[LLVMdev] [DRAFT] Announcement for LLVM 1.6 [DRAFT]

Chris Lattner sabre at nondot.org
Tue Oct 25 21:23:42 PDT 2005

Hi All,

I'm putting together the announcement for the LLVM 1.6 release.  Here is 
what I have so far.  Because so much has been done, it is very likely that 
I have forgotten something.  If you have done something that is not on the 
list, please send me a private email so I can add it (also, please tell 
me if I've made a mistake or miscredited something)!

My next project is to start hacking on the release notes.  I would 
appreciate it if people could look into the documentation and let us know 
about (or fix!) anything that is out of date, misleading, or could be 

I believe we are still on track to start rolling the release next monday 
(Oct 31), which makes the likely 'official' release to be about a week 
from then.  Once the release is officially out, it would be great to get 
help making binary distros for additional platforms (e.g. Cygwin) and for 
packages to be built (e.g. for the various Linux distros).

Thanks all!


----------------- 8< ----------------- 8< --------------------

Insert high-level description/overview blurb here :)
Themes: Major code generator work.  New excellent performance/stability on 
PPC/darwin.  Going back to 3-month release cycle.  LLVM being used by many 
different people projects, e.g. papers being published.

Major New Features:

X. Reid added guards to the JIT, enabling it to JIT multithreaded code
    (on systems with pthreads).  Threads support can be disabled by
    configuring LLVM with the --disable-threads swith.
X. LLVM includes a new optimization to statically evaluate C++ static
    variable constructors when they are simple enough.  For example, it can
    now statically initialize "struct X { int a; X() : a(4) {} } g;".
X. The Loop Strength Reduction pass is completely rewritten, far more
    aggressive and enabled by default on most RISC targets.  On PPC, we
    find that it often speeds up programs from 10-40% depending on the
X. LLVM now includes support for auto-generating large portions of the
    instruction selectors from target descriptions.  This allows us to
    write patterns in the target .td file, instead of writing lots of
    nasty C++ code.  Most of the PowerPC instruction selector is now
    generated from the PowerPC target description files and other targets
    are adding support that will be live for LLVM 1.7.
X. Andrew has dramatically improved the LLVM Alpha backend, to the point
    where it is now considered fully functional and off the 'beta' list.

Major Code Generator Changes:

X. Nate wrote a new component for the backend, a DAG Combiner.  This
    allows the backend to take advantage of identities and do low-level
    peephole-style optimizations on the DAG.
X. Nate added support for a new TargetSubtarget interface, which
    determines which parts of the target to enable based on the
    target-triple (e.g., whether to use GAS or Intel asm printers on X86).
X. Jim Laskey extended sub-target support to include -mcpu and -mattr,
    allowing the target to think about what to do when particular features
    are enabled, but allowing the end-user to think about what CPU they
X. Jim also contributed a new light-weight instruction scheduler,
    available to targets that use DAG-to-DAG instruction selectors.  In
    this release, the scheduler is fully operational but needs tuning, so
    it is not enabled by default.
X. The instruction selector framework now supports DAG-to-DAG instruction
    selection, where the instruction selector does pattern matching, but
    no code emission (necessary for scheduling & .td file autogeneration).

Other Code Generator Changes:

X. Duraid contributed many improvements to the Itanium backend
X. Andrew Lenharth contributed a major change to the varargs support,
    allowing LLVM to work with targets whose va_list type is a struct.
X. The instruction framework that debuted in LLVM 1.5 is far more mature
    and robust, and is able to handle many more strange target features.
X. Andrew added initial JIT support to the Alpha backend, which can run
    some simple programs.  It is not fully complete yet though.
X. Jim Laskey contributed patches to improve the instruction selection in
    the PowerPC backend, matching more RLWIMI cases for example.
X. Nate implemented most of the PowerPC DAG-to-DAG instruction selector.
X. The tblgen tool & code generator now have more assertions and checking,
    which catch errors early, making it easier to work on the backend.
X. The default register allocator is now far faster on some testcases,
    particularly on targets with a large number of registers (e.g. IA64
    and PPC).
X. Jim extended tblgen to allow description of subtarget features in the
    .td files for the target.
X. There have been several minor improvements to the register allocator to
    coallesce more aggressively and coallesce spill code with copies more

Miscellaneous Improvements:

X. Andrew added support to the JIT to built a Global Offset Table if
    needed by a target.
X. Alexander Friedman improved the .ll file parser to be able to read
    from a text buffer in addition to a file.
X. Bryan Turner tried LLVM with Quest, a random testcase generator, and
    exposed several bugs (which are now fixed).
X. The llvm-test suite can now use the NAG Fortran to C compiler to compile
    SPEC FP programs if available (allowing us to test all of SPEC'95 & 2K).
X. The JIT-debugger mode of bugpoint is now much faster than before.
X. When bugpoint is grinding away and the user hits ctrl-C, it now
    gracefully stops and gives what it has reduced so far, instead of
    giving up completely.
X. LLVM now includes Xcode project files.
X. Jim Laskey added bitvector support to the command line option parsing
    library.  See http://llvm.org/docs/CommandLine.html#bits
X. We no longer build two versions of most LLVM libraries, which reduces
    the time required to build LLVM.
X. Documentation for the code generator is improving, though it is
    still incomplete: http://llvm.org/docs/CodeGenerator.html
X. The code produced when exception handling is enabled is far more
    efficient in some cases, particularly on Mac OS/X.

Portability Improvements:

X. Nate added support for Mac OS/X on Intel.
X. X86 tail calls now work with the JIT and Jeff Cohen added code
    to support them under Visual C++.
X. Nate contributed a patch to allow LLVM to build with GCC 4.x, and Reid
    contributed several cleanup patches to silence GCC 4 warnings.
X. The llvm-test suite is now fully compatible with Mac OS/X
    (non-portabilities in the programs have been fixed).
X. Jeff Cohen contributed portability fixes to build on AMD64.

In addition to the new features and infrastructure we have built, we have 
also fixed many minor bugs in the C/C++ front-end, optimizers, and code 
generator including 54 bugzilla bugs (search for target milestone = 1.6). 
LLVM 1.6 is by far the best release we've had yet!

As usual, if you have any questions or comments about LLVM or any of the 
features in this status update, please feel free to contact the LLVMdev 
mailing list (llvmdev at cs.uiuc.edu)!

Finally, here is the previous status report, the LLVM 1.5 announcement:



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