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691 lines
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link rel="stylesheet" href="llvm.css" type="text/css">
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<title>LLVM 2.1 Release Notes</title>
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</head>
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<body>
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<div class="doc_title">LLVM 2.1 Release Notes</div>
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<ol>
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<li><a href="#intro">Introduction</a></li>
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<li><a href="#whatsnew">What's New?</a></li>
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<li><a href="GettingStarted.html">Installation Instructions</a></li>
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<li><a href="#portability">Portability and Supported Platforms</a></li>
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<li><a href="#knownproblems">Known Problems</a>
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<li><a href="#additionalinfo">Additional Information</a></li>
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</ol>
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<div class="doc_author">
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<p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="intro">Introduction</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This document contains the release notes for the LLVM compiler
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infrastructure, release 2.1. Here we describe the status of LLVM, including
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major improvements from the previous release and any known problems. All LLVM
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releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
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releases web site</a>.</p>
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<p>For more information about LLVM, including information about the latest
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release, please check out the <a href="http://llvm.org/">main LLVM
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web site</a>. If you have questions or comments, the <a
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href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
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list</a> is a good place to send them.</p>
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<p>Note that if you are reading this file from a Subversion checkout or the
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main LLVM web page, this document applies to the <i>next</i> release, not the
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current one. To see the release notes for a specific releases, please see the
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<a href="http://llvm.org/releases/">releases page</a>.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="whatsnew">What's New?</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This is the twelfth public release of the LLVM Compiler Infrastructure.
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It includes many features and refinements from LLVM 2.0.</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="frontends">New Frontends</a>
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</div>
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<div class="doc_text">
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<p>LLVM 2.1 brings two new beta C front-ends. First, a new version of llvm-gcc
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based on GCC 4.2, innovatively called "llvm-gcc-4.2". This promises to bring
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FORTRAN and Ada support to LLVM as well as features like atomic builtins and
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OpenMP. None of these actually work yet, but don't let that stop you checking
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it out!</p>
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<p>Second, LLVM now includes its own native C and Objective-C front-end (C++ is
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in progress, but is not very far along) code named "<a
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href="http://clang.llvm.org/">clang</a>". This front-end has a number of great
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features, primarily aimed at source-level analysis and speeding up compile-time.
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At this point though, the LLVM Code Generator component is still very early in
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development, so it's mostly useful for people looking to build source-level
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analysis tools or source-to-source translators.</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="optimizer">Optimizer Improvements</a>
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</div>
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<div class="doc_text">
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<p>Some of the most noticable feature improvements this release have been in the
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optimizer, speeding it up and making it more aggressive. For example:</p>
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<ul>
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<li>Owen Anderson wrote the new MemoryDependenceAnalysis pass, which provides
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a lazy, caching layer on top of <a
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href="AliasAnalysis.html">AliasAnalysis</a>. He then used it to rewrite
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DeadStoreElimination which resulted in significantly better compile time in
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common cases, </li>
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<li>Owen implemented the new GVN pass, which is also based on
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MemoryDependenceAnalysis. This pass replaces GCSE/LoadVN in the standard
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set of passes, providing more aggressive optimization at a some-what
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improved compile-time cost.</li>
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<li>Owen implemented GVN-PRE, a partial redundancy elimination algorithm that
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shares some details with the new GVN pass. It is still in need of compile
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time tuning, and is not turned on by default.</li>
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<li>Devang merged ETForest and DomTree into a single easier to use data
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structure. This makes it more obvious which datastructure to choose
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(because there is only one) and makes the compiler more memory and time
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efficient (less stuff to keep up-to-date).</li>
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<li>Nick Lewycky improved loop trip count analysis to handle many more common
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cases.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="codegen">Code Generator Improvements</a>
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</div>
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<div class="doc_text">
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<p>One of the main focuses of this release was performance tuning and bug
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fixing. In addition to these, several new major changes occurred:</p>
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<ul>
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<li>Dale finished up the Tail Merging optimization in the code generator, and
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enabled it by default. This produces smaller code that is also faster in
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some cases.</li>
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<li>Christopher Lamb implemented support for virtual register sub-registers,
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which can be used to better model many forms of subregisters. As an example
