+++ /dev/null
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
- "http://www.w3.org/TR/html4/strict.dtd">
-<html>
-<head>
- <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
- <link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 2.6 Release Notes</title>
-</head>
-<body>
-
-<div class="doc_title">LLVM 2.6 Release Notes</div>
-
-<ol>
- <li><a href="#intro">Introduction</a></li>
- <li><a href="#subproj">Sub-project Status Update</a></li>
- <li><a href="#externalproj">External Projects Using LLVM 2.6</a></li>
- <li><a href="#whatsnew">What's New in LLVM 2.6?</a></li>
- <li><a href="GettingStarted.html">Installation Instructions</a></li>
- <li><a href="#portability">Portability and Supported Platforms</a></li>
- <li><a href="#knownproblems">Known Problems</a></li>
- <li><a href="#additionalinfo">Additional Information</a></li>
-</ol>
-
-<div class="doc_author">
- <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
-</div>
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="intro">Introduction</a>
-</div>
-<!-- *********************************************************************** -->
-
-<div class="doc_text">
-
-<p>This document contains the release notes for the LLVM Compiler
-Infrastructure, release 2.6. Here we describe the status of LLVM, including
-major improvements from the previous release and significant known problems.
-All LLVM releases may be downloaded from the <a
-href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
-
-<p>For more information about LLVM, including information about the latest
-release, please check out the <a href="http://llvm.org/">main LLVM
-web site</a>. If you have questions or comments, the <a
-href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
-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 a specific release, please see the
-<a href="http://llvm.org/releases/">releases page</a>.</p>
-
-</div>
-
-
-<!--
-Almost dead code.
- include/llvm/Analysis/LiveValues.h => Dan
- lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
- llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
--->
-
-
-<!-- Unfinished features in 2.6:
- gcc plugin.
- strong phi elim
- variable debug info for optimized code
- postalloc scheduler: anti dependence breaking, hazard recognizer?
- metadata
- loop dependence analysis
- ELF Writer? How stable?
- <li>PostRA scheduler improvements, ARM adoption (David Goodwin).</li>
- 2.7 supports the GDB 7.0 jit interfaces for debug info.
- 2.7 eliminates ADT/iterator.h
- -->
-
- <!-- for announcement email:
- Logo web page.
- llvm devmtg
- compiler_rt
- KLEE web page at klee.llvm.org
- Many new papers added to /pubs/
- Mention gcc plugin.
-
- -->
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="subproj">Sub-project Status Update</a>
-</div>
-<!-- *********************************************************************** -->
-
-<div class="doc_text">
-<p>
-The LLVM 2.6 distribution currently consists of code from the core LLVM
-repository (which roughly includes the LLVM optimizers, code generators
-and supporting tools), the Clang repository and the llvm-gcc repository. In
-addition to this code, the LLVM Project includes other sub-projects that are in
-development. Here we include updates on these subprojects.
-</p>
-
-</div>
-
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
-</div>
-
-<div class="doc_text">
-
-<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
-a set of new 'LLVM native' front-end technologies for the C family of languages.
-LLVM 2.6 is the first release to officially include Clang, and it provides a
-production quality C and Objective-C compiler. If you are interested in <a
-href="http://clang.llvm.org/performance.html">fast compiles</a> and
-<a href="http://clang.llvm.org/diagnostics.html">good diagnostics</a>, we
-encourage you to try it out. Clang currently compiles typical Objective-C code
-3x faster than GCC and compiles C code about 30% faster than GCC at -O0 -g
-(which is when the most pressure is on the frontend).</p>
-
-<p>In addition to supporting these languages, C++ support is also <a
-href="http://clang.llvm.org/cxx_status.html">well under way</a>, and mainline
-Clang is able to parse the libstdc++ 4.2 headers and even codegen simple apps.
