[llvm-commits] [llvm] r42186 - /llvm/trunk/docs/ReleaseNotes.html
Chris Lattner
sabre at nondot.org
Thu Sep 20 20:54:09 PDT 2007
Author: lattner
Date: Thu Sep 20 22:54:09 2007
New Revision: 42186
URL: http://llvm.org/viewvc/llvm-project?rev=42186&view=rev
Log:
Initial hack at 2.1 release notes.
Modified:
llvm/trunk/docs/ReleaseNotes.html
Modified: llvm/trunk/docs/ReleaseNotes.html
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ReleaseNotes.html?rev=42186&r1=42185&r2=42186&view=diff
==============================================================================
--- llvm/trunk/docs/ReleaseNotes.html (original)
+++ llvm/trunk/docs/ReleaseNotes.html Thu Sep 20 22:54:09 2007
@@ -4,11 +4,11 @@
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 2.0 Release Notes</title>
+ <title>LLVM 2.1 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.0 Release Notes</div>
+<div class="doc_title">LLVM 2.1 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
@@ -32,7 +32,7 @@
<div class="doc_text">
<p>This document contains the release notes for the LLVM compiler
-infrastructure, release 2.0. Here we describe the status of LLVM, including
+infrastructure, release 2.1. Here we describe the status of LLVM, including
major improvements from the previous release and any known problems. All LLVM
releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
releases web site</a>.</p>
@@ -44,10 +44,9 @@
list</a> is a good place to send them.</p>
<p>Note that if you are reading this file from a Subversion checkout or the
-main LLVM web page,
-this document applies to the <i>next</i> release, not the current one. To see
-the release notes for the current or previous releases, see the <a
-href="http://llvm.org/releases/">releases page</a>.</p>
+main LLVM web page, this document applies to the <i>next</i> release, not the
+current one. To see the release notes for a specific releases, please see the
+<a href="http://llvm.org/releases/">releases page</a>.</p>
</div>
@@ -59,416 +58,197 @@
<div class="doc_text">
-<p>This is the eleventh public release of the LLVM Compiler Infrastructure.
-Being the first major release since 1.0, this release is different in several
-ways from our previous releases:</p>
-
-<ol>
-<li>We took this as an opportunity to
-break backwards compatibility with the LLVM 1.x bytecode and .ll file format.
-If you have LLVM 1.9 .ll files that you would like to upgrade to LLVM 2.x, we
-recommend the use of the stand alone <a href="#llvm-upgrade">llvm-upgrade</a>
-tool (which is included with 2.0). We intend to keep compatibility with .ll
-and .bc formats within the 2.x release series, like we did within the 1.x
-series.</li>
-<li>There are several significant change to the LLVM IR and internal APIs, such
- as a major overhaul of the type system, the completely new bitcode file
- format, etc (described below).</li>
-<li>We designed the release around a 6 month release cycle instead of the usual
- 3-month cycle. This gave us extra time to develop and test some of the
- more invasive features in this release.</li>
-<li>LLVM 2.0 no longer supports the llvm-gcc3 front-end. Users are required to
- upgrade to llvm-gcc4. llvm-gcc4 includes many features over
- llvm-gcc3, is faster, and is <a href="CFEBuildInstrs.html">much easier to
- build from source</a>.</li>
-</ol>
-
-<p>Note that while this is a major version bump, this release has been
- extensively tested on a wide range of software. It is easy to say that this
- is our best release yet, in terms of both features and correctness. This is
- the first LLVM release to correctly compile and optimize major software like
- LLVM itself, Mozilla/Seamonkey, Qt 4.3rc1, kOffice, etc out of the box on
- linux/x86.
- </p>
+<p>This is the twelfth public release of the LLVM Compiler Infrastructure.
+It includes many features and refinements from LLVM 2.0.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="newfeatures">New Features in LLVM 2.0</a>
+<a name="frontends">New Frontends</a>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="majorchanges">Major Changes</a></div>
<div class="doc_text">
-<p>Changes to the LLVM IR itself:</p>
-
-<ul>
-
-<li>Integer types are now completely signless. This means that we
- have types like i8/i16/i32 instead of ubyte/sbyte/short/ushort/int
- etc. LLVM operations that depend on sign have been split up into
- separate instructions (<a href="http://llvm.org/PR950">PR950</a>). This
- eliminates cast instructions that just change the sign of the operands (e.g.