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use, he modified the X86 backend to use this to model truncates and
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extends more accurately (leading to better code).</li>
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<li>Dan Gohman changed the way we represent vectors before legalization,
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significantly simplifying the SelectionDAG representation for these and
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making the code generator faster for vector code.</li>
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<li>Evan contributed a new target independent if-converter. While it is
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target independent, so far only the ARM backend uses it.</li>
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<li>Evan rewrote the way the register allocator handles rematerialization,
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allowing it to be much more effective on two-address targets like X86,
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and taught it to fold loads away when possible (also a big win on X86).</li>
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<li>Dan Gohman contributed support for better alignment and volatility handling
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in the code generator, and significantly enhanced alignment analysis for SSE
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load/store instructions. With his changes, an insufficiently-aligned SSE
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load instruction turns into <tt>movups</tt>, for example.</li>
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<li>Duraid Madina contributed a new "bigblock" register allocator, and Roman
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Levenstein contributed several big improvements. BigBlock is optimized for
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code that uses very large basic blocks. It is slightly slower than the
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"local" allocator, but produces much better code.</li>
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<li>David Greene refactored the register allocator to split coalescing out from
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allocation, making coalescers pluggable.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="targetspecific">Target Specific Improvements</a>
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</div>
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<div class="doc_text">
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<p>New features include:
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</p>
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<ul>
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<li>Bruno Cardoso Lopes contributed initial MIPS support. It is sufficient to
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run many small programs, but is still incomplete and is not yet
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fully performant.</li>
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<li>Bill Wendling added SSSE3 support to the X86 backend.</li>
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<li>Nicholas Geoffray contributed improved linux/ppc ABI and JIT support.</li>
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<li>Dale Johannesen rewrote handling of 32-bit float values in the X86 backend
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when using the floating point stack, fixing several nasty bugs.</li>
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<li>Dan contributed rematerialization support for the X86 backend, in addition
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to several X86-specific micro optimizations.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="llvmgccimprovements">llvm-gcc Improvements</a>
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</div>
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<div class="doc_text">
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<p>New features include:
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</p>
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<ul>
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<li>Duncan and Anton made significant progress chasing down a number of problems
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with C++ Zero-Cost exception handling in llvm-gcc 4.0 and 4.2. It is now at
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the point where it "just works" on linux/X86-32 and has partial support on
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other targets.</li>
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<li>Devang and Duncan fixed a huge number of bugs relating to bitfields, pragma
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pack, and variable sized fields in structures.</li>
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<li>Tanya implemented support for <tt>__attribute__((noinline))</tt> in
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llvm-gcc, and added support for generic variable annotations which are
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propagated into the LLVM IR, e.g.
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"<tt>int X __attribute__((annotate("myproperty")));</tt>".</li>
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<li>Sheng Zhou and Christopher Lamb implemented alias analysis support for
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"restrict" pointer arguments to functions.</li>
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<li>Duncan contributed support for trampolines (taking the address of a nested
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function). Currently this is only supported on the X86-32 target.</li>
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<li>Lauro Ramos Venancio contributed support to encode alignment info in
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load and store instructions, the foundation for other alignment-related
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work.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="coreimprovements">LLVM Core Improvements</a>
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</div>
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<div class="doc_text">
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<p>New features include:
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</p>
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<ul>
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<li>Neil Booth contributed a new "APFloat" class, which ensures that floating
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point representation and constant folding is not dependent on the host
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architecture that builds the application. This support is the foundation
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for "long double" support that will be wrapped up in LLVM 2.2.</li>
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<li>Based on the APFloat class, Dale redesigned the internals of the ConstantFP
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class and has been working on extending the core and optimizer components to
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support various target-specific 'long double's. We expect this work to be
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completed in LLVM 2.2.</li>
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<li>LLVM now provides an LLVMBuilder class, which makes it significantly easier
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to create LLVM IR instructions.</li>
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<li>Reid contributed support for intrinsics that take arbitrary integer typed
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arguments. Dan Gohman and Chandler extended it to support arbitrary
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floating point arguments and vectors.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="otherimprovements">Other Improvements</a>
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</div>
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<div class="doc_text">
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<p>New features include:
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</p>
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<ul>
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<li>Sterling Stein contributed a new BrainF frontend, located in llvm/examples.