-If you are interested in Clang C++ support or any other Clang feature, we
-strongly encourage you to get involved on the <a
-href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
-list</a>.</p>
-
-<p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
-
-<ul>
-<li>C and Objective-C support are now considered production quality.</li>
-<li>AuroraUX, FreeBSD and OpenBSD are now supported.</li>
-<li>Most of Objective-C 2.0 is now supported with the GNU runtime.</li>
-<li>Many many bugs are fixed and lots of features have been added.</li>
-</ul>
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="clangsa">Clang Static Analyzer</a>
-</div>
-
-<div class="doc_text">
-
-<p>Previously announced in the 2.4 and 2.5 LLVM releases, the Clang project also
-includes an early stage static source code analysis tool for <a
-href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
-in C and Objective-C programs. The tool performs checks to find
-bugs that occur on a specific path within a program.</p>
-
-<p>In the LLVM 2.6 time-frame, the analyzer core has undergone several important
-improvements and cleanups and now includes a new <em>Checker</em> interface that
-is intended to eventually serve as a basis for domain-specific checks. Further,
-in addition to generating HTML files for reporting analysis results, the
-analyzer can now also emit bug reports in a structured XML format that is
-intended to be easily readable by other programs.</p>
-
-<p>The set of checks performed by the static analyzer continues to expand, and
-future plans for the tool include full source-level inter-procedural analysis
-and deeper checks such as buffer overrun detection. There are many opportunities
-to extend and enhance the static analyzer, and anyone interested in working on
-this project is encouraged to get involved!</p>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
-</div>
-
-<div class="doc_text">
-<p>
-The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
-a JVM and a CLI Virtual Machine (Microsoft .NET is an
-implementation of the CLI) using LLVM for static and just-in-time
-compilation.</p>
-
-<p>
-VMKit version 0.26 builds with LLVM 2.6 and you can find it on its
-<a href="http://vmkit.llvm.org/releases/">web page</a>. The release includes
-bug fixes, cleanup and new features. The major changes are:</p>
-
-<ul>
-
-<li>A new llcj tool to generate shared libraries or executables of Java
- files.</li>
-<li>Cooperative garbage collection. </li>
-<li>Fast subtype checking (paper from Click et al [JGI'02]). </li>
-<li>Implementation of a two-word header for Java objects instead of the original
- three-word header. </li>
-<li>Better Java specification-compliance: division by zero checks, stack
- overflow checks, finalization and references support. </li>
-
-</ul>
-</div>
-
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
-</div>
-
-<div class="doc_text">
-<p>
-The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
-is a simple library that provides an implementation of the low-level
-target-specific hooks required by code generation and other runtime components.
-For example, when compiling for a 32-bit target, converting a double to a 64-bit
-unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
-function. The compiler-rt library provides highly optimized implementations of
-this and other low-level routines (some are 3x faster than the equivalent
-libgcc routines).</p>
-
-<p>
-All of the code in the compiler-rt project is available under the standard LLVM
-License, a "BSD-style" license.</p>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="klee">KLEE: Symbolic Execution and Automatic Test Case Generator</a>
-</div>
-
-<div class="doc_text">
-<p>
-The new LLVM <a href="http://klee.llvm.org/">KLEE project</a> is a symbolic
-execution framework for programs in LLVM bitcode form. KLEE tries to
-symbolically evaluate "all" paths through the application and records state
-transitions that lead to fault states. This allows it to construct testcases
-that lead to faults and can even be used to verify algorithms. For more
-details, please see the <a
-href="http://llvm.org/pubs/2008-12-OSDI-KLEE.html">OSDI 2008 paper</a> about
-KLEE.</p>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
-</div>
-
-<div class="doc_text">
-<p>
-The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
-gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
-<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (llvm.so)
-that is loaded by gcc at runtime. It uses the new gcc plugin architecture to
-disable the GCC optimizers and code generators, and schedule the LLVM optimizers
-and code generators (or direct output of LLVM IR) instead. Currently only Linux
-and Darwin are supported, and only on x86-32 and x86-64. It should be easy to
-add additional unix-like architectures and other processor families. In theory
-it should be possible to use <a href="http://dragonegg.llvm.org/">DragonEgg</a>
-with any language supported by gcc, however only C and Fortran work well for the
-moment. Ada and C++ work to some extent, while Java, Obj-C and Obj-C++ are so
-far entirely untested. Since gcc-4.5 has not yet been released, neither has
-<a href="http://dragonegg.llvm.org/">DragonEgg</a>. To build
-<a href="http://dragonegg.llvm.org/">DragonEgg</a> you will need to check out the
-development versions of <a href="http://gcc.gnu.org/svn.html/"> gcc</a>,
-<a href="http://llvm.org/docs/GettingStarted.html#checkout">llvm</a> and
-<a href="http://dragonegg.llvm.org/">DragonEgg</a> from their respective
-subversion repositories, and follow the instructions in the
-<a href="http://dragonegg.llvm.org/">DragonEgg</a> README.
