvm.org/git/llvm.git
+ % cd llvm
+ % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
+ % git config svn-remote.svn.fetch :refs/remotes/origin/master
+ % git svn rebase -l # -l avoids fetching ahead of the git mirror.
+
+ # If you have clang too:
+ % cd tools
+ % git clone http://llvm.org/git/clang.git
+ % cd clang
+ % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
+ % git config svn-remote.svn.fetch :refs/remotes/origin/master
+ % git svn rebase -l
+
+Likewise for compiler-rt and test-suite.
+
+To update this clone without generating git-svn tags that conflict with the
+upstream Git repo, run:
+
+.. code-block:: console
+
+ % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
+ % git checkout master
+ % git svn rebase -l
+ % (cd tools/clang &&
+ git checkout master &&
+ git svn rebase -l)
+
+Likewise for compiler-rt and test-suite.
+
+This leaves your working directories on their master branches, so you'll need to
+``checkout`` each working branch individually and ``rebase`` it on top of its
+parent branch.
+
+For those who wish to be able to update an llvm repo/revert patches easily using
+git-svn, please look in the directory for the scripts ``git-svnup`` and
+``git-svnrevert``.
+
+To perform the aforementioned update steps go into your source directory and
+just type ``git-svnup`` or ``git svnup`` and everything will just work.
+
+If one wishes to revert a commit with git-svn, but do not want the git hash to
+escape into the commit message, one can use the script ``git-svnrevert`` or
+``git svnrevert`` which will take in the git hash for the commit you want to
+revert, look up the appropriate svn revision, and output a message where all
+references to the git hash have been replaced with the svn revision.
+
+To commit back changes via git-svn, use ``git svn dcommit``:
+
+.. code-block:: console
+
+ % git svn dcommit
+
+Note that git-svn will create one SVN commit for each Git commit you have pending,
+so squash and edit each commit before executing ``dcommit`` to make sure they all
+conform to the coding standards and the developers' policy.
+
+On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict,
+please make sure your current branch is up-to-date (via fetch/rebase) before
+proceeding.
+
+The git-svn metadata can get out of sync after you mess around with branches and
+``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
+about files with uncommitted changes. The fix is to rebuild the metadata:
+
+.. code-block:: console
+
+ % rm -rf .git/svn
+ % git svn rebase -l
+
+Please, refer to the Git-SVN manual (``man git-svn``) for more information.
+
+Local LLVM Configuration
+------------------------
+
+Once checked out from the Subversion repository, the LLVM suite source code must
+be configured via the ``configure`` script. This script sets variables in the
+various ``*.in`` files, most notably ``llvm/Makefile.config`` and
+``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
+Makefiles needed to begin building LLVM.
+
+The following environment variables are used by the ``configure`` script to
+configure the build system:
+
++------------+-----------------------------------------------------------+
+| Variable | Purpose |
++============+===========================================================+
+| CC | Tells ``configure`` which C compiler to use. By default, |
+| | ``configure`` will check ``PATH`` for ``clang`` and GCC C |
+| | compilers (in this order). Use this variable to override |
+| | ``configure``\'s default behavior. |
++------------+-----------------------------------------------------------+
+| CXX | Tells ``configure`` which C++ compiler to use. By |
+| | default, ``configure`` will check ``PATH`` for |
+| | ``clang++`` and GCC C++ compilers (in this order). Use |
+| | this variable to override ``configure``'s default |
+| | behavior. |
++------------+-----------------------------------------------------------+
+
+The following options can be used to set or enable LLVM specific options:
+
+``--enable-optimized``
+
+ Enables optimized compilation (debugging symbols are removed and GCC
+ optimization flags are enabled). Note that this is the default setting if you
+ are using the LLVM distribution. The default behavior of a Subversion
+ checkout is to use an unoptimized build (also known as a debug build).
+
+``--enable-debug-runtime``
+
+ Enables debug symbols in the runtime libraries. The default is to strip debug
+ symbols from the runtime libraries.
+
+``--enable-jit``
+
+ Compile the Just In Time (JIT) compiler functionality. This is not available
+ on all platforms. The default is dependent on platform, so it is best to
+ explicitly enable it if you want it.
+
+``--enable-targets=target-option``
+
+ Controls which targets will be built and linked into llc. The default value
+ for ``target_options`` is "all" which builds and links all available targets.
+ The "host" target is selected as the target of the build host. You can also
+ specify a comma separated list of target names that you want available in llc.
+ The target names use all lower case. The current set of targets is:
+
+ ``aarch64, arm, arm64, cpp, hexagon, mips, mipsel, mips64, mips64el, msp430,
+ powerpc, nvptx, r600, sparc, systemz, x86, x86_64, xcore``.
+
+``--enable-doxygen``
+
+ Look for the doxygen program and enable construction of doxygen based
+ documentation from the source code. This is disabled by default because
+ generating the documentation can take a long time and producess 100s of
+ megabytes of output.
+
+To configure LLVM, follow these steps:
+
+#. Change directory into the object root directory:
+
+ .. code-block:: console
+
+ % cd OBJ_ROOT
+
+#. Run the ``configure`` script located in the LLVM source tree:
+
+ .. code-block:: console
+
+ % SRC_ROOT/configure --prefix=/install/path [other options]
+
+Compiling the LLVM Suite Source Code
+------------------------------------
+
+Once you have configured LLVM, you can build it. There are three types of
+builds:
+
+Debug Builds
+
+ These builds are the default when one is using a Subversion checkout and
+ types ``gmake`` (unless the ``--enable-optimized`` option was used during
+ configuration). The build system will compile the tools and libraries with
+ debugging information. To get a Debug Build using the LLVM distribution the
+ ``--disable-optimized`` option must be passed to ``configure``.
+
+Release (Optimized) Builds
+
+ These builds are enabled with the ``--enable-optimized`` option to
+ ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
+ line. For these builds, the build system will compile the tools and libraries
+ with GCC optimizations enabled and strip debugging information from the
+ libraries and executables it generates. Note that Release Builds are default
+ when using an LLVM distribution.
+
+Profile Builds
+
+ These builds are for use with profiling. They compile profiling information
+ into the code for use with programs like ``gprof``. Profile builds must be
+ started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
+
+Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
+directory and issuing the following command:
+
+.. code-block:: console
+
+ % gmake
+
+If the build fails, please `check here`_ to see if you are using a version of
+GCC that is known not to compile LLVM.
+
+If you have multiple processors in your machine, you may wish to use some of the
+parallel build options provided by GNU Make. For example, you could use the
+command:
+
+.. code-block:: console
+
+ % gmake -j2
+
+There are several special targets which are useful when working with the LLVM
+source code:
+
+``gmake clean``
+
+ Removes all files generated by the build. This includes object files,
+ generated C/C++ files, libraries, and executables.
+
+``gmake dist-clean``
+
+ Removes everything that ``gmake clean`` does, but also removes files generated
+ by ``configure``. It attempts to return the source tree to the original state
+ in which it was shipped.
+
+``gmake install``
+
+ Installs LLVM header files, libraries, tools, and documentation in a hierarchy
+ under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
+ defaults to ``/usr/local``.
+
+``gmake -C runtime install-bytecode``
+
+ Assuming you built LLVM into $OBJDIR, when this command is run, it will
+ install bitcode libraries into the GCC front end's bitcode library directory.
+ If you need to update your bitcode libraries, this is the target to use once
+ you've built them.
+
+Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
+these ``make`` targets and descriptions of other targets available.
+
+It is also possible to override default values from ``configure`` by declaring
+variables on the command line. The following are some examples:
+
+``gmake ENABLE_OPTIMIZED=1``
+
+ Perform a Release (Optimized) build.
+
+``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
+
+ Perform a Release (Optimized) build without assertions enabled.
+
+``gmake ENABLE_OPTIMIZED=0``
+
+ Perform a Debug build.
+
+``gmake ENABLE_PROFILING=1``
+
+ Perform a Profiling build.
+
+``gmake VERBOSE=1``
+
+ Print what ``gmake`` is doing on standard output.
+
+``gmake TOOL_VERBOSE=1``
+
+ Ask each tool invoked by the makefiles to print out what it is doing on
+ the standard output. This also implies ``VERBOSE=1``.
+
+Every directory in the LLVM object tree includes a ``Makefile`` to build it and
+any subdirectories that it contains. Entering any directory inside the LLVM
+object tree and typing ``gmake`` should rebuild anything in or below that
+directory that is out of date.
+
+This does not apply to building the documentation.
+LLVM's (non-Doxygen) documentation is produced with the
+`Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
+There are some HTML documents that have not yet been converted to the new
+system (which uses the easy-to-read and easy-to-write
+`reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
+language).
+The generated documentation is built in the ``SRC_ROOT/docs`` directory using
+a special makefile.
+For instructions on how to install Sphinx, see
+`Sphinx Introduction for LLVM Developers
+<http://lld.llvm.org/sphinx_intro.html>`_.
+After following the instructions there for installing Sphinx, build the LLVM
+HTML documentation by doing the following:
+
+.. code-block:: console
+
+ $ cd SRC_ROOT/docs
+ $ make -f Makefile.sphinx
+
+This creates a ``_build/html`` sub-directory with all of the HTML files, not
+just the generated ones.
+This directory corresponds to ``llvm.org/docs``.
+For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
+``llvm.org/docs/SphinxQuickstartTemplate.html``.
+The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
+
+Cross-Compiling LLVM
+--------------------
+
+It is possible to cross-compile LLVM itself. That is, you can create LLVM
+executables and libraries to be hosted on a platform different from the platform
+where they are built (a Canadian Cross build). To configure a cross-compile,
+supply the configure script with ``--build`` and ``--host`` options that are
+different. The values of these options must be legal target triples that your
+GCC compiler supports.
+
+The result of such a build is executables that are not runnable on on the build
+host (--build option) but can be executed on the compile host (--host option).
+
+Check :doc:`HowToCrossCompileLLVM` and `Clang docs on how to cross-compile in general
+<http://clang.llvm.org/docs/CrossCompilation.html>`_ for more information
+about cross-compiling.
+
+The Location of LLVM Object Files
+---------------------------------
+
+The LLVM build system is capable of sharing a single LLVM source tree among
+several LLVM builds. Hence, it is possible to build LLVM for several different
+platforms or configurations using the same source tree.
+
+This is accomplished in the typical autoconf manner:
+
+* Change directory to where the LLVM object files should live:
+
+ .. code-block:: console
+
+ % cd OBJ_ROOT
+
+* Run the ``configure`` script found in the LLVM source directory:
+
+ .. code-block:: console
+
+ % SRC_ROOT/configure
+
+The LLVM build will place files underneath *OBJ_ROOT* in directories named after
+the build type:
+
+Debug Builds with assertions enabled (the default)
+
+ Tools
+
+ ``OBJ_ROOT/Debug+Asserts/bin``
+
+ Libraries
+
+ ``OBJ_ROOT/Debug+Asserts/lib``
+
+Release Builds
+
+ Tools
+
+ ``OBJ_ROOT/Release/bin``
+
+ Libraries
+
+ ``OBJ_ROOT/Release/lib``
+
+Profile Builds
+
+ Tools
+
+ ``OBJ_ROOT/Profile/bin``
+
+ Libraries
+
+ ``OBJ_ROOT/Profile/lib``
+
+Optional Configuration Items
+----------------------------
+
+If you're running on a Linux system that supports the `binfmt_misc
+<http://en.wikipedia.org/wiki/binfmt_misc>`_
+module, and you have root access on the system, you can set your system up to
+execute LLVM bitcode files directly. To do this, use commands like this (the
+first command may not be required if you are already using the module):
+
+.. code-block:: console
+
+ % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
+ % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
+ % chmod u+x hello.bc (if needed)
+ % ./hello.bc
+
+This allows you to execute LLVM bitcode files directly. On Debian, you can also
+use this command instead of the 'echo' command above:
+
+.. code-block:: console
+
+ % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
+
+.. _Program Layout:
+.. _general layout:
+
+Program Layout
+==============
+
+One useful source of information about the LLVM source base is the LLVM `doxygen
+<http://www.doxygen.org/>`_ documentation available at
+`<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
+layout:
+
+``llvm/examples``
+-----------------
+
+This directory contains some simple examples of how to use the LLVM IR and JIT.
+
+``llvm/include``
+----------------
+
+This directory contains public header files exported from the LLVM library. The
+three main subdirectories of this directory are:
+
+``llvm/include/llvm``
+
+ This directory contains all of the LLVM specific header files. This directory
+ also has subdirectories for different portions of LLVM: ``Analysis``,
+ ``CodeGen``, ``Target``, ``Transforms``, etc...
+
+``llvm/include/llvm/Support``
+
+ This directory contains generic support libraries that are provided with LLVM
+ but not necessarily specific to LLVM. For example, some C++ STL utilities and
+ a Command Line option processing library store their header files here.
+
+``llvm/include/llvm/Config``
+
+ This directory contains header files configured by the ``configure`` script.
+ They wrap "standard" UNIX and C header files. Source code can include these
+ header files which automatically take care of the conditional #includes that
+ the ``configure`` script generates.
+
+``llvm/lib``
+------------
+
+This directory contains most of the source files of the LLVM system. In LLVM,
+almost all code exists in libraries, making it very easy to share code among the
+different `tools`_.
+
+``llvm/lib/IR/``
+
+ This directory holds the core LLVM source files that implement core classes
+ like Instruction and BasicBlock.
+
+``llvm/lib/AsmParser/``
+
+ This directory holds the source code for the LLVM assembly language parser
+ library.
+
+``llvm/lib/Bitcode/``
+
+ This directory holds code for reading and write LLVM bitcode.
+
+``llvm/lib/Analysis/``
+
+ This directory contains a variety of different program analyses, such as
+ Dominator Information, Call Graphs, Induction Variables, Interval
+ Identification, Natural Loop Identification, etc.
+
+``llvm/lib/Transforms/``
+
+ This directory contains the source code for the LLVM to LLVM program
+ transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
+ Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
+ Elimination, and many others.
+
+``llvm/lib/Target/``
+
+ This directory contains files that describe various target architectures for
+ code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
+ X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
+ backend.
+
+``llvm/lib/CodeGen/``
+
+ This directory contains the major parts of the code generator: Instruction
+ Selector, Instruction Scheduling, and Register Allocation.
+
+``llvm/lib/MC/``
+
+ (FIXME: T.B.D.)
+
+``llvm/lib/Debugger/``
+
+ This directory contains the source level debugger library that makes it
+ possible to instrument LLVM programs so that a debugger could identify source
+ code locations at which the program is executing.
+
+``llvm/lib/ExecutionEngine/``
+
+ This directory contains libraries for executing LLVM bitcode directly at
+ runtime in both interpreted and JIT compiled fashions.
+
+``llvm/lib/Support/``
+
+ This directory contains the source code that corresponds to the header files
+ located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
+
+``llvm/projects``
+-----------------
+
+This directory contains projects that are not strictly part of LLVM but are
+shipped with LLVM. This is also the directory where you should create your own
+LLVM-based projects.
+
+``llvm/runtime``
+----------------
+
+This directory contains libraries which are compiled into LLVM bitcode and used
+when linking programs with the Clang front end. Most of these libraries are
+skeleton versions of real libraries; for example, libc is a stripped down
+version of glibc.
+
+Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
+to compile.
+
+``llvm/test``
+-------------
+
+This directory contains feature and regression tests and other basic sanity
+checks on the LLVM infrastructure. These are intended to run quickly and cover a
+lot of territory without being exhaustive.
+
+``test-suite``
+--------------
+
+This is not a directory in the normal llvm module; it is a separate Subversion
+module that must be checked out (usually to ``projects/test-suite``). This
+module contains a comprehensive correctness, performance, and benchmarking test
+suite for LLVM. It is a separate Subversion module because not every LLVM user
+is interested in downloading or building such a comprehensive test suite. For
+further details on this test suite, please see the :doc:`Testing Guide
+<TestingGuide>` document.
+
+.. _tools:
+
+``llvm/tools``
+--------------
+
+The **tools** directory contains the executables built out of the libraries
+above, which form the main part of the user interface. You can always get help
+for a tool by typing ``tool_name -help``. The following is a brief introduction
+to the most important tools. More detailed information is in
+the `Command Guide <CommandGuide/index.html>`_.
+
+``bugpoint``
+
+ ``bugpoint`` is used to debug optimization passes or code generation backends
+ by narrowing down the given test case to the minimum number of passes and/or
+ instructions that still cause a problem, whether it is a crash or
+ miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
+ ``bugpoint``.
+
+``llvm-ar``
+
+ The archiver produces an archive containing the given LLVM bitcode files,
+ optionally with an index for faster lookup.
+
+``llvm-as``
+
+ The assembler transforms the human readable LLVM assembly to LLVM bitcode.
+
+``llvm-dis``
+
+ The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
+
+``llvm-link``
+
+ ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
+ program.
+
+``lli``
+
+ ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
+ (although very slowly...). For architectures that support it (currently x86,
+ Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
+ compiler (if the functionality was compiled in), and will execute the code
+ *much* faster than the interpreter.
+
+``llc``
+
+ ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
+ native code assembly file or to C code (with the ``-march=c`` option).
+
+``opt``
+
+ ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
+ (which are specified on the command line), and then outputs the resultant
+ bitcode. The '``opt -help``' command is a good way to get a list of the
+ program transformations available in LLVM.
+
+ ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
+ file and print out the results. It is primarily useful for debugging
+ analyses, or familiarizing yourself with what an analysis does.
+
+``llvm/utils``
+--------------
+
+This directory contains utilities for working with LLVM source code, and some of
+the utilities are actually required as part of the build process because they
+are code generators for parts of LLVM infrastructure.
+
+
+``codegen-diff``
+
+ ``codegen-diff`` is a script that finds differences between code that LLC
+ generates and code that LLI generates. This is a useful tool if you are
+ debugging one of them, assuming that the other generates correct output. For
+ the full user manual, run ```perldoc codegen-diff'``.
+
+``emacs/``
+
+ The ``emacs`` directory contains syntax-highlighting files which will work
+ with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
+ assembly files and TableGen description files. For information on how to use
+ the syntax files, consult the ``README`` file in that directory.
+
+``getsrcs.sh``
+
+ The ``getsrcs.sh`` script finds and outputs all non-generated source files,
+ which is useful if one wishes to do a lot of development across directories
+ and does not want to individually find each file. One way to use it is to run,
+ for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
+ tree.
+
+``llvmgrep``
+
+ This little tool performs an ``egrep -H -n`` on each source file in LLVM and
+ passes to it a regular expression provided on ``llvmgrep``'s command
+ line. This is a very efficient way of searching the source base for a
+ particular regular expression.
+
+``makellvm``
+
+ The ``makellvm`` script compiles all files in the current directory and then
+ compiles and links the tool that is the first argument. For example, assuming
+ you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
+ path, simply running ``makellvm llc`` will make a build of the current
+ directory, switch to directory ``llvm/tools/llc`` and build it, causing a
+ re-linking of LLC.
+
+``TableGen/``
+
+ The ``TableGen`` directory contains the tool used to generate register
+ descriptions, instruction set descriptions, and even assemblers from common
+ TableGen description files.
+
+``vim/``
+
+ The ``vim`` directory contains syntax-highlighting files which will work with
+ the VIM editor, providing syntax highlighting support for LLVM assembly files
+ and TableGen description files. For information on how to use the syntax
+ files, consult the ``README`` file in that directory.
+
+.. _simple example:
+
+An Example Using the LLVM Tool Chain
+====================================
+
+This section gives an example of using LLVM with the Clang front end.
+
+Example with clang
+------------------
+
+#. First, create a simple C file, name it 'hello.c':
+
+ .. code-block:: c
+
+ #include <stdio.h>
+
+ int main() {
+ printf("hello world\n");
+ return 0;
+ }
+
+#. Next, compile the C file into a native executable:
+
+ .. code-block:: console
+
+ % clang hello.c -o hello
+
+ .. note::
+
+ Clang works just like GCC by default. The standard -S and -c arguments
+ work as usual (producing a native .s or .o file, respectively).
+
+#. Next, compile the C file into an LLVM bitcode file:
+
+ .. code-block:: console
+
+ % clang -O3 -emit-llvm hello.c -c -o hello.bc
+
+ The -emit-llvm option can be used with the -S or -c options to emit an LLVM
+ ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
+ the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
+
+#. Run the program in both forms. To run the program, use:
+
+ .. code-block:: console
+
+ % ./hello
+
+ and
+
+ .. code-block:: console
+
+ % lli hello.bc
+
+ The second examples shows how to invoke the LLVM JIT, :doc:`lli
+ <CommandGuide/lli>`.
+
+#. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
+
+ .. code-block:: console
+
+ % llvm-dis < hello.bc | less
+
+#. Compile the program to native assembly using the LLC code generator:
+
+ .. code-block:: console
+
+ % llc hello.bc -o hello.s
+
+#. Assemble the native assembly language file into a program:
+
+ .. code-block:: console
+
+ % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
+
+ % gcc hello.s -o hello.native # On others
+
+#. Execute the native code program:
+
+ .. code-block:: console
+
+ % ./hello.native
+
+ Note that using clang to compile directly to native code (i.e. when the
+ ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
+
+Common Problems
+===============
+
+If you are having problems building or using LLVM, or if you have any other
+general questions about LLVM, please consult the `Frequently Asked
+Questions <FAQ.html>`_ page.
+
+.. _links:
+
+Links
+=====
+
+This document is just an **introduction** on how to use LLVM to do some simple
+things... there are many more interesting and complicated things that you can do
+that aren't documented here (but we'll gladly accept a patch if you want to
+write something up!). For more information about LLVM, check out:
+
+* `LLVM Homepage <http://llvm.org/>`_
+* `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
+* `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_
Added: www-releases/trunk/3.6.2/docs/_sources/GettingStartedVS.txt
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==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/GettingStartedVS.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/GettingStartedVS.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,234 @@
+==================================================================
+Getting Started with the LLVM System using Microsoft Visual Studio
+==================================================================
+
+.. contents::
+ :local:
+
+
+Overview
+========
+Welcome to LLVM on Windows! This document only covers LLVM on Windows using
+Visual Studio, not mingw or cygwin. In order to get started, you first need to
+know some basic information.
+
+There are many different projects that compose LLVM. The first is the LLVM
+suite. This contains all of the tools, libraries, and header files needed to
+use LLVM. It contains an assembler, disassembler,
+bitcode analyzer and bitcode optimizer. It also contains a test suite that can
+be used to test the LLVM tools.
+
+Another useful project on Windows is `Clang <http://clang.llvm.org/>`_.
+Clang is a C family ([Objective]C/C++) compiler. Clang mostly works on
+Windows, but does not currently understand all of the Microsoft extensions
+to C and C++. Because of this, clang cannot parse the C++ standard library
+included with Visual Studio, nor parts of the Windows Platform SDK. However,
+most standard C programs do compile. Clang can be used to emit bitcode,
+directly emit object files or even linked executables using Visual Studio's
+``link.exe``.
+
+The large LLVM test suite cannot be run on the Visual Studio port at this
+time.
+
+Most of the tools build and work. ``bugpoint`` does build, but does
+not work.
+
+Additional information about the LLVM directory structure and tool chain
+can be found on the main :doc:`GettingStarted` page.
+
+
+Requirements
+============
+Before you begin to use the LLVM system, review the requirements given
+below. This may save you some trouble by knowing ahead of time what hardware
+and software you will need.
+
+Hardware
+--------
+Any system that can adequately run Visual Studio 2012 is fine. The LLVM
+source tree and object files, libraries and executables will consume
+approximately 3GB.
+
+Software
+--------
+You will need Visual Studio 2012 or higher.
+
+You will also need the `CMake <http://www.cmake.org/>`_ build system since it
+generates the project files you will use to build with.
+
+If you would like to run the LLVM tests you will need `Python
+<http://www.python.org/>`_. Version 2.7 and newer are known to work. You will
+need `GnuWin32 <http://gnuwin32.sourceforge.net/>`_ tools, too.
+
+Do not install the LLVM directory tree into a path containing spaces (e.g.
+``C:\Documents and Settings\...``) as the configure step will fail.
+
+
+Getting Started
+===============
+Here's the short story for getting up and running quickly with LLVM:
+
+1. Read the documentation.
+2. Seriously, read the documentation.
+3. Remember that you were warned twice about reading the documentation.
+4. Get the Source Code
+
+ * With the distributed files:
+
+ 1. ``cd <where-you-want-llvm-to-live>``
+ 2. ``gunzip --stdout llvm-VERSION.tar.gz | tar -xvf -``
+ (*or use WinZip*)
+ 3. ``cd llvm``
+
+ * With anonymous Subversion access:
+
+ 1. ``cd <where-you-want-llvm-to-live>``
+ 2. ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
+ 3. ``cd llvm``
+
+5. Use `CMake <http://www.cmake.org/>`_ to generate up-to-date project files:
+
+ * Once CMake is installed then the simplest way is to just start the
+ CMake GUI, select the directory where you have LLVM extracted to, and
+ the default options should all be fine. One option you may really
+ want to change, regardless of anything else, might be the
+ ``CMAKE_INSTALL_PREFIX`` setting to select a directory to INSTALL to
+ once compiling is complete, although installation is not mandatory for
+ using LLVM. Another important option is ``LLVM_TARGETS_TO_BUILD``,
+ which controls the LLVM target architectures that are included on the
+ build.
+ * See the :doc:`LLVM CMake guide <CMake>` for detailed information about
+ how to configure the LLVM build.
+ * CMake generates project files for all build types. To select a specific
+ build type, use the Configuration manager from the VS IDE or the
+ ``/property:Configuration`` command line option when using MSBuild.
+
+6. Start Visual Studio
+
+ * In the directory you created the project files will have an ``llvm.sln``
+ file, just double-click on that to open Visual Studio.
+
+7. Build the LLVM Suite:
+
+ * The projects may still be built individually, but to build them all do
+ not just select all of them in batch build (as some are meant as
+ configuration projects), but rather select and build just the
+ ``ALL_BUILD`` project to build everything, or the ``INSTALL`` project,
+ which first builds the ``ALL_BUILD`` project, then installs the LLVM
+ headers, libs, and other useful things to the directory set by the
+ ``CMAKE_INSTALL_PREFIX`` setting when you first configured CMake.
+ * The Fibonacci project is a sample program that uses the JIT. Modify the
+ project's debugging properties to provide a numeric command line argument
+ or run it from the command line. The program will print the
+ corresponding fibonacci value.
+
+8. Test LLVM in Visual Studio:
+
+ * If ``%PATH%`` does not contain GnuWin32, you may specify
+ ``LLVM_LIT_TOOLS_DIR`` on CMake for the path to GnuWin32.
+ * You can run LLVM tests by merely building the project "check". The test
+ results will be shown in the VS output window.
+
+9. Test LLVM on the command line:
+
+ * The LLVM tests can be run by changing directory to the llvm source
+ directory and running:
+
+ .. code-block:: bat
+
+ C:\..\llvm> python ..\build\bin\llvm-lit --param build_config=Win32 --param build_mode=Debug --param llvm_site_config=../build/test/lit.site.cfg test
+
+ This example assumes that Python is in your PATH variable, you
+ have built a Win32 Debug version of llvm with a standard out of
+ line build. You should not see any unexpected failures, but will
+ see many unsupported tests and expected failures.
+
+ A specific test or test directory can be run with:
+
+ .. code-block:: bat
+
+ C:\..\llvm> python ..\build\bin\llvm-lit --param build_config=Win32 --param build_mode=Debug --param llvm_site_config=../build/test/lit.site.cfg test/path/to/test
+
+
+An Example Using the LLVM Tool Chain
+====================================
+
+1. First, create a simple C file, name it '``hello.c``':
+
+ .. code-block:: c
+
+ #include <stdio.h>
+ int main() {
+ printf("hello world\n");
+ return 0;
+ }
+
+2. Next, compile the C file into an LLVM bitcode file:
+
+ .. code-block:: bat
+
+ C:\..> clang -c hello.c -emit-llvm -o hello.bc
+
+ This will create the result file ``hello.bc`` which is the LLVM bitcode
+ that corresponds the compiled program and the library facilities that
+ it required. You can execute this file directly using ``lli`` tool,
+ compile it to native assembly with the ``llc``, optimize or analyze it
+ further with the ``opt`` tool, etc.
+
+ Alternatively you can directly output an executable with clang with:
+
+ .. code-block:: bat
+
+ C:\..> clang hello.c -o hello.exe
+
+ The ``-o hello.exe`` is required because clang currently outputs ``a.out``
+ when neither ``-o`` nor ``-c`` are given.
+
+3. Run the program using the just-in-time compiler:
+
+ .. code-block:: bat
+
+ C:\..> lli hello.bc
+
+4. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
+
+ .. code-block:: bat
+
+ C:\..> llvm-dis < hello.bc | more
+
+5. Compile the program to object code using the LLC code generator:
+
+ .. code-block:: bat
+
+ C:\..> llc -filetype=obj hello.bc
+
+6. Link to binary using Microsoft link:
+
+ .. code-block:: bat
+
+ C:\..> link hello.obj -defaultlib:libcmt
+
+7. Execute the native code program:
+
+ .. code-block:: bat
+
+ C:\..> hello.exe
+
+
+Common Problems
+===============
+If you are having problems building or using LLVM, or if you have any other
+general questions about LLVM, please consult the :doc:`Frequently Asked Questions
+<FAQ>` page.
+
+
+Links
+=====
+This document is just an **introduction** to how to use LLVM to do some simple
+things... there are many more interesting and complicated things that you can
+do that aren't documented here (but we'll gladly accept a patch if you want to
+write something up!). For more information about LLVM, check out:
+
+* `LLVM homepage <http://llvm.org/>`_
+* `LLVM doxygen tree <http://llvm.org/doxygen/>`_
+
Added: www-releases/trunk/3.6.2/docs/_sources/GoldPlugin.txt
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==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/GoldPlugin.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/GoldPlugin.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,174 @@
+====================
+The LLVM gold plugin
+====================
+
+Introduction
+============
+
+Building with link time optimization requires cooperation from
+the system linker. LTO support on Linux systems requires that you use the
+`gold linker`_ which supports LTO via plugins. This is the same mechanism
+used by the `GCC LTO`_ project.
+
+The LLVM gold plugin implements the gold plugin interface on top of
+:ref:`libLTO`. The same plugin can also be used by other tools such as
+``ar`` and ``nm``.
+
+.. _`gold linker`: http://sourceware.org/binutils
+.. _`GCC LTO`: http://gcc.gnu.org/wiki/LinkTimeOptimization
+.. _`gold plugin interface`: http://gcc.gnu.org/wiki/whopr/driver
+
+.. _lto-how-to-build:
+
+How to build it
+===============
+
+You need to have gold with plugin support and build the LLVMgold plugin.
+Check whether you have gold running ``/usr/bin/ld -v``. It will report "GNU
+gold" or else "GNU ld" if not. If you have gold, check for plugin support
+by running ``/usr/bin/ld -plugin``. If it complains "missing argument" then
+you have plugin support. If not, such as an "unknown option" error then you
+will either need to build gold or install a version with plugin support.
+
+* Download, configure and build gold with plugin support:
+
+ .. code-block:: bash
+
+ $ git clone --depth 1 git://sourceware.org/git/binutils-gdb.git binutils
+ $ mkdir build
+ $ cd build
+ $ ../binutils/configure --enable-gold --enable-plugins --disable-werror
+ $ make all-gold
+
+ That should leave you with ``build/gold/ld-new`` which supports
+ the ``-plugin`` option. Running ``make`` will additionally build
+ ``build/binutils/ar`` and ``nm-new`` binaries supporting plugins.
+
+* Build the LLVMgold plugin. If building with autotools, run configure with
+ ``--with-binutils-include=/path/to/binutils/include`` and run ``make``.
+ If building with CMake, run cmake with
+ ``-DLLVM_BINUTILS_INCDIR=/path/to/binutils/include``. The correct include
+ path will contain the file ``plugin-api.h``.
+
+Usage
+=====
+
+The linker takes a ``-plugin`` option that points to the path of
+the plugin ``.so`` file. To find out what link command ``gcc``
+would run in a given situation, run ``gcc -v [...]`` and
+look for the line where it runs ``collect2``. Replace that with
+``ld-new -plugin /path/to/LLVMgold.so`` to test it out. Once you're
+ready to switch to using gold, backup your existing ``/usr/bin/ld``
+then replace it with ``ld-new``.
+
+You should produce bitcode files from ``clang`` with the option
+``-flto``. This flag will also cause ``clang`` to look for the gold plugin in
+the ``lib`` directory under its prefix and pass the ``-plugin`` option to
+``ld``. It will not look for an alternate linker, which is why you need
+gold to be the installed system linker in your path.
+
+``ar`` and ``nm`` also accept the ``-plugin`` option and it's possible to
+to install ``LLVMgold.so`` to ``/usr/lib/bfd-plugins`` for a seamless setup.
+If you built your own gold, be sure to install the ``ar`` and ``nm-new`` you
+built to ``/usr/bin``.
+
+
+Example of link time optimization
+---------------------------------
+
+The following example shows a worked example of the gold plugin mixing LLVM
+bitcode and native code.
+
+.. code-block:: c
+
+ --- a.c ---
+ #include <stdio.h>
+
+ extern void foo1(void);
+ extern void foo4(void);
+
+ void foo2(void) {
+ printf("Foo2\n");
+ }
+
+ void foo3(void) {
+ foo4();
+ }
+
+ int main(void) {
+ foo1();
+ }
+
+ --- b.c ---
+ #include <stdio.h>
+
+ extern void foo2(void);
+
+ void foo1(void) {
+ foo2();
+ }
+
+ void foo4(void) {
+ printf("Foo4");
+ }
+
+.. code-block:: bash
+
+ --- command lines ---
+ $ clang -flto a.c -c -o a.o # <-- a.o is LLVM bitcode file
+ $ ar q a.a a.o # <-- a.a is an archive with LLVM bitcode
+ $ clang b.c -c -o b.o # <-- b.o is native object file
+ $ clang -flto a.a b.o -o main # <-- link with LLVMgold plugin
+
+Gold informs the plugin that foo3 is never referenced outside the IR,
+leading LLVM to delete that function. However, unlike in the :ref:`libLTO
+example <libLTO-example>` gold does not currently eliminate foo4.
+
+Quickstart for using LTO with autotooled projects
+=================================================
+
+Once your system ``ld``, ``ar``, and ``nm`` all support LLVM bitcode,
+everything is in place for an easy to use LTO build of autotooled projects:
+
+* Follow the instructions :ref:`on how to build LLVMgold.so
+ <lto-how-to-build>`.
+
+* Install the newly built binutils to ``$PREFIX``
+
+* Copy ``Release/lib/LLVMgold.so`` to ``$PREFIX/lib/bfd-plugins/``
+
+* Set environment variables (``$PREFIX`` is where you installed clang and
+ binutils):
+
+ .. code-block:: bash
+
+ export CC="$PREFIX/bin/clang -flto"
+ export CXX="$PREFIX/bin/clang++ -flto"
+ export AR="$PREFIX/bin/ar"
+ export NM="$PREFIX/bin/nm"
+ export RANLIB=/bin/true #ranlib is not needed, and doesn't support .bc files in .a
+
+* Or you can just set your path:
+
+ .. code-block:: bash
+
+ export PATH="$PREFIX/bin:$PATH"
+ export CC="clang -flto"
+ export CXX="clang++ -flto"
+ export RANLIB=/bin/true
+* Configure and build the project as usual:
+
+ .. code-block:: bash
+
+ % ./configure && make && make check
+
+The environment variable settings may work for non-autotooled projects too,
+but you may need to set the ``LD`` environment variable as well.
+
+Licensing
+=========
+
+Gold is licensed under the GPLv3. LLVMgold uses the interface file
+``plugin-api.h`` from gold which means that the resulting ``LLVMgold.so``
+binary is also GPLv3. This can still be used to link non-GPLv3 programs
+just as much as gold could without the plugin.
Added: www-releases/trunk/3.6.2/docs/_sources/HowToAddABuilder.txt
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==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/HowToAddABuilder.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/HowToAddABuilder.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,86 @@
+===================================================================
+How To Add Your Build Configuration To LLVM Buildbot Infrastructure
+===================================================================
+
+Introduction
+============
+
+This document contains information about adding a build configuration and
+buildslave to private slave builder to LLVM Buildbot Infrastructure
+`<http://lab.llvm.org:8011>`_.
+
+
+Steps To Add Builder To LLVM Buildbot
+=====================================
+Volunteers can provide their build machines to work as build slaves to
+public LLVM Buildbot.
+
+Here are the steps you can follow to do so:
+
+#. Check the existing build configurations to make sure the one you are
+ interested in is not covered yet or gets built on your computer much
+ faster than on the existing one. We prefer faster builds so developers
+ will get feedback sooner after changes get committed.
+
+#. The computer you will be registering with the LLVM buildbot
+ infrastructure should have all dependencies installed and you can
+ actually build your configuration successfully. Please check what degree
+ of parallelism (-j param) would give the fastest build. You can build
+ multiple configurations on one computer.
+
+#. Install buildslave (currently we are using buildbot version 0.8.5).
+ Depending on the platform, buildslave could be available to download and
+ install with your packet manager, or you can download it directly from
+ `<http://trac.buildbot.net>`_ and install it manually.
+
+#. Create a designated user account, your buildslave will be running under,
+ and set appropriate permissions.
+
+#. Choose the buildslave root directory (all builds will be placed under
+ it), buildslave access name and password the build master will be using
+ to authenticate your buildslave.
+
+#. Create a buildslave in context of that buildslave account. Point it to
+ the **lab.llvm.org** port **9990** (see `Buildbot documentation,
+ Creating a slave
+ <http://buildbot.net/buildbot/docs/current/full.html#creating-a-slave>`_
+ for more details) by running the following command:
+
+ .. code-block:: bash
+
+ $ buildslave create-slave <buildslave-root-directory> \
+ lab.llvm.org:9990 \
+ <buildslave-access-name> <buildslave-access-password>
+
+#. Fill the buildslave description and admin name/e-mail. Here is an
+ example of the buildslave description::
+
+ Windows 7 x64
+ Core i7 (2.66GHz), 16GB of RAM
+
+ g++.exe (TDM-1 mingw32) 4.4.0
+ GNU Binutils 2.19.1
+ cmake version 2.8.4
+ Microsoft(R) 32-bit C/C++ Optimizing Compiler Version 16.00.40219.01 for 80x86
+
+#. Make sure you can actually start the buildslave successfully. Then set
+ up your buildslave to start automatically at the start up time. See the
+ buildbot documentation for help. You may want to restart your computer
+ to see if it works.
+
+#. Send a patch which adds your build slave and your builder to zorg.
+
+ * slaves are added to ``buildbot/osuosl/master/config/slaves.py``
+ * builders are added to ``buildbot/osuosl/master/config/builders.py``
+
+#. Send the buildslave access name and the access password directly to
+ `Galina Kistanova <mailto:gkistanova at gmail.com>`_, and wait till she
+ will let you know that your changes are applied and buildmaster is
+ reconfigured.
+
+#. Check the status of your buildslave on the `Waterfall Display
+ <http://lab.llvm.org:8011/waterfall>`_ to make sure it is connected, and
+ ``http://lab.llvm.org:8011/buildslaves/<your-buildslave-name>`` to see
+ if administrator contact and slave information are correct.
+
+#. Wait for the first build to succeed and enjoy.
Added: www-releases/trunk/3.6.2/docs/_sources/HowToBuildOnARM.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/HowToBuildOnARM.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/HowToBuildOnARM.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/HowToBuildOnARM.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,69 @@
+===================================================================
+How To Build On ARM
+===================================================================
+
+Introduction
+============
+
+This document contains information about building/testing LLVM and
+Clang on an ARM machine.
+
+This document is *NOT* tailored to help you cross-compile LLVM/Clang
+to ARM on another architecture, for example an x86_64 machine. To find
+out more about cross-compiling, please check :doc:`HowToCrossCompileLLVM`.
+
+Notes On Building LLVM/Clang on ARM
+=====================================
+Here are some notes on building/testing LLVM/Clang on ARM. Note that
+ARM encompasses a wide variety of CPUs; this advice is primarily based
+on the ARMv6 and ARMv7 architectures and may be inapplicable to older chips.
+
+#. If you are building LLVM/Clang on an ARM board with 1G of memory or less,
+ please use ``gold`` rather then GNU ``ld``.
+ Building LLVM/Clang with ``--enable-optimized``
+ is preferred since it consumes less memory. Otherwise, the building
+ process will very likely fail due to insufficient memory. In any
+ case it is probably a good idea to set up a swap partition.
+
+#. If you want to run ``make check-all`` after building LLVM/Clang, to avoid
+ false alarms (e.g., ARCMT failure) please use at least the following
+ configuration:
+
+ .. code-block:: bash
+
+ $ ../$LLVM_SRC_DIR/configure --with-abi=aapcs-vfp
+
+#. The most popular Linaro/Ubuntu OS's for ARM boards, e.g., the
+ Pandaboard, have become hard-float platforms. The following set
+ of configuration options appears to be a good choice for this
+ platform:
+
+ .. code-block:: bash
+
+ ./configure --build=armv7l-unknown-linux-gnueabihf \
+ --host=armv7l-unknown-linux-gnueabihf \
+ --target=armv7l-unknown-linux-gnueabihf --with-cpu=cortex-a9 \
+ --with-float=hard --with-abi=aapcs-vfp --with-fpu=neon \
+ --enable-targets=arm --enable-optimized --enable-assertions
+
+#. ARM development boards can be unstable and you may experience that cores
+ are disappearing, caches being flushed on every big.LITTLE switch, and
+ other similar issues. To help ease the effect of this, set the Linux
+ scheduler to "performance" on **all** cores using this little script:
+
+ .. code-block:: bash
+
+ # The code below requires the package 'cpufrequtils' to be installed.
+ for ((cpu=0; cpu<`grep -c proc /proc/cpuinfo`; cpu++)); do
+ sudo cpufreq-set -c $cpu -g performance
+ done
+
+#. Running the build on SD cards is ok, but they are more prone to failures
+ than good quality USB sticks, and those are more prone to failures than
+ external hard-drives (those are also a lot faster). So, at least, you
+ should consider to buy a fast USB stick. On systems with a fast eMMC,
+ that's a good option too.
+
+#. Make sure you have a decent power supply (dozens of dollars worth) that can
+ provide *at least* 4 amperes, this is especially important if you use USB
+ devices with your board.
Added: www-releases/trunk/3.6.2/docs/_sources/HowToCrossCompileLLVM.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/HowToCrossCompileLLVM.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/HowToCrossCompileLLVM.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/HowToCrossCompileLLVM.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,175 @@
+===================================================================
+How To Cross-Compile Clang/LLVM using Clang/LLVM
+===================================================================
+
+Introduction
+============
+
+This document contains information about building LLVM and
+Clang on host machine, targeting another platform.
+
+For more information on how to use Clang as a cross-compiler,
+please check http://clang.llvm.org/docs/CrossCompilation.html.
+
+TODO: Add MIPS and other platforms to this document.
+
+Cross-Compiling from x86_64 to ARM
+==================================
+
+In this use case, we'll be using CMake and Ninja, on a Debian-based Linux
+system, cross-compiling from an x86_64 host (most Intel and AMD chips
+nowadays) to a hard-float ARM target (most ARM targets nowadays).
+
+The packages you'll need are:
+
+ * ``cmake``
+ * ``ninja-build`` (from backports in Ubuntu)
+ * ``gcc-4.7-arm-linux-gnueabihf``
+ * ``gcc-4.7-multilib-arm-linux-gnueabihf``
+ * ``binutils-arm-linux-gnueabihf``
+ * ``libgcc1-armhf-cross``
+ * ``libsfgcc1-armhf-cross``
+ * ``libstdc++6-armhf-cross``
+ * ``libstdc++6-4.7-dev-armhf-cross``
+
+Configuring CMake
+-----------------
+
+For more information on how to configure CMake for LLVM/Clang,
+see :doc:`CMake`.
+
+The CMake options you need to add are:
+ * ``-DCMAKE_CROSSCOMPILING=True``
+ * ``-DCMAKE_INSTALL_PREFIX=<install-dir>``
+ * ``-DLLVM_TABLEGEN=<path-to-host-bin>/llvm-tblgen``
+ * ``-DCLANG_TABLEGEN=<path-to-host-bin>/clang-tblgen``
+ * ``-DLLVM_DEFAULT_TARGET_TRIPLE=arm-linux-gnueabihf``
+ * ``-DLLVM_TARGET_ARCH=ARM``
+ * ``-DLLVM_TARGETS_TO_BUILD=ARM``
+ * ``-DCMAKE_CXX_FLAGS='-target armv7a-linux-gnueabihf -mcpu=cortex-a9 -I/usr/arm-linux-gnueabihf/include/c++/4.7.2/arm-linux-gnueabihf/ -I/usr/arm-linux-gnueabihf/include/ -mfloat-abi=hard -ccc-gcc-name arm-linux-gnueabihf-gcc'``
+
+The TableGen options are required to compile it with the host compiler,
+so you'll need to compile LLVM (or at least ``llvm-tblgen``) to your host
+platform before you start. The CXX flags define the target, cpu (which
+defaults to ``fpu=VFP3`` with NEON), and forcing the hard-float ABI. If you're
+using Clang as a cross-compiler, you will *also* have to set ``-ccc-gcc-name``,
+to make sure it picks the correct linker.
+
+Most of the time, what you want is to have a native compiler to the
+platform itself, but not others. It might not even be feasible to
+produce x86 binaries from ARM targets, so there's no point in compiling
+all back-ends. For that reason, you should also set the
+``TARGETS_TO_BUILD`` to only build the ARM back-end.
+
+You must set the ``CMAKE_INSTALL_PREFIX``, otherwise a ``ninja install``
+will copy ARM binaries to your root filesystem, which is not what you
+want.
+
+Hacks
+-----
+
+There are some bugs in current LLVM, which require some fiddling before
+running CMake:
+
+#. If you're using Clang as the cross-compiler, there is a problem in
+ the LLVM ARM back-end that is producing absolute relocations on
+ position-independent code (``R_ARM_THM_MOVW_ABS_NC``), so for now, you
+ should disable PIC:
+
+ .. code-block:: bash
+
+ -DLLVM_ENABLE_PIC=False
+
+ This is not a problem, since Clang/LLVM libraries are statically
+ linked anyway, it shouldn't affect much.
+
+#. The ARM libraries won't be installed in your system, and possibly
+ not easily installable anyway, so you'll have to build/download
+ them separately. But the CMake prepare step, which checks for
+ dependencies, will check the *host* libraries, not the *target*
+ ones.
+
+ A quick way of getting the libraries is to download them from
+ a distribution repository, like Debian (http://packages.debian.org/wheezy/),
+ and download the missing libraries. Note that the ``libXXX``
+ will have the shared objects (``.so``) and the ``libXXX-dev`` will
+ give you the headers and the static (``.a``) library. Just in
+ case, download both.
+
+ The ones you need for ARM are: ``libtinfo``, ``zlib1g``,
+ ``libxml2`` and ``liblzma``. In the Debian repository you'll
+ find downloads for all architectures.
+
+ After you download and unpack all ``.deb`` packages, copy all
+ ``.so`` and ``.a`` to a directory, make the appropriate
+ symbolic links (if necessary), and add the relevant ``-L``
+ and ``-I`` paths to ``-DCMAKE_CXX_FLAGS`` above.
+
+
+Running CMake and Building
+--------------------------
+
+Finally, if you're using your platform compiler, run:
+
+ .. code-block:: bash
+
+ $ cmake -G Ninja <source-dir> <options above>
+
+If you're using Clang as the cross-compiler, run:
+
+ .. code-block:: bash
+
+ $ CC='clang' CXX='clang++' cmake -G Ninja <source-dir> <options above>
+
+If you have ``clang``/``clang++`` on the path, it should just work, and special
+Ninja files will be created in the build directory. I strongly suggest
+you to run ``cmake`` on a separate build directory, *not* inside the
+source tree.
+
+To build, simply type:
+
+ .. code-block:: bash
+
+ $ ninja
+
+It should automatically find out how many cores you have, what are
+the rules that needs building and will build the whole thing.
+
+You can't run ``ninja check-all`` on this tree because the created
+binaries are targeted to ARM, not x86_64.
+
+Installing and Using
+--------------------
+
+After the LLVM/Clang has built successfully, you should install it
+via:
+
+ .. code-block:: bash
+
+ $ ninja install
+
+which will create a sysroot on the install-dir. You can then tar
+that directory into a binary with the full triple name (for easy
+identification), like:
+
+ .. code-block:: bash
+
+ $ ln -sf <install-dir> arm-linux-gnueabihf-clang
+ $ tar zchf arm-linux-gnueabihf-clang.tar.gz arm-linux-gnueabihf-clang
+
+If you copy that tarball to your target board, you'll be able to use
+it for running the test-suite, for example. Follow the guidelines at
+http://llvm.org/docs/lnt/quickstart.html, unpack the tarball in the
+test directory, and use options:
+
+ .. code-block:: bash
+
+ $ ./sandbox/bin/python sandbox/bin/lnt runtest nt \
+ --sandbox sandbox \
+ --test-suite `pwd`/test-suite \
+ --cc `pwd`/arm-linux-gnueabihf-clang/bin/clang \
+ --cxx `pwd`/arm-linux-gnueabihf-clang/bin/clang++
+
+Remember to add the ``-jN`` options to ``lnt`` to the number of CPUs
+on your board. Also, the path to your clang has to be absolute, so
+you'll need the `pwd` trick above.
Added: www-releases/trunk/3.6.2/docs/_sources/HowToReleaseLLVM.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/HowToReleaseLLVM.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/HowToReleaseLLVM.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/HowToReleaseLLVM.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,441 @@
+=================================
+How To Release LLVM To The Public
+=================================
+
+.. contents::
+ :local:
+ :depth: 1
+
+Introduction
+============
+
+This document contains information about successfully releasing LLVM ---
+including subprojects: e.g., ``clang`` and ``dragonegg`` --- to the public. It
+is the Release Manager's responsibility to ensure that a high quality build of
+LLVM is released.
+
+If you're looking for the document on how to test the release candidates and
+create the binary packages, please refer to the :doc:`ReleaseProcess` instead.
+
+.. _timeline:
+
+Release Timeline
+================
+
+LLVM is released on a time based schedule --- with major releases roughly
+every 6 months. In between major releases there may be dot releases.
+The release manager will determine if and when to make a dot release based
+on feedback from the community. Typically, dot releases should be made if
+there are large number of bug-fixes in the stable branch or a critical bug
+has been discovered that affects a large number of users.
+
+Unless otherwise stated, dot releases will follow the same procedure as
+major releases.
+
+The release process is roughly as follows:
+
+* Set code freeze and branch creation date for 6 months after last code freeze
+ date. Announce release schedule to the LLVM community and update the website.
+
+* Create release branch and begin release process.
+
+* Send out release candidate sources for first round of testing. Testing lasts
+ 7-10 days. During the first round of testing, any regressions found should be
+ fixed. Patches are merged from mainline into the release branch. Also, all
+ features need to be completed during this time. Any features not completed at
+ the end of the first round of testing will be removed or disabled for the
+ release.
+
+* Generate and send out the second release candidate sources. Only *critial*
+ bugs found during this testing phase will be fixed. Any bugs introduced by
+ merged patches will be fixed. If so a third round of testing is needed.
+
+* The release notes are updated.
+
+* Finally, release!
+
+The release process will be accelerated for dot releases. If the first round
+of testing finds no critical bugs and no regressions since the last major release,
+then additional rounds of testing will not be required.
+
+Release Process
+===============
+
+.. contents::
+ :local:
+
+Release Administrative Tasks
+----------------------------
+
+This section describes a few administrative tasks that need to be done for the
+release process to begin. Specifically, it involves:
+
+* Creating the release branch,
+
+* Setting version numbers, and
+
+* Tagging release candidates for the release team to begin testing.
+
+Create Release Branch
+^^^^^^^^^^^^^^^^^^^^^
+
+Branch the Subversion trunk using the following procedure:
+
+#. Remind developers that the release branching is imminent and to refrain from
+ committing patches that might break the build. E.g., new features, large
+ patches for works in progress, an overhaul of the type system, an exciting
+ new TableGen feature, etc.
+
+#. Verify that the current Subversion trunk is in decent shape by
+ examining nightly tester and buildbot results.
+
+#. Create the release branch for ``llvm``, ``clang``, the ``test-suite``, and
+ ``dragonegg`` from the last known good revision. The branch's name is
+ ``release_XY``, where ``X`` is the major and ``Y`` the minor release
+ numbers. The branches should be created using the following commands:
+
+ ::
+
+ $ svn copy https://llvm.org/svn/llvm-project/llvm/trunk \
+ https://llvm.org/svn/llvm-project/llvm/branches/release_XY
+
+ $ svn copy https://llvm.org/svn/llvm-project/cfe/trunk \
+ https://llvm.org/svn/llvm-project/cfe/branches/release_XY
+
+ $ svn copy https://llvm.org/svn/llvm-project/dragonegg/trunk \
+ https://llvm.org/svn/llvm-project/dragonegg/branches/release_XY
+
+ $ svn copy https://llvm.org/svn/llvm-project/test-suite/trunk \
+ https://llvm.org/svn/llvm-project/test-suite/branches/release_XY
+
+#. Advise developers that they may now check their patches into the Subversion
+ tree again.
+
+#. The Release Manager should switch to the release branch, because all changes
+ to the release will now be done in the branch. The easiest way to do this is
+ to grab a working copy using the following commands:
+
+ ::
+
+ $ svn co https://llvm.org/svn/llvm-project/llvm/branches/release_XY llvm-X.Y
+
+ $ svn co https://llvm.org/svn/llvm-project/cfe/branches/release_XY clang-X.Y
+
+ $ svn co https://llvm.org/svn/llvm-project/dragonegg/branches/release_XY dragonegg-X.Y
+
+ $ svn co https://llvm.org/svn/llvm-project/test-suite/branches/release_XY test-suite-X.Y
+
+Update LLVM Version
+^^^^^^^^^^^^^^^^^^^
+
+After creating the LLVM release branch, update the release branches'
+``autoconf`` and ``configure.ac`` versions from '``X.Ysvn``' to '``X.Y``'.
+Update it on mainline as well to be the next version ('``X.Y+1svn``').
+Regenerate the configure scripts for both ``llvm`` and the ``test-suite``.
+
+In addition, the version numbers of all the Bugzilla components must be updated
+for the next release.
+
+Build the LLVM Release Candidates
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Create release candidates for ``llvm``, ``clang``, ``dragonegg``, and the LLVM
+``test-suite`` by tagging the branch with the respective release candidate
+number. For instance, to create **Release Candidate 1** you would issue the
+following commands:
+
+::
+
+ $ svn mkdir https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XYZ
+ $ svn copy https://llvm.org/svn/llvm-project/llvm/branches/release_XY \
+ https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XYZ/rc1
+
+ $ svn mkdir https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_XYZ
+ $ svn copy https://llvm.org/svn/llvm-project/cfe/branches/release_XY \
+ https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_XYZ/rc1
+
+ $ svn mkdir https://llvm.org/svn/llvm-project/dragonegg/tags/RELEASE_XYZ
+ $ svn copy https://llvm.org/svn/llvm-project/dragonegg/branches/release_XY \
+ https://llvm.org/svn/llvm-project/dragonegg/tags/RELEASE_XYZ/rc1
+
+ $ svn mkdir https://llvm.org/svn/llvm-project/test-suite/tags/RELEASE_XYZ
+ $ svn copy https://llvm.org/svn/llvm-project/test-suite/branches/release_XY \
+ https://llvm.org/svn/llvm-project/test-suite/tags/RELEASE_XYZ/rc1
+
+Similarly, **Release Candidate 2** would be named ``RC2`` and so on. This keeps
+a permanent copy of the release candidate around for people to export and build
+as they wish. The final released sources will be tagged in the ``RELEASE_XYZ``
+directory as ``Final`` (c.f. :ref:`tag`).
+
+The Release Manager may supply pre-packaged source tarballs for users. This can
+be done with the following commands:
+
+::
+
+ $ svn export https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XYZ/rc1 llvm-X.Yrc1
+ $ svn export https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_XYZ/rc1 clang-X.Yrc1
+ $ svn export https://llvm.org/svn/llvm-project/dragonegg/tags/RELEASE_XYZ/rc1 dragonegg-X.Yrc1
+ $ svn export https://llvm.org/svn/llvm-project/test-suite/tags/RELEASE_XYZ/rc1 llvm-test-X.Yrc1
+
+ $ tar -cvf - llvm-X.Yrc1 | gzip > llvm-X.Yrc1.src.tar.gz
+ $ tar -cvf - clang-X.Yrc1 | gzip > clang-X.Yrc1.src.tar.gz
+ $ tar -cvf - dragonegg-X.Yrc1 | gzip > dragonegg-X.Yrc1.src.tar.gz
+ $ tar -cvf - llvm-test-X.Yrc1 | gzip > llvm-test-X.Yrc1.src.tar.gz
+
+Building the Release
+--------------------
+
+The builds of ``llvm``, ``clang``, and ``dragonegg`` *must* be free of
+errors and warnings in Debug, Release+Asserts, and Release builds. If all
+builds are clean, then the release passes Build Qualification.
+
+The ``make`` options for building the different modes:
+
++-----------------+---------------------------------------------+
+| Mode | Options |
++=================+=============================================+
+| Debug | ``ENABLE_OPTIMIZED=0`` |
++-----------------+---------------------------------------------+
+| Release+Asserts | ``ENABLE_OPTIMIZED=1`` |
++-----------------+---------------------------------------------+
+| Release | ``ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1`` |
++-----------------+---------------------------------------------+
+
+Build LLVM
+^^^^^^^^^^
+
+Build ``Debug``, ``Release+Asserts``, and ``Release`` versions
+of ``llvm`` on all supported platforms. Directions to build ``llvm``
+are :doc:`here <GettingStarted>`.
+
+Build Clang Binary Distribution
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Creating the ``clang`` binary distribution (Debug/Release+Asserts/Release)
+requires performing the following steps for each supported platform:
+
+#. Build clang according to the directions `here
+ <http://clang.llvm.org/get_started.html>`__.
+
+#. Build both a Debug and Release version of clang. The binary will be the
+ Release build.
+
+#. Package ``clang`` (details to follow).
+
+Target Specific Build Details
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The table below specifies which compilers are used for each Arch/OS combination
+when qualifying the build of ``llvm``, ``clang``, and ``dragonegg``.
+
++--------------+---------------+----------------------+
+| Architecture | OS | compiler |
++==============+===============+======================+
+| x86-32 | Mac OS 10.5 | gcc 4.0.1 |
++--------------+---------------+----------------------+
+| x86-32 | Linux | gcc 4.2.X, gcc 4.3.X |
++--------------+---------------+----------------------+
+| x86-32 | FreeBSD | gcc 4.2.X |
++--------------+---------------+----------------------+
+| x86-32 | mingw | gcc 3.4.5 |
++--------------+---------------+----------------------+
+| x86-64 | Mac OS 10.5 | gcc 4.0.1 |
++--------------+---------------+----------------------+
+| x86-64 | Linux | gcc 4.2.X, gcc 4.3.X |
++--------------+---------------+----------------------+
+| x86-64 | FreeBSD | gcc 4.2.X |
++--------------+---------------+----------------------+
+| ARMv7 | Linux | gcc 4.6.X, gcc 4.7.X |
++--------------+---------------+----------------------+
+
+Release Qualification Criteria
+------------------------------
+
+A release is qualified when it has no regressions from the previous release (or
+baseline). Regressions are related to correctness first and performance second.
+(We may tolerate some minor performance regressions if they are deemed
+necessary for the general quality of the compiler.)
+
+**Regressions are new failures in the set of tests that are used to qualify
+each product and only include things on the list. Every release will have
+some bugs in it. It is the reality of developing a complex piece of
+software. We need a very concrete and definitive release criteria that
+ensures we have monotonically improving quality on some metric. The metric we
+use is described below. This doesn't mean that we don't care about other
+criteria, but these are the criteria which we found to be most important and
+which must be satisfied before a release can go out.**
+
+Qualify LLVM
+^^^^^^^^^^^^
+
+LLVM is qualified when it has a clean test run without a front-end. And it has
+no regressions when using either ``clang`` or ``dragonegg`` with the
+``test-suite`` from the previous release.
+
+Qualify Clang
+^^^^^^^^^^^^^
+
+``Clang`` is qualified when front-end specific tests in the ``llvm`` regression
+test suite all pass, clang's own test suite passes cleanly, and there are no
+regressions in the ``test-suite``.
+
+Specific Target Qualification Details
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
++--------------+-------------+----------------+-----------------------------+
+| Architecture | OS | clang baseline | tests |
++==============+=============+================+=============================+
+| x86-32 | Linux | last release | llvm regression tests, |
+| | | | clang regression tests, |
+| | | | test-suite (including spec) |
++--------------+-------------+----------------+-----------------------------+
+| x86-32 | FreeBSD | last release | llvm regression tests, |
+| | | | clang regression tests, |
+| | | | test-suite |
++--------------+-------------+----------------+-----------------------------+
+| x86-32 | mingw | none | QT |
++--------------+-------------+----------------+-----------------------------+
+| x86-64 | Mac OS 10.X | last release | llvm regression tests, |
+| | | | clang regression tests, |
+| | | | test-suite (including spec) |
++--------------+-------------+----------------+-----------------------------+
+| x86-64 | Linux | last release | llvm regression tests, |
+| | | | clang regression tests, |
+| | | | test-suite (including spec) |
++--------------+-------------+----------------+-----------------------------+
+| x86-64 | FreeBSD | last release | llvm regression tests, |
+| | | | clang regression tests, |
+| | | | test-suite |
++--------------+-------------+----------------+-----------------------------+
+| ARMv7A | Linux | last release | llvm regression tests, |
+| | | | clang regression tests, |
+| | | | test-suite |
++--------------+-------------+----------------+-----------------------------+
+
+Community Testing
+-----------------
+
+Once all testing has been completed and appropriate bugs filed, the release
+candidate tarballs are put on the website and the LLVM community is notified.
+Ask that all LLVM developers test the release in 2 ways:
+
+#. Download ``llvm-X.Y``, ``llvm-test-X.Y``, and the appropriate ``clang``
+ binary. Build LLVM. Run ``make check`` and the full LLVM test suite (``make
+ TEST=nightly report``).
+
+#. Download ``llvm-X.Y``, ``llvm-test-X.Y``, and the ``clang`` sources. Compile
+ everything. Run ``make check`` and the full LLVM test suite (``make
+ TEST=nightly report``).
+
+Ask LLVM developers to submit the test suite report and ``make check`` results
+to the list. Verify that there are no regressions from the previous release.
+The results are not used to qualify a release, but to spot other potential
+problems. For unsupported targets, verify that ``make check`` is at least
+clean.
+
+During the first round of testing, all regressions must be fixed before the
+second release candidate is tagged.
+
+If this is the second round of testing, the testing is only to ensure that bug
+fixes previously merged in have not created new major problems. *This is not
+the time to solve additional and unrelated bugs!* If no patches are merged in,
+the release is determined to be ready and the release manager may move onto the
+next stage.
+
+Release Patch Rules
+-------------------
+
+Below are the rules regarding patching the release branch:
+
+#. Patches applied to the release branch may only be applied by the release
+ manager.
+
+#. During the first round of testing, patches that fix regressions or that are
+ small and relatively risk free (verified by the appropriate code owner) are
+ applied to the branch. Code owners are asked to be very conservative in
+ approving patches for the branch. We reserve the right to reject any patch
+ that does not fix a regression as previously defined.
+
+#. During the remaining rounds of testing, only patches that fix critical
+ regressions may be applied.
+
+#. For dot releases all patches must mantain both API and ABI compatibility with
+ the previous major release. Only bugfixes will be accepted.
+
+Release Final Tasks
+-------------------
+
+The final stages of the release process involves tagging the "final" release
+branch, updating documentation that refers to the release, and updating the
+demo page.
+
+Update Documentation
+^^^^^^^^^^^^^^^^^^^^
+
+Review the documentation and ensure that it is up to date. The "Release Notes"
+must be updated to reflect new features, bug fixes, new known issues, and
+changes in the list of supported platforms. The "Getting Started Guide" should
+be updated to reflect the new release version number tag available from
+Subversion and changes in basic system requirements. Merge both changes from
+mainline into the release branch.
+
+.. _tag:
+
+Tag the LLVM Final Release
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Tag the final release sources using the following procedure:
+
+::
+
+ $ svn copy https://llvm.org/svn/llvm-project/llvm/branches/release_XY \
+ https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_XYZ/Final
+
+ $ svn copy https://llvm.org/svn/llvm-project/cfe/branches/release_XY \
+ https://llvm.org/svn/llvm-project/cfe/tags/RELEASE_XYZ/Final
+
+ $ svn copy https://llvm.org/svn/llvm-project/dragonegg/branches/release_XY \
+ https://llvm.org/svn/llvm-project/dragonegg/tags/RELEASE_XYZ/Final
+
+ $ svn copy https://llvm.org/svn/llvm-project/test-suite/branches/release_XY \
+ https://llvm.org/svn/llvm-project/test-suite/tags/RELEASE_XYZ/Final
+
+Update the LLVM Demo Page
+-------------------------
+
+The LLVM demo page must be updated to use the new release. This consists of
+using the new ``clang`` binary and building LLVM.
+
+Update the LLVM Website
+^^^^^^^^^^^^^^^^^^^^^^^
+
+The website must be updated before the release announcement is sent out. Here
+is what to do:
+
+#. Check out the ``www`` module from Subversion.
+
+#. Create a new subdirectory ``X.Y`` in the releases directory.
+
+#. Commit the ``llvm``, ``test-suite``, ``clang`` source, ``clang binaries``,
+ ``dragonegg`` source, and ``dragonegg`` binaries in this new directory.
+
+#. Copy and commit the ``llvm/docs`` and ``LICENSE.txt`` files into this new
+ directory. The docs should be built with ``BUILD_FOR_WEBSITE=1``.
+
+#. Commit the ``index.html`` to the ``release/X.Y`` directory to redirect (use
+ from previous release).
+
+#. Update the ``releases/download.html`` file with the new release.
+
+#. Update the ``releases/index.html`` with the new release and link to release
+ documentation.
+
+#. Finally, update the main page (``index.html`` and sidebar) to point to the
+ new release and release announcement. Make sure this all gets committed back
+ into Subversion.
+
+Announce the Release
+^^^^^^^^^^^^^^^^^^^^
+
+Have Chris send out the release announcement when everything is finished.
+
Added: www-releases/trunk/3.6.2/docs/_sources/HowToSetUpLLVMStyleRTTI.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/HowToSetUpLLVMStyleRTTI.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/HowToSetUpLLVMStyleRTTI.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/HowToSetUpLLVMStyleRTTI.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,400 @@
+======================================================
+How to set up LLVM-style RTTI for your class hierarchy
+======================================================
+
+.. contents::
+
+Background
+==========
+
+LLVM avoids using C++'s built in RTTI. Instead, it pervasively uses its
+own hand-rolled form of RTTI which is much more efficient and flexible,
+although it requires a bit more work from you as a class author.
+
+A description of how to use LLVM-style RTTI from a client's perspective is
+given in the `Programmer's Manual <ProgrammersManual.html#isa>`_. This
+document, in contrast, discusses the steps you need to take as a class
+hierarchy author to make LLVM-style RTTI available to your clients.
+
+Before diving in, make sure that you are familiar with the Object Oriented
+Programming concept of "`is-a`_".
+
+.. _is-a: http://en.wikipedia.org/wiki/Is-a
+
+Basic Setup
+===========
+
+This section describes how to set up the most basic form of LLVM-style RTTI
+(which is sufficient for 99.9% of the cases). We will set up LLVM-style
+RTTI for this class hierarchy:
+
+.. code-block:: c++
+
+ class Shape {
+ public:
+ Shape() {}
+ virtual double computeArea() = 0;
+ };
+
+ class Square : public Shape {
+ double SideLength;
+ public:
+ Square(double S) : SideLength(S) {}
+ double computeArea() /* override */;
+ };
+
+ class Circle : public Shape {
+ double Radius;
+ public:
+ Circle(double R) : Radius(R) {}
+ double computeArea() /* override */;
+ };
+
+The most basic working setup for LLVM-style RTTI requires the following
+steps:
+
+#. In the header where you declare ``Shape``, you will want to ``#include
+ "llvm/Support/Casting.h"``, which declares LLVM's RTTI templates. That
+ way your clients don't even have to think about it.
+
+ .. code-block:: c++
+
+ #include "llvm/Support/Casting.h"
+
+#. In the base class, introduce an enum which discriminates all of the
+ different concrete classes in the hierarchy, and stash the enum value
+ somewhere in the base class.
+
+ Here is the code after introducing this change:
+
+ .. code-block:: c++
+
+ class Shape {
+ public:
+ + /// Discriminator for LLVM-style RTTI (dyn_cast<> et al.)
+ + enum ShapeKind {
+ + SK_Square,
+ + SK_Circle
+ + };
+ +private:
+ + const ShapeKind Kind;
+ +public:
+ + ShapeKind getKind() const { return Kind; }
+ +
+ Shape() {}
+ virtual double computeArea() = 0;
+ };
+
+ You will usually want to keep the ``Kind`` member encapsulated and
+ private, but let the enum ``ShapeKind`` be public along with providing a
+ ``getKind()`` method. This is convenient for clients so that they can do
+ a ``switch`` over the enum.
+
+ A common naming convention is that these enums are "kind"s, to avoid
+ ambiguity with the words "type" or "class" which have overloaded meanings
+ in many contexts within LLVM. Sometimes there will be a natural name for
+ it, like "opcode". Don't bikeshed over this; when in doubt use ``Kind``.