- int -> uint), which reduces the size of the IR and makes optimizers
- simpler to write.</li>
+<p>LLVM 2.1 brings two new beta C front-ends. First, Duncan, Anton and Devang
+start syncing up llvm-gcc with GCC 4.2, yielding "llvm-gcc 4.2" (creative,
+huh?). llvm-gcc 4.2 has the promise to bring much better FORTRAN and Ada
+support to LLVM as well as features like atomic builtins, OpenMP, and many other
+things. Check it out!</p>
-<li>Integer types with arbitrary bitwidths (e.g. i13, i36, i42, i1057, etc) are
- now supported in the LLVM IR and optimizations (<a
- href="http://llvm.org/PR1043">PR1043</a>). However, neither llvm-gcc
- (<a href="http://llvm.org/PR1284">PR1284</a>) nor the native code generators
- (<a href="http://llvm.org/PR1270">PR1270</a>) support non-standard width
- integers yet.</li>
+<p>Second, LLVM now includes its own native C and Objective-C front-end (C++ is
+in progress, but is not very far along) code named "<a
+href="http://clang.llvm.org/">clang</a>". This front-end has a number of great
+features, primarily aimed at source-level analysis and speeding up compile-time.
+At this point though, the LLVM Code Generator component is still very early in
+development, so it's mostly useful for people looking to build source-level
+analysis tools or source-to-source translators.</p>
-<li>'Type planes' have been removed (<a href="http://llvm.org/PR411">PR411</a>).
- It is no longer possible to have two values with the same name in the
- same symbol table. This simplifies LLVM internals, allowing significant
- speedups.</li>
-
-<li>Global variables and functions in .ll files are now prefixed with
- @ instead of % (<a href="http://llvm.org/PR645">PR645</a>).</li>
+</div>
-<li>The LLVM 1.x "bytecode" format has been replaced with a
- completely new binary representation, named 'bitcode'. The <a
- href="BitCodeFormat.html">Bitcode Format</a> brings a
- number of advantages to the LLVM over the old bytecode format: it is denser
- (files are smaller), more extensible, requires less memory to read,
- is easier to keep backwards compatible (so LLVM 2.5 will read 2.0 .bc
- files), and has many other nice features.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="optimizer">Optimizer Improvements</a>
+</div>
-<li>Load and store instructions now track the alignment of their pointer
- (<a href="http://www.llvm.org/PR400">PR400</a>). This allows the IR to
- express loads that are not sufficiently aligned (e.g. due to '<tt>#pragma
- packed</tt>') or to capture extra alignment information.</li>
-</ul>
+<div class="doc_text">
-<p>Major new features:</p>
+<p>Some of the most noticable improvements this release have been in the
+optimizer, speeding it up and making it more aggressive</p>
<ul>
-<li>A number of ELF features are now supported by LLVM, including 'visibility',
- extern weak linkage, Thread Local Storage (TLS) with the <tt>__thread</tt>
- keyword, and symbol aliases.
- Among other things, this means that many of the special options needed to
- configure llvm-gcc on linux are no longer needed, and special hacks to build
- large C++ libraries like Qt are not needed.</li>
-
-<li>LLVM now has a new MSIL backend. <tt>llc -march=msil</tt> will now turn LLVM
- into MSIL (".net") bytecode. This is still fairly early development
- with a number of limitations.</li>
+<li>Owen DSE and MemDep analysis</li>
+<li>Owen GVN</li>
+<li>Owen GVN-PRE, not in llvm-gcc</li>
+<li>Devang merged ETForest and DomTree into a single easier to use data
+structure.</li>
+<li>Nick Lewycky improved loop trip count analysis to handle many more common
+cases.</li>
-<li>A new <a href="CommandGuide/html/llvm-upgrade.html">llvm-upgrade</a> tool
- exists to migrates LLVM 1.9 .ll files to LLVM 2.0 syntax.</li>
</ul>
</div>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="codegen">Code Generator Improvements</a>
+</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="llvmgccfeatures">llvm-gcc
-Improvements</a></div>
<div class="doc_text">
-<p>New features include:
-</p>
+
+<p>foo</p>
<ul>
-<li>Precompiled Headers (PCH) are now supported.</li>
-<li>"<tt>#pragma packed</tt>" is now supported, as are the various features
- described above (visibility, extern weak linkage, __thread, aliases,
- etc).</li>
+<li>Dale finished up the Tail Merging optimization in the code generator,
+enabling it by default. This produces smaller code that is also faster in some
+cases.</li>
+
+<li>Dan Gohman changed the way we represent vectors before legalization,
+significantly simplifying the SelectionDAG representation for these and making
+the code generator faster for vector code.</li>
-<li>Tracking function parameter/result attributes is now possible.</li>
+<li>Evan remat rewrite (coallesced intervals + folding of remat'd loads) and
+live intervals improvements.</li>
-<li>Many internal enhancements have been added, such as improvements to