-</p>
-
-</div>
-
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="mc">llvm-mc: Machine Code Toolkit</a>
-</div>
-
-<div class="doc_text">
-<p>
-The LLVM Machine Code (MC) Toolkit project is a (very early) effort to build
-better tools for dealing with machine code, object file formats, etc. The idea
-is to be able to generate most of the target specific details of assemblers and
-disassemblers from existing LLVM target .td files (with suitable enhancements),
-and to build infrastructure for reading and writing common object file formats.
-One of the first deliverables is to build a full assembler and integrate it into
-the compiler, which is predicted to substantially reduce compile time in some
-scenarios.
-</p>
-
-<p>In the LLVM 2.6 timeframe, the MC framework has grown to the point where it
-can reliably parse and pretty print (with some encoding information) a
-darwin/x86 .s file successfully, and has the very early phases of a Mach-O
-assembler in progress. Beyond the MC framework itself, major refactoring of the
-LLVM code generator has started. The idea is to make the code generator reason
-about the code it is producing in a much more semantic way, rather than a
-textual way. For example, the code generator now uses MCSection objects to
-represent section assignments, instead of text strings that print to .section
-directives.</p>
-
-<p>MC is an early and ongoing project that will hopefully continue to lead to
-many improvements in the code generator and build infrastructure useful for many
-other situations.
-</p>
-
-</div>
-
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="externalproj">External Open Source Projects Using LLVM 2.6</a>
-</div>
-<!-- *********************************************************************** -->
-
-<div class="doc_text">
-
-<p>An exciting aspect of LLVM is that it is used as an enabling technology for
- a lot of other language and tools projects. This section lists some of the
- projects that have already been updated to work with LLVM 2.6.</p>
-</div>
-
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="Rubinius">Rubinius</a>
-</div>
-
-<div class="doc_text">
-<p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
-for running Ruby code which strives to write as much of the core class
-implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
-uses LLVM to optimize and compile ruby code down to machine code. Techniques
-such as type feedback, method inlining, and uncommon traps are all used to
-remove dynamism from ruby execution and increase performance.</p>
-
-<p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
-a counter based JIT, type feedback and speculative method inlining.
-</p>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="macruby">MacRuby</a>
-</div>
-
-<div class="doc_text">
-
-<p>
-<a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
-core Mac OS X technologies, such as the Objective-C common runtime and garbage
-collector and the CoreFoundation framework. It is principally developed by
-Apple and aims at enabling the creation of full-fledged Mac OS X applications.
-</p>
-
-<p>
-MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
-expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
-handling.</p>
-
-</div>
-
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="pure">Pure</a>
-</div>
-
-<div class="doc_text">
-<p>
-<a href="http://pure-lang.googlecode.com/">Pure</a>
-is an algebraic/functional programming language based on term rewriting.