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This shows a some of the more modern APIs for building a front-end, and
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demonstrates JIT compiler support.</li>
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<li>David Green contributed a new <tt>--enable-expensive-checks</tt> configure
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option which enables STL checking, and fixed several bugs exposed by
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it.</li>
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</ul>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="portability">Portability and Supported Platforms</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>LLVM is known to work on the following platforms:</p>
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<ul>
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<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
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(and probably other unix-like systems).</li>
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<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
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64-bit modes.</li>
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<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
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<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
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support is available for native builds with Visual C++).</li>
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<li>Sun UltraSPARC workstations running Solaris 8.</li>
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<li>Alpha-based machines running Debian GNU/Linux.</li>
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<li>Itanium-based machines running Linux and HP-UX.</li>
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</ul>
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<p>The core LLVM infrastructure uses
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<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
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to the machine and operating system on which it is built. However, minor
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porting may be required to get LLVM to work on new platforms. We welcome your
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portability patches and reports of successful builds or error messages.</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="knownproblems">Known Problems</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This section contains all known problems with the LLVM system, listed by
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component. As new problems are discovered, they will be added to these
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sections. If you run into a problem, please check the <a
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href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
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there isn't already one.</p>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="experimental">Experimental features included with this release</a>
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</div>
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<div class="doc_text">
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<p>The following components of this LLVM release are either untested, known to
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be broken or unreliable, or are in early development. These components should
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not be relied on, and bugs should not be filed against them, but they may be
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useful to some people. In particular, if you would like to work on one of these
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components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
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<ul>
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<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in a
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future release.</li>
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<li>The MSIL backend is experimental.</li>
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<li>The IA64 code generator is experimental.</li>
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<li>The Alpha backend is experimental.</li>
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<li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
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<tt>-filetype</tt> llc option.</li>
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</ul>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="x86-be">Known problems with the X86 back-end</a>
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</div>
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<div class="doc_text">
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<ul>
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<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
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assembly that uses the X86 floating point stack</a>.</li>
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<li>The X86 backend occasionally has <a href="http://llvm.org/PR1649">alignment
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problems</a> on operating systems that don't require 16-byte stack alignment
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(including most non-darwin OS's like linux).</li>
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</ul>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="ppc-be">Known problems with the PowerPC back-end</a>
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</div>
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<div class="doc_text">
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<ul>
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<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
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implement ordered FP comparisons</a>.</li>
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<li>The Linux PPC32/ABI support needs testing for the interpreter and static
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compilation, and lacks support for debug information.</li>
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</ul>
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</div>
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="arm-be">Known problems with the ARM back-end</a>
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</div>
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<div class="doc_text">
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<ul>
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<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
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processors, thumb programs can crash or produce wrong
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results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
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<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
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</li>
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<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
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programs compiled with LLVM. Please use more recent versions of QEMU.</li>
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</ul>
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|
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</div>
|
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|
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="sparc-be">Known problems with the SPARC back-end</a>
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</div>
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<div class="doc_text">
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<ul>
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<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
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support the 64-bit SPARC ABI (-m64).</li>
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</ul>
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|
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</div>
|
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|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="alpha-be">Known problems with the Alpha back-end</a>
|
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</div>
|
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|
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<div class="doc_text">
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<ul>
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<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
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appropriate nops inserted to ensure restartability.</li>
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</ul>
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</div>
|
|
|
|
<!-- ======================================================================= -->
|
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<div class="doc_subsection">
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<a name="ia64-be">Known problems with the IA64 back-end</a>
|
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</div>
|
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<div class="doc_text">
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<ul>
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<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
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made where the argument is not 16-byte aligned, as required on IA64. (Strictly
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speaking this is not a bug in the IA64 back-end; it will also be encountered
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when building C++ programs using the C back-end.)</li>
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<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
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ABI compliant layout of v-tables</a>. In particular, it just stores function
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pointers instead of function descriptors in the vtable. This bug prevents
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mixing C++ code compiled with LLVM with C++ objects compiled by other C++
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compilers.</li>
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<li>There are a few ABI violations which will lead to problems when mixing LLVM
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output with code built with other compilers, particularly for floating-point
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programs.</li>
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<li>Defining vararg functions is not supported (but calling them is ok).</li>
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<li>The Itanium backend has bitrotted somewhat.</li>
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</ul>
|
|
|
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</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="c-be">Known problems with the C back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
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|
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<ul>
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<li><a href="http://llvm.org/PR802">The C backend does not support inline
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assembly code</a>.</li>
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<li><a href="http://llvm.org/PR1126">The C backend does not support vectors
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yet</a>.</li>
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<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
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C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
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C++ code compiled with LLC or native compilers.</li>
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</ul>
|
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</div>
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|
|
|
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<!-- ======================================================================= -->
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<div class="doc_subsection">
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<a name="c-fe">Known problems with the C front-end</a>
|
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</div>
|
|
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<!-- _______________________________________________________________________ -->
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<div class="doc_subsubsection">Bugs</div>
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<div class="doc_text">
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|
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<p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
|
|
Optimization</a> on most platforms "out-of-the-box". Please inquire on the
|
|
llvmdev mailing list if you are interested.</p>
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|
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</div>
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<!-- _______________________________________________________________________ -->
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<div class="doc_subsubsection">
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Notes
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</div>
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|
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<div class="doc_text">
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<ul>
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|
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<li><p>"long double" is silently transformed by the front-end into "double". There
|
|
is no support for floating point data types of any size other than 32 and 64
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bits.</p></li>
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|
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<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
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|
See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
|
|
</li>
|
|
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<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
|
|
<ol>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>:
|
|
|
|
As in Algol and Pascal, lexical scoping of functions.