- NON_LVALUE_EXPR, arrays with non-zero base, structs with variable sized
- fields, VIEW_CONVERT_EXPR, CEIL_DIV_EXPR, nested functions, and many other
- things. This is primarily to supports non-C GCC front-ends, like Ada.</li>
+<li>Dan Gohman contributed support for better alignment and volatility handling
+in the code generator, and significantly enhanced alignment analysis for SSE
+load/store instructions.</li>
-<li>It is simpler to configure llvm-gcc for linux.</li>
+<li>Christopher Lamb virtual register sub-register support, better truncates and
+extends on X86.</li>
+
+<li>Duraid Madina contributed a new "bigblock" register allocator, and Roman
+Levenstein contributed several big improvements. BigBlock is optimized for code
+that uses very large basic blocks. It is slightly slower than the "local"
+allocator, but produces much better code.</li>
+
+<li>David Greene refactored the register allocator to split coallescing out from
+allocation, making coallescers pluggable.</li>
</ul>
-
+
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="optimizer">Optimizer
-Improvements</a></div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="targetspecific">Target Specific Improvements</a>
+</div>
<div class="doc_text">
<p>New features include:
</p>
<ul>
-<li>The <a href="WritingAnLLVMPass.html">pass manager</a> has been entirely
- rewritten, making it significantly smaller, simpler, and more extensible.
- Support has been added to run <tt>FunctionPass</tt>es interlaced with
- <tt>CallGraphSCCPass</tt>es, we now support loop transformations
- explicitly with <tt>LoopPass</tt>, and <tt>ModulePass</tt>es may now use the
- result of <tt>FunctionPass</tt>es.</li>
-
-<li>LLVM 2.0 includes a new loop rotation pass, which converts "for loops" into
- "do/while loops", where the condition is at the bottom of the loop.</li>
-
-<li>The Loop Strength Reduction pass has been improved, and we now support
- sinking expressions across blocks to reduce register pressure.</li>
-
-<li>The <tt>-scalarrepl</tt> pass can now promote unions containing FP values
- into a register, it can also handle unions of vectors of the same
- size.</li>
-
-<li>The [Post]DominatorSet classes have been removed from LLVM and clients
- switched to use the more-efficient ETForest class instead.</li>
-
-<li>The ImmediateDominator class has also been removed, and clients have been
- switched to use DominatorTree instead.</li>
-
-<li>The predicate simplifier pass has been improved, making it able to do
- simple value range propagation and eliminate more conditionals. However,
- note that predsimplify is not enabled by default in llvm-gcc.</li>
-
+<li>Bruno Cardoso Lopes contributed initial MIPS support.</li>
+<li>Bill Wendling added SSSE3 support.</li>
+<li>New Target independent if converter, ARM uses it so far</li>
+<li>Nicholas Geoffray contributed improved linux/ppc ABI and JIT support.</li>
+<li>Dale Johannesen rewrote handling of 32-bit float values in the X86 backend
+when using the floating point stack, fixing several nasty bugs.</li>
+<li>Dan contributed rematerialization support for the X86 backend.</li>
</ul>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="codegen">Code
-Generator Enhancements</a></div>
-
-<div class="doc_text">
-<p>
-New features include:
-</p>
-
-<ul>
-
-<li>LLVM now supports software floating point, which allows LLVM to target
- chips that don't have hardware FPUs (e.g. ARM thumb mode).</li>
-<li>A new register scavenger has been implemented, which is useful for
- finding free registers after register allocation. This is useful when
- rewriting frame references on RISC targets, for example.</li>
-
-<li>Heuristics have been added to avoid coalescing vregs with very large live
- ranges to physregs. This was bad because it effectively pinned the physical
- register for the entire lifetime of the virtual register (<a
- href="http://llvm.org/PR711">PR711</a>).</li>
-
-<li>Support now exists for very simple (but still very useful)
- rematerialization the register allocator, enough to move
- instructions like "load immediate" and constant pool loads.</li>
-
-<li>Switch statement lowering is significantly better, improving codegen for
- sparse switches that have dense subregions, and implemented support
- for the shift/and trick.</li>
-
-<li>LLVM now supports tracking physreg sub-registers and super-registers
- in the code generator, and includes extensive register
- allocator changes to track them.</li>
-
-<li>There is initial support for virtreg sub-registers
- (<a href="http://llvm.org/PR1350">PR1350</a>).</li>
-
-</ul>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="llvmgccimprovements">llvm-gcc Improvements</a>
+</div>
-<p>
-Other improvements include:
+<div class="doc_text">
+<p>New features include:
</p>
<ul>
+<li>Duncan and Anton exception handling in llvm-gcc 4.0/4.2</li>
-<li>Inline assembly support is much more solid that before.