-Programs are collections of equations which are used to evaluate expressions in
-a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
-lexical closures, a hygienic macro system (also based on term rewriting),
-built-in list and matrix support (including list and matrix comprehensions) and
-an easy-to-use C interface. The interpreter uses LLVM as a backend to
- JIT-compile Pure programs to fast native code.</p>
-
-<p>Pure versions 0.31 and later have been tested and are known to work with
-LLVM 2.6 (and continue to work with older LLVM releases >= 2.3 as well).
-</p>
-</div>
-
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="ldc">LLVM D Compiler</a>
-</div>
-
-<div class="doc_text">
-<p>
-<a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
-the D Programming Language using the LLVM optimizer and code generator.
-The LDC project works great with the LLVM 2.6 release. General improvements in
-this
-cycle have included new inline asm constraint handling, better debug info
-support, general bug fixes and better x86-64 support. This has allowed
-some major improvements in LDC, getting it much closer to being as
-fully featured as the original DMD compiler from DigitalMars.
-</p>
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="RoadsendPHP">Roadsend PHP</a>
-</div>
-
-<div class="doc_text">
-<p>
-<a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
-source implementation of the PHP programming
-language that uses LLVM for its optimizer, JIT and static compiler. This is a
-reimplementation of an earlier project that is now based on LLVM.</p>
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="UnladenSwallow">Unladen Swallow</a>
-</div>
-
-<div class="doc_text">
-<p>
-<a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
-branch of <a href="http://python.org/">Python</a> intended to be fully
-compatible and significantly faster. It uses LLVM's optimization passes and JIT
-compiler.</p>
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="llvm-lua">llvm-lua</a>
-</div>
-
-<div class="doc_text">
-<p>
-<a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
-and static compiling support to the Lua VM. Lua bytecode is analyzed to
-remove type checks, then LLVM is used to compile the bytecode down to machine
-code.</p>
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="icedtea">IcedTea Java Virtual Machine Implementation</a>
-</div>
-
-<div class="doc_text">
-<p>
-<a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
-harness to build OpenJDK using only free software build tools and to provide
-replacements for the not-yet free parts of OpenJDK. One of the extensions that
-IcedTea provides is a new JIT compiler named <a
-href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
-to provide native code generation without introducing processor-dependent
-code.
-</p>
-</div>
-
-
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="whatsnew">What's New in LLVM 2.6?</a>
-</div>
-<!-- *********************************************************************** -->
-
-<div class="doc_text">
-
-<p>This release includes a huge number of bug fixes, performance tweaks and
-minor improvements. Some of the major improvements and new features are listed
-in this section.
-</p>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="majorfeatures">Major New Features</a>
-</div>
-
-<div class="doc_text">
-
-<p>LLVM 2.6 includes several major new capabilities:</p>
-
-<ul>
-<li>New <a href="#compiler-rt">compiler-rt</a>, <A href="#klee">KLEE</a>
- and <a href="#mc">machine code toolkit</a> sub-projects.</li>
-<li>Debug information now includes line numbers when optimizations are enabled.