+
+ You might wonder why the ``Kind`` enum doesn't have an entry for
+ ``Shape``. The reason for this is that since ``Shape`` is abstract
+ (``computeArea() = 0;``), you will never actually have non-derived
+ instances of exactly that class (only subclasses). See `Concrete Bases
+ and Deeper Hierarchies`_ for information on how to deal with
+ non-abstract bases. It's worth mentioning here that unlike
+ ``dynamic_cast<>``, LLVM-style RTTI can be used (and is often used) for
+ classes that don't have v-tables.
+
+#. Next, you need to make sure that the ``Kind`` gets initialized to the
+ value corresponding to the dynamic type of the class. Typically, you will
+ want to have it be an argument to the constructor of the base class, and
+ then pass in the respective ``XXXKind`` from subclass constructors.
+
+ Here is the code after that change:
+
+ .. code-block:: c++
+
+ class Shape {
+ public:
+ /// Discriminator for LLVM-style RTTI (dyn_cast<> et al.)
+ enum ShapeKind {
+ SK_Square,
+ SK_Circle
+ };
+ private:
+ const ShapeKind Kind;
+ public:
+ ShapeKind getKind() const { return Kind; }
+
+ - Shape() {}
+ + Shape(ShapeKind K) : Kind(K) {}
+ virtual double computeArea() = 0;
+ };
+
+ class Square : public Shape {
+ double SideLength;
+ public:
+ - Square(double S) : SideLength(S) {}
+ + Square(double S) : Shape(SK_Square), SideLength(S) {}
+ double computeArea() /* override */;
+ };
+
+ class Circle : public Shape {
+ double Radius;
+ public:
+ - Circle(double R) : Radius(R) {}
+ + Circle(double R) : Shape(SK_Circle), Radius(R) {}
+ double computeArea() /* override */;
+ };
+
+#. Finally, you need to inform LLVM's RTTI templates how to dynamically
+ determine the type of a class (i.e. whether the ``isa<>``/``dyn_cast<>``
+ should succeed). The default "99.9% of use cases" way to accomplish this
+ is through a small static member function ``classof``. In order to have
+ proper context for an explanation, we will display this code first, and
+ then below describe each part:
+
+ .. code-block:: c++
+
+ class Shape {
+ public:
+ /// Discriminator for LLVM-style RTTI (dyn_cast<> et al.)
+ enum ShapeKind {
+ SK_Square,
+ SK_Circle
+ };
+ private:
+ const ShapeKind Kind;
+ public:
+ ShapeKind getKind() const { return Kind; }
+
+ Shape(ShapeKind K) : Kind(K) {}
+ virtual double computeArea() = 0;
+ };
+
+ class Square : public Shape {
+ double SideLength;
+ public:
+ Square(double S) : Shape(SK_Square), SideLength(S) {}
+ double computeArea() /* override */;
+ +
+ + static bool classof(const Shape *S) {
+ + return S->getKind() == SK_Square;
+ + }
+ };
+
+ class Circle : public Shape {
+ double Radius;
+ public:
+ Circle(double R) : Shape(SK_Circle), Radius(R) {}
+ double computeArea() /* override */;
+ +
+ + static bool classof(const Shape *S) {
+ + return S->getKind() == SK_Circle;
+ + }
+ };
+
+ The job of ``classof`` is to dynamically determine whether an object of
+ a base class is in fact of a particular derived class. In order to
+ downcast a type ``Base`` to a type ``Derived``, there needs to be a
+ ``classof`` in ``Derived`` which will accept an object of type ``Base``.
+
+ To be concrete, consider the following code:
+
+ .. code-block:: c++
+
+ Shape *S = ...;
+ if (isa<Circle>(S)) {
+ /* do something ... */
+ }
+
+ The code of the ``isa<>`` test in this code will eventually boil
+ down---after template instantiation and some other machinery---to a
+ check roughly like ``Circle::classof(S)``. For more information, see
+ :ref:`classof-contract`.
+
+ The argument to ``classof`` should always be an *ancestor* class because
+ the implementation has logic to allow and optimize away
+ upcasts/up-``isa<>``'s automatically. It is as though every class
+ ``Foo`` automatically has a ``classof`` like:
+
+ .. code-block:: c++
+
+ class Foo {
+ [...]
+ template <class T>
+ static bool classof(const T *,
+ ::std::enable_if<
+ ::std::is_base_of<Foo, T>::value
+ >::type* = 0) { return true; }
+ [...]
+ };
+
+ Note that this is the reason that we did not need to introduce a
+ ``classof`` into ``Shape``: all relevant classes derive from ``Shape``,
+ and ``Shape`` itself is abstract (has no entry in the ``Kind`` enum),
+ so this notional inferred ``classof`` is all we need. See `Concrete
+ Bases and Deeper Hierarchies`_ for more information about how to extend
+ this example to more general hierarchies.
+
+Although for this small example setting up LLVM-style RTTI seems like a lot
+of "boilerplate", if your classes are doing anything interesting then this
+will end up being a tiny fraction of the code.
+
+Concrete Bases and Deeper Hierarchies
+=====================================
+
+For concrete bases (i.e. non-abstract interior nodes of the inheritance
+tree), the ``Kind`` check inside ``classof`` needs to be a bit more
+complicated. The situation differs from the example above in that
+
+* Since the class is concrete, it must itself have an entry in the ``Kind``
+ enum because it is possible to have objects with this class as a dynamic
+ type.
+
+* Since the class has children, the check inside ``classof`` must take them
+ into account.
+
+Say that ``SpecialSquare`` and ``OtherSpecialSquare`` derive
+from ``Square``, and so ``ShapeKind`` becomes:
+
+.. code-block:: c++
+
+ enum ShapeKind {
+ SK_Square,
+ + SK_SpecialSquare,
+ + SK_OtherSpecialSquare,
+ SK_Circle
+ }
+
+Then in ``Square``, we would need to modify the ``classof`` like so:
+
+.. code-block:: c++
+
+ - static bool classof(const Shape *S) {
+ - return S->getKind() == SK_Square;
+ - }
+ + static bool classof(const Shape *S) {
+ + return S->getKind() >= SK_Square &&
+ + S->getKind() <= SK_OtherSpecialSquare;
+ + }
+
+The reason that we need to test a range like this instead of just equality
+is that both ``SpecialSquare`` and ``OtherSpecialSquare`` "is-a"
+``Square``, and so ``classof`` needs to return ``true`` for them.
+
+This approach can be made to scale to arbitrarily deep hierarchies. The
+trick is that you arrange the enum values so that they correspond to a
+preorder traversal of the class hierarchy tree. With that arrangement, all
+subclass tests can be done with two comparisons as shown above. If you just
+list the class hierarchy like a list of bullet points, you'll get the
+ordering right::
+
+ | Shape
+ | Square
+ | SpecialSquare
+ | OtherSpecialSquare
+ | Circle
+
+A Bug to be Aware Of
+--------------------
+
+The example just given opens the door to bugs where the ``classof``\s are
+not updated to match the ``Kind`` enum when adding (or removing) classes to
+(from) the hierarchy.
+
+Continuing the example above, suppose we add a ``SomewhatSpecialSquare`` as
+a subclass of ``Square``, and update the ``ShapeKind`` enum like so:
+
+.. code-block:: c++
+
+ enum ShapeKind {
+ SK_Square,
+ SK_SpecialSquare,
+ SK_OtherSpecialSquare,
+ + SK_SomewhatSpecialSquare,
+ SK_Circle
+ }
+
+Now, suppose that we forget to update ``Square::classof()``, so it still
+looks like:
+
+.. code-block:: c++
+
+ static bool classof(const Shape *S) {
+ // BUG: Returns false when S->getKind() == SK_SomewhatSpecialSquare,
+ // even though SomewhatSpecialSquare "is a" Square.
+ return S->getKind() >= SK_Square &&
+ S->getKind() <= SK_OtherSpecialSquare;
+ }
+
+As the comment indicates, this code contains a bug. A straightforward and
+non-clever way to avoid this is to introduce an explicit ``SK_LastSquare``
+entry in the enum when adding the first subclass(es). For example, we could
+rewrite the example at the beginning of `Concrete Bases and Deeper
+Hierarchies`_ as:
+
+.. code-block:: c++
+
+ enum ShapeKind {
+ SK_Square,
+ + SK_SpecialSquare,
+ + SK_OtherSpecialSquare,
+ + SK_LastSquare,
+ SK_Circle
+ }
+ ...
+ // Square::classof()
+ - static bool classof(const Shape *S) {
+ - return S->getKind() == SK_Square;
+ - }
+ + static bool classof(const Shape *S) {
+ + return S->getKind() >= SK_Square &&
+ + S->getKind() <= SK_LastSquare;
+ + }
+
+Then, adding new subclasses is easy:
+
+.. code-block:: c++
+
+ enum ShapeKind {
+ SK_Square,
+ SK_SpecialSquare,
+ SK_OtherSpecialSquare,
+ + SK_SomewhatSpecialSquare,
+ SK_LastSquare,
+ SK_Circle
+ }
+
+Notice that ``Square::classof`` does not need to be changed.
+
+.. _classof-contract:
+
+The Contract of ``classof``
+---------------------------
+
+To be more precise, let ``classof`` be inside a class ``C``. Then the
+contract for ``classof`` is "return ``true`` if the dynamic type of the
+argument is-a ``C``". As long as your implementation fulfills this
+contract, you can tweak and optimize it as much as you want.
+
+.. TODO::
+
+ Touch on some of the more advanced features, like ``isa_impl`` and
+ ``simplify_type``. However, those two need reference documentation in
+ the form of doxygen comments as well. We need the doxygen so that we can
+ say "for full details, see http://llvm.org/doxygen/..."
+
+Rules of Thumb
+==============
+
+#. The ``Kind`` enum should have one entry per concrete class, ordered
+ according to a preorder traversal of the inheritance tree.
+#. The argument to ``classof`` should be a ``const Base *``, where ``Base``
+ is some ancestor in the inheritance hierarchy. The argument should
+ *never* be a derived class or the class itself: the template machinery
+ for ``isa<>`` already handles this case and optimizes it.
+#. For each class in the hierarchy that has no children, implement a
+ ``classof`` that checks only against its ``Kind``.
+#. For each class in the hierarchy that has children, implement a
+ ``classof`` that checks a range of the first child's ``Kind`` and the
+ last child's ``Kind``.
Added: www-releases/trunk/3.6.2/docs/_sources/HowToSubmitABug.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/HowToSubmitABug.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/HowToSubmitABug.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/HowToSubmitABug.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,229 @@
+================================
+How to submit an LLVM bug report
+================================
+
+Introduction - Got bugs?
+========================
+
+
+If you're working with LLVM and run into a bug, we definitely want to know
+about it. This document describes what you can do to increase the odds of
+getting it fixed quickly.
+
+Basically you have to do two things at a minimum. First, decide whether
+the bug `crashes the compiler`_ (or an LLVM pass), or if the
+compiler is `miscompiling`_ the program (i.e., the
+compiler successfully produces an executable, but it doesn't run right).
+Based on what type of bug it is, follow the instructions in the linked
+section to narrow down the bug so that the person who fixes it will be able
+to find the problem more easily.
+
+Once you have a reduced test-case, go to `the LLVM Bug Tracking System
+<http://llvm.org/bugs/enter_bug.cgi>`_ and fill out the form with the
+necessary details (note that you don't need to pick a category, just use
+the "new-bugs" category if you're not sure). The bug description should
+contain the following information:
+
+* All information necessary to reproduce the problem.
+* The reduced test-case that triggers the bug.
+* The location where you obtained LLVM (if not from our Subversion
+ repository).
+
+Thanks for helping us make LLVM better!
+
+.. _crashes the compiler:
+
+Crashing Bugs
+=============
+
+More often than not, bugs in the compiler cause it to crash---often due to
+an assertion failure of some sort. The most important piece of the puzzle
+is to figure out if it is crashing in the GCC front-end or if it is one of
+the LLVM libraries (e.g. the optimizer or code generator) that has
+problems.
+
+To figure out which component is crashing (the front-end, optimizer or code
+generator), run the ``clang`` command line as you were when the crash
+occurred, but with the following extra command line options:
+
+* ``-O0 -emit-llvm``: If ``clang`` still crashes when passed these
+ options (which disable the optimizer and code generator), then the crash
+ is in the front-end. Jump ahead to the section on :ref:`front-end bugs
+ <front-end>`.
+
+* ``-emit-llvm``: If ``clang`` crashes with this option (which disables
+ the code generator), you found an optimizer bug. Jump ahead to
+ `compile-time optimization bugs`_.
+
+* Otherwise, you have a code generator crash. Jump ahead to `code
+ generator bugs`_.
+
+.. _front-end bug:
+.. _front-end:
+
+Front-end bugs
+--------------
+
+If the problem is in the front-end, you should re-run the same ``clang``
+command that resulted in the crash, but add the ``-save-temps`` option.
+The compiler will crash again, but it will leave behind a ``foo.i`` file
+(containing preprocessed C source code) and possibly ``foo.s`` for each
+compiled ``foo.c`` file. Send us the ``foo.i`` file, along with the options
+you passed to ``clang``, and a brief description of the error it caused.
+
+The `delta <http://delta.tigris.org/>`_ tool helps to reduce the
+preprocessed file down to the smallest amount of code that still replicates
+the problem. You're encouraged to use delta to reduce the code to make the
+developers' lives easier. `This website
+<http://gcc.gnu.org/wiki/A_guide_to_testcase_reduction>`_ has instructions
+on the best way to use delta.
+
+.. _compile-time optimization bugs:
+
+Compile-time optimization bugs
+------------------------------
+
+If you find that a bug crashes in the optimizer, compile your test-case to a
+``.bc`` file by passing "``-emit-llvm -O0 -c -o foo.bc``".
+Then run:
+
+.. code-block:: bash
+
+ opt -O3 -debug-pass=Arguments foo.bc -disable-output
+
+This command should do two things: it should print out a list of passes, and
+then it should crash in the same way as clang. If it doesn't crash, please
+follow the instructions for a `front-end bug`_.
+
+If this does crash, then you should be able to debug this with the following
+bugpoint command:
+
+.. code-block:: bash
+
+ bugpoint foo.bc <list of passes printed by opt>
+
+Please run this, then file a bug with the instructions and reduced .bc
+files that bugpoint emits. If something goes wrong with bugpoint, please
+submit the "foo.bc" file and the list of passes printed by ``opt``.
+
+.. _code generator bugs:
+
+Code generator bugs
+-------------------
+
+If you find a bug that crashes clang in the code generator, compile your
+source file to a .bc file by passing "``-emit-llvm -c -o foo.bc``" to
+clang (in addition to the options you already pass). Once your have
+foo.bc, one of the following commands should fail:
+
+#. ``llc foo.bc``
+#. ``llc foo.bc -relocation-model=pic``
+#. ``llc foo.bc -relocation-model=static``
+
+If none of these crash, please follow the instructions for a `front-end
+bug`_. If one of these do crash, you should be able to reduce this with
+one of the following bugpoint command lines (use the one corresponding to
+the command above that failed):
+
+#. ``bugpoint -run-llc foo.bc``
+#. ``bugpoint -run-llc foo.bc --tool-args -relocation-model=pic``
+#. ``bugpoint -run-llc foo.bc --tool-args -relocation-model=static``
+
+Please run this, then file a bug with the instructions and reduced .bc file
+that bugpoint emits. If something goes wrong with bugpoint, please submit
+the "foo.bc" file and the option that llc crashes with.
+
+.. _miscompiling:
+
+Miscompilations
+===============
+
+If clang successfully produces an executable, but that executable
+doesn't run right, this is either a bug in the code or a bug in the
+compiler. The first thing to check is to make sure it is not using
+undefined behavior (e.g. reading a variable before it is defined). In
+particular, check to see if the program `valgrind
+<http://valgrind.org/>`_'s clean, passes purify, or some other memory
+checker tool. Many of the "LLVM bugs" that we have chased down ended up
+being bugs in the program being compiled, not LLVM.
+
+Once you determine that the program itself is not buggy, you should choose
+which code generator you wish to compile the program with (e.g. LLC or the JIT)
+and optionally a series of LLVM passes to run. For example:
+
+.. code-block:: bash
+
+ bugpoint -run-llc [... optzn passes ...] file-to-test.bc --args -- [program arguments]
+
+bugpoint will try to narrow down your list of passes to the one pass that
+causes an error, and simplify the bitcode file as much as it can to assist
+you. It will print a message letting you know how to reproduce the
+resulting error.
+
+Incorrect code generation
+=========================
+
+Similarly to debugging incorrect compilation by mis-behaving passes, you
+can debug incorrect code generation by either LLC or the JIT, using
+``bugpoint``. The process ``bugpoint`` follows in this case is to try to
+narrow the code down to a function that is miscompiled by one or the other
+method, but since for correctness, the entire program must be run,
+``bugpoint`` will compile the code it deems to not be affected with the C
+Backend, and then link in the shared object it generates.
+
+To debug the JIT:
+
+.. code-block:: bash
+
+ bugpoint -run-jit -output=[correct output file] [bitcode file] \
+ --tool-args -- [arguments to pass to lli] \
+ --args -- [program arguments]
+
+Similarly, to debug the LLC, one would run:
+
+.. code-block:: bash
+
+ bugpoint -run-llc -output=[correct output file] [bitcode file] \
+ --tool-args -- [arguments to pass to llc] \
+ --args -- [program arguments]
+
+**Special note:** if you are debugging MultiSource or SPEC tests that
+already exist in the ``llvm/test`` hierarchy, there is an easier way to
+debug the JIT, LLC, and CBE, using the pre-written Makefile targets, which
+will pass the program options specified in the Makefiles:
+
+.. code-block:: bash
+
+ cd llvm/test/../../program
+ make bugpoint-jit
+
+At the end of a successful ``bugpoint`` run, you will be presented
+with two bitcode files: a *safe* file which can be compiled with the C
+backend and the *test* file which either LLC or the JIT
+mis-codegenerates, and thus causes the error.
+
+To reproduce the error that ``bugpoint`` found, it is sufficient to do
+the following:
+
+#. Regenerate the shared object from the safe bitcode file:
+
+ .. code-block:: bash
+
+ llc -march=c safe.bc -o safe.c
+ gcc -shared safe.c -o safe.so
+
+#. If debugging LLC, compile test bitcode native and link with the shared
+ object:
+
+ .. code-block:: bash
+
+ llc test.bc -o test.s
+ gcc test.s safe.so -o test.llc
+ ./test.llc [program options]
+
+#. If debugging the JIT, load the shared object and supply the test
+ bitcode:
+
+ .. code-block:: bash
+
+ lli -load=safe.so test.bc [program options]
Added: www-releases/trunk/3.6.2/docs/_sources/HowToUseAttributes.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/HowToUseAttributes.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/HowToUseAttributes.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/HowToUseAttributes.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,81 @@
+=====================
+How To Use Attributes
+=====================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+Attributes in LLVM have changed in some fundamental ways. It was necessary to
+do this to support expanding the attributes to encompass more than a handful of
+attributes --- e.g. command line options. The old way of handling attributes
+consisted of representing them as a bit mask of values. This bit mask was
+stored in a "list" structure that was reference counted. The advantage of this
+was that attributes could be manipulated with 'or's and 'and's. The
+disadvantage of this was that there was limited room for expansion, and
+virtually no support for attribute-value pairs other than alignment.
+
+In the new scheme, an ``Attribute`` object represents a single attribute that's
+uniqued. You use the ``Attribute::get`` methods to create a new ``Attribute``
+object. An attribute can be a single "enum" value (the enum being the
+``Attribute::AttrKind`` enum), a string representing a target-dependent
+attribute, or an attribute-value pair. Some examples:
+
+* Target-independent: ``noinline``, ``zext``
+* Target-dependent: ``"no-sse"``, ``"thumb2"``
+* Attribute-value pair: ``"cpu" = "cortex-a8"``, ``align = 4``
+
+Note: for an attribute value pair, we expect a target-dependent attribute to
+have a string for the value.
+
+``Attribute``
+=============
+An ``Attribute`` object is designed to be passed around by value.
+
+Because attributes are no longer represented as a bit mask, you will need to
+convert any code which does treat them as a bit mask to use the new query
+methods on the Attribute class.
+
+``AttributeSet``
+================
+
+The ``AttributeSet`` class replaces the old ``AttributeList`` class. The
+``AttributeSet`` stores a collection of Attribute objects for each kind of
+object that may have an attribute associated with it: the function as a
+whole, the return type, or the function's parameters. A function's attributes
+are at index ``AttributeSet::FunctionIndex``; the return type's attributes are
+at index ``AttributeSet::ReturnIndex``; and the function's parameters'
+attributes are at indices 1, ..., n (where 'n' is the number of parameters).
+Most methods on the ``AttributeSet`` class take an index parameter.
+
+An ``AttributeSet`` is also a uniqued and immutable object. You create an
+``AttributeSet`` through the ``AttributeSet::get`` methods. You can add and
+remove attributes, which result in the creation of a new ``AttributeSet``.
+
+An ``AttributeSet`` object is designed to be passed around by value.
+
+Note: It is advised that you do *not* use the ``AttributeSet`` "introspection"
+methods (e.g. ``Raw``, ``getRawPointer``, etc.). These methods break
+encapsulation, and may be removed in a future release (i.e. LLVM 4.0).
+
+``AttrBuilder``
+===============
+
+Lastly, we have a "builder" class to help create the ``AttributeSet`` object
+without having to create several different intermediate uniqued
+``AttributeSet`` objects. The ``AttrBuilder`` class allows you to add and
+remove attributes at will. The attributes won't be uniqued until you call the
+appropriate ``AttributeSet::get`` method.
+
+An ``AttrBuilder`` object is *not* designed to be passed around by value. It
+should be passed by reference.
+
+Note: It is advised that you do *not* use the ``AttrBuilder::addRawValue()``
+method or the ``AttrBuilder(uint64_t Val)`` constructor. These are for
+backwards compatibility and may be removed in a future release (i.e. LLVM 4.0).
+
+And that's basically it! A lot of functionality is hidden behind these classes,
+but the interfaces are pretty straight forward.
+
Added: www-releases/trunk/3.6.2/docs/_sources/HowToUseInstrMappings.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/HowToUseInstrMappings.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/HowToUseInstrMappings.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/HowToUseInstrMappings.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,175 @@
+===============================
+How To Use Instruction Mappings
+===============================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+This document contains information about adding instruction mapping support
+for a target. The motivation behind this feature comes from the need to switch
+between different instruction formats during various optimizations. One approach
+could be to use switch cases which list all the instructions along with formats
+they can transition to. However, it has large maintenance overhead
+because of the hardcoded instruction names. Also, whenever a new instruction is
+added in the .td files, all the relevant switch cases should be modified
+accordingly. Instead, the same functionality could be achieved with TableGen and
+some support from the .td files for a fraction of maintenance cost.
+
+``InstrMapping`` Class Overview
+===============================
+
+TableGen uses relationship models to map instructions with each other. These
+models are described using ``InstrMapping`` class as a base. Each model sets
+various fields of the ``InstrMapping`` class such that they can uniquely
+describe all the instructions using that model. TableGen parses all the relation
+models and uses the information to construct relation tables which relate
+instructions with each other. These tables are emitted in the
+``XXXInstrInfo.inc`` file along with the functions to query them. Following
+is the definition of ``InstrMapping`` class definied in Target.td file:
+
+.. code-block:: llvm
+
+ class InstrMapping {
+ // Used to reduce search space only to the instructions using this
+ // relation model.
+ string FilterClass;
+
+ // List of fields/attributes that should be same for all the instructions in
+ // a row of the relation table. Think of this as a set of properties shared
+ // by all the instructions related by this relationship.
+ list<string> RowFields = [];
+
+ // List of fields/attributes that are same for all the instructions
+ // in a column of the relation table.
+ list<string> ColFields = [];
+
+ // Values for the fields/attributes listed in 'ColFields' corresponding to
+ // the key instruction. This is the instruction that will be transformed
+ // using this relation model.
+ list<string> KeyCol = [];
+
+ // List of values for the fields/attributes listed in 'ColFields', one for
+ // each column in the relation table. These are the instructions a key
+ // instruction will be transformed into.
+ list<list<string> > ValueCols = [];
+ }
+
+Sample Example
+--------------
+
+Let's say that we want to have a function
+``int getPredOpcode(uint16_t Opcode, enum PredSense inPredSense)`` which
+takes a non-predicated instruction and returns its predicated true or false form
+depending on some input flag, ``inPredSense``. The first step in the process is
+to define a relationship model that relates predicated instructions to their
+non-predicated form by assigning appropriate values to the ``InstrMapping``
+fields. For this relationship, non-predicated instructions are treated as key
+instruction since they are the one used to query the interface function.
+
+.. code-block:: llvm
+
+ def getPredOpcode : InstrMapping {
+ // Choose a FilterClass that is used as a base class for all the
+ // instructions modeling this relationship. This is done to reduce the
+ // search space only to these set of instructions.
+ let FilterClass = "PredRel";
+
+ // Instructions with same values for all the fields in RowFields form a
+ // row in the resulting relation table.
+ // For example, if we want to relate 'ADD' (non-predicated) with 'Add_pt'
+ // (predicated true) and 'Add_pf' (predicated false), then all 3
+ // instructions need to have same value for BaseOpcode field. It can be any
+ // unique value (Ex: XYZ) and should not be shared with any other
+ // instruction not related to 'add'.
+ let RowFields = ["BaseOpcode"];
+
+ // List of attributes that can be used to define key and column instructions
+ // for a relation. Key instruction is passed as an argument
+ // to the function used for querying relation tables. Column instructions
+ // are the instructions they (key) can transform into.
+ //
+ // Here, we choose 'PredSense' as ColFields since this is the unique
+ // attribute of the key (non-predicated) and column (true/false)
+ // instructions involved in this relationship model.
+ let ColFields = ["PredSense"];
+
+ // The key column contains non-predicated instructions.
+ let KeyCol = ["none"];
+
+ // Two value columns - first column contains instructions with
+ // PredSense=true while second column has instructions with PredSense=false.
+ let ValueCols = [["true"], ["false"]];
+ }
+
+TableGen uses the above relationship model to emit relation table that maps
+non-predicated instructions with their predicated forms. It also outputs the
+interface function
+``int getPredOpcode(uint16_t Opcode, enum PredSense inPredSense)`` to query
+the table. Here, Function ``getPredOpcode`` takes two arguments, opcode of the
+current instruction and PredSense of the desired instruction, and returns
+predicated form of the instruction, if found in the relation table.
+In order for an instruction to be added into the relation table, it needs
+to include relevant information in its definition. For example, consider
+following to be the current definitions of ADD, ADD_pt (true) and ADD_pf (false)
+instructions:
+
+.. code-block:: llvm
+
+ def ADD : ALU32_rr<(outs IntRegs:$dst), (ins IntRegs:$a, IntRegs:$b),
+ "$dst = add($a, $b)",
+ [(set (i32 IntRegs:$dst), (add (i32 IntRegs:$a),
+ (i32 IntRegs:$b)))]>;
+
+ def ADD_Pt : ALU32_rr<(outs IntRegs:$dst),
+ (ins PredRegs:$p, IntRegs:$a, IntRegs:$b),
+ "if ($p) $dst = add($a, $b)",
+ []>;
+
+ def ADD_Pf : ALU32_rr<(outs IntRegs:$dst),
+ (ins PredRegs:$p, IntRegs:$a, IntRegs:$b),
+ "if (!$p) $dst = add($a, $b)",
+ []>;
+
+In this step, we modify these instructions to include the information
+required by the relationship model, <tt>getPredOpcode</tt>, so that they can
+be related.
+
+.. code-block:: llvm
+
+ def ADD : PredRel, ALU32_rr<(outs IntRegs:$dst), (ins IntRegs:$a, IntRegs:$b),
+ "$dst = add($a, $b)",
+ [(set (i32 IntRegs:$dst), (add (i32 IntRegs:$a),
+ (i32 IntRegs:$b)))]> {
+ let BaseOpcode = "ADD";
+ let PredSense = "none";
+ }
+
+ def ADD_Pt : PredRel, ALU32_rr<(outs IntRegs:$dst),
+ (ins PredRegs:$p, IntRegs:$a, IntRegs:$b),
+ "if ($p) $dst = add($a, $b)",
+ []> {
+ let BaseOpcode = "ADD";
+ let PredSense = "true";
+ }
+
+ def ADD_Pf : PredRel, ALU32_rr<(outs IntRegs:$dst),
+ (ins PredRegs:$p, IntRegs:$a, IntRegs:$b),
+ "if (!$p) $dst = add($a, $b)",
+ []> {
+ let BaseOpcode = "ADD";
+ let PredSense = "false";
+ }
+
+Please note that all the above instructions use ``PredRel`` as a base class.
+This is extremely important since TableGen uses it as a filter for selecting
+instructions for ``getPredOpcode`` model. Any instruction not derived from
+``PredRel`` is excluded from the analysis. ``BaseOpcode`` is another important
+field. Since it's selected as a ``RowFields`` of the model, it is required
+to have the same value for all 3 instructions in order to be related. Next,
+``PredSense`` is used to determine their column positions by comparing its value
+with ``KeyCol`` and ``ValueCols``. If an instruction sets its ``PredSense``
+value to something not used in the relation model, it will not be assigned
+a column in the relation table.
Added: www-releases/trunk/3.6.2/docs/_sources/InAlloca.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/InAlloca.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/InAlloca.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/InAlloca.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,160 @@
+==========================================
+Design and Usage of the InAlloca Attribute
+==========================================
+
+Introduction
+============
+
+The :ref:`inalloca <attr_inalloca>` attribute is designed to allow
+taking the address of an aggregate argument that is being passed by
+value through memory. Primarily, this feature is required for
+compatibility with the Microsoft C++ ABI. Under that ABI, class
+instances that are passed by value are constructed directly into
+argument stack memory. Prior to the addition of inalloca, calls in LLVM
+were indivisible instructions. There was no way to perform intermediate
+work, such as object construction, between the first stack adjustment
+and the final control transfer. With inalloca, all arguments passed in
+memory are modelled as a single alloca, which can be stored to prior to
+the call. Unfortunately, this complicated feature comes with a large
+set of restrictions designed to bound the lifetime of the argument
+memory around the call.
+
+For now, it is recommended that frontends and optimizers avoid producing
+this construct, primarily because it forces the use of a base pointer.
+This feature may grow in the future to allow general mid-level
+optimization, but for now, it should be regarded as less efficient than
+passing by value with a copy.
+
+Intended Usage
+==============
+
+The example below is the intended LLVM IR lowering for some C++ code
+that passes two default-constructed ``Foo`` objects to ``g`` in the
+32-bit Microsoft C++ ABI.
+
+.. code-block:: c++
+
+ // Foo is non-trivial.
+ struct Foo { int a, b; Foo(); ~Foo(); Foo(const Foo &); };
+ void g(Foo a, Foo b);
+ void f() {
+ g(Foo(), Foo());
+ }
+
+.. code-block:: llvm
+
+ %struct.Foo = type { i32, i32 }
+ declare void @Foo_ctor(%struct.Foo* %this)
+ declare void @Foo_dtor(%struct.Foo* %this)
+ declare void @g(<{ %struct.Foo, %struct.Foo }>* inalloca %memargs)
+
+ define void @f() {
+ entry:
+ %base = call i8* @llvm.stacksave()
+ %memargs = alloca <{ %struct.Foo, %struct.Foo }>
+ %b = getelementptr <{ %struct.Foo, %struct.Foo }>* %memargs, i32 1
+ call void @Foo_ctor(%struct.Foo* %b)
+
+ ; If a's ctor throws, we must destruct b.
+ %a = getelementptr <{ %struct.Foo, %struct.Foo }>* %memargs, i32 0
+ invoke void @Foo_ctor(%struct.Foo* %a)
+ to label %invoke.cont unwind %invoke.unwind
+
+ invoke.cont:
+ call void @g(<{ %struct.Foo, %struct.Foo }>* inalloca %memargs)
+ call void @llvm.stackrestore(i8* %base)
+ ...
+
+ invoke.unwind:
+ call void @Foo_dtor(%struct.Foo* %b)
+ call void @llvm.stackrestore(i8* %base)
+ ...
+ }
+
+To avoid stack leaks, the frontend saves the current stack pointer with
+a call to :ref:`llvm.stacksave <int_stacksave>`. Then, it allocates the
+argument stack space with alloca and calls the default constructor. The
+default constructor could throw an exception, so the frontend has to
+create a landing pad. The frontend has to destroy the already
+constructed argument ``b`` before restoring the stack pointer. If the
+constructor does not unwind, ``g`` is called. In the Microsoft C++ ABI,
+``g`` will destroy its arguments, and then the stack is restored in
+``f``.
+
+Design Considerations
+=====================
+
+Lifetime
+--------
+
+The biggest design consideration for this feature is object lifetime.
+We cannot model the arguments as static allocas in the entry block,
+because all calls need to use the memory at the top of the stack to pass
+arguments. We cannot vend pointers to that memory at function entry
+because after code generation they will alias.
+
+The rule against allocas between argument allocations and the call site
+avoids this problem, but it creates a cleanup problem. Cleanup and
+lifetime is handled explicitly with stack save and restore calls. In
+the future, we may want to introduce a new construct such as ``freea``
+or ``afree`` to make it clear that this stack adjusting cleanup is less
+powerful than a full stack save and restore.
+
+Nested Calls and Copy Elision
+-----------------------------
+
+We also want to be able to support copy elision into these argument
+slots. This means we have to support multiple live argument
+allocations.
+
+Consider the evaluation of:
+
+.. code-block:: c++
+
+ // Foo is non-trivial.
+ struct Foo { int a; Foo(); Foo(const &Foo); ~Foo(); };
+ Foo bar(Foo b);
+ int main() {
+ bar(bar(Foo()));
+ }
+
+In this case, we want to be able to elide copies into ``bar``'s argument
+slots. That means we need to have more than one set of argument frames
+active at the same time. First, we need to allocate the frame for the
+outer call so we can pass it in as the hidden struct return pointer to
+the middle call. Then we do the same for the middle call, allocating a
+frame and passing its address to ``Foo``'s default constructor. By
+wrapping the evaluation of the inner ``bar`` with stack save and
+restore, we can have multiple overlapping active call frames.
+
+Callee-cleanup Calling Conventions
+----------------------------------
+
+Another wrinkle is the existence of callee-cleanup conventions. On
+Windows, all methods and many other functions adjust the stack to clear
+the memory used to pass their arguments. In some sense, this means that
+the allocas are automatically cleared by the call. However, LLVM
+instead models this as a write of undef to all of the inalloca values
+passed to the call instead of a stack adjustment. Frontends should
+still restore the stack pointer to avoid a stack leak.
+
+Exceptions
+----------
+
+There is also the possibility of an exception. If argument evaluation
+or copy construction throws an exception, the landing pad must do
+cleanup, which includes adjusting the stack pointer to avoid a stack
+leak. This means the cleanup of the stack memory cannot be tied to the
+call itself. There needs to be a separate IR-level instruction that can
+perform independent cleanup of arguments.
+
+Efficiency
+----------
+
+Eventually, it should be possible to generate efficient code for this
+construct. In particular, using inalloca should not require a base
+pointer. If the backend can prove that all points in the CFG only have
+one possible stack level, then it can address the stack directly from
+the stack pointer. While this is not yet implemented, the plan is that
+the inalloca attribute should not change much, but the frontend IR
+generation recommendations may change.
Added: www-releases/trunk/3.6.2/docs/_sources/LLVMBuild.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/LLVMBuild.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/LLVMBuild.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/LLVMBuild.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,325 @@
+===============
+LLVMBuild Guide
+===============
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+This document describes the ``LLVMBuild`` organization and files which
+we use to describe parts of the LLVM ecosystem. For description of
+specific LLVMBuild related tools, please see the command guide.
+
+LLVM is designed to be a modular set of libraries which can be flexibly
+mixed together in order to build a variety of tools, like compilers,
+JITs, custom code generators, optimization passes, interpreters, and so
+on. Related projects in the LLVM system like Clang and LLDB also tend to
+follow this philosophy.
+
+In order to support this usage style, LLVM has a fairly strict structure
+as to how the source code and various components are organized. The
+``LLVMBuild.txt`` files are the explicit specification of that
+structure, and are used by the build systems and other tools in order to
+develop the LLVM project.
+
+Project Organization
+====================
+
+The source code for LLVM projects using the LLVMBuild system (LLVM,
+Clang, and LLDB) is organized into *components*, which define the
+separate pieces of functionality that make up the project. These
+projects may consist of many libraries, associated tools, build tools,
+or other utility tools (for example, testing tools).
+
+For the most part, the project contents are organized around defining
+one main component per each subdirectory. Each such directory contains
+an ``LLVMBuild.txt`` which contains the component definitions.
+
+The component descriptions for the project as a whole are automatically
+gathered by the LLVMBuild tools. The tools automatically traverse the
+source directory structure to find all of the component description
+files. NOTE: For performance/sanity reasons, we only traverse into
+subdirectories when the parent itself contains an ``LLVMBuild.txt``
+description file.
+
+Build Integration
+=================
+
+The LLVMBuild files themselves are just a declarative way to describe
+the project structure. The actual building of the LLVM project is
+handled by another build system (currently we support both
+:doc:`Makefiles <MakefileGuide>` and :doc:`CMake <CMake>`).
+
+The build system implementation will load the relevant contents of the
+LLVMBuild files and use that to drive the actual project build.
+Typically, the build system will only need to load this information at
+"configure" time, and use it to generative native information. Build
+systems will also handle automatically reconfiguring their information
+when the contents of the ``LLVMBuild.txt`` files change.
+
+Developers generally are not expected to need to be aware of the details
+of how the LLVMBuild system is integrated into their build. Ideally,
+LLVM developers who are not working on the build system would only ever
+need to modify the contents of the ``LLVMBuild.txt`` description files
+(although we have not reached this goal yet).
+
+For more information on the utility tool we provide to help interfacing
+with the build system, please see the :doc:`llvm-build
+<CommandGuide/llvm-build>` documentation.
+
+Component Overview
+==================
+
+As mentioned earlier, LLVM projects are organized into logical
+*components*. Every component is typically grouped into its own
+subdirectory. Generally, a component is organized around a coherent
+group of sources which have some kind of clear API separation from other
+parts of the code.
+
+LLVM primarily uses the following types of components:
+
+- *Libraries* - Library components define a distinct API which can be
+ independently linked into LLVM client applications. Libraries typically
+ have private and public header files, and may specify a link of required
+ libraries that they build on top of.
+- *Build Tools* - Build tools are applications which are designed to be run
+ as part of the build process (typically to generate other source files).
+ Currently, LLVM uses one main build tool called :doc:`TableGen/index`
+ to generate a variety of source files.
+- *Tools* - Command line applications which are built using the LLVM
+ component libraries. Most LLVM tools are small and are primarily
+ frontends to the library interfaces.
+
+Components are described using ``LLVMBuild.txt`` files in the directories
+that define the component. See the `LLVMBuild Format Reference`_ section
+for information on the exact format of these files.
+
+LLVMBuild Format Reference
+==========================
+
+LLVMBuild files are written in a simple variant of the INI or configuration
+file format (`Wikipedia entry`_). The format defines a list of sections
+each of which may contain some number of properties. A simple example of
+the file format is below:
+
+.. _Wikipedia entry: http://en.wikipedia.org/wiki/INI_file
+
+.. code-block:: ini
+
+ ; Comments start with a semi-colon.
+
+ ; Sections are declared using square brackets.
+ [component_0]
+
+ ; Properties are declared using '=' and are contained in the previous section.
+ ;
+ ; We support simple string and boolean scalar values and list values, where
+ ; items are separated by spaces. There is no support for quoting, and so
+ ; property values may not contain spaces.
+ property_name = property_value
+ list_property_name = value_1 value_2 ... value_n
+ boolean_property_name = 1 (or 0)
+
+LLVMBuild files are expected to define a strict set of sections and
+properties. A typical component description file for a library
+component would look like the following example:
+
+.. code-block:: ini
+
+ [component_0]
+ type = Library
+ name = Linker
+ parent = Libraries
+ required_libraries = Archive BitReader Core Support TransformUtils
+
+A full description of the exact sections and properties which are
+allowed follows.
+
+Each file may define exactly one common component, named ``common``. The
+common component may define the following properties:
+
+- ``subdirectories`` **[optional]**
+
+ If given, a list of the names of the subdirectories from the current
+ subpath to search for additional LLVMBuild files.
+
+Each file may define multiple components. Each component is described by a
+section who name starts with ``component``. The remainder of the section
+name is ignored, but each section name must be unique. Typically components
+are just number in order for files with multiple components
+(``component_0``, ``component_1``, and so on).
+
+.. warning::
+
+ Section names not matching this format (or the ``common`` section) are
+ currently unused and are disallowed.
+
+Every component is defined by the properties in the section. The exact
+list of properties that are allowed depends on the component type.
+Components **may not** define any properties other than those expected
+by the component type.
+
+Every component must define the following properties:
+
+- ``type`` **[required]**
+
+ The type of the component. Supported component types are detailed
+ below. Most components will define additional properties which may be
+ required or optional.
+
+- ``name`` **[required]**
+
+ The name of the component. Names are required to be unique across the
+ entire project.
+
+- ``parent`` **[required]**
+
+ The name of the logical parent of the component. Components are
+ organized into a logical tree to make it easier to navigate and
+ organize groups of components. The parents have no semantics as far
+ as the project build is concerned, however. Typically, the parent
+ will be the main component of the parent directory.
+
+ Components may reference the root pseudo component using ``$ROOT`` to
+ indicate they should logically be grouped at the top-level.
+
+Components may define the following properties:
+
+- ``dependencies`` **[optional]**
+
+ If specified, a list of names of components which *must* be built
+ prior to this one. This should only be exactly those components which
+ produce some tool or source code required for building the component.
+
+ .. note::
+
+ ``Group`` and ``LibraryGroup`` components have no semantics for the
+ actual build, and are not allowed to specify dependencies.
+
+The following section lists the available component types, as well as
+the properties which are associated with that component.
+
+- ``type = Group``
+
+ Group components exist purely to allow additional arbitrary structuring
+ of the logical components tree. For example, one might define a
+ ``Libraries`` group to hold all of the root library components.
+
+ ``Group`` components have no additionally properties.
+
+- ``type = Library``
+
+ Library components define an individual library which should be built
+ from the source code in the component directory.
+
+ Components with this type use the following properties:
+
+ - ``library_name`` **[optional]**
+
+ If given, the name to use for the actual library file on disk. If
+ not given, the name is derived from the component name itself.
+
+ - ``required_libraries`` **[optional]**
+
+ If given, a list of the names of ``Library`` or ``LibraryGroup``
+ components which must also be linked in whenever this library is
+ used. That is, the link time dependencies for this component. When
+ tools are built, the build system will include the transitive closure
+ of all ``required_libraries`` for the components the tool needs.
+
+ - ``add_to_library_groups`` **[optional]**
+
+ If given, a list of the names of ``LibraryGroup`` components which
+ this component is also part of. This allows nesting groups of
+ components. For example, the ``X86`` target might define a library
+ group for all of the ``X86`` components. That library group might
+ then be included in the ``all-targets`` library group.
+
+ - ``installed`` **[optional]** **[boolean]**
+
+ Whether this library is installed. Libraries that are not installed
+ are only reported by ``llvm-config`` when it is run as part of a
+ development directory.
+
+- ``type = LibraryGroup``
+
+ ``LibraryGroup`` components are a mechanism to allow easy definition of
+ useful sets of related components. In particular, we use them to easily
+ specify things like "all targets", or "all assembly printers".
+
+ Components with this type use the following properties:
+
+ - ``required_libraries`` **[optional]**
+
+ See the ``Library`` type for a description of this property.
+
+ - ``add_to_library_groups`` **[optional]**
+
+ See the ``Library`` type for a description of this property.
+
+- ``type = TargetGroup``
+
+ ``TargetGroup`` components are an extension of ``LibraryGroup``\s,
+ specifically for defining LLVM targets (which are handled specially in a
+ few places).
+
+ The name of the component should always be the name of the target.
+
+ Components with this type use the ``LibraryGroup`` properties in
+ addition to:
+
+ - ``has_asmparser`` **[optional]** **[boolean]**
+
+ Whether this target defines an assembly parser.
+
+ - ``has_asmprinter`` **[optional]** **[boolean]**
+
+ Whether this target defines an assembly printer.
+
+ - ``has_disassembler`` **[optional]** **[boolean]**
+
+ Whether this target defines a disassembler.
+
+ - ``has_jit`` **[optional]** **[boolean]**
+
+ Whether this target supports JIT compilation.
+
+- ``type = Tool``
+
+ ``Tool`` components define standalone command line tools which should be
+ built from the source code in the component directory and linked.
+
+ Components with this type use the following properties:
+
+ - ``required_libraries`` **[optional]**
+
+ If given, a list of the names of ``Library`` or ``LibraryGroup``
+ components which this tool is required to be linked with.
+
+ .. note::
+
+ The values should be the component names, which may not always
+ match up with the actual library names on disk.
+
+ Build systems are expected to properly include all of the libraries
+ required by the linked components (i.e., the transitive closure of
+ ``required_libraries``).
+
+ Build systems are also expected to understand that those library
+ components must be built prior to linking -- they do not also need
+ to be listed under ``dependencies``.
+
+- ``type = BuildTool``
+
+ ``BuildTool`` components are like ``Tool`` components, except that the
+ tool is supposed to be built for the platform where the build is running
+ (instead of that platform being targeted). Build systems are expected
+ to handle the fact that required libraries may need to be built for
+ multiple platforms in order to be able to link this tool.
+
+ ``BuildTool`` components currently use the exact same properties as
+ ``Tool`` components, the type distinction is only used to differentiate
+ what the tool is built for.
+
Added: www-releases/trunk/3.6.2/docs/_sources/LangRef.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/LangRef.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/LangRef.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/LangRef.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,9924 @@
+==============================
+LLVM Language Reference Manual
+==============================
+
+.. contents::
+ :local:
+ :depth: 4
+
+Abstract
+========
+
+This document is a reference manual for the LLVM assembly language. LLVM
+is a Static Single Assignment (SSA) based representation that provides
+type safety, low-level operations, flexibility, and the capability of
+representing 'all' high-level languages cleanly. It is the common code
+representation used throughout all phases of the LLVM compilation
+strategy.
+
+Introduction
+============
+
+The LLVM code representation is designed to be used in three different
+forms: as an in-memory compiler IR, as an on-disk bitcode representation
+(suitable for fast loading by a Just-In-Time compiler), and as a human
+readable assembly language representation. This allows LLVM to provide a
+powerful intermediate representation for efficient compiler
+transformations and analysis, while providing a natural means to debug
+and visualize the transformations. The three different forms of LLVM are
+all equivalent. This document describes the human readable
+representation and notation.
+
+The LLVM representation aims to be light-weight and low-level while
+being expressive, typed, and extensible at the same time. It aims to be
+a "universal IR" of sorts, by being at a low enough level that
+high-level ideas may be cleanly mapped to it (similar to how
+microprocessors are "universal IR's", allowing many source languages to
+be mapped to them). By providing type information, LLVM can be used as
+the target of optimizations: for example, through pointer analysis, it
+can be proven that a C automatic variable is never accessed outside of
+the current function, allowing it to be promoted to a simple SSA value
+instead of a memory location.
+
+.. _wellformed:
+
+Well-Formedness
+---------------
+
+It is important to note that this document describes 'well formed' LLVM
+assembly language. There is a difference between what the parser accepts
+and what is considered 'well formed'. For example, the following
+instruction is syntactically okay, but not well formed:
+
+.. code-block:: llvm
+
+ %x = add i32 1, %x
+
+because the definition of ``%x`` does not dominate all of its uses. The
+LLVM infrastructure provides a verification pass that may be used to
+verify that an LLVM module is well formed. This pass is automatically
+run by the parser after parsing input assembly and by the optimizer
+before it outputs bitcode. The violations pointed out by the verifier
+pass indicate bugs in transformation passes or input to the parser.
+
+.. _identifiers:
+
+Identifiers
+===========
+
+LLVM identifiers come in two basic types: global and local. Global
+identifiers (functions, global variables) begin with the ``'@'``
+character. Local identifiers (register names, types) begin with the
+``'%'`` character. Additionally, there are three different formats for
+identifiers, for different purposes:
+
+#. Named values are represented as a string of characters with their
+ prefix. For example, ``%foo``, ``@DivisionByZero``,
+ ``%a.really.long.identifier``. The actual regular expression used is
+ '``[%@][-a-zA-Z$._][-a-zA-Z$._0-9]*``'. Identifiers that require other
+ characters in their names can be surrounded with quotes. Special
+ characters may be escaped using ``"\xx"`` where ``xx`` is the ASCII
+ code for the character in hexadecimal. In this way, any character can
+ be used in a name value, even quotes themselves. The ``"\01"`` prefix
+ can be used on global variables to suppress mangling.
+#. Unnamed values are represented as an unsigned numeric value with
+ their prefix. For example, ``%12``, ``@2``, ``%44``.
+#. Constants, which are described in the section Constants_ below.
+
+LLVM requires that values start with a prefix for two reasons: Compilers
+don't need to worry about name clashes with reserved words, and the set
+of reserved words may be expanded in the future without penalty.
+Additionally, unnamed identifiers allow a compiler to quickly come up
+with a temporary variable without having to avoid symbol table
+conflicts.
+
+Reserved words in LLVM are very similar to reserved words in other
+languages. There are keywords for different opcodes ('``add``',
+'``bitcast``', '``ret``', etc...), for primitive type names ('``void``',
+'``i32``', etc...), and others. These reserved words cannot conflict
+with variable names, because none of them start with a prefix character
+(``'%'`` or ``'@'``).
+
+Here is an example of LLVM code to multiply the integer variable
+'``%X``' by 8:
+
+The easy way:
+
+.. code-block:: llvm
+
+ %result = mul i32 %X, 8
+
+After strength reduction:
+
+.. code-block:: llvm
+
+ %result = shl i32 %X, 3
+
+And the hard way:
+
+.. code-block:: llvm
+
+ %0 = add i32 %X, %X ; yields i32:%0
+ %1 = add i32 %0, %0 ; yields i32:%1
+ %result = add i32 %1, %1
+
+This last way of multiplying ``%X`` by 8 illustrates several important
+lexical features of LLVM:
+
+#. Comments are delimited with a '``;``' and go until the end of line.
+#. Unnamed temporaries are created when the result of a computation is
+ not assigned to a named value.
+#. Unnamed temporaries are numbered sequentially (using a per-function
+ incrementing counter, starting with 0). Note that basic blocks and unnamed
+ function parameters are included in this numbering. For example, if the
+ entry basic block is not given a label name and all function parameters are
+ named, then it will get number 0.
+
+It also shows a convention that we follow in this document. When
+demonstrating instructions, we will follow an instruction with a comment
+that defines the type and name of value produced.
+
+High Level Structure
+====================
+
+Module Structure
+----------------
+
+LLVM programs are composed of ``Module``'s, each of which is a
+translation unit of the input programs. Each module consists of
+functions, global variables, and symbol table entries. Modules may be
+combined together with the LLVM linker, which merges function (and
+global variable) definitions, resolves forward declarations, and merges
+symbol table entries. Here is an example of the "hello world" module:
+
+.. code-block:: llvm
+
+ ; Declare the string constant as a global constant.
+ @.str = private unnamed_addr constant [13 x i8] c"hello world\0A\00"
+
+ ; External declaration of the puts function
+ declare i32 @puts(i8* nocapture) nounwind
+
+ ; Definition of main function
+ define i32 @main() { ; i32()*
+ ; Convert [13 x i8]* to i8 *...
+ %cast210 = getelementptr [13 x i8]* @.str, i64 0, i64 0
+
+ ; Call puts function to write out the string to stdout.
+ call i32 @puts(i8* %cast210)
+ ret i32 0
+ }
+
+ ; Named metadata
+ !0 = !{i32 42, null, !"string"}
+ !foo = !{!0}
+
+This example is made up of a :ref:`global variable <globalvars>` named
+"``.str``", an external declaration of the "``puts``" function, a
+:ref:`function definition <functionstructure>` for "``main``" and
+:ref:`named metadata <namedmetadatastructure>` "``foo``".
+
+In general, a module is made up of a list of global values (where both
+functions and global variables are global values). Global values are
+represented by a pointer to a memory location (in this case, a pointer
+to an array of char, and a pointer to a function), and have one of the
+following :ref:`linkage types <linkage>`.
+
+.. _linkage:
+
+Linkage Types
+-------------
+
+All Global Variables and Functions have one of the following types of
+linkage:
+
+``private``
+ Global values with "``private``" linkage are only directly
+ accessible by objects in the current module. In particular, linking
+ code into a module with an private global value may cause the
+ private to be renamed as necessary to avoid collisions. Because the
+ symbol is private to the module, all references can be updated. This
+ doesn't show up in any symbol table in the object file.
+``internal``
+ Similar to private, but the value shows as a local symbol
+ (``STB_LOCAL`` in the case of ELF) in the object file. This
+ corresponds to the notion of the '``static``' keyword in C.
+``available_externally``
+ Globals with "``available_externally``" linkage are never emitted
+ into the object file corresponding to the LLVM module. They exist to
+ allow inlining and other optimizations to take place given knowledge
+ of the definition of the global, which is known to be somewhere
+ outside the module. Globals with ``available_externally`` linkage
+ are allowed to be discarded at will, and are otherwise the same as
+ ``linkonce_odr``. This linkage type is only allowed on definitions,
+ not declarations.
+``linkonce``
+ Globals with "``linkonce``" linkage are merged with other globals of
+ the same name when linkage occurs. This can be used to implement
+ some forms of inline functions, templates, or other code which must
+ be generated in each translation unit that uses it, but where the
+ body may be overridden with a more definitive definition later.
+ Unreferenced ``linkonce`` globals are allowed to be discarded. Note
+ that ``linkonce`` linkage does not actually allow the optimizer to
+ inline the body of this function into callers because it doesn't
+ know if this definition of the function is the definitive definition
+ within the program or whether it will be overridden by a stronger
+ definition. To enable inlining and other optimizations, use
+ "``linkonce_odr``" linkage.
+``weak``
+ "``weak``" linkage has the same merging semantics as ``linkonce``
+ linkage, except that unreferenced globals with ``weak`` linkage may
+ not be discarded. This is used for globals that are declared "weak"
+ in C source code.
+``common``
+ "``common``" linkage is most similar to "``weak``" linkage, but they
+ are used for tentative definitions in C, such as "``int X;``" at
+ global scope. Symbols with "``common``" linkage are merged in the
+ same way as ``weak symbols``, and they may not be deleted if
+ unreferenced. ``common`` symbols may not have an explicit section,
+ must have a zero initializer, and may not be marked
+ ':ref:`constant <globalvars>`'. Functions and aliases may not have
+ common linkage.
+
+.. _linkage_appending:
+
+``appending``
+ "``appending``" linkage may only be applied to global variables of
+ pointer to array type. When two global variables with appending
+ linkage are linked together, the two global arrays are appended
+ together. This is the LLVM, typesafe, equivalent of having the
+ system linker append together "sections" with identical names when
+ .o files are linked.
+``extern_weak``
+ The semantics of this linkage follow the ELF object file model: the
+ symbol is weak until linked, if not linked, the symbol becomes null
+ instead of being an undefined reference.
+``linkonce_odr``, ``weak_odr``
+ Some languages allow differing globals to be merged, such as two
+ functions with different semantics. Other languages, such as
+ ``C++``, ensure that only equivalent globals are ever merged (the
+ "one definition rule" --- "ODR"). Such languages can use the
+ ``linkonce_odr`` and ``weak_odr`` linkage types to indicate that the
+ global will only be merged with equivalent globals. These linkage
+ types are otherwise the same as their non-``odr`` versions.
+``external``
+ If none of the above identifiers are used, the global is externally
+ visible, meaning that it participates in linkage and can be used to
+ resolve external symbol references.
+
+It is illegal for a function *declaration* to have any linkage type
+other than ``external`` or ``extern_weak``.
+
+.. _callingconv:
+
+Calling Conventions
+-------------------
+
+LLVM :ref:`functions <functionstructure>`, :ref:`calls <i_call>` and
+:ref:`invokes <i_invoke>` can all have an optional calling convention
+specified for the call. The calling convention of any pair of dynamic
+caller/callee must match, or the behavior of the program is undefined.
+The following calling conventions are supported by LLVM, and more may be
+added in the future:
+
+"``ccc``" - The C calling convention
+ This calling convention (the default if no other calling convention
+ is specified) matches the target C calling conventions. This calling
+ convention supports varargs function calls and tolerates some
+ mismatch in the declared prototype and implemented declaration of
+ the function (as does normal C).
+"``fastcc``" - The fast calling convention
+ This calling convention attempts to make calls as fast as possible
+ (e.g. by passing things in registers). This calling convention
+ allows the target to use whatever tricks it wants to produce fast
+ code for the target, without having to conform to an externally
+ specified ABI (Application Binary Interface). `Tail calls can only
+ be optimized when this, the GHC or the HiPE convention is
+ used. <CodeGenerator.html#id80>`_ This calling convention does not
+ support varargs and requires the prototype of all callees to exactly
+ match the prototype of the function definition.
+"``coldcc``" - The cold calling convention
+ This calling convention attempts to make code in the caller as
+ efficient as possible under the assumption that the call is not
+ commonly executed. As such, these calls often preserve all registers
+ so that the call does not break any live ranges in the caller side.
+ This calling convention does not support varargs and requires the
+ prototype of all callees to exactly match the prototype of the
+ function definition. Furthermore the inliner doesn't consider such function
+ calls for inlining.
+"``cc 10``" - GHC convention
+ This calling convention has been implemented specifically for use by
+ the `Glasgow Haskell Compiler (GHC) <http://www.haskell.org/ghc>`_.
+ It passes everything in registers, going to extremes to achieve this
+ by disabling callee save registers. This calling convention should
+ not be used lightly but only for specific situations such as an
+ alternative to the *register pinning* performance technique often
+ used when implementing functional programming languages. At the
+ moment only X86 supports this convention and it has the following
+ limitations:
+
+ - On *X86-32* only supports up to 4 bit type parameters. No
+ floating point types are supported.
+ - On *X86-64* only supports up to 10 bit type parameters and 6
+ floating point parameters.
+
+ This calling convention supports `tail call
+ optimization <CodeGenerator.html#id80>`_ but requires both the
+ caller and callee are using it.
+"``cc 11``" - The HiPE calling convention
+ This calling convention has been implemented specifically for use by
+ the `High-Performance Erlang
+ (HiPE) <http://www.it.uu.se/research/group/hipe/>`_ compiler, *the*
+ native code compiler of the `Ericsson's Open Source Erlang/OTP
+ system <http://www.erlang.org/download.shtml>`_. It uses more
+ registers for argument passing than the ordinary C calling
+ convention and defines no callee-saved registers. The calling
+ convention properly supports `tail call
+ optimization <CodeGenerator.html#id80>`_ but requires that both the
+ caller and the callee use it. It uses a *register pinning*
+ mechanism, similar to GHC's convention, for keeping frequently
+ accessed runtime components pinned to specific hardware registers.
+ At the moment only X86 supports this convention (both 32 and 64
+ bit).
+"``webkit_jscc``" - WebKit's JavaScript calling convention
+ This calling convention has been implemented for `WebKit FTL JIT
+ <https://trac.webkit.org/wiki/FTLJIT>`_. It passes arguments on the
+ stack right to left (as cdecl does), and returns a value in the
+ platform's customary return register.
+"``anyregcc``" - Dynamic calling convention for code patching
+ This is a special convention that supports patching an arbitrary code
+ sequence in place of a call site. This convention forces the call
+ arguments into registers but allows them to be dynamcially
+ allocated. This can currently only be used with calls to
+ llvm.experimental.patchpoint because only this intrinsic records
+ the location of its arguments in a side table. See :doc:`StackMaps`.
+"``preserve_mostcc``" - The `PreserveMost` calling convention
+ This calling convention attempts to make the code in the caller as little
+ intrusive as possible. This calling convention behaves identical to the `C`
+ calling convention on how arguments and return values are passed, but it
+ uses a different set of caller/callee-saved registers. This alleviates the
+ burden of saving and recovering a large register set before and after the
+ call in the caller. If the arguments are passed in callee-saved registers,
+ then they will be preserved by the callee across the call. This doesn't
+ apply for values returned in callee-saved registers.
+
+ - On X86-64 the callee preserves all general purpose registers, except for
+ R11. R11 can be used as a scratch register. Floating-point registers
+ (XMMs/YMMs) are not preserved and need to be saved by the caller.
+
+ The idea behind this convention is to support calls to runtime functions
+ that have a hot path and a cold path. The hot path is usually a small piece
+ of code that doesn't many registers. The cold path might need to call out to
+ another function and therefore only needs to preserve the caller-saved
+ registers, which haven't already been saved by the caller. The
+ `PreserveMost` calling convention is very similar to the `cold` calling
+ convention in terms of caller/callee-saved registers, but they are used for
+ different types of function calls. `coldcc` is for function calls that are
+ rarely executed, whereas `preserve_mostcc` function calls are intended to be
+ on the hot path and definitely executed a lot. Furthermore `preserve_mostcc`
+ doesn't prevent the inliner from inlining the function call.
+
+ This calling convention will be used by a future version of the ObjectiveC
+ runtime and should therefore still be considered experimental at this time.
+ Although this convention was created to optimize certain runtime calls to
+ the ObjectiveC runtime, it is not limited to this runtime and might be used
+ by other runtimes in the future too. The current implementation only
+ supports X86-64, but the intention is to support more architectures in the
+ future.
+"``preserve_allcc``" - The `PreserveAll` calling convention
+ This calling convention attempts to make the code in the caller even less
+ intrusive than the `PreserveMost` calling convention. This calling
+ convention also behaves identical to the `C` calling convention on how
+ arguments and return values are passed, but it uses a different set of
+ caller/callee-saved registers. This removes the burden of saving and
+ recovering a large register set before and after the call in the caller. If
+ the arguments are passed in callee-saved registers, then they will be
+ preserved by the callee across the call. This doesn't apply for values
+ returned in callee-saved registers.
+
+ - On X86-64 the callee preserves all general purpose registers, except for
+ R11. R11 can be used as a scratch register. Furthermore it also preserves
+ all floating-point registers (XMMs/YMMs).
+
+ The idea behind this convention is to support calls to runtime functions
+ that don't need to call out to any other functions.
+
+ This calling convention, like the `PreserveMost` calling convention, will be
+ used by a future version of the ObjectiveC runtime and should be considered
+ experimental at this time.
+"``cc <n>``" - Numbered convention
+ Any calling convention may be specified by number, allowing
+ target-specific calling conventions to be used. Target specific
+ calling conventions start at 64.
+
+More calling conventions can be added/defined on an as-needed basis, to
+support Pascal conventions or any other well-known target-independent
+convention.
+
+.. _visibilitystyles:
+
+Visibility Styles
+-----------------
+
+All Global Variables and Functions have one of the following visibility
+styles:
+
+"``default``" - Default style
+ On targets that use the ELF object file format, default visibility
+ means that the declaration is visible to other modules and, in
+ shared libraries, means that the declared entity may be overridden.
+ On Darwin, default visibility means that the declaration is visible
+ to other modules. Default visibility corresponds to "external
+ linkage" in the language.
+"``hidden``" - Hidden style
+ Two declarations of an object with hidden visibility refer to the
+ same object if they are in the same shared object. Usually, hidden
+ visibility indicates that the symbol will not be placed into the
+ dynamic symbol table, so no other module (executable or shared
+ library) can reference it directly.
+"``protected``" - Protected style
+ On ELF, protected visibility indicates that the symbol will be
+ placed in the dynamic symbol table, but that references within the
+ defining module will bind to the local symbol. That is, the symbol
+ cannot be overridden by another module.
+
+A symbol with ``internal`` or ``private`` linkage must have ``default``
+visibility.
+
+.. _dllstorageclass:
+
+DLL Storage Classes
+-------------------
+
+All Global Variables, Functions and Aliases can have one of the following
+DLL storage class:
+
+``dllimport``
+ "``dllimport``" causes the compiler to reference a function or variable via
+ a global pointer to a pointer that is set up by the DLL exporting the
+ symbol. On Microsoft Windows targets, the pointer name is formed by
+ combining ``__imp_`` and the function or variable name.
+``dllexport``
+ "``dllexport``" causes the compiler to provide a global pointer to a pointer
+ in a DLL, so that it can be referenced with the ``dllimport`` attribute. On
+ Microsoft Windows targets, the pointer name is formed by combining
+ ``__imp_`` and the function or variable name. Since this storage class
+ exists for defining a dll interface, the compiler, assembler and linker know
+ it is externally referenced and must refrain from deleting the symbol.
+
+.. _tls_model:
+
+Thread Local Storage Models
+---------------------------
+
+A variable may be defined as ``thread_local``, which means that it will
+not be shared by threads (each thread will have a separated copy of the
+variable). Not all targets support thread-local variables. Optionally, a
+TLS model may be specified:
+
+``localdynamic``
+ For variables that are only used within the current shared library.
+``initialexec``
+ For variables in modules that will not be loaded dynamically.
+``localexec``
+ For variables defined in the executable and only used within it.
+
+If no explicit model is given, the "general dynamic" model is used.
+
+The models correspond to the ELF TLS models; see `ELF Handling For
+Thread-Local Storage <http://people.redhat.com/drepper/tls.pdf>`_ for
+more information on under which circumstances the different models may
+be used. The target may choose a different TLS model if the specified
+model is not supported, or if a better choice of model can be made.
+
+A model can also be specified in a alias, but then it only governs how
+the alias is accessed. It will not have any effect in the aliasee.
+
+.. _namedtypes:
+
+Structure Types
+---------------
+
+LLVM IR allows you to specify both "identified" and "literal" :ref:`structure
+types <t_struct>`. Literal types are uniqued structurally, but identified types
+are never uniqued. An :ref:`opaque structural type <t_opaque>` can also be used
+to forward declare a type that is not yet available.
+
+An example of a identified structure specification is:
+
+.. code-block:: llvm
+
+ %mytype = type { %mytype*, i32 }
+
+Prior to the LLVM 3.0 release, identified types were structurally uniqued. Only
+literal types are uniqued in recent versions of LLVM.
+
+.. _globalvars:
+
+Global Variables
+----------------
+
+Global variables define regions of memory allocated at compilation time
+instead of run-time.
+
+Global variables definitions must be initialized.
+
+Global variables in other translation units can also be declared, in which
+case they don't have an initializer.
+
+Either global variable definitions or declarations may have an explicit section
+to be placed in and may have an optional explicit alignment specified.
+
+A variable may be defined as a global ``constant``, which indicates that
+the contents of the variable will **never** be modified (enabling better
+optimization, allowing the global data to be placed in the read-only
+section of an executable, etc). Note that variables that need runtime
+initialization cannot be marked ``constant`` as there is a store to the
+variable.
+
+LLVM explicitly allows *declarations* of global variables to be marked
+constant, even if the final definition of the global is not. This
+capability can be used to enable slightly better optimization of the
+program, but requires the language definition to guarantee that
+optimizations based on the 'constantness' are valid for the translation
+units that do not include the definition.
+
+As SSA values, global variables define pointer values that are in scope
+(i.e. they dominate) all basic blocks in the program. Global variables
+always define a pointer to their "content" type because they describe a
+region of memory, and all memory objects in LLVM are accessed through
+pointers.
+
+Global variables can be marked with ``unnamed_addr`` which indicates
+that the address is not significant, only the content. Constants marked
+like this can be merged with other constants if they have the same
+initializer. Note that a constant with significant address *can* be
+merged with a ``unnamed_addr`` constant, the result being a constant
+whose address is significant.
+
+A global variable may be declared to reside in a target-specific
+numbered address space. For targets that support them, address spaces
+may affect how optimizations are performed and/or what target
+instructions are used to access the variable. The default address space
+is zero. The address space qualifier must precede any other attributes.
+
+LLVM allows an explicit section to be specified for globals. If the
+target supports it, it will emit globals to the section specified.
+Additionally, the global can placed in a comdat if the target has the necessary
+support.
+
+By default, global initializers are optimized by assuming that global
+variables defined within the module are not modified from their
+initial values before the start of the global initializer. This is
+true even for variables potentially accessible from outside the
+module, including those with external linkage or appearing in
+``@llvm.used`` or dllexported variables. This assumption may be suppressed
+by marking the variable with ``externally_initialized``.
+
+An explicit alignment may be specified for a global, which must be a
+power of 2. If not present, or if the alignment is set to zero, the
+alignment of the global is set by the target to whatever it feels
+convenient. If an explicit alignment is specified, the global is forced
+to have exactly that alignment. Targets and optimizers are not allowed
+to over-align the global if the global has an assigned section. In this
+case, the extra alignment could be observable: for example, code could
+assume that the globals are densely packed in their section and try to
+iterate over them as an array, alignment padding would break this
+iteration. The maximum alignment is ``1 << 29``.
+
+Globals can also have a :ref:`DLL storage class <dllstorageclass>`.
+
+Variables and aliasaes can have a
+:ref:`Thread Local Storage Model <tls_model>`.