|
|
Nested functions are supported, but llvm-gcc does not support
|
|
taking the address of a nested function (except on the X86-32 target)
|
|
or non-local gotos.</li>
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|
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
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|
|
|
Declaring that functions have no side effects or that they can never
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|
return.<br>
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|
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<b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
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<tt>constructor</tt>, <tt>destructor</tt>,
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|
<tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
|
|
<tt>format_arg</tt>, <tt>non_null</tt>, <tt>noinline</tt>, <tt>noreturn</tt>, <tt>regparm</tt>
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|
<tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
|
|
<tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
|
|
|
|
<b>Ignored:</b> <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
|
|
<tt>malloc</tt>, <tt>no_instrument_function</tt></li>
|
|
</ol>
|
|
</li>
|
|
|
|
<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
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|
|
|
<ol>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
|
|
Other built-in functions.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
|
|
Specifying attributes of variables.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
|
|
Arrays whose length is computed at run time.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels and computed gotos.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc-3.4.0/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>: Arithmetic on <code>void</code>-pointers and function pointers.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
|
|
or arrays as values.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>: Casting to union type from any member of the union.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Comments.html#C_002b_002b-Comments">C++ Comments</a>: C++ comments are recognized.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character <ESC>.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.</li>
|
|
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
|
|
</ol></li>
|
|
|
|
</ul>
|
|
|
|
<p>If you run into GCC extensions which have not been included in any of these
|
|
lists, please let us know (also including whether or not they work).</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="c++-fe">Known problems with the C++ front-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The C++ front-end is considered to be fully
|
|
tested and works for a number of non-trivial programs, including LLVM
|
|
itself, Qt, Mozilla, etc.</p>
|
|
|
|
<ul>
|
|
<li>Exception handling only works well on the linux/X86-32 target.
|
|
In some cases, illegally throwing an exception does not result
|
|
in a call to terminate.</li>
|
|
|
|
<!-- NO EH Support!
|
|
|
|
<li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
|
|
performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
|
|
function and in the <tt>setjmp</tt> receiver function may not be run.
|
|
Objects in intervening stack frames will be destroyed, however (which is
|
|
better than most compilers).</li>
|
|
|
|
<li>The LLVM C++ front-end follows the <a
|
|
href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
|
|
This document, which is not Itanium specific, specifies a standard for name
|
|
mangling, class layout, v-table layout, RTTI formats, and other C++
|
|
representation issues. Because we use this API, code generated by the LLVM
|
|
compilers should be binary compatible with machine code generated by other
|
|
Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
|
|
<i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
|
|
different from the model used in the Itanium ABI, so <b>exceptions will not
|
|
interact correctly</b>. </li>
|
|
-->
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="additionalinfo">Additional Information</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>A wide variety of additional information is available on the <a
|
|
href="http://llvm.org">LLVM web page</a>, in particular in the <a
|
|
href="http://llvm.org/docs/">documentation</a> section. The web page also
|
|
contains versions of the API documentation which is up-to-date with the
|
|
Subversion version of the source code.
|
|
You can access versions of these documents specific to this release by going
|
|
into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
|
|
|
|
<p>If you have any questions or comments about LLVM, please feel free to contact
|
|
us via the <a href="http://llvm.org/docs/#maillist"> mailing
|
|
lists</a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
<hr>
|
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src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
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<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
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