- This allows statistical sampling tools like OProfile and Shark to map
- samples back to source lines.</li>
-<li>LLVM now includes new experimental backends to support the MSP430, SystemZ
- and BlackFin architectures.</li>
-<li>LLVM supports a new <a href="GoldPlugin.html">Gold Linker Plugin</a> which
- enables support for <a href="LinkTimeOptimization.html">transparent
- link-time optimization</a> on ELF targets when used with the Gold binutils
- linker.</li>
-<li>LLVM now supports doing optimization and code generation on multiple
- threads. Please see the <a href="ProgrammersManual.html#threading">LLVM
- Programmer's Manual</a> for more information.</li>
-<li>LLVM now has experimental support for <a
- href="http://nondot.org/~sabre/LLVMNotes/EmbeddedMetadata.txt">embedded
- metadata</a> in LLVM IR, though the implementation is not guaranteed to be
- final and the .bc file format may change in future releases. Debug info
- does not yet use this format in LLVM 2.6.</li>
-</ul>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="coreimprovements">LLVM IR and Core Improvements</a>
-</div>
-
-<div class="doc_text">
-<p>LLVM IR has several new features for better support of new targets and that
-expose new optimization opportunities:</p>
-
-<ul>
-<li>The <a href="LangRef.html#i_add">add</a>, <a
- href="LangRef.html#i_sub">sub</a> and <a href="LangRef.html#i_mul">mul</a>
- instructions have been split into integer and floating point versions (like
- divide and remainder), introducing new <a
- href="LangRef.html#i_fadd">fadd</a>, <a href="LangRef.html#i_fsub">fsub</a>,
- and <a href="LangRef.html#i_fmul">fmul</a> instructions.</li>
-<li>The <a href="LangRef.html#i_add">add</a>, <a
- href="LangRef.html#i_sub">sub</a> and <a href="LangRef.html#i_mul">mul</a>
- instructions now support optional "nsw" and "nuw" bits which indicate that
- the operation is guaranteed to not overflow (in the signed or
- unsigned case, respectively). This gives the optimizer more information and
- can be used for things like C signed integer values, which are undefined on
- overflow.</li>
-<li>The <a href="LangRef.html#i_sdiv">sdiv</a> instruction now supports an
- optional "exact" flag which indicates that the result of the division is
- guaranteed to have a remainder of zero. This is useful for optimizing pointer
- subtraction in C.</li>
-<li>The <a href="LangRef.html#i_getelementptr">getelementptr</a> instruction now
- supports arbitrary integer index values for array/pointer indices. This
- allows for better code generation on 16-bit pointer targets like PIC16.</li>
-<li>The <a href="LangRef.html#i_getelementptr">getelementptr</a> instruction now
- supports an "inbounds" optimization hint that tells the optimizer that the
- pointer is guaranteed to be within its allocated object.</li>
-<li>LLVM now support a series of new linkage types for global values which allow
- for better optimization and new capabilities:
- <ul>
- <li><a href="LangRef.html#linkage_linkonce">linkonce_odr</a> and
- <a href="LangRef.html#linkage_weak">weak_odr</a> have the same linkage
- semantics as the non-"odr" linkage types. The difference is that these
- linkage types indicate that all definitions of the specified function
- are guaranteed to have the same semantics. This allows inlining
- templates functions in C++ but not inlining weak functions in C,
- which previously both got the same linkage type.</li>
- <li><a href="LangRef.html#linkage_available_externally">available_externally
- </a> is a new linkage type that gives the optimizer visibility into the
- definition of a function (allowing inlining and side effect analysis)
- but that does not cause code to be generated. This allows better
- optimization of "GNU inline" functions, extern templates, etc.</li>
- <li><a href="LangRef.html#linkage_linker_private">linker_private</a> is a
- new linkage type (which is only useful on Mac OS X) that is used for
- some metadata generation and other obscure things.</li>
- </ul></li>
-<li>Finally, target-specific intrinsics can now return multiple values, which
- is useful for modeling target operations with multiple results.</li>
-</ul>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="optimizer">Optimizer Improvements</a>