+
+Syntax::
+
+ [@<GlobalVarName> =] [Linkage] [Visibility] [DLLStorageClass] [ThreadLocal]
+ [unnamed_addr] [AddrSpace] [ExternallyInitialized]
+ <global | constant> <Type> [<InitializerConstant>]
+ [, section "name"] [, comdat [($name)]]
+ [, align <Alignment>]
+
+For example, the following defines a global in a numbered address space
+with an initializer, section, and alignment:
+
+.. code-block:: llvm
+
+ @G = addrspace(5) constant float 1.0, section "foo", align 4
+
+The following example just declares a global variable
+
+.. code-block:: llvm
+
+ @G = external global i32
+
+The following example defines a thread-local global with the
+``initialexec`` TLS model:
+
+.. code-block:: llvm
+
+ @G = thread_local(initialexec) global i32 0, align 4
+
+.. _functionstructure:
+
+Functions
+---------
+
+LLVM function definitions consist of the "``define``" keyword, an
+optional :ref:`linkage type <linkage>`, an optional :ref:`visibility
+style <visibility>`, an optional :ref:`DLL storage class <dllstorageclass>`,
+an optional :ref:`calling convention <callingconv>`,
+an optional ``unnamed_addr`` attribute, a return type, an optional
+:ref:`parameter attribute <paramattrs>` for the return type, a function
+name, a (possibly empty) argument list (each with optional :ref:`parameter
+attributes <paramattrs>`), optional :ref:`function attributes <fnattrs>`,
+an optional section, an optional alignment,
+an optional :ref:`comdat <langref_comdats>`,
+an optional :ref:`garbage collector name <gc>`, an optional :ref:`prefix <prefixdata>`,
+an optional :ref:`prologue <prologuedata>`, an opening
+curly brace, a list of basic blocks, and a closing curly brace.
+
+LLVM function declarations consist of the "``declare``" keyword, an
+optional :ref:`linkage type <linkage>`, an optional :ref:`visibility
+style <visibility>`, an optional :ref:`DLL storage class <dllstorageclass>`,
+an optional :ref:`calling convention <callingconv>`,
+an optional ``unnamed_addr`` attribute, a return type, an optional
+:ref:`parameter attribute <paramattrs>` for the return type, a function
+name, a possibly empty list of arguments, an optional alignment, an optional
+:ref:`garbage collector name <gc>`, an optional :ref:`prefix <prefixdata>`,
+and an optional :ref:`prologue <prologuedata>`.
+
+A function definition contains a list of basic blocks, forming the CFG (Control
+Flow Graph) for the function. Each basic block may optionally start with a label
+(giving the basic block a symbol table entry), contains a list of instructions,
+and ends with a :ref:`terminator <terminators>` instruction (such as a branch or
+function return). If an explicit label is not provided, a block is assigned an
+implicit numbered label, using the next value from the same counter as used for
+unnamed temporaries (:ref:`see above<identifiers>`). For example, if a function
+entry block does not have an explicit label, it will be assigned label "%0",
+then the first unnamed temporary in that block will be "%1", etc.
+
+The first basic block in a function is special in two ways: it is
+immediately executed on entrance to the function, and it is not allowed
+to have predecessor basic blocks (i.e. there can not be any branches to
+the entry block of a function). Because the block can have no
+predecessors, it also cannot have any :ref:`PHI nodes <i_phi>`.
+
+LLVM allows an explicit section to be specified for functions. If the
+target supports it, it will emit functions to the section specified.
+Additionally, the function can placed in a COMDAT.
+
+An explicit alignment may be specified for a function. If not present,
+or if the alignment is set to zero, the alignment of the function is set
+by the target to whatever it feels convenient. If an explicit alignment
+is specified, the function is forced to have at least that much
+alignment. All alignments must be a power of 2.
+
+If the ``unnamed_addr`` attribute is given, the address is know to not
+be significant and two identical functions can be merged.
+
+Syntax::
+
+ define [linkage] [visibility] [DLLStorageClass]
+ [cconv] [ret attrs]
+ <ResultType> @<FunctionName> ([argument list])
+ [unnamed_addr] [fn Attrs] [section "name"] [comdat [($name)]]
+ [align N] [gc] [prefix Constant] [prologue Constant] { ... }
+
+The argument list is a comma seperated sequence of arguments where each
+argument is of the following form
+
+Syntax::
+
+ <type> [parameter Attrs] [name]
+
+
+.. _langref_aliases:
+
+Aliases
+-------
+
+Aliases, unlike function or variables, don't create any new data. They
+are just a new symbol and metadata for an existing position.
+
+Aliases have a name and an aliasee that is either a global value or a
+constant expression.
+
+Aliases may have an optional :ref:`linkage type <linkage>`, an optional
+:ref:`visibility style <visibility>`, an optional :ref:`DLL storage class
+<dllstorageclass>` and an optional :ref:`tls model <tls_model>`.
+
+Syntax::
+
+ @<Name> = [Linkage] [Visibility] [DLLStorageClass] [ThreadLocal] [unnamed_addr] alias <AliaseeTy> @<Aliasee>
+
+The linkage must be one of ``private``, ``internal``, ``linkonce``, ``weak``,
+``linkonce_odr``, ``weak_odr``, ``external``. Note that some system linkers
+might not correctly handle dropping a weak symbol that is aliased.
+
+Alias that are not ``unnamed_addr`` are guaranteed to have the same address as
+the aliasee expression. ``unnamed_addr`` ones are only guaranteed to point
+to the same content.
+
+Since aliases are only a second name, some restrictions apply, of which
+some can only be checked when producing an object file:
+
+* The expression defining the aliasee must be computable at assembly
+ time. Since it is just a name, no relocations can be used.
+
+* No alias in the expression can be weak as the possibility of the
+ intermediate alias being overridden cannot be represented in an
+ object file.
+
+* No global value in the expression can be a declaration, since that
+ would require a relocation, which is not possible.
+
+.. _langref_comdats:
+
+Comdats
+-------
+
+Comdat IR provides access to COFF and ELF object file COMDAT functionality.
+
+Comdats have a name which represents the COMDAT key. All global objects that
+specify this key will only end up in the final object file if the linker chooses
+that key over some other key. Aliases are placed in the same COMDAT that their
+aliasee computes to, if any.
+
+Comdats have a selection kind to provide input on how the linker should
+choose between keys in two different object files.
+
+Syntax::
+
+ $<Name> = comdat SelectionKind
+
+The selection kind must be one of the following:
+
+``any``
+ The linker may choose any COMDAT key, the choice is arbitrary.
+``exactmatch``
+ The linker may choose any COMDAT key but the sections must contain the
+ same data.
+``largest``
+ The linker will choose the section containing the largest COMDAT key.
+``noduplicates``
+ The linker requires that only section with this COMDAT key exist.
+``samesize``
+ The linker may choose any COMDAT key but the sections must contain the
+ same amount of data.
+
+Note that the Mach-O platform doesn't support COMDATs and ELF only supports
+``any`` as a selection kind.
+
+Here is an example of a COMDAT group where a function will only be selected if
+the COMDAT key's section is the largest:
+
+.. code-block:: llvm
+
+ $foo = comdat largest
+ @foo = global i32 2, comdat($foo)
+
+ define void @bar() comdat($foo) {
+ ret void
+ }
+
+As a syntactic sugar the ``$name`` can be omitted if the name is the same as
+the global name:
+
+.. code-block:: llvm
+
+ $foo = comdat any
+ @foo = global i32 2, comdat
+
+
+In a COFF object file, this will create a COMDAT section with selection kind
+``IMAGE_COMDAT_SELECT_LARGEST`` containing the contents of the ``@foo`` symbol
+and another COMDAT section with selection kind
+``IMAGE_COMDAT_SELECT_ASSOCIATIVE`` which is associated with the first COMDAT
+section and contains the contents of the ``@bar`` symbol.
+
+There are some restrictions on the properties of the global object.
+It, or an alias to it, must have the same name as the COMDAT group when
+targeting COFF.
+The contents and size of this object may be used during link-time to determine
+which COMDAT groups get selected depending on the selection kind.
+Because the name of the object must match the name of the COMDAT group, the
+linkage of the global object must not be local; local symbols can get renamed
+if a collision occurs in the symbol table.
+
+The combined use of COMDATS and section attributes may yield surprising results.
+For example:
+
+.. code-block:: llvm
+
+ $foo = comdat any
+ $bar = comdat any
+ @g1 = global i32 42, section "sec", comdat($foo)
+ @g2 = global i32 42, section "sec", comdat($bar)
+
+From the object file perspective, this requires the creation of two sections
+with the same name. This is necessary because both globals belong to different
+COMDAT groups and COMDATs, at the object file level, are represented by
+sections.
+
+Note that certain IR constructs like global variables and functions may create
+COMDATs in the object file in addition to any which are specified using COMDAT
+IR. This arises, for example, when a global variable has linkonce_odr linkage.
+
+.. _namedmetadatastructure:
+
+Named Metadata
+--------------
+
+Named metadata is a collection of metadata. :ref:`Metadata
+nodes <metadata>` (but not metadata strings) are the only valid
+operands for a named metadata.
+
+Syntax::
+
+ ; Some unnamed metadata nodes, which are referenced by the named metadata.
+ !0 = !{!"zero"}
+ !1 = !{!"one"}
+ !2 = !{!"two"}
+ ; A named metadata.
+ !name = !{!0, !1, !2}
+
+.. _paramattrs:
+
+Parameter Attributes
+--------------------
+
+The return type and each parameter of a function type may have a set of
+*parameter attributes* associated with them. Parameter attributes are
+used to communicate additional information about the result or
+parameters of a function. Parameter attributes are considered to be part
+of the function, not of the function type, so functions with different
+parameter attributes can have the same function type.
+
+Parameter attributes are simple keywords that follow the type specified.
+If multiple parameter attributes are needed, they are space separated.
+For example:
+
+.. code-block:: llvm
+
+ declare i32 @printf(i8* noalias nocapture, ...)
+ declare i32 @atoi(i8 zeroext)
+ declare signext i8 @returns_signed_char()
+
+Note that any attributes for the function result (``nounwind``,
+``readonly``) come immediately after the argument list.
+
+Currently, only the following parameter attributes are defined:
+
+``zeroext``
+ This indicates to the code generator that the parameter or return
+ value should be zero-extended to the extent required by the target's
+ ABI (which is usually 32-bits, but is 8-bits for a i1 on x86-64) by
+ the caller (for a parameter) or the callee (for a return value).
+``signext``
+ This indicates to the code generator that the parameter or return
+ value should be sign-extended to the extent required by the target's
+ ABI (which is usually 32-bits) by the caller (for a parameter) or
+ the callee (for a return value).
+``inreg``
+ This indicates that this parameter or return value should be treated
+ in a special target-dependent fashion during while emitting code for
+ a function call or return (usually, by putting it in a register as
+ opposed to memory, though some targets use it to distinguish between
+ two different kinds of registers). Use of this attribute is
+ target-specific.
+``byval``
+ This indicates that the pointer parameter should really be passed by
+ value to the function. The attribute implies that a hidden copy of
+ the pointee is made between the caller and the callee, so the callee
+ is unable to modify the value in the caller. This attribute is only
+ valid on LLVM pointer arguments. It is generally used to pass
+ structs and arrays by value, but is also valid on pointers to
+ scalars. The copy is considered to belong to the caller not the
+ callee (for example, ``readonly`` functions should not write to
+ ``byval`` parameters). This is not a valid attribute for return
+ values.
+
+ The byval attribute also supports specifying an alignment with the
+ align attribute. It indicates the alignment of the stack slot to
+ form and the known alignment of the pointer specified to the call
+ site. If the alignment is not specified, then the code generator
+ makes a target-specific assumption.
+
+.. _attr_inalloca:
+
+``inalloca``
+
+ The ``inalloca`` argument attribute allows the caller to take the
+ address of outgoing stack arguments. An ``inalloca`` argument must
+ be a pointer to stack memory produced by an ``alloca`` instruction.
+ The alloca, or argument allocation, must also be tagged with the
+ inalloca keyword. Only the last argument may have the ``inalloca``
+ attribute, and that argument is guaranteed to be passed in memory.
+
+ An argument allocation may be used by a call at most once because
+ the call may deallocate it. The ``inalloca`` attribute cannot be
+ used in conjunction with other attributes that affect argument
+ storage, like ``inreg``, ``nest``, ``sret``, or ``byval``. The
+ ``inalloca`` attribute also disables LLVM's implicit lowering of
+ large aggregate return values, which means that frontend authors
+ must lower them with ``sret`` pointers.
+
+ When the call site is reached, the argument allocation must have
+ been the most recent stack allocation that is still live, or the
+ results are undefined. It is possible to allocate additional stack
+ space after an argument allocation and before its call site, but it
+ must be cleared off with :ref:`llvm.stackrestore
+ <int_stackrestore>`.
+
+ See :doc:`InAlloca` for more information on how to use this
+ attribute.
+
+``sret``
+ This indicates that the pointer parameter specifies the address of a
+ structure that is the return value of the function in the source
+ program. This pointer must be guaranteed by the caller to be valid:
+ loads and stores to the structure may be assumed by the callee
+ not to trap and to be properly aligned. This may only be applied to
+ the first parameter. This is not a valid attribute for return
+ values.
+
+``align <n>``
+ This indicates that the pointer value may be assumed by the optimizer to
+ have the specified alignment.
+
+ Note that this attribute has additional semantics when combined with the
+ ``byval`` attribute.
+
+.. _noalias:
+
+``noalias``
+ This indicates that objects accessed via pointer values
+ :ref:`based <pointeraliasing>` on the argument or return value are not also
+ accessed, during the execution of the function, via pointer values not
+ *based* on the argument or return value. The attribute on a return value
+ also has additional semantics described below. The caller shares the
+ responsibility with the callee for ensuring that these requirements are met.
+ For further details, please see the discussion of the NoAlias response in
+ :ref:`alias analysis <Must, May, or No>`.
+
+ Note that this definition of ``noalias`` is intentionally similar
+ to the definition of ``restrict`` in C99 for function arguments.
+
+ For function return values, C99's ``restrict`` is not meaningful,
+ while LLVM's ``noalias`` is. Furthermore, the semantics of the ``noalias``
+ attribute on return values are stronger than the semantics of the attribute
+ when used on function arguments. On function return values, the ``noalias``
+ attribute indicates that the function acts like a system memory allocation
+ function, returning a pointer to allocated storage disjoint from the
+ storage for any other object accessible to the caller.
+
+``nocapture``
+ This indicates that the callee does not make any copies of the
+ pointer that outlive the callee itself. This is not a valid
+ attribute for return values.
+
+.. _nest:
+
+``nest``
+ This indicates that the pointer parameter can be excised using the
+ :ref:`trampoline intrinsics <int_trampoline>`. This is not a valid
+ attribute for return values and can only be applied to one parameter.
+
+``returned``
+ This indicates that the function always returns the argument as its return
+ value. This is an optimization hint to the code generator when generating
+ the caller, allowing tail call optimization and omission of register saves
+ and restores in some cases; it is not checked or enforced when generating
+ the callee. The parameter and the function return type must be valid
+ operands for the :ref:`bitcast instruction <i_bitcast>`. This is not a
+ valid attribute for return values and can only be applied to one parameter.
+
+``nonnull``
+ This indicates that the parameter or return pointer is not null. This
+ attribute may only be applied to pointer typed parameters. This is not
+ checked or enforced by LLVM, the caller must ensure that the pointer
+ passed in is non-null, or the callee must ensure that the returned pointer
+ is non-null.
+
+``dereferenceable(<n>)``
+ This indicates that the parameter or return pointer is dereferenceable. This
+ attribute may only be applied to pointer typed parameters. A pointer that
+ is dereferenceable can be loaded from speculatively without a risk of
+ trapping. The number of bytes known to be dereferenceable must be provided
+ in parentheses. It is legal for the number of bytes to be less than the
+ size of the pointee type. The ``nonnull`` attribute does not imply
+ dereferenceability (consider a pointer to one element past the end of an
+ array), however ``dereferenceable(<n>)`` does imply ``nonnull`` in
+ ``addrspace(0)`` (which is the default address space).
+
+.. _gc:
+
+Garbage Collector Names
+-----------------------
+
+Each function may specify a garbage collector name, which is simply a
+string:
+
+.. code-block:: llvm
+
+ define void @f() gc "name" { ... }
+
+The compiler declares the supported values of *name*. Specifying a
+collector will cause the compiler to alter its output in order to
+support the named garbage collection algorithm.
+
+.. _prefixdata:
+
+Prefix Data
+-----------
+
+Prefix data is data associated with a function which the code
+generator will emit immediately before the function's entrypoint.
+The purpose of this feature is to allow frontends to associate
+language-specific runtime metadata with specific functions and make it
+available through the function pointer while still allowing the
+function pointer to be called.
+
+To access the data for a given function, a program may bitcast the
+function pointer to a pointer to the constant's type and dereference
+index -1. This implies that the IR symbol points just past the end of
+the prefix data. For instance, take the example of a function annotated
+with a single ``i32``,
+
+.. code-block:: llvm
+
+ define void @f() prefix i32 123 { ... }
+
+The prefix data can be referenced as,
+
+.. code-block:: llvm
+
+ %0 = bitcast *void () @f to *i32
+ %a = getelementptr inbounds *i32 %0, i32 -1
+ %b = load i32* %a
+
+Prefix data is laid out as if it were an initializer for a global variable
+of the prefix data's type. The function will be placed such that the
+beginning of the prefix data is aligned. This means that if the size
+of the prefix data is not a multiple of the alignment size, the
+function's entrypoint will not be aligned. If alignment of the
+function's entrypoint is desired, padding must be added to the prefix
+data.
+
+A function may have prefix data but no body. This has similar semantics
+to the ``available_externally`` linkage in that the data may be used by the
+optimizers but will not be emitted in the object file.
+
+.. _prologuedata:
+
+Prologue Data
+-------------
+
+The ``prologue`` attribute allows arbitrary code (encoded as bytes) to
+be inserted prior to the function body. This can be used for enabling
+function hot-patching and instrumentation.
+
+To maintain the semantics of ordinary function calls, the prologue data must
+have a particular format. Specifically, it must begin with a sequence of
+bytes which decode to a sequence of machine instructions, valid for the
+module's target, which transfer control to the point immediately succeeding
+the prologue data, without performing any other visible action. This allows
+the inliner and other passes to reason about the semantics of the function
+definition without needing to reason about the prologue data. Obviously this
+makes the format of the prologue data highly target dependent.
+
+A trivial example of valid prologue data for the x86 architecture is ``i8 144``,
+which encodes the ``nop`` instruction:
+
+.. code-block:: llvm
+
+ define void @f() prologue i8 144 { ... }
+
+Generally prologue data can be formed by encoding a relative branch instruction
+which skips the metadata, as in this example of valid prologue data for the
+x86_64 architecture, where the first two bytes encode ``jmp .+10``:
+
+.. code-block:: llvm
+
+ %0 = type <{ i8, i8, i8* }>
+
+ define void @f() prologue %0 <{ i8 235, i8 8, i8* @md}> { ... }
+
+A function may have prologue data but no body. This has similar semantics
+to the ``available_externally`` linkage in that the data may be used by the
+optimizers but will not be emitted in the object file.
+
+.. _attrgrp:
+
+Attribute Groups
+----------------
+
+Attribute groups are groups of attributes that are referenced by objects within
+the IR. They are important for keeping ``.ll`` files readable, because a lot of
+functions will use the same set of attributes. In the degenerative case of a
+``.ll`` file that corresponds to a single ``.c`` file, the single attribute
+group will capture the important command line flags used to build that file.
+
+An attribute group is a module-level object. To use an attribute group, an
+object references the attribute group's ID (e.g. ``#37``). An object may refer
+to more than one attribute group. In that situation, the attributes from the
+different groups are merged.
+
+Here is an example of attribute groups for a function that should always be
+inlined, has a stack alignment of 4, and which shouldn't use SSE instructions:
+
+.. code-block:: llvm
+
+ ; Target-independent attributes:
+ attributes #0 = { alwaysinline alignstack=4 }
+
+ ; Target-dependent attributes:
+ attributes #1 = { "no-sse" }
+
+ ; Function @f has attributes: alwaysinline, alignstack=4, and "no-sse".
+ define void @f() #0 #1 { ... }
+
+.. _fnattrs:
+
+Function Attributes
+-------------------
+
+Function attributes are set to communicate additional information about
+a function. Function attributes are considered to be part of the
+function, not of the function type, so functions with different function
+attributes can have the same function type.
+
+Function attributes are simple keywords that follow the type specified.
+If multiple attributes are needed, they are space separated. For
+example:
+
+.. code-block:: llvm
+
+ define void @f() noinline { ... }
+ define void @f() alwaysinline { ... }
+ define void @f() alwaysinline optsize { ... }
+ define void @f() optsize { ... }
+
+``alignstack(<n>)``
+ This attribute indicates that, when emitting the prologue and
+ epilogue, the backend should forcibly align the stack pointer.
+ Specify the desired alignment, which must be a power of two, in
+ parentheses.
+``alwaysinline``
+ This attribute indicates that the inliner should attempt to inline
+ this function into callers whenever possible, ignoring any active
+ inlining size threshold for this caller.
+``builtin``
+ This indicates that the callee function at a call site should be
+ recognized as a built-in function, even though the function's declaration
+ uses the ``nobuiltin`` attribute. This is only valid at call sites for
+ direct calls to functions that are declared with the ``nobuiltin``
+ attribute.
+``cold``
+ This attribute indicates that this function is rarely called. When
+ computing edge weights, basic blocks post-dominated by a cold
+ function call are also considered to be cold; and, thus, given low
+ weight.
+``inlinehint``
+ This attribute indicates that the source code contained a hint that
+ inlining this function is desirable (such as the "inline" keyword in
+ C/C++). It is just a hint; it imposes no requirements on the
+ inliner.
+``jumptable``
+ This attribute indicates that the function should be added to a
+ jump-instruction table at code-generation time, and that all address-taken
+ references to this function should be replaced with a reference to the
+ appropriate jump-instruction-table function pointer. Note that this creates
+ a new pointer for the original function, which means that code that depends
+ on function-pointer identity can break. So, any function annotated with
+ ``jumptable`` must also be ``unnamed_addr``.
+``minsize``
+ This attribute suggests that optimization passes and code generator
+ passes make choices that keep the code size of this function as small
+ as possible and perform optimizations that may sacrifice runtime
+ performance in order to minimize the size of the generated code.
+``naked``
+ This attribute disables prologue / epilogue emission for the
+ function. This can have very system-specific consequences.
+``nobuiltin``
+ This indicates that the callee function at a call site is not recognized as
+ a built-in function. LLVM will retain the original call and not replace it
+ with equivalent code based on the semantics of the built-in function, unless
+ the call site uses the ``builtin`` attribute. This is valid at call sites
+ and on function declarations and definitions.
+``noduplicate``
+ This attribute indicates that calls to the function cannot be
+ duplicated. A call to a ``noduplicate`` function may be moved
+ within its parent function, but may not be duplicated within
+ its parent function.
+
+ A function containing a ``noduplicate`` call may still
+ be an inlining candidate, provided that the call is not
+ duplicated by inlining. That implies that the function has
+ internal linkage and only has one call site, so the original
+ call is dead after inlining.
+``noimplicitfloat``
+ This attributes disables implicit floating point instructions.
+``noinline``
+ This attribute indicates that the inliner should never inline this
+ function in any situation. This attribute may not be used together
+ with the ``alwaysinline`` attribute.
+``nonlazybind``
+ This attribute suppresses lazy symbol binding for the function. This
+ may make calls to the function faster, at the cost of extra program
+ startup time if the function is not called during program startup.
+``noredzone``
+ This attribute indicates that the code generator should not use a
+ red zone, even if the target-specific ABI normally permits it.
+``noreturn``
+ This function attribute indicates that the function never returns
+ normally. This produces undefined behavior at runtime if the
+ function ever does dynamically return.
+``nounwind``
+ This function attribute indicates that the function never returns
+ with an unwind or exceptional control flow. If the function does
+ unwind, its runtime behavior is undefined.
+``optnone``
+ This function attribute indicates that the function is not optimized
+ by any optimization or code generator passes with the
+ exception of interprocedural optimization passes.
+ This attribute cannot be used together with the ``alwaysinline``
+ attribute; this attribute is also incompatible
+ with the ``minsize`` attribute and the ``optsize`` attribute.
+
+ This attribute requires the ``noinline`` attribute to be specified on
+ the function as well, so the function is never inlined into any caller.
+ Only functions with the ``alwaysinline`` attribute are valid
+ candidates for inlining into the body of this function.
+``optsize``
+ This attribute suggests that optimization passes and code generator
+ passes make choices that keep the code size of this function low,
+ and otherwise do optimizations specifically to reduce code size as
+ long as they do not significantly impact runtime performance.
+``readnone``
+ On a function, this attribute indicates that the function computes its
+ result (or decides to unwind an exception) based strictly on its arguments,
+ without dereferencing any pointer arguments or otherwise accessing
+ any mutable state (e.g. memory, control registers, etc) visible to
+ caller functions. It does not write through any pointer arguments
+ (including ``byval`` arguments) and never changes any state visible
+ to callers. This means that it cannot unwind exceptions by calling
+ the ``C++`` exception throwing methods.
+
+ On an argument, this attribute indicates that the function does not
+ dereference that pointer argument, even though it may read or write the
+ memory that the pointer points to if accessed through other pointers.
+``readonly``
+ On a function, this attribute indicates that the function does not write
+ through any pointer arguments (including ``byval`` arguments) or otherwise
+ modify any state (e.g. memory, control registers, etc) visible to
+ caller functions. It may dereference pointer arguments and read
+ state that may be set in the caller. A readonly function always
+ returns the same value (or unwinds an exception identically) when
+ called with the same set of arguments and global state. It cannot
+ unwind an exception by calling the ``C++`` exception throwing
+ methods.
+
+ On an argument, this attribute indicates that the function does not write
+ through this pointer argument, even though it may write to the memory that
+ the pointer points to.
+``returns_twice``
+ This attribute indicates that this function can return twice. The C
+ ``setjmp`` is an example of such a function. The compiler disables
+ some optimizations (like tail calls) in the caller of these
+ functions.
+``sanitize_address``
+ This attribute indicates that AddressSanitizer checks
+ (dynamic address safety analysis) are enabled for this function.
+``sanitize_memory``
+ This attribute indicates that MemorySanitizer checks (dynamic detection
+ of accesses to uninitialized memory) are enabled for this function.
+``sanitize_thread``
+ This attribute indicates that ThreadSanitizer checks
+ (dynamic thread safety analysis) are enabled for this function.
+``ssp``
+ This attribute indicates that the function should emit a stack
+ smashing protector. It is in the form of a "canary" --- a random value
+ placed on the stack before the local variables that's checked upon
+ return from the function to see if it has been overwritten. A
+ heuristic is used to determine if a function needs stack protectors
+ or not. The heuristic used will enable protectors for functions with:
+
+ - Character arrays larger than ``ssp-buffer-size`` (default 8).
+ - Aggregates containing character arrays larger than ``ssp-buffer-size``.
+ - Calls to alloca() with variable sizes or constant sizes greater than
+ ``ssp-buffer-size``.
+
+ Variables that are identified as requiring a protector will be arranged
+ on the stack such that they are adjacent to the stack protector guard.
+
+ If a function that has an ``ssp`` attribute is inlined into a
+ function that doesn't have an ``ssp`` attribute, then the resulting
+ function will have an ``ssp`` attribute.
+``sspreq``
+ This attribute indicates that the function should *always* emit a
+ stack smashing protector. This overrides the ``ssp`` function
+ attribute.
+
+ Variables that are identified as requiring a protector will be arranged
+ on the stack such that they are adjacent to the stack protector guard.
+ The specific layout rules are:
+
+ #. Large arrays and structures containing large arrays
+ (``>= ssp-buffer-size``) are closest to the stack protector.
+ #. Small arrays and structures containing small arrays
+ (``< ssp-buffer-size``) are 2nd closest to the protector.
+ #. Variables that have had their address taken are 3rd closest to the
+ protector.
+
+ If a function that has an ``sspreq`` attribute is inlined into a
+ function that doesn't have an ``sspreq`` attribute or which has an
+ ``ssp`` or ``sspstrong`` attribute, then the resulting function will have
+ an ``sspreq`` attribute.
+``sspstrong``
+ This attribute indicates that the function should emit a stack smashing
+ protector. This attribute causes a strong heuristic to be used when
+ determining if a function needs stack protectors. The strong heuristic
+ will enable protectors for functions with:
+
+ - Arrays of any size and type
+ - Aggregates containing an array of any size and type.
+ - Calls to alloca().
+ - Local variables that have had their address taken.
+
+ Variables that are identified as requiring a protector will be arranged
+ on the stack such that they are adjacent to the stack protector guard.
+ The specific layout rules are:
+
+ #. Large arrays and structures containing large arrays
+ (``>= ssp-buffer-size``) are closest to the stack protector.
+ #. Small arrays and structures containing small arrays
+ (``< ssp-buffer-size``) are 2nd closest to the protector.
+ #. Variables that have had their address taken are 3rd closest to the
+ protector.
+
+ This overrides the ``ssp`` function attribute.
+
+ If a function that has an ``sspstrong`` attribute is inlined into a
+ function that doesn't have an ``sspstrong`` attribute, then the
+ resulting function will have an ``sspstrong`` attribute.
+``uwtable``
+ This attribute indicates that the ABI being targeted requires that
+ an unwind table entry be produce for this function even if we can
+ show that no exceptions passes by it. This is normally the case for
+ the ELF x86-64 abi, but it can be disabled for some compilation
+ units.
+
+.. _moduleasm:
+
+Module-Level Inline Assembly
+----------------------------
+
+Modules may contain "module-level inline asm" blocks, which corresponds
+to the GCC "file scope inline asm" blocks. These blocks are internally
+concatenated by LLVM and treated as a single unit, but may be separated
+in the ``.ll`` file if desired. The syntax is very simple:
+
+.. code-block:: llvm
+
+ module asm "inline asm code goes here"
+ module asm "more can go here"
+
+The strings can contain any character by escaping non-printable
+characters. The escape sequence used is simply "\\xx" where "xx" is the
+two digit hex code for the number.
+
+The inline asm code is simply printed to the machine code .s file when
+assembly code is generated.
+
+.. _langref_datalayout:
+
+Data Layout
+-----------
+
+A module may specify a target specific data layout string that specifies
+how data is to be laid out in memory. The syntax for the data layout is
+simply:
+
+.. code-block:: llvm
+
+ target datalayout = "layout specification"
+
+The *layout specification* consists of a list of specifications
+separated by the minus sign character ('-'). Each specification starts
+with a letter and may include other information after the letter to
+define some aspect of the data layout. The specifications accepted are
+as follows:
+
+``E``
+ Specifies that the target lays out data in big-endian form. That is,
+ the bits with the most significance have the lowest address
+ location.
+``e``
+ Specifies that the target lays out data in little-endian form. That
+ is, the bits with the least significance have the lowest address
+ location.
+``S<size>``
+ Specifies the natural alignment of the stack in bits. Alignment
+ promotion of stack variables is limited to the natural stack
+ alignment to avoid dynamic stack realignment. The stack alignment
+ must be a multiple of 8-bits. If omitted, the natural stack
+ alignment defaults to "unspecified", which does not prevent any
+ alignment promotions.
+``p[n]:<size>:<abi>:<pref>``
+ This specifies the *size* of a pointer and its ``<abi>`` and
+ ``<pref>``\erred alignments for address space ``n``. All sizes are in
+ bits. The address space, ``n`` is optional, and if not specified,
+ denotes the default address space 0. The value of ``n`` must be
+ in the range [1,2^23).
+``i<size>:<abi>:<pref>``
+ This specifies the alignment for an integer type of a given bit
+ ``<size>``. The value of ``<size>`` must be in the range [1,2^23).
+``v<size>:<abi>:<pref>``
+ This specifies the alignment for a vector type of a given bit
+ ``<size>``.
+``f<size>:<abi>:<pref>``
+ This specifies the alignment for a floating point type of a given bit
+ ``<size>``. Only values of ``<size>`` that are supported by the target
+ will work. 32 (float) and 64 (double) are supported on all targets; 80
+ or 128 (different flavors of long double) are also supported on some
+ targets.
+``a:<abi>:<pref>``
+ This specifies the alignment for an object of aggregate type.
+``m:<mangling>``
+ If present, specifies that llvm names are mangled in the output. The
+ options are
+
+ * ``e``: ELF mangling: Private symbols get a ``.L`` prefix.
+ * ``m``: Mips mangling: Private symbols get a ``$`` prefix.
+ * ``o``: Mach-O mangling: Private symbols get ``L`` prefix. Other
+ symbols get a ``_`` prefix.
+ * ``w``: Windows COFF prefix: Similar to Mach-O, but stdcall and fastcall
+ functions also get a suffix based on the frame size.
+``n<size1>:<size2>:<size3>...``
+ This specifies a set of native integer widths for the target CPU in
+ bits. For example, it might contain ``n32`` for 32-bit PowerPC,
+ ``n32:64`` for PowerPC 64, or ``n8:16:32:64`` for X86-64. Elements of
+ this set are considered to support most general arithmetic operations
+ efficiently.
+
+On every specification that takes a ``<abi>:<pref>``, specifying the
+``<pref>`` alignment is optional. If omitted, the preceding ``:``
+should be omitted too and ``<pref>`` will be equal to ``<abi>``.
+
+When constructing the data layout for a given target, LLVM starts with a
+default set of specifications which are then (possibly) overridden by
+the specifications in the ``datalayout`` keyword. The default
+specifications are given in this list:
+
+- ``E`` - big endian
+- ``p:64:64:64`` - 64-bit pointers with 64-bit alignment.
+- ``p[n]:64:64:64`` - Other address spaces are assumed to be the
+ same as the default address space.
+- ``S0`` - natural stack alignment is unspecified
+- ``i1:8:8`` - i1 is 8-bit (byte) aligned
+- ``i8:8:8`` - i8 is 8-bit (byte) aligned
+- ``i16:16:16`` - i16 is 16-bit aligned
+- ``i32:32:32`` - i32 is 32-bit aligned
+- ``i64:32:64`` - i64 has ABI alignment of 32-bits but preferred
+ alignment of 64-bits
+- ``f16:16:16`` - half is 16-bit aligned
+- ``f32:32:32`` - float is 32-bit aligned
+- ``f64:64:64`` - double is 64-bit aligned
+- ``f128:128:128`` - quad is 128-bit aligned
+- ``v64:64:64`` - 64-bit vector is 64-bit aligned
+- ``v128:128:128`` - 128-bit vector is 128-bit aligned
+- ``a:0:64`` - aggregates are 64-bit aligned
+
+When LLVM is determining the alignment for a given type, it uses the
+following rules:
+
+#. If the type sought is an exact match for one of the specifications,
+ that specification is used.
+#. If no match is found, and the type sought is an integer type, then
+ the smallest integer type that is larger than the bitwidth of the
+ sought type is used. If none of the specifications are larger than
+ the bitwidth then the largest integer type is used. For example,
+ given the default specifications above, the i7 type will use the
+ alignment of i8 (next largest) while both i65 and i256 will use the
+ alignment of i64 (largest specified).
+#. If no match is found, and the type sought is a vector type, then the
+ largest vector type that is smaller than the sought vector type will
+ be used as a fall back. This happens because <128 x double> can be
+ implemented in terms of 64 <2 x double>, for example.
+
+The function of the data layout string may not be what you expect.
+Notably, this is not a specification from the frontend of what alignment
+the code generator should use.
+
+Instead, if specified, the target data layout is required to match what
+the ultimate *code generator* expects. This string is used by the
+mid-level optimizers to improve code, and this only works if it matches
+what the ultimate code generator uses. If you would like to generate IR
+that does not embed this target-specific detail into the IR, then you
+don't have to specify the string. This will disable some optimizations
+that require precise layout information, but this also prevents those
+optimizations from introducing target specificity into the IR.
+
+.. _langref_triple:
+
+Target Triple
+-------------
+
+A module may specify a target triple string that describes the target
+host. The syntax for the target triple is simply:
+
+.. code-block:: llvm
+
+ target triple = "x86_64-apple-macosx10.7.0"
+
+The *target triple* string consists of a series of identifiers delimited
+by the minus sign character ('-'). The canonical forms are:
+
+::
+
+ ARCHITECTURE-VENDOR-OPERATING_SYSTEM
+ ARCHITECTURE-VENDOR-OPERATING_SYSTEM-ENVIRONMENT
+
+This information is passed along to the backend so that it generates
+code for the proper architecture. It's possible to override this on the
+command line with the ``-mtriple`` command line option.
+
+.. _pointeraliasing:
+
+Pointer Aliasing Rules
+----------------------
+
+Any memory access must be done through a pointer value associated with
+an address range of the memory access, otherwise the behavior is
+undefined. Pointer values are associated with address ranges according
+to the following rules:
+
+- A pointer value is associated with the addresses associated with any
+ value it is *based* on.
+- An address of a global variable is associated with the address range
+ of the variable's storage.
+- The result value of an allocation instruction is associated with the
+ address range of the allocated storage.
+- A null pointer in the default address-space is associated with no
+ address.
+- An integer constant other than zero or a pointer value returned from
+ a function not defined within LLVM may be associated with address
+ ranges allocated through mechanisms other than those provided by
+ LLVM. Such ranges shall not overlap with any ranges of addresses
+ allocated by mechanisms provided by LLVM.
+
+A pointer value is *based* on another pointer value according to the
+following rules:
+
+- A pointer value formed from a ``getelementptr`` operation is *based*
+ on the first operand of the ``getelementptr``.
+- The result value of a ``bitcast`` is *based* on the operand of the
+ ``bitcast``.
+- A pointer value formed by an ``inttoptr`` is *based* on all pointer
+ values that contribute (directly or indirectly) to the computation of
+ the pointer's value.
+- The "*based* on" relationship is transitive.
+
+Note that this definition of *"based"* is intentionally similar to the
+definition of *"based"* in C99, though it is slightly weaker.
+
+LLVM IR does not associate types with memory. The result type of a
+``load`` merely indicates the size and alignment of the memory from
+which to load, as well as the interpretation of the value. The first
+operand type of a ``store`` similarly only indicates the size and
+alignment of the store.
+
+Consequently, type-based alias analysis, aka TBAA, aka
+``-fstrict-aliasing``, is not applicable to general unadorned LLVM IR.
+:ref:`Metadata <metadata>` may be used to encode additional information
+which specialized optimization passes may use to implement type-based
+alias analysis.
+
+.. _volatile:
+
+Volatile Memory Accesses
+------------------------
+
+Certain memory accesses, such as :ref:`load <i_load>`'s,
+:ref:`store <i_store>`'s, and :ref:`llvm.memcpy <int_memcpy>`'s may be
+marked ``volatile``. The optimizers must not change the number of
+volatile operations or change their order of execution relative to other
+volatile operations. The optimizers *may* change the order of volatile
+operations relative to non-volatile operations. This is not Java's
+"volatile" and has no cross-thread synchronization behavior.
+
+IR-level volatile loads and stores cannot safely be optimized into
+llvm.memcpy or llvm.memmove intrinsics even when those intrinsics are
+flagged volatile. Likewise, the backend should never split or merge
+target-legal volatile load/store instructions.
+
+.. admonition:: Rationale
+
+ Platforms may rely on volatile loads and stores of natively supported
+ data width to be executed as single instruction. For example, in C
+ this holds for an l-value of volatile primitive type with native
+ hardware support, but not necessarily for aggregate types. The
+ frontend upholds these expectations, which are intentionally
+ unspecified in the IR. The rules above ensure that IR transformation
+ do not violate the frontend's contract with the language.
+
+.. _memmodel:
+
+Memory Model for Concurrent Operations
+--------------------------------------
+
+The LLVM IR does not define any way to start parallel threads of
+execution or to register signal handlers. Nonetheless, there are
+platform-specific ways to create them, and we define LLVM IR's behavior
+in their presence. This model is inspired by the C++0x memory model.
+
+For a more informal introduction to this model, see the :doc:`Atomics`.
+
+We define a *happens-before* partial order as the least partial order
+that
+
+- Is a superset of single-thread program order, and
+- When a *synchronizes-with* ``b``, includes an edge from ``a`` to
+ ``b``. *Synchronizes-with* pairs are introduced by platform-specific
+ techniques, like pthread locks, thread creation, thread joining,
+ etc., and by atomic instructions. (See also :ref:`Atomic Memory Ordering
+ Constraints <ordering>`).
+
+Note that program order does not introduce *happens-before* edges
+between a thread and signals executing inside that thread.
+
+Every (defined) read operation (load instructions, memcpy, atomic
+loads/read-modify-writes, etc.) R reads a series of bytes written by
+(defined) write operations (store instructions, atomic
+stores/read-modify-writes, memcpy, etc.). For the purposes of this
+section, initialized globals are considered to have a write of the
+initializer which is atomic and happens before any other read or write
+of the memory in question. For each byte of a read R, R\ :sub:`byte`
+may see any write to the same byte, except:
+
+- If write\ :sub:`1` happens before write\ :sub:`2`, and
+ write\ :sub:`2` happens before R\ :sub:`byte`, then
+ R\ :sub:`byte` does not see write\ :sub:`1`.
+- If R\ :sub:`byte` happens before write\ :sub:`3`, then
+ R\ :sub:`byte` does not see write\ :sub:`3`.
+
+Given that definition, R\ :sub:`byte` is defined as follows:
+
+- If R is volatile, the result is target-dependent. (Volatile is
+ supposed to give guarantees which can support ``sig_atomic_t`` in
+ C/C++, and may be used for accesses to addresses that do not behave
+ like normal memory. It does not generally provide cross-thread
+ synchronization.)
+- Otherwise, if there is no write to the same byte that happens before
+ R\ :sub:`byte`, R\ :sub:`byte` returns ``undef`` for that byte.
+- Otherwise, if R\ :sub:`byte` may see exactly one write,
+ R\ :sub:`byte` returns the value written by that write.
+- Otherwise, if R is atomic, and all the writes R\ :sub:`byte` may
+ see are atomic, it chooses one of the values written. See the :ref:`Atomic
+ Memory Ordering Constraints <ordering>` section for additional
+ constraints on how the choice is made.
+- Otherwise R\ :sub:`byte` returns ``undef``.
+
+R returns the value composed of the series of bytes it read. This
+implies that some bytes within the value may be ``undef`` **without**
+the entire value being ``undef``. Note that this only defines the
+semantics of the operation; it doesn't mean that targets will emit more
+than one instruction to read the series of bytes.
+
+Note that in cases where none of the atomic intrinsics are used, this
+model places only one restriction on IR transformations on top of what
+is required for single-threaded execution: introducing a store to a byte
+which might not otherwise be stored is not allowed in general.
+(Specifically, in the case where another thread might write to and read
+from an address, introducing a store can change a load that may see
+exactly one write into a load that may see multiple writes.)
+
+.. _ordering:
+
+Atomic Memory Ordering Constraints
+----------------------------------
+
+Atomic instructions (:ref:`cmpxchg <i_cmpxchg>`,
+:ref:`atomicrmw <i_atomicrmw>`, :ref:`fence <i_fence>`,
+:ref:`atomic load <i_load>`, and :ref:`atomic store <i_store>`) take
+ordering parameters that determine which other atomic instructions on
+the same address they *synchronize with*. These semantics are borrowed
+from Java and C++0x, but are somewhat more colloquial. If these
+descriptions aren't precise enough, check those specs (see spec
+references in the :doc:`atomics guide <Atomics>`).
+:ref:`fence <i_fence>` instructions treat these orderings somewhat
+differently since they don't take an address. See that instruction's
+documentation for details.
+
+For a simpler introduction to the ordering constraints, see the
+:doc:`Atomics`.
+
+``unordered``
+ The set of values that can be read is governed by the happens-before
+ partial order. A value cannot be read unless some operation wrote
+ it. This is intended to provide a guarantee strong enough to model
+ Java's non-volatile shared variables. This ordering cannot be
+ specified for read-modify-write operations; it is not strong enough
+ to make them atomic in any interesting way.
+``monotonic``
+ In addition to the guarantees of ``unordered``, there is a single
+ total order for modifications by ``monotonic`` operations on each
+ address. All modification orders must be compatible with the
+ happens-before order. There is no guarantee that the modification
+ orders can be combined to a global total order for the whole program
+ (and this often will not be possible). The read in an atomic
+ read-modify-write operation (:ref:`cmpxchg <i_cmpxchg>` and
+ :ref:`atomicrmw <i_atomicrmw>`) reads the value in the modification
+ order immediately before the value it writes. If one atomic read
+ happens before another atomic read of the same address, the later
+ read must see the same value or a later value in the address's
+ modification order. This disallows reordering of ``monotonic`` (or
+ stronger) operations on the same address. If an address is written
+ ``monotonic``-ally by one thread, and other threads ``monotonic``-ally
+ read that address repeatedly, the other threads must eventually see
+ the write. This corresponds to the C++0x/C1x
+ ``memory_order_relaxed``.
+``acquire``
+ In addition to the guarantees of ``monotonic``, a
+ *synchronizes-with* edge may be formed with a ``release`` operation.
+ This is intended to model C++'s ``memory_order_acquire``.
+``release``
+ In addition to the guarantees of ``monotonic``, if this operation
+ writes a value which is subsequently read by an ``acquire``
+ operation, it *synchronizes-with* that operation. (This isn't a
+ complete description; see the C++0x definition of a release
+ sequence.) This corresponds to the C++0x/C1x
+ ``memory_order_release``.
+``acq_rel`` (acquire+release)
+ Acts as both an ``acquire`` and ``release`` operation on its
+ address. This corresponds to the C++0x/C1x ``memory_order_acq_rel``.
+``seq_cst`` (sequentially consistent)
+ In addition to the guarantees of ``acq_rel`` (``acquire`` for an
+ operation that only reads, ``release`` for an operation that only
+ writes), there is a global total order on all
+ sequentially-consistent operations on all addresses, which is
+ consistent with the *happens-before* partial order and with the
+ modification orders of all the affected addresses. Each
+ sequentially-consistent read sees the last preceding write to the
+ same address in this global order. This corresponds to the C++0x/C1x
+ ``memory_order_seq_cst`` and Java volatile.
+
+.. _singlethread:
+
+If an atomic operation is marked ``singlethread``, it only *synchronizes
+with* or participates in modification and seq\_cst total orderings with
+other operations running in the same thread (for example, in signal
+handlers).
+
+.. _fastmath:
+
+Fast-Math Flags
+---------------
+
+LLVM IR floating-point binary ops (:ref:`fadd <i_fadd>`,
+:ref:`fsub <i_fsub>`, :ref:`fmul <i_fmul>`, :ref:`fdiv <i_fdiv>`,
+:ref:`frem <i_frem>`) have the following flags that can set to enable
+otherwise unsafe floating point operations
+
+``nnan``
+ No NaNs - Allow optimizations to assume the arguments and result are not
+ NaN. Such optimizations are required to retain defined behavior over
+ NaNs, but the value of the result is undefined.
+
+``ninf``
+ No Infs - Allow optimizations to assume the arguments and result are not
+ +/-Inf. Such optimizations are required to retain defined behavior over
+ +/-Inf, but the value of the result is undefined.
+
+``nsz``
+ No Signed Zeros - Allow optimizations to treat the sign of a zero
+ argument or result as insignificant.
+
+``arcp``
+ Allow Reciprocal - Allow optimizations to use the reciprocal of an
+ argument rather than perform division.
+
+``fast``
+ Fast - Allow algebraically equivalent transformations that may
+ dramatically change results in floating point (e.g. reassociate). This
+ flag implies all the others.
+
+.. _uselistorder:
+
+Use-list Order Directives
+-------------------------
+
+Use-list directives encode the in-memory order of each use-list, allowing the
+order to be recreated. ``<order-indexes>`` is a comma-separated list of
+indexes that are assigned to the referenced value's uses. The referenced
+value's use-list is immediately sorted by these indexes.
+
+Use-list directives may appear at function scope or global scope. They are not
+instructions, and have no effect on the semantics of the IR. When they're at
+function scope, they must appear after the terminator of the final basic block.
+
+If basic blocks have their address taken via ``blockaddress()`` expressions,
+``uselistorder_bb`` can be used to reorder their use-lists from outside their
+function's scope.
+
+:Syntax:
+
+::
+
+ uselistorder <ty> <value>, { <order-indexes> }
+ uselistorder_bb @function, %block { <order-indexes> }
+
+:Examples:
+
+::
+
+ define void @foo(i32 %arg1, i32 %arg2) {
+ entry:
+ ; ... instructions ...
+ bb:
+ ; ... instructions ...
+
+ ; At function scope.
+ uselistorder i32 %arg1, { 1, 0, 2 }
+ uselistorder label %bb, { 1, 0 }
+ }
+
+ ; At global scope.
+ uselistorder i32* @global, { 1, 2, 0 }
+ uselistorder i32 7, { 1, 0 }
+ uselistorder i32 (i32) @bar, { 1, 0 }
+ uselistorder_bb @foo, %bb, { 5, 1, 3, 2, 0, 4 }
+
+.. _typesystem:
+
+Type System
+===========
+
+The LLVM type system is one of the most important features of the
+intermediate representation. Being typed enables a number of
+optimizations to be performed on the intermediate representation
+directly, without having to do extra analyses on the side before the
+transformation. A strong type system makes it easier to read the
+generated code and enables novel analyses and transformations that are
+not feasible to perform on normal three address code representations.
+
+.. _t_void:
+
+Void Type
+---------
+
+:Overview:
+
+
+The void type does not represent any value and has no size.
+
+:Syntax:
+
+
+::
+
+ void
+
+
+.. _t_function:
+
+Function Type
+-------------
+
+:Overview:
+
+
+The function type can be thought of as a function signature. It consists of a
+return type and a list of formal parameter types. The return type of a function
+type is a void type or first class type --- except for :ref:`label <t_label>`
+and :ref:`metadata <t_metadata>` types.
+
+:Syntax:
+
+::
+
+ <returntype> (<parameter list>)
+
+...where '``<parameter list>``' is a comma-separated list of type
+specifiers. Optionally, the parameter list may include a type ``...``, which
+indicates that the function takes a variable number of arguments. Variable
+argument functions can access their arguments with the :ref:`variable argument
+handling intrinsic <int_varargs>` functions. '``<returntype>``' is any type
+except :ref:`label <t_label>` and :ref:`metadata <t_metadata>`.
+
+:Examples:
+
++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| ``i32 (i32)`` | function taking an ``i32``, returning an ``i32`` |
++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| ``float (i16, i32 *) *`` | :ref:`Pointer <t_pointer>` to a function that takes an ``i16`` and a :ref:`pointer <t_pointer>` to ``i32``, returning ``float``. |
++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| ``i32 (i8*, ...)`` | A vararg function that takes at least one :ref:`pointer <t_pointer>` to ``i8`` (char in C), which returns an integer. This is the signature for ``printf`` in LLVM. |
++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| ``{i32, i32} (i32)`` | A function taking an ``i32``, returning a :ref:`structure <t_struct>` containing two ``i32`` values |
++---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+
+.. _t_firstclass:
+
+First Class Types
+-----------------
+
+The :ref:`first class <t_firstclass>` types are perhaps the most important.
+Values of these types are the only ones which can be produced by
+instructions.
+
+.. _t_single_value:
+
+Single Value Types
+^^^^^^^^^^^^^^^^^^
+
+These are the types that are valid in registers from CodeGen's perspective.
+
+.. _t_integer:
+
+Integer Type
+""""""""""""
+
+:Overview:
+
+The integer type is a very simple type that simply specifies an
+arbitrary bit width for the integer type desired. Any bit width from 1
+bit to 2\ :sup:`23`\ -1 (about 8 million) can be specified.
+
+:Syntax:
+
+::
+
+ iN
+
+The number of bits the integer will occupy is specified by the ``N``
+value.
+
+Examples:
+*********
+
++----------------+------------------------------------------------+
+| ``i1`` | a single-bit integer. |
++----------------+------------------------------------------------+
+| ``i32`` | a 32-bit integer. |
++----------------+------------------------------------------------+
+| ``i1942652`` | a really big integer of over 1 million bits. |
++----------------+------------------------------------------------+
+
+.. _t_floating:
+
+Floating Point Types
+""""""""""""""""""""
+
+.. list-table::
+ :header-rows: 1
+
+ * - Type
+ - Description
+
+ * - ``half``
+ - 16-bit floating point value
+
+ * - ``float``
+ - 32-bit floating point value
+
+ * - ``double``
+ - 64-bit floating point value
+
+ * - ``fp128``
+ - 128-bit floating point value (112-bit mantissa)
+
+ * - ``x86_fp80``
+ - 80-bit floating point value (X87)
+
+ * - ``ppc_fp128``
+ - 128-bit floating point value (two 64-bits)
+
+X86_mmx Type
+""""""""""""
+
+:Overview:
+
+The x86_mmx type represents a value held in an MMX register on an x86
+machine. The operations allowed on it are quite limited: parameters and
+return values, load and store, and bitcast. User-specified MMX
+instructions are represented as intrinsic or asm calls with arguments
+and/or results of this type. There are no arrays, vectors or constants
+of this type.
+
+:Syntax:
+
+::
+
+ x86_mmx
+
+
+.. _t_pointer:
+
+Pointer Type
+""""""""""""
+
+:Overview:
+
+The pointer type is used to specify memory locations. Pointers are
+commonly used to reference objects in memory.
+
+Pointer types may have an optional address space attribute defining the
+numbered address space where the pointed-to object resides. The default
+address space is number zero. The semantics of non-zero address spaces
+are target-specific.
+
+Note that LLVM does not permit pointers to void (``void*``) nor does it
+permit pointers to labels (``label*``). Use ``i8*`` instead.
+
+:Syntax:
+
+::
+
+ <type> *
+
+:Examples:
+
++-------------------------+--------------------------------------------------------------------------------------------------------------+
+| ``[4 x i32]*`` | A :ref:`pointer <t_pointer>` to :ref:`array <t_array>` of four ``i32`` values. |
++-------------------------+--------------------------------------------------------------------------------------------------------------+
+| ``i32 (i32*) *`` | A :ref:`pointer <t_pointer>` to a :ref:`function <t_function>` that takes an ``i32*``, returning an ``i32``. |
++-------------------------+--------------------------------------------------------------------------------------------------------------+
+| ``i32 addrspace(5)*`` | A :ref:`pointer <t_pointer>` to an ``i32`` value that resides in address space #5. |
++-------------------------+--------------------------------------------------------------------------------------------------------------+
+
+.. _t_vector:
+
+Vector Type
+"""""""""""
+
+:Overview:
+
+A vector type is a simple derived type that represents a vector of
+elements. Vector types are used when multiple primitive data are
+operated in parallel using a single instruction (SIMD). A vector type
+requires a size (number of elements) and an underlying primitive data
+type. Vector types are considered :ref:`first class <t_firstclass>`.
+
+:Syntax:
+
+::
+
+ < <# elements> x <elementtype> >
+
+The number of elements is a constant integer value larger than 0;
+elementtype may be any integer, floating point or pointer type. Vectors
+of size zero are not allowed.
+
+:Examples:
+
++-------------------+--------------------------------------------------+
+| ``<4 x i32>`` | Vector of 4 32-bit integer values. |
++-------------------+--------------------------------------------------+
+| ``<8 x float>`` | Vector of 8 32-bit floating-point values. |
++-------------------+--------------------------------------------------+
+| ``<2 x i64>`` | Vector of 2 64-bit integer values. |
++-------------------+--------------------------------------------------+
+| ``<4 x i64*>`` | Vector of 4 pointers to 64-bit integer values. |
++-------------------+--------------------------------------------------+
+
+.. _t_label:
+
+Label Type
+^^^^^^^^^^
+
+:Overview:
+
+The label type represents code labels.
+
+:Syntax:
+
+::
+
+ label
+
+.. _t_metadata:
+
+Metadata Type
+^^^^^^^^^^^^^
+
+:Overview:
+
+The metadata type represents embedded metadata. No derived types may be
+created from metadata except for :ref:`function <t_function>` arguments.
+
+:Syntax:
+
+::
+
+ metadata
+
+.. _t_aggregate:
+
+Aggregate Types
+^^^^^^^^^^^^^^^
+
+Aggregate Types are a subset of derived types that can contain multiple
+member types. :ref:`Arrays <t_array>` and :ref:`structs <t_struct>` are
+aggregate types. :ref:`Vectors <t_vector>` are not considered to be
+aggregate types.
+
+.. _t_array:
+
+Array Type
+""""""""""
+
+:Overview:
+
+The array type is a very simple derived type that arranges elements
+sequentially in memory. The array type requires a size (number of
+elements) and an underlying data type.
+
+:Syntax:
+
+::
+
+ [<# elements> x <elementtype>]
+
+The number of elements is a constant integer value; ``elementtype`` may
+be any type with a size.
+
+:Examples:
+
++------------------+--------------------------------------+
+| ``[40 x i32]`` | Array of 40 32-bit integer values. |
++------------------+--------------------------------------+
+| ``[41 x i32]`` | Array of 41 32-bit integer values. |
++------------------+--------------------------------------+
+| ``[4 x i8]`` | Array of 4 8-bit integer values. |
++------------------+--------------------------------------+
+
+Here are some examples of multidimensional arrays:
+
++-----------------------------+----------------------------------------------------------+
+| ``[3 x [4 x i32]]`` | 3x4 array of 32-bit integer values. |
++-----------------------------+----------------------------------------------------------+
+| ``[12 x [10 x float]]`` | 12x10 array of single precision floating point values. |
++-----------------------------+----------------------------------------------------------+
+| ``[2 x [3 x [4 x i16]]]`` | 2x3x4 array of 16-bit integer values. |
++-----------------------------+----------------------------------------------------------+
+
+There is no restriction on indexing beyond the end of the array implied
+by a static type (though there are restrictions on indexing beyond the
+bounds of an allocated object in some cases). This means that
+single-dimension 'variable sized array' addressing can be implemented in
+LLVM with a zero length array type. An implementation of 'pascal style
+arrays' in LLVM could use the type "``{ i32, [0 x float]}``", for
+example.
+
+.. _t_struct:
+
+Structure Type
+""""""""""""""
+
+:Overview:
+
+The structure type is used to represent a collection of data members
+together in memory. The elements of a structure may be any type that has
+a size.
+
+Structures in memory are accessed using '``load``' and '``store``' by
+getting a pointer to a field with the '``getelementptr``' instruction.
+Structures in registers are accessed using the '``extractvalue``' and
+'``insertvalue``' instructions.
+
+Structures may optionally be "packed" structures, which indicate that
+the alignment of the struct is one byte, and that there is no padding
+between the elements. In non-packed structs, padding between field types
+is inserted as defined by the DataLayout string in the module, which is
+required to match what the underlying code generator expects.
+
+Structures can either be "literal" or "identified". A literal structure
+is defined inline with other types (e.g. ``{i32, i32}*``) whereas
+identified types are always defined at the top level with a name.
+Literal types are uniqued by their contents and can never be recursive
+or opaque since there is no way to write one. Identified types can be
+recursive, can be opaqued, and are never uniqued.
+
+:Syntax:
+
+::
+
+ %T1 = type { <type list> } ; Identified normal struct type
+ %T2 = type <{ <type list> }> ; Identified packed struct type
+
+:Examples:
+
++------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| ``{ i32, i32, i32 }`` | A triple of three ``i32`` values |
++------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| ``{ float, i32 (i32) * }`` | A pair, where the first element is a ``float`` and the second element is a :ref:`pointer <t_pointer>` to a :ref:`function <t_function>` that takes an ``i32``, returning an ``i32``. |
++------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| ``<{ i8, i32 }>`` | A packed struct known to be 5 bytes in size. |
++------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+
+.. _t_opaque:
+
+Opaque Structure Types
+""""""""""""""""""""""
+
+:Overview:
+
+Opaque structure types are used to represent named structure types that
+do not have a body specified. This corresponds (for example) to the C
+notion of a forward declared structure.
+
+:Syntax:
+
+::
+
+ %X = type opaque
+ %52 = type opaque
+
+:Examples:
+
++--------------+-------------------+
+| ``opaque`` | An opaque type. |
++--------------+-------------------+
+
+.. _constants:
+
+Constants
+=========
+
+LLVM has several different basic types of constants. This section
+describes them all and their syntax.
+
+Simple Constants
+----------------
+
+**Boolean constants**
+ The two strings '``true``' and '``false``' are both valid constants
+ of the ``i1`` type.
+**Integer constants**
+ Standard integers (such as '4') are constants of the
+ :ref:`integer <t_integer>` type. Negative numbers may be used with
+ integer types.
+**Floating point constants**
+ Floating point constants use standard decimal notation (e.g.
+ 123.421), exponential notation (e.g. 1.23421e+2), or a more precise
+ hexadecimal notation (see below). The assembler requires the exact
+ decimal value of a floating-point constant. For example, the
+ assembler accepts 1.25 but rejects 1.3 because 1.3 is a repeating
+ decimal in binary. Floating point constants must have a :ref:`floating
+ point <t_floating>` type.
+**Null pointer constants**
+ The identifier '``null``' is recognized as a null pointer constant
+ and must be of :ref:`pointer type <t_pointer>`.
+
+The one non-intuitive notation for constants is the hexadecimal form of
+floating point constants. For example, the form
+'``double 0x432ff973cafa8000``' is equivalent to (but harder to read
+than) '``double 4.5e+15``'. The only time hexadecimal floating point
+constants are required (and the only time that they are generated by the
+disassembler) is when a floating point constant must be emitted but it
+cannot be represented as a decimal floating point number in a reasonable
+number of digits. For example, NaN's, infinities, and other special
+values are represented in their IEEE hexadecimal format so that assembly
+and disassembly do not cause any bits to change in the constants.
+
+When using the hexadecimal form, constants of types half, float, and
+double are represented using the 16-digit form shown above (which
+matches the IEEE754 representation for double); half and float values
+must, however, be exactly representable as IEEE 754 half and single
+precision, respectively. Hexadecimal format is always used for long
+double, and there are three forms of long double. The 80-bit format used
+by x86 is represented as ``0xK`` followed by 20 hexadecimal digits. The
+128-bit format used by PowerPC (two adjacent doubles) is represented by
+``0xM`` followed by 32 hexadecimal digits. The IEEE 128-bit format is
+represented by ``0xL`` followed by 32 hexadecimal digits. Long doubles
+will only work if they match the long double format on your target.
+The IEEE 16-bit format (half precision) is represented by ``0xH``
+followed by 4 hexadecimal digits. All hexadecimal formats are big-endian
+(sign bit at the left).
+
+There are no constants of type x86_mmx.
+
+.. _complexconstants:
+
+Complex Constants
+-----------------
+
+Complex constants are a (potentially recursive) combination of simple
+constants and smaller complex constants.
+
+**Structure constants**
+ Structure constants are represented with notation similar to
+ structure type definitions (a comma separated list of elements,
+ surrounded by braces (``{}``)). For example:
+ "``{ i32 4, float 17.0, i32* @G }``", where "``@G``" is declared as
+ "``@G = external global i32``". Structure constants must have
+ :ref:`structure type <t_struct>`, and the number and types of elements
+ must match those specified by the type.
+**Array constants**
+ Array constants are represented with notation similar to array type
+ definitions (a comma separated list of elements, surrounded by
+ square brackets (``[]``)). For example:
+ "``[ i32 42, i32 11, i32 74 ]``". Array constants must have
+ :ref:`array type <t_array>`, and the number and types of elements must
+ match those specified by the type. As a special case, character array
+ constants may also be represented as a double-quoted string using the ``c``
+ prefix. For example: "``c"Hello World\0A\00"``".
+**Vector constants**
+ Vector constants are represented with notation similar to vector
+ type definitions (a comma separated list of elements, surrounded by
+ less-than/greater-than's (``<>``)). For example:
+ "``< i32 42, i32 11, i32 74, i32 100 >``". Vector constants
+ must have :ref:`vector type <t_vector>`, and the number and types of
+ elements must match those specified by the type.
+**Zero initialization**
+ The string '``zeroinitializer``' can be used to zero initialize a
+ value to zero of *any* type, including scalar and
+ :ref:`aggregate <t_aggregate>` types. This is often used to avoid
+ having to print large zero initializers (e.g. for large arrays) and
+ is always exactly equivalent to using explicit zero initializers.
+**Metadata node**
+ A metadata node is a constant tuple without types. For example:
+ "``!{!0, !{!2, !0}, !"test"}``". Metadata can reference constant values,
+ for example: "``!{!0, i32 0, i8* @global, i64 (i64)* @function, !"str"}``".
+ Unlike other typed constants that are meant to be interpreted as part of
+ the instruction stream, metadata is a place to attach additional
+ information such as debug info.
+
+Global Variable and Function Addresses
+--------------------------------------
+
+The addresses of :ref:`global variables <globalvars>` and
+:ref:`functions <functionstructure>` are always implicitly valid
+(link-time) constants. These constants are explicitly referenced when
+the :ref:`identifier for the global <identifiers>` is used and always have
+:ref:`pointer <t_pointer>` type. For example, the following is a legal LLVM
+file:
+
+.. code-block:: llvm
+
+ @X = global i32 17
+ @Y = global i32 42
+ @Z = global [2 x i32*] [ i32* @X, i32* @Y ]
+
+.. _undefvalues:
+
+Undefined Values
+----------------
+
+The string '``undef``' can be used anywhere a constant is expected, and
+indicates that the user of the value may receive an unspecified
+bit-pattern. Undefined values may be of any type (other than '``label``'
+or '``void``') and be used anywhere a constant is permitted.
+
+Undefined values are useful because they indicate to the compiler that
+the program is well defined no matter what value is used. This gives the
+compiler more freedom to optimize. Here are some examples of
+(potentially surprising) transformations that are valid (in pseudo IR):
+
+.. code-block:: llvm
+
+ %A = add %X, undef
+ %B = sub %X, undef
+ %C = xor %X, undef
+ Safe:
+ %A = undef
+ %B = undef
+ %C = undef
+
+This is safe because all of the output bits are affected by the undef
+bits. Any output bit can have a zero or one depending on the input bits.
+
+.. code-block:: llvm
+
+ %A = or %X, undef
+ %B = and %X, undef
+ Safe:
+ %A = -1
+ %B = 0
+ Unsafe:
+ %A = undef
+ %B = undef
+
+These logical operations have bits that are not always affected by the
+input. For example, if ``%X`` has a zero bit, then the output of the
+'``and``' operation will always be a zero for that bit, no matter what
+the corresponding bit from the '``undef``' is. As such, it is unsafe to
+optimize or assume that the result of the '``and``' is '``undef``'.
+However, it is safe to assume that all bits of the '``undef``' could be
+0, and optimize the '``and``' to 0. Likewise, it is safe to assume that
+all the bits of the '``undef``' operand to the '``or``' could be set,
+allowing the '``or``' to be folded to -1.
+
+.. code-block:: llvm
+
+ %A = select undef, %X, %Y
+ %B = select undef, 42, %Y
+ %C = select %X, %Y, undef
+ Safe:
+ %A = %X (or %Y)
+ %B = 42 (or %Y)
+ %C = %Y
+ Unsafe:
+ %A = undef
+ %B = undef
+ %C = undef
+
+This set of examples shows that undefined '``select``' (and conditional
+branch) conditions can go *either way*, but they have to come from one
+of the two operands. In the ``%A`` example, if ``%X`` and ``%Y`` were
+both known to have a clear low bit, then ``%A`` would have to have a
+cleared low bit. However, in the ``%C`` example, the optimizer is
+allowed to assume that the '``undef``' operand could be the same as
+``%Y``, allowing the whole '``select``' to be eliminated.
+
+.. code-block:: llvm
+
+ %A = xor undef, undef
+
+ %B = undef
+ %C = xor %B, %B
+
+ %D = undef
+ %E = icmp slt %D, 4
+ %F = icmp gte %D, 4
+
+ Safe:
+ %A = undef
+ %B = undef
+ %C = undef
+ %D = undef
+ %E = undef
+ %F = undef
+
+This example points out that two '``undef``' operands are not
+necessarily the same. This can be surprising to people (and also matches
+C semantics) where they assume that "``X^X``" is always zero, even if
+``X`` is undefined. This isn't true for a number of reasons, but the
+short answer is that an '``undef``' "variable" can arbitrarily change
+its value over its "live range". This is true because the variable
+doesn't actually *have a live range*. Instead, the value is logically
+read from arbitrary registers that happen to be around when needed, so
+the value is not necessarily consistent over time. In fact, ``%A`` and
+``%C`` need to have the same semantics or the core LLVM "replace all
+uses with" concept would not hold.
+
+.. code-block:: llvm
+
+ %A = fdiv undef, %X
+ %B = fdiv %X, undef
+ Safe:
+ %A = undef
+ b: unreachable
+
+These examples show the crucial difference between an *undefined value*
+and *undefined behavior*. An undefined value (like '``undef``') is
+allowed to have an arbitrary bit-pattern. This means that the ``%A``
+operation can be constant folded to '``undef``', because the '``undef``'
+could be an SNaN, and ``fdiv`` is not (currently) defined on SNaN's.
+However, in the second example, we can make a more aggressive
+assumption: because the ``undef`` is allowed to be an arbitrary value,
+we are allowed to assume that it could be zero. Since a divide by zero
+has *undefined behavior*, we are allowed to assume that the operation
+does not execute at all. This allows us to delete the divide and all
+code after it. Because the undefined operation "can't happen", the
+optimizer can assume that it occurs in dead code.
+
+.. code-block:: llvm
+
+ a: store undef -> %X
+ b: store %X -> undef
+ Safe:
+ a: <deleted>
+ b: unreachable
+
+These examples reiterate the ``fdiv`` example: a store *of* an undefined
+value can be assumed to not have any effect; we can assume that the
+value is overwritten with bits that happen to match what was already
+there. However, a store *to* an undefined location could clobber
+arbitrary memory, therefore, it has undefined behavior.
+
+.. _poisonvalues:
+
+Poison Values
+-------------
+
+Poison values are similar to :ref:`undef values <undefvalues>`, however
+they also represent the fact that an instruction or constant expression
+that cannot evoke side effects has nevertheless detected a condition
+that results in undefined behavior.
+
+There is currently no way of representing a poison value in the IR; they
+only exist when produced by operations such as :ref:`add <i_add>` with
+the ``nsw`` flag.
+
+Poison value behavior is defined in terms of value *dependence*:
+
+- Values other than :ref:`phi <i_phi>` nodes depend on their operands.