- The two primary features still missing are support for 80-bit floating point
- stack registers on X86 (<a href="http://llvm.org/PR879">PR879</a>), and
- support for inline asm in the C backend (<a
- href="http://llvm.org/PR802">PR802</a>).</li>
+<li>Devang and Duncan: Bitfields, pragma pack</li>
-<li>DWARF debug information generation has been improved. LLVM now passes
- most of the GDB testsuite on MacOS and debug info is more dense.</li>
+<li>Tanya implemented support for __attribute__((noinline)) in llvm-gcc, and
+added support for generic variable annotations which are propagated into the
+LLVM IR, e.g. "<tt>int X __attribute__((annotate("myproperty")));</tt>".</li>
-<li>Codegen support for Zero-cost DWARF exception handling has been added (<a
- href="http://llvm.org/PR592">PR592</a>). It is mostly
- complete and just in need of continued bug fixes and optimizations at
- this point. However, support in llvm-g++ is disabled with an
- #ifdef for the 2.0 release (<a
- href="http://llvm.org/PR870">PR870</a>).</li>
+<li>Sheng Zhou and Christopher Lamb implemented alias analysis support for
+'restrict' arguments to functions.</li>
-<li>The code generator now has more accurate and general hooks for
- describing addressing modes ("isLegalAddressingMode") to
- optimizations like loop strength reduction and code sinking.</li>
-
-<li>Progress has been made on a direct Mach-o .o file writer. Many small
- apps work, but it is still not quite complete.</li>
+<li>Duncan contributed support for trampolines (pointers to nested functions),
+currently only supported on x86 target.</li>
</ul>
+
+</div>
-<p>In addition, the LLVM target description format has itself been extended in
- several ways:</p>
-
-<ul>
-<li>TargetData now supports better target parameterization in
- the .ll/.bc files, eliminating the 'pointersize/endianness' attributes
- in the files (<a href="http://llvm.org/PR761">PR761</a>).</li>
-
-<li>TargetData was generalized for finer grained alignment handling,
- handling of vector alignment, and handling of preferred alignment</li>
-
-<li>LLVM now supports describing target calling conventions
- explicitly in .td files, reducing the amount of C++ code that needs
- to be written for a port.</li>
-
-</ul>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="coreimprovements">LLVM Core Improvements</a>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="specifictargets">Target-Specific
-Improvements</a></div>
-
<div class="doc_text">
-
-<p>X86-specific Code Generator Enhancements:
+<p>New features include:
</p>
<ul>
-<li>The MMX instruction set is now supported through intrinsics.</li>
-<li>The scheduler was improved to better reduce register pressure on
- X86 and other targets that are register pressure sensitive.</li>
-<li>Linux/x86-64 support is much better.</li>
-<li>PIC support for linux/x86 has been added.</li>
-<li>The X86 backend now supports the GCC regparm attribute.</li>
-<li>LLVM now supports inline asm with multiple constraint letters per operand
- (like "mri") which is common in X86 inline asms.</li>
-</ul>
-
-<p>ARM-specific Code Generator Enhancements:</p>
-
-<ul>
-<li>The ARM code generator is now stable and fully supported.</li>
-
-<li>There are major new features, including support for ARM
- v4-v6 chips, vfp support, soft float point support, pre/postinc support,
- load/store multiple generation, constant pool entry motion (to support
- large functions), inline asm support, weak linkage support, static
- ctor/dtor support and many bug fixes.</li>
-
-<li>Added support for Thumb code generation (<tt>llc -march=thumb</tt>).</li>
-
-<li>The ARM backend now supports the ARM AAPCS/EABI ABI and PIC codegen on
- arm/linux.</li>
-
-<li>Several bugs were fixed for DWARF debug info generation on arm/linux.</li>
-
-</ul>
-
-<p>PowerPC-specific Code Generator Enhancements:</p>
-
-<ul>
-<li>The PowerPC 64 JIT now supports addressing code loaded above the 2G
- boundary.</li>
+<li>Neil Booth APFloat, foundation for long double support that will be wrapped
+up in 2.2. Dale contributed most of long double support, will be enabled in
+2.2.</li>
-<li>Improved support for the Linux/ppc ABI and the linux/ppc JIT is fully
- functional now. llvm-gcc and static compilation are not fully supported
- yet though.</li>
+<li>LLVM now provides an LLVMBuilder class which makes it significantly easier
+to create LLVM IR instructions.</li>
-<li>Many PowerPC 64 bug fixes.</li>
+<li>Reid contributed support for intrinsics that take arbitrary integer typed
+arguments, Dan Gohman and Chandler extended it to support FP and vectors.</li>
+</li>
</ul>
-
+
</div>
-
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="other">Other Improvements</a></div>
-<div class="doc_text">
-
-<p>More specific changes include:</p>
-
-<ul>
-<li>LLVM no longer relies on static destructors to shut itself down. Instead,
- it lazily initializes itself and shuts down when <tt>llvm_shutdown()</tt> is
- explicitly called.</li>
-
-<li>LLVM now has significantly fewer static constructors, reducing startup time.