-</div>
-
-<div class="doc_text">
-
-<p>In addition to a large array of minor performance tweaks and bug fixes, this
-release includes a few major enhancements and additions to the optimizers:</p>
-
-<ul>
-
-<li>The <a href="Passes.html#scalarrepl">Scalar Replacement of Aggregates</a>
- pass has many improvements that allow it to better promote vector unions,
- variables which are memset, and much more strange code that can happen to
- do bitfield accesses to register operations. An interesting change is that
- it now produces "unusual" integer sizes (like i1704) in some cases and lets
- other optimizers clean things up.</li>
-<li>The <a href="Passes.html#loop-reduce">Loop Strength Reduction</a> pass now
- promotes small integer induction variables to 64-bit on 64-bit targets,
- which provides a major performance boost for much numerical code. It also
- promotes shorts to int on 32-bit hosts, etc. LSR now also analyzes pointer
- expressions (e.g. getelementptrs), as well as integers.</li>
-<li>The <a href="Passes.html#gvn">GVN</a> pass now eliminates partial
- redundancies of loads in simple cases.</li>
-<li>The <a href="Passes.html#inline">Inliner</a> now reuses stack space when
- inlining similar arrays from multiple callees into one caller.</li>
-<li>LLVM includes a new experimental Static Single Information (SSI)
- construction pass.</li>
-
-</ul>
-
-</div>
-
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="executionengine">Interpreter and JIT Improvements</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
-<li>LLVM has a new "EngineBuilder" class which makes it more obvious how to
- set up and configure an ExecutionEngine (a JIT or interpreter).</li>
-<li>The JIT now supports generating more than 16M of code.</li>
-<li>When configured with <tt>--with-oprofile</tt>, the JIT can now inform
- OProfile about JIT'd code, allowing OProfile to get line number and function
- name information for JIT'd functions.</li>
-<li>When "libffi" is available, the LLVM interpreter now uses it, which supports
- calling almost arbitrary external (natively compiled) functions.</li>
-<li>Clients of the JIT can now register a 'JITEventListener' object to receive
- callbacks when the JIT emits or frees machine code. The OProfile support
- uses this mechanism.</li>
-</ul>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="codegen">Target Independent Code Generator Improvements</a>
-</div>
-
-<div class="doc_text">
-
-<p>We have put a significant amount of work into the code generator
-infrastructure, which allows us to implement more aggressive algorithms and make
-it run faster:</p>
-
-<ul>
-
-<li>The <tt>llc -asm-verbose</tt> option (exposed from llvm-gcc as <tt>-dA</tt>
- and clang as <tt>-fverbose-asm</tt> or <tt>-dA</tt>) now adds a lot of
- useful information in comments to
- the generated .s file. This information includes location information (if
- built with <tt>-g</tt>) and loop nest information.</li>
-<li>The code generator now supports a new MachineVerifier pass which is useful
- for finding bugs in targets and codegen passes.</li>
-<li>The Machine LICM is now enabled by default. It hoists instructions out of
- loops (such as constant pool loads, loads from read-only stubs, vector
- constant synthesization code, etc.) and is currently configured to only do
- so when the hoisted operation can be rematerialized.</li>
-<li>The Machine Sinking pass is now enabled by default. This pass moves
- side-effect free operations down the CFG so that they are executed on fewer
- paths through a function.</li>
-<li>The code generator now performs "stack slot coloring" of register spills,
- which allows spill slots to be reused. This leads to smaller stack frames
- in cases where there are lots of register spills.</li>
-<li>The register allocator has many improvements to take better advantage of
- commutable operations, various spiller peephole optimizations, and can now
- coalesce cross-register-class copies.</li>
-<li>Tblgen now supports multiclass inheritance and a number of new string and
- list operations like <tt>!(subst)</tt>, <tt>!(foreach)</tt>, <tt>!car</tt>,
- <tt>!cdr</tt>, <tt>!null</tt>, <tt>!if</tt>, <tt>!cast</tt>.