+- :ref:`Phi <i_phi>` nodes depend on the operand corresponding to
+ their dynamic predecessor basic block.
+- Function arguments depend on the corresponding actual argument values
+ in the dynamic callers of their functions.
+- :ref:`Call <i_call>` instructions depend on the :ref:`ret <i_ret>`
+ instructions that dynamically transfer control back to them.
+- :ref:`Invoke <i_invoke>` instructions depend on the
+ :ref:`ret <i_ret>`, :ref:`resume <i_resume>`, or exception-throwing
+ call instructions that dynamically transfer control back to them.
+- Non-volatile loads and stores depend on the most recent stores to all
+ of the referenced memory addresses, following the order in the IR
+ (including loads and stores implied by intrinsics such as
+ :ref:`@llvm.memcpy <int_memcpy>`.)
+- An instruction with externally visible side effects depends on the
+ most recent preceding instruction with externally visible side
+ effects, following the order in the IR. (This includes :ref:`volatile
+ operations <volatile>`.)
+- An instruction *control-depends* on a :ref:`terminator
+ instruction <terminators>` if the terminator instruction has
+ multiple successors and the instruction is always executed when
+ control transfers to one of the successors, and may not be executed
+ when control is transferred to another.
+- Additionally, an instruction also *control-depends* on a terminator
+ instruction if the set of instructions it otherwise depends on would
+ be different if the terminator had transferred control to a different
+ successor.
+- Dependence is transitive.
+
+Poison values have the same behavior as :ref:`undef values <undefvalues>`,
+with the additional effect that any instruction that has a *dependence*
+on a poison value has undefined behavior.
+
+Here are some examples:
+
+.. code-block:: llvm
+
+ entry:
+ %poison = sub nuw i32 0, 1 ; Results in a poison value.
+ %still_poison = and i32 %poison, 0 ; 0, but also poison.
+ %poison_yet_again = getelementptr i32* @h, i32 %still_poison
+ store i32 0, i32* %poison_yet_again ; memory at @h[0] is poisoned
+
+ store i32 %poison, i32* @g ; Poison value stored to memory.
+ %poison2 = load i32* @g ; Poison value loaded back from memory.
+
+ store volatile i32 %poison, i32* @g ; External observation; undefined behavior.
+
+ %narrowaddr = bitcast i32* @g to i16*
+ %wideaddr = bitcast i32* @g to i64*
+ %poison3 = load i16* %narrowaddr ; Returns a poison value.
+ %poison4 = load i64* %wideaddr ; Returns a poison value.
+
+ %cmp = icmp slt i32 %poison, 0 ; Returns a poison value.
+ br i1 %cmp, label %true, label %end ; Branch to either destination.
+
+ true:
+ store volatile i32 0, i32* @g ; This is control-dependent on %cmp, so
+ ; it has undefined behavior.
+ br label %end
+
+ end:
+ %p = phi i32 [ 0, %entry ], [ 1, %true ]
+ ; Both edges into this PHI are
+ ; control-dependent on %cmp, so this
+ ; always results in a poison value.
+
+ store volatile i32 0, i32* @g ; This would depend on the store in %true
+ ; if %cmp is true, or the store in %entry
+ ; otherwise, so this is undefined behavior.
+
+ br i1 %cmp, label %second_true, label %second_end
+ ; The same branch again, but this time the
+ ; true block doesn't have side effects.
+
+ second_true:
+ ; No side effects!
+ ret void
+
+ second_end:
+ store volatile i32 0, i32* @g ; This time, the instruction always depends
+ ; on the store in %end. Also, it is
+ ; control-equivalent to %end, so this is
+ ; well-defined (ignoring earlier undefined
+ ; behavior in this example).
+
+.. _blockaddress:
+
+Addresses of Basic Blocks
+-------------------------
+
+``blockaddress(@function, %block)``
+
+The '``blockaddress``' constant computes the address of the specified
+basic block in the specified function, and always has an ``i8*`` type.
+Taking the address of the entry block is illegal.
+
+This value only has defined behavior when used as an operand to the
+':ref:`indirectbr <i_indirectbr>`' instruction, or for comparisons
+against null. Pointer equality tests between labels addresses results in
+undefined behavior --- though, again, comparison against null is ok, and
+no label is equal to the null pointer. This may be passed around as an
+opaque pointer sized value as long as the bits are not inspected. This
+allows ``ptrtoint`` and arithmetic to be performed on these values so
+long as the original value is reconstituted before the ``indirectbr``
+instruction.
+
+Finally, some targets may provide defined semantics when using the value
+as the operand to an inline assembly, but that is target specific.
+
+.. _constantexprs:
+
+Constant Expressions
+--------------------
+
+Constant expressions are used to allow expressions involving other
+constants to be used as constants. Constant expressions may be of any
+:ref:`first class <t_firstclass>` type and may involve any LLVM operation
+that does not have side effects (e.g. load and call are not supported).
+The following is the syntax for constant expressions:
+
+``trunc (CST to TYPE)``
+ Truncate a constant to another type. The bit size of CST must be
+ larger than the bit size of TYPE. Both types must be integers.
+``zext (CST to TYPE)``
+ Zero extend a constant to another type. The bit size of CST must be
+ smaller than the bit size of TYPE. Both types must be integers.
+``sext (CST to TYPE)``
+ Sign extend a constant to another type. The bit size of CST must be
+ smaller than the bit size of TYPE. Both types must be integers.
+``fptrunc (CST to TYPE)``
+ Truncate a floating point constant to another floating point type.
+ The size of CST must be larger than the size of TYPE. Both types
+ must be floating point.
+``fpext (CST to TYPE)``
+ Floating point extend a constant to another type. The size of CST
+ must be smaller or equal to the size of TYPE. Both types must be
+ floating point.
+``fptoui (CST to TYPE)``
+ Convert a floating point constant to the corresponding unsigned
+ integer constant. TYPE must be a scalar or vector integer type. CST
+ must be of scalar or vector floating point type. Both CST and TYPE
+ must be scalars, or vectors of the same number of elements. If the
+ value won't fit in the integer type, the results are undefined.
+``fptosi (CST to TYPE)``
+ Convert a floating point constant to the corresponding signed
+ integer constant. TYPE must be a scalar or vector integer type. CST
+ must be of scalar or vector floating point type. Both CST and TYPE
+ must be scalars, or vectors of the same number of elements. If the
+ value won't fit in the integer type, the results are undefined.
+``uitofp (CST to TYPE)``
+ Convert an unsigned integer constant to the corresponding floating
+ point constant. TYPE must be a scalar or vector floating point type.
+ CST must be of scalar or vector integer type. Both CST and TYPE must
+ be scalars, or vectors of the same number of elements. If the value
+ won't fit in the floating point type, the results are undefined.
+``sitofp (CST to TYPE)``
+ Convert a signed integer constant to the corresponding floating
+ point constant. TYPE must be a scalar or vector floating point type.
+ CST must be of scalar or vector integer type. Both CST and TYPE must
+ be scalars, or vectors of the same number of elements. If the value
+ won't fit in the floating point type, the results are undefined.
+``ptrtoint (CST to TYPE)``
+ Convert a pointer typed constant to the corresponding integer
+ constant. ``TYPE`` must be an integer type. ``CST`` must be of
+ pointer type. The ``CST`` value is zero extended, truncated, or
+ unchanged to make it fit in ``TYPE``.
+``inttoptr (CST to TYPE)``
+ Convert an integer constant to a pointer constant. TYPE must be a
+ pointer type. CST must be of integer type. The CST value is zero
+ extended, truncated, or unchanged to make it fit in a pointer size.
+ This one is *really* dangerous!
+``bitcast (CST to TYPE)``
+ Convert a constant, CST, to another TYPE. The constraints of the
+ operands are the same as those for the :ref:`bitcast
+ instruction <i_bitcast>`.
+``addrspacecast (CST to TYPE)``
+ Convert a constant pointer or constant vector of pointer, CST, to another
+ TYPE in a different address space. The constraints of the operands are the
+ same as those for the :ref:`addrspacecast instruction <i_addrspacecast>`.
+``getelementptr (CSTPTR, IDX0, IDX1, ...)``, ``getelementptr inbounds (CSTPTR, IDX0, IDX1, ...)``
+ Perform the :ref:`getelementptr operation <i_getelementptr>` on
+ constants. As with the :ref:`getelementptr <i_getelementptr>`
+ instruction, the index list may have zero or more indexes, which are
+ required to make sense for the type of "CSTPTR".
+``select (COND, VAL1, VAL2)``
+ Perform the :ref:`select operation <i_select>` on constants.
+``icmp COND (VAL1, VAL2)``
+ Performs the :ref:`icmp operation <i_icmp>` on constants.
+``fcmp COND (VAL1, VAL2)``
+ Performs the :ref:`fcmp operation <i_fcmp>` on constants.
+``extractelement (VAL, IDX)``
+ Perform the :ref:`extractelement operation <i_extractelement>` on
+ constants.
+``insertelement (VAL, ELT, IDX)``
+ Perform the :ref:`insertelement operation <i_insertelement>` on
+ constants.
+``shufflevector (VEC1, VEC2, IDXMASK)``
+ Perform the :ref:`shufflevector operation <i_shufflevector>` on
+ constants.
+``extractvalue (VAL, IDX0, IDX1, ...)``
+ Perform the :ref:`extractvalue operation <i_extractvalue>` on
+ constants. The index list is interpreted in a similar manner as
+ indices in a ':ref:`getelementptr <i_getelementptr>`' operation. At
+ least one index value must be specified.
+``insertvalue (VAL, ELT, IDX0, IDX1, ...)``
+ Perform the :ref:`insertvalue operation <i_insertvalue>` on constants.
+ The index list is interpreted in a similar manner as indices in a
+ ':ref:`getelementptr <i_getelementptr>`' operation. At least one index
+ value must be specified.
+``OPCODE (LHS, RHS)``
+ Perform the specified operation of the LHS and RHS constants. OPCODE
+ may be any of the :ref:`binary <binaryops>` or :ref:`bitwise
+ binary <bitwiseops>` operations. The constraints on operands are
+ the same as those for the corresponding instruction (e.g. no bitwise
+ operations on floating point values are allowed).
+
+Other Values
+============
+
+.. _inlineasmexprs:
+
+Inline Assembler Expressions
+----------------------------
+
+LLVM supports inline assembler expressions (as opposed to :ref:`Module-Level
+Inline Assembly <moduleasm>`) through the use of a special value. This
+value represents the inline assembler as a string (containing the
+instructions to emit), a list of operand constraints (stored as a
+string), a flag that indicates whether or not the inline asm expression
+has side effects, and a flag indicating whether the function containing
+the asm needs to align its stack conservatively. An example inline
+assembler expression is:
+
+.. code-block:: llvm
+
+ i32 (i32) asm "bswap $0", "=r,r"
+
+Inline assembler expressions may **only** be used as the callee operand
+of a :ref:`call <i_call>` or an :ref:`invoke <i_invoke>` instruction.
+Thus, typically we have:
+
+.. code-block:: llvm
+
+ %X = call i32 asm "bswap $0", "=r,r"(i32 %Y)
+
+Inline asms with side effects not visible in the constraint list must be
+marked as having side effects. This is done through the use of the
+'``sideeffect``' keyword, like so:
+
+.. code-block:: llvm
+
+ call void asm sideeffect "eieio", ""()
+
+In some cases inline asms will contain code that will not work unless
+the stack is aligned in some way, such as calls or SSE instructions on
+x86, yet will not contain code that does that alignment within the asm.
+The compiler should make conservative assumptions about what the asm
+might contain and should generate its usual stack alignment code in the
+prologue if the '``alignstack``' keyword is present:
+
+.. code-block:: llvm
+
+ call void asm alignstack "eieio", ""()
+
+Inline asms also support using non-standard assembly dialects. The
+assumed dialect is ATT. When the '``inteldialect``' keyword is present,
+the inline asm is using the Intel dialect. Currently, ATT and Intel are
+the only supported dialects. An example is:
+
+.. code-block:: llvm
+
+ call void asm inteldialect "eieio", ""()
+
+If multiple keywords appear the '``sideeffect``' keyword must come
+first, the '``alignstack``' keyword second and the '``inteldialect``'
+keyword last.
+
+Inline Asm Metadata
+^^^^^^^^^^^^^^^^^^^
+
+The call instructions that wrap inline asm nodes may have a
+"``!srcloc``" MDNode attached to it that contains a list of constant
+integers. If present, the code generator will use the integer as the
+location cookie value when report errors through the ``LLVMContext``
+error reporting mechanisms. This allows a front-end to correlate backend
+errors that occur with inline asm back to the source code that produced
+it. For example:
+
+.. code-block:: llvm
+
+ call void asm sideeffect "something bad", ""(), !srcloc !42
+ ...
+ !42 = !{ i32 1234567 }
+
+It is up to the front-end to make sense of the magic numbers it places
+in the IR. If the MDNode contains multiple constants, the code generator
+will use the one that corresponds to the line of the asm that the error
+occurs on.
+
+.. _metadata:
+
+Metadata
+========
+
+LLVM IR allows metadata to be attached to instructions in the program
+that can convey extra information about the code to the optimizers and
+code generator. One example application of metadata is source-level
+debug information. There are two metadata primitives: strings and nodes.
+
+Metadata does not have a type, and is not a value. If referenced from a
+``call`` instruction, it uses the ``metadata`` type.
+
+All metadata are identified in syntax by a exclamation point ('``!``').
+
+Metadata Nodes and Metadata Strings
+-----------------------------------
+
+A metadata string is a string surrounded by double quotes. It can
+contain any character by escaping non-printable characters with
+"``\xx``" where "``xx``" is the two digit hex code. For example:
+"``!"test\00"``".
+
+Metadata nodes are represented with notation similar to structure
+constants (a comma separated list of elements, surrounded by braces and
+preceded by an exclamation point). Metadata nodes can have any values as
+their operand. For example:
+
+.. code-block:: llvm
+
+ !{ !"test\00", i32 10}
+
+Metadata nodes that aren't uniqued use the ``distinct`` keyword. For example:
+
+.. code-block:: llvm
+
+ !0 = distinct !{!"test\00", i32 10}
+
+``distinct`` nodes are useful when nodes shouldn't be merged based on their
+content. They can also occur when transformations cause uniquing collisions
+when metadata operands change.
+
+A :ref:`named metadata <namedmetadatastructure>` is a collection of
+metadata nodes, which can be looked up in the module symbol table. For
+example:
+
+.. code-block:: llvm
+
+ !foo = !{!4, !3}
+
+Metadata can be used as function arguments. Here ``llvm.dbg.value``
+function is using two metadata arguments:
+
+.. code-block:: llvm
+
+ call void @llvm.dbg.value(metadata !24, i64 0, metadata !25)
+
+Metadata can be attached with an instruction. Here metadata ``!21`` is
+attached to the ``add`` instruction using the ``!dbg`` identifier:
+
+.. code-block:: llvm
+
+ %indvar.next = add i64 %indvar, 1, !dbg !21
+
+More information about specific metadata nodes recognized by the
+optimizers and code generator is found below.
+
+Specialized Metadata Nodes
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Specialized metadata nodes are custom data structures in metadata (as opposed
+to generic tuples). Their fields are labelled, and can be specified in any
+order.
+
+MDLocation
+""""""""""
+
+``MDLocation`` nodes represent source debug locations. The ``scope:`` field is
+mandatory.
+
+.. code-block:: llvm
+
+ !0 = !MDLocation(line: 2900, column: 42, scope: !1, inlinedAt: !2)
+
+'``tbaa``' Metadata
+^^^^^^^^^^^^^^^^^^^
+
+In LLVM IR, memory does not have types, so LLVM's own type system is not
+suitable for doing TBAA. Instead, metadata is added to the IR to
+describe a type system of a higher level language. This can be used to
+implement typical C/C++ TBAA, but it can also be used to implement
+custom alias analysis behavior for other languages.
+
+The current metadata format is very simple. TBAA metadata nodes have up
+to three fields, e.g.:
+
+.. code-block:: llvm
+
+ !0 = !{ !"an example type tree" }
+ !1 = !{ !"int", !0 }
+ !2 = !{ !"float", !0 }
+ !3 = !{ !"const float", !2, i64 1 }
+
+The first field is an identity field. It can be any value, usually a
+metadata string, which uniquely identifies the type. The most important
+name in the tree is the name of the root node. Two trees with different
+root node names are entirely disjoint, even if they have leaves with
+common names.
+
+The second field identifies the type's parent node in the tree, or is
+null or omitted for a root node. A type is considered to alias all of
+its descendants and all of its ancestors in the tree. Also, a type is
+considered to alias all types in other trees, so that bitcode produced
+from multiple front-ends is handled conservatively.
+
+If the third field is present, it's an integer which if equal to 1
+indicates that the type is "constant" (meaning
+``pointsToConstantMemory`` should return true; see `other useful
+AliasAnalysis methods <AliasAnalysis.html#OtherItfs>`_).
+
+'``tbaa.struct``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The :ref:`llvm.memcpy <int_memcpy>` is often used to implement
+aggregate assignment operations in C and similar languages, however it
+is defined to copy a contiguous region of memory, which is more than
+strictly necessary for aggregate types which contain holes due to
+padding. Also, it doesn't contain any TBAA information about the fields
+of the aggregate.
+
+``!tbaa.struct`` metadata can describe which memory subregions in a
+memcpy are padding and what the TBAA tags of the struct are.
+
+The current metadata format is very simple. ``!tbaa.struct`` metadata
+nodes are a list of operands which are in conceptual groups of three.
+For each group of three, the first operand gives the byte offset of a
+field in bytes, the second gives its size in bytes, and the third gives
+its tbaa tag. e.g.:
+
+.. code-block:: llvm
+
+ !4 = !{ i64 0, i64 4, !1, i64 8, i64 4, !2 }
+
+This describes a struct with two fields. The first is at offset 0 bytes
+with size 4 bytes, and has tbaa tag !1. The second is at offset 8 bytes
+and has size 4 bytes and has tbaa tag !2.
+
+Note that the fields need not be contiguous. In this example, there is a
+4 byte gap between the two fields. This gap represents padding which
+does not carry useful data and need not be preserved.
+
+'``noalias``' and '``alias.scope``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+``noalias`` and ``alias.scope`` metadata provide the ability to specify generic
+noalias memory-access sets. This means that some collection of memory access
+instructions (loads, stores, memory-accessing calls, etc.) that carry
+``noalias`` metadata can specifically be specified not to alias with some other
+collection of memory access instructions that carry ``alias.scope`` metadata.
+Each type of metadata specifies a list of scopes where each scope has an id and
+a domain. When evaluating an aliasing query, if for some some domain, the set
+of scopes with that domain in one instruction's ``alias.scope`` list is a
+subset of (or qual to) the set of scopes for that domain in another
+instruction's ``noalias`` list, then the two memory accesses are assumed not to
+alias.
+
+The metadata identifying each domain is itself a list containing one or two
+entries. The first entry is the name of the domain. Note that if the name is a
+string then it can be combined accross functions and translation units. A
+self-reference can be used to create globally unique domain names. A
+descriptive string may optionally be provided as a second list entry.
+
+The metadata identifying each scope is also itself a list containing two or
+three entries. The first entry is the name of the scope. Note that if the name
+is a string then it can be combined accross functions and translation units. A
+self-reference can be used to create globally unique scope names. A metadata
+reference to the scope's domain is the second entry. A descriptive string may
+optionally be provided as a third list entry.
+
+For example,
+
+.. code-block:: llvm
+
+ ; Two scope domains:
+ !0 = !{!0}
+ !1 = !{!1}
+
+ ; Some scopes in these domains:
+ !2 = !{!2, !0}
+ !3 = !{!3, !0}
+ !4 = !{!4, !1}
+
+ ; Some scope lists:
+ !5 = !{!4} ; A list containing only scope !4
+ !6 = !{!4, !3, !2}
+ !7 = !{!3}
+
+ ; These two instructions don't alias:
+ %0 = load float* %c, align 4, !alias.scope !5
+ store float %0, float* %arrayidx.i, align 4, !noalias !5
+
+ ; These two instructions also don't alias (for domain !1, the set of scopes
+ ; in the !alias.scope equals that in the !noalias list):
+ %2 = load float* %c, align 4, !alias.scope !5
+ store float %2, float* %arrayidx.i2, align 4, !noalias !6
+
+ ; These two instructions don't alias (for domain !0, the set of scopes in
+ ; the !noalias list is not a superset of, or equal to, the scopes in the
+ ; !alias.scope list):
+ %2 = load float* %c, align 4, !alias.scope !6
+ store float %0, float* %arrayidx.i, align 4, !noalias !7
+
+'``fpmath``' Metadata
+^^^^^^^^^^^^^^^^^^^^^
+
+``fpmath`` metadata may be attached to any instruction of floating point
+type. It can be used to express the maximum acceptable error in the
+result of that instruction, in ULPs, thus potentially allowing the
+compiler to use a more efficient but less accurate method of computing
+it. ULP is defined as follows:
+
+ If ``x`` is a real number that lies between two finite consecutive
+ floating-point numbers ``a`` and ``b``, without being equal to one
+ of them, then ``ulp(x) = |b - a|``, otherwise ``ulp(x)`` is the
+ distance between the two non-equal finite floating-point numbers
+ nearest ``x``. Moreover, ``ulp(NaN)`` is ``NaN``.
+
+The metadata node shall consist of a single positive floating point
+number representing the maximum relative error, for example:
+
+.. code-block:: llvm
+
+ !0 = !{ float 2.5 } ; maximum acceptable inaccuracy is 2.5 ULPs
+
+'``range``' Metadata
+^^^^^^^^^^^^^^^^^^^^
+
+``range`` metadata may be attached only to ``load``, ``call`` and ``invoke`` of
+integer types. It expresses the possible ranges the loaded value or the value
+returned by the called function at this call site is in. The ranges are
+represented with a flattened list of integers. The loaded value or the value
+returned is known to be in the union of the ranges defined by each consecutive
+pair. Each pair has the following properties:
+
+- The type must match the type loaded by the instruction.
+- The pair ``a,b`` represents the range ``[a,b)``.
+- Both ``a`` and ``b`` are constants.
+- The range is allowed to wrap.
+- The range should not represent the full or empty set. That is,
+ ``a!=b``.
+
+In addition, the pairs must be in signed order of the lower bound and
+they must be non-contiguous.
+
+Examples:
+
+.. code-block:: llvm
+
+ %a = load i8* %x, align 1, !range !0 ; Can only be 0 or 1
+ %b = load i8* %y, align 1, !range !1 ; Can only be 255 (-1), 0 or 1
+ %c = call i8 @foo(), !range !2 ; Can only be 0, 1, 3, 4 or 5
+ %d = invoke i8 @bar() to label %cont
+ unwind label %lpad, !range !3 ; Can only be -2, -1, 3, 4 or 5
+ ...
+ !0 = !{ i8 0, i8 2 }
+ !1 = !{ i8 255, i8 2 }
+ !2 = !{ i8 0, i8 2, i8 3, i8 6 }
+ !3 = !{ i8 -2, i8 0, i8 3, i8 6 }
+
+'``llvm.loop``'
+^^^^^^^^^^^^^^^
+
+It is sometimes useful to attach information to loop constructs. Currently,
+loop metadata is implemented as metadata attached to the branch instruction
+in the loop latch block. This type of metadata refer to a metadata node that is
+guaranteed to be separate for each loop. The loop identifier metadata is
+specified with the name ``llvm.loop``.
+
+The loop identifier metadata is implemented using a metadata that refers to
+itself to avoid merging it with any other identifier metadata, e.g.,
+during module linkage or function inlining. That is, each loop should refer
+to their own identification metadata even if they reside in separate functions.
+The following example contains loop identifier metadata for two separate loop
+constructs:
+
+.. code-block:: llvm
+
+ !0 = !{!0}
+ !1 = !{!1}
+
+The loop identifier metadata can be used to specify additional
+per-loop metadata. Any operands after the first operand can be treated
+as user-defined metadata. For example the ``llvm.loop.unroll.count``
+suggests an unroll factor to the loop unroller:
+
+.. code-block:: llvm
+
+ br i1 %exitcond, label %._crit_edge, label %.lr.ph, !llvm.loop !0
+ ...
+ !0 = !{!0, !1}
+ !1 = !{!"llvm.loop.unroll.count", i32 4}
+
+'``llvm.loop.vectorize``' and '``llvm.loop.interleave``'
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Metadata prefixed with ``llvm.loop.vectorize`` or ``llvm.loop.interleave`` are
+used to control per-loop vectorization and interleaving parameters such as
+vectorization width and interleave count. These metadata should be used in
+conjunction with ``llvm.loop`` loop identification metadata. The
+``llvm.loop.vectorize`` and ``llvm.loop.interleave`` metadata are only
+optimization hints and the optimizer will only interleave and vectorize loops if
+it believes it is safe to do so. The ``llvm.mem.parallel_loop_access`` metadata
+which contains information about loop-carried memory dependencies can be helpful
+in determining the safety of these transformations.
+
+'``llvm.loop.interleave.count``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata suggests an interleave count to the loop interleaver.
+The first operand is the string ``llvm.loop.interleave.count`` and the
+second operand is an integer specifying the interleave count. For
+example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.interleave.count", i32 4}
+
+Note that setting ``llvm.loop.interleave.count`` to 1 disables interleaving
+multiple iterations of the loop. If ``llvm.loop.interleave.count`` is set to 0
+then the interleave count will be determined automatically.
+
+'``llvm.loop.vectorize.enable``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata selectively enables or disables vectorization for the loop. The
+first operand is the string ``llvm.loop.vectorize.enable`` and the second operand
+is a bit. If the bit operand value is 1 vectorization is enabled. A value of
+0 disables vectorization:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.vectorize.enable", i1 0}
+ !1 = !{!"llvm.loop.vectorize.enable", i1 1}
+
+'``llvm.loop.vectorize.width``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata sets the target width of the vectorizer. The first
+operand is the string ``llvm.loop.vectorize.width`` and the second
+operand is an integer specifying the width. For example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.vectorize.width", i32 4}
+
+Note that setting ``llvm.loop.vectorize.width`` to 1 disables
+vectorization of the loop. If ``llvm.loop.vectorize.width`` is set to
+0 or if the loop does not have this metadata the width will be
+determined automatically.
+
+'``llvm.loop.unroll``'
+^^^^^^^^^^^^^^^^^^^^^^
+
+Metadata prefixed with ``llvm.loop.unroll`` are loop unrolling
+optimization hints such as the unroll factor. ``llvm.loop.unroll``
+metadata should be used in conjunction with ``llvm.loop`` loop
+identification metadata. The ``llvm.loop.unroll`` metadata are only
+optimization hints and the unrolling will only be performed if the
+optimizer believes it is safe to do so.
+
+'``llvm.loop.unroll.count``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata suggests an unroll factor to the loop unroller. The
+first operand is the string ``llvm.loop.unroll.count`` and the second
+operand is a positive integer specifying the unroll factor. For
+example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.unroll.count", i32 4}
+
+If the trip count of the loop is less than the unroll count the loop
+will be partially unrolled.
+
+'``llvm.loop.unroll.disable``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata either disables loop unrolling. The metadata has a single operand
+which is the string ``llvm.loop.unroll.disable``. For example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.unroll.disable"}
+
+'``llvm.loop.unroll.full``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata either suggests that the loop should be unrolled fully. The
+metadata has a single operand which is the string ``llvm.loop.unroll.disable``.
+For example:
+
+.. code-block:: llvm
+
+ !0 = !{!"llvm.loop.unroll.full"}
+
+'``llvm.mem``'
+^^^^^^^^^^^^^^^
+
+Metadata types used to annotate memory accesses with information helpful
+for optimizations are prefixed with ``llvm.mem``.
+
+'``llvm.mem.parallel_loop_access``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``llvm.mem.parallel_loop_access`` metadata refers to a loop identifier,
+or metadata containing a list of loop identifiers for nested loops.
+The metadata is attached to memory accessing instructions and denotes that
+no loop carried memory dependence exist between it and other instructions denoted
+with the same loop identifier.
+
+Precisely, given two instructions ``m1`` and ``m2`` that both have the
+``llvm.mem.parallel_loop_access`` metadata, with ``L1`` and ``L2`` being the
+set of loops associated with that metadata, respectively, then there is no loop
+carried dependence between ``m1`` and ``m2`` for loops in both ``L1`` and
+``L2``.
+
+As a special case, if all memory accessing instructions in a loop have
+``llvm.mem.parallel_loop_access`` metadata that refers to that loop, then the
+loop has no loop carried memory dependences and is considered to be a parallel
+loop.
+
+Note that if not all memory access instructions have such metadata referring to
+the loop, then the loop is considered not being trivially parallel. Additional
+memory dependence analysis is required to make that determination. As a fail
+safe mechanism, this causes loops that were originally parallel to be considered
+sequential (if optimization passes that are unaware of the parallel semantics
+insert new memory instructions into the loop body).
+
+Example of a loop that is considered parallel due to its correct use of
+both ``llvm.loop`` and ``llvm.mem.parallel_loop_access``
+metadata types that refer to the same loop identifier metadata.
+
+.. code-block:: llvm
+
+ for.body:
+ ...
+ %val0 = load i32* %arrayidx, !llvm.mem.parallel_loop_access !0
+ ...
+ store i32 %val0, i32* %arrayidx1, !llvm.mem.parallel_loop_access !0
+ ...
+ br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !0
+
+ for.end:
+ ...
+ !0 = !{!0}
+
+It is also possible to have nested parallel loops. In that case the
+memory accesses refer to a list of loop identifier metadata nodes instead of
+the loop identifier metadata node directly:
+
+.. code-block:: llvm
+
+ outer.for.body:
+ ...
+ %val1 = load i32* %arrayidx3, !llvm.mem.parallel_loop_access !2
+ ...
+ br label %inner.for.body
+
+ inner.for.body:
+ ...
+ %val0 = load i32* %arrayidx1, !llvm.mem.parallel_loop_access !0
+ ...
+ store i32 %val0, i32* %arrayidx2, !llvm.mem.parallel_loop_access !0
+ ...
+ br i1 %exitcond, label %inner.for.end, label %inner.for.body, !llvm.loop !1
+
+ inner.for.end:
+ ...
+ store i32 %val1, i32* %arrayidx4, !llvm.mem.parallel_loop_access !2
+ ...
+ br i1 %exitcond, label %outer.for.end, label %outer.for.body, !llvm.loop !2
+
+ outer.for.end: ; preds = %for.body
+ ...
+ !0 = !{!1, !2} ; a list of loop identifiers
+ !1 = !{!1} ; an identifier for the inner loop
+ !2 = !{!2} ; an identifier for the outer loop
+
+Module Flags Metadata
+=====================
+
+Information about the module as a whole is difficult to convey to LLVM's
+subsystems. The LLVM IR isn't sufficient to transmit this information.
+The ``llvm.module.flags`` named metadata exists in order to facilitate
+this. These flags are in the form of key / value pairs --- much like a
+dictionary --- making it easy for any subsystem who cares about a flag to
+look it up.
+
+The ``llvm.module.flags`` metadata contains a list of metadata triplets.
+Each triplet has the following form:
+
+- The first element is a *behavior* flag, which specifies the behavior
+ when two (or more) modules are merged together, and it encounters two
+ (or more) metadata with the same ID. The supported behaviors are
+ described below.
+- The second element is a metadata string that is a unique ID for the
+ metadata. Each module may only have one flag entry for each unique ID (not
+ including entries with the **Require** behavior).
+- The third element is the value of the flag.
+
+When two (or more) modules are merged together, the resulting
+``llvm.module.flags`` metadata is the union of the modules' flags. That is, for
+each unique metadata ID string, there will be exactly one entry in the merged
+modules ``llvm.module.flags`` metadata table, and the value for that entry will
+be determined by the merge behavior flag, as described below. The only exception
+is that entries with the *Require* behavior are always preserved.
+
+The following behaviors are supported:
+
+.. list-table::
+ :header-rows: 1
+ :widths: 10 90
+
+ * - Value
+ - Behavior
+
+ * - 1
+ - **Error**
+ Emits an error if two values disagree, otherwise the resulting value
+ is that of the operands.
+
+ * - 2
+ - **Warning**
+ Emits a warning if two values disagree. The result value will be the
+ operand for the flag from the first module being linked.
+
+ * - 3
+ - **Require**
+ Adds a requirement that another module flag be present and have a
+ specified value after linking is performed. The value must be a
+ metadata pair, where the first element of the pair is the ID of the
+ module flag to be restricted, and the second element of the pair is
+ the value the module flag should be restricted to. This behavior can
+ be used to restrict the allowable results (via triggering of an
+ error) of linking IDs with the **Override** behavior.
+
+ * - 4
+ - **Override**
+ Uses the specified value, regardless of the behavior or value of the
+ other module. If both modules specify **Override**, but the values
+ differ, an error will be emitted.
+
+ * - 5
+ - **Append**
+ Appends the two values, which are required to be metadata nodes.
+
+ * - 6
+ - **AppendUnique**
+ Appends the two values, which are required to be metadata
+ nodes. However, duplicate entries in the second list are dropped
+ during the append operation.
+
+It is an error for a particular unique flag ID to have multiple behaviors,
+except in the case of **Require** (which adds restrictions on another metadata
+value) or **Override**.
+
+An example of module flags:
+
+.. code-block:: llvm
+
+ !0 = !{ i32 1, !"foo", i32 1 }
+ !1 = !{ i32 4, !"bar", i32 37 }
+ !2 = !{ i32 2, !"qux", i32 42 }
+ !3 = !{ i32 3, !"qux",
+ !{
+ !"foo", i32 1
+ }
+ }
+ !llvm.module.flags = !{ !0, !1, !2, !3 }
+
+- Metadata ``!0`` has the ID ``!"foo"`` and the value '1'. The behavior
+ if two or more ``!"foo"`` flags are seen is to emit an error if their
+ values are not equal.
+
+- Metadata ``!1`` has the ID ``!"bar"`` and the value '37'. The
+ behavior if two or more ``!"bar"`` flags are seen is to use the value
+ '37'.
+
+- Metadata ``!2`` has the ID ``!"qux"`` and the value '42'. The
+ behavior if two or more ``!"qux"`` flags are seen is to emit a
+ warning if their values are not equal.
+
+- Metadata ``!3`` has the ID ``!"qux"`` and the value:
+
+ ::
+
+ !{ !"foo", i32 1 }
+
+ The behavior is to emit an error if the ``llvm.module.flags`` does not
+ contain a flag with the ID ``!"foo"`` that has the value '1' after linking is
+ performed.
+
+Objective-C Garbage Collection Module Flags Metadata
+----------------------------------------------------
+
+On the Mach-O platform, Objective-C stores metadata about garbage
+collection in a special section called "image info". The metadata
+consists of a version number and a bitmask specifying what types of
+garbage collection are supported (if any) by the file. If two or more
+modules are linked together their garbage collection metadata needs to
+be merged rather than appended together.
+
+The Objective-C garbage collection module flags metadata consists of the
+following key-value pairs:
+
+.. list-table::
+ :header-rows: 1
+ :widths: 30 70
+
+ * - Key
+ - Value
+
+ * - ``Objective-C Version``
+ - **[Required]** --- The Objective-C ABI version. Valid values are 1 and 2.
+
+ * - ``Objective-C Image Info Version``
+ - **[Required]** --- The version of the image info section. Currently
+ always 0.
+
+ * - ``Objective-C Image Info Section``
+ - **[Required]** --- The section to place the metadata. Valid values are
+ ``"__OBJC, __image_info, regular"`` for Objective-C ABI version 1, and
+ ``"__DATA,__objc_imageinfo, regular, no_dead_strip"`` for
+ Objective-C ABI version 2.
+
+ * - ``Objective-C Garbage Collection``
+ - **[Required]** --- Specifies whether garbage collection is supported or
+ not. Valid values are 0, for no garbage collection, and 2, for garbage
+ collection supported.
+
+ * - ``Objective-C GC Only``
+ - **[Optional]** --- Specifies that only garbage collection is supported.
+ If present, its value must be 6. This flag requires that the
+ ``Objective-C Garbage Collection`` flag have the value 2.
+
+Some important flag interactions:
+
+- If a module with ``Objective-C Garbage Collection`` set to 0 is
+ merged with a module with ``Objective-C Garbage Collection`` set to
+ 2, then the resulting module has the
+ ``Objective-C Garbage Collection`` flag set to 0.
+- A module with ``Objective-C Garbage Collection`` set to 0 cannot be
+ merged with a module with ``Objective-C GC Only`` set to 6.
+
+Automatic Linker Flags Module Flags Metadata
+--------------------------------------------
+
+Some targets support embedding flags to the linker inside individual object
+files. Typically this is used in conjunction with language extensions which
+allow source files to explicitly declare the libraries they depend on, and have
+these automatically be transmitted to the linker via object files.
+
+These flags are encoded in the IR using metadata in the module flags section,
+using the ``Linker Options`` key. The merge behavior for this flag is required
+to be ``AppendUnique``, and the value for the key is expected to be a metadata
+node which should be a list of other metadata nodes, each of which should be a
+list of metadata strings defining linker options.
+
+For example, the following metadata section specifies two separate sets of
+linker options, presumably to link against ``libz`` and the ``Cocoa``
+framework::
+
+ !0 = !{ i32 6, !"Linker Options",
+ !{
+ !{ !"-lz" },
+ !{ !"-framework", !"Cocoa" } } }
+ !llvm.module.flags = !{ !0 }
+
+The metadata encoding as lists of lists of options, as opposed to a collapsed
+list of options, is chosen so that the IR encoding can use multiple option
+strings to specify e.g., a single library, while still having that specifier be
+preserved as an atomic element that can be recognized by a target specific
+assembly writer or object file emitter.
+
+Each individual option is required to be either a valid option for the target's
+linker, or an option that is reserved by the target specific assembly writer or
+object file emitter. No other aspect of these options is defined by the IR.
+
+C type width Module Flags Metadata
+----------------------------------
+
+The ARM backend emits a section into each generated object file describing the
+options that it was compiled with (in a compiler-independent way) to prevent
+linking incompatible objects, and to allow automatic library selection. Some
+of these options are not visible at the IR level, namely wchar_t width and enum
+width.
+
+To pass this information to the backend, these options are encoded in module
+flags metadata, using the following key-value pairs:
+
+.. list-table::
+ :header-rows: 1
+ :widths: 30 70
+
+ * - Key
+ - Value
+
+ * - short_wchar
+ - * 0 --- sizeof(wchar_t) == 4
+ * 1 --- sizeof(wchar_t) == 2
+
+ * - short_enum
+ - * 0 --- Enums are at least as large as an ``int``.
+ * 1 --- Enums are stored in the smallest integer type which can
+ represent all of its values.
+
+For example, the following metadata section specifies that the module was
+compiled with a ``wchar_t`` width of 4 bytes, and the underlying type of an
+enum is the smallest type which can represent all of its values::
+
+ !llvm.module.flags = !{!0, !1}
+ !0 = !{i32 1, !"short_wchar", i32 1}
+ !1 = !{i32 1, !"short_enum", i32 0}
+
+.. _intrinsicglobalvariables:
+
+Intrinsic Global Variables
+==========================
+
+LLVM has a number of "magic" global variables that contain data that
+affect code generation or other IR semantics. These are documented here.
+All globals of this sort should have a section specified as
+"``llvm.metadata``". This section and all globals that start with
+"``llvm.``" are reserved for use by LLVM.
+
+.. _gv_llvmused:
+
+The '``llvm.used``' Global Variable
+-----------------------------------
+
+The ``@llvm.used`` global is an array which has
+:ref:`appending linkage <linkage_appending>`. This array contains a list of
+pointers to named global variables, functions and aliases which may optionally
+have a pointer cast formed of bitcast or getelementptr. For example, a legal
+use of it is:
+
+.. code-block:: llvm
+
+ @X = global i8 4
+ @Y = global i32 123
+
+ @llvm.used = appending global [2 x i8*] [
+ i8* @X,
+ i8* bitcast (i32* @Y to i8*)
+ ], section "llvm.metadata"
+
+If a symbol appears in the ``@llvm.used`` list, then the compiler, assembler,
+and linker are required to treat the symbol as if there is a reference to the
+symbol that it cannot see (which is why they have to be named). For example, if
+a variable has internal linkage and no references other than that from the
+``@llvm.used`` list, it cannot be deleted. This is commonly used to represent
+references from inline asms and other things the compiler cannot "see", and
+corresponds to "``attribute((used))``" in GNU C.
+
+On some targets, the code generator must emit a directive to the
+assembler or object file to prevent the assembler and linker from
+molesting the symbol.
+
+.. _gv_llvmcompilerused:
+
+The '``llvm.compiler.used``' Global Variable
+--------------------------------------------
+
+The ``@llvm.compiler.used`` directive is the same as the ``@llvm.used``
+directive, except that it only prevents the compiler from touching the
+symbol. On targets that support it, this allows an intelligent linker to
+optimize references to the symbol without being impeded as it would be
+by ``@llvm.used``.
+
+This is a rare construct that should only be used in rare circumstances,
+and should not be exposed to source languages.
+
+.. _gv_llvmglobalctors:
+
+The '``llvm.global_ctors``' Global Variable
+-------------------------------------------
+
+.. code-block:: llvm
+
+ %0 = type { i32, void ()*, i8* }
+ @llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @ctor, i8* @data }]
+
+The ``@llvm.global_ctors`` array contains a list of constructor
+functions, priorities, and an optional associated global or function.
+The functions referenced by this array will be called in ascending order
+of priority (i.e. lowest first) when the module is loaded. The order of
+functions with the same priority is not defined.
+
+If the third field is present, non-null, and points to a global variable
+or function, the initializer function will only run if the associated
+data from the current module is not discarded.
+
+.. _llvmglobaldtors:
+
+The '``llvm.global_dtors``' Global Variable
+-------------------------------------------
+
+.. code-block:: llvm
+
+ %0 = type { i32, void ()*, i8* }
+ @llvm.global_dtors = appending global [1 x %0] [%0 { i32 65535, void ()* @dtor, i8* @data }]
+
+The ``@llvm.global_dtors`` array contains a list of destructor
+functions, priorities, and an optional associated global or function.
+The functions referenced by this array will be called in descending
+order of priority (i.e. highest first) when the module is unloaded. The
+order of functions with the same priority is not defined.
+
+If the third field is present, non-null, and points to a global variable
+or function, the destructor function will only run if the associated
+data from the current module is not discarded.
+
+Instruction Reference
+=====================
+
+The LLVM instruction set consists of several different classifications
+of instructions: :ref:`terminator instructions <terminators>`, :ref:`binary
+instructions <binaryops>`, :ref:`bitwise binary
+instructions <bitwiseops>`, :ref:`memory instructions <memoryops>`, and
+:ref:`other instructions <otherops>`.
+
+.. _terminators:
+
+Terminator Instructions
+-----------------------
+
+As mentioned :ref:`previously <functionstructure>`, every basic block in a
+program ends with a "Terminator" instruction, which indicates which
+block should be executed after the current block is finished. These
+terminator instructions typically yield a '``void``' value: they produce
+control flow, not values (the one exception being the
+':ref:`invoke <i_invoke>`' instruction).
+
+The terminator instructions are: ':ref:`ret <i_ret>`',
+':ref:`br <i_br>`', ':ref:`switch <i_switch>`',
+':ref:`indirectbr <i_indirectbr>`', ':ref:`invoke <i_invoke>`',
+':ref:`resume <i_resume>`', and ':ref:`unreachable <i_unreachable>`'.
+
+.. _i_ret:
+
+'``ret``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ ret <type> <value> ; Return a value from a non-void function
+ ret void ; Return from void function
+
+Overview:
+"""""""""
+
+The '``ret``' instruction is used to return control flow (and optionally
+a value) from a function back to the caller.
+
+There are two forms of the '``ret``' instruction: one that returns a
+value and then causes control flow, and one that just causes control
+flow to occur.
+
+Arguments:
+""""""""""
+
+The '``ret``' instruction optionally accepts a single argument, the
+return value. The type of the return value must be a ':ref:`first
+class <t_firstclass>`' type.
+
+A function is not :ref:`well formed <wellformed>` if it it has a non-void
+return type and contains a '``ret``' instruction with no return value or
+a return value with a type that does not match its type, or if it has a
+void return type and contains a '``ret``' instruction with a return
+value.
+
+Semantics:
+""""""""""
+
+When the '``ret``' instruction is executed, control flow returns back to
+the calling function's context. If the caller is a
+":ref:`call <i_call>`" instruction, execution continues at the
+instruction after the call. If the caller was an
+":ref:`invoke <i_invoke>`" instruction, execution continues at the
+beginning of the "normal" destination block. If the instruction returns
+a value, that value shall set the call or invoke instruction's return
+value.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ ret i32 5 ; Return an integer value of 5
+ ret void ; Return from a void function
+ ret { i32, i8 } { i32 4, i8 2 } ; Return a struct of values 4 and 2
+
+.. _i_br:
+
+'``br``' Instruction
+^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ br i1 <cond>, label <iftrue>, label <iffalse>
+ br label <dest> ; Unconditional branch
+
+Overview:
+"""""""""
+
+The '``br``' instruction is used to cause control flow to transfer to a
+different basic block in the current function. There are two forms of
+this instruction, corresponding to a conditional branch and an
+unconditional branch.
+
+Arguments:
+""""""""""
+
+The conditional branch form of the '``br``' instruction takes a single
+'``i1``' value and two '``label``' values. The unconditional form of the
+'``br``' instruction takes a single '``label``' value as a target.
+
+Semantics:
+""""""""""
+
+Upon execution of a conditional '``br``' instruction, the '``i1``'
+argument is evaluated. If the value is ``true``, control flows to the
+'``iftrue``' ``label`` argument. If "cond" is ``false``, control flows
+to the '``iffalse``' ``label`` argument.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ Test:
+ %cond = icmp eq i32 %a, %b
+ br i1 %cond, label %IfEqual, label %IfUnequal
+ IfEqual:
+ ret i32 1
+ IfUnequal:
+ ret i32 0
+
+.. _i_switch:
+
+'``switch``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ]
+
+Overview:
+"""""""""
+
+The '``switch``' instruction is used to transfer control flow to one of
+several different places. It is a generalization of the '``br``'
+instruction, allowing a branch to occur to one of many possible
+destinations.
+
+Arguments:
+""""""""""
+
+The '``switch``' instruction uses three parameters: an integer
+comparison value '``value``', a default '``label``' destination, and an
+array of pairs of comparison value constants and '``label``'s. The table
+is not allowed to contain duplicate constant entries.
+
+Semantics:
+""""""""""
+
+The ``switch`` instruction specifies a table of values and destinations.
+When the '``switch``' instruction is executed, this table is searched
+for the given value. If the value is found, control flow is transferred
+to the corresponding destination; otherwise, control flow is transferred
+to the default destination.
+
+Implementation:
+"""""""""""""""
+
+Depending on properties of the target machine and the particular
+``switch`` instruction, this instruction may be code generated in
+different ways. For example, it could be generated as a series of
+chained conditional branches or with a lookup table.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ ; Emulate a conditional br instruction
+ %Val = zext i1 %value to i32
+ switch i32 %Val, label %truedest [ i32 0, label %falsedest ]
+
+ ; Emulate an unconditional br instruction
+ switch i32 0, label %dest [ ]
+
+ ; Implement a jump table:
+ switch i32 %val, label %otherwise [ i32 0, label %onzero
+ i32 1, label %onone
+ i32 2, label %ontwo ]
+
+.. _i_indirectbr:
+
+'``indirectbr``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ indirectbr <somety>* <address>, [ label <dest1>, label <dest2>, ... ]
+
+Overview:
+"""""""""
+
+The '``indirectbr``' instruction implements an indirect branch to a
+label within the current function, whose address is specified by
+"``address``". Address must be derived from a
+:ref:`blockaddress <blockaddress>` constant.
+
+Arguments:
+""""""""""
+
+The '``address``' argument is the address of the label to jump to. The
+rest of the arguments indicate the full set of possible destinations
+that the address may point to. Blocks are allowed to occur multiple
+times in the destination list, though this isn't particularly useful.
+
+This destination list is required so that dataflow analysis has an
+accurate understanding of the CFG.
+
+Semantics:
+""""""""""
+
+Control transfers to the block specified in the address argument. All
+possible destination blocks must be listed in the label list, otherwise
+this instruction has undefined behavior. This implies that jumps to
+labels defined in other functions have undefined behavior as well.
+
+Implementation:
+"""""""""""""""
+
+This is typically implemented with a jump through a register.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ indirectbr i8* %Addr, [ label %bb1, label %bb2, label %bb3 ]
+
+.. _i_invoke:
+
+'``invoke``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = invoke [cconv] [ret attrs] <ptr to function ty> <function ptr val>(<function args>) [fn attrs]
+ to label <normal label> unwind label <exception label>
+
+Overview:
+"""""""""
+
+The '``invoke``' instruction causes control to transfer to a specified
+function, with the possibility of control flow transfer to either the
+'``normal``' label or the '``exception``' label. If the callee function
+returns with the "``ret``" instruction, control flow will return to the
+"normal" label. If the callee (or any indirect callees) returns via the
+":ref:`resume <i_resume>`" instruction or other exception handling
+mechanism, control is interrupted and continued at the dynamically
+nearest "exception" label.
+
+The '``exception``' label is a `landing
+pad <ExceptionHandling.html#overview>`_ for the exception. As such,
+'``exception``' label is required to have the
+":ref:`landingpad <i_landingpad>`" instruction, which contains the
+information about the behavior of the program after unwinding happens,
+as its first non-PHI instruction. The restrictions on the
+"``landingpad``" instruction's tightly couples it to the "``invoke``"
+instruction, so that the important information contained within the
+"``landingpad``" instruction can't be lost through normal code motion.
+
+Arguments:
+""""""""""
+
+This instruction requires several arguments:
+
+#. The optional "cconv" marker indicates which :ref:`calling
+ convention <callingconv>` the call should use. If none is
+ specified, the call defaults to using C calling conventions.
+#. The optional :ref:`Parameter Attributes <paramattrs>` list for return
+ values. Only '``zeroext``', '``signext``', and '``inreg``' attributes
+ are valid here.
+#. '``ptr to function ty``': shall be the signature of the pointer to
+ function value being invoked. In most cases, this is a direct
+ function invocation, but indirect ``invoke``'s are just as possible,
+ branching off an arbitrary pointer to function value.
+#. '``function ptr val``': An LLVM value containing a pointer to a
+ function to be invoked.
+#. '``function args``': argument list whose types match the function
+ signature argument types and parameter attributes. All arguments must
+ be of :ref:`first class <t_firstclass>` type. If the function signature
+ indicates the function accepts a variable number of arguments, the
+ extra arguments can be specified.
+#. '``normal label``': the label reached when the called function
+ executes a '``ret``' instruction.
+#. '``exception label``': the label reached when a callee returns via
+ the :ref:`resume <i_resume>` instruction or other exception handling
+ mechanism.
+#. The optional :ref:`function attributes <fnattrs>` list. Only
+ '``noreturn``', '``nounwind``', '``readonly``' and '``readnone``'
+ attributes are valid here.
+
+Semantics:
+""""""""""
+
+This instruction is designed to operate as a standard '``call``'
+instruction in most regards. The primary difference is that it
+establishes an association with a label, which is used by the runtime
+library to unwind the stack.
+
+This instruction is used in languages with destructors to ensure that
+proper cleanup is performed in the case of either a ``longjmp`` or a
+thrown exception. Additionally, this is important for implementation of
+'``catch``' clauses in high-level languages that support them.
+
+For the purposes of the SSA form, the definition of the value returned
+by the '``invoke``' instruction is deemed to occur on the edge from the
+current block to the "normal" label. If the callee unwinds then no
+return value is available.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %retval = invoke i32 @Test(i32 15) to label %Continue
+ unwind label %TestCleanup ; i32:retval set
+ %retval = invoke coldcc i32 %Testfnptr(i32 15) to label %Continue
+ unwind label %TestCleanup ; i32:retval set
+
+.. _i_resume:
+
+'``resume``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ resume <type> <value>
+
+Overview:
+"""""""""
+
+The '``resume``' instruction is a terminator instruction that has no
+successors.
+
+Arguments:
+""""""""""
+
+The '``resume``' instruction requires one argument, which must have the
+same type as the result of any '``landingpad``' instruction in the same
+function.
+
+Semantics:
+""""""""""
+
+The '``resume``' instruction resumes propagation of an existing
+(in-flight) exception whose unwinding was interrupted with a
+:ref:`landingpad <i_landingpad>` instruction.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ resume { i8*, i32 } %exn
+
+.. _i_unreachable:
+
+'``unreachable``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ unreachable
+
+Overview:
+"""""""""
+
+The '``unreachable``' instruction has no defined semantics. This
+instruction is used to inform the optimizer that a particular portion of
+the code is not reachable. This can be used to indicate that the code
+after a no-return function cannot be reached, and other facts.
+
+Semantics:
+""""""""""
+
+The '``unreachable``' instruction has no defined semantics.
+
+.. _binaryops:
+
+Binary Operations
+-----------------
+
+Binary operators are used to do most of the computation in a program.
+They require two operands of the same type, execute an operation on
+them, and produce a single value. The operands might represent multiple
+data, as is the case with the :ref:`vector <t_vector>` data type. The
+result value has the same type as its operands.
+
+There are several different binary operators:
+
+.. _i_add:
+
+'``add``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = add <ty> <op1>, <op2> ; yields ty:result
+ <result> = add nuw <ty> <op1>, <op2> ; yields ty:result
+ <result> = add nsw <ty> <op1>, <op2> ; yields ty:result
+ <result> = add nuw nsw <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``add``' instruction returns the sum of its two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``add``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the integer sum of the two operands.
+
+If the sum has unsigned overflow, the result returned is the
+mathematical result modulo 2\ :sup:`n`\ , where n is the bit width of
+the result.
+
+Because LLVM integers use a two's complement representation, this
+instruction is appropriate for both signed and unsigned integers.
+
+``nuw`` and ``nsw`` stand for "No Unsigned Wrap" and "No Signed Wrap",
+respectively. If the ``nuw`` and/or ``nsw`` keywords are present, the
+result value of the ``add`` is a :ref:`poison value <poisonvalues>` if
+unsigned and/or signed overflow, respectively, occurs.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = add i32 4, %var ; yields i32:result = 4 + %var
+
+.. _i_fadd:
+
+'``fadd``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fadd [fast-math flags]* <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``fadd``' instruction returns the sum of its two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``fadd``' instruction must be :ref:`floating
+point <t_floating>` or :ref:`vector <t_vector>` of floating point values.
+Both arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the floating point sum of the two operands. This
+instruction can also take any number of :ref:`fast-math flags <fastmath>`,
+which are optimization hints to enable otherwise unsafe floating point
+optimizations:
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = fadd float 4.0, %var ; yields float:result = 4.0 + %var
+
+'``sub``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = sub <ty> <op1>, <op2> ; yields ty:result
+ <result> = sub nuw <ty> <op1>, <op2> ; yields ty:result
+ <result> = sub nsw <ty> <op1>, <op2> ; yields ty:result
+ <result> = sub nuw nsw <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``sub``' instruction returns the difference of its two operands.
+
+Note that the '``sub``' instruction is used to represent the '``neg``'
+instruction present in most other intermediate representations.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``sub``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the integer difference of the two operands.
+
+If the difference has unsigned overflow, the result returned is the
+mathematical result modulo 2\ :sup:`n`\ , where n is the bit width of
+the result.
+
+Because LLVM integers use a two's complement representation, this
+instruction is appropriate for both signed and unsigned integers.
+
+``nuw`` and ``nsw`` stand for "No Unsigned Wrap" and "No Signed Wrap",
+respectively. If the ``nuw`` and/or ``nsw`` keywords are present, the
+result value of the ``sub`` is a :ref:`poison value <poisonvalues>` if
+unsigned and/or signed overflow, respectively, occurs.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = sub i32 4, %var ; yields i32:result = 4 - %var
+ <result> = sub i32 0, %val ; yields i32:result = -%var
+
+.. _i_fsub:
+
+'``fsub``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fsub [fast-math flags]* <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``fsub``' instruction returns the difference of its two operands.
+
+Note that the '``fsub``' instruction is used to represent the '``fneg``'
+instruction present in most other intermediate representations.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``fsub``' instruction must be :ref:`floating
+point <t_floating>` or :ref:`vector <t_vector>` of floating point values.
+Both arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the floating point difference of the two operands.
+This instruction can also take any number of :ref:`fast-math
+flags <fastmath>`, which are optimization hints to enable otherwise
+unsafe floating point optimizations:
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = fsub float 4.0, %var ; yields float:result = 4.0 - %var
+ <result> = fsub float -0.0, %val ; yields float:result = -%var
+
+'``mul``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = mul <ty> <op1>, <op2> ; yields ty:result
+ <result> = mul nuw <ty> <op1>, <op2> ; yields ty:result
+ <result> = mul nsw <ty> <op1>, <op2> ; yields ty:result
+ <result> = mul nuw nsw <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``mul``' instruction returns the product of its two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``mul``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the integer product of the two operands.
+
+If the result of the multiplication has unsigned overflow, the result
+returned is the mathematical result modulo 2\ :sup:`n`\ , where n is the
+bit width of the result.
+
+Because LLVM integers use a two's complement representation, and the
+result is the same width as the operands, this instruction returns the
+correct result for both signed and unsigned integers. If a full product
+(e.g. ``i32`` * ``i32`` -> ``i64``) is needed, the operands should be
+sign-extended or zero-extended as appropriate to the width of the full
+product.
+
+``nuw`` and ``nsw`` stand for "No Unsigned Wrap" and "No Signed Wrap",
+respectively. If the ``nuw`` and/or ``nsw`` keywords are present, the
+result value of the ``mul`` is a :ref:`poison value <poisonvalues>` if
+unsigned and/or signed overflow, respectively, occurs.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = mul i32 4, %var ; yields i32:result = 4 * %var
+
+.. _i_fmul:
+
+'``fmul``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fmul [fast-math flags]* <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``fmul``' instruction returns the product of its two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``fmul``' instruction must be :ref:`floating
+point <t_floating>` or :ref:`vector <t_vector>` of floating point values.
+Both arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the floating point product of the two operands.
+This instruction can also take any number of :ref:`fast-math
+flags <fastmath>`, which are optimization hints to enable otherwise
+unsafe floating point optimizations:
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = fmul float 4.0, %var ; yields float:result = 4.0 * %var
+
+'``udiv``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = udiv <ty> <op1>, <op2> ; yields ty:result
+ <result> = udiv exact <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``udiv``' instruction returns the quotient of its two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``udiv``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the unsigned integer quotient of the two operands.
+
+Note that unsigned integer division and signed integer division are
+distinct operations; for signed integer division, use '``sdiv``'.
+
+Division by zero leads to undefined behavior.
+
+If the ``exact`` keyword is present, the result value of the ``udiv`` is
+a :ref:`poison value <poisonvalues>` if %op1 is not a multiple of %op2 (as
+such, "((a udiv exact b) mul b) == a").
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = udiv i32 4, %var ; yields i32:result = 4 / %var
+
+'``sdiv``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = sdiv <ty> <op1>, <op2> ; yields ty:result
+ <result> = sdiv exact <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``sdiv``' instruction returns the quotient of its two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``sdiv``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the signed integer quotient of the two operands
+rounded towards zero.
+
+Note that signed integer division and unsigned integer division are
+distinct operations; for unsigned integer division, use '``udiv``'.
+
+Division by zero leads to undefined behavior. Overflow also leads to
+undefined behavior; this is a rare case, but can occur, for example, by
+doing a 32-bit division of -2147483648 by -1.
+
+If the ``exact`` keyword is present, the result value of the ``sdiv`` is
+a :ref:`poison value <poisonvalues>` if the result would be rounded.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = sdiv i32 4, %var ; yields i32:result = 4 / %var
+
+.. _i_fdiv:
+
+'``fdiv``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fdiv [fast-math flags]* <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``fdiv``' instruction returns the quotient of its two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``fdiv``' instruction must be :ref:`floating
+point <t_floating>` or :ref:`vector <t_vector>` of floating point values.
+Both arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The value produced is the floating point quotient of the two operands.
+This instruction can also take any number of :ref:`fast-math
+flags <fastmath>`, which are optimization hints to enable otherwise
+unsafe floating point optimizations:
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = fdiv float 4.0, %var ; yields float:result = 4.0 / %var
+
+'``urem``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = urem <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``urem``' instruction returns the remainder from the unsigned
+division of its two arguments.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``urem``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+This instruction returns the unsigned integer *remainder* of a division.
+This instruction always performs an unsigned division to get the
+remainder.
+
+Note that unsigned integer remainder and signed integer remainder are
+distinct operations; for signed integer remainder, use '``srem``'.
+
+Taking the remainder of a division by zero leads to undefined behavior.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = urem i32 4, %var ; yields i32:result = 4 % %var
+
+'``srem``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = srem <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``srem``' instruction returns the remainder from the signed
+division of its two operands. This instruction can also take
+:ref:`vector <t_vector>` versions of the values in which case the elements
+must be integers.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``srem``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+This instruction returns the *remainder* of a division (where the result
+is either zero or has the same sign as the dividend, ``op1``), not the
+*modulo* operator (where the result is either zero or has the same sign
+as the divisor, ``op2``) of a value. For more information about the
+difference, see `The Math
+Forum <http://mathforum.org/dr.math/problems/anne.4.28.99.html>`_. For a
+table of how this is implemented in various languages, please see
+`Wikipedia: modulo
+operation <http://en.wikipedia.org/wiki/Modulo_operation>`_.
+
+Note that signed integer remainder and unsigned integer remainder are
+distinct operations; for unsigned integer remainder, use '``urem``'.
+
+Taking the remainder of a division by zero leads to undefined behavior.
+Overflow also leads to undefined behavior; this is a rare case, but can
+occur, for example, by taking the remainder of a 32-bit division of
+-2147483648 by -1. (The remainder doesn't actually overflow, but this
+rule lets srem be implemented using instructions that return both the
+result of the division and the remainder.)
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = srem i32 4, %var ; yields i32:result = 4 % %var
+
+.. _i_frem:
+
+'``frem``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = frem [fast-math flags]* <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``frem``' instruction returns the remainder from the division of
+its two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``frem``' instruction must be :ref:`floating
+point <t_floating>` or :ref:`vector <t_vector>` of floating point values.
+Both arguments must have identical types.
+
+Semantics:
+""""""""""
+
+This instruction returns the *remainder* of a division. The remainder
+has the same sign as the dividend. This instruction can also take any
+number of :ref:`fast-math flags <fastmath>`, which are optimization hints
+to enable otherwise unsafe floating point optimizations:
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = frem float 4.0, %var ; yields float:result = 4.0 % %var
+
+.. _bitwiseops:
+
+Bitwise Binary Operations
+-------------------------
+
+Bitwise binary operators are used to do various forms of bit-twiddling
+in a program. They are generally very efficient instructions and can
+commonly be strength reduced from other instructions. They require two
+operands of the same type, execute an operation on them, and produce a
+single value. The resulting value is the same type as its operands.
+
+'``shl``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = shl <ty> <op1>, <op2> ; yields ty:result
+ <result> = shl nuw <ty> <op1>, <op2> ; yields ty:result
+ <result> = shl nsw <ty> <op1>, <op2> ; yields ty:result
+ <result> = shl nuw nsw <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``shl``' instruction returns the first operand shifted to the left
+a specified number of bits.
+
+Arguments:
+""""""""""
+
+Both arguments to the '``shl``' instruction must be the same
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer type.
+'``op2``' is treated as an unsigned value.
+
+Semantics:
+""""""""""
+
+The value produced is ``op1`` \* 2\ :sup:`op2` mod 2\ :sup:`n`,
+where ``n`` is the width of the result. If ``op2`` is (statically or
+dynamically) negative or equal to or larger than the number of bits in
+``op1``, the result is undefined. If the arguments are vectors, each
+vector element of ``op1`` is shifted by the corresponding shift amount
+in ``op2``.
+
+If the ``nuw`` keyword is present, then the shift produces a :ref:`poison
+value <poisonvalues>` if it shifts out any non-zero bits. If the
+``nsw`` keyword is present, then the shift produces a :ref:`poison
+value <poisonvalues>` if it shifts out any bits that disagree with the
+resultant sign bit. As such, NUW/NSW have the same semantics as they
+would if the shift were expressed as a mul instruction with the same
+nsw/nuw bits in (mul %op1, (shl 1, %op2)).
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = shl i32 4, %var ; yields i32: 4 << %var
+ <result> = shl i32 4, 2 ; yields i32: 16
+ <result> = shl i32 1, 10 ; yields i32: 1024
+ <result> = shl i32 1, 32 ; undefined
+ <result> = shl <2 x i32> < i32 1, i32 1>, < i32 1, i32 2> ; yields: result=<2 x i32> < i32 2, i32 4>
+
+'``lshr``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = lshr <ty> <op1>, <op2> ; yields ty:result
+ <result> = lshr exact <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``lshr``' instruction (logical shift right) returns the first
+operand shifted to the right a specified number of bits with zero fill.
+
+Arguments:
+""""""""""
+
+Both arguments to the '``lshr``' instruction must be the same
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer type.
+'``op2``' is treated as an unsigned value.
+
+Semantics:
+""""""""""
+
+This instruction always performs a logical shift right operation. The
+most significant bits of the result will be filled with zero bits after
+the shift. If ``op2`` is (statically or dynamically) equal to or larger
+than the number of bits in ``op1``, the result is undefined. If the
+arguments are vectors, each vector element of ``op1`` is shifted by the
+corresponding shift amount in ``op2``.
+
+If the ``exact`` keyword is present, the result value of the ``lshr`` is
+a :ref:`poison value <poisonvalues>` if any of the bits shifted out are
+non-zero.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = lshr i32 4, 1 ; yields i32:result = 2
+ <result> = lshr i32 4, 2 ; yields i32:result = 1
+ <result> = lshr i8 4, 3 ; yields i8:result = 0
+ <result> = lshr i8 -2, 1 ; yields i8:result = 0x7F
+ <result> = lshr i32 1, 32 ; undefined
+ <result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> ; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1>
+
+'``ashr``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = ashr <ty> <op1>, <op2> ; yields ty:result
+ <result> = ashr exact <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``ashr``' instruction (arithmetic shift right) returns the first
+operand shifted to the right a specified number of bits with sign
+extension.
+
+Arguments:
+""""""""""
+
+Both arguments to the '``ashr``' instruction must be the same
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer type.
+'``op2``' is treated as an unsigned value.
+
+Semantics:
+""""""""""
+
+This instruction always performs an arithmetic shift right operation,
+The most significant bits of the result will be filled with the sign bit
+of ``op1``. If ``op2`` is (statically or dynamically) equal to or larger
+than the number of bits in ``op1``, the result is undefined. If the
+arguments are vectors, each vector element of ``op1`` is shifted by the
+corresponding shift amount in ``op2``.
+
+If the ``exact`` keyword is present, the result value of the ``ashr`` is
+a :ref:`poison value <poisonvalues>` if any of the bits shifted out are
+non-zero.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = ashr i32 4, 1 ; yields i32:result = 2
+ <result> = ashr i32 4, 2 ; yields i32:result = 1
+ <result> = ashr i8 4, 3 ; yields i8:result = 0
+ <result> = ashr i8 -2, 1 ; yields i8:result = -1
+ <result> = ashr i32 1, 32 ; undefined
+ <result> = ashr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 3> ; yields: result=<2 x i32> < i32 -1, i32 0>
+
+'``and``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = and <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``and``' instruction returns the bitwise logical and of its two
+operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``and``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The truth table used for the '``and``' instruction is:
+
++-----+-----+-----+
+| In0 | In1 | Out |
++-----+-----+-----+
+| 0 | 0 | 0 |
++-----+-----+-----+
+| 0 | 1 | 0 |
++-----+-----+-----+
+| 1 | 0 | 0 |
++-----+-----+-----+
+| 1 | 1 | 1 |
++-----+-----+-----+
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = and i32 4, %var ; yields i32:result = 4 & %var
+ <result> = and i32 15, 40 ; yields i32:result = 8
+ <result> = and i32 4, 8 ; yields i32:result = 0
+
+'``or``' Instruction
+^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = or <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``or``' instruction returns the bitwise logical inclusive or of its
+two operands.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``or``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The truth table used for the '``or``' instruction is:
+
++-----+-----+-----+
+| In0 | In1 | Out |
++-----+-----+-----+
+| 0 | 0 | 0 |
++-----+-----+-----+
+| 0 | 1 | 1 |
++-----+-----+-----+
+| 1 | 0 | 1 |
++-----+-----+-----+
+| 1 | 1 | 1 |
++-----+-----+-----+
+
+Example:
+""""""""
+
+::
+
+ <result> = or i32 4, %var ; yields i32:result = 4 | %var
+ <result> = or i32 15, 40 ; yields i32:result = 47
+ <result> = or i32 4, 8 ; yields i32:result = 12
+
+'``xor``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = xor <ty> <op1>, <op2> ; yields ty:result
+
+Overview:
+"""""""""
+
+The '``xor``' instruction returns the bitwise logical exclusive or of
+its two operands. The ``xor`` is used to implement the "one's
+complement" operation, which is the "~" operator in C.
+
+Arguments:
+""""""""""
+
+The two arguments to the '``xor``' instruction must be
+:ref:`integer <t_integer>` or :ref:`vector <t_vector>` of integer values. Both
+arguments must have identical types.