- </li>
-
-<li>Several classes have been refactored to reduce the amount of code that
- gets linked into apps that use the JIT.</li>
-
-<li>Construction of intrinsic function declarations has been simplified.</li>
-
-<li>The gccas/gccld tools have been replaced with small shell scripts.</li>
-
-<li>Support has been added to llvm-test for running on low-memory
- or slow machines (make SMALL_PROBLEM_SIZE=1).</li>
-
-</ul>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="otherimprovements">Other Improvements</a>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="apichanges">API Changes</a></div>
<div class="doc_text">
-
-<p>LLVM 2.0 contains a revamp of the type system and several other significant
-internal changes. If you are programming to the C++ API, be aware of the
-following major changes:</p>
+<p>New features include:
+</p>
<ul>
-<li>Pass registration is slightly different in LLVM 2.0 (you now need an
- <tt>intptr_t</tt> in your constructor), as explained in the <a
- href="WritingAnLLVMPass.html#basiccode">Writing an LLVM Pass</a>
- document.</li>
-
-<li><tt>ConstantBool</tt>, <tt>ConstantIntegral</tt> and <tt>ConstantInt</tt>
- classes have been merged together, we now just have
- <tt>ConstantInt</tt>.</li>
-
-<li><tt>Type::IntTy</tt>, <tt>Type::UIntTy</tt>, <tt>Type::SByteTy</tt>, ... are
- replaced by <tt>Type::Int8Ty</tt>, <tt>Type::Int16Ty</tt>, etc. LLVM types
- have always corresponded to fixed size types
- (e.g. long was always 64-bits), but the type system no longer includes
- information about the sign of the type. Also, the
- <tt>Type::isPrimitiveType()</tt> method now returns false for integers.</li>
+<li>BrainF frontend by Sterling Stein.</li>
-<li>Several classes (<tt>CallInst</tt>, <tt>GetElementPtrInst</tt>,
- <tt>ConstantArray</tt>, etc), that once took <tt>std::vector</tt> as
- arguments now take ranges instead. For example, you can create a
- <tt>GetElementPtrInst</tt> with code like:
-
- <pre>
- Value *Ops[] = { Op1, Op2, Op3 };
- GEP = new GetElementPtrInst(BasePtr, Ops, 3);
- </pre>
-
- This avoids creation of a temporary vector (and a call to malloc/free). If
- you have an <tt>std::vector</tt>, use code like this:
- <pre>
- std::vector<Value*> Ops = ...;
- GEP = new GetElementPtrInst(BasePtr, &Ops[0], Ops.size());
- </pre>
+<li>David Green contributed a new --enable-expensive-checks configure option
+which enables STL checking, and fixed several bugs exposed by it.</li>
- </li>
-
-<li><tt>CastInst</tt> is now abstract and its functionality is split into
- several parts, one for each of the <a href="LangRef.html#convertops">new
- cast instructions</a>.</li>
-
-<li><tt>Instruction::getNext()/getPrev()</tt> are now private (along with
- <tt>BasicBlock::getNext</tt>, etc), for efficiency reasons (they are now no
- longer just simple pointers). Please use <tt>BasicBlock::iterator</tt>, etc
- instead.
</li>
-<li><tt>Module::getNamedFunction()</tt> is now called
- <tt>Module::getFunction()</tt>.</li>
-
-<li><tt>SymbolTable.h</tt> has been split into <tt>ValueSymbolTable.h</tt> and
-<tt>TypeSymbolTable.h</tt>.</li>
</ul>
+
</div>
-
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="portability">Portability and Supported Platforms</a>
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