- These make the .td files more expressive and allow more aggressive factoring
- of duplication across instruction patterns.</li>
-<li>Target-specific intrinsics can now be added without having to hack VMCore to
- add them. This makes it easier to maintain out-of-tree targets.</li>
-<li>The instruction selector is better at propagating information about values
- (such as whether they are sign/zero extended etc.) across basic block
- boundaries.</li>
-<li>The SelectionDAG datastructure has new nodes for representing buildvector
- and <a href="http://llvm.org/PR2957">vector shuffle</a> operations. This
- makes operations and pattern matching more efficient and easier to get
- right.</li>
-<li>The Prolog/Epilog Insertion Pass now has experimental support for performing
- the "shrink wrapping" optimization, which moves spills and reloads around in
- the CFG to avoid doing saves on paths that don't need them.</li>
-<li>LLVM includes new experimental support for writing ELF .o files directly
- from the compiler. It works well for many simple C testcases, but doesn't
- support exception handling, debug info, inline assembly, etc.</li>
-<li>Targets can now specify register allocation hints through
- <tt>MachineRegisterInfo::setRegAllocationHint</tt>. A regalloc hint consists
- of hint type and physical register number. A hint type of zero specifies a
- register allocation preference. Other hint type values are target specific
- which are resolved by <tt>TargetRegisterInfo::ResolveRegAllocHint</tt>. An
- example is the ARM target which uses register hints to request that the
- register allocator provide an even / odd register pair to two virtual
- registers.</li>
-</ul>
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="x86">X86-32 and X86-64 Target Improvements</a>
-</div>
-
-<div class="doc_text">
-<p>New features of the X86 target include:
-</p>
-
-<ul>
-
-<li>SSE 4.2 builtins are now supported.</li>
-<li>GCC-compatible soft float modes are now supported, which are typically used
- by OS kernels.</li>
-<li>X86-64 now models implicit zero extensions better, which allows the code
- generator to remove a lot of redundant zexts. It also models the 8-bit "H"
- registers as subregs, which allows them to be used in some tricky
- situations.</li>
-<li>X86-64 now supports the "local exec" and "initial exec" thread local storage
- model.</li>
-<li>The vector forms of the <a href="LangRef.html#i_icmp">icmp</a> and <a
- href="LangRef.html#i_fcmp">fcmp</a> instructions now select to efficient
- SSE operations.</li>
-<li>Support for the win64 calling conventions have improved. The primary
- missing feature is support for varargs function definitions. It seems to
- work well for many win64 JIT purposes.</li>
-<li>The X86 backend has preliminary support for <a
- href="CodeGenerator.html#x86_memory">mapping address spaces to segment
- register references</a>. This allows you to write GS or FS relative memory
- accesses directly in LLVM IR for cases where you know exactly what you're
- doing (such as in an OS kernel). There are some known problems with this
- support, but it works in simple cases.</li>
-<li>The X86 code generator has been refactored to move all global variable
- reference logic to one place
- (<tt>X86Subtarget::ClassifyGlobalReference</tt>) which
- makes it easier to reason about.</li>
-
-</ul>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="pic16">PIC16 Target Improvements</a>
-</div>
-
-<div class="doc_text">
-<p>New features of the PIC16 target include:
-</p>
-
-<ul>
-<li>Support for floating-point, indirect function calls, and
- passing/returning aggregate types to functions.
-<li>The code generator is able to generate debug info into output COFF files.
-<li>Support for placing an object into a specific section or at a specific
- address in memory.</li>
-</ul>
-
-<p>Things not yet supported:</p>
-
-<ul>
-<li>Variable arguments.</li>
-<li>Interrupts/programs.</li>
-</ul>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="ARM">ARM Target Improvements</a>
-</div>
-
-<div class="doc_text">
-<p>New features of the ARM target include:
-</p>
-
-<ul>
-
-<li>Preliminary support for processors, such as the Cortex-A8 and Cortex-A9,
-that implement version v7-A of the ARM architecture. The ARM backend now
-supports both the Thumb2 and Advanced SIMD (Neon) instruction sets.</li>
-
-<li>The AAPCS-VFP "hard float" calling conventions are also supported with the
-<tt>-float-abi=hard</tt> flag.</li>
-
-<li>The ARM calling convention code is now tblgen generated instead of resorting
- to C++ code.</li>
-</ul>
-
-<p>These features are still somewhat experimental
-and subject to change. The Neon intrinsics, in particular, may change in future
-releases of LLVM. ARMv7 support has progressed a lot on top of tree since 2.6
-branched.</p>
-
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="OtherTarget">Other Target Specific Improvements</a>
-</div>
-
-<div class="doc_text">
-<p>New features of other targets include:
-</p>
-
-<ul>
-<li>Mips now supports O32 Calling Convention.</li>
-<li>Many improvements to the 32-bit PowerPC SVR4 ABI (used on powerpc-linux)
- support, lots of bugs fixed.</li>
-<li>Added support for the 64-bit PowerPC SVR4 ABI (used on powerpc64-linux).
- Needs more testing.</li>
-</ul>
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="newapis">New Useful APIs</a>
-</div>
-
-<div class="doc_text">
-
-<p>This release includes a number of new APIs that are used internally, which
- may also be useful for external clients.
-</p>
-
-<ul>
-<li>New <a href="http://llvm.org/doxygen/PrettyStackTrace_8h-source.html">
- <tt>PrettyStackTrace</tt> class</a> allows crashes of llvm tools (and applications
- that integrate them) to provide more detailed indication of what the
- compiler was doing at the time of the crash (e.g. running a pass).
- At the top level for each LLVM tool, it includes the command line arguments.
- </li>
-<li>New <a href="http://llvm.org/doxygen/StringRef_8h-source.html">StringRef</a>
- and <a href="http://llvm.org/doxygen/Twine_8h-source.html">Twine</a> classes
- make operations on character ranges and
- string concatenation to be more efficient. <tt>StringRef</tt> is just a <tt>const
- char*</tt> with a length, <tt>Twine</tt> is a light-weight rope.</li>
-<li>LLVM has new <tt>WeakVH</tt>, <tt>AssertingVH</tt> and <tt>CallbackVH</tt>
- classes, which make it easier to write LLVM IR transformations. <tt>WeakVH</tt>
- is automatically drops to null when the referenced <tt>Value</tt> is deleted,
- and is updated across a <tt>replaceAllUsesWith</tt> operation.
- <tt>AssertingVH</tt> aborts the program if the
- referenced value is destroyed while it is being referenced. <tt>CallbackVH</tt>
- is a customizable class for handling value references. See <a
- href="http://llvm.org/doxygen/ValueHandle_8h-source.html">ValueHandle.h</a>
- for more information.</li>
-<li>The new '<a href="http://llvm.org/doxygen/Triple_8h-source.html">Triple
- </a>' class centralizes a lot of logic that reasons about target
- triples.</li>
-<li>The new '<a href="http://llvm.org/doxygen/ErrorHandling_8h-source.html">
- llvm_report_error()</a>' set of APIs allows tools to embed the LLVM
- optimizer and backend and recover from previously unrecoverable errors.</li>
-<li>LLVM has new abstractions for <a
- href="http://llvm.org/doxygen/Atomic_8h-source.html">atomic operations</a>
- and <a href="http://llvm.org/doxygen/RWMutex_8h-source.html">reader/writer
- locks</a>.</li>
-<li>LLVM has new <a href="http://llvm.org/doxygen/SourceMgr_8h-source.html">
- <tt>SourceMgr</tt> and <tt>SMLoc</tt> classes</a> which implement caret
- diagnostics and basic include stack processing for simple parsers. It is
- used by tablegen, llvm-mc, the .ll parser and FileCheck.</li>
-</ul>
-
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="otherimprovements">Other Improvements and New Features</a>
-</div>
-
-<div class="doc_text">
-<p>Other miscellaneous features include:</p>
-
-<ul>
-<li>LLVM now includes a new internal '<a
- href="http://llvm.org/cmds/FileCheck.html">FileCheck</a>' tool which allows
- writing much more accurate regression tests that run faster. Please see the
- <a href="TestingGuide.html#FileCheck">FileCheck section of the Testing
- Guide</a> for more information.</li>
-<li>LLVM profile information support has been significantly improved to produce
-correct use counts, and has support for edge profiling with reduced runtime
-overhead. Combined, the generated profile information is both more correct and
-imposes about half as much overhead (2.