+
+Semantics:
+""""""""""
+
+The truth table used for the '``xor``' instruction is:
+
++-----+-----+-----+
+| In0 | In1 | Out |
++-----+-----+-----+
+| 0 | 0 | 0 |
++-----+-----+-----+
+| 0 | 1 | 1 |
++-----+-----+-----+
+| 1 | 0 | 1 |
++-----+-----+-----+
+| 1 | 1 | 0 |
++-----+-----+-----+
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = xor i32 4, %var ; yields i32:result = 4 ^ %var
+ <result> = xor i32 15, 40 ; yields i32:result = 39
+ <result> = xor i32 4, 8 ; yields i32:result = 12
+ <result> = xor i32 %V, -1 ; yields i32:result = ~%V
+
+Vector Operations
+-----------------
+
+LLVM supports several instructions to represent vector operations in a
+target-independent manner. These instructions cover the element-access
+and vector-specific operations needed to process vectors effectively.
+While LLVM does directly support these vector operations, many
+sophisticated algorithms will want to use target-specific intrinsics to
+take full advantage of a specific target.
+
+.. _i_extractelement:
+
+'``extractelement``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = extractelement <n x <ty>> <val>, <ty2> <idx> ; yields <ty>
+
+Overview:
+"""""""""
+
+The '``extractelement``' instruction extracts a single scalar element
+from a vector at a specified index.
+
+Arguments:
+""""""""""
+
+The first operand of an '``extractelement``' instruction is a value of
+:ref:`vector <t_vector>` type. The second operand is an index indicating
+the position from which to extract the element. The index may be a
+variable of any integer type.
+
+Semantics:
+""""""""""
+
+The result is a scalar of the same type as the element type of ``val``.
+Its value is the value at position ``idx`` of ``val``. If ``idx``
+exceeds the length of ``val``, the results are undefined.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = extractelement <4 x i32> %vec, i32 0 ; yields i32
+
+.. _i_insertelement:
+
+'``insertelement``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = insertelement <n x <ty>> <val>, <ty> <elt>, <ty2> <idx> ; yields <n x <ty>>
+
+Overview:
+"""""""""
+
+The '``insertelement``' instruction inserts a scalar element into a
+vector at a specified index.
+
+Arguments:
+""""""""""
+
+The first operand of an '``insertelement``' instruction is a value of
+:ref:`vector <t_vector>` type. The second operand is a scalar value whose
+type must equal the element type of the first operand. The third operand
+is an index indicating the position at which to insert the value. The
+index may be a variable of any integer type.
+
+Semantics:
+""""""""""
+
+The result is a vector of the same type as ``val``. Its element values
+are those of ``val`` except at position ``idx``, where it gets the value
+``elt``. If ``idx`` exceeds the length of ``val``, the results are
+undefined.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = insertelement <4 x i32> %vec, i32 1, i32 0 ; yields <4 x i32>
+
+.. _i_shufflevector:
+
+'``shufflevector``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <m x i32> <mask> ; yields <m x <ty>>
+
+Overview:
+"""""""""
+
+The '``shufflevector``' instruction constructs a permutation of elements
+from two input vectors, returning a vector with the same element type as
+the input and length that is the same as the shuffle mask.
+
+Arguments:
+""""""""""
+
+The first two operands of a '``shufflevector``' instruction are vectors
+with the same type. The third argument is a shuffle mask whose element
+type is always 'i32'. The result of the instruction is a vector whose
+length is the same as the shuffle mask and whose element type is the
+same as the element type of the first two operands.
+
+The shuffle mask operand is required to be a constant vector with either
+constant integer or undef values.
+
+Semantics:
+""""""""""
+
+The elements of the two input vectors are numbered from left to right
+across both of the vectors. The shuffle mask operand specifies, for each
+element of the result vector, which element of the two input vectors the
+result element gets. The element selector may be undef (meaning "don't
+care") and the second operand may be undef if performing a shuffle from
+only one vector.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
+ <4 x i32> <i32 0, i32 4, i32 1, i32 5> ; yields <4 x i32>
+ <result> = shufflevector <4 x i32> %v1, <4 x i32> undef,
+ <4 x i32> <i32 0, i32 1, i32 2, i32 3> ; yields <4 x i32> - Identity shuffle.
+ <result> = shufflevector <8 x i32> %v1, <8 x i32> undef,
+ <4 x i32> <i32 0, i32 1, i32 2, i32 3> ; yields <4 x i32>
+ <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2,
+ <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7 > ; yields <8 x i32>
+
+Aggregate Operations
+--------------------
+
+LLVM supports several instructions for working with
+:ref:`aggregate <t_aggregate>` values.
+
+.. _i_extractvalue:
+
+'``extractvalue``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = extractvalue <aggregate type> <val>, <idx>{, <idx>}*
+
+Overview:
+"""""""""
+
+The '``extractvalue``' instruction extracts the value of a member field
+from an :ref:`aggregate <t_aggregate>` value.
+
+Arguments:
+""""""""""
+
+The first operand of an '``extractvalue``' instruction is a value of
+:ref:`struct <t_struct>` or :ref:`array <t_array>` type. The operands are
+constant indices to specify which value to extract in a similar manner
+as indices in a '``getelementptr``' instruction.
+
+The major differences to ``getelementptr`` indexing are:
+
+- Since the value being indexed is not a pointer, the first index is
+ omitted and assumed to be zero.
+- At least one index must be specified.
+- Not only struct indices but also array indices must be in bounds.
+
+Semantics:
+""""""""""
+
+The result is the value at the position in the aggregate specified by
+the index operands.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = extractvalue {i32, float} %agg, 0 ; yields i32
+
+.. _i_insertvalue:
+
+'``insertvalue``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = insertvalue <aggregate type> <val>, <ty> <elt>, <idx>{, <idx>}* ; yields <aggregate type>
+
+Overview:
+"""""""""
+
+The '``insertvalue``' instruction inserts a value into a member field in
+an :ref:`aggregate <t_aggregate>` value.
+
+Arguments:
+""""""""""
+
+The first operand of an '``insertvalue``' instruction is a value of
+:ref:`struct <t_struct>` or :ref:`array <t_array>` type. The second operand is
+a first-class value to insert. The following operands are constant
+indices indicating the position at which to insert the value in a
+similar manner as indices in a '``extractvalue``' instruction. The value
+to insert must have the same type as the value identified by the
+indices.
+
+Semantics:
+""""""""""
+
+The result is an aggregate of the same type as ``val``. Its value is
+that of ``val`` except that the value at the position specified by the
+indices is that of ``elt``.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %agg1 = insertvalue {i32, float} undef, i32 1, 0 ; yields {i32 1, float undef}
+ %agg2 = insertvalue {i32, float} %agg1, float %val, 1 ; yields {i32 1, float %val}
+ %agg3 = insertvalue {i32, {float}} undef, float %val, 1, 0 ; yields {i32 undef, {float %val}}
+
+.. _memoryops:
+
+Memory Access and Addressing Operations
+---------------------------------------
+
+A key design point of an SSA-based representation is how it represents
+memory. In LLVM, no memory locations are in SSA form, which makes things
+very simple. This section describes how to read, write, and allocate
+memory in LLVM.
+
+.. _i_alloca:
+
+'``alloca``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = alloca [inalloca] <type> [, <ty> <NumElements>] [, align <alignment>] ; yields type*:result
+
+Overview:
+"""""""""
+
+The '``alloca``' instruction allocates memory on the stack frame of the
+currently executing function, to be automatically released when this
+function returns to its caller. The object is always allocated in the
+generic address space (address space zero).
+
+Arguments:
+""""""""""
+
+The '``alloca``' instruction allocates ``sizeof(<type>)*NumElements``
+bytes of memory on the runtime stack, returning a pointer of the
+appropriate type to the program. If "NumElements" is specified, it is
+the number of elements allocated, otherwise "NumElements" is defaulted
+to be one. If a constant alignment is specified, the value result of the
+allocation is guaranteed to be aligned to at least that boundary. The
+alignment may not be greater than ``1 << 29``. If not specified, or if
+zero, the target can choose to align the allocation on any convenient
+boundary compatible with the type.
+
+'``type``' may be any sized type.
+
+Semantics:
+""""""""""
+
+Memory is allocated; a pointer is returned. The operation is undefined
+if there is insufficient stack space for the allocation. '``alloca``'d
+memory is automatically released when the function returns. The
+'``alloca``' instruction is commonly used to represent automatic
+variables that must have an address available. When the function returns
+(either with the ``ret`` or ``resume`` instructions), the memory is
+reclaimed. Allocating zero bytes is legal, but the result is undefined.
+The order in which memory is allocated (ie., which way the stack grows)
+is not specified.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %ptr = alloca i32 ; yields i32*:ptr
+ %ptr = alloca i32, i32 4 ; yields i32*:ptr
+ %ptr = alloca i32, i32 4, align 1024 ; yields i32*:ptr
+ %ptr = alloca i32, align 1024 ; yields i32*:ptr
+
+.. _i_load:
+
+'``load``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = load [volatile] <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>][, !invariant.load !<index>][, !nonnull !<index>]
+ <result> = load atomic [volatile] <ty>* <pointer> [singlethread] <ordering>, align <alignment>
+ !<index> = !{ i32 1 }
+
+Overview:
+"""""""""
+
+The '``load``' instruction is used to read from memory.
+
+Arguments:
+""""""""""
+
+The argument to the ``load`` instruction specifies the memory address
+from which to load. The pointer must point to a :ref:`first
+class <t_firstclass>` type. If the ``load`` is marked as ``volatile``,
+then the optimizer is not allowed to modify the number or order of
+execution of this ``load`` with other :ref:`volatile
+operations <volatile>`.
+
+If the ``load`` is marked as ``atomic``, it takes an extra
+:ref:`ordering <ordering>` and optional ``singlethread`` argument. The
+``release`` and ``acq_rel`` orderings are not valid on ``load``
+instructions. Atomic loads produce :ref:`defined <memmodel>` results
+when they may see multiple atomic stores. The type of the pointee must
+be an integer type whose bit width is a power of two greater than or
+equal to eight and less than or equal to a target-specific size limit.
+``align`` must be explicitly specified on atomic loads, and the load has
+undefined behavior if the alignment is not set to a value which is at
+least the size in bytes of the pointee. ``!nontemporal`` does not have
+any defined semantics for atomic loads.
+
+The optional constant ``align`` argument specifies the alignment of the
+operation (that is, the alignment of the memory address). A value of 0
+or an omitted ``align`` argument means that the operation has the ABI
+alignment for the target. It is the responsibility of the code emitter
+to ensure that the alignment information is correct. Overestimating the
+alignment results in undefined behavior. Underestimating the alignment
+may produce less efficient code. An alignment of 1 is always safe. The
+maximum possible alignment is ``1 << 29``.
+
+The optional ``!nontemporal`` metadata must reference a single
+metadata name ``<index>`` corresponding to a metadata node with one
+``i32`` entry of value 1. The existence of the ``!nontemporal``
+metadata on the instruction tells the optimizer and code generator
+that this load is not expected to be reused in the cache. The code
+generator may select special instructions to save cache bandwidth, such
+as the ``MOVNT`` instruction on x86.
+
+The optional ``!invariant.load`` metadata must reference a single
+metadata name ``<index>`` corresponding to a metadata node with no
+entries. The existence of the ``!invariant.load`` metadata on the
+instruction tells the optimizer and code generator that the address
+operand to this load points to memory which can be assumed unchanged.
+Being invariant does not imply that a location is dereferenceable,
+but it does imply that once the location is known dereferenceable
+its value is henceforth unchanging.
+
+The optional ``!nonnull`` metadata must reference a single
+metadata name ``<index>`` corresponding to a metadata node with no
+entries. The existence of the ``!nonnull`` metadata on the
+instruction tells the optimizer that the value loaded is known to
+never be null. This is analogous to the ''nonnull'' attribute
+on parameters and return values. This metadata can only be applied
+to loads of a pointer type.
+
+Semantics:
+""""""""""
+
+The location of memory pointed to is loaded. If the value being loaded
+is of scalar type then the number of bytes read does not exceed the
+minimum number of bytes needed to hold all bits of the type. For
+example, loading an ``i24`` reads at most three bytes. When loading a
+value of a type like ``i20`` with a size that is not an integral number
+of bytes, the result is undefined if the value was not originally
+written using a store of the same type.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %ptr = alloca i32 ; yields i32*:ptr
+ store i32 3, i32* %ptr ; yields void
+ %val = load i32* %ptr ; yields i32:val = i32 3
+
+.. _i_store:
+
+'``store``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ store [volatile] <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] ; yields void
+ store atomic [volatile] <ty> <value>, <ty>* <pointer> [singlethread] <ordering>, align <alignment> ; yields void
+
+Overview:
+"""""""""
+
+The '``store``' instruction is used to write to memory.
+
+Arguments:
+""""""""""
+
+There are two arguments to the ``store`` instruction: a value to store
+and an address at which to store it. The type of the ``<pointer>``
+operand must be a pointer to the :ref:`first class <t_firstclass>` type of
+the ``<value>`` operand. If the ``store`` is marked as ``volatile``,
+then the optimizer is not allowed to modify the number or order of
+execution of this ``store`` with other :ref:`volatile
+operations <volatile>`.
+
+If the ``store`` is marked as ``atomic``, it takes an extra
+:ref:`ordering <ordering>` and optional ``singlethread`` argument. The
+``acquire`` and ``acq_rel`` orderings aren't valid on ``store``
+instructions. Atomic loads produce :ref:`defined <memmodel>` results
+when they may see multiple atomic stores. The type of the pointee must
+be an integer type whose bit width is a power of two greater than or
+equal to eight and less than or equal to a target-specific size limit.
+``align`` must be explicitly specified on atomic stores, and the store
+has undefined behavior if the alignment is not set to a value which is
+at least the size in bytes of the pointee. ``!nontemporal`` does not
+have any defined semantics for atomic stores.
+
+The optional constant ``align`` argument specifies the alignment of the
+operation (that is, the alignment of the memory address). A value of 0
+or an omitted ``align`` argument means that the operation has the ABI
+alignment for the target. It is the responsibility of the code emitter
+to ensure that the alignment information is correct. Overestimating the
+alignment results in undefined behavior. Underestimating the
+alignment may produce less efficient code. An alignment of 1 is always
+safe. The maximum possible alignment is ``1 << 29``.
+
+The optional ``!nontemporal`` metadata must reference a single metadata
+name ``<index>`` corresponding to a metadata node with one ``i32`` entry of
+value 1. The existence of the ``!nontemporal`` metadata on the instruction
+tells the optimizer and code generator that this load is not expected to
+be reused in the cache. The code generator may select special
+instructions to save cache bandwidth, such as the MOVNT instruction on
+x86.
+
+Semantics:
+""""""""""
+
+The contents of memory are updated to contain ``<value>`` at the
+location specified by the ``<pointer>`` operand. If ``<value>`` is
+of scalar type then the number of bytes written does not exceed the
+minimum number of bytes needed to hold all bits of the type. For
+example, storing an ``i24`` writes at most three bytes. When writing a
+value of a type like ``i20`` with a size that is not an integral number
+of bytes, it is unspecified what happens to the extra bits that do not
+belong to the type, but they will typically be overwritten.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %ptr = alloca i32 ; yields i32*:ptr
+ store i32 3, i32* %ptr ; yields void
+ %val = load i32* %ptr ; yields i32:val = i32 3
+
+.. _i_fence:
+
+'``fence``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ fence [singlethread] <ordering> ; yields void
+
+Overview:
+"""""""""
+
+The '``fence``' instruction is used to introduce happens-before edges
+between operations.
+
+Arguments:
+""""""""""
+
+'``fence``' instructions take an :ref:`ordering <ordering>` argument which
+defines what *synchronizes-with* edges they add. They can only be given
+``acquire``, ``release``, ``acq_rel``, and ``seq_cst`` orderings.
+
+Semantics:
+""""""""""
+
+A fence A which has (at least) ``release`` ordering semantics
+*synchronizes with* a fence B with (at least) ``acquire`` ordering
+semantics if and only if there exist atomic operations X and Y, both
+operating on some atomic object M, such that A is sequenced before X, X
+modifies M (either directly or through some side effect of a sequence
+headed by X), Y is sequenced before B, and Y observes M. This provides a
+*happens-before* dependency between A and B. Rather than an explicit
+``fence``, one (but not both) of the atomic operations X or Y might
+provide a ``release`` or ``acquire`` (resp.) ordering constraint and
+still *synchronize-with* the explicit ``fence`` and establish the
+*happens-before* edge.
+
+A ``fence`` which has ``seq_cst`` ordering, in addition to having both
+``acquire`` and ``release`` semantics specified above, participates in
+the global program order of other ``seq_cst`` operations and/or fences.
+
+The optional ":ref:`singlethread <singlethread>`" argument specifies
+that the fence only synchronizes with other fences in the same thread.
+(This is useful for interacting with signal handlers.)
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ fence acquire ; yields void
+ fence singlethread seq_cst ; yields void
+
+.. _i_cmpxchg:
+
+'``cmpxchg``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ cmpxchg [weak] [volatile] <ty>* <pointer>, <ty> <cmp>, <ty> <new> [singlethread] <success ordering> <failure ordering> ; yields { ty, i1 }
+
+Overview:
+"""""""""
+
+The '``cmpxchg``' instruction is used to atomically modify memory. It
+loads a value in memory and compares it to a given value. If they are
+equal, it tries to store a new value into the memory.
+
+Arguments:
+""""""""""
+
+There are three arguments to the '``cmpxchg``' instruction: an address
+to operate on, a value to compare to the value currently be at that
+address, and a new value to place at that address if the compared values
+are equal. The type of '<cmp>' must be an integer type whose bit width
+is a power of two greater than or equal to eight and less than or equal
+to a target-specific size limit. '<cmp>' and '<new>' must have the same
+type, and the type of '<pointer>' must be a pointer to that type. If the
+``cmpxchg`` is marked as ``volatile``, then the optimizer is not allowed
+to modify the number or order of execution of this ``cmpxchg`` with
+other :ref:`volatile operations <volatile>`.
+
+The success and failure :ref:`ordering <ordering>` arguments specify how this
+``cmpxchg`` synchronizes with other atomic operations. Both ordering parameters
+must be at least ``monotonic``, the ordering constraint on failure must be no
+stronger than that on success, and the failure ordering cannot be either
+``release`` or ``acq_rel``.
+
+The optional "``singlethread``" argument declares that the ``cmpxchg``
+is only atomic with respect to code (usually signal handlers) running in
+the same thread as the ``cmpxchg``. Otherwise the cmpxchg is atomic with
+respect to all other code in the system.
+
+The pointer passed into cmpxchg must have alignment greater than or
+equal to the size in memory of the operand.
+
+Semantics:
+""""""""""
+
+The contents of memory at the location specified by the '``<pointer>``' operand
+is read and compared to '``<cmp>``'; if the read value is the equal, the
+'``<new>``' is written. The original value at the location is returned, together
+with a flag indicating success (true) or failure (false).
+
+If the cmpxchg operation is marked as ``weak`` then a spurious failure is
+permitted: the operation may not write ``<new>`` even if the comparison
+matched.
+
+If the cmpxchg operation is strong (the default), the i1 value is 1 if and only
+if the value loaded equals ``cmp``.
+
+A successful ``cmpxchg`` is a read-modify-write instruction for the purpose of
+identifying release sequences. A failed ``cmpxchg`` is equivalent to an atomic
+load with an ordering parameter determined the second ordering parameter.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ entry:
+ %orig = atomic load i32* %ptr unordered ; yields i32
+ br label %loop
+
+ loop:
+ %cmp = phi i32 [ %orig, %entry ], [%old, %loop]
+ %squared = mul i32 %cmp, %cmp
+ %val_success = cmpxchg i32* %ptr, i32 %cmp, i32 %squared acq_rel monotonic ; yields { i32, i1 }
+ %value_loaded = extractvalue { i32, i1 } %val_success, 0
+ %success = extractvalue { i32, i1 } %val_success, 1
+ br i1 %success, label %done, label %loop
+
+ done:
+ ...
+
+.. _i_atomicrmw:
+
+'``atomicrmw``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ atomicrmw [volatile] <operation> <ty>* <pointer>, <ty> <value> [singlethread] <ordering> ; yields ty
+
+Overview:
+"""""""""
+
+The '``atomicrmw``' instruction is used to atomically modify memory.
+
+Arguments:
+""""""""""
+
+There are three arguments to the '``atomicrmw``' instruction: an
+operation to apply, an address whose value to modify, an argument to the
+operation. The operation must be one of the following keywords:
+
+- xchg
+- add
+- sub
+- and
+- nand
+- or
+- xor
+- max
+- min
+- umax
+- umin
+
+The type of '<value>' must be an integer type whose bit width is a power
+of two greater than or equal to eight and less than or equal to a
+target-specific size limit. The type of the '``<pointer>``' operand must
+be a pointer to that type. If the ``atomicrmw`` is marked as
+``volatile``, then the optimizer is not allowed to modify the number or
+order of execution of this ``atomicrmw`` with other :ref:`volatile
+operations <volatile>`.
+
+Semantics:
+""""""""""
+
+The contents of memory at the location specified by the '``<pointer>``'
+operand are atomically read, modified, and written back. The original
+value at the location is returned. The modification is specified by the
+operation argument:
+
+- xchg: ``*ptr = val``
+- add: ``*ptr = *ptr + val``
+- sub: ``*ptr = *ptr - val``
+- and: ``*ptr = *ptr & val``
+- nand: ``*ptr = ~(*ptr & val)``
+- or: ``*ptr = *ptr | val``
+- xor: ``*ptr = *ptr ^ val``
+- max: ``*ptr = *ptr > val ? *ptr : val`` (using a signed comparison)
+- min: ``*ptr = *ptr < val ? *ptr : val`` (using a signed comparison)
+- umax: ``*ptr = *ptr > val ? *ptr : val`` (using an unsigned
+ comparison)
+- umin: ``*ptr = *ptr < val ? *ptr : val`` (using an unsigned
+ comparison)
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %old = atomicrmw add i32* %ptr, i32 1 acquire ; yields i32
+
+.. _i_getelementptr:
+
+'``getelementptr``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = getelementptr <pty>* <ptrval>{, <ty> <idx>}*
+ <result> = getelementptr inbounds <pty>* <ptrval>{, <ty> <idx>}*
+ <result> = getelementptr <ptr vector> ptrval, <vector index type> idx
+
+Overview:
+"""""""""
+
+The '``getelementptr``' instruction is used to get the address of a
+subelement of an :ref:`aggregate <t_aggregate>` data structure. It performs
+address calculation only and does not access memory.
+
+Arguments:
+""""""""""
+
+The first argument is always a pointer or a vector of pointers, and
+forms the basis of the calculation. The remaining arguments are indices
+that indicate which of the elements of the aggregate object are indexed.
+The interpretation of each index is dependent on the type being indexed
+into. The first index always indexes the pointer value given as the
+first argument, the second index indexes a value of the type pointed to
+(not necessarily the value directly pointed to, since the first index
+can be non-zero), etc. The first type indexed into must be a pointer
+value, subsequent types can be arrays, vectors, and structs. Note that
+subsequent types being indexed into can never be pointers, since that
+would require loading the pointer before continuing calculation.
+
+The type of each index argument depends on the type it is indexing into.
+When indexing into a (optionally packed) structure, only ``i32`` integer
+**constants** are allowed (when using a vector of indices they must all
+be the **same** ``i32`` integer constant). When indexing into an array,
+pointer or vector, integers of any width are allowed, and they are not
+required to be constant. These integers are treated as signed values
+where relevant.
+
+For example, let's consider a C code fragment and how it gets compiled
+to LLVM:
+
+.. code-block:: c
+
+ struct RT {
+ char A;
+ int B[10][20];
+ char C;
+ };
+ struct ST {
+ int X;
+ double Y;
+ struct RT Z;
+ };
+
+ int *foo(struct ST *s) {
+ return &s[1].Z.B[5][13];
+ }
+
+The LLVM code generated by Clang is:
+
+.. code-block:: llvm
+
+ %struct.RT = type { i8, [10 x [20 x i32]], i8 }
+ %struct.ST = type { i32, double, %struct.RT }
+
+ define i32* @foo(%struct.ST* %s) nounwind uwtable readnone optsize ssp {
+ entry:
+ %arrayidx = getelementptr inbounds %struct.ST* %s, i64 1, i32 2, i32 1, i64 5, i64 13
+ ret i32* %arrayidx
+ }
+
+Semantics:
+""""""""""
+
+In the example above, the first index is indexing into the
+'``%struct.ST*``' type, which is a pointer, yielding a '``%struct.ST``'
+= '``{ i32, double, %struct.RT }``' type, a structure. The second index
+indexes into the third element of the structure, yielding a
+'``%struct.RT``' = '``{ i8 , [10 x [20 x i32]], i8 }``' type, another
+structure. The third index indexes into the second element of the
+structure, yielding a '``[10 x [20 x i32]]``' type, an array. The two
+dimensions of the array are subscripted into, yielding an '``i32``'
+type. The '``getelementptr``' instruction returns a pointer to this
+element, thus computing a value of '``i32*``' type.
+
+Note that it is perfectly legal to index partially through a structure,
+returning a pointer to an inner element. Because of this, the LLVM code
+for the given testcase is equivalent to:
+
+.. code-block:: llvm
+
+ define i32* @foo(%struct.ST* %s) {
+ %t1 = getelementptr %struct.ST* %s, i32 1 ; yields %struct.ST*:%t1
+ %t2 = getelementptr %struct.ST* %t1, i32 0, i32 2 ; yields %struct.RT*:%t2
+ %t3 = getelementptr %struct.RT* %t2, i32 0, i32 1 ; yields [10 x [20 x i32]]*:%t3
+ %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 ; yields [20 x i32]*:%t4
+ %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 ; yields i32*:%t5
+ ret i32* %t5
+ }
+
+If the ``inbounds`` keyword is present, the result value of the
+``getelementptr`` is a :ref:`poison value <poisonvalues>` if the base
+pointer is not an *in bounds* address of an allocated object, or if any
+of the addresses that would be formed by successive addition of the
+offsets implied by the indices to the base address with infinitely
+precise signed arithmetic are not an *in bounds* address of that
+allocated object. The *in bounds* addresses for an allocated object are
+all the addresses that point into the object, plus the address one byte
+past the end. In cases where the base is a vector of pointers the
+``inbounds`` keyword applies to each of the computations element-wise.
+
+If the ``inbounds`` keyword is not present, the offsets are added to the
+base address with silently-wrapping two's complement arithmetic. If the
+offsets have a different width from the pointer, they are sign-extended
+or truncated to the width of the pointer. The result value of the
+``getelementptr`` may be outside the object pointed to by the base
+pointer. The result value may not necessarily be used to access memory
+though, even if it happens to point into allocated storage. See the
+:ref:`Pointer Aliasing Rules <pointeraliasing>` section for more
+information.
+
+The getelementptr instruction is often confusing. For some more insight
+into how it works, see :doc:`the getelementptr FAQ <GetElementPtr>`.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ ; yields [12 x i8]*:aptr
+ %aptr = getelementptr {i32, [12 x i8]}* %saptr, i64 0, i32 1
+ ; yields i8*:vptr
+ %vptr = getelementptr {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1
+ ; yields i8*:eptr
+ %eptr = getelementptr [12 x i8]* %aptr, i64 0, i32 1
+ ; yields i32*:iptr
+ %iptr = getelementptr [10 x i32]* @arr, i16 0, i16 0
+
+In cases where the pointer argument is a vector of pointers, each index
+must be a vector with the same number of elements. For example:
+
+.. code-block:: llvm
+
+ %A = getelementptr <4 x i8*> %ptrs, <4 x i64> %offsets,
+
+Conversion Operations
+---------------------
+
+The instructions in this category are the conversion instructions
+(casting) which all take a single operand and a type. They perform
+various bit conversions on the operand.
+
+'``trunc .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = trunc <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``trunc``' instruction truncates its operand to the type ``ty2``.
+
+Arguments:
+""""""""""
+
+The '``trunc``' instruction takes a value to trunc, and a type to trunc
+it to. Both types must be of :ref:`integer <t_integer>` types, or vectors
+of the same number of integers. The bit size of the ``value`` must be
+larger than the bit size of the destination type, ``ty2``. Equal sized
+types are not allowed.
+
+Semantics:
+""""""""""
+
+The '``trunc``' instruction truncates the high order bits in ``value``
+and converts the remaining bits to ``ty2``. Since the source size must
+be larger than the destination size, ``trunc`` cannot be a *no-op cast*.
+It will always truncate bits.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = trunc i32 257 to i8 ; yields i8:1
+ %Y = trunc i32 123 to i1 ; yields i1:true
+ %Z = trunc i32 122 to i1 ; yields i1:false
+ %W = trunc <2 x i16> <i16 8, i16 7> to <2 x i8> ; yields <i8 8, i8 7>
+
+'``zext .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = zext <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``zext``' instruction zero extends its operand to type ``ty2``.
+
+Arguments:
+""""""""""
+
+The '``zext``' instruction takes a value to cast, and a type to cast it
+to. Both types must be of :ref:`integer <t_integer>` types, or vectors of
+the same number of integers. The bit size of the ``value`` must be
+smaller than the bit size of the destination type, ``ty2``.
+
+Semantics:
+""""""""""
+
+The ``zext`` fills the high order bits of the ``value`` with zero bits
+until it reaches the size of the destination type, ``ty2``.
+
+When zero extending from i1, the result will always be either 0 or 1.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = zext i32 257 to i64 ; yields i64:257
+ %Y = zext i1 true to i32 ; yields i32:1
+ %Z = zext <2 x i16> <i16 8, i16 7> to <2 x i32> ; yields <i32 8, i32 7>
+
+'``sext .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = sext <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``sext``' sign extends ``value`` to the type ``ty2``.
+
+Arguments:
+""""""""""
+
+The '``sext``' instruction takes a value to cast, and a type to cast it
+to. Both types must be of :ref:`integer <t_integer>` types, or vectors of
+the same number of integers. The bit size of the ``value`` must be
+smaller than the bit size of the destination type, ``ty2``.
+
+Semantics:
+""""""""""
+
+The '``sext``' instruction performs a sign extension by copying the sign
+bit (highest order bit) of the ``value`` until it reaches the bit size
+of the type ``ty2``.
+
+When sign extending from i1, the extension always results in -1 or 0.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = sext i8 -1 to i16 ; yields i16 :65535
+ %Y = sext i1 true to i32 ; yields i32:-1
+ %Z = sext <2 x i16> <i16 8, i16 7> to <2 x i32> ; yields <i32 8, i32 7>
+
+'``fptrunc .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fptrunc <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``fptrunc``' instruction truncates ``value`` to type ``ty2``.
+
+Arguments:
+""""""""""
+
+The '``fptrunc``' instruction takes a :ref:`floating point <t_floating>`
+value to cast and a :ref:`floating point <t_floating>` type to cast it to.
+The size of ``value`` must be larger than the size of ``ty2``. This
+implies that ``fptrunc`` cannot be used to make a *no-op cast*.
+
+Semantics:
+""""""""""
+
+The '``fptrunc``' instruction truncates a ``value`` from a larger
+:ref:`floating point <t_floating>` type to a smaller :ref:`floating
+point <t_floating>` type. If the value cannot fit within the
+destination type, ``ty2``, then the results are undefined.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = fptrunc double 123.0 to float ; yields float:123.0
+ %Y = fptrunc double 1.0E+300 to float ; yields undefined
+
+'``fpext .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fpext <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``fpext``' extends a floating point ``value`` to a larger floating
+point value.
+
+Arguments:
+""""""""""
+
+The '``fpext``' instruction takes a :ref:`floating point <t_floating>`
+``value`` to cast, and a :ref:`floating point <t_floating>` type to cast it
+to. The source type must be smaller than the destination type.
+
+Semantics:
+""""""""""
+
+The '``fpext``' instruction extends the ``value`` from a smaller
+:ref:`floating point <t_floating>` type to a larger :ref:`floating
+point <t_floating>` type. The ``fpext`` cannot be used to make a
+*no-op cast* because it always changes bits. Use ``bitcast`` to make a
+*no-op cast* for a floating point cast.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = fpext float 3.125 to double ; yields double:3.125000e+00
+ %Y = fpext double %X to fp128 ; yields fp128:0xL00000000000000004000900000000000
+
+'``fptoui .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fptoui <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``fptoui``' converts a floating point ``value`` to its unsigned
+integer equivalent of type ``ty2``.
+
+Arguments:
+""""""""""
+
+The '``fptoui``' instruction takes a value to cast, which must be a
+scalar or vector :ref:`floating point <t_floating>` value, and a type to
+cast it to ``ty2``, which must be an :ref:`integer <t_integer>` type. If
+``ty`` is a vector floating point type, ``ty2`` must be a vector integer
+type with the same number of elements as ``ty``
+
+Semantics:
+""""""""""
+
+The '``fptoui``' instruction converts its :ref:`floating
+point <t_floating>` operand into the nearest (rounding towards zero)
+unsigned integer value. If the value cannot fit in ``ty2``, the results
+are undefined.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = fptoui double 123.0 to i32 ; yields i32:123
+ %Y = fptoui float 1.0E+300 to i1 ; yields undefined:1
+ %Z = fptoui float 1.04E+17 to i8 ; yields undefined:1
+
+'``fptosi .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fptosi <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``fptosi``' instruction converts :ref:`floating point <t_floating>`
+``value`` to type ``ty2``.
+
+Arguments:
+""""""""""
+
+The '``fptosi``' instruction takes a value to cast, which must be a
+scalar or vector :ref:`floating point <t_floating>` value, and a type to
+cast it to ``ty2``, which must be an :ref:`integer <t_integer>` type. If
+``ty`` is a vector floating point type, ``ty2`` must be a vector integer
+type with the same number of elements as ``ty``
+
+Semantics:
+""""""""""
+
+The '``fptosi``' instruction converts its :ref:`floating
+point <t_floating>` operand into the nearest (rounding towards zero)
+signed integer value. If the value cannot fit in ``ty2``, the results
+are undefined.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = fptosi double -123.0 to i32 ; yields i32:-123
+ %Y = fptosi float 1.0E-247 to i1 ; yields undefined:1
+ %Z = fptosi float 1.04E+17 to i8 ; yields undefined:1
+
+'``uitofp .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = uitofp <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``uitofp``' instruction regards ``value`` as an unsigned integer
+and converts that value to the ``ty2`` type.
+
+Arguments:
+""""""""""
+
+The '``uitofp``' instruction takes a value to cast, which must be a
+scalar or vector :ref:`integer <t_integer>` value, and a type to cast it to
+``ty2``, which must be an :ref:`floating point <t_floating>` type. If
+``ty`` is a vector integer type, ``ty2`` must be a vector floating point
+type with the same number of elements as ``ty``
+
+Semantics:
+""""""""""
+
+The '``uitofp``' instruction interprets its operand as an unsigned
+integer quantity and converts it to the corresponding floating point
+value. If the value cannot fit in the floating point value, the results
+are undefined.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = uitofp i32 257 to float ; yields float:257.0
+ %Y = uitofp i8 -1 to double ; yields double:255.0
+
+'``sitofp .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = sitofp <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``sitofp``' instruction regards ``value`` as a signed integer and
+converts that value to the ``ty2`` type.
+
+Arguments:
+""""""""""
+
+The '``sitofp``' instruction takes a value to cast, which must be a
+scalar or vector :ref:`integer <t_integer>` value, and a type to cast it to
+``ty2``, which must be an :ref:`floating point <t_floating>` type. If
+``ty`` is a vector integer type, ``ty2`` must be a vector floating point
+type with the same number of elements as ``ty``
+
+Semantics:
+""""""""""
+
+The '``sitofp``' instruction interprets its operand as a signed integer
+quantity and converts it to the corresponding floating point value. If
+the value cannot fit in the floating point value, the results are
+undefined.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = sitofp i32 257 to float ; yields float:257.0
+ %Y = sitofp i8 -1 to double ; yields double:-1.0
+
+.. _i_ptrtoint:
+
+'``ptrtoint .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = ptrtoint <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``ptrtoint``' instruction converts the pointer or a vector of
+pointers ``value`` to the integer (or vector of integers) type ``ty2``.
+
+Arguments:
+""""""""""
+
+The '``ptrtoint``' instruction takes a ``value`` to cast, which must be
+a a value of type :ref:`pointer <t_pointer>` or a vector of pointers, and a
+type to cast it to ``ty2``, which must be an :ref:`integer <t_integer>` or
+a vector of integers type.
+
+Semantics:
+""""""""""
+
+The '``ptrtoint``' instruction converts ``value`` to integer type
+``ty2`` by interpreting the pointer value as an integer and either
+truncating or zero extending that value to the size of the integer type.
+If ``value`` is smaller than ``ty2`` then a zero extension is done. If
+``value`` is larger than ``ty2`` then a truncation is done. If they are
+the same size, then nothing is done (*no-op cast*) other than a type
+change.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = ptrtoint i32* %P to i8 ; yields truncation on 32-bit architecture
+ %Y = ptrtoint i32* %P to i64 ; yields zero extension on 32-bit architecture
+ %Z = ptrtoint <4 x i32*> %P to <4 x i64>; yields vector zero extension for a vector of addresses on 32-bit architecture
+
+.. _i_inttoptr:
+
+'``inttoptr .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = inttoptr <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``inttoptr``' instruction converts an integer ``value`` to a
+pointer type, ``ty2``.
+
+Arguments:
+""""""""""
+
+The '``inttoptr``' instruction takes an :ref:`integer <t_integer>` value to
+cast, and a type to cast it to, which must be a :ref:`pointer <t_pointer>`
+type.
+
+Semantics:
+""""""""""
+
+The '``inttoptr``' instruction converts ``value`` to type ``ty2`` by
+applying either a zero extension or a truncation depending on the size
+of the integer ``value``. If ``value`` is larger than the size of a
+pointer then a truncation is done. If ``value`` is smaller than the size
+of a pointer then a zero extension is done. If they are the same size,
+nothing is done (*no-op cast*).
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = inttoptr i32 255 to i32* ; yields zero extension on 64-bit architecture
+ %Y = inttoptr i32 255 to i32* ; yields no-op on 32-bit architecture
+ %Z = inttoptr i64 0 to i32* ; yields truncation on 32-bit architecture
+ %Z = inttoptr <4 x i32> %G to <4 x i8*>; yields truncation of vector G to four pointers
+
+.. _i_bitcast:
+
+'``bitcast .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = bitcast <ty> <value> to <ty2> ; yields ty2
+
+Overview:
+"""""""""
+
+The '``bitcast``' instruction converts ``value`` to type ``ty2`` without
+changing any bits.
+
+Arguments:
+""""""""""
+
+The '``bitcast``' instruction takes a value to cast, which must be a
+non-aggregate first class value, and a type to cast it to, which must
+also be a non-aggregate :ref:`first class <t_firstclass>` type. The
+bit sizes of ``value`` and the destination type, ``ty2``, must be
+identical. If the source type is a pointer, the destination type must
+also be a pointer of the same size. This instruction supports bitwise
+conversion of vectors to integers and to vectors of other types (as
+long as they have the same size).
+
+Semantics:
+""""""""""
+
+The '``bitcast``' instruction converts ``value`` to type ``ty2``. It
+is always a *no-op cast* because no bits change with this
+conversion. The conversion is done as if the ``value`` had been stored
+to memory and read back as type ``ty2``. Pointer (or vector of
+pointers) types may only be converted to other pointer (or vector of
+pointers) types with the same address space through this instruction.
+To convert pointers to other types, use the :ref:`inttoptr <i_inttoptr>`
+or :ref:`ptrtoint <i_ptrtoint>` instructions first.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = bitcast i8 255 to i8 ; yields i8 :-1
+ %Y = bitcast i32* %x to sint* ; yields sint*:%x
+ %Z = bitcast <2 x int> %V to i64; ; yields i64: %V
+ %Z = bitcast <2 x i32*> %V to <2 x i64*> ; yields <2 x i64*>
+
+.. _i_addrspacecast:
+
+'``addrspacecast .. to``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = addrspacecast <pty> <ptrval> to <pty2> ; yields pty2
+
+Overview:
+"""""""""
+
+The '``addrspacecast``' instruction converts ``ptrval`` from ``pty`` in
+address space ``n`` to type ``pty2`` in address space ``m``.
+
+Arguments:
+""""""""""
+
+The '``addrspacecast``' instruction takes a pointer or vector of pointer value
+to cast and a pointer type to cast it to, which must have a different
+address space.
+
+Semantics:
+""""""""""
+
+The '``addrspacecast``' instruction converts the pointer value
+``ptrval`` to type ``pty2``. It can be a *no-op cast* or a complex
+value modification, depending on the target and the address space
+pair. Pointer conversions within the same address space must be
+performed with the ``bitcast`` instruction. Note that if the address space
+conversion is legal then both result and operand refer to the same memory
+location.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = addrspacecast i32* %x to i32 addrspace(1)* ; yields i32 addrspace(1)*:%x
+ %Y = addrspacecast i32 addrspace(1)* %y to i64 addrspace(2)* ; yields i64 addrspace(2)*:%y
+ %Z = addrspacecast <4 x i32*> %z to <4 x float addrspace(3)*> ; yields <4 x float addrspace(3)*>:%z
+
+.. _otherops:
+
+Other Operations
+----------------
+
+The instructions in this category are the "miscellaneous" instructions,
+which defy better classification.
+
+.. _i_icmp:
+
+'``icmp``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = icmp <cond> <ty> <op1>, <op2> ; yields i1 or <N x i1>:result
+
+Overview:
+"""""""""
+
+The '``icmp``' instruction returns a boolean value or a vector of
+boolean values based on comparison of its two integer, integer vector,
+pointer, or pointer vector operands.
+
+Arguments:
+""""""""""
+
+The '``icmp``' instruction takes three operands. The first operand is
+the condition code indicating the kind of comparison to perform. It is
+not a value, just a keyword. The possible condition code are:
+
+#. ``eq``: equal
+#. ``ne``: not equal
+#. ``ugt``: unsigned greater than
+#. ``uge``: unsigned greater or equal
+#. ``ult``: unsigned less than
+#. ``ule``: unsigned less or equal
+#. ``sgt``: signed greater than
+#. ``sge``: signed greater or equal
+#. ``slt``: signed less than
+#. ``sle``: signed less or equal
+
+The remaining two arguments must be :ref:`integer <t_integer>` or
+:ref:`pointer <t_pointer>` or integer :ref:`vector <t_vector>` typed. They
+must also be identical types.
+
+Semantics:
+""""""""""
+
+The '``icmp``' compares ``op1`` and ``op2`` according to the condition
+code given as ``cond``. The comparison performed always yields either an
+:ref:`i1 <t_integer>` or vector of ``i1`` result, as follows:
+
+#. ``eq``: yields ``true`` if the operands are equal, ``false``
+ otherwise. No sign interpretation is necessary or performed.
+#. ``ne``: yields ``true`` if the operands are unequal, ``false``
+ otherwise. No sign interpretation is necessary or performed.
+#. ``ugt``: interprets the operands as unsigned values and yields
+ ``true`` if ``op1`` is greater than ``op2``.
+#. ``uge``: interprets the operands as unsigned values and yields
+ ``true`` if ``op1`` is greater than or equal to ``op2``.
+#. ``ult``: interprets the operands as unsigned values and yields
+ ``true`` if ``op1`` is less than ``op2``.
+#. ``ule``: interprets the operands as unsigned values and yields
+ ``true`` if ``op1`` is less than or equal to ``op2``.
+#. ``sgt``: interprets the operands as signed values and yields ``true``
+ if ``op1`` is greater than ``op2``.
+#. ``sge``: interprets the operands as signed values and yields ``true``
+ if ``op1`` is greater than or equal to ``op2``.
+#. ``slt``: interprets the operands as signed values and yields ``true``
+ if ``op1`` is less than ``op2``.
+#. ``sle``: interprets the operands as signed values and yields ``true``
+ if ``op1`` is less than or equal to ``op2``.
+
+If the operands are :ref:`pointer <t_pointer>` typed, the pointer values
+are compared as if they were integers.
+
+If the operands are integer vectors, then they are compared element by
+element. The result is an ``i1`` vector with the same number of elements
+as the values being compared. Otherwise, the result is an ``i1``.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = icmp eq i32 4, 5 ; yields: result=false
+ <result> = icmp ne float* %X, %X ; yields: result=false
+ <result> = icmp ult i16 4, 5 ; yields: result=true
+ <result> = icmp sgt i16 4, 5 ; yields: result=false
+ <result> = icmp ule i16 -4, 5 ; yields: result=false
+ <result> = icmp sge i16 4, 5 ; yields: result=false
+
+Note that the code generator does not yet support vector types with the
+``icmp`` instruction.
+
+.. _i_fcmp:
+
+'``fcmp``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = fcmp <cond> <ty> <op1>, <op2> ; yields i1 or <N x i1>:result
+
+Overview:
+"""""""""
+
+The '``fcmp``' instruction returns a boolean value or vector of boolean
+values based on comparison of its operands.
+
+If the operands are floating point scalars, then the result type is a
+boolean (:ref:`i1 <t_integer>`).
+
+If the operands are floating point vectors, then the result type is a
+vector of boolean with the same number of elements as the operands being
+compared.
+
+Arguments:
+""""""""""
+
+The '``fcmp``' instruction takes three operands. The first operand is
+the condition code indicating the kind of comparison to perform. It is
+not a value, just a keyword. The possible condition code are:
+
+#. ``false``: no comparison, always returns false
+#. ``oeq``: ordered and equal
+#. ``ogt``: ordered and greater than
+#. ``oge``: ordered and greater than or equal
+#. ``olt``: ordered and less than
+#. ``ole``: ordered and less than or equal
+#. ``one``: ordered and not equal
+#. ``ord``: ordered (no nans)
+#. ``ueq``: unordered or equal
+#. ``ugt``: unordered or greater than
+#. ``uge``: unordered or greater than or equal
+#. ``ult``: unordered or less than
+#. ``ule``: unordered or less than or equal
+#. ``une``: unordered or not equal
+#. ``uno``: unordered (either nans)
+#. ``true``: no comparison, always returns true
+
+*Ordered* means that neither operand is a QNAN while *unordered* means
+that either operand may be a QNAN.
+
+Each of ``val1`` and ``val2`` arguments must be either a :ref:`floating
+point <t_floating>` type or a :ref:`vector <t_vector>` of floating point
+type. They must have identical types.
+
+Semantics:
+""""""""""
+
+The '``fcmp``' instruction compares ``op1`` and ``op2`` according to the
+condition code given as ``cond``. If the operands are vectors, then the
+vectors are compared element by element. Each comparison performed
+always yields an :ref:`i1 <t_integer>` result, as follows:
+
+#. ``false``: always yields ``false``, regardless of operands.
+#. ``oeq``: yields ``true`` if both operands are not a QNAN and ``op1``
+ is equal to ``op2``.
+#. ``ogt``: yields ``true`` if both operands are not a QNAN and ``op1``
+ is greater than ``op2``.
+#. ``oge``: yields ``true`` if both operands are not a QNAN and ``op1``
+ is greater than or equal to ``op2``.
+#. ``olt``: yields ``true`` if both operands are not a QNAN and ``op1``
+ is less than ``op2``.
+#. ``ole``: yields ``true`` if both operands are not a QNAN and ``op1``
+ is less than or equal to ``op2``.
+#. ``one``: yields ``true`` if both operands are not a QNAN and ``op1``
+ is not equal to ``op2``.
+#. ``ord``: yields ``true`` if both operands are not a QNAN.
+#. ``ueq``: yields ``true`` if either operand is a QNAN or ``op1`` is
+ equal to ``op2``.
+#. ``ugt``: yields ``true`` if either operand is a QNAN or ``op1`` is
+ greater than ``op2``.
+#. ``uge``: yields ``true`` if either operand is a QNAN or ``op1`` is
+ greater than or equal to ``op2``.
+#. ``ult``: yields ``true`` if either operand is a QNAN or ``op1`` is
+ less than ``op2``.
+#. ``ule``: yields ``true`` if either operand is a QNAN or ``op1`` is
+ less than or equal to ``op2``.
+#. ``une``: yields ``true`` if either operand is a QNAN or ``op1`` is
+ not equal to ``op2``.
+#. ``uno``: yields ``true`` if either operand is a QNAN.
+#. ``true``: always yields ``true``, regardless of operands.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ <result> = fcmp oeq float 4.0, 5.0 ; yields: result=false
+ <result> = fcmp one float 4.0, 5.0 ; yields: result=true
+ <result> = fcmp olt float 4.0, 5.0 ; yields: result=true
+ <result> = fcmp ueq double 1.0, 2.0 ; yields: result=false
+
+Note that the code generator does not yet support vector types with the
+``fcmp`` instruction.
+
+.. _i_phi:
+
+'``phi``' Instruction
+^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = phi <ty> [ <val0>, <label0>], ...
+
+Overview:
+"""""""""
+
+The '``phi``' instruction is used to implement the Ï node in the SSA
+graph representing the function.
+
+Arguments:
+""""""""""
+
+The type of the incoming values is specified with the first type field.
+After this, the '``phi``' instruction takes a list of pairs as
+arguments, with one pair for each predecessor basic block of the current
+block. Only values of :ref:`first class <t_firstclass>` type may be used as
+the value arguments to the PHI node. Only labels may be used as the
+label arguments.
+
+There must be no non-phi instructions between the start of a basic block
+and the PHI instructions: i.e. PHI instructions must be first in a basic
+block.
+
+For the purposes of the SSA form, the use of each incoming value is
+deemed to occur on the edge from the corresponding predecessor block to
+the current block (but after any definition of an '``invoke``'
+instruction's return value on the same edge).
+
+Semantics:
+""""""""""
+
+At runtime, the '``phi``' instruction logically takes on the value
+specified by the pair corresponding to the predecessor basic block that
+executed just prior to the current block.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ Loop: ; Infinite loop that counts from 0 on up...
+ %indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ]
+ %nextindvar = add i32 %indvar, 1
+ br label %Loop
+
+.. _i_select:
+
+'``select``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = select selty <cond>, <ty> <val1>, <ty> <val2> ; yields ty
+
+ selty is either i1 or {<N x i1>}
+
+Overview:
+"""""""""
+
+The '``select``' instruction is used to choose one value based on a
+condition, without IR-level branching.
+
+Arguments:
+""""""""""
+
+The '``select``' instruction requires an 'i1' value or a vector of 'i1'
+values indicating the condition, and two values of the same :ref:`first
+class <t_firstclass>` type. If the val1/val2 are vectors and the
+condition is a scalar, then entire vectors are selected, not individual
+elements.
+
+Semantics:
+""""""""""
+
+If the condition is an i1 and it evaluates to 1, the instruction returns
+the first value argument; otherwise, it returns the second value
+argument.
+
+If the condition is a vector of i1, then the value arguments must be
+vectors of the same size, and the selection is done element by element.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %X = select i1 true, i8 17, i8 42 ; yields i8:17
+
+.. _i_call:
+
+'``call``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <result> = [tail | musttail] call [cconv] [ret attrs] <ty> [<fnty>*] <fnptrval>(<function args>) [fn attrs]
+
+Overview:
+"""""""""
+
+The '``call``' instruction represents a simple function call.
+
+Arguments:
+""""""""""
+
+This instruction requires several arguments:
+
+#. The optional ``tail`` and ``musttail`` markers indicate that the optimizers
+ should perform tail call optimization. The ``tail`` marker is a hint that
+ `can be ignored <CodeGenerator.html#sibcallopt>`_. The ``musttail`` marker
+ means that the call must be tail call optimized in order for the program to
+ be correct. The ``musttail`` marker provides these guarantees:
+
+ #. The call will not cause unbounded stack growth if it is part of a
+ recursive cycle in the call graph.
+ #. Arguments with the :ref:`inalloca <attr_inalloca>` attribute are
+ forwarded in place.
+
+ Both markers imply that the callee does not access allocas or varargs from
+ the caller. Calls marked ``musttail`` must obey the following additional
+ rules:
+
+ - The call must immediately precede a :ref:`ret <i_ret>` instruction,
+ or a pointer bitcast followed by a ret instruction.
+ - The ret instruction must return the (possibly bitcasted) value
+ produced by the call or void.
+ - The caller and callee prototypes must match. Pointer types of
+ parameters or return types may differ in pointee type, but not
+ in address space.
+ - The calling conventions of the caller and callee must match.
+ - All ABI-impacting function attributes, such as sret, byval, inreg,
+ returned, and inalloca, must match.
+ - The callee must be varargs iff the caller is varargs. Bitcasting a
+ non-varargs function to the appropriate varargs type is legal so
+ long as the non-varargs prefixes obey the other rules.
+
+ Tail call optimization for calls marked ``tail`` is guaranteed to occur if
+ the following conditions are met:
+
+ - Caller and callee both have the calling convention ``fastcc``.
+ - The call is in tail position (ret immediately follows call and ret
+ uses value of call or is void).
+ - Option ``-tailcallopt`` is enabled, or
+ ``llvm::GuaranteedTailCallOpt`` is ``true``.
+ - `Platform-specific constraints are
+ met. <CodeGenerator.html#tailcallopt>`_
+
+#. The optional "cconv" marker indicates which :ref:`calling
+ convention <callingconv>` the call should use. If none is
+ specified, the call defaults to using C calling conventions. The
+ calling convention of the call must match the calling convention of
+ the target function, or else the behavior is undefined.
+#. The optional :ref:`Parameter Attributes <paramattrs>` list for return
+ values. Only '``zeroext``', '``signext``', and '``inreg``' attributes
+ are valid here.
+#. '``ty``': the type of the call instruction itself which is also the
+ type of the return value. Functions that return no value are marked
+ ``void``.
+#. '``fnty``': shall be the signature of the pointer to function value
+ being invoked. The argument types must match the types implied by
+ this signature. This type can be omitted if the function is not
+ varargs and if the function type does not return a pointer to a
+ function.
+#. '``fnptrval``': An LLVM value containing a pointer to a function to
+ be invoked. In most cases, this is a direct function invocation, but
+ indirect ``call``'s are just as possible, calling an arbitrary pointer
+ to function value.
+#. '``function args``': argument list whose types match the function
+ signature argument types and parameter attributes. All arguments must
+ be of :ref:`first class <t_firstclass>` type. If the function signature
+ indicates the function accepts a variable number of arguments, the
+ extra arguments can be specified.
+#. The optional :ref:`function attributes <fnattrs>` list. Only
+ '``noreturn``', '``nounwind``', '``readonly``' and '``readnone``'
+ attributes are valid here.
+
+Semantics:
+""""""""""
+
+The '``call``' instruction is used to cause control flow to transfer to
+a specified function, with its incoming arguments bound to the specified
+values. Upon a '``ret``' instruction in the called function, control
+flow continues with the instruction after the function call, and the
+return value of the function is bound to the result argument.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ %retval = call i32 @test(i32 %argc)
+ call i32 (i8*, ...)* @printf(i8* %msg, i32 12, i8 42) ; yields i32
+ %X = tail call i32 @foo() ; yields i32
+ %Y = tail call fastcc i32 @foo() ; yields i32
+ call void %foo(i8 97 signext)
+
+ %struct.A = type { i32, i8 }
+ %r = call %struct.A @foo() ; yields { i32, i8 }
+ %gr = extractvalue %struct.A %r, 0 ; yields i32
+ %gr1 = extractvalue %struct.A %r, 1 ; yields i8
+ %Z = call void @foo() noreturn ; indicates that %foo never returns normally
+ %ZZ = call zeroext i32 @bar() ; Return value is %zero extended
+
+llvm treats calls to some functions with names and arguments that match
+the standard C99 library as being the C99 library functions, and may
+perform optimizations or generate code for them under that assumption.
+This is something we'd like to change in the future to provide better
+support for freestanding environments and non-C-based languages.
+
+.. _i_va_arg:
+
+'``va_arg``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <resultval> = va_arg <va_list*> <arglist>, <argty>
+
+Overview:
+"""""""""
+
+The '``va_arg``' instruction is used to access arguments passed through
+the "variable argument" area of a function call. It is used to implement
+the ``va_arg`` macro in C.
+
+Arguments:
+""""""""""
+
+This instruction takes a ``va_list*`` value and the type of the
+argument. It returns a value of the specified argument type and
+increments the ``va_list`` to point to the next argument. The actual
+type of ``va_list`` is target specific.
+
+Semantics:
+""""""""""
+
+The '``va_arg``' instruction loads an argument of the specified type
+from the specified ``va_list`` and causes the ``va_list`` to point to
+the next argument. For more information, see the variable argument
+handling :ref:`Intrinsic Functions <int_varargs>`.
+
+It is legal for this instruction to be called in a function which does
+not take a variable number of arguments, for example, the ``vfprintf``
+function.
+
+``va_arg`` is an LLVM instruction instead of an :ref:`intrinsic
+function <intrinsics>` because it takes a type as an argument.
+
+Example:
+""""""""
+
+See the :ref:`variable argument processing <int_varargs>` section.
+
+Note that the code generator does not yet fully support va\_arg on many
+targets. Also, it does not currently support va\_arg with aggregate
+types on any target.
+
+.. _i_landingpad:
+
+'``landingpad``' Instruction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ <resultval> = landingpad <resultty> personality <type> <pers_fn> <clause>+
+ <resultval> = landingpad <resultty> personality <type> <pers_fn> cleanup <clause>*
+
+ <clause> := catch <type> <value>
+ <clause> := filter <array constant type> <array constant>
+
+Overview:
+"""""""""
+
+The '``landingpad``' instruction is used by `LLVM's exception handling
+system <ExceptionHandling.html#overview>`_ to specify that a basic block
+is a landing pad --- one where the exception lands, and corresponds to the
+code found in the ``catch`` portion of a ``try``/``catch`` sequence. It
+defines values supplied by the personality function (``pers_fn``) upon
+re-entry to the function. The ``resultval`` has the type ``resultty``.
+
+Arguments:
+""""""""""
+
+This instruction takes a ``pers_fn`` value. This is the personality
+function associated with the unwinding mechanism. The optional
+``cleanup`` flag indicates that the landing pad block is a cleanup.
+
+A ``clause`` begins with the clause type --- ``catch`` or ``filter`` --- and
+contains the global variable representing the "type" that may be caught
+or filtered respectively. Unlike the ``catch`` clause, the ``filter``
+clause takes an array constant as its argument. Use
+"``[0 x i8**] undef``" for a filter which cannot throw. The
+'``landingpad``' instruction must contain *at least* one ``clause`` or
+the ``cleanup`` flag.
+
+Semantics:
+""""""""""
+
+The '``landingpad``' instruction defines the values which are set by the
+personality function (``pers_fn``) upon re-entry to the function, and
+therefore the "result type" of the ``landingpad`` instruction. As with
+calling conventions, how the personality function results are
+represented in LLVM IR is target specific.
+
+The clauses are applied in order from top to bottom. If two
+``landingpad`` instructions are merged together through inlining, the
+clauses from the calling function are appended to the list of clauses.
+When the call stack is being unwound due to an exception being thrown,
+the exception is compared against each ``clause`` in turn. If it doesn't
+match any of the clauses, and the ``cleanup`` flag is not set, then
+unwinding continues further up the call stack.
+
+The ``landingpad`` instruction has several restrictions:
+
+- A landing pad block is a basic block which is the unwind destination
+ of an '``invoke``' instruction.
+- A landing pad block must have a '``landingpad``' instruction as its
+ first non-PHI instruction.
+- There can be only one '``landingpad``' instruction within the landing
+ pad block.
+- A basic block that is not a landing pad block may not include a
+ '``landingpad``' instruction.
+- All '``landingpad``' instructions in a function must have the same
+ personality function.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+ ;; A landing pad which can catch an integer.
+ %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
+ catch i8** @_ZTIi
+ ;; A landing pad that is a cleanup.
+ %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
+ cleanup
+ ;; A landing pad which can catch an integer and can only throw a double.
+ %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0
+ catch i8** @_ZTIi
+ filter [1 x i8**] [@_ZTId]
+
+.. _intrinsics:
+
+Intrinsic Functions
+===================
+
+LLVM supports the notion of an "intrinsic function". These functions
+have well known names and semantics and are required to follow certain
+restrictions. Overall, these intrinsics represent an extension mechanism
+for the LLVM language that does not require changing all of the
+transformations in LLVM when adding to the language (or the bitcode
+reader/writer, the parser, etc...).
+
+Intrinsic function names must all start with an "``llvm.``" prefix. This
+prefix is reserved in LLVM for intrinsic names; thus, function names may
+not begin with this prefix. Intrinsic functions must always be external
+functions: you cannot define the body of intrinsic functions. Intrinsic
+functions may only be used in call or invoke instructions: it is illegal
+to take the address of an intrinsic function. Additionally, because
+intrinsic functions are part of the LLVM language, it is required if any
+are added that they be documented here.
+
+Some intrinsic functions can be overloaded, i.e., the intrinsic
+represents a family of functions that perform the same operation but on
+different data types. Because LLVM can represent over 8 million
+different integer types, overloading is used commonly to allow an
+intrinsic function to operate on any integer type. One or more of the
+argument types or the result type can be overloaded to accept any
+integer type. Argument types may also be defined as exactly matching a
+previous argument's type or the result type. This allows an intrinsic
+function which accepts multiple arguments, but needs all of them to be
+of the same type, to only be overloaded with respect to a single
+argument or the result.
+
+Overloaded intrinsics will have the names of its overloaded argument
+types encoded into its function name, each preceded by a period. Only
+those types which are overloaded result in a name suffix. Arguments
+whose type is matched against another type do not. For example, the
+``llvm.ctpop`` function can take an integer of any width and returns an
+integer of exactly the same integer width. This leads to a family of
+functions such as ``i8 @llvm.ctpop.i8(i8 %val)`` and
+``i29 @llvm.ctpop.i29(i29 %val)``. Only one type, the return type, is
+overloaded, and only one type suffix is required. Because the argument's
+type is matched against the return type, it does not require its own
+name suffix.
+
+To learn how to add an intrinsic function, please see the `Extending
+LLVM Guide <ExtendingLLVM.html>`_.
+
+.. _int_varargs:
+
+Variable Argument Handling Intrinsics
+-------------------------------------
+
+Variable argument support is defined in LLVM with the
+:ref:`va_arg <i_va_arg>` instruction and these three intrinsic
+functions. These functions are related to the similarly named macros
+defined in the ``<stdarg.h>`` header file.
+
+All of these functions operate on arguments that use a target-specific
+value type "``va_list``". The LLVM assembly language reference manual
+does not define what this type is, so all transformations should be
+prepared to handle these functions regardless of the type used.
+
+This example shows how the :ref:`va_arg <i_va_arg>` instruction and the
+variable argument handling intrinsic functions are used.
+
+.. code-block:: llvm
+
+ ; This struct is different for every platform. For most platforms,
+ ; it is merely an i8*.
+ %struct.va_list = type { i8* }
+
+ ; For Unix x86_64 platforms, va_list is the following struct:
+ ; %struct.va_list = type { i32, i32, i8*, i8* }
+
+ define i32 @test(i32 %X, ...) {
+ ; Initialize variable argument processing
+ %ap = alloca %struct.va_list
+ %ap2 = bitcast %struct.va_list* %ap to i8*
+ call void @llvm.va_start(i8* %ap2)
+
+ ; Read a single integer argument
+ %tmp = va_arg i8* %ap2, i32
+
+ ; Demonstrate usage of llvm.va_copy and llvm.va_end
+ %aq = alloca i8*
+ %aq2 = bitcast i8** %aq to i8*
+ call void @llvm.va_copy(i8* %aq2, i8* %ap2)
+ call void @llvm.va_end(i8* %aq2)
+
+ ; Stop processing of arguments.
+ call void @llvm.va_end(i8* %ap2)
+ ret i32 %tmp
+ }
+
+ declare void @llvm.va_start(i8*)
+ declare void @llvm.va_copy(i8*, i8*)
+ declare void @llvm.va_end(i8*)
+
+.. _int_va_start:
+
+'``llvm.va_start``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.va_start(i8* <arglist>)
+
+Overview:
+"""""""""
+
+The '``llvm.va_start``' intrinsic initializes ``*<arglist>`` for
+subsequent use by ``va_arg``.
+
+Arguments:
+""""""""""
+
+The argument is a pointer to a ``va_list`` element to initialize.
+
+Semantics:
+""""""""""
+
+The '``llvm.va_start``' intrinsic works just like the ``va_start`` macro
+available in C. In a target-dependent way, it initializes the
+``va_list`` element to which the argument points, so that the next call
+to ``va_arg`` will produce the first variable argument passed to the
+function. Unlike the C ``va_start`` macro, this intrinsic does not need
+to know the last argument of the function as the compiler can figure
+that out.
+
+'``llvm.va_end``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.va_end(i8* <arglist>)
+
+Overview:
+"""""""""
+
+The '``llvm.va_end``' intrinsic destroys ``*<arglist>``, which has been
+initialized previously with ``llvm.va_start`` or ``llvm.va_copy``.
+
+Arguments:
+""""""""""
+
+The argument is a pointer to a ``va_list`` to destroy.
+
+Semantics:
+""""""""""
+
+The '``llvm.va_end``' intrinsic works just like the ``va_end`` macro
+available in C. In a target-dependent way, it destroys the ``va_list``
+element to which the argument points. Calls to
+:ref:`llvm.va_start <int_va_start>` and
+:ref:`llvm.va_copy <int_va_copy>` must be matched exactly with calls to
+``llvm.va_end``.
+
+.. _int_va_copy:
+
+'``llvm.va_copy``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>)
+
+Overview:
+"""""""""
+
+The '``llvm.va_copy``' intrinsic copies the current argument position
+from the source argument list to the destination argument list.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to a ``va_list`` element to initialize.
+The second argument is a pointer to a ``va_list`` element to copy from.
+
+Semantics:
+""""""""""
+
+The '``llvm.va_copy``' intrinsic works just like the ``va_copy`` macro
+available in C. In a target-dependent way, it copies the source
+``va_list`` element into the destination ``va_list`` element. This
+intrinsic is necessary because the `` llvm.va_start`` intrinsic may be
+arbitrarily complex and require, for example, memory allocation.
+
+Accurate Garbage Collection Intrinsics
+--------------------------------------
+
+LLVM support for `Accurate Garbage Collection <GarbageCollection.html>`_
+(GC) requires the implementation and generation of these intrinsics.
+These intrinsics allow identification of :ref:`GC roots on the
+stack <int_gcroot>`, as well as garbage collector implementations that
+require :ref:`read <int_gcread>` and :ref:`write <int_gcwrite>` barriers.
+Front-ends for type-safe garbage collected languages should generate
+these intrinsics to make use of the LLVM garbage collectors. For more
+details, see `Accurate Garbage Collection with
+LLVM <GarbageCollection.html>`_.
+
+The garbage collection intrinsics only operate on objects in the generic
+address space (address space zero).
+
+.. _int_gcroot:
+
+'``llvm.gcroot``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata)
+
+Overview:
+"""""""""
+
+The '``llvm.gcroot``' intrinsic declares the existence of a GC root to
+the code generator, and allows some metadata to be associated with it.
+
+Arguments:
+""""""""""
+
+The first argument specifies the address of a stack object that contains
+the root pointer. The second pointer (which must be either a constant or
+a global value address) contains the meta-data to be associated with the
+root.
+
+Semantics:
+""""""""""
+
+At runtime, a call to this intrinsic stores a null pointer into the
+"ptrloc" location. At compile-time, the code generator generates
+information to allow the runtime to find the pointer at GC safe points.
+The '``llvm.gcroot``' intrinsic may only be used in a function which
+:ref:`specifies a GC algorithm <gc>`.
+
+.. _int_gcread:
+
+'``llvm.gcread``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr)
+
+Overview:
+"""""""""
+
+The '``llvm.gcread``' intrinsic identifies reads of references from heap
+locations, allowing garbage collector implementations that require read
+barriers.
+
+Arguments:
+""""""""""
+
+The second argument is the address to read from, which should be an
+address allocated from the garbage collector. The first object is a
+pointer to the start of the referenced object, if needed by the language
+runtime (otherwise null).
+
+Semantics:
+""""""""""
+
+The '``llvm.gcread``' intrinsic has the same semantics as a load
+instruction, but may be replaced with substantially more complex code by
+the garbage collector runtime, as needed. The '``llvm.gcread``'
+intrinsic may only be used in a function which :ref:`specifies a GC
+algorithm <gc>`.
+
+.. _int_gcwrite:
+
+'``llvm.gcwrite``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2)
+
+Overview:
+"""""""""
+
+The '``llvm.gcwrite``' intrinsic identifies writes of references to heap
+locations, allowing garbage collector implementations that require write
+barriers (such as generational or reference counting collectors).
+
+Arguments:
+""""""""""
+
+The first argument is the reference to store, the second is the start of
+the object to store it to, and the third is the address of the field of
+Obj to store to. If the runtime does not require a pointer to the
+object, Obj may be null.
+
+Semantics:
+""""""""""
+
+The '``llvm.gcwrite``' intrinsic has the same semantics as a store
+instruction, but may be replaced with substantially more complex code by
+the garbage collector runtime, as needed. The '``llvm.gcwrite``'
+intrinsic may only be used in a function which :ref:`specifies a GC
+algorithm <gc>`.
+
+Code Generator Intrinsics
+-------------------------
+
+These intrinsics are provided by LLVM to expose special features that
+may only be implemented with code generator support.
+
+'``llvm.returnaddress``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i8 *@llvm.returnaddress(i32 <level>)
+
+Overview:
+"""""""""
+
+The '``llvm.returnaddress``' intrinsic attempts to compute a
+target-specific value indicating the return address of the current
+function or one of its callers.
+
+Arguments:
+""""""""""
+
+The argument to this intrinsic indicates which function to return the
+address for. Zero indicates the calling function, one indicates its
+caller, etc. The argument is **required** to be a constant integer
+value.
+
+Semantics:
+""""""""""
+
+The '``llvm.returnaddress``' intrinsic either returns a pointer
+indicating the return address of the specified call frame, or zero if it
+cannot be identified. The value returned by this intrinsic is likely to
+be incorrect or 0 for arguments other than zero, so it should only be
+used for debugging purposes.
+
+Note that calling this intrinsic does not prevent function inlining or
+other aggressive transformations, so the value returned may not be that
+of the obvious source-language caller.
+
+'``llvm.frameaddress``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i8* @llvm.frameaddress(i32 <level>)
+
+Overview:
+"""""""""
+
+The '``llvm.frameaddress``' intrinsic attempts to return the
+target-specific frame pointer value for the specified stack frame.
+
+Arguments:
+""""""""""
+
+The argument to this intrinsic indicates which function to return the
+frame pointer for. Zero indicates the calling function, one indicates
+its caller, etc. The argument is **required** to be a constant integer
+value.
+
+Semantics:
+""""""""""
+
+The '``llvm.frameaddress``' intrinsic either returns a pointer
+indicating the frame address of the specified call frame, or zero if it
+cannot be identified. The value returned by this intrinsic is likely to
+be incorrect or 0 for arguments other than zero, so it should only be
+used for debugging purposes.
+
+Note that calling this intrinsic does not prevent function inlining or
+other aggressive transformations, so the value returned may not be that
+of the obvious source-language caller.
+
+'``llvm.frameallocate``' and '``llvm.framerecover``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i8* @llvm.frameallocate(i32 %size)
+ declare i8* @llvm.framerecover(i8* %func, i8* %fp)
+
+Overview:
+"""""""""
+
+The '``llvm.frameallocate``' intrinsic allocates stack memory at some fixed
+offset from the frame pointer, and the '``llvm.framerecover``'
+intrinsic applies that offset to a live frame pointer to recover the address of
+the allocation. The offset is computed during frame layout of the caller of
+``llvm.frameallocate``.
+
+Arguments:
+""""""""""
+
+The ``size`` argument to '``llvm.frameallocate``' must be a constant integer
+indicating the amount of stack memory to allocate. As with allocas, allocating
+zero bytes is legal, but the result is undefined.
+
+The ``func`` argument to '``llvm.framerecover``' must be a constant
+bitcasted pointer to a function defined in the current module. The code
+generator cannot determine the frame allocation offset of functions defined in
+other modules.
+
+The ``fp`` argument to '``llvm.framerecover``' must be a frame
+pointer of a call frame that is currently live. The return value of
+'``llvm.frameaddress``' is one way to produce such a value, but most platforms
+also expose the frame pointer through stack unwinding mechanisms.
+
+Semantics:
+""""""""""
+
+These intrinsics allow a group of functions to access one stack memory
+allocation in an ancestor stack frame. The memory returned from
+'``llvm.frameallocate``' may be allocated prior to stack realignment, so the
+memory is only aligned to the ABI-required stack alignment. Each function may
+only call '``llvm.frameallocate``' one or zero times from the function entry
+block. The frame allocation intrinsic inhibits inlining, as any frame
+allocations in the inlined function frame are likely to be at a different
+offset from the one used by '``llvm.framerecover``' called with the
+uninlined function.
+
+.. _int_read_register:
+.. _int_write_register:
+
+'``llvm.read_register``' and '``llvm.write_register``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i32 @llvm.read_register.i32(metadata)
+ declare i64 @llvm.read_register.i64(metadata)
+ declare void @llvm.write_register.i32(metadata, i32 @value)
+ declare void @llvm.write_register.i64(metadata, i64 @value)
+ !0 = !{!"sp\00"}
+
+Overview:
+"""""""""
+
+The '``llvm.read_register``' and '``llvm.write_register``' intrinsics
+provides access to the named register. The register must be valid on
+the architecture being compiled to. The type needs to be compatible
+with the register being read.
+
+Semantics:
+""""""""""
+
+The '``llvm.read_register``' intrinsic returns the current value of the
+register, where possible. The '``llvm.write_register``' intrinsic sets
+the current value of the register, where possible.
+
+This is useful to implement named register global variables that need
+to always be mapped to a specific register, as is common practice on
+bare-metal programs including OS kernels.
+
+The compiler doesn't check for register availability or use of the used
+register in surrounding code, including inline assembly. Because of that,
+allocatable registers are not supported.
+
+Warning: So far it only works with the stack pointer on selected
+architectures (ARM, AArch64, PowerPC and x86_64). Significant amount of
+work is needed to support other registers and even more so, allocatable
+registers.
+
+.. _int_stacksave:
+
+'``llvm.stacksave``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i8* @llvm.stacksave()
+
+Overview:
+"""""""""
+
+The '``llvm.stacksave``' intrinsic is used to remember the current state
+of the function stack, for use with
+:ref:`llvm.stackrestore <int_stackrestore>`. This is useful for
+implementing language features like scoped automatic variable sized
+arrays in C99.
+
+Semantics:
+""""""""""
+
+This intrinsic returns a opaque pointer value that can be passed to
+:ref:`llvm.stackrestore <int_stackrestore>`. When an
+``llvm.stackrestore`` intrinsic is executed with a value saved from
+``llvm.stacksave``, it effectively restores the state of the stack to
+the state it was in when the ``llvm.stacksave`` intrinsic executed. In
+practice, this pops any :ref:`alloca <i_alloca>` blocks from the stack that
+were allocated after the ``llvm.stacksave`` was executed.
+
+.. _int_stackrestore:
+
+'``llvm.stackrestore``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.stackrestore(i8* %ptr)
+
+Overview:
+"""""""""
+
+The '``llvm.stackrestore``' intrinsic is used to restore the state of
+the function stack to the state it was in when the corresponding
+:ref:`llvm.stacksave <int_stacksave>` intrinsic executed. This is
+useful for implementing language features like scoped automatic variable
+sized arrays in C99.
+
+Semantics:
+""""""""""
+
+See the description for :ref:`llvm.stacksave <int_stacksave>`.
+
+'``llvm.prefetch``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>, i32 <cache type>)
+
+Overview:
+"""""""""
+
+The '``llvm.prefetch``' intrinsic is a hint to the code generator to
+insert a prefetch instruction if supported; otherwise, it is a noop.
+Prefetches have no effect on the behavior of the program but can change
+its performance characteristics.
+
+Arguments:
+""""""""""
+
+``address`` is the address to be prefetched, ``rw`` is the specifier
+determining if the fetch should be for a read (0) or write (1), and
+``locality`` is a temporal locality specifier ranging from (0) - no
+locality, to (3) - extremely local keep in cache. The ``cache type``
+specifies whether the prefetch is performed on the data (1) or
+instruction (0) cache. The ``rw``, ``locality`` and ``cache type``
+arguments must be constant integers.
+
+Semantics:
+""""""""""
+
+This intrinsic does not modify the behavior of the program. In
+particular, prefetches cannot trap and do not produce a value. On
+targets that support this intrinsic, the prefetch can provide hints to
+the processor cache for better performance.
+
+'``llvm.pcmarker``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.pcmarker(i32 <id>)
+
+Overview:
+"""""""""
+
+The '``llvm.pcmarker``' intrinsic is a method to export a Program
+Counter (PC) in a region of code to simulators and other tools. The
+method is target specific, but it is expected that the marker will use
+exported symbols to transmit the PC of the marker. The marker makes no
+guarantees that it will remain with any specific instruction after
+optimizations. It is possible that the presence of a marker will inhibit
+optimizations. The intended use is to be inserted after optimizations to
+allow correlations of simulation runs.
+
+Arguments:
+""""""""""
+
+``id`` is a numerical id identifying the marker.
+
+Semantics:
+""""""""""
+
+This intrinsic does not modify the behavior of the program. Backends
+that do not support this intrinsic may ignore it.
+
+'``llvm.readcyclecounter``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i64 @llvm.readcyclecounter()
+
+Overview:
+"""""""""
+
+The '``llvm.readcyclecounter``' intrinsic provides access to the cycle
+counter register (or similar low latency, high accuracy clocks) on those
+targets that support it. On X86, it should map to RDTSC. On Alpha, it
+should map to RPCC. As the backing counters overflow quickly (on the
+order of 9 seconds on alpha), this should only be used for small
+timings.
+
+Semantics:
+""""""""""
+
+When directly supported, reading the cycle counter should not modify any
+memory. Implementations are allowed to either return a application
+specific value or a system wide value. On backends without support, this
+is lowered to a constant 0.
+
+Note that runtime support may be conditional on the privilege-level code is
+running at and the host platform.
+
+'``llvm.clear_cache``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.clear_cache(i8*, i8*)
+
+Overview:
+"""""""""
+
+The '``llvm.clear_cache``' intrinsic ensures visibility of modifications
+in the specified range to the execution unit of the processor. On
+targets with non-unified instruction and data cache, the implementation
+flushes the instruction cache.
+
+Semantics:
+""""""""""
+
+On platforms with coherent instruction and data caches (e.g. x86), this
+intrinsic is a nop. On platforms with non-coherent instruction and data
+cache (e.g. ARM, MIPS), the intrinsic is lowered either to appropriate
+instructions or a system call, if cache flushing requires special
+privileges.
+
+The default behavior is to emit a call to ``__clear_cache`` from the run
+time library.
+
+This instrinsic does *not* empty the instruction pipeline. Modifications
+of the current function are outside the scope of the intrinsic.
+
+'``llvm.instrprof_increment``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.instrprof_increment(i8* <name>, i64 <hash>,
+ i32 <num-counters>, i32 <index>)
+
+Overview:
+"""""""""
+
+The '``llvm.instrprof_increment``' intrinsic can be emitted by a
+frontend for use with instrumentation based profiling. These will be
+lowered by the ``-instrprof`` pass to generate execution counts of a
+program at runtime.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to a global variable containing the
+name of the entity being instrumented. This should generally be the
+(mangled) function name for a set of counters.
+
+The second argument is a hash value that can be used by the consumer
+of the profile data to detect changes to the instrumented source, and
+the third is the number of counters associated with ``name``. It is an
+error if ``hash`` or ``num-counters`` differ between two instances of
+``instrprof_increment`` that refer to the same name.
+
+The last argument refers to which of the counters for ``name`` should
+be incremented. It should be a value between 0 and ``num-counters``.
+
+Semantics:
+""""""""""
+
+This intrinsic represents an increment of a profiling counter. It will
+cause the ``-instrprof`` pass to generate the appropriate data
+structures and the code to increment the appropriate value, in a
+format that can be written out by a compiler runtime and consumed via
+the ``llvm-profdata`` tool.
+
+Standard C Library Intrinsics
+-----------------------------
+
+LLVM provides intrinsics for a few important standard C library
+functions. These intrinsics allow source-language front-ends to pass
+information about the alignment of the pointer arguments to the code
+generator, providing opportunity for more efficient code generation.
+
+.. _int_memcpy:
+
+'``llvm.memcpy``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.memcpy`` on any
+integer bit width and for different address spaces. Not all targets
+support all bit widths however.
+
+::
+
+ declare void @llvm.memcpy.p0i8.p0i8.i32(i8* <dest>, i8* <src>,
+ i32 <len>, i32 <align>, i1 <isvolatile>)
+ declare void @llvm.memcpy.p0i8.p0i8.i64(i8* <dest>, i8* <src>,
+ i64 <len>, i32 <align>, i1 <isvolatile>)
+
+Overview:
+"""""""""
+
+The '``llvm.memcpy.*``' intrinsics copy a block of memory from the
+source location to the destination location.
+
+Note that, unlike the standard libc function, the ``llvm.memcpy.*``
+intrinsics do not return a value, takes extra alignment/isvolatile
+arguments and the pointers can be in specified address spaces.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to the destination, the second is a
+pointer to the source. The third argument is an integer argument
+specifying the number of bytes to copy, the fourth argument is the
+alignment of the source and destination locations, and the fifth is a
+boolean indicating a volatile access.
+
+If the call to this intrinsic has an alignment value that is not 0 or 1,
+then the caller guarantees that both the source and destination pointers
+are aligned to that boundary.
+
+If the ``isvolatile`` parameter is ``true``, the ``llvm.memcpy`` call is
+a :ref:`volatile operation <volatile>`. The detailed access behavior is not
+very cleanly specified and it is unwise to depend on it.
+
+Semantics:
+""""""""""
+
+The '``llvm.memcpy.*``' intrinsics copy a block of memory from the
+source location to the destination location, which are not allowed to
+overlap. It copies "len" bytes of memory over. If the argument is known
+to be aligned to some boundary, this can be specified as the fourth
+argument, otherwise it should be set to 0 or 1 (both meaning no alignment).
+
+'``llvm.memmove``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use llvm.memmove on any integer
+bit width and for different address space. Not all targets support all
+bit widths however.
+
+::
+
+ declare void @llvm.memmove.p0i8.p0i8.i32(i8* <dest>, i8* <src>,
+ i32 <len>, i32 <align>, i1 <isvolatile>)
+ declare void @llvm.memmove.p0i8.p0i8.i64(i8* <dest>, i8* <src>,
+ i64 <len>, i32 <align>, i1 <isvolatile>)
+
+Overview:
+"""""""""
+
+The '``llvm.memmove.*``' intrinsics move a block of memory from the
+source location to the destination location. It is similar to the
+'``llvm.memcpy``' intrinsic but allows the two memory locations to
+overlap.
+
+Note that, unlike the standard libc function, the ``llvm.memmove.*``
+intrinsics do not return a value, takes extra alignment/isvolatile
+arguments and the pointers can be in specified address spaces.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to the destination, the second is a
+pointer to the source. The third argument is an integer argument
+specifying the number of bytes to copy, the fourth argument is the
+alignment of the source and destination locations, and the fifth is a
+boolean indicating a volatile access.
+
+If the call to this intrinsic has an alignment value that is not 0 or 1,
+then the caller guarantees that the source and destination pointers are
+aligned to that boundary.
+
+If the ``isvolatile`` parameter is ``true``, the ``llvm.memmove`` call
+is a :ref:`volatile operation <volatile>`. The detailed access behavior is
+not very cleanly specified and it is unwise to depend on it.
+
+Semantics:
+""""""""""
+
+The '``llvm.memmove.*``' intrinsics copy a block of memory from the
+source location to the destination location, which may overlap. It
+copies "len" bytes of memory over. If the argument is known to be
+aligned to some boundary, this can be specified as the fourth argument,
+otherwise it should be set to 0 or 1 (both meaning no alignment).
+
+'``llvm.memset.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use llvm.memset on any integer
+bit width and for different address spaces. However, not all targets
+support all bit widths.
+
+::
+
+ declare void @llvm.memset.p0i8.i32(i8* <dest>, i8 <val>,
+ i32 <len>, i32 <align>, i1 <isvolatile>)
+ declare void @llvm.memset.p0i8.i64(i8* <dest>, i8 <val>,
+ i64 <len>, i32 <align>, i1 <isvolatile>)
+
+Overview:
+"""""""""
+
+The '``llvm.memset.*``' intrinsics fill a block of memory with a
+particular byte value.
+
+Note that, unlike the standard libc function, the ``llvm.memset``
+intrinsic does not return a value and takes extra alignment/volatile
+arguments. Also, the destination can be in an arbitrary address space.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to the destination to fill, the second
+is the byte value with which to fill it, the third argument is an
+integer argument specifying the number of bytes to fill, and the fourth
+argument is the known alignment of the destination location.
+
+If the call to this intrinsic has an alignment value that is not 0 or 1,
+then the caller guarantees that the destination pointer is aligned to
+that boundary.
+
+If the ``isvolatile`` parameter is ``true``, the ``llvm.memset`` call is
+a :ref:`volatile operation <volatile>`. The detailed access behavior is not
+very cleanly specified and it is unwise to depend on it.
+
+Semantics:
+""""""""""
+
+The '``llvm.memset.*``' intrinsics fill "len" bytes of memory starting
+at the destination location. If the argument is known to be aligned to
+some boundary, this can be specified as the fourth argument, otherwise
+it should be set to 0 or 1 (both meaning no alignment).
+
+'``llvm.sqrt.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.sqrt`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.sqrt.f32(float %Val)
+ declare double @llvm.sqrt.f64(double %Val)
+ declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val)
+ declare fp128 @llvm.sqrt.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.sqrt``' intrinsics return the sqrt of the specified operand,
+returning the same value as the libm '``sqrt``' functions would. Unlike
+``sqrt`` in libm, however, ``llvm.sqrt`` has undefined behavior for
+negative numbers other than -0.0 (which allows for better optimization,
+because there is no need to worry about errno being set).
+``llvm.sqrt(-0.0)`` is defined to return -0.0 like IEEE sqrt.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the sqrt of the specified operand if it is a
+nonnegative floating point number.
+
+'``llvm.powi.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.powi`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.powi.f32(float %Val, i32 %power)
+ declare double @llvm.powi.f64(double %Val, i32 %power)
+ declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power)
+ declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power)
+ declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power)
+
+Overview:
+"""""""""
+
+The '``llvm.powi.*``' intrinsics return the first operand raised to the
+specified (positive or negative) power. The order of evaluation of
+multiplications is not defined. When a vector of floating point type is
+used, the second argument remains a scalar integer value.
+
+Arguments:
+""""""""""
+
+The second argument is an integer power, and the first is a value to
+raise to that power.
+
+Semantics:
+""""""""""
+
+This function returns the first value raised to the second power with an
+unspecified sequence of rounding operations.
+
+'``llvm.sin.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.sin`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.sin.f32(float %Val)
+ declare double @llvm.sin.f64(double %Val)
+ declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val)
+ declare fp128 @llvm.sin.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.sin.*``' intrinsics return the sine of the operand.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the sine of the specified operand, returning the
+same values as the libm ``sin`` functions would, and handles error
+conditions in the same way.
+
+'``llvm.cos.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.cos`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.cos.f32(float %Val)
+ declare double @llvm.cos.f64(double %Val)
+ declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val)
+ declare fp128 @llvm.cos.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.cos.*``' intrinsics return the cosine of the operand.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the cosine of the specified operand, returning the
+same values as the libm ``cos`` functions would, and handles error
+conditions in the same way.
+
+'``llvm.pow.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.pow`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.pow.f32(float %Val, float %Power)
+ declare double @llvm.pow.f64(double %Val, double %Power)
+ declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power)
+ declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power)
+ declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power)
+
+Overview:
+"""""""""
+
+The '``llvm.pow.*``' intrinsics return the first operand raised to the
+specified (positive or negative) power.
+
+Arguments:
+""""""""""
+
+The second argument is a floating point power, and the first is a value
+to raise to that power.
+
+Semantics:
+""""""""""
+
+This function returns the first value raised to the second power,
+returning the same values as the libm ``pow`` functions would, and
+handles error conditions in the same way.
+
+'``llvm.exp.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.exp`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.exp.f32(float %Val)
+ declare double @llvm.exp.f64(double %Val)
+ declare x86_fp80 @llvm.exp.f80(x86_fp80 %Val)
+ declare fp128 @llvm.exp.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.exp.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.exp.*``' intrinsics perform the exp function.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``exp`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.exp2.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.exp2`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.exp2.f32(float %Val)
+ declare double @llvm.exp2.f64(double %Val)
+ declare x86_fp80 @llvm.exp2.f80(x86_fp80 %Val)
+ declare fp128 @llvm.exp2.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.exp2.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.exp2.*``' intrinsics perform the exp2 function.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``exp2`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.log.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.log`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.log.f32(float %Val)
+ declare double @llvm.log.f64(double %Val)
+ declare x86_fp80 @llvm.log.f80(x86_fp80 %Val)
+ declare fp128 @llvm.log.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.log.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.log.*``' intrinsics perform the log function.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``log`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.log10.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.log10`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.log10.f32(float %Val)
+ declare double @llvm.log10.f64(double %Val)
+ declare x86_fp80 @llvm.log10.f80(x86_fp80 %Val)
+ declare fp128 @llvm.log10.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.log10.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.log10.*``' intrinsics perform the log10 function.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``log10`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.log2.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.log2`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.log2.f32(float %Val)
+ declare double @llvm.log2.f64(double %Val)
+ declare x86_fp80 @llvm.log2.f80(x86_fp80 %Val)
+ declare fp128 @llvm.log2.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.log2.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.log2.*``' intrinsics perform the log2 function.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``log2`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.fma.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.fma`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.fma.f32(float %a, float %b, float %c)
+ declare double @llvm.fma.f64(double %a, double %b, double %c)
+ declare x86_fp80 @llvm.fma.f80(x86_fp80 %a, x86_fp80 %b, x86_fp80 %c)
+ declare fp128 @llvm.fma.f128(fp128 %a, fp128 %b, fp128 %c)
+ declare ppc_fp128 @llvm.fma.ppcf128(ppc_fp128 %a, ppc_fp128 %b, ppc_fp128 %c)
+
+Overview:
+"""""""""
+
+The '``llvm.fma.*``' intrinsics perform the fused multiply-add
+operation.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``fma`` functions
+would, and does not set errno.
+
+'``llvm.fabs.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.fabs`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.fabs.f32(float %Val)
+ declare double @llvm.fabs.f64(double %Val)
+ declare x86_fp80 @llvm.fabs.f80(x86_fp80 %Val)
+ declare fp128 @llvm.fabs.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.fabs.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.fabs.*``' intrinsics return the absolute value of the
+operand.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``fabs`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.minnum.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.minnum`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.minnum.f32(float %Val0, float %Val1)
+ declare double @llvm.minnum.f64(double %Val0, double %Val1)
+ declare x86_fp80 @llvm.minnum.f80(x86_fp80 %Val0, x86_fp80 %Val1)
+ declare fp128 @llvm.minnum.f128(fp128 %Val0, fp128 %Val1)
+ declare ppc_fp128 @llvm.minnum.ppcf128(ppc_fp128 %Val0, ppc_fp128 %Val1)
+
+Overview:
+"""""""""
+
+The '``llvm.minnum.*``' intrinsics return the minimum of the two
+arguments.
+
+
+Arguments:
+""""""""""
+
+The arguments and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+Follows the IEEE-754 semantics for minNum, which also match for libm's
+fmin.
+
+If either operand is a NaN, returns the other non-NaN operand. Returns
+NaN only if both operands are NaN. If the operands compare equal,
+returns a value that compares equal to both operands. This means that
+fmin(+/-0.0, +/-0.0) could return either -0.0 or 0.0.
+
+'``llvm.maxnum.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.maxnum`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.maxnum.f32(float %Val0, float %Val1l)
+ declare double @llvm.maxnum.f64(double %Val0, double %Val1)
+ declare x86_fp80 @llvm.maxnum.f80(x86_fp80 %Val0, x86_fp80 %Val1)
+ declare fp128 @llvm.maxnum.f128(fp128 %Val0, fp128 %Val1)
+ declare ppc_fp128 @llvm.maxnum.ppcf128(ppc_fp128 %Val0, ppc_fp128 %Val1)
+
+Overview:
+"""""""""
+
+The '``llvm.maxnum.*``' intrinsics return the maximum of the two
+arguments.
+
+
+Arguments:
+""""""""""
+
+The arguments and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+Follows the IEEE-754 semantics for maxNum, which also match for libm's
+fmax.
+
+If either operand is a NaN, returns the other non-NaN operand. Returns
+NaN only if both operands are NaN. If the operands compare equal,
+returns a value that compares equal to both operands. This means that
+fmax(+/-0.0, +/-0.0) could return either -0.0 or 0.0.
+
+'``llvm.copysign.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.copysign`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.copysign.f32(float %Mag, float %Sgn)
+ declare double @llvm.copysign.f64(double %Mag, double %Sgn)
+ declare x86_fp80 @llvm.copysign.f80(x86_fp80 %Mag, x86_fp80 %Sgn)
+ declare fp128 @llvm.copysign.f128(fp128 %Mag, fp128 %Sgn)
+ declare ppc_fp128 @llvm.copysign.ppcf128(ppc_fp128 %Mag, ppc_fp128 %Sgn)
+
+Overview:
+"""""""""
+
+The '``llvm.copysign.*``' intrinsics return a value with the magnitude of the
+first operand and the sign of the second operand.
+
+Arguments:
+""""""""""
+
+The arguments and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``copysign``
+functions would, and handles error conditions in the same way.
+
+'``llvm.floor.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.floor`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.floor.f32(float %Val)
+ declare double @llvm.floor.f64(double %Val)
+ declare x86_fp80 @llvm.floor.f80(x86_fp80 %Val)
+ declare fp128 @llvm.floor.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.floor.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.floor.*``' intrinsics return the floor of the operand.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``floor`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.ceil.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.ceil`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.ceil.f32(float %Val)
+ declare double @llvm.ceil.f64(double %Val)
+ declare x86_fp80 @llvm.ceil.f80(x86_fp80 %Val)
+ declare fp128 @llvm.ceil.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.ceil.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.ceil.*``' intrinsics return the ceiling of the operand.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``ceil`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.trunc.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.trunc`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.trunc.f32(float %Val)
+ declare double @llvm.trunc.f64(double %Val)
+ declare x86_fp80 @llvm.trunc.f80(x86_fp80 %Val)
+ declare fp128 @llvm.trunc.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.trunc.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.trunc.*``' intrinsics returns the operand rounded to the
+nearest integer not larger in magnitude than the operand.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``trunc`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.rint.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.rint`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.rint.f32(float %Val)
+ declare double @llvm.rint.f64(double %Val)
+ declare x86_fp80 @llvm.rint.f80(x86_fp80 %Val)
+ declare fp128 @llvm.rint.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.rint.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.rint.*``' intrinsics returns the operand rounded to the
+nearest integer. It may raise an inexact floating-point exception if the
+operand isn't an integer.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``rint`` functions
+would, and handles error conditions in the same way.
+
+'``llvm.nearbyint.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.nearbyint`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.nearbyint.f32(float %Val)
+ declare double @llvm.nearbyint.f64(double %Val)
+ declare x86_fp80 @llvm.nearbyint.f80(x86_fp80 %Val)
+ declare fp128 @llvm.nearbyint.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.nearbyint.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.nearbyint.*``' intrinsics returns the operand rounded to the
+nearest integer.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``nearbyint``
+functions would, and handles error conditions in the same way.
+
+'``llvm.round.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.round`` on any
+floating point or vector of floating point type. Not all targets support
+all types however.
+
+::
+
+ declare float @llvm.round.f32(float %Val)
+ declare double @llvm.round.f64(double %Val)
+ declare x86_fp80 @llvm.round.f80(x86_fp80 %Val)
+ declare fp128 @llvm.round.f128(fp128 %Val)
+ declare ppc_fp128 @llvm.round.ppcf128(ppc_fp128 %Val)
+
+Overview:
+"""""""""
+
+The '``llvm.round.*``' intrinsics returns the operand rounded to the
+nearest integer.
+
+Arguments:
+""""""""""
+
+The argument and return value are floating point numbers of the same
+type.
+
+Semantics:
+""""""""""
+
+This function returns the same values as the libm ``round``
+functions would, and handles error conditions in the same way.
+
+Bit Manipulation Intrinsics
+---------------------------
+
+LLVM provides intrinsics for a few important bit manipulation
+operations. These allow efficient code generation for some algorithms.
+
+'``llvm.bswap.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic function. You can use bswap on any
+integer type that is an even number of bytes (i.e. BitWidth % 16 == 0).
+
+::
+
+ declare i16 @llvm.bswap.i16(i16 <id>)
+ declare i32 @llvm.bswap.i32(i32 <id>)
+ declare i64 @llvm.bswap.i64(i64 <id>)
+
+Overview:
+"""""""""
+
+The '``llvm.bswap``' family of intrinsics is used to byte swap integer
+values with an even number of bytes (positive multiple of 16 bits).
+These are useful for performing operations on data that is not in the
+target's native byte order.
+
+Semantics:
+""""""""""
+
+The ``llvm.bswap.i16`` intrinsic returns an i16 value that has the high
+and low byte of the input i16 swapped. Similarly, the ``llvm.bswap.i32``
+intrinsic returns an i32 value that has the four bytes of the input i32
+swapped, so that if the input bytes are numbered 0, 1, 2, 3 then the
+returned i32 will have its bytes in 3, 2, 1, 0 order. The
+``llvm.bswap.i48``, ``llvm.bswap.i64`` and other intrinsics extend this
+concept to additional even-byte lengths (6 bytes, 8 bytes and more,
+respectively).
+
+'``llvm.ctpop.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use llvm.ctpop on any integer
+bit width, or on any vector with integer elements. Not all targets
+support all bit widths or vector types, however.
+
+::
+
+ declare i8 @llvm.ctpop.i8(i8 <src>)
+ declare i16 @llvm.ctpop.i16(i16 <src>)
+ declare i32 @llvm.ctpop.i32(i32 <src>)
+ declare i64 @llvm.ctpop.i64(i64 <src>)
+ declare i256 @llvm.ctpop.i256(i256 <src>)
+ declare <2 x i32> @llvm.ctpop.v2i32(<2 x i32> <src>)
+
+Overview:
+"""""""""
+
+The '``llvm.ctpop``' family of intrinsics counts the number of bits set
+in a value.
+
+Arguments:
+""""""""""
+
+The only argument is the value to be counted. The argument may be of any
+integer type, or a vector with integer elements. The return type must
+match the argument type.
+
+Semantics:
+""""""""""
+
+The '``llvm.ctpop``' intrinsic counts the 1's in a variable, or within
+each element of a vector.
+
+'``llvm.ctlz.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.ctlz`` on any
+integer bit width, or any vector whose elements are integers. Not all
+targets support all bit widths or vector types, however.
+
+::
+
+ declare i8 @llvm.ctlz.i8 (i8 <src>, i1 <is_zero_undef>)
+ declare i16 @llvm.ctlz.i16 (i16 <src>, i1 <is_zero_undef>)
+ declare i32 @llvm.ctlz.i32 (i32 <src>, i1 <is_zero_undef>)
+ declare i64 @llvm.ctlz.i64 (i64 <src>, i1 <is_zero_undef>)
+ declare i256 @llvm.ctlz.i256(i256 <src>, i1 <is_zero_undef>)
+ declase <2 x i32> @llvm.ctlz.v2i32(<2 x i32> <src>, i1 <is_zero_undef>)
+
+Overview:
+"""""""""
+
+The '``llvm.ctlz``' family of intrinsic functions counts the number of
+leading zeros in a variable.
+
+Arguments:
+""""""""""
+
+The first argument is the value to be counted. This argument may be of
+any integer type, or a vector with integer element type. The return
+type must match the first argument type.
+
+The second argument must be a constant and is a flag to indicate whether
+the intrinsic should ensure that a zero as the first argument produces a
+defined result. Historically some architectures did not provide a
+defined result for zero values as efficiently, and many algorithms are
+now predicated on avoiding zero-value inputs.
+
+Semantics:
+""""""""""
+
+The '``llvm.ctlz``' intrinsic counts the leading (most significant)
+zeros in a variable, or within each element of the vector. If
+``src == 0`` then the result is the size in bits of the type of ``src``
+if ``is_zero_undef == 0`` and ``undef`` otherwise. For example,
+``llvm.ctlz(i32 2) = 30``.
+
+'``llvm.cttz.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.cttz`` on any
+integer bit width, or any vector of integer elements. Not all targets
+support all bit widths or vector types, however.
+
+::
+
+ declare i8 @llvm.cttz.i8 (i8 <src>, i1 <is_zero_undef>)
+ declare i16 @llvm.cttz.i16 (i16 <src>, i1 <is_zero_undef>)
+ declare i32 @llvm.cttz.i32 (i32 <src>, i1 <is_zero_undef>)
+ declare i64 @llvm.cttz.i64 (i64 <src>, i1 <is_zero_undef>)
+ declare i256 @llvm.cttz.i256(i256 <src>, i1 <is_zero_undef>)
+ declase <2 x i32> @llvm.cttz.v2i32(<2 x i32> <src>, i1 <is_zero_undef>)
+
+Overview:
+"""""""""
+
+The '``llvm.cttz``' family of intrinsic functions counts the number of
+trailing zeros.
+
+Arguments:
+""""""""""
+
+The first argument is the value to be counted. This argument may be of
+any integer type, or a vector with integer element type. The return
+type must match the first argument type.
+
+The second argument must be a constant and is a flag to indicate whether
+the intrinsic should ensure that a zero as the first argument produces a
+defined result. Historically some architectures did not provide a
+defined result for zero values as efficiently, and many algorithms are
+now predicated on avoiding zero-value inputs.
+
+Semantics:
+""""""""""
+
+The '``llvm.cttz``' intrinsic counts the trailing (least significant)
+zeros in a variable, or within each element of a vector. If ``src == 0``
+then the result is the size in bits of the type of ``src`` if
+``is_zero_undef == 0`` and ``undef`` otherwise. For example,
+``llvm.cttz(2) = 1``.
+
+Arithmetic with Overflow Intrinsics
+-----------------------------------
+
+LLVM provides intrinsics for some arithmetic with overflow operations.
+
+'``llvm.sadd.with.overflow.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.sadd.with.overflow``
+on any integer bit width.
+
+::
+
+ declare {i16, i1} @llvm.sadd.with.overflow.i16(i16 %a, i16 %b)
+ declare {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
+ declare {i64, i1} @llvm.sadd.with.overflow.i64(i64 %a, i64 %b)
+
+Overview:
+"""""""""
+
+The '``llvm.sadd.with.overflow``' family of intrinsic functions perform
+a signed addition of the two arguments, and indicate whether an overflow
+occurred during the signed summation.
+
+Arguments:
+""""""""""
+
+The arguments (%a and %b) and the first element of the result structure
+may be of integer types of any bit width, but they must have the same
+bit width. The second element of the result structure must be of type
+``i1``. ``%a`` and ``%b`` are the two values that will undergo signed
+addition.
+
+Semantics:
+""""""""""
+
+The '``llvm.sadd.with.overflow``' family of intrinsic functions perform
+a signed addition of the two variables. They return a structure --- the
+first element of which is the signed summation, and the second element
+of which is a bit specifying if the signed summation resulted in an
+overflow.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b)
+ %sum = extractvalue {i32, i1} %res, 0
+ %obit = extractvalue {i32, i1} %res, 1
+ br i1 %obit, label %overflow, label %normal
+
+'``llvm.uadd.with.overflow.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.uadd.with.overflow``
+on any integer bit width.
+
+::
+
+ declare {i16, i1} @llvm.uadd.with.overflow.i16(i16 %a, i16 %b)
+ declare {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
+ declare {i64, i1} @llvm.uadd.with.overflow.i64(i64 %a, i64 %b)
+
+Overview:
+"""""""""
+
+The '``llvm.uadd.with.overflow``' family of intrinsic functions perform
+an unsigned addition of the two arguments, and indicate whether a carry
+occurred during the unsigned summation.
+
+Arguments:
+""""""""""
+
+The arguments (%a and %b) and the first element of the result structure
+may be of integer types of any bit width, but they must have the same
+bit width. The second element of the result structure must be of type
+``i1``. ``%a`` and ``%b`` are the two values that will undergo unsigned
+addition.
+
+Semantics:
+""""""""""
+
+The '``llvm.uadd.with.overflow``' family of intrinsic functions perform
+an unsigned addition of the two arguments. They return a structure --- the
+first element of which is the sum, and the second element of which is a
+bit specifying if the unsigned summation resulted in a carry.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %res = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
+ %sum = extractvalue {i32, i1} %res, 0
+ %obit = extractvalue {i32, i1} %res, 1
+ br i1 %obit, label %carry, label %normal
+
+'``llvm.ssub.with.overflow.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.ssub.with.overflow``
+on any integer bit width.
+
+::
+
+ declare {i16, i1} @llvm.ssub.with.overflow.i16(i16 %a, i16 %b)
+ declare {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
+ declare {i64, i1} @llvm.ssub.with.overflow.i64(i64 %a, i64 %b)
+
+Overview:
+"""""""""
+
+The '``llvm.ssub.with.overflow``' family of intrinsic functions perform
+a signed subtraction of the two arguments, and indicate whether an
+overflow occurred during the signed subtraction.
+
+Arguments:
+""""""""""
+
+The arguments (%a and %b) and the first element of the result structure
+may be of integer types of any bit width, but they must have the same
+bit width. The second element of the result structure must be of type
+``i1``. ``%a`` and ``%b`` are the two values that will undergo signed
+subtraction.
+
+Semantics:
+""""""""""
+
+The '``llvm.ssub.with.overflow``' family of intrinsic functions perform
+a signed subtraction of the two arguments. They return a structure --- the
+first element of which is the subtraction, and the second element of
+which is a bit specifying if the signed subtraction resulted in an
+overflow.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %res = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b)
+ %sum = extractvalue {i32, i1} %res, 0
+ %obit = extractvalue {i32, i1} %res, 1
+ br i1 %obit, label %overflow, label %normal
+
+'``llvm.usub.with.overflow.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.usub.with.overflow``
+on any integer bit width.
+
+::
+
+ declare {i16, i1} @llvm.usub.with.overflow.i16(i16 %a, i16 %b)
+ declare {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
+ declare {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %b)
+
+Overview:
+"""""""""
+
+The '``llvm.usub.with.overflow``' family of intrinsic functions perform
+an unsigned subtraction of the two arguments, and indicate whether an
+overflow occurred during the unsigned subtraction.
+
+Arguments:
+""""""""""
+
+The arguments (%a and %b) and the first element of the result structure
+may be of integer types of any bit width, but they must have the same
+bit width. The second element of the result structure must be of type
+``i1``. ``%a`` and ``%b`` are the two values that will undergo unsigned
+subtraction.
+
+Semantics:
+""""""""""
+
+The '``llvm.usub.with.overflow``' family of intrinsic functions perform
+an unsigned subtraction of the two arguments. They return a structure ---
+the first element of which is the subtraction, and the second element of
+which is a bit specifying if the unsigned subtraction resulted in an
+overflow.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %res = call {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b)
+ %sum = extractvalue {i32, i1} %res, 0
+ %obit = extractvalue {i32, i1} %res, 1
+ br i1 %obit, label %overflow, label %normal
+
+'``llvm.smul.with.overflow.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.smul.with.overflow``
+on any integer bit width.
+
+::
+
+ declare {i16, i1} @llvm.smul.with.overflow.i16(i16 %a, i16 %b)
+ declare {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
+ declare {i64, i1} @llvm.smul.with.overflow.i64(i64 %a, i64 %b)
+
+Overview:
+"""""""""
+
+The '``llvm.smul.with.overflow``' family of intrinsic functions perform
+a signed multiplication of the two arguments, and indicate whether an
+overflow occurred during the signed multiplication.
+
+Arguments:
+""""""""""
+
+The arguments (%a and %b) and the first element of the result structure
+may be of integer types of any bit width, but they must have the same
+bit width. The second element of the result structure must be of type
+``i1``. ``%a`` and ``%b`` are the two values that will undergo signed
+multiplication.
+
+Semantics:
+""""""""""
+
+The '``llvm.smul.with.overflow``' family of intrinsic functions perform
+a signed multiplication of the two arguments. They return a structure ---
+the first element of which is the multiplication, and the second element
+of which is a bit specifying if the signed multiplication resulted in an
+overflow.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %res = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
+ %sum = extractvalue {i32, i1} %res, 0
+ %obit = extractvalue {i32, i1} %res, 1
+ br i1 %obit, label %overflow, label %normal
+
+'``llvm.umul.with.overflow.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.umul.with.overflow``
+on any integer bit width.
+
+::
+
+ declare {i16, i1} @llvm.umul.with.overflow.i16(i16 %a, i16 %b)
+ declare {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
+ declare {i64, i1} @llvm.umul.with.overflow.i64(i64 %a, i64 %b)
+
+Overview:
+"""""""""
+
+The '``llvm.umul.with.overflow``' family of intrinsic functions perform
+a unsigned multiplication of the two arguments, and indicate whether an
+overflow occurred during the unsigned multiplication.
+
+Arguments:
+""""""""""
+
+The arguments (%a and %b) and the first element of the result structure
+may be of integer types of any bit width, but they must have the same
+bit width. The second element of the result structure must be of type
+``i1``. ``%a`` and ``%b`` are the two values that will undergo unsigned
+multiplication.
+
+Semantics:
+""""""""""
+
+The '``llvm.umul.with.overflow``' family of intrinsic functions perform
+an unsigned multiplication of the two arguments. They return a structure ---
+the first element of which is the multiplication, and the second
+element of which is a bit specifying if the unsigned multiplication
+resulted in an overflow.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %res = call {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b)
+ %sum = extractvalue {i32, i1} %res, 0
+ %obit = extractvalue {i32, i1} %res, 1
+ br i1 %obit, label %overflow, label %normal
+
+Specialised Arithmetic Intrinsics
+---------------------------------
+
+'``llvm.fmuladd.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare float @llvm.fmuladd.f32(float %a, float %b, float %c)
+ declare double @llvm.fmuladd.f64(double %a, double %b, double %c)
+
+Overview:
+"""""""""
+
+The '``llvm.fmuladd.*``' intrinsic functions represent multiply-add
+expressions that can be fused if the code generator determines that (a) the
+target instruction set has support for a fused operation, and (b) that the
+fused operation is more efficient than the equivalent, separate pair of mul
+and add instructions.
+
+Arguments:
+""""""""""
+
+The '``llvm.fmuladd.*``' intrinsics each take three arguments: two
+multiplicands, a and b, and an addend c.
+
+Semantics:
+""""""""""
+
+The expression:
+
+::
+
+ %0 = call float @llvm.fmuladd.f32(%a, %b, %c)
+
+is equivalent to the expression a \* b + c, except that rounding will
+not be performed between the multiplication and addition steps if the
+code generator fuses the operations. Fusion is not guaranteed, even if
+the target platform supports it. If a fused multiply-add is required the
+corresponding llvm.fma.\* intrinsic function should be used
+instead. This never sets errno, just as '``llvm.fma.*``'.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %r2 = call float @llvm.fmuladd.f32(float %a, float %b, float %c) ; yields float:r2 = (a * b) + c
+
+Half Precision Floating Point Intrinsics
+----------------------------------------
+
+For most target platforms, half precision floating point is a
+storage-only format. This means that it is a dense encoding (in memory)
+but does not support computation in the format.
+
+This means that code must first load the half-precision floating point
+value as an i16, then convert it to float with
+:ref:`llvm.convert.from.fp16 <int_convert_from_fp16>`. Computation can
+then be performed on the float value (including extending to double
+etc). To store the value back to memory, it is first converted to float
+if needed, then converted to i16 with
+:ref:`llvm.convert.to.fp16 <int_convert_to_fp16>`, then storing as an
+i16 value.
+
+.. _int_convert_to_fp16:
+
+'``llvm.convert.to.fp16``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i16 @llvm.convert.to.fp16.f32(float %a)
+ declare i16 @llvm.convert.to.fp16.f64(double %a)
+
+Overview:
+"""""""""
+
+The '``llvm.convert.to.fp16``' intrinsic function performs a conversion from a
+conventional floating point type to half precision floating point format.
+
+Arguments:
+""""""""""
+
+The intrinsic function contains single argument - the value to be
+converted.
+
+Semantics:
+""""""""""
+
+The '``llvm.convert.to.fp16``' intrinsic function performs a conversion from a
+conventional floating point format to half precision floating point format. The
+return value is an ``i16`` which contains the converted number.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %res = call i16 @llvm.convert.to.fp16.f32(float %a)
+ store i16 %res, i16* @x, align 2
+
+.. _int_convert_from_fp16:
+
+'``llvm.convert.from.fp16``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare float @llvm.convert.from.fp16.f32(i16 %a)
+ declare double @llvm.convert.from.fp16.f64(i16 %a)
+
+Overview:
+"""""""""
+
+The '``llvm.convert.from.fp16``' intrinsic function performs a
+conversion from half precision floating point format to single precision
+floating point format.
+
+Arguments:
+""""""""""
+
+The intrinsic function contains single argument - the value to be
+converted.
+
+Semantics:
+""""""""""
+
+The '``llvm.convert.from.fp16``' intrinsic function performs a
+conversion from half single precision floating point format to single
+precision floating point format. The input half-float value is
+represented by an ``i16`` value.
+
+Examples:
+"""""""""
+
+.. code-block:: llvm
+
+ %a = load i16* @x, align 2
+ %res = call float @llvm.convert.from.fp16(i16 %a)
+
+Debugger Intrinsics
+-------------------
+
+The LLVM debugger intrinsics (which all start with ``llvm.dbg.``
+prefix), are described in the `LLVM Source Level
+Debugging <SourceLevelDebugging.html#format_common_intrinsics>`_
+document.
+
+Exception Handling Intrinsics
+-----------------------------
+
+The LLVM exception handling intrinsics (which all start with
+``llvm.eh.`` prefix), are described in the `LLVM Exception
+Handling <ExceptionHandling.html#format_common_intrinsics>`_ document.
+
+.. _int_trampoline:
+
+Trampoline Intrinsics
+---------------------
+
+These intrinsics make it possible to excise one parameter, marked with
+the :ref:`nest <nest>` attribute, from a function. The result is a
+callable function pointer lacking the nest parameter - the caller does
+not need to provide a value for it. Instead, the value to use is stored
+in advance in a "trampoline", a block of memory usually allocated on the
+stack, which also contains code to splice the nest value into the
+argument list. This is used to implement the GCC nested function address
+extension.
+
+For example, if the function is ``i32 f(i8* nest %c, i32 %x, i32 %y)``
+then the resulting function pointer has signature ``i32 (i32, i32)*``.
+It can be created as follows:
+
+.. code-block:: llvm
+
+ %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
+ %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
+ call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8*, i32, i32)* @f to i8*), i8* %nval)
+ %p = call i8* @llvm.adjust.trampoline(i8* %tramp1)
+ %fp = bitcast i8* %p to i32 (i32, i32)*
+
+The call ``%val = call i32 %fp(i32 %x, i32 %y)`` is then equivalent to
+``%val = call i32 %f(i8* %nval, i32 %x, i32 %y)``.
+
+.. _int_it:
+
+'``llvm.init.trampoline``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
+
+Overview:
+"""""""""
+
+This fills the memory pointed to by ``tramp`` with executable code,
+turning it into a trampoline.
+
+Arguments:
+""""""""""
+
+The ``llvm.init.trampoline`` intrinsic takes three arguments, all
+pointers. The ``tramp`` argument must point to a sufficiently large and
+sufficiently aligned block of memory; this memory is written to by the
+intrinsic. Note that the size and the alignment are target-specific -
+LLVM currently provides no portable way of determining them, so a
+front-end that generates this intrinsic needs to have some
+target-specific knowledge. The ``func`` argument must hold a function
+bitcast to an ``i8*``.
+
+Semantics:
+""""""""""
+
+The block of memory pointed to by ``tramp`` is filled with target
+dependent code, turning it into a function. Then ``tramp`` needs to be
+passed to :ref:`llvm.adjust.trampoline <int_at>` to get a pointer which can
+be :ref:`bitcast (to a new function) and called <int_trampoline>`. The new
+function's signature is the same as that of ``func`` with any arguments
+marked with the ``nest`` attribute removed. At most one such ``nest``
+argument is allowed, and it must be of pointer type. Calling the new
+function is equivalent to calling ``func`` with the same argument list,
+but with ``nval`` used for the missing ``nest`` argument. If, after
+calling ``llvm.init.trampoline``, the memory pointed to by ``tramp`` is
+modified, then the effect of any later call to the returned function
+pointer is undefined.
+
+.. _int_at:
+
+'``llvm.adjust.trampoline``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i8* @llvm.adjust.trampoline(i8* <tramp>)
+
+Overview:
+"""""""""
+
+This performs any required machine-specific adjustment to the address of
+a trampoline (passed as ``tramp``).
+
+Arguments:
+""""""""""
+
+``tramp`` must point to a block of memory which already has trampoline
+code filled in by a previous call to
+:ref:`llvm.init.trampoline <int_it>`.
+
+Semantics:
+""""""""""
+
+On some architectures the address of the code to be executed needs to be
+different than the address where the trampoline is actually stored. This
+intrinsic returns the executable address corresponding to ``tramp``
+after performing the required machine specific adjustments. The pointer
+returned can then be :ref:`bitcast and executed <int_trampoline>`.
+
+Masked Vector Load and Store Intrinsics
+---------------------------------------
+
+LLVM provides intrinsics for predicated vector load and store operations. The predicate is specified by a mask operand, which holds one bit per vector element, switching the associated vector lane on or off. The memory addresses corresponding to the "off" lanes are not accessed. When all bits of the mask are on, the intrinsic is identical to a regular vector load or store. When all bits are off, no memory is accessed.
+
+.. _int_mload:
+
+'``llvm.masked.load.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic. The loaded data is a vector of any integer or floating point data type.
+
+::
+
+ declare <16 x float> @llvm.masked.load.v16f32 (<16 x float>* <ptr>, i32 <alignment>, <16 x i1> <mask>, <16 x float> <passthru>)
+ declare <2 x double> @llvm.masked.load.v2f64 (<2 x double>* <ptr>, i32 <alignment>, <2 x i1> <mask>, <2 x double> <passthru>)
+
+Overview:
+"""""""""
+
+Reads a vector from memory according to the provided mask. The mask holds a bit for each vector lane, and is used to prevent memory accesses to the masked-off lanes. The masked-off lanes in the result vector are taken from the corresponding lanes in the passthru operand.
+
+
+Arguments:
+""""""""""
+
+The first operand is the base pointer for the load. The second operand is the alignment of the source location. It must be a constant integer value. The third operand, mask, is a vector of boolean 'i1' values with the same number of elements as the return type. The fourth is a pass-through value that is used to fill the masked-off lanes of the result. The return type, underlying type of the base pointer and the type of passthru operand are the same vector types.
+
+
+Semantics:
+""""""""""
+
+The '``llvm.masked.load``' intrinsic is designed for conditional reading of selected vector elements in a single IR operation. It is useful for targets that support vector masked loads and allows vectorizing predicated basic blocks on these targets. Other targets may support this intrinsic differently, for example by lowering it into a sequence of branches that guard scalar load operations.
+The result of this operation is equivalent to a regular vector load instruction followed by a 'select' between the loaded and the passthru values, predicated on the same mask. However, using this intrinsic prevents exceptions on memory access to masked-off lanes.
+
+
+::
+
+ %res = call <16 x float> @llvm.masked.load.v16f32 (<16 x float>* %ptr, i32 4, <16 x i1>%mask, <16 x float> %passthru)
+
+ ;; The result of the two following instructions is identical aside from potential memory access exception
+ %loadlal = load <16 x float>* %ptr, align 4
+ %res = select <16 x i1> %mask, <16 x float> %loadlal, <16 x float> %passthru
+
+.. _int_mstore:
+
+'``llvm.masked.store.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+This is an overloaded intrinsic. The data stored in memory is a vector of any integer or floating point data type.
+
+::
+
+ declare void @llvm.masked.store.v8i32 (<8 x i32> <value>, <8 x i32> * <ptr>, i32 <alignment>, <8 x i1> <mask>)
+ declare void @llvm.masked.store.v16f32(<16 x i32> <value>, <16 x i32>* <ptr>, i32 <alignment>, <16 x i1> <mask>)
+
+Overview:
+"""""""""
+
+Writes a vector to memory according to the provided mask. The mask holds a bit for each vector lane, and is used to prevent memory accesses to the masked-off lanes.
+
+Arguments:
+""""""""""
+
+The first operand is the vector value to be written to memory. The second operand is the base pointer for the store, it has the same underlying type as the value operand. The third operand is the alignment of the destination location. The fourth operand, mask, is a vector of boolean values. The types of the mask and the value operand must have the same number of vector elements.
+
+
+Semantics:
+""""""""""
+
+The '``llvm.masked.store``' intrinsics is designed for conditional writing of selected vector elements in a single IR operation. It is useful for targets that support vector masked store and allows vectorizing predicated basic blocks on these targets. Other targets may support this intrinsic differently, for example by lowering it into a sequence of branches that guard scalar store operations.
+The result of this operation is equivalent to a load-modify-store sequence. However, using this intrinsic prevents exceptions and data races on memory access to masked-off lanes.
+
+::
+
+ call void @llvm.masked.store.v16f32(<16 x float> %value, <16 x float>* %ptr, i32 4, <16 x i1> %mask)
+
+ ;; The result of the following instructions is identical aside from potential data races and memory access exceptions
+ %oldval = load <16 x float>* %ptr, align 4
+ %res = select <16 x i1> %mask, <16 x float> %value, <16 x float> %oldval
+ store <16 x float> %res, <16 x float>* %ptr, align 4
+
+
+Memory Use Markers
+------------------
+
+This class of intrinsics provides information about the lifetime of
+memory objects and ranges where variables are immutable.
+
+.. _int_lifestart:
+
+'``llvm.lifetime.start``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.lifetime.start(i64 <size>, i8* nocapture <ptr>)
+
+Overview:
+"""""""""
+
+The '``llvm.lifetime.start``' intrinsic specifies the start of a memory
+object's lifetime.
+
+Arguments:
+""""""""""
+
+The first argument is a constant integer representing the size of the
+object, or -1 if it is variable sized. The second argument is a pointer
+to the object.
+
+Semantics:
+""""""""""
+
+This intrinsic indicates that before this point in the code, the value
+of the memory pointed to by ``ptr`` is dead. This means that it is known
+to never be used and has an undefined value. A load from the pointer
+that precedes this intrinsic can be replaced with ``'undef'``.
+
+.. _int_lifeend:
+
+'``llvm.lifetime.end``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.lifetime.end(i64 <size>, i8* nocapture <ptr>)
+
+Overview:
+"""""""""
+
+The '``llvm.lifetime.end``' intrinsic specifies the end of a memory
+object's lifetime.
+
+Arguments:
+""""""""""
+
+The first argument is a constant integer representing the size of the
+object, or -1 if it is variable sized. The second argument is a pointer
+to the object.
+
+Semantics:
+""""""""""
+
+This intrinsic indicates that after this point in the code, the value of
+the memory pointed to by ``ptr`` is dead. This means that it is known to
+never be used and has an undefined value. Any stores into the memory
+object following this intrinsic may be removed as dead.
+
+'``llvm.invariant.start``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare {}* @llvm.invariant.start(i64 <size>, i8* nocapture <ptr>)
+
+Overview:
+"""""""""
+
+The '``llvm.invariant.start``' intrinsic specifies that the contents of
+a memory object will not change.
+
+Arguments:
+""""""""""
+
+The first argument is a constant integer representing the size of the
+object, or -1 if it is variable sized. The second argument is a pointer
+to the object.
+
+Semantics:
+""""""""""
+
+This intrinsic indicates that until an ``llvm.invariant.end`` that uses
+the return value, the referenced memory location is constant and
+unchanging.
+
+'``llvm.invariant.end``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.invariant.end({}* <start>, i64 <size>, i8* nocapture <ptr>)
+
+Overview:
+"""""""""
+
+The '``llvm.invariant.end``' intrinsic specifies that the contents of a
+memory object are mutable.
+
+Arguments:
+""""""""""
+
+The first argument is the matching ``llvm.invariant.start`` intrinsic.
+The second argument is a constant integer representing the size of the
+object, or -1 if it is variable sized and the third argument is a
+pointer to the object.
+
+Semantics:
+""""""""""
+
+This intrinsic indicates that the memory is mutable again.
+
+General Intrinsics
+------------------
+
+This class of intrinsics is designed to be generic and has no specific
+purpose.
+
+'``llvm.var.annotation``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int>)
+
+Overview:
+"""""""""
+
+The '``llvm.var.annotation``' intrinsic.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to a value, the second is a pointer to a
+global string, the third is a pointer to a global string which is the
+source file name, and the last argument is the line number.
+
+Semantics:
+""""""""""
+
+This intrinsic allows annotation of local variables with arbitrary
+strings. This can be useful for special purpose optimizations that want
+to look for these annotations. These have no other defined use; they are
+ignored by code generation and optimization.
+
+'``llvm.ptr.annotation.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use '``llvm.ptr.annotation``' on a
+pointer to an integer of any width. *NOTE* you must specify an address space for
+the pointer. The identifier for the default address space is the integer
+'``0``'.
+
+::
+
+ declare i8* @llvm.ptr.annotation.p<address space>i8(i8* <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i16* @llvm.ptr.annotation.p<address space>i16(i16* <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i32* @llvm.ptr.annotation.p<address space>i32(i32* <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i64* @llvm.ptr.annotation.p<address space>i64(i64* <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i256* @llvm.ptr.annotation.p<address space>i256(i256* <val>, i8* <str>, i8* <str>, i32 <int>)
+
+Overview:
+"""""""""
+
+The '``llvm.ptr.annotation``' intrinsic.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to an integer value of arbitrary bitwidth
+(result of some expression), the second is a pointer to a global string, the
+third is a pointer to a global string which is the source file name, and the
+last argument is the line number. It returns the value of the first argument.
+
+Semantics:
+""""""""""
+
+This intrinsic allows annotation of a pointer to an integer with arbitrary
+strings. This can be useful for special purpose optimizations that want to look
+for these annotations. These have no other defined use; they are ignored by code
+generation and optimization.
+
+'``llvm.annotation.*``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use '``llvm.annotation``' on
+any integer bit width.
+
+::
+
+ declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int>)
+ declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int>)
+
+Overview:
+"""""""""
+
+The '``llvm.annotation``' intrinsic.
+
+Arguments:
+""""""""""
+
+The first argument is an integer value (result of some expression), the
+second is a pointer to a global string, the third is a pointer to a
+global string which is the source file name, and the last argument is
+the line number. It returns the value of the first argument.
+
+Semantics:
+""""""""""
+
+This intrinsic allows annotations to be put on arbitrary expressions
+with arbitrary strings. This can be useful for special purpose
+optimizations that want to look for these annotations. These have no
+other defined use; they are ignored by code generation and optimization.
+
+'``llvm.trap``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.trap() noreturn nounwind
+
+Overview:
+"""""""""
+
+The '``llvm.trap``' intrinsic.
+
+Arguments:
+""""""""""
+
+None.
+
+Semantics:
+""""""""""
+
+This intrinsic is lowered to the target dependent trap instruction. If
+the target does not have a trap instruction, this intrinsic will be
+lowered to a call of the ``abort()`` function.
+
+'``llvm.debugtrap``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.debugtrap() nounwind
+
+Overview:
+"""""""""
+
+The '``llvm.debugtrap``' intrinsic.
+
+Arguments:
+""""""""""
+
+None.
+
+Semantics:
+""""""""""
+
+This intrinsic is lowered to code which is intended to cause an
+execution trap with the intention of requesting the attention of a
+debugger.
+
+'``llvm.stackprotector``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.stackprotector(i8* <guard>, i8** <slot>)
+
+Overview:
+"""""""""
+
+The ``llvm.stackprotector`` intrinsic takes the ``guard`` and stores it
+onto the stack at ``slot``. The stack slot is adjusted to ensure that it
+is placed on the stack before local variables.
+
+Arguments:
+""""""""""
+
+The ``llvm.stackprotector`` intrinsic requires two pointer arguments.
+The first argument is the value loaded from the stack guard
+``@__stack_chk_guard``. The second variable is an ``alloca`` that has
+enough space to hold the value of the guard.
+
+Semantics:
+""""""""""
+
+This intrinsic causes the prologue/epilogue inserter to force the position of
+the ``AllocaInst`` stack slot to be before local variables on the stack. This is
+to ensure that if a local variable on the stack is overwritten, it will destroy
+the value of the guard. When the function exits, the guard on the stack is
+checked against the original guard by ``llvm.stackprotectorcheck``. If they are
+different, then ``llvm.stackprotectorcheck`` causes the program to abort by
+calling the ``__stack_chk_fail()`` function.
+
+'``llvm.stackprotectorcheck``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.stackprotectorcheck(i8** <guard>)
+
+Overview:
+"""""""""
+
+The ``llvm.stackprotectorcheck`` intrinsic compares ``guard`` against an already
+created stack protector and if they are not equal calls the
+``__stack_chk_fail()`` function.
+
+Arguments:
+""""""""""
+
+The ``llvm.stackprotectorcheck`` intrinsic requires one pointer argument, the
+the variable ``@__stack_chk_guard``.
+
+Semantics:
+""""""""""
+
+This intrinsic is provided to perform the stack protector check by comparing
+``guard`` with the stack slot created by ``llvm.stackprotector`` and if the
+values do not match call the ``__stack_chk_fail()`` function.
+
+The reason to provide this as an IR level intrinsic instead of implementing it
+via other IR operations is that in order to perform this operation at the IR
+level without an intrinsic, one would need to create additional basic blocks to
+handle the success/failure cases. This makes it difficult to stop the stack
+protector check from disrupting sibling tail calls in Codegen. With this
+intrinsic, we are able to generate the stack protector basic blocks late in
+codegen after the tail call decision has occurred.
+
+'``llvm.objectsize``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare i32 @llvm.objectsize.i32(i8* <object>, i1 <min>)
+ declare i64 @llvm.objectsize.i64(i8* <object>, i1 <min>)
+
+Overview:
+"""""""""
+
+The ``llvm.objectsize`` intrinsic is designed to provide information to
+the optimizers to determine at compile time whether a) an operation
+(like memcpy) will overflow a buffer that corresponds to an object, or
+b) that a runtime check for overflow isn't necessary. An object in this
+context means an allocation of a specific class, structure, array, or
+other object.
+
+Arguments:
+""""""""""
+
+The ``llvm.objectsize`` intrinsic takes two arguments. The first
+argument is a pointer to or into the ``object``. The second argument is
+a boolean and determines whether ``llvm.objectsize`` returns 0 (if true)
+or -1 (if false) when the object size is unknown. The second argument
+only accepts constants.
+
+Semantics:
+""""""""""
+
+The ``llvm.objectsize`` intrinsic is lowered to a constant representing
+the size of the object concerned. If the size cannot be determined at
+compile time, ``llvm.objectsize`` returns ``i32/i64 -1 or 0`` (depending
+on the ``min`` argument).
+
+'``llvm.expect``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use ``llvm.expect`` on any
+integer bit width.
+
+::
+
+ declare i1 @llvm.expect.i1(i1 <val>, i1 <expected_val>)
+ declare i32 @llvm.expect.i32(i32 <val>, i32 <expected_val>)
+ declare i64 @llvm.expect.i64(i64 <val>, i64 <expected_val>)
+
+Overview:
+"""""""""
+
+The ``llvm.expect`` intrinsic provides information about expected (the
+most probable) value of ``val``, which can be used by optimizers.
+
+Arguments:
+""""""""""
+
+The ``llvm.expect`` intrinsic takes two arguments. The first argument is
+a value. The second argument is an expected value, this needs to be a
+constant value, variables are not allowed.
+
+Semantics:
+""""""""""
+
+This intrinsic is lowered to the ``val``.
+
+'``llvm.assume``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.assume(i1 %cond)
+
+Overview:
+"""""""""
+
+The ``llvm.assume`` allows the optimizer to assume that the provided
+condition is true. This information can then be used in simplifying other parts
+of the code.
+
+Arguments:
+""""""""""
+
+The condition which the optimizer may assume is always true.
+
+Semantics:
+""""""""""
+
+The intrinsic allows the optimizer to assume that the provided condition is
+always true whenever the control flow reaches the intrinsic call. No code is
+generated for this intrinsic, and instructions that contribute only to the
+provided condition are not used for code generation. If the condition is
+violated during execution, the behavior is undefined.
+
+Note that the optimizer might limit the transformations performed on values
+used by the ``llvm.assume`` intrinsic in order to preserve the instructions
+only used to form the intrinsic's input argument. This might prove undesirable
+if the extra information provided by the ``llvm.assume`` intrinsic does not cause
+sufficient overall improvement in code quality. For this reason,
+``llvm.assume`` should not be used to document basic mathematical invariants
+that the optimizer can otherwise deduce or facts that are of little use to the
+optimizer.
+
+'``llvm.donothing``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+ declare void @llvm.donothing() nounwind readnone
+
+Overview:
+"""""""""
+
+The ``llvm.donothing`` intrinsic doesn't perform any operation. It's one of only
+two intrinsics (besides ``llvm.experimental.patchpoint``) that can be called
+with an invoke instruction.
+
+Arguments:
+""""""""""
+
+None.
+
+Semantics:
+""""""""""
+
+This intrinsic does nothing, and it's removed by optimizers and ignored
+by codegen.
+
+Stack Map Intrinsics
+--------------------
+
+LLVM provides experimental intrinsics to support runtime patching
+mechanisms commonly desired in dynamic language JITs. These intrinsics
+are described in :doc:`StackMaps`.
Added: www-releases/trunk/3.6.2/docs/_sources/Lexicon.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/Lexicon.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/Lexicon.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/Lexicon.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,231 @@
+================
+The LLVM Lexicon
+================
+
+.. note::
+
+ This document is a work in progress!
+
+Definitions
+===========
+
+A
+-
+
+**ADCE**
+ Aggressive Dead Code Elimination
+
+**AST**
+ Abstract Syntax Tree.
+
+ Due to Clang's influence (mostly the fact that parsing and semantic
+ analysis are so intertwined for C and especially C++), the typical
+ working definition of AST in the LLVM community is roughly "the
+ compiler's first complete symbolic (as opposed to textual)
+ representation of an input program".
+ As such, an "AST" might be a more general graph instead of a "tree"
+ (consider the symbolic representation for the type of a typical "linked
+ list node"). This working definition is closer to what some authors
+ call an "annotated abstract syntax tree".
+
+ Consult your favorite compiler book or search engine for more details.
+
+B
+-
+
+.. _lexicon-bb-vectorization:
+
+**BB Vectorization**
+ Basic-Block Vectorization
+
+**BURS**
+ Bottom Up Rewriting System --- A method of instruction selection for code
+ generation. An example is the `BURG
+ <http://www.program-transformation.org/Transform/BURG>`_ tool.
+
+C
+-
+
+**CSE**
+ Common Subexpression Elimination. An optimization that removes common
+ subexpression compuation. For example ``(a+b)*(a+b)`` has two subexpressions
+ that are the same: ``(a+b)``. This optimization would perform the addition
+ only once and then perform the multiply (but only if it's computationally
+ correct/safe).
+
+D
+-
+
+**DAG**
+ Directed Acyclic Graph
+
+.. _derived pointer:
+.. _derived pointers:
+
+**Derived Pointer**
+ A pointer to the interior of an object, such that a garbage collector is
+ unable to use the pointer for reachability analysis. While a derived pointer
+ is live, the corresponding object pointer must be kept in a root, otherwise
+ the collector might free the referenced object. With copying collectors,
+ derived pointers pose an additional hazard that they may be invalidated at
+ any `safe point`_. This term is used in opposition to `object pointer`_.
+
+**DSA**
+ Data Structure Analysis
+
+**DSE**
+ Dead Store Elimination
+
+F
+-
+
+**FCA**
+ First Class Aggregate
+
+G
+-
+
+**GC**
+ Garbage Collection. The practice of using reachability analysis instead of
+ explicit memory management to reclaim unused memory.
+
+H
+-
+
+.. _heap:
+
+**Heap**
+ In garbage collection, the region of memory which is managed using
+ reachability analysis.
+
+I
+-
+
+**IPA**
+ Inter-Procedural Analysis. Refers to any variety of code analysis that
+ occurs between procedures, functions or compilation units (modules).
+
+**IPO**
+ Inter-Procedural Optimization. Refers to any variety of code optimization
+ that occurs between procedures, functions or compilation units (modules).
+
+**ISel**
+ Instruction Selection
+
+L
+-
+
+**LCSSA**
+ Loop-Closed Static Single Assignment Form
+
+**LICM**
+ Loop Invariant Code Motion
+
+**Load-VN**
+ Load Value Numbering
+
+**LTO**
+ Link-Time Optimization
+
+M
+-
+
+**MC**
+ Machine Code
+
+N
+-
+
+**NFC**
+ "No functional change". Used in a commit message to indicate that a patch
+ is a pure refactoring/cleanup.
+ Usually used in the first line, so it is visible without opening the
+ actual commit email.
+
+O
+-
+.. _object pointer:
+.. _object pointers:
+
+**Object Pointer**
+ A pointer to an object such that the garbage collector is able to trace
+ references contained within the object. This term is used in opposition to
+ `derived pointer`_.
+
+P
+-
+
+**PRE**
+ Partial Redundancy Elimination
+
+R
+-
+
+**RAUW**
+
+ Replace All Uses With. The functions ``User::replaceUsesOfWith()``,
+ ``Value::replaceAllUsesWith()``, and
+ ``Constant::replaceUsesOfWithOnConstant()`` implement the replacement of one
+ Value with another by iterating over its def/use chain and fixing up all of
+ the pointers to point to the new value. See
+ also `def/use chains <ProgrammersManual.html#iterating-over-def-use-use-def-chains>`_.
+
+**Reassociation**
+ Rearranging associative expressions to promote better redundancy elimination
+ and other optimization. For example, changing ``(A+B-A)`` into ``(B+A-A)``,
+ permitting it to be optimized into ``(B+0)`` then ``(B)``.
+
+.. _roots:
+.. _stack roots:
+
+**Root**
+ In garbage collection, a pointer variable lying outside of the `heap`_ from
+ which the collector begins its reachability analysis. In the context of code
+ generation, "root" almost always refers to a "stack root" --- a local or
+ temporary variable within an executing function.
+
+**RPO**
+ Reverse postorder
+
+S
+-
+
+.. _safe point:
+
+**Safe Point**
+ In garbage collection, it is necessary to identify `stack roots`_ so that
+ reachability analysis may proceed. It may be infeasible to provide this
+ information for every instruction, so instead the information may is
+ calculated only at designated safe points. With a copying collector,
+ `derived pointers`_ must not be retained across safe points and `object
+ pointers`_ must be reloaded from stack roots.
+
+**SDISel**
+ Selection DAG Instruction Selection.
+
+**SCC**
+ Strongly Connected Component
+
+**SCCP**
+ Sparse Conditional Constant Propagation
+
+**SLP**
+ Superword-Level Parallelism, same as :ref:`Basic-Block Vectorization
+ <lexicon-bb-vectorization>`.
+
+**SRoA**
+ Scalar Replacement of Aggregates
+
+**SSA**
+ Static Single Assignment
+
+**Stack Map**
+ In garbage collection, metadata emitted by the code generator which
+ identifies `roots`_ within the stack frame of an executing function.
+
+T
+-
+
+**TBAA**
+ Type-Based Alias Analysis
+
Added: www-releases/trunk/3.6.2/docs/_sources/LibFuzzer.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/LibFuzzer.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/LibFuzzer.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/LibFuzzer.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,418 @@
+========================================================
+LibFuzzer -- a library for coverage-guided fuzz testing.
+========================================================
+.. contents::
+ :local:
+ :depth: 4
+
+Introduction
+============
+
+This library is intended primarily for in-process coverage-guided fuzz testing
+(fuzzing) of other libraries. The typical workflow looks like this:
+
+* Build the Fuzzer library as a static archive (or just a set of .o files).
+ Note that the Fuzzer contains the main() function.
+ Preferably do *not* use sanitizers while building the Fuzzer.
+* Build the library you are going to test with
+ `-fsanitize-coverage={bb,edge}[,indirect-calls,8bit-counters]`
+ and one of the sanitizers. We recommend to build the library in several
+ different modes (e.g. asan, msan, lsan, ubsan, etc) and even using different
+ optimizations options (e.g. -O0, -O1, -O2) to diversify testing.
+* Build a test driver using the same options as the library.
+ The test driver is a C/C++ file containing interesting calls to the library
+ inside a single function ``extern "C" void LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size);``
+* Link the Fuzzer, the library and the driver together into an executable
+ using the same sanitizer options as for the library.
+* Collect the initial corpus of inputs for the
+ fuzzer (a directory with test inputs, one file per input).
+ The better your inputs are the faster you will find something interesting.
+ Also try to keep your inputs small, otherwise the Fuzzer will run too slow.
+ By default, the Fuzzer limits the size of every input by 64 bytes
+ (use ``-max_len=N`` to override).
+* Run the fuzzer with the test corpus. As new interesting test cases are
+ discovered they will be added to the corpus. If a bug is discovered by
+ the sanitizer (asan, etc) it will be reported as usual and the reproducer
+ will be written to disk.
+ Each Fuzzer process is single-threaded (unless the library starts its own
+ threads). You can run the Fuzzer on the same corpus in multiple processes
+ in parallel.
+
+
+The Fuzzer is similar in concept to AFL_,
+but uses in-process Fuzzing, which is more fragile, more restrictive, but
+potentially much faster as it has no overhead for process start-up.
+It uses LLVM's SanitizerCoverage_ instrumentation to get in-process
+coverage-feedback
+
+The code resides in the LLVM repository, requires the fresh Clang compiler to build
+and is used to fuzz various parts of LLVM,
+but the Fuzzer itself does not (and should not) depend on any
+part of LLVM and can be used for other projects w/o requiring the rest of LLVM.
+
+Flags
+=====
+The most important flags are::
+
+ seed 0 Random seed. If 0, seed is generated.
+ runs -1 Number of individual test runs (-1 for infinite runs).
+ max_len 64 Maximal length of the test input.
+ cross_over 1 If 1, cross over inputs.
+ mutate_depth 5 Apply this number of consecutive mutations to each input.
+ timeout -1 Timeout in seconds (if positive). If one unit runs more than this number of seconds the process will abort.
+ help 0 Print help.
+ save_minimized_corpus 0 If 1, the minimized corpus is saved into the first input directory
+ jobs 0 Number of jobs to run. If jobs >= 1 we spawn this number of jobs in separate worker processes with stdout/stderr redirected to fuzz-JOB.log.
+ workers 0 Number of simultaneous worker processes to run the jobs. If zero, "min(jobs,NumberOfCpuCores()/2)" is used.
+ tokens 0 Use the file with tokens (one token per line) to fuzz a token based input language.
+ apply_tokens 0 Read the given input file, substitute bytes with tokens and write the result to stdout.
+ sync_command 0 Execute an external command "<sync_command> <test_corpus>" to synchronize the test corpus.
+ sync_timeout 600 Minimal timeout between syncs.
+
+For the full list of flags run the fuzzer binary with ``-help=1``.
+
+Usage examples
+==============
+
+Toy example
+-----------
+
+A simple function that does something interesting if it receives the input "HI!"::
+
+ cat << EOF >> test_fuzzer.cc
+ extern "C" void LLVMFuzzerTestOneInput(const unsigned char *data, unsigned long size) {
+ if (size > 0 && data[0] == 'H')
+ if (size > 1 && data[1] == 'I')
+ if (size > 2 && data[2] == '!')
+ __builtin_trap();
+ }
+ EOF
+ # Get lib/Fuzzer. Assuming that you already have fresh clang in PATH.
+ svn co http://llvm.org/svn/llvm-project/llvm/trunk/lib/Fuzzer
+ # Build lib/Fuzzer files.
+ clang -c -g -O2 -std=c++11 Fuzzer/*.cpp -IFuzzer
+ # Build test_fuzzer.cc with asan and link against lib/Fuzzer.
+ clang++ -fsanitize=address -fsanitize-coverage=edge test_fuzzer.cc Fuzzer*.o
+ # Run the fuzzer with no corpus.
+ ./a.out
+
+You should get ``Illegal instruction (core dumped)`` pretty quickly.
+
+PCRE2
+-----
+
+Here we show how to use lib/Fuzzer on something real, yet simple: pcre2_::
+
+ COV_FLAGS=" -fsanitize-coverage=edge,indirect-calls,8bit-counters"
+ # Get PCRE2
+ svn co svn://vcs.exim.org/pcre2/code/trunk pcre
+ # Get lib/Fuzzer. Assuming that you already have fresh clang in PATH.
+ svn co http://llvm.org/svn/llvm-project/llvm/trunk/lib/Fuzzer
+ # Build PCRE2 with AddressSanitizer and coverage.
+ (cd pcre; ./autogen.sh; CC="clang -fsanitize=address $COV_FLAGS" ./configure --prefix=`pwd`/../inst && make -j && make install)
+ # Build lib/Fuzzer files.
+ clang -c -g -O2 -std=c++11 Fuzzer/*.cpp -IFuzzer
+ # Build the the actual function that does something interesting with PCRE2.
+ cat << EOF > pcre_fuzzer.cc
+ #include <string.h>
+ #include "pcre2posix.h"
+ extern "C" void LLVMFuzzerTestOneInput(const unsigned char *data, size_t size) {
+ if (size < 1) return;
+ char *str = new char[size+1];
+ memcpy(str, data, size);
+ str[size] = 0;
+ regex_t preg;
+ if (0 == regcomp(&preg, str, 0)) {
+ regexec(&preg, str, 0, 0, 0);
+ regfree(&preg);
+ }
+ delete [] str;
+ }
+ EOF
+ clang++ -g -fsanitize=address $COV_FLAGS -c -std=c++11 -I inst/include/ pcre_fuzzer.cc
+ # Link.
+ clang++ -g -fsanitize=address -Wl,--whole-archive inst/lib/*.a -Wl,-no-whole-archive Fuzzer*.o pcre_fuzzer.o -o pcre_fuzzer
+
+This will give you a binary of the fuzzer, called ``pcre_fuzzer``.
+Now, create a directory that will hold the test corpus::
+
+ mkdir -p CORPUS
+
+For simple input languages like regular expressions this is all you need.
+For more complicated inputs populate the directory with some input samples.
+Now run the fuzzer with the corpus dir as the only parameter::
+
+ ./pcre_fuzzer ./CORPUS
+
+You will see output like this::
+
+ Seed: 1876794929
+ #0 READ cov 0 bits 0 units 1 exec/s 0
+ #1 pulse cov 3 bits 0 units 1 exec/s 0
+ #1 INITED cov 3 bits 0 units 1 exec/s 0
+ #2 pulse cov 208 bits 0 units 1 exec/s 0
+ #2 NEW cov 208 bits 0 units 2 exec/s 0 L: 64
+ #3 NEW cov 217 bits 0 units 3 exec/s 0 L: 63
+ #4 pulse cov 217 bits 0 units 3 exec/s 0
+
+* The ``Seed:`` line shows you the current random seed (you can change it with ``-seed=N`` flag).
+* The ``READ`` line shows you how many input files were read (since you passed an empty dir there were inputs, but one dummy input was synthesised).
+* The ``INITED`` line shows you that how many inputs will be fuzzed.
+* The ``NEW`` lines appear with the fuzzer finds a new interesting input, which is saved to the CORPUS dir. If multiple corpus dirs are given, the first one is used.
+* The ``pulse`` lines appear periodically to show the current status.
+
+Now, interrupt the fuzzer and run it again the same way. You will see::
+
+ Seed: 1879995378
+ #0 READ cov 0 bits 0 units 564 exec/s 0
+ #1 pulse cov 502 bits 0 units 564 exec/s 0
+ ...
+ #512 pulse cov 2933 bits 0 units 564 exec/s 512
+ #564 INITED cov 2991 bits 0 units 344 exec/s 564
+ #1024 pulse cov 2991 bits 0 units 344 exec/s 1024
+ #1455 NEW cov 2995 bits 0 units 345 exec/s 1455 L: 49
+
+This time you were running the fuzzer with a non-empty input corpus (564 items).
+As the first step, the fuzzer minimized the set to produce 344 interesting items (the ``INITED`` line)
+
+It is quite convenient to store test corpuses in git.
+As an example, here is a git repository with test inputs for the above PCRE2 fuzzer::
+
+ git clone https://github.com/kcc/fuzzing-with-sanitizers.git
+ ./pcre_fuzzer ./fuzzing-with-sanitizers/pcre2/C1/
+
+You may run ``N`` independent fuzzer jobs in parallel on ``M`` CPUs::
+
+ N=100; M=4; ./pcre_fuzzer ./CORPUS -jobs=$N -workers=$M
+
+By default (``-reload=1``) the fuzzer processes will periodically scan the CORPUS directory
+and reload any new tests. This way the test inputs found by one process will be picked up
+by all others.
+
+If ``-workers=$M`` is not supplied, ``min($N,NumberOfCpuCore/2)`` will be used.
+
+Heartbleed
+----------
+Remember Heartbleed_?
+As it was recently `shown <https://blog.hboeck.de/archives/868-How-Heartbleed-couldve-been-found.html>`_,
+fuzzing with AddressSanitizer can find Heartbleed. Indeed, here are the step-by-step instructions
+to find Heartbleed with LibFuzzer::
+
+ wget https://www.openssl.org/source/openssl-1.0.1f.tar.gz
+ tar xf openssl-1.0.1f.tar.gz
+ COV_FLAGS="-fsanitize-coverage=edge,indirect-calls" # -fsanitize-coverage=8bit-counters
+ (cd openssl-1.0.1f/ && ./config &&
+ make -j 32 CC="clang -g -fsanitize=address $COV_FLAGS")
+ # Get and build LibFuzzer
+ svn co http://llvm.org/svn/llvm-project/llvm/trunk/lib/Fuzzer
+ clang -c -g -O2 -std=c++11 Fuzzer/*.cpp -IFuzzer
+ # Get examples of key/pem files.
+ git clone https://github.com/hannob/selftls
+ cp selftls/server* . -v
+ cat << EOF > handshake-fuzz.cc
+ #include <openssl/ssl.h>
+ #include <openssl/err.h>
+ #include <assert.h>
+ SSL_CTX *sctx;
+ int Init() {
+ SSL_library_init();
+ SSL_load_error_strings();
+ ERR_load_BIO_strings();
+ OpenSSL_add_all_algorithms();
+ assert (sctx = SSL_CTX_new(TLSv1_method()));
+ assert (SSL_CTX_use_certificate_file(sctx, "server.pem", SSL_FILETYPE_PEM));
+ assert (SSL_CTX_use_PrivateKey_file(sctx, "server.key", SSL_FILETYPE_PEM));
+ return 0;
+ }
+ extern "C" void LLVMFuzzerTestOneInput(unsigned char *Data, size_t Size) {
+ static int unused = Init();
+ SSL *server = SSL_new(sctx);
+ BIO *sinbio = BIO_new(BIO_s_mem());
+ BIO *soutbio = BIO_new(BIO_s_mem());
+ SSL_set_bio(server, sinbio, soutbio);
+ SSL_set_accept_state(server);
+ BIO_write(sinbio, Data, Size);
+ SSL_do_handshake(server);
+ SSL_free(server);
+ }
+ EOF
+ # Build the fuzzer.
+ clang++ -g handshake-fuzz.cc -fsanitize=address \
+ openssl-1.0.1f/libssl.a openssl-1.0.1f/libcrypto.a Fuzzer*.o
+ # Run 20 independent fuzzer jobs.
+ ./a.out -jobs=20 -workers=20
+
+Voila::
+
+ #1048576 pulse cov 3424 bits 0 units 9 exec/s 24385
+ =================================================================
+ ==17488==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x629000004748 at pc 0x00000048c979 bp 0x7fffe3e864f0 sp 0x7fffe3e85ca8
+ READ of size 60731 at 0x629000004748 thread T0
+ #0 0x48c978 in __asan_memcpy
+ #1 0x4db504 in tls1_process_heartbeat openssl-1.0.1f/ssl/t1_lib.c:2586:3
+ #2 0x580be3 in ssl3_read_bytes openssl-1.0.1f/ssl/s3_pkt.c:1092:4
+
+Advanced features
+=================
+
+Tokens
+------
+
+By default, the fuzzer is not aware of complexities of the input language
+and when fuzzing e.g. a C++ parser it will mostly stress the lexer.
+It is very hard for the fuzzer to come up with something like ``reinterpret_cast<int>``
+from a test corpus that doesn't have it.
+See a detailed discussion of this topic at
+http://lcamtuf.blogspot.com/2015/01/afl-fuzz-making-up-grammar-with.html.
+
+lib/Fuzzer implements a simple technique that allows to fuzz input languages with
+long tokens. All you need is to prepare a text file containing up to 253 tokens, one token per line,
+and pass it to the fuzzer as ``-tokens=TOKENS_FILE.txt``.
+Three implicit tokens are added: ``" "``, ``"\t"``, and ``"\n"``.
+The fuzzer itself will still be mutating a string of bytes
+but before passing this input to the target library it will replace every byte ``b`` with the ``b``-th token.
+If there are less than ``b`` tokens, a space will be added instead.
+
+AFL compatibility
+-----------------
+LibFuzzer can be used in parallel with AFL_ on the same test corpus.
+Both fuzzers expect the test corpus to reside in a directory, one file per input.
+You can run both fuzzers on the same corpus in parallel::
+
+ ./afl-fuzz -i testcase_dir -o findings_dir /path/to/program -r @@
+ ./llvm-fuzz testcase_dir findings_dir # Will write new tests to testcase_dir
+
+Periodically restart both fuzzers so that they can use each other's findings.
+
+How good is my fuzzer?
+----------------------
+
+Once you implement your target function ``LLVMFuzzerTestOneInput`` and fuzz it to death,
+you will want to know whether the function or the corpus can be improved further.
+One easy to use metric is, of course, code coverage.
+You can get the coverage for your corpus like this::
+
+ ASAN_OPTIONS=coverage_pcs=1 ./fuzzer CORPUS_DIR -runs=0
+
+This will run all the tests in the CORPUS_DIR but will not generate any new tests
+and dump covered PCs to disk before exiting.
+Then you can subtract the set of covered PCs from the set of all instrumented PCs in the binary,
+see SanitizerCoverage_ for details.
+
+User-supplied mutators
+----------------------
+
+LibFuzzer allows to use custom (user-supplied) mutators,
+see FuzzerInterface.h_
+
+Fuzzing components of LLVM
+==========================
+
+clang-format-fuzzer
+-------------------
+The inputs are random pieces of C++-like text.
+
+Build (make sure to use fresh clang as the host compiler)::
+
+ cmake -GNinja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DLLVM_USE_SANITIZER=Address -DLLVM_USE_SANITIZE_COVERAGE=YES -DCMAKE_BUILD_TYPE=Release /path/to/llvm
+ ninja clang-format-fuzzer
+ mkdir CORPUS_DIR
+ ./bin/clang-format-fuzzer CORPUS_DIR
+
+Optionally build other kinds of binaries (asan+Debug, msan, ubsan, etc).
+
+TODO: commit the pre-fuzzed corpus to svn (?).
+
+Tracking bug: https://llvm.org/bugs/show_bug.cgi?id=23052
+
+clang-fuzzer
+------------
+
+The default behavior is very similar to ``clang-format-fuzzer``.
+Clang can also be fuzzed with Tokens_ using ``-tokens=$LLVM/lib/Fuzzer/cxx_fuzzer_tokens.txt`` option.
+
+Tracking bug: https://llvm.org/bugs/show_bug.cgi?id=23057
+
+Buildbot
+--------
+
+We have a buildbot that runs the above fuzzers for LLVM components
+24/7/365 at http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fuzzer .
+
+Pre-fuzzed test inputs in git
+-----------------------------
+
+The buildbot occumulates large test corpuses over time.
+The corpuses are stored in git on github and can be used like this::
+
+ git clone https://github.com/kcc/fuzzing-with-sanitizers.git
+ bin/clang-format-fuzzer fuzzing-with-sanitizers/llvm/clang-format/C1
+ bin/clang-fuzzer fuzzing-with-sanitizers/llvm/clang/C1/
+ bin/clang-fuzzer fuzzing-with-sanitizers/llvm/clang/TOK1 -tokens=$LLVM/llvm/lib/Fuzzer/cxx_fuzzer_tokens.txt
+
+
+FAQ
+=========================
+
+Q. Why Fuzzer does not use any of the LLVM support?
+---------------------------------------------------
+
+There are two reasons.
+
+First, we want this library to be used outside of the LLVM w/o users having to
+build the rest of LLVM. This may sound unconvincing for many LLVM folks,
+but in practice the need for building the whole LLVM frightens many potential
+users -- and we want more users to use this code.
+
+Second, there is a subtle technical reason not to rely on the rest of LLVM, or
+any other large body of code (maybe not even STL). When coverage instrumentation
+is enabled, it will also instrument the LLVM support code which will blow up the
+coverage set of the process (since the fuzzer is in-process). In other words, by
+using more external dependencies we will slow down the fuzzer while the main
+reason for it to exist is extreme speed.
+
+Q. What about Windows then? The Fuzzer contains code that does not build on Windows.
+------------------------------------------------------------------------------------
+
+The sanitizer coverage support does not work on Windows either as of 01/2015.
+Once it's there, we'll need to re-implement OS-specific parts (I/O, signals).
+
+Q. When this Fuzzer is not a good solution for a problem?
+---------------------------------------------------------
+
+* If the test inputs are validated by the target library and the validator
+ asserts/crashes on invalid inputs, the in-process fuzzer is not applicable
+ (we could use fork() w/o exec, but it comes with extra overhead).
+* Bugs in the target library may accumulate w/o being detected. E.g. a memory
+ corruption that goes undetected at first and then leads to a crash while
+ testing another input. This is why it is highly recommended to run this
+ in-process fuzzer with all sanitizers to detect most bugs on the spot.
+* It is harder to protect the in-process fuzzer from excessive memory
+ consumption and infinite loops in the target library (still possible).
+* The target library should not have significant global state that is not
+ reset between the runs.
+* Many interesting target libs are not designed in a way that supports
+ the in-process fuzzer interface (e.g. require a file path instead of a
+ byte array).
+* If a single test run takes a considerable fraction of a second (or
+ more) the speed benefit from the in-process fuzzer is negligible.
+* If the target library runs persistent threads (that outlive
+ execution of one test) the fuzzing results will be unreliable.
+
+Q. So, what exactly this Fuzzer is good for?
+--------------------------------------------
+
+This Fuzzer might be a good choice for testing libraries that have relatively
+small inputs, each input takes < 1ms to run, and the library code is not expected
+to crash on invalid inputs.
+Examples: regular expression matchers, text or binary format parsers.
+
+.. _pcre2: http://www.pcre.org/
+
+.. _AFL: http://lcamtuf.coredump.cx/afl/
+
+.. _SanitizerCoverage: http://clang.llvm.org/docs/SanitizerCoverage.html
+
+.. _Heartbleed: http://en.wikipedia.org/wiki/Heartbleed
+
+.. _FuzzerInterface.h: https://github.com/llvm-mirror/llvm/blob/master/lib/Fuzzer/FuzzerInterface.h
Added: www-releases/trunk/3.6.2/docs/_sources/LinkTimeOptimization.txt
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==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/LinkTimeOptimization.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/LinkTimeOptimization.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,299 @@
+======================================================
+LLVM Link Time Optimization: Design and Implementation
+======================================================
+
+.. contents::
+ :local:
+
+Description
+===========
+
+LLVM features powerful intermodular optimizations which can be used at link
+time. Link Time Optimization (LTO) is another name for intermodular
+optimization when performed during the link stage. This document describes the
+interface and design between the LTO optimizer and the linker.
+
+Design Philosophy
+=================
+
+The LLVM Link Time Optimizer provides complete transparency, while doing
+intermodular optimization, in the compiler tool chain. Its main goal is to let
+the developer take advantage of intermodular optimizations without making any
+significant changes to the developer's makefiles or build system. This is
+achieved through tight integration with the linker. In this model, the linker
+treates LLVM bitcode files like native object files and allows mixing and
+matching among them. The linker uses `libLTO`_, a shared object, to handle LLVM
+bitcode files. This tight integration between the linker and LLVM optimizer
+helps to do optimizations that are not possible in other models. The linker
+input allows the optimizer to avoid relying on conservative escape analysis.
+
+.. _libLTO-example:
+
+Example of link time optimization
+---------------------------------
+
+The following example illustrates the advantages of LTO's integrated approach
+and clean interface. This example requires a system linker which supports LTO
+through the interface described in this document. Here, clang transparently
+invokes system linker.
+
+* Input source file ``a.c`` is compiled into LLVM bitcode form.
+* Input source file ``main.c`` is compiled into native object code.
+
+.. code-block:: c++
+
+ --- a.h ---
+ extern int foo1(void);
+ extern void foo2(void);
+ extern void foo4(void);
+
+ --- a.c ---
+ #include "a.h"
+
+ static signed int i = 0;
+
+ void foo2(void) {
+ i = -1;
+ }
+
+ static int foo3() {
+ foo4();
+ return 10;
+ }
+
+ int foo1(void) {
+ int data = 0;
+
+ if (i < 0)
+ data = foo3();
+
+ data = data + 42;
+ return data;
+ }
+
+ --- main.c ---
+ #include <stdio.h>
+ #include "a.h"
+
+ void foo4(void) {
+ printf("Hi\n");
+ }
+
+ int main() {
+ return foo1();
+ }
+
+To compile, run:
+
+.. code-block:: console
+
+ % clang -emit-llvm -c a.c -o a.o # <-- a.o is LLVM bitcode file
+ % clang -c main.c -o main.o # <-- main.o is native object file
+ % clang a.o main.o -o main # <-- standard link command without modifications
+
+* In this example, the linker recognizes that ``foo2()`` is an externally
+ visible symbol defined in LLVM bitcode file. The linker completes its usual
+ symbol resolution pass and finds that ``foo2()`` is not used
+ anywhere. This information is used by the LLVM optimizer and it
+ removes ``foo2()``.
+
+* As soon as ``foo2()`` is removed, the optimizer recognizes that condition ``i
+ < 0`` is always false, which means ``foo3()`` is never used. Hence, the
+ optimizer also removes ``foo3()``.
+
+* And this in turn, enables linker to remove ``foo4()``.
+
+This example illustrates the advantage of tight integration with the
+linker. Here, the optimizer can not remove ``foo3()`` without the linker's
+input.
+
+Alternative Approaches
+----------------------
+
+**Compiler driver invokes link time optimizer separately.**
+ In this model the link time optimizer is not able to take advantage of
+ information collected during the linker's normal symbol resolution phase.
+ In the above example, the optimizer can not remove ``foo2()`` without the
+ linker's input because it is externally visible. This in turn prohibits the
+ optimizer from removing ``foo3()``.
+
+**Use separate tool to collect symbol information from all object files.**
+ In this model, a new, separate, tool or library replicates the linker's
+ capability to collect information for link time optimization. Not only is
+ this code duplication difficult to justify, but it also has several other
+ disadvantages. For example, the linking semantics and the features provided
+ by the linker on various platform are not unique. This means, this new tool
+ needs to support all such features and platforms in one super tool or a
+ separate tool per platform is required. This increases maintenance cost for
+ link time optimizer significantly, which is not necessary. This approach
+ also requires staying synchronized with linker developements on various
+ platforms, which is not the main focus of the link time optimizer. Finally,
+ this approach increases end user's build time due to the duplication of work
+ done by this separate tool and the linker itself.
+
+Multi-phase communication between ``libLTO`` and linker
+=======================================================
+
+The linker collects information about symbol definitions and uses in various
+link objects which is more accurate than any information collected by other
+tools during typical build cycles. The linker collects this information by
+looking at the definitions and uses of symbols in native .o files and using
+symbol visibility information. The linker also uses user-supplied information,
+such as a list of exported symbols. LLVM optimizer collects control flow
+information, data flow information and knows much more about program structure
+from the optimizer's point of view. Our goal is to take advantage of tight
+integration between the linker and the optimizer by sharing this information
+during various linking phases.
+
+Phase 1 : Read LLVM Bitcode Files
+---------------------------------
+
+The linker first reads all object files in natural order and collects symbol
+information. This includes native object files as well as LLVM bitcode files.
+To minimize the cost to the linker in the case that all .o files are native
+object files, the linker only calls ``lto_module_create()`` when a supplied
+object file is found to not be a native object file. If ``lto_module_create()``
+returns that the file is an LLVM bitcode file, the linker then iterates over the
+module using ``lto_module_get_symbol_name()`` and
+``lto_module_get_symbol_attribute()`` to get all symbols defined and referenced.
+This information is added to the linker's global symbol table.
+
+
+The lto* functions are all implemented in a shared object libLTO. This allows
+the LLVM LTO code to be updated independently of the linker tool. On platforms
+that support it, the shared object is lazily loaded.
+
+Phase 2 : Symbol Resolution
+---------------------------
+
+In this stage, the linker resolves symbols using global symbol table. It may
+report undefined symbol errors, read archive members, replace weak symbols, etc.
+The linker is able to do this seamlessly even though it does not know the exact
+content of input LLVM bitcode files. If dead code stripping is enabled then the
+linker collects the list of live symbols.
+
+Phase 3 : Optimize Bitcode Files
+--------------------------------
+
+After symbol resolution, the linker tells the LTO shared object which symbols
+are needed by native object files. In the example above, the linker reports
+that only ``foo1()`` is used by native object files using
+``lto_codegen_add_must_preserve_symbol()``. Next the linker invokes the LLVM
+optimizer and code generators using ``lto_codegen_compile()`` which returns a
+native object file creating by merging the LLVM bitcode files and applying
+various optimization passes.
+
+Phase 4 : Symbol Resolution after optimization
+----------------------------------------------
+
+In this phase, the linker reads optimized a native object file and updates the
+internal global symbol table to reflect any changes. The linker also collects
+information about any changes in use of external symbols by LLVM bitcode
+files. In the example above, the linker notes that ``foo4()`` is not used any
+more. If dead code stripping is enabled then the linker refreshes the live
+symbol information appropriately and performs dead code stripping.
+
+After this phase, the linker continues linking as if it never saw LLVM bitcode
+files.
+
+.. _libLTO:
+
+``libLTO``
+==========
+
+``libLTO`` is a shared object that is part of the LLVM tools, and is intended
+for use by a linker. ``libLTO`` provides an abstract C interface to use the LLVM
+interprocedural optimizer without exposing details of LLVM's internals. The
+intention is to keep the interface as stable as possible even when the LLVM
+optimizer continues to evolve. It should even be possible for a completely
+different compilation technology to provide a different libLTO that works with
+their object files and the standard linker tool.
+
+``lto_module_t``
+----------------
+
+A non-native object file is handled via an ``lto_module_t``. The following
+functions allow the linker to check if a file (on disk or in a memory buffer) is
+a file which libLTO can process:
+
+.. code-block:: c
+
+ lto_module_is_object_file(const char*)
+ lto_module_is_object_file_for_target(const char*, const char*)
+ lto_module_is_object_file_in_memory(const void*, size_t)
+ lto_module_is_object_file_in_memory_for_target(const void*, size_t, const char*)
+
+If the object file can be processed by ``libLTO``, the linker creates a
+``lto_module_t`` by using one of:
+
+.. code-block:: c
+
+ lto_module_create(const char*)
+ lto_module_create_from_memory(const void*, size_t)
+
+and when done, the handle is released via
+
+.. code-block:: c
+
+ lto_module_dispose(lto_module_t)
+
+
+The linker can introspect the non-native object file by getting the number of
+symbols and getting the name and attributes of each symbol via:
+
+.. code-block:: c
+
+ lto_module_get_num_symbols(lto_module_t)
+ lto_module_get_symbol_name(lto_module_t, unsigned int)
+ lto_module_get_symbol_attribute(lto_module_t, unsigned int)
+
+The attributes of a symbol include the alignment, visibility, and kind.
+
+``lto_code_gen_t``
+------------------
+
+Once the linker has loaded each non-native object files into an
+``lto_module_t``, it can request ``libLTO`` to process them all and generate a
+native object file. This is done in a couple of steps. First, a code generator
+is created with:
+
+.. code-block:: c
+
+ lto_codegen_create()
+
+Then, each non-native object file is added to the code generator with:
+
+.. code-block:: c
+
+ lto_codegen_add_module(lto_code_gen_t, lto_module_t)
+
+The linker then has the option of setting some codegen options. Whether or not
+to generate DWARF debug info is set with:
+
+.. code-block:: c
+
+ lto_codegen_set_debug_model(lto_code_gen_t)
+
+Which kind of position independence is set with:
+
+.. code-block:: c
+
+ lto_codegen_set_pic_model(lto_code_gen_t)
+
+And each symbol that is referenced by a native object file or otherwise must not
+be optimized away is set with:
+
+.. code-block:: c
+
+ lto_codegen_add_must_preserve_symbol(lto_code_gen_t, const char*)
+
+After all these settings are done, the linker requests that a native object file
+be created from the modules with the settings using:
+
+.. code-block:: c
+
+ lto_codegen_compile(lto_code_gen_t, size*)
+
+which returns a pointer to a buffer containing the generated native object file.
+The linker then parses that and links it with the rest of the native object
+files.
Added: www-releases/trunk/3.6.2/docs/_sources/MCJITDesignAndImplementation.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/MCJITDesignAndImplementation.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/MCJITDesignAndImplementation.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/MCJITDesignAndImplementation.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,180 @@
+===============================
+MCJIT Design and Implementation
+===============================
+
+Introduction
+============
+
+This document describes the internal workings of the MCJIT execution
+engine and the RuntimeDyld component. It is intended as a high level
+overview of the implementation, showing the flow and interactions of
+objects throughout the code generation and dynamic loading process.
+
+Engine Creation
+===============
+
+In most cases, an EngineBuilder object is used to create an instance of
+the MCJIT execution engine. The EngineBuilder takes an llvm::Module
+object as an argument to its constructor. The client may then set various
+options that we control the later be passed along to the MCJIT engine,
+including the selection of MCJIT as the engine type to be created.
+Of particular interest is the EngineBuilder::setMCJITMemoryManager
+function. If the client does not explicitly create a memory manager at
+this time, a default memory manager (specifically SectionMemoryManager)
+will be created when the MCJIT engine is instantiated.
+
+Once the options have been set, a client calls EngineBuilder::create to
+create an instance of the MCJIT engine. If the client does not use the
+form of this function that takes a TargetMachine as a parameter, a new
+TargetMachine will be created based on the target triple associated with
+the Module that was used to create the EngineBuilder.
+
+.. image:: MCJIT-engine-builder.png
+
+EngineBuilder::create will call the static MCJIT::createJIT function,
+passing in its pointers to the module, memory manager and target machine
+objects, all of which will subsequently be owned by the MCJIT object.
+
+The MCJIT class has a member variable, Dyld, which contains an instance of
+the RuntimeDyld wrapper class. This member will be used for
+communications between MCJIT and the actual RuntimeDyldImpl object that
+gets created when an object is loaded.
+
+.. image:: MCJIT-creation.png
+
+Upon creation, MCJIT holds a pointer to the Module object that it received
+from EngineBuilder but it does not immediately generate code for this
+module. Code generation is deferred until either the
+MCJIT::finalizeObject method is called explicitly or a function such as
+MCJIT::getPointerToFunction is called which requires the code to have been
+generated.
+
+Code Generation
+===============
+
+When code generation is triggered, as described above, MCJIT will first
+attempt to retrieve an object image from its ObjectCache member, if one
+has been set. If a cached object image cannot be retrieved, MCJIT will
+call its emitObject method. MCJIT::emitObject uses a local PassManager
+instance and creates a new ObjectBufferStream instance, both of which it
+passes to TargetMachine::addPassesToEmitMC before calling PassManager::run
+on the Module with which it was created.
+
+.. image:: MCJIT-load.png
+
+The PassManager::run call causes the MC code generation mechanisms to emit
+a complete relocatable binary object image (either in either ELF or MachO
+format, depending on the target) into the ObjectBufferStream object, which
+is flushed to complete the process. If an ObjectCache is being used, the
+image will be passed to the ObjectCache here.
+
+At this point, the ObjectBufferStream contains the raw object image.
+Before the code can be executed, the code and data sections from this
+image must be loaded into suitable memory, relocations must be applied and
+memory permission and code cache invalidation (if required) must be completed.
+
+Object Loading
+==============
+
+Once an object image has been obtained, either through code generation or
+having been retrieved from an ObjectCache, it is passed to RuntimeDyld to
+be loaded. The RuntimeDyld wrapper class examines the object to determine
+its file format and creates an instance of either RuntimeDyldELF or
+RuntimeDyldMachO (both of which derive from the RuntimeDyldImpl base
+class) and calls the RuntimeDyldImpl::loadObject method to perform that
+actual loading.
+
+.. image:: MCJIT-dyld-load.png
+
+RuntimeDyldImpl::loadObject begins by creating an ObjectImage instance
+from the ObjectBuffer it received. ObjectImage, which wraps the
+ObjectFile class, is a helper class which parses the binary object image
+and provides access to the information contained in the format-specific
+headers, including section, symbol and relocation information.
+
+RuntimeDyldImpl::loadObject then iterates through the symbols in the
+image. Information about common symbols is collected for later use. For
+each function or data symbol, the associated section is loaded into memory
+and the symbol is stored in a symbol table map data structure. When the
+iteration is complete, a section is emitted for the common symbols.
+
+Next, RuntimeDyldImpl::loadObject iterates through the sections in the
+object image and for each section iterates through the relocations for
+that sections. For each relocation, it calls the format-specific
+processRelocationRef method, which will examine the relocation and store
+it in one of two data structures, a section-based relocation list map and
+an external symbol relocation map.
+
+.. image:: MCJIT-load-object.png
+
+When RuntimeDyldImpl::loadObject returns, all of the code and data
+sections for the object will have been loaded into memory allocated by the
+memory manager and relocation information will have been prepared, but the
+relocations have not yet been applied and the generated code is still not
+ready to be executed.
+
+[Currently (as of August 2013) the MCJIT engine will immediately apply
+relocations when loadObject completes. However, this shouldn't be
+happening. Because the code may have been generated for a remote target,
+the client should be given a chance to re-map the section addresses before
+relocations are applied. It is possible to apply relocations multiple
+times, but in the case where addresses are to be re-mapped, this first
+application is wasted effort.]
+
+Address Remapping
+=================
+
+At any time after initial code has been generated and before
+finalizeObject is called, the client can remap the address of sections in
+the object. Typically this is done because the code was generated for an
+external process and is being mapped into that process' address space.
+The client remaps the section address by calling MCJIT::mapSectionAddress.
+This should happen before the section memory is copied to its new
+location.
+
+When MCJIT::mapSectionAddress is called, MCJIT passes the call on to
+RuntimeDyldImpl (via its Dyld member). RuntimeDyldImpl stores the new
+address in an internal data structure but does not update the code at this
+time, since other sections are likely to change.
+
+When the client is finished remapping section addresses, it will call
+MCJIT::finalizeObject to complete the remapping process.
+
+Final Preparations
+==================
+
+When MCJIT::finalizeObject is called, MCJIT calls
+RuntimeDyld::resolveRelocations. This function will attempt to locate any
+external symbols and then apply all relocations for the object.
+
+External symbols are resolved by calling the memory manager's
+getPointerToNamedFunction method. The memory manager will return the
+address of the requested symbol in the target address space. (Note, this
+may not be a valid pointer in the host process.) RuntimeDyld will then
+iterate through the list of relocations it has stored which are associated
+with this symbol and invoke the resolveRelocation method which, through an
+format-specific implementation, will apply the relocation to the loaded
+section memory.
+
+Next, RuntimeDyld::resolveRelocations iterates through the list of
+sections and for each section iterates through a list of relocations that
+have been saved which reference that symbol and call resolveRelocation for
+each entry in this list. The relocation list here is a list of
+relocations for which the symbol associated with the relocation is located
+in the section associated with the list. Each of these locations will
+have a target location at which the relocation will be applied that is
+likely located in a different section.
+
+.. image:: MCJIT-resolve-relocations.png
+
+Once relocations have been applied as described above, MCJIT calls
+RuntimeDyld::getEHFrameSection, and if a non-zero result is returned
+passes the section data to the memory manager's registerEHFrames method.
+This allows the memory manager to call any desired target-specific
+functions, such as registering the EH frame information with a debugger.
+
+Finally, MCJIT calls the memory manager's finalizeMemory method. In this
+method, the memory manager will invalidate the target code cache, if
+necessary, and apply final permissions to the memory pages it has
+allocated for code and data memory.
+
Added: www-releases/trunk/3.6.2/docs/_sources/MakefileGuide.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/MakefileGuide.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/MakefileGuide.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/MakefileGuide.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,916 @@
+===================
+LLVM Makefile Guide
+===================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+This document provides *usage* information about the LLVM makefile system. While
+loosely patterned after the BSD makefile system, LLVM has taken a departure from
+BSD in order to implement additional features needed by LLVM. Although makefile
+systems, such as ``automake``, were attempted at one point, it has become clear
+that the features needed by LLVM and the ``Makefile`` norm are too great to use
+a more limited tool. Consequently, LLVM requires simply GNU Make 3.79, a widely
+portable makefile processor. LLVM unabashedly makes heavy use of the features of
+GNU Make so the dependency on GNU Make is firm. If you're not familiar with
+``make``, it is recommended that you read the `GNU Makefile Manual
+<http://www.gnu.org/software/make/manual/make.html>`_.
+
+While this document is rightly part of the `LLVM Programmer's
+Manual <ProgrammersManual.html>`_, it is treated separately here because of the
+volume of content and because it is often an early source of bewilderment for
+new developers.
+
+General Concepts
+================
+
+The LLVM Makefile System is the component of LLVM that is responsible for
+building the software, testing it, generating distributions, checking those
+distributions, installing and uninstalling, etc. It consists of a several files
+throughout the source tree. These files and other general concepts are described
+in this section.
+
+Projects
+--------
+
+The LLVM Makefile System is quite generous. It not only builds its own software,
+but it can build yours too. Built into the system is knowledge of the
+``llvm/projects`` directory. Any directory under ``projects`` that has both a
+``configure`` script and a ``Makefile`` is assumed to be a project that uses the
+LLVM Makefile system. Building software that uses LLVM does not require the
+LLVM Makefile System nor even placement in the ``llvm/projects``
+directory. However, doing so will allow your project to get up and running
+quickly by utilizing the built-in features that are used to compile LLVM. LLVM
+compiles itself using the same features of the makefile system as used for
+projects.
+
+For further details, consult the `Projects <Projects.html>`_ page.
+
+Variable Values
+---------------
+
+To use the makefile system, you simply create a file named ``Makefile`` in your
+directory and declare values for certain variables. The variables and values
+that you select determine what the makefile system will do. These variables
+enable rules and processing in the makefile system that automatically Do The
+Right Thing (C).
+
+Including Makefiles
+-------------------
+
+Setting variables alone is not enough. You must include into your Makefile
+additional files that provide the rules of the LLVM Makefile system. The various
+files involved are described in the sections that follow.
+
+``Makefile``
+^^^^^^^^^^^^
+
+Each directory to participate in the build needs to have a file named
+``Makefile``. This is the file first read by ``make``. It has three
+sections:
+
+#. Settable Variables --- Required that must be set first.
+#. ``include $(LEVEL)/Makefile.common`` --- include the LLVM Makefile system.
+#. Override Variables --- Override variables set by the LLVM Makefile system.
+
+.. _$(LEVEL)/Makefile.common:
+
+``Makefile.common``
+^^^^^^^^^^^^^^^^^^^
+
+Every project must have a ``Makefile.common`` file at its top source
+directory. This file serves three purposes:
+
+#. It includes the project's configuration makefile to obtain values determined
+ by the ``configure`` script. This is done by including the
+ `$(LEVEL)/Makefile.config`_ file.
+
+#. It specifies any other (static) values that are needed throughout the
+ project. Only values that are used in all or a large proportion of the
+ project's directories should be placed here.
+
+#. It includes the standard rules for the LLVM Makefile system,
+ `$(LLVM_SRC_ROOT)/Makefile.rules`_. This file is the *guts* of the LLVM
+ ``Makefile`` system.
+
+.. _$(LEVEL)/Makefile.config:
+
+``Makefile.config``
+^^^^^^^^^^^^^^^^^^^
+
+Every project must have a ``Makefile.config`` at the top of its *build*
+directory. This file is **generated** by the ``configure`` script from the
+pattern provided by the ``Makefile.config.in`` file located at the top of the
+project's *source* directory. The contents of this file depend largely on what
+configuration items the project uses, however most projects can get what they
+need by just relying on LLVM's configuration found in
+``$(LLVM_OBJ_ROOT)/Makefile.config``.
+
+.. _$(LLVM_SRC_ROOT)/Makefile.rules:
+
+``Makefile.rules``
+^^^^^^^^^^^^^^^^^^
+
+This file, located at ``$(LLVM_SRC_ROOT)/Makefile.rules`` is the heart of the
+LLVM Makefile System. It provides all the logic, dependencies, and rules for
+building the targets supported by the system. What it does largely depends on
+the values of ``make`` `variables`_ that have been set *before*
+``Makefile.rules`` is included.
+
+Comments
+^^^^^^^^
+
+User ``Makefile``\s need not have comments in them unless the construction is
+unusual or it does not strictly follow the rules and patterns of the LLVM
+makefile system. Makefile comments are invoked with the pound (``#``) character.
+The ``#`` character and any text following it, to the end of the line, are
+ignored by ``make``.
+
+Tutorial
+========
+
+This section provides some examples of the different kinds of modules you can
+build with the LLVM makefile system. In general, each directory you provide will
+build a single object although that object may be composed of additionally
+compiled components.
+
+Libraries
+---------
+
+Only a few variable definitions are needed to build a regular library.
+Normally, the makefile system will build all the software into a single
+``libname.o`` (pre-linked) object. This means the library is not searchable and
+that the distinction between compilation units has been dissolved. Optionally,
+you can ask for a shared library (.so) or archive library (.a) built. Archive
+libraries are the default. For example:
+
+.. code-block:: makefile
+
+ LIBRARYNAME = mylib
+ SHARED_LIBRARY = 1
+ BUILD_ARCHIVE = 1
+
+says to build a library named ``mylib`` with both a shared library
+(``mylib.so``) and an archive library (``mylib.a``) version. The contents of all
+the libraries produced will be the same, they are just constructed differently.
+Note that you normally do not need to specify the sources involved. The LLVM
+Makefile system will infer the source files from the contents of the source
+directory.
+
+The ``LOADABLE_MODULE=1`` directive can be used in conjunction with
+``SHARED_LIBRARY=1`` to indicate that the resulting shared library should be
+openable with the ``dlopen`` function and searchable with the ``dlsym`` function
+(or your operating system's equivalents). While this isn't strictly necessary on
+Linux and a few other platforms, it is required on systems like HP-UX and
+Darwin. You should use ``LOADABLE_MODULE`` for any shared library that you
+intend to be loaded into an tool via the ``-load`` option. :ref:`Pass
+documentation <writing-an-llvm-pass-makefile>` has an example of why you might
+want to do this.
+
+Loadable Modules
+^^^^^^^^^^^^^^^^
+
+In some situations, you need to create a loadable module. Loadable modules can
+be loaded into programs like ``opt`` or ``llc`` to specify additional passes to
+run or targets to support. Loadable modules are also useful for debugging a
+pass or providing a pass with another package if that pass can't be included in
+LLVM.
+
+LLVM provides complete support for building such a module. All you need to do is
+use the ``LOADABLE_MODULE`` variable in your ``Makefile``. For example, to build
+a loadable module named ``MyMod`` that uses the LLVM libraries ``LLVMSupport.a``
+and ``LLVMSystem.a``, you would specify:
+
+.. code-block:: makefile
+
+ LIBRARYNAME := MyMod
+ LOADABLE_MODULE := 1
+ LINK_COMPONENTS := support system
+
+Use of the ``LOADABLE_MODULE`` facility implies several things:
+
+#. There will be no "``lib``" prefix on the module. This differentiates it from
+ a standard shared library of the same name.
+
+#. The `SHARED_LIBRARY`_ variable is turned on.
+
+#. The `LINK_LIBS_IN_SHARED`_ variable is turned on.
+
+A loadable module is loaded by LLVM via the facilities of libtool's libltdl
+library which is part of ``lib/System`` implementation.
+
+Tools
+-----
+
+For building executable programs (tools), you must provide the name of the tool
+and the names of the libraries you wish to link with the tool. For example:
+
+.. code-block:: makefile
+
+ TOOLNAME = mytool
+ USEDLIBS = mylib
+ LINK_COMPONENTS = support system
+
+says that we are to build a tool name ``mytool`` and that it requires three
+libraries: ``mylib``, ``LLVMSupport.a`` and ``LLVMSystem.a``.
+
+Note that two different variables are used to indicate which libraries are
+linked: ``USEDLIBS`` and ``LLVMLIBS``. This distinction is necessary to support
+projects. ``LLVMLIBS`` refers to the LLVM libraries found in the LLVM object
+directory. ``USEDLIBS`` refers to the libraries built by your project. In the
+case of building LLVM tools, ``USEDLIBS`` and ``LLVMLIBS`` can be used
+interchangeably since the "project" is LLVM itself and ``USEDLIBS`` refers to
+the same place as ``LLVMLIBS``.
+
+Also note that there are two different ways of specifying a library: with a
+``.a`` suffix and without. Without the suffix, the entry refers to the re-linked
+(.o) file which will include *all* symbols of the library. This is
+useful, for example, to include all passes from a library of passes. If the
+``.a`` suffix is used then the library is linked as a searchable library (with
+the ``-l`` option). In this case, only the symbols that are unresolved *at
+that point* will be resolved from the library, if they exist. Other
+(unreferenced) symbols will not be included when the ``.a`` syntax is used. Note
+that in order to use the ``.a`` suffix, the library in question must have been
+built with the ``BUILD_ARCHIVE`` option set.
+
+JIT Tools
+^^^^^^^^^
+
+Many tools will want to use the JIT features of LLVM. To do this, you simply
+specify that you want an execution 'engine', and the makefiles will
+automatically link in the appropriate JIT for the host or an interpreter if none
+is available:
+
+.. code-block:: makefile
+
+ TOOLNAME = my_jit_tool
+ USEDLIBS = mylib
+ LINK_COMPONENTS = engine
+
+Of course, any additional libraries may be listed as other components. To get a
+full understanding of how this changes the linker command, it is recommended
+that you:
+
+.. code-block:: bash
+
+ % cd examples/Fibonacci
+ % make VERBOSE=1
+
+Targets Supported
+=================
+
+This section describes each of the targets that can be built using the LLVM
+Makefile system. Any target can be invoked from any directory but not all are
+applicable to a given directory (e.g. "check", "dist" and "install" will always
+operate as if invoked from the top level directory).
+
+================= =============== ==================
+Target Name Implied Targets Target Description
+================= =============== ==================
+``all`` \ Compile the software recursively. Default target.
+``all-local`` \ Compile the software in the local directory only.
+``check`` \ Change to the ``test`` directory in a project and run the test suite there.
+``check-local`` \ Run a local test suite. Generally this is only defined in the ``Makefile`` of the project's ``test`` directory.
+``clean`` \ Remove built objects recursively.
+``clean-local`` \ Remove built objects from the local directory only.
+``dist`` ``all`` Prepare a source distribution tarball.
+``dist-check`` ``all`` Prepare a source distribution tarball and check that it builds.
+``dist-clean`` ``clean`` Clean source distribution tarball temporary files.
+``install`` ``all`` Copy built objects to installation directory.
+``preconditions`` ``all`` Check to make sure configuration and makefiles are up to date.
+``printvars`` ``all`` Prints variables defined by the makefile system (for debugging).
+``tags`` \ Make C and C++ tags files for emacs and vi.
+``uninstall`` \ Remove built objects from installation directory.
+================= =============== ==================
+
+.. _all:
+
+``all`` (default)
+-----------------
+
+When you invoke ``make`` with no arguments, you are implicitly instructing it to
+seek the ``all`` target (goal). This target is used for building the software
+recursively and will do different things in different directories. For example,
+in a ``lib`` directory, the ``all`` target will compile source files and
+generate libraries. But, in a ``tools`` directory, it will link libraries and
+generate executables.
+
+``all-local``
+-------------
+
+This target is the same as `all`_ but it operates only on the current directory
+instead of recursively.
+
+``check``
+---------
+
+This target can be invoked from anywhere within a project's directories but
+always invokes the `check-local`_ target in the project's ``test`` directory, if
+it exists and has a ``Makefile``. A warning is produced otherwise. If
+`TESTSUITE`_ is defined on the ``make`` command line, it will be passed down to
+the invocation of ``make check-local`` in the ``test`` directory. The intended
+usage for this is to assist in running specific suites of tests. If
+``TESTSUITE`` is not set, the implementation of ``check-local`` should run all
+normal tests. It is up to the project to define what different values for
+``TESTSUTE`` will do. See the :doc:`Testing Guide <TestingGuide>` for further
+details.
+
+``check-local``
+---------------
+
+This target should be implemented by the ``Makefile`` in the project's ``test``
+directory. It is invoked by the ``check`` target elsewhere. Each project is
+free to define the actions of ``check-local`` as appropriate for that
+project. The LLVM project itself uses the :doc:`Lit <CommandGuide/lit>` testing
+tool to run a suite of feature and regression tests. Other projects may choose
+to use :program:`lit` or any other testing mechanism.
+
+``clean``
+---------
+
+This target cleans the build directory, recursively removing all things that the
+Makefile builds. The cleaning rules have been made guarded so they shouldn't go
+awry (via ``rm -f $(UNSET_VARIABLE)/*`` which will attempt to erase the entire
+directory structure).
+
+``clean-local``
+---------------
+
+This target does the same thing as ``clean`` but only for the current (local)
+directory.
+
+``dist``
+--------
+
+This target builds a distribution tarball. It first builds the entire project
+using the ``all`` target and then tars up the necessary files and compresses
+it. The generated tarball is sufficient for a casual source distribution, but
+probably not for a release (see ``dist-check``).
+
+``dist-check``
+--------------
+
+This target does the same thing as the ``dist`` target but also checks the
+distribution tarball. The check is made by unpacking the tarball to a new
+directory, configuring it, building it, installing it, and then verifying that
+the installation results are correct (by comparing to the original build). This
+target can take a long time to run but should be done before a release goes out
+to make sure that the distributed tarball can actually be built into a working
+release.
+
+``dist-clean``
+--------------
+
+This is a special form of the ``clean`` clean target. It performs a normal
+``clean`` but also removes things pertaining to building the distribution.
+
+``install``
+-----------
+
+This target finalizes shared objects and executables and copies all libraries,
+headers, executables and documentation to the directory given with the
+``--prefix`` option to ``configure``. When completed, the prefix directory will
+have everything needed to **use** LLVM.
+
+The LLVM makefiles can generate complete **internal** documentation for all the
+classes by using ``doxygen``. By default, this feature is **not** enabled
+because it takes a long time and generates a massive amount of data (>100MB). If
+you want this feature, you must configure LLVM with the --enable-doxygen switch
+and ensure that a modern version of doxygen (1.3.7 or later) is available in
+your ``PATH``. You can download doxygen from `here
+<http://www.stack.nl/~dimitri/doxygen/download.html#latestsrc>`_.
+
+``preconditions``
+-----------------
+
+This utility target checks to see if the ``Makefile`` in the object directory is
+older than the ``Makefile`` in the source directory and copies it if so. It also
+reruns the ``configure`` script if that needs to be done and rebuilds the
+``Makefile.config`` file similarly. Users may overload this target to ensure
+that sanity checks are run *before* any building of targets as all the targets
+depend on ``preconditions``.
+
+``printvars``
+-------------
+
+This utility target just causes the LLVM makefiles to print out some of the
+makefile variables so that you can double check how things are set.
+
+``reconfigure``
+---------------
+
+This utility target will force a reconfigure of LLVM or your project. It simply
+runs ``$(PROJ_OBJ_ROOT)/config.status --recheck`` to rerun the configuration
+tests and rebuild the configured files. This isn't generally useful as the
+makefiles will reconfigure themselves whenever its necessary.
+
+``spotless``
+------------
+
+.. warning::
+
+ Use with caution!
+
+This utility target, only available when ``$(PROJ_OBJ_ROOT)`` is not the same as
+``$(PROJ_SRC_ROOT)``, will completely clean the ``$(PROJ_OBJ_ROOT)`` directory
+by removing its content entirely and reconfiguring the directory. This returns
+the ``$(PROJ_OBJ_ROOT)`` directory to a completely fresh state. All content in
+the directory except configured files and top-level makefiles will be lost.
+
+``tags``
+--------
+
+This target will generate a ``TAGS`` file in the top-level source directory. It
+is meant for use with emacs, XEmacs, or ViM. The TAGS file provides an index of
+symbol definitions so that the editor can jump you to the definition
+quickly.
+
+``uninstall``
+-------------
+
+This target is the opposite of the ``install`` target. It removes the header,
+library and executable files from the installation directories. Note that the
+directories themselves are not removed because it is not guaranteed that LLVM is
+the only thing installing there (e.g. ``--prefix=/usr``).
+
+.. _variables:
+
+Variables
+=========
+
+Variables are used to tell the LLVM Makefile System what to do and to obtain
+information from it. Variables are also used internally by the LLVM Makefile
+System. Variable names that contain only the upper case alphabetic letters and
+underscore are intended for use by the end user. All other variables are
+internal to the LLVM Makefile System and should not be relied upon nor
+modified. The sections below describe how to use the LLVM Makefile
+variables.
+
+Control Variables
+-----------------
+
+Variables listed in the table below should be set *before* the inclusion of
+`$(LEVEL)/Makefile.common`_. These variables provide input to the LLVM make
+system that tell it what to do for the current directory.
+
+``BUILD_ARCHIVE``
+ If set to any value, causes an archive (.a) library to be built.
+
+``BUILT_SOURCES``
+ Specifies a set of source files that are generated from other source
+ files. These sources will be built before any other target processing to
+ ensure they are present.
+
+``CONFIG_FILES``
+ Specifies a set of configuration files to be installed.
+
+``DEBUG_SYMBOLS``
+ If set to any value, causes the build to include debugging symbols even in
+ optimized objects, libraries and executables. This alters the flags
+ specified to the compilers and linkers. Debugging isn't fun in an optimized
+ build, but it is possible.
+
+``DIRS``
+ Specifies a set of directories, usually children of the current directory,
+ that should also be made using the same goal. These directories will be
+ built serially.
+
+``DISABLE_AUTO_DEPENDENCIES``
+ If set to any value, causes the makefiles to **not** automatically generate
+ dependencies when running the compiler. Use of this feature is discouraged
+ and it may be removed at a later date.
+
+``ENABLE_OPTIMIZED``
+ If set to 1, causes the build to generate optimized objects, libraries and
+ executables. This alters the flags specified to the compilers and
+ linkers. Generally debugging won't be a fun experience with an optimized
+ build.
+
+``ENABLE_PROFILING``
+ If set to 1, causes the build to generate both optimized and profiled
+ objects, libraries and executables. This alters the flags specified to the
+ compilers and linkers to ensure that profile data can be collected from the
+ tools built. Use the ``gprof`` tool to analyze the output from the profiled
+ tools (``gmon.out``).
+
+``DISABLE_ASSERTIONS``
+ If set to 1, causes the build to disable assertions, even if building a
+ debug or profile build. This will exclude all assertion check code from the
+ build. LLVM will execute faster, but with little help when things go
+ wrong.
+
+``EXPERIMENTAL_DIRS``
+ Specify a set of directories that should be built, but if they fail, it
+ should not cause the build to fail. Note that this should only be used
+ temporarily while code is being written.
+
+``EXPORTED_SYMBOL_FILE``
+ Specifies the name of a single file that contains a list of the symbols to
+ be exported by the linker. One symbol per line.
+
+``EXPORTED_SYMBOL_LIST``
+ Specifies a set of symbols to be exported by the linker.
+
+``EXTRA_DIST``
+ Specifies additional files that should be distributed with LLVM. All source
+ files, all built sources, all Makefiles, and most documentation files will
+ be automatically distributed. Use this variable to distribute any files that
+ are not automatically distributed.
+
+``KEEP_SYMBOLS``
+ If set to any value, specifies that when linking executables the makefiles
+ should retain debug symbols in the executable. Normally, symbols are
+ stripped from the executable.
+
+``LEVEL`` (required)
+ Specify the level of nesting from the top level. This variable must be set
+ in each makefile as it is used to find the top level and thus the other
+ makefiles.
+
+``LIBRARYNAME``
+ Specify the name of the library to be built. (Required For Libraries)
+
+``LINK_COMPONENTS``
+ When specified for building a tool, the value of this variable will be
+ passed to the ``llvm-config`` tool to generate a link line for the
+ tool. Unlike ``USEDLIBS`` and ``LLVMLIBS``, not all libraries need to be
+ specified. The ``llvm-config`` tool will figure out the library dependencies
+ and add any libraries that are needed. The ``USEDLIBS`` variable can still
+ be used in conjunction with ``LINK_COMPONENTS`` so that additional
+ project-specific libraries can be linked with the LLVM libraries specified
+ by ``LINK_COMPONENTS``.
+
+.. _LINK_LIBS_IN_SHARED:
+
+``LINK_LIBS_IN_SHARED``
+ By default, shared library linking will ignore any libraries specified with
+ the `LLVMLIBS`_ or `USEDLIBS`_. This prevents shared libs from including
+ things that will be in the LLVM tool the shared library will be loaded
+ into. However, sometimes it is useful to link certain libraries into your
+ shared library and this option enables that feature.
+
+.. _LLVMLIBS:
+
+``LLVMLIBS``
+ Specifies the set of libraries from the LLVM ``$(ObjDir)`` that will be
+ linked into the tool or library.
+
+``LOADABLE_MODULE``
+ If set to any value, causes the shared library being built to also be a
+ loadable module. Loadable modules can be opened with the dlopen() function
+ and searched with dlsym (or the operating system's equivalent). Note that
+ setting this variable without also setting ``SHARED_LIBRARY`` will have no
+ effect.
+
+``NO_INSTALL``
+ Specifies that the build products of the directory should not be installed
+ but should be built even if the ``install`` target is given. This is handy
+ for directories that build libraries or tools that are only used as part of
+ the build process, such as code generators (e.g. ``tblgen``).
+
+``OPTIONAL_DIRS``
+ Specify a set of directories that may be built, if they exist, but it is
+ not an error for them not to exist.
+
+``PARALLEL_DIRS``
+ Specify a set of directories to build recursively and in parallel if the
+ ``-j`` option was used with ``make``.
+
+.. _SHARED_LIBRARY:
+
+``SHARED_LIBRARY``
+ If set to any value, causes a shared library (``.so``) to be built in
+ addition to any other kinds of libraries. Note that this option will cause
+ all source files to be built twice: once with options for position
+ independent code and once without. Use it only where you really need a
+ shared library.
+
+``SOURCES`` (optional)
+ Specifies the list of source files in the current directory to be
+ built. Source files of any type may be specified (programs, documentation,
+ config files, etc.). If not specified, the makefile system will infer the
+ set of source files from the files present in the current directory.
+
+``SUFFIXES``
+ Specifies a set of filename suffixes that occur in suffix match rules. Only
+ set this if your local ``Makefile`` specifies additional suffix match
+ rules.
+
+``TARGET``
+ Specifies the name of the LLVM code generation target that the current
+ directory builds. Setting this variable enables additional rules to build
+ ``.inc`` files from ``.td`` files.
+
+.. _TESTSUITE:
+
+``TESTSUITE``
+ Specifies the directory of tests to run in ``llvm/test``.
+
+``TOOLNAME``
+ Specifies the name of the tool that the current directory should build.
+
+``TOOL_VERBOSE``
+ Implies ``VERBOSE`` and also tells each tool invoked to be verbose. This is
+ handy when you're trying to see the sub-tools invoked by each tool invoked
+ by the makefile. For example, this will pass ``-v`` to the GCC compilers
+ which causes it to print out the command lines it uses to invoke sub-tools
+ (compiler, assembler, linker).
+
+.. _USEDLIBS:
+
+``USEDLIBS``
+ Specifies the list of project libraries that will be linked into the tool or
+ library.
+
+``VERBOSE``
+ Tells the Makefile system to produce detailed output of what it is doing
+ instead of just summary comments. This will generate a LOT of output.
+
+Override Variables
+------------------
+
+Override variables can be used to override the default values provided by the
+LLVM makefile system. These variables can be set in several ways:
+
+* In the environment (e.g. setenv, export) --- not recommended.
+* On the ``make`` command line --- recommended.
+* On the ``configure`` command line.
+* In the Makefile (only *after* the inclusion of `$(LEVEL)/Makefile.common`_).
+
+The override variables are given below:
+
+``AR`` (defaulted)
+ Specifies the path to the ``ar`` tool.
+
+``PROJ_OBJ_DIR``
+ The directory into which the products of build rules will be placed. This
+ might be the same as `PROJ_SRC_DIR`_ but typically is not.
+
+.. _PROJ_SRC_DIR:
+
+``PROJ_SRC_DIR``
+ The directory which contains the source files to be built.
+
+``BUILD_EXAMPLES``
+ If set to 1, build examples in ``examples`` and (if building Clang)
+ ``tools/clang/examples`` directories.
+
+``BZIP2`` (configured)
+ The path to the ``bzip2`` tool.
+
+``CC`` (configured)
+ The path to the 'C' compiler.
+
+``CFLAGS``
+ Additional flags to be passed to the 'C' compiler.
+
+``CPPFLAGS``
+ Additional flags passed to the C/C++ preprocessor.
+
+``CXX``
+ Specifies the path to the C++ compiler.
+
+``CXXFLAGS``
+ Additional flags to be passed to the C++ compiler.
+
+``DATE`` (configured)
+ Specifies the path to the ``date`` program or any program that can generate
+ the current date and time on its standard output.
+
+``DOT`` (configured)
+ Specifies the path to the ``dot`` tool or ``false`` if there isn't one.
+
+``ECHO`` (configured)
+ Specifies the path to the ``echo`` tool for printing output.
+
+``EXEEXT`` (configured)
+ Provides the extension to be used on executables built by the makefiles.
+ The value may be empty on platforms that do not use file extensions for
+ executables (e.g. Unix).
+
+``INSTALL`` (configured)
+ Specifies the path to the ``install`` tool.
+
+``LDFLAGS`` (configured)
+ Allows users to specify additional flags to pass to the linker.
+
+``LIBS`` (configured)
+ The list of libraries that should be linked with each tool.
+
+``LIBTOOL`` (configured)
+ Specifies the path to the ``libtool`` tool. This tool is renamed ``mklib``
+ by the ``configure`` script.
+
+``LLVMAS`` (defaulted)
+ Specifies the path to the ``llvm-as`` tool.
+
+``LLVMGCC`` (defaulted)
+ Specifies the path to the LLVM version of the GCC 'C' Compiler.
+
+``LLVMGXX`` (defaulted)
+ Specifies the path to the LLVM version of the GCC C++ Compiler.
+
+``LLVMLD`` (defaulted)
+ Specifies the path to the LLVM bitcode linker tool
+
+``LLVM_OBJ_ROOT`` (configured)
+ Specifies the top directory into which the output of the build is placed.
+
+``LLVM_SRC_ROOT`` (configured)
+ Specifies the top directory in which the sources are found.
+
+``LLVM_TARBALL_NAME`` (configured)
+ Specifies the name of the distribution tarball to create. This is configured
+ from the name of the project and its version number.
+
+``MKDIR`` (defaulted)
+ Specifies the path to the ``mkdir`` tool that creates directories.
+
+``ONLY_TOOLS``
+ If set, specifies the list of tools to build.
+
+``PLATFORMSTRIPOPTS``
+ The options to provide to the linker to specify that a stripped (no symbols)
+ executable should be built.
+
+``RANLIB`` (defaulted)
+ Specifies the path to the ``ranlib`` tool.
+
+``RM`` (defaulted)
+ Specifies the path to the ``rm`` tool.
+
+``SED`` (defaulted)
+ Specifies the path to the ``sed`` tool.
+
+``SHLIBEXT`` (configured)
+ Provides the filename extension to use for shared libraries.
+
+``TBLGEN`` (defaulted)
+ Specifies the path to the ``tblgen`` tool.
+
+``TAR`` (defaulted)
+ Specifies the path to the ``tar`` tool.
+
+``ZIP`` (defaulted)
+ Specifies the path to the ``zip`` tool.
+
+Readable Variables
+------------------
+
+Variables listed in the table below can be used by the user's Makefile but
+should not be changed. Changing the value will generally cause the build to go
+wrong, so don't do it.
+
+``bindir``
+ The directory into which executables will ultimately be installed. This
+ value is derived from the ``--prefix`` option given to ``configure``.
+
+``BuildMode``
+ The name of the type of build being performed: Debug, Release, or
+ Profile.
+
+``bytecode_libdir``
+ The directory into which bitcode libraries will ultimately be installed.
+ This value is derived from the ``--prefix`` option given to ``configure``.
+
+``ConfigureScriptFLAGS``
+ Additional flags given to the ``configure`` script when reconfiguring.
+
+``DistDir``
+ The *current* directory for which a distribution copy is being made.
+
+.. _Echo:
+
+``Echo``
+ The LLVM Makefile System output command. This provides the ``llvm[n]``
+ prefix and starts with ``@`` so the command itself is not printed by
+ ``make``.
+
+``EchoCmd``
+ Same as `Echo`_ but without the leading ``@``.
+
+``includedir``
+ The directory into which include files will ultimately be installed. This
+ value is derived from the ``--prefix`` option given to ``configure``.
+
+``libdir``
+ The directory into which native libraries will ultimately be installed.
+ This value is derived from the ``--prefix`` option given to
+ ``configure``.
+
+``LibDir``
+ The configuration specific directory into which libraries are placed before
+ installation.
+
+``MakefileConfig``
+ Full path of the ``Makefile.config`` file.
+
+``MakefileConfigIn``
+ Full path of the ``Makefile.config.in`` file.
+
+``ObjDir``
+ The configuration and directory specific directory where build objects
+ (compilation results) are placed.
+
+``SubDirs``
+ The complete list of sub-directories of the current directory as
+ specified by other variables.
+
+``Sources``
+ The complete list of source files.
+
+``sysconfdir``
+ The directory into which configuration files will ultimately be
+ installed. This value is derived from the ``--prefix`` option given to
+ ``configure``.
+
+``ToolDir``
+ The configuration specific directory into which executables are placed
+ before they are installed.
+
+``TopDistDir``
+ The top most directory into which the distribution files are copied.
+
+``Verb``
+ Use this as the first thing on your build script lines to enable or disable
+ verbose mode. It expands to either an ``@`` (quiet mode) or nothing (verbose
+ mode).
+
+Internal Variables
+------------------
+
+Variables listed below are used by the LLVM Makefile System and considered
+internal. You should not use these variables under any circumstances.
+
+.. code-block:: makefile
+
+ Archive
+ AR.Flags
+ BaseNameSources
+ BCLinkLib
+ C.Flags
+ Compile.C
+ CompileCommonOpts
+ Compile.CXX
+ ConfigStatusScript
+ ConfigureScript
+ CPP.Flags
+ CPP.Flags
+ CXX.Flags
+ DependFiles
+ DestArchiveLib
+ DestBitcodeLib
+ DestModule
+ DestSharedLib
+ DestTool
+ DistAlways
+ DistCheckDir
+ DistCheckTop
+ DistFiles
+ DistName
+ DistOther
+ DistSources
+ DistSubDirs
+ DistTarBZ2
+ DistTarGZip
+ DistZip
+ ExtraLibs
+ FakeSources
+ INCFiles
+ InternalTargets
+ LD.Flags
+ LibName.A
+ LibName.BC
+ LibName.LA
+ LibName.O
+ LibTool.Flags
+ Link
+ LinkModule
+ LLVMLibDir
+ LLVMLibsOptions
+ LLVMLibsPaths
+ LLVMToolDir
+ LLVMUsedLibs
+ LocalTargets
+ Module
+ ObjectsLO
+ ObjectsO
+ ObjMakefiles
+ ParallelTargets
+ PreConditions
+ ProjLibsOptions
+ ProjLibsPaths
+ ProjUsedLibs
+ Ranlib
+ RecursiveTargets
+ SrcMakefiles
+ Strip
+ StripWarnMsg
+ TableGen
+ TDFiles
+ ToolBuildPath
+ TopLevelTargets
+ UserTargets
Added: www-releases/trunk/3.6.2/docs/_sources/MarkedUpDisassembly.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/MarkedUpDisassembly.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/MarkedUpDisassembly.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/MarkedUpDisassembly.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,86 @@
+=======================================
+LLVM's Optional Rich Disassembly Output
+=======================================
+
+.. contents::
+ :local:
+
+Introduction
+============
+
+LLVM's default disassembly output is raw text. To allow consumers more ability
+to introspect the instructions' textual representation or to reformat for a more
+user friendly display there is an optional rich disassembly output.
+
+This optional output is sufficient to reference into individual portions of the
+instruction text. This is intended for clients like disassemblers, list file
+generators, and pretty-printers, which need more than the raw instructions and
+the ability to print them.
+
+To provide this functionality the assembly text is marked up with annotations.
+The markup is simple enough in syntax to be robust even in the case of version
+mismatches between consumers and producers. That is, the syntax generally does
+not carry semantics beyond "this text has an annotation," so consumers can
+simply ignore annotations they do not understand or do not care about.
+
+After calling ``LLVMCreateDisasm()`` to create a disassembler context the
+optional output is enable with this call:
+
+.. code-block:: c
+
+ LLVMSetDisasmOptions(DC, LLVMDisassembler_Option_UseMarkup);
+
+Then subsequent calls to ``LLVMDisasmInstruction()`` will return output strings
+with the marked up annotations.
+
+Instruction Annotations
+=======================
+
+.. _contextual markups:
+
+Contextual markups
+------------------
+
+Annoated assembly display will supply contextual markup to help clients more
+efficiently implement things like pretty printers. Most markup will be target
+independent, so clients can effectively provide good display without any target
+specific knowledge.
+
+Annotated assembly goes through the normal instruction printer, but optionally
+includes contextual tags on portions of the instruction string. An annotation
+is any '<' '>' delimited section of text(1).
+
+.. code-block:: bat
+
+ annotation: '<' tag-name tag-modifier-list ':' annotated-text '>'
+ tag-name: identifier
+ tag-modifier-list: comma delimited identifier list
+
+The tag-name is an identifier which gives the type of the annotation. For the
+first pass, this will be very simple, with memory references, registers, and
+immediates having the tag names "mem", "reg", and "imm", respectively.
+
+The tag-modifier-list is typically additional target-specific context, such as
+register class.
+
+Clients should accept and ignore any tag-names or tag-modifiers they do not
+understand, allowing the annotations to grow in richness without breaking older
+clients.
+
+For example, a possible annotation of an ARM load of a stack-relative location
+might be annotated as:
+
+.. code-block:: nasm
+
+ ldr <reg gpr:r0>, <mem regoffset:[<reg gpr:sp>, <imm:#4>]>
+
+
+1: For assembly dialects in which '<' and/or '>' are legal tokens, a literal token is escaped by following immediately with a repeat of the character. For example, a literal '<' character is output as '<<' in an annotated assembly string.
+
+C API Details
+-------------
+
+The intended consumers of this information use the C API, therefore the new C
+API function for the disassembler will be added to provide an option to produce
+disassembled instructions with annotations, ``LLVMSetDisasmOptions()`` and the
+``LLVMDisassembler_Option_UseMarkup`` option (see above).
Added: www-releases/trunk/3.6.2/docs/_sources/MergeFunctions.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/MergeFunctions.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/MergeFunctions.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/MergeFunctions.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,802 @@
+=================================
+MergeFunctions pass, how it works
+=================================
+
+.. contents::
+ :local:
+
+Introduction
+============
+Sometimes code contains equal functions, or functions that does exactly the same
+thing even though they are non-equal on the IR level (e.g.: multiplication on 2
+and 'shl 1'). It could happen due to several reasons: mainly, the usage of
+templates and automatic code generators. Though, sometimes user itself could
+write the same thing twice :-)
+
+The main purpose of this pass is to recognize such functions and merge them.
+
+Why would I want to read this document?
+---------------------------------------
+Document is the extension to pass comments and describes the pass logic. It
+describes algorithm that is used in order to compare functions, it also
+explains how we could combine equal functions correctly, keeping module valid.
+
+Material is brought in top-down form, so reader could start learn pass from
+ideas and end up with low-level algorithm details, thus preparing him for
+reading the sources.
+
+So main goal is do describe algorithm and logic here; the concept. This document
+is good for you, if you *don't want* to read the source code, but want to
+understand pass algorithms. Author tried not to repeat the source-code and
+cover only common cases, and thus avoid cases when after minor code changes we
+need to update this document.
+
+
+What should I know to be able to follow along with this document?
+-----------------------------------------------------------------
+
+Reader should be familiar with common compile-engineering principles and LLVM
+code fundamentals. In this article we suppose reader is familiar with
+`Single Static Assingment <http://en.wikipedia.org/wiki/Static_single_assignment_form>`_
+concepts. Understanding of
+`IR structure <http://llvm.org/docs/LangRef.html#high-level-structure>`_ is
+also important.
+
+We will use such terms as
+"`module <http://llvm.org/docs/LangRef.html#high-level-structure>`_",
+"`function <http://llvm.org/docs/ProgrammersManual.html#the-function-class>`_",
+"`basic block <http://en.wikipedia.org/wiki/Basic_block>`_",
+"`user <http://llvm.org/docs/ProgrammersManual.html#the-user-class>`_",
+"`value <http://llvm.org/docs/ProgrammersManual.html#the-value-class>`_",
+"`instruction <http://llvm.org/docs/ProgrammersManual.html#the-instruction-class>`_".
+
+As a good start point, Kaleidoscope tutorial could be used:
+
+:doc:`tutorial/index`
+
+Especially it's important to understand chapter 3 of tutorial:
+
+:doc:`tutorial/LangImpl3`
+
+Reader also should know how passes work in LLVM, he could use next article as a
+reference and start point here:
+
+:doc:`WritingAnLLVMPass`
+
+What else? Well perhaps reader also should have some experience in LLVM pass
+debugging and bug-fixing.
+
+What I gain by reading this document?
+-------------------------------------
+Main purpose is to provide reader with comfortable form of algorithms
+description, namely the human reading text. Since it could be hard to
+understand algorithm straight from the source code: pass uses some principles
+that have to be explained first.
+
+Author wishes to everybody to avoid case, when you read code from top to bottom
+again and again, and yet you don't understand why we implemented it that way.
+
+We hope that after this article reader could easily debug and improve
+MergeFunctions pass and thus help LLVM project.
+
+Narrative structure
+-------------------
+Article consists of three parts. First part explains pass functionality on the
+top-level. Second part describes the comparison procedure itself. The third
+part describes the merging process.
+
+In every part author also tried to put the contents into the top-down form.
+First, the top-level methods will be described, while the terminal ones will be
+at the end, in the tail of each part. If reader will see the reference to the
+method that wasn't described yet, he will find its description a bit below.
+
+Basics
+======
+
+How to do it?
+-------------
+Do we need to merge functions? Obvious thing is: yes that's a quite possible
+case, since usually we *do* have duplicates. And it would be good to get rid of
+them. But how to detect such a duplicates? The idea is next: we split functions
+onto small bricks (parts), then we compare "bricks" amount, and if it equal,
+compare "bricks" themselves, and then do our conclusions about functions
+themselves.
+
+What the difference it could be? For example, on machine with 64-bit pointers
+(let's assume we have only one address space), one function stores 64-bit
+integer, while another one stores a pointer. So if the target is a machine
+mentioned above, and if functions are identical, except the parameter type (we
+could consider it as a part of function type), then we can treat ``uint64_t``
+and``void*`` as equal.
+
+It was just an example; possible details are described a bit below.
+
+As another example reader may imagine two more functions. First function
+performs multiplication on 2, while the second one performs arithmetic right
+shift on 1.
+
+Possible solutions
+^^^^^^^^^^^^^^^^^^
+Let's briefly consider possible options about how and what we have to implement
+in order to create full-featured functions merging, and also what it would
+meant for us.
+
+Equal functions detection, obviously supposes "detector" method to be
+implemented, latter should answer the question "whether functions are equal".
+This "detector" method consists of tiny "sub-detectors", each of them answers
+exactly the same question, but for function parts.
+
+As the second step, we should merge equal functions. So it should be a "merger"
+method. "Merger" accepts two functions *F1* and *F2*, and produces *F1F2*
+function, the result of merging.
+
+Having such a routines in our hands, we can process whole module, and merge all
+equal functions.
+
+In this case, we have to compare every function with every another function. As
+reader could notice, this way seems to be quite expensive. Of course we could
+introduce hashing and other helpers, but it is still just an optimization, and
+thus the level of O(N*N) complexity.
+
+Can we reach another level? Could we introduce logarithmical search, or random
+access lookup? The answer is: "yes".
+
+Random-access
+"""""""""""""
+How it could be done? Just convert each function to number, and gather all of
+them in special hash-table. Functions with equal hash are equal. Good hashing
+means, that every function part must be taken into account. That means we have
+to convert every function part into some number, and then add it into hash.
+Lookup-up time would be small, but such approach adds some delay due to hashing
+routine.
+
+Logarithmical search
+""""""""""""""""""""
+We could introduce total ordering among the functions set, once we had it we
+could then implement a logarithmical search. Lookup time still depends on N,
+but adds a little of delay (*log(N)*).
+
+Present state
+"""""""""""""
+Both of approaches (random-access and logarithmical) has been implemented and
+tested. And both of them gave a very good improvement. And what was most
+surprising, logarithmical search was faster; sometimes up to 15%. Hashing needs
+some extra CPU time, and it is the main reason why it works slower; in most of
+cases total "hashing" time was greater than total "logarithmical-search" time.
+
+So, preference has been granted to the "logarithmical search".
+
+Though in the case of need, *logarithmical-search* (read "total-ordering") could
+be used as a milestone on our way to the *random-access* implementation.
+
+Every comparison is based either on the numbers or on flags comparison. In
+*random-access* approach we could use the same comparison algorithm. During
+comparison we exit once we find the difference, but here we might have to scan
+whole function body every time (note, it could be slower). Like in
+"total-ordering", we will track every numbers and flags, but instead of
+comparison, we should get numbers sequence and then create the hash number. So,
+once again, *total-ordering* could be considered as a milestone for even faster
+(in theory) random-access approach.
+
+MergeFunctions, main fields and runOnModule
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+There are two most important fields in class:
+
+``FnTree`` â the set of all unique functions. It keeps items that couldn't be
+merged with each other. It is defined as:
+
+``std::set<FunctionNode> FnTree;``
+
+Here ``FunctionNode`` is a wrapper for ``llvm::Function`` class, with
+implemented â<â operator among the functions set (below we explain how it works
+exactly; this is a key point in fast functions comparison).
+
+``Deferred`` â merging process can affect bodies of functions that are in
+``FnTree`` already. Obviously such functions should be rechecked again. In this
+case we remove them from ``FnTree``, and mark them as to be rescanned, namely
+put them into ``Deferred`` list.
+
+runOnModule
+"""""""""""
+The algorithm is pretty simple:
+
+1. Put all module's functions into the *worklist*.
+
+2. Scan *worklist*'s functions twice: first enumerate only strong functions and
+then only weak ones:
+
+ 2.1. Loop body: take function from *worklist* (call it *FCur*) and try to
+ insert it into *FnTree*: check whether *FCur* is equal to one of functions
+ in *FnTree*. If there *is* equal function in *FnTree* (call it *FExists*):
+ merge function *FCur* with *FExists*. Otherwise add function from *worklist*
+ to *FnTree*.
+
+3. Once *worklist* scanning and merging operations is complete, check *Deferred*
+list. If it is not empty: refill *worklist* contents with *Deferred* list and
+do step 2 again, if *Deferred* is empty, then exit from method.
+
+Comparison and logarithmical search
+"""""""""""""""""""""""""""""""""""
+Let's recall our task: for every function *F* from module *M*, we have to find
+equal functions *F`* in shortest time, and merge them into the single function.
+
+Defining total ordering among the functions set allows to organize functions
+into the binary tree. The lookup procedure complexity would be estimated as
+O(log(N)) in this case. But how to define *total-ordering*?
+
+We have to introduce a single rule applicable to every pair of functions, and
+following this rule then evaluate which of them is greater. What kind of rule
+it could be? Let's declare it as "compare" method, that returns one of 3
+possible values:
+
+-1, left is *less* than right,
+
+0, left and right are *equal*,
+
+1, left is *greater* than right.
+
+Of course it means, that we have to maintain
+*strict and non-strict order relation properties*:
+
+* reflexivity (``a <= a``, ``a == a``, ``a >= a``),
+* antisymmetry (if ``a <= b`` and ``b <= a`` then ``a == b``),
+* transitivity (``a <= b`` and ``b <= c``, then ``a <= c``)
+* asymmetry (if ``a < b``, then ``a > b`` or ``a == b``).
+
+As it was mentioned before, comparison routine consists of
+"sub-comparison-routines", each of them also consists
+"sub-comparison-routines", and so on, finally it ends up with a primitives
+comparison.
+
+Below, we will use the next operations:
+
+#. ``cmpNumbers(number1, number2)`` is method that returns -1 if left is less
+ than right; 0, if left and right are equal; and 1 otherwise.
+
+#. ``cmpFlags(flag1, flag2)`` is hypothetical method that compares two flags.
+ The logic is the same as in ``cmpNumbers``, where ``true`` is 1, and
+ ``false`` is 0.
+
+The rest of article is based on *MergeFunctions.cpp* source code
+(*<llvm_dir>/lib/Transforms/IPO/MergeFunctions.cpp*). We would like to ask
+reader to keep this file open nearby, so we could use it as a reference for
+further explanations.
+
+Now we're ready to proceed to the next chapter and see how it works.
+
+Functions comparison
+====================
+At first, let's define how exactly we compare complex objects.
+
+Complex objects comparison (function, basic-block, etc) is mostly based on its
+sub-objects comparison results. So it is similar to the next "tree" objects
+comparison:
+
+#. For two trees *T1* and *T2* we perform *depth-first-traversal* and have
+ two sequences as a product: "*T1Items*" and "*T2Items*".
+
+#. Then compare chains "*T1Items*" and "*T2Items*" in
+ most-significant-item-first order. Result of items comparison would be the
+ result of *T1* and *T2* comparison itself.
+
+FunctionComparator::compare(void)
+---------------------------------
+Brief look at the source code tells us, that comparison starts in
+â``int FunctionComparator::compare(void)``â method.
+
+1. First parts to be compared are function's attributes and some properties that
+outsides âattributesâ term, but still could make function different without
+changing its body. This part of comparison is usually done within simple
+*cmpNumbers* or *cmpFlags* operations (e.g.
+``cmpFlags(F1->hasGC(), F2->hasGC())``). Below is full list of function's
+properties to be compared on this stage:
+
+ * *Attributes* (those are returned by ``Function::getAttributes()``
+ method).
+
+ * *GC*, for equivalence, *RHS* and *LHS* should be both either without
+ *GC* or with the same one.
+
+ * *Section*, just like a *GC*: *RHS* and *LHS* should be defined in the
+ same section.
+
+ * *Variable arguments*. *LHS* and *RHS* should be both either with or
+ without *var-args*.
+
+ * *Calling convention* should be the same.
+
+2. Function type. Checked by ``FunctionComparator::cmpType(Type*, Type*)``
+method. It checks return type and parameters type; the method itself will be
+described later.
+
+3. Associate function formal parameters with each other. Then comparing function
+bodies, if we see the usage of *LHS*'s *i*-th argument in *LHS*'s body, then,
+we want to see usage of *RHS*'s *i*-th argument at the same place in *RHS*'s
+body, otherwise functions are different. On this stage we grant the preference
+to those we met later in function body (value we met first would be *less*).
+This is done by â``FunctionComparator::cmpValues(const Value*, const Value*)``â
+method (will be described a bit later).
+
+4. Function body comparison. As it written in method comments:
+
+âWe do a CFG-ordered walk since the actual ordering of the blocks in the linked
+list is immaterial. Our walk starts at the entry block for both functions, then
+takes each block from each terminator in order. As an artifact, this also means
+that unreachable blocks are ignored.â
+
+So, using this walk we get BBs from *left* and *right* in the same order, and
+compare them by â``FunctionComparator::compare(const BasicBlock*, const
+BasicBlock*)``â method.
+
+We also associate BBs with each other, like we did it with function formal
+arguments (see ``cmpValues`` method below).
+
+FunctionComparator::cmpType
+---------------------------
+Consider how types comparison works.
+
+1. Coerce pointer to integer. If left type is a pointer, try to coerce it to the
+integer type. It could be done if its address space is 0, or if address spaces
+are ignored at all. Do the same thing for the right type.
+
+2. If left and right types are equal, return 0. Otherwise we need to give
+preference to one of them. So proceed to the next step.
+
+3. If types are of different kind (different type IDs). Return result of type
+IDs comparison, treating them as a numbers (use ``cmpNumbers`` operation).
+
+4. If types are vectors or integers, return result of their pointers comparison,
+comparing them as numbers.
+
+5. Check whether type ID belongs to the next group (call it equivalent-group):
+
+ * Void
+
+ * Float
+
+ * Double
+
+ * X86_FP80
+
+ * FP128
+
+ * PPC_FP128
+
+ * Label
+
+ * Metadata.
+
+ If ID belongs to group above, return 0. Since it's enough to see that
+ types has the same ``TypeID``. No additional information is required.
+
+6. Left and right are pointers. Return result of address space comparison
+(numbers comparison).
+
+7. Complex types (structures, arrays, etc.). Follow complex objects comparison
+technique (see the very first paragraph of this chapter). Both *left* and
+*right* are to be expanded and their element types will be checked the same
+way. If we get -1 or 1 on some stage, return it. Otherwise return 0.
+
+8. Steps 1-6 describe all the possible cases, if we passed steps 1-6 and didn't
+get any conclusions, then invoke ``llvm_unreachable``, since it's quite
+unexpectable case.
+
+cmpValues(const Value*, const Value*)
+-------------------------------------
+Method that compares local values.
+
+This method gives us an answer on a very curious quesion: whether we could treat
+local values as equal, and which value is greater otherwise. It's better to
+start from example:
+
+Consider situation when we're looking at the same place in left function "*FL*"
+and in right function "*FR*". And every part of *left* place is equal to the
+corresponding part of *right* place, and (!) both parts use *Value* instances,
+for example:
+
+.. code-block:: llvm
+
+ instr0 i32 %LV ; left side, function FL
+ instr0 i32 %RV ; right side, function FR
+
+So, now our conclusion depends on *Value* instances comparison.
+
+Main purpose of this method is to determine relation between such values.
+
+What we expect from equal functions? At the same place, in functions "*FL*" and
+"*FR*" we expect to see *equal* values, or values *defined* at the same place
+in "*FL*" and "*FR*".
+
+Consider small example here:
+
+.. code-block:: llvm
+
+ define void %f(i32 %pf0, i32 %pf1) {
+ instr0 i32 %pf0 instr1 i32 %pf1 instr2 i32 123
+ }
+
+.. code-block:: llvm
+
+ define void %g(i32 %pg0, i32 %pg1) {
+ instr0 i32 %pg0 instr1 i32 %pg0 instr2 i32 123
+ }
+
+In this example, *pf0* is associated with *pg0*, *pf1* is associated with *pg1*,
+and we also declare that *pf0* < *pf1*, and thus *pg0* < *pf1*.
+
+Instructions with opcode "*instr0*" would be *equal*, since their types and
+opcodes are equal, and values are *associated*.
+
+Instruction with opcode "*instr1*" from *f* is *greater* than instruction with
+opcode "*instr1*" from *g*; here we have equal types and opcodes, but "*pf1* is
+greater than "*pg0*".
+
+And instructions with opcode "*instr2*" are equal, because their opcodes and
+types are equal, and the same constant is used as a value.
+
+What we assiciate in cmpValues?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+* Function arguments. *i*-th argument from left function associated with
+ *i*-th argument from right function.
+* BasicBlock instances. In basic-block enumeration loop we associate *i*-th
+ BasicBlock from the left function with *i*-th BasicBlock from the right
+ function.
+* Instructions.
+* Instruction operands. Note, we can meet *Value* here we have never seen
+ before. In this case it is not a function argument, nor *BasicBlock*, nor
+ *Instruction*. It is global value. It is constant, since its the only
+ supposed global here. Method also compares:
+* Constants that are of the same type.
+* If right constant could be losslessly bit-casted to the left one, then we
+ also compare them.
+
+How to implement cmpValues?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+*Association* is a case of equality for us. We just treat such values as equal.
+But, in general, we need to implement antisymmetric relation. As it was
+mentioned above, to understand what is *less*, we can use order in which we
+meet values. If both of values has the same order in function (met at the same
+time), then treat values as *associated*. Otherwise â it depends on who was
+first.
+
+Every time we run top-level compare method, we initialize two identical maps
+(one for the left side, another one for the right side):
+
+``map<Value, int> sn_mapL, sn_mapR;``
+
+The key of the map is the *Value* itself, the *value* â is its order (call it
+*serial number*).
+
+To add value *V* we need to perform the next procedure:
+
+``sn_map.insert(std::make_pair(V, sn_map.size()));``
+
+For the first *Value*, map will return *0*, for second *Value* map will return
+*1*, and so on.
+
+Then we can check whether left and right values met at the same time with simple
+comparison:
+
+``cmpNumbers(sn_mapL[Left], sn_mapR[Right]);``
+
+Of course, we can combine insertion and comparison:
+
+.. code-block:: c++
+
+ std::pair<iterator, bool>
+ LeftRes = sn_mapL.insert(std::make_pair(Left, sn_mapL.size())), RightRes
+ = sn_mapR.insert(std::make_pair(Right, sn_mapR.size()));
+ return cmpNumbers(LeftRes.first->second, RightRes.first->second);
+
+Let's look, how whole method could be implemented.
+
+1. we have to start from the bad news. Consider function self and
+cross-referencing cases:
+
+.. code-block:: c++
+
+ // self-reference unsigned fact0(unsigned n) { return n > 1 ? n
+ * fact0(n-1) : 1; } unsigned fact1(unsigned n) { return n > 1 ? n *
+ fact1(n-1) : 1; }
+
+ // cross-reference unsigned ping(unsigned n) { return n!= 0 ? pong(n-1) : 0;
+ } unsigned pong(unsigned n) { return n!= 0 ? ping(n-1) : 0; }
+
+..
+
+ This comparison has been implemented in initial *MergeFunctions* pass
+ version. But, unfortunately, it is not transitive. And this is the only case
+ we can't convert to less-equal-greater comparison. It is a seldom case, 4-5
+ functions of 10000 (checked on test-suite), and, we hope, reader would
+ forgive us for such a sacrifice in order to get the O(log(N)) pass time.
+
+2. If left/right *Value* is a constant, we have to compare them. Return 0 if it
+is the same constant, or use ``cmpConstants`` method otherwise.
+
+3. If left/right is *InlineAsm* instance. Return result of *Value* pointers
+comparison.
+
+4. Explicit association of *L* (left value) and *R* (right value). We need to
+find out whether values met at the same time, and thus are *associated*. Or we
+need to put the rule: when we treat *L* < *R*. Now it is easy: just return
+result of numbers comparison:
+
+.. code-block:: c++
+
+ std::pair<iterator, bool>
+ LeftRes = sn_mapL.insert(std::make_pair(Left, sn_mapL.size())),
+ RightRes = sn_mapR.insert(std::make_pair(Right, sn_mapR.size()));
+ if (LeftRes.first->second == RightRes.first->second) return 0;
+ if (LeftRes.first->second < RightRes.first->second) return -1;
+ return 1;
+
+Now when *cmpValues* returns 0, we can proceed comparison procedure. Otherwise,
+if we get (-1 or 1), we need to pass this result to the top level, and finish
+comparison procedure.
+
+cmpConstants
+------------
+Performs constants comparison as follows:
+
+1. Compare constant types using ``cmpType`` method. If result is -1 or 1, goto
+step 2, otherwise proceed to step 3.
+
+2. If types are different, we still can check whether constants could be
+losslessly bitcasted to each other. The further explanation is modification of
+``canLosslesslyBitCastTo`` method.
+
+ 2.1 Check whether constants are of the first class types
+ (``isFirstClassType`` check):
+
+ 2.1.1. If both constants are *not* of the first class type: return result
+ of ``cmpType``.
+
+ 2.1.2. Otherwise, if left type is not of the first class, return -1. If
+ right type is not of the first class, return 1.
+
+ 2.1.3. If both types are of the first class type, proceed to the next step
+ (2.1.3.1).
+
+ 2.1.3.1. If types are vectors, compare their bitwidth using the
+ *cmpNumbers*. If result is not 0, return it.
+
+ 2.1.3.2. Different types, but not a vectors:
+
+ * if both of them are pointers, good for us, we can proceed to step 3.
+ * if one of types is pointer, return result of *isPointer* flags
+ comparison (*cmpFlags* operation).
+ * otherwise we have no methods to prove bitcastability, and thus return
+ result of types comparison (-1 or 1).
+
+Steps below are for the case when types are equal, or case when constants are
+bitcastable:
+
+3. One of constants is a "*null*" value. Return the result of
+``cmpFlags(L->isNullValue, R->isNullValue)`` comparison.
+
+4. Compare value IDs, and return result if it is not 0:
+
+.. code-block:: c++
+
+ if (int Res = cmpNumbers(L->getValueID(), R->getValueID()))
+ return Res;
+
+5. Compare the contents of constants. The comparison depends on kind of
+constants, but on this stage it is just a lexicographical comparison. Just see
+how it was described in the beginning of "*Functions comparison*" paragraph.
+Mathematically it is equal to the next case: we encode left constant and right
+constant (with similar way *bitcode-writer* does). Then compare left code
+sequence and right code sequence.
+
+compare(const BasicBlock*, const BasicBlock*)
+---------------------------------------------
+Compares two *BasicBlock* instances.
+
+It enumerates instructions from left *BB* and right *BB*.
+
+1. It assigns serial numbers to the left and right instructions, using
+``cmpValues`` method.
+
+2. If one of left or right is *GEP* (``GetElementPtr``), then treat *GEP* as
+greater than other instructions, if both instructions are *GEPs* use ``cmpGEP``
+method for comparison. If result is -1 or 1, pass it to the top-level
+comparison (return it).
+
+ 3.1. Compare operations. Call ``cmpOperation`` method. If result is -1 or
+ 1, return it.
+
+ 3.2. Compare number of operands, if result is -1 or 1, return it.
+
+ 3.3. Compare operands themselves, use ``cmpValues`` method. Return result
+ if it is -1 or 1.
+
+ 3.4. Compare type of operands, using ``cmpType`` method. Return result if
+ it is -1 or 1.
+
+ 3.5. Proceed to the next instruction.
+
+4. We can finish instruction enumeration in 3 cases:
+
+ 4.1. We reached the end of both left and right basic-blocks. We didn't
+ exit on steps 1-3, so contents is equal, return 0.
+
+ 4.2. We have reached the end of the left basic-block. Return -1.
+
+ 4.3. Return 1 (the end of the right basic block).
+
+cmpGEP
+------
+Compares two GEPs (``getelementptr`` instructions).
+
+It differs from regular operations comparison with the only thing: possibility
+to use ``accumulateConstantOffset`` method.
+
+So, if we get constant offset for both left and right *GEPs*, then compare it as
+numbers, and return comparison result.
+
+Otherwise treat it like a regular operation (see previous paragraph).
+
+cmpOperation
+------------
+Compares instruction opcodes and some important operation properties.
+
+1. Compare opcodes, if it differs return the result.
+
+2. Compare number of operands. If it differs â return the result.
+
+3. Compare operation types, use *cmpType*. All the same â if types are
+different, return result.
+
+4. Compare *subclassOptionalData*, get it with ``getRawSubclassOptionalData``
+method, and compare it like a numbers.
+
+5. Compare operand types.
+
+6. For some particular instructions check equivalence (relation in our case) of
+some significant attributes. For example we have to compare alignment for
+``load`` instructions.
+
+O(log(N))
+---------
+Methods described above implement order relationship. And latter, could be used
+for nodes comparison in a binary tree. So we can organize functions set into
+the binary tree and reduce the cost of lookup procedure from
+O(N*N) to O(log(N)).
+
+Merging process, mergeTwoFunctions
+==================================
+Once *MergeFunctions* detected that current function (*G*) is equal to one that
+were analyzed before (function *F*) it calls ``mergeTwoFunctions(Function*,
+Function*)``.
+
+Operation affects ``FnTree`` contents with next way: *F* will stay in
+``FnTree``. *G* being equal to *F* will not be added to ``FnTree``. Calls of
+*G* would be replaced with something else. It changes bodies of callers. So,
+functions that calls *G* would be put into ``Deferred`` set and removed from
+``FnTree``, and analyzed again.
+
+The approach is next:
+
+1. Most wished case: when we can use alias and both of *F* and *G* are weak. We
+make both of them with aliases to the third strong function *H*. Actually *H*
+is *F*. See below how it's made (but it's better to look straight into the
+source code). Well, this is a case when we can just replace *G* with *F*
+everywhere, we use ``replaceAllUsesWith`` operation here (*RAUW*).
+
+2. *F* could not be overridden, while *G* could. It would be good to do the
+next: after merging the places where overridable function were used, still use
+overridable stub. So try to make *G* alias to *F*, or create overridable tail
+call wrapper around *F* and replace *G* with that call.
+
+3. Neither *F* nor *G* could be overridden. We can't use *RAUW*. We can just
+change the callers: call *F* instead of *G*. That's what
+``replaceDirectCallers`` does.
+
+Below is detailed body description.
+
+If âFâ may be overridden
+------------------------
+As follows from ``mayBeOverridden`` comments: âwhether the definition of this
+global may be replaced by something non-equivalent at link timeâ. If so, thats
+ok: we can use alias to *F* instead of *G* or change call instructions itself.
+
+HasGlobalAliases, removeUsers
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+First consider the case when we have global aliases of one function name to
+another. Our purpose is make both of them with aliases to the third strong
+function. Though if we keep *F* alive and without major changes we can leave it
+in ``FnTree``. Try to combine these two goals.
+
+Do stub replacement of *F* itself with an alias to *F*.
+
+1. Create stub function *H*, with the same name and attributes like function
+*F*. It takes maximum alignment of *F* and *G*.
+
+2. Replace all uses of function *F* with uses of function *H*. It is the two
+steps procedure instead. First of all, we must take into account, all functions
+from whom *F* is called would be changed: since we change the call argument
+(from *F* to *H*). If so we must to review these caller functions again after
+this procedure. We remove callers from ``FnTree``, method with name
+``removeUsers(F)`` does that (don't confuse with ``replaceAllUsesWith``):
+
+ 2.1. ``Inside removeUsers(Value*
+ V)`` we go through the all values that use value *V* (or *F* in our context).
+ If value is instruction, we go to function that holds this instruction and
+ mark it as to-be-analyzed-again (put to ``Deferred`` set), we also remove
+ caller from ``FnTree``.
+
+ 2.2. Now we can do the replacement: call ``F->replaceAllUsesWith(H)``.
+
+3. *H* (that now "officially" plays *F*'s role) is replaced with alias to *F*.
+Do the same with *G*: replace it with alias to *F*. So finally everywhere *F*
+was used, we use *H* and it is alias to *F*, and everywhere *G* was used we
+also have alias to *F*.
+
+4. Set *F* linkage to private. Make it strong :-)
+
+No global aliases, replaceDirectCallers
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+If global aliases are not supported. We call ``replaceDirectCallers`` then. Just
+go through all calls of *G* and replace it with calls of *F*. If you look into
+method you will see that it scans all uses of *G* too, and if use is callee (if
+user is call instruction and *G* is used as what to be called), we replace it
+with use of *F*.
+
+If âFâ could not be overridden, fix it!
+"""""""""""""""""""""""""""""""""""""""
+
+We call ``writeThunkOrAlias(Function *F, Function *G)``. Here we try to replace
+*G* with alias to *F* first. Next conditions are essential:
+
+* target should support global aliases,
+* the address itself of *G* should be not significant, not named and not
+ referenced anywhere,
+* function should come with external, local or weak linkage.
+
+Otherwise we write thunk: some wrapper that has *G's* interface and calls *F*,
+so *G* could be replaced with this wrapper.
+
+*writeAlias*
+
+As follows from *llvm* reference:
+
+âAliases act as *second name* for the aliasee valueâ. So we just want to create
+second name for *F* and use it instead of *G*:
+
+1. create global alias itself (*GA*),
+
+2. adjust alignment of *F* so it must be maximum of current and *G's* alignment;
+
+3. replace uses of *G*:
+
+ 3.1. first mark all callers of *G* as to-be-analyzed-again, using
+ ``removeUsers`` method (see chapter above),
+
+ 3.2. call ``G->replaceAllUsesWith(GA)``.
+
+4. Get rid of *G*.
+
+*writeThunk*
+
+As it written in method comments:
+
+âReplace G with a simple tail call to bitcast(F). Also replace direct uses of G
+with bitcast(F). Deletes G.â
+
+In general it does the same as usual when we want to replace callee, except the
+first point:
+
+1. We generate tail call wrapper around *F*, but with interface that allows use
+it instead of *G*.
+
+2. âAs-usualâ: ``removeUsers`` and ``replaceAllUsesWith`` then.
+
+3. Get rid of *G*.
+
+That's it.
+==========
+We have described how to detect equal functions, and how to merge them, and in
+first chapter we have described how it works all-together. Author hopes, reader
+have some picture from now, and it helps him improve and debug Âthis pass.
+
+Reader is welcomed to send us any questions and proposals ;-)
Added: www-releases/trunk/3.6.2/docs/_sources/NVPTXUsage.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/NVPTXUsage.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/NVPTXUsage.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/NVPTXUsage.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,980 @@
+=============================
+User Guide for NVPTX Back-end
+=============================
+
+.. contents::
+ :local:
+ :depth: 3
+
+
+Introduction
+============
+
+To support GPU programming, the NVPTX back-end supports a subset of LLVM IR
+along with a defined set of conventions used to represent GPU programming
+concepts. This document provides an overview of the general usage of the back-
+end, including a description of the conventions used and the set of accepted
+LLVM IR.
+
+.. note::
+
+ This document assumes a basic familiarity with CUDA and the PTX
+ assembly language. Information about the CUDA Driver API and the PTX assembly
+ language can be found in the `CUDA documentation
+ <http://docs.nvidia.com/cuda/index.html>`_.
+
+
+
+Conventions
+===========
+
+Marking Functions as Kernels
+----------------------------
+
+In PTX, there are two types of functions: *device functions*, which are only
+callable by device code, and *kernel functions*, which are callable by host
+code. By default, the back-end will emit device functions. Metadata is used to
+declare a function as a kernel function. This metadata is attached to the
+``nvvm.annotations`` named metadata object, and has the following format:
+
+.. code-block:: llvm
+
+ !0 = metadata !{<function-ref>, metadata !"kernel", i32 1}
+
+The first parameter is a reference to the kernel function. The following
+example shows a kernel function calling a device function in LLVM IR. The
+function ``@my_kernel`` is callable from host code, but ``@my_fmad`` is not.
+
+.. code-block:: llvm
+
+ define float @my_fmad(float %x, float %y, float %z) {
+ %mul = fmul float %x, %y
+ %add = fadd float %mul, %z
+ ret float %add
+ }
+
+ define void @my_kernel(float* %ptr) {
+ %val = load float* %ptr
+ %ret = call float @my_fmad(float %val, float %val, float %val)
+ store float %ret, float* %ptr
+ ret void
+ }
+
+ !nvvm.annotations = !{!1}
+ !1 = metadata !{void (float*)* @my_kernel, metadata !"kernel", i32 1}
+
+When compiled, the PTX kernel functions are callable by host-side code.
+
+
+.. _address_spaces:
+
+Address Spaces
+--------------
+
+The NVPTX back-end uses the following address space mapping:
+
+ ============= ======================
+ Address Space Memory Space
+ ============= ======================
+ 0 Generic
+ 1 Global
+ 2 Internal Use
+ 3 Shared
+ 4 Constant
+ 5 Local
+ ============= ======================
+
+Every global variable and pointer type is assigned to one of these address
+spaces, with 0 being the default address space. Intrinsics are provided which
+can be used to convert pointers between the generic and non-generic address
+spaces.
+
+As an example, the following IR will define an array ``@g`` that resides in
+global device memory.
+
+.. code-block:: llvm
+
+ @g = internal addrspace(1) global [4 x i32] [ i32 0, i32 1, i32 2, i32 3 ]
+
+LLVM IR functions can read and write to this array, and host-side code can
+copy data to it by name with the CUDA Driver API.
+
+Note that since address space 0 is the generic space, it is illegal to have
+global variables in address space 0. Address space 0 is the default address
+space in LLVM, so the ``addrspace(N)`` annotation is *required* for global
+variables.
+
+
+Triples
+-------
+
+The NVPTX target uses the module triple to select between 32/64-bit code
+generation and the driver-compiler interface to use. The triple architecture
+can be one of ``nvptx`` (32-bit PTX) or ``nvptx64`` (64-bit PTX). The
+operating system should be one of ``cuda`` or ``nvcl``, which determines the
+interface used by the generated code to communicate with the driver. Most
+users will want to use ``cuda`` as the operating system, which makes the
+generated PTX compatible with the CUDA Driver API.
+
+Example: 32-bit PTX for CUDA Driver API: ``nvptx-nvidia-cuda``
+
+Example: 64-bit PTX for CUDA Driver API: ``nvptx64-nvidia-cuda``
+
+
+
+.. _nvptx_intrinsics:
+
+NVPTX Intrinsics
+================
+
+Address Space Conversion
+------------------------
+
+'``llvm.nvvm.ptr.*.to.gen``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+These are overloaded intrinsics. You can use these on any pointer types.
+
+.. code-block:: llvm
+
+ declare i8* @llvm.nvvm.ptr.global.to.gen.p0i8.p1i8(i8 addrspace(1)*)
+ declare i8* @llvm.nvvm.ptr.shared.to.gen.p0i8.p3i8(i8 addrspace(3)*)
+ declare i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8(i8 addrspace(4)*)
+ declare i8* @llvm.nvvm.ptr.local.to.gen.p0i8.p5i8(i8 addrspace(5)*)
+
+Overview:
+"""""""""
+
+The '``llvm.nvvm.ptr.*.to.gen``' intrinsics convert a pointer in a non-generic
+address space to a generic address space pointer.
+
+Semantics:
+""""""""""
+
+These intrinsics modify the pointer value to be a valid generic address space
+pointer.
+
+
+'``llvm.nvvm.ptr.gen.to.*``' Intrinsics
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+These are overloaded intrinsics. You can use these on any pointer types.
+
+.. code-block:: llvm
+
+ declare i8* @llvm.nvvm.ptr.gen.to.global.p1i8.p0i8(i8 addrspace(1)*)
+ declare i8* @llvm.nvvm.ptr.gen.to.shared.p3i8.p0i8(i8 addrspace(3)*)
+ declare i8* @llvm.nvvm.ptr.gen.to.constant.p4i8.p0i8(i8 addrspace(4)*)
+ declare i8* @llvm.nvvm.ptr.gen.to.local.p5i8.p0i8(i8 addrspace(5)*)
+
+Overview:
+"""""""""
+
+The '``llvm.nvvm.ptr.gen.to.*``' intrinsics convert a pointer in the generic
+address space to a pointer in the target address space. Note that these
+intrinsics are only useful if the address space of the target address space of
+the pointer is known. It is not legal to use address space conversion
+intrinsics to convert a pointer from one non-generic address space to another
+non-generic address space.
+
+Semantics:
+""""""""""
+
+These intrinsics modify the pointer value to be a valid pointer in the target
+non-generic address space.
+
+
+Reading PTX Special Registers
+-----------------------------
+
+'``llvm.nvvm.read.ptx.sreg.*``'
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+.. code-block:: llvm
+
+ declare i32 @llvm.nvvm.read.ptx.sreg.tid.x()
+ declare i32 @llvm.nvvm.read.ptx.sreg.tid.y()
+ declare i32 @llvm.nvvm.read.ptx.sreg.tid.z()
+ declare i32 @llvm.nvvm.read.ptx.sreg.ntid.x()
+ declare i32 @llvm.nvvm.read.ptx.sreg.ntid.y()
+ declare i32 @llvm.nvvm.read.ptx.sreg.ntid.z()
+ declare i32 @llvm.nvvm.read.ptx.sreg.ctaid.x()
+ declare i32 @llvm.nvvm.read.ptx.sreg.ctaid.y()
+ declare i32 @llvm.nvvm.read.ptx.sreg.ctaid.z()
+ declare i32 @llvm.nvvm.read.ptx.sreg.nctaid.x()
+ declare i32 @llvm.nvvm.read.ptx.sreg.nctaid.y()
+ declare i32 @llvm.nvvm.read.ptx.sreg.nctaid.z()
+ declare i32 @llvm.nvvm.read.ptx.sreg.warpsize()
+
+Overview:
+"""""""""
+
+The '``@llvm.nvvm.read.ptx.sreg.*``' intrinsics provide access to the PTX
+special registers, in particular the kernel launch bounds. These registers
+map in the following way to CUDA builtins:
+
+ ============ =====================================
+ CUDA Builtin PTX Special Register Intrinsic
+ ============ =====================================
+ ``threadId`` ``@llvm.nvvm.read.ptx.sreg.tid.*``
+ ``blockIdx`` ``@llvm.nvvm.read.ptx.sreg.ctaid.*``
+ ``blockDim`` ``@llvm.nvvm.read.ptx.sreg.ntid.*``
+ ``gridDim`` ``@llvm.nvvm.read.ptx.sreg.nctaid.*``
+ ============ =====================================
+
+
+Barriers
+--------
+
+'``llvm.nvvm.barrier0``'
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+.. code-block:: llvm
+
+ declare void @llvm.nvvm.barrier0()
+
+Overview:
+"""""""""
+
+The '``@llvm.nvvm.barrier0()``' intrinsic emits a PTX ``bar.sync 0``
+instruction, equivalent to the ``__syncthreads()`` call in CUDA.
+
+
+Other Intrinsics
+----------------
+
+For the full set of NVPTX intrinsics, please see the
+``include/llvm/IR/IntrinsicsNVVM.td`` file in the LLVM source tree.
+
+
+.. _libdevice:
+
+Linking with Libdevice
+======================
+
+The CUDA Toolkit comes with an LLVM bitcode library called ``libdevice`` that
+implements many common mathematical functions. This library can be used as a
+high-performance math library for any compilers using the LLVM NVPTX target.
+The library can be found under ``nvvm/libdevice/`` in the CUDA Toolkit and
+there is a separate version for each compute architecture.
+
+For a list of all math functions implemented in libdevice, see
+`libdevice Users Guide <http://docs.nvidia.com/cuda/libdevice-users-guide/index.html>`_.
+
+To accommodate various math-related compiler flags that can affect code
+generation of libdevice code, the library code depends on a special LLVM IR
+pass (``NVVMReflect``) to handle conditional compilation within LLVM IR. This
+pass looks for calls to the ``@__nvvm_reflect`` function and replaces them
+with constants based on the defined reflection parameters. Such conditional
+code often follows a pattern:
+
+.. code-block:: c++
+
+ float my_function(float a) {
+ if (__nvvm_reflect("FASTMATH"))
+ return my_function_fast(a);
+ else
+ return my_function_precise(a);
+ }
+
+The default value for all unspecified reflection parameters is zero.
+
+The ``NVVMReflect`` pass should be executed early in the optimization
+pipeline, immediately after the link stage. The ``internalize`` pass is also
+recommended to remove unused math functions from the resulting PTX. For an
+input IR module ``module.bc``, the following compilation flow is recommended:
+
+1. Save list of external functions in ``module.bc``
+2. Link ``module.bc`` with ``libdevice.compute_XX.YY.bc``
+3. Internalize all functions not in list from (1)
+4. Eliminate all unused internal functions
+5. Run ``NVVMReflect`` pass
+6. Run standard optimization pipeline
+
+.. note::
+
+ ``linkonce`` and ``linkonce_odr`` linkage types are not suitable for the
+ libdevice functions. It is possible to link two IR modules that have been
+ linked against libdevice using different reflection variables.
+
+Since the ``NVVMReflect`` pass replaces conditionals with constants, it will
+often leave behind dead code of the form:
+
+.. code-block:: llvm
+
+ entry:
+ ..
+ br i1 true, label %foo, label %bar
+ foo:
+ ..
+ bar:
+ ; Dead code
+ ..
+
+Therefore, it is recommended that ``NVVMReflect`` is executed early in the
+optimization pipeline before dead-code elimination.
+
+
+Reflection Parameters
+---------------------
+
+The libdevice library currently uses the following reflection parameters to
+control code generation:
+
+==================== ======================================================
+Flag Description
+==================== ======================================================
+``__CUDA_FTZ=[0,1]`` Use optimized code paths that flush subnormals to zero
+==================== ======================================================
+
+
+Invoking NVVMReflect
+--------------------
+
+To ensure that all dead code caused by the reflection pass is eliminated, it
+is recommended that the reflection pass is executed early in the LLVM IR
+optimization pipeline. The pass takes an optional mapping of reflection
+parameter name to an integer value. This mapping can be specified as either a
+command-line option to ``opt`` or as an LLVM ``StringMap<int>`` object when
+programmatically creating a pass pipeline.
+
+With ``opt``:
+
+.. code-block:: text
+
+ # opt -nvvm-reflect -nvvm-reflect-list=<var>=<value>,<var>=<value> module.bc -o module.reflect.bc
+
+
+With programmatic pass pipeline:
+
+.. code-block:: c++
+
+ extern ModulePass *llvm::createNVVMReflectPass(const StringMap<int>& Mapping);
+
+ StringMap<int> ReflectParams;
+ ReflectParams["__CUDA_FTZ"] = 1;
+ Passes.add(createNVVMReflectPass(ReflectParams));
+
+
+
+Executing PTX
+=============
+
+The most common way to execute PTX assembly on a GPU device is to use the CUDA
+Driver API. This API is a low-level interface to the GPU driver and allows for
+JIT compilation of PTX code to native GPU machine code.
+
+Initializing the Driver API:
+
+.. code-block:: c++
+
+ CUdevice device;
+ CUcontext context;
+
+ // Initialize the driver API
+ cuInit(0);
+ // Get a handle to the first compute device
+ cuDeviceGet(&device, 0);
+ // Create a compute device context
+ cuCtxCreate(&context, 0, device);
+
+JIT compiling a PTX string to a device binary:
+
+.. code-block:: c++
+
+ CUmodule module;
+ CUfunction funcion;
+
+ // JIT compile a null-terminated PTX string
+ cuModuleLoadData(&module, (void*)PTXString);
+
+ // Get a handle to the "myfunction" kernel function
+ cuModuleGetFunction(&function, module, "myfunction");
+
+For full examples of executing PTX assembly, please see the `CUDA Samples
+<https://developer.nvidia.com/cuda-downloads>`_ distribution.
+
+
+Common Issues
+=============
+
+ptxas complains of undefined function: __nvvm_reflect
+-----------------------------------------------------
+
+When linking with libdevice, the ``NVVMReflect`` pass must be used. See
+:ref:`libdevice` for more information.
+
+
+Tutorial: A Simple Compute Kernel
+=================================
+
+To start, let us take a look at a simple compute kernel written directly in
+LLVM IR. The kernel implements vector addition, where each thread computes one
+element of the output vector C from the input vectors A and B. To make this
+easier, we also assume that only a single CTA (thread block) will be launched,
+and that it will be one dimensional.
+
+
+The Kernel
+----------
+
+.. code-block:: llvm
+
+ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+ target triple = "nvptx64-nvidia-cuda"
+
+ ; Intrinsic to read X component of thread ID
+ declare i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind
+
+ define void @kernel(float addrspace(1)* %A,
+ float addrspace(1)* %B,
+ float addrspace(1)* %C) {
+ entry:
+ ; What is my ID?
+ %id = tail call i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind
+
+ ; Compute pointers into A, B, and C
+ %ptrA = getelementptr float addrspace(1)* %A, i32 %id
+ %ptrB = getelementptr float addrspace(1)* %B, i32 %id
+ %ptrC = getelementptr float addrspace(1)* %C, i32 %id
+
+ ; Read A, B
+ %valA = load float addrspace(1)* %ptrA, align 4
+ %valB = load float addrspace(1)* %ptrB, align 4
+
+ ; Compute C = A + B
+ %valC = fadd float %valA, %valB
+
+ ; Store back to C
+ store float %valC, float addrspace(1)* %ptrC, align 4
+
+ ret void
+ }
+
+ !nvvm.annotations = !{!0}
+ !0 = metadata !{void (float addrspace(1)*,
+ float addrspace(1)*,
+ float addrspace(1)*)* @kernel, metadata !"kernel", i32 1}
+
+
+We can use the LLVM ``llc`` tool to directly run the NVPTX code generator:
+
+.. code-block:: text
+
+ # llc -mcpu=sm_20 kernel.ll -o kernel.ptx
+
+
+.. note::
+
+ If you want to generate 32-bit code, change ``p:64:64:64`` to ``p:32:32:32``
+ in the module data layout string and use ``nvptx-nvidia-cuda`` as the
+ target triple.
+
+
+The output we get from ``llc`` (as of LLVM 3.4):
+
+.. code-block:: text
+
+ //
+ // Generated by LLVM NVPTX Back-End
+ //
+
+ .version 3.1
+ .target sm_20
+ .address_size 64
+
+ // .globl kernel
+ // @kernel
+ .visible .entry kernel(
+ .param .u64 kernel_param_0,
+ .param .u64 kernel_param_1,
+ .param .u64 kernel_param_2
+ )
+ {
+ .reg .f32 %f<4>;
+ .reg .s32 %r<2>;
+ .reg .s64 %rl<8>;
+
+ // BB#0: // %entry
+ ld.param.u64 %rl1, [kernel_param_0];
+ mov.u32 %r1, %tid.x;
+ mul.wide.s32 %rl2, %r1, 4;
+ add.s64 %rl3, %rl1, %rl2;
+ ld.param.u64 %rl4, [kernel_param_1];
+ add.s64 %rl5, %rl4, %rl2;
+ ld.param.u64 %rl6, [kernel_param_2];
+ add.s64 %rl7, %rl6, %rl2;
+ ld.global.f32 %f1, [%rl3];
+ ld.global.f32 %f2, [%rl5];
+ add.f32 %f3, %f1, %f2;
+ st.global.f32 [%rl7], %f3;
+ ret;
+ }
+
+
+Dissecting the Kernel
+---------------------
+
+Now let us dissect the LLVM IR that makes up this kernel.
+
+Data Layout
+^^^^^^^^^^^
+
+The data layout string determines the size in bits of common data types, their
+ABI alignment, and their storage size. For NVPTX, you should use one of the
+following:
+
+32-bit PTX:
+
+.. code-block:: llvm
+
+ target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+
+64-bit PTX:
+
+.. code-block:: llvm
+
+ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+
+
+Target Intrinsics
+^^^^^^^^^^^^^^^^^
+
+In this example, we use the ``@llvm.nvvm.read.ptx.sreg.tid.x`` intrinsic to
+read the X component of the current thread's ID, which corresponds to a read
+of register ``%tid.x`` in PTX. The NVPTX back-end supports a large set of
+intrinsics. A short list is shown below; please see
+``include/llvm/IR/IntrinsicsNVVM.td`` for the full list.
+
+
+================================================ ====================
+Intrinsic CUDA Equivalent
+================================================ ====================
+``i32 @llvm.nvvm.read.ptx.sreg.tid.{x,y,z}`` threadIdx.{x,y,z}
+``i32 @llvm.nvvm.read.ptx.sreg.ctaid.{x,y,z}`` blockIdx.{x,y,z}
+``i32 @llvm.nvvm.read.ptx.sreg.ntid.{x,y,z}`` blockDim.{x,y,z}
+``i32 @llvm.nvvm.read.ptx.sreg.nctaid.{x,y,z}`` gridDim.{x,y,z}
+``void @llvm.cuda.syncthreads()`` __syncthreads()
+================================================ ====================
+
+
+Address Spaces
+^^^^^^^^^^^^^^
+
+You may have noticed that all of the pointer types in the LLVM IR example had
+an explicit address space specifier. What is address space 1? NVIDIA GPU
+devices (generally) have four types of memory:
+
+- Global: Large, off-chip memory
+- Shared: Small, on-chip memory shared among all threads in a CTA
+- Local: Per-thread, private memory
+- Constant: Read-only memory shared across all threads
+
+These different types of memory are represented in LLVM IR as address spaces.
+There is also a fifth address space used by the NVPTX code generator that
+corresponds to the "generic" address space. This address space can represent
+addresses in any other address space (with a few exceptions). This allows
+users to write IR functions that can load/store memory using the same
+instructions. Intrinsics are provided to convert pointers between the generic
+and non-generic address spaces.
+
+See :ref:`address_spaces` and :ref:`nvptx_intrinsics` for more information.
+
+
+Kernel Metadata
+^^^^^^^^^^^^^^^
+
+In PTX, a function can be either a `kernel` function (callable from the host
+program), or a `device` function (callable only from GPU code). You can think
+of `kernel` functions as entry-points in the GPU program. To mark an LLVM IR
+function as a `kernel` function, we make use of special LLVM metadata. The
+NVPTX back-end will look for a named metadata node called
+``nvvm.annotations``. This named metadata must contain a list of metadata that
+describe the IR. For our purposes, we need to declare a metadata node that
+assigns the "kernel" attribute to the LLVM IR function that should be emitted
+as a PTX `kernel` function. These metadata nodes take the form:
+
+.. code-block:: text
+
+ metadata !{<function ref>, metadata !"kernel", i32 1}
+
+For the previous example, we have:
+
+.. code-block:: llvm
+
+ !nvvm.annotations = !{!0}
+ !0 = metadata !{void (float addrspace(1)*,
+ float addrspace(1)*,
+ float addrspace(1)*)* @kernel, metadata !"kernel", i32 1}
+
+Here, we have a single metadata declaration in ``nvvm.annotations``. This
+metadata annotates our ``@kernel`` function with the ``kernel`` attribute.
+
+
+Running the Kernel
+------------------
+
+Generating PTX from LLVM IR is all well and good, but how do we execute it on
+a real GPU device? The CUDA Driver API provides a convenient mechanism for
+loading and JIT compiling PTX to a native GPU device, and launching a kernel.
+The API is similar to OpenCL. A simple example showing how to load and
+execute our vector addition code is shown below. Note that for brevity this
+code does not perform much error checking!
+
+.. note::
+
+ You can also use the ``ptxas`` tool provided by the CUDA Toolkit to offline
+ compile PTX to machine code (SASS) for a specific GPU architecture. Such
+ binaries can be loaded by the CUDA Driver API in the same way as PTX. This
+ can be useful for reducing startup time by precompiling the PTX kernels.
+
+
+.. code-block:: c++
+
+ #include <iostream>
+ #include <fstream>
+ #include <cassert>
+ #include "cuda.h"
+
+
+ void checkCudaErrors(CUresult err) {
+ assert(err == CUDA_SUCCESS);
+ }
+
+ /// main - Program entry point
+ int main(int argc, char **argv) {
+ CUdevice device;
+ CUmodule cudaModule;
+ CUcontext context;
+ CUfunction function;
+ CUlinkState linker;
+ int devCount;
+
+ // CUDA initialization
+ checkCudaErrors(cuInit(0));
+ checkCudaErrors(cuDeviceGetCount(&devCount));
+ checkCudaErrors(cuDeviceGet(&device, 0));
+
+ char name[128];
+ checkCudaErrors(cuDeviceGetName(name, 128, device));
+ std::cout << "Using CUDA Device [0]: " << name << "\n";
+
+ int devMajor, devMinor;
+ checkCudaErrors(cuDeviceComputeCapability(&devMajor, &devMinor, device));
+ std::cout << "Device Compute Capability: "
+ << devMajor << "." << devMinor << "\n";
+ if (devMajor < 2) {
+ std::cerr << "ERROR: Device 0 is not SM 2.0 or greater\n";
+ return 1;
+ }
+
+ std::ifstream t("kernel.ptx");
+ if (!t.is_open()) {
+ std::cerr << "kernel.ptx not found\n";
+ return 1;
+ }
+ std::string str((std::istreambuf_iterator<char>(t)),
+ std::istreambuf_iterator<char>());
+
+ // Create driver context
+ checkCudaErrors(cuCtxCreate(&context, 0, device));
+
+ // Create module for object
+ checkCudaErrors(cuModuleLoadDataEx(&cudaModule, str.c_str(), 0, 0, 0));
+
+ // Get kernel function
+ checkCudaErrors(cuModuleGetFunction(&function, cudaModule, "kernel"));
+
+ // Device data
+ CUdeviceptr devBufferA;
+ CUdeviceptr devBufferB;
+ CUdeviceptr devBufferC;
+
+ checkCudaErrors(cuMemAlloc(&devBufferA, sizeof(float)*16));
+ checkCudaErrors(cuMemAlloc(&devBufferB, sizeof(float)*16));
+ checkCudaErrors(cuMemAlloc(&devBufferC, sizeof(float)*16));
+
+ float* hostA = new float[16];
+ float* hostB = new float[16];
+ float* hostC = new float[16];
+
+ // Populate input
+ for (unsigned i = 0; i != 16; ++i) {
+ hostA[i] = (float)i;
+ hostB[i] = (float)(2*i);
+ hostC[i] = 0.0f;
+ }
+
+ checkCudaErrors(cuMemcpyHtoD(devBufferA, &hostA[0], sizeof(float)*16));
+ checkCudaErrors(cuMemcpyHtoD(devBufferB, &hostB[0], sizeof(float)*16));
+
+
+ unsigned blockSizeX = 16;
+ unsigned blockSizeY = 1;
+ unsigned blockSizeZ = 1;
+ unsigned gridSizeX = 1;
+ unsigned gridSizeY = 1;
+ unsigned gridSizeZ = 1;
+
+ // Kernel parameters
+ void *KernelParams[] = { &devBufferA, &devBufferB, &devBufferC };
+
+ std::cout << "Launching kernel\n";
+
+ // Kernel launch
+ checkCudaErrors(cuLaunchKernel(function, gridSizeX, gridSizeY, gridSizeZ,
+ blockSizeX, blockSizeY, blockSizeZ,
+ 0, NULL, KernelParams, NULL));
+
+ // Retrieve device data
+ checkCudaErrors(cuMemcpyDtoH(&hostC[0], devBufferC, sizeof(float)*16));
+
+
+ std::cout << "Results:\n";
+ for (unsigned i = 0; i != 16; ++i) {
+ std::cout << hostA[i] << " + " << hostB[i] << " = " << hostC[i] << "\n";
+ }
+
+
+ // Clean up after ourselves
+ delete [] hostA;
+ delete [] hostB;
+ delete [] hostC;
+
+ // Clean-up
+ checkCudaErrors(cuMemFree(devBufferA));
+ checkCudaErrors(cuMemFree(devBufferB));
+ checkCudaErrors(cuMemFree(devBufferC));
+ checkCudaErrors(cuModuleUnload(cudaModule));
+ checkCudaErrors(cuCtxDestroy(context));
+
+ return 0;
+ }
+
+
+You will need to link with the CUDA driver and specify the path to cuda.h.
+
+.. code-block:: text
+
+ # clang++ sample.cpp -o sample -O2 -g -I/usr/local/cuda-5.5/include -lcuda
+
+We don't need to specify a path to ``libcuda.so`` since this is installed in a
+system location by the driver, not the CUDA toolkit.
+
+If everything goes as planned, you should see the following output when
+running the compiled program:
+
+.. code-block:: text
+
+ Using CUDA Device [0]: GeForce GTX 680
+ Device Compute Capability: 3.0
+ Launching kernel
+ Results:
+ 0 + 0 = 0
+ 1 + 2 = 3
+ 2 + 4 = 6
+ 3 + 6 = 9
+ 4 + 8 = 12
+ 5 + 10 = 15
+ 6 + 12 = 18
+ 7 + 14 = 21
+ 8 + 16 = 24
+ 9 + 18 = 27
+ 10 + 20 = 30
+ 11 + 22 = 33
+ 12 + 24 = 36
+ 13 + 26 = 39
+ 14 + 28 = 42
+ 15 + 30 = 45
+
+.. note::
+
+ You will likely see a different device identifier based on your hardware
+
+
+Tutorial: Linking with Libdevice
+================================
+
+In this tutorial, we show a simple example of linking LLVM IR with the
+libdevice library. We will use the same kernel as the previous tutorial,
+except that we will compute ``C = pow(A, B)`` instead of ``C = A + B``.
+Libdevice provides an ``__nv_powf`` function that we will use.
+
+.. code-block:: llvm
+
+ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+ target triple = "nvptx64-nvidia-cuda"
+
+ ; Intrinsic to read X component of thread ID
+ declare i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind
+ ; libdevice function
+ declare float @__nv_powf(float, float)
+
+ define void @kernel(float addrspace(1)* %A,
+ float addrspace(1)* %B,
+ float addrspace(1)* %C) {
+ entry:
+ ; What is my ID?
+ %id = tail call i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind
+
+ ; Compute pointers into A, B, and C
+ %ptrA = getelementptr float addrspace(1)* %A, i32 %id
+ %ptrB = getelementptr float addrspace(1)* %B, i32 %id
+ %ptrC = getelementptr float addrspace(1)* %C, i32 %id
+
+ ; Read A, B
+ %valA = load float addrspace(1)* %ptrA, align 4
+ %valB = load float addrspace(1)* %ptrB, align 4
+
+ ; Compute C = pow(A, B)
+ %valC = call float @__nv_powf(float %valA, float %valB)
+
+ ; Store back to C
+ store float %valC, float addrspace(1)* %ptrC, align 4
+
+ ret void
+ }
+
+ !nvvm.annotations = !{!0}
+ !0 = metadata !{void (float addrspace(1)*,
+ float addrspace(1)*,
+ float addrspace(1)*)* @kernel, metadata !"kernel", i32 1}
+
+
+To compile this kernel, we perform the following steps:
+
+1. Link with libdevice
+2. Internalize all but the public kernel function
+3. Run ``NVVMReflect`` and set ``__CUDA_FTZ`` to 0
+4. Optimize the linked module
+5. Codegen the module
+
+
+These steps can be performed by the LLVM ``llvm-link``, ``opt``, and ``llc``
+tools. In a complete compiler, these steps can also be performed entirely
+programmatically by setting up an appropriate pass configuration (see
+:ref:`libdevice`).
+
+.. code-block:: text
+
+ # llvm-link t2.bc libdevice.compute_20.10.bc -o t2.linked.bc
+ # opt -internalize -internalize-public-api-list=kernel -nvvm-reflect-list=__CUDA_FTZ=0 -nvvm-reflect -O3 t2.linked.bc -o t2.opt.bc
+ # llc -mcpu=sm_20 t2.opt.bc -o t2.ptx
+
+.. note::
+
+ The ``-nvvm-reflect-list=_CUDA_FTZ=0`` is not strictly required, as any
+ undefined variables will default to zero. It is shown here for evaluation
+ purposes.
+
+
+This gives us the following PTX (excerpt):
+
+.. code-block:: text
+
+ //
+ // Generated by LLVM NVPTX Back-End
+ //
+
+ .version 3.1
+ .target sm_20
+ .address_size 64
+
+ // .globl kernel
+ // @kernel
+ .visible .entry kernel(
+ .param .u64 kernel_param_0,
+ .param .u64 kernel_param_1,
+ .param .u64 kernel_param_2
+ )
+ {
+ .reg .pred %p<30>;
+ .reg .f32 %f<111>;
+ .reg .s32 %r<21>;
+ .reg .s64 %rl<8>;
+
+ // BB#0: // %entry
+ ld.param.u64 %rl2, [kernel_param_0];
+ mov.u32 %r3, %tid.x;
+ ld.param.u64 %rl3, [kernel_param_1];
+ mul.wide.s32 %rl4, %r3, 4;
+ add.s64 %rl5, %rl2, %rl4;
+ ld.param.u64 %rl6, [kernel_param_2];
+ add.s64 %rl7, %rl3, %rl4;
+ add.s64 %rl1, %rl6, %rl4;
+ ld.global.f32 %f1, [%rl5];
+ ld.global.f32 %f2, [%rl7];
+ setp.eq.f32 %p1, %f1, 0f3F800000;
+ setp.eq.f32 %p2, %f2, 0f00000000;
+ or.pred %p3, %p1, %p2;
+ @%p3 bra BB0_1;
+ bra.uni BB0_2;
+ BB0_1:
+ mov.f32 %f110, 0f3F800000;
+ st.global.f32 [%rl1], %f110;
+ ret;
+ BB0_2: // %__nv_isnanf.exit.i
+ abs.f32 %f4, %f1;
+ setp.gtu.f32 %p4, %f4, 0f7F800000;
+ @%p4 bra BB0_4;
+ // BB#3: // %__nv_isnanf.exit5.i
+ abs.f32 %f5, %f2;
+ setp.le.f32 %p5, %f5, 0f7F800000;
+ @%p5 bra BB0_5;
+ BB0_4: // %.critedge1.i
+ add.f32 %f110, %f1, %f2;
+ st.global.f32 [%rl1], %f110;
+ ret;
+ BB0_5: // %__nv_isinff.exit.i
+
+ ...
+
+ BB0_26: // %__nv_truncf.exit.i.i.i.i.i
+ mul.f32 %f90, %f107, 0f3FB8AA3B;
+ cvt.rzi.f32.f32 %f91, %f90;
+ mov.f32 %f92, 0fBF317200;
+ fma.rn.f32 %f93, %f91, %f92, %f107;
+ mov.f32 %f94, 0fB5BFBE8E;
+ fma.rn.f32 %f95, %f91, %f94, %f93;
+ mul.f32 %f89, %f95, 0f3FB8AA3B;
+ // inline asm
+ ex2.approx.ftz.f32 %f88,%f89;
+ // inline asm
+ add.f32 %f96, %f91, 0f00000000;
+ ex2.approx.f32 %f97, %f96;
+ mul.f32 %f98, %f88, %f97;
+ setp.lt.f32 %p15, %f107, 0fC2D20000;
+ selp.f32 %f99, 0f00000000, %f98, %p15;
+ setp.gt.f32 %p16, %f107, 0f42D20000;
+ selp.f32 %f110, 0f7F800000, %f99, %p16;
+ setp.eq.f32 %p17, %f110, 0f7F800000;
+ @%p17 bra BB0_28;
+ // BB#27:
+ fma.rn.f32 %f110, %f110, %f108, %f110;
+ BB0_28: // %__internal_accurate_powf.exit.i
+ setp.lt.f32 %p18, %f1, 0f00000000;
+ setp.eq.f32 %p19, %f3, 0f3F800000;
+ and.pred %p20, %p18, %p19;
+ @!%p20 bra BB0_30;
+ bra.uni BB0_29;
+ BB0_29:
+ mov.b32 %r9, %f110;
+ xor.b32 %r10, %r9, -2147483648;
+ mov.b32 %f110, %r10;
+ BB0_30: // %__nv_powf.exit
+ st.global.f32 [%rl1], %f110;
+ ret;
+ }
+
Added: www-releases/trunk/3.6.2/docs/_sources/Packaging.txt
URL: http://llvm.org/viewvc/llvm-project/www-releases/trunk/3.6.2/docs/_sources/Packaging.txt?rev=242418&view=auto
==============================================================================
--- www-releases/trunk/3.6.2/docs/_sources/Packaging.txt (added)
+++ www-releases/trunk/3.6.2/docs/_sources/Packaging.txt Thu Jul 16 11:56:00 2015
@@ -0,0 +1,73 @@
+========================
+Advice on Packaging LLVM
+========================
+
+.. contents::
+ :local:
+
+Overview
+========
+
+LLVM sets certain default configure options to make sure our developers don't
+break things for constrained platforms. These settings are not optimal for most
+desktop systems, and we hope that packagers (e.g., Redhat, Debian, MacPorts,
+etc.) will tweak them. This document lists settings we suggest you tweak.
+
+LLVM's API changes with each release, so users are likely to want, for example,
+both LLVM-2.6 and LLVM-2.7 installed at the same time to support apps developed
+against each.
+
+Compile Flags
+=============
+
+LLVM runs much more quickly when it's optimized and assertions are removed.
+However, such a build is currently incompatible with users who build without
+defining ``NDEBUG``, and the lack of assertions makes it hard to debug problems
+in user code. We recommend allowing users to install both optimized and debug
+versions of LLVM in parallel. The following configure flags are relevant:
+
+``--disable-assertions``
+ Builds LLVM with ``NDEBUG`` defined. Changes the LLVM ABI. Also available
+ by setting ``DISABLE_ASSERTIONS=0|1`` in ``make``'s environment. This
+ defaults to enabled regardless of the optimization setting, but it slows
+ things down.
+
+``--enable-debug-symbols``
+ Builds LLVM with ``-g``. Also available by setting ``DEBUG_SYMBOLS=0|1`` in
+ ``make``'s environment. This defaults to disabled when optimizing, so you
+ should turn it back on to let users debug their programs.
+
+``--enable-optimized``
+ (For svn checkouts) Builds LLVM with ``-O2`` and, by default, turns off
+ debug symbols. Also available by setting ``ENABLE_OPTIMIZED=0|1`` in
+ ``make``'s environment. This defaults to enabled when not in a
+ checkout.
+
+C++ Features
+============
+
+RTTI
+ LLVM disables RTTI by default. Add ``REQUIRES_RTTI=1`` to your environment
+ while running ``make`` to re-enable it. This will allow users to build with
+ RTTI enabled and still inherit from LLVM classes.
+
+Shared Library
+==============
+
+Configure with ``--enable-shared`` to build
+``libLLVM-<major>.<minor>.(so|dylib)`` and link the tools against it. This
+saves lots of binary size at the cost of some startup time.
+
+Dependencies
+============
+
+``--enable-libffi``
+ Depend on `libffi <http://sources.redhat.com/libffi/>`_ to allow the LLVM
+ interpreter to call external functions.
+
+``--with-oprofile``
+
+ Depend on `libopagent
+ <http://oprofile.sourceforge.net/doc/devel/index.html>`_ (>=version 0.9.4)
+ to let the LLVM JIT tell oprofile about function addresses and line
+ numbers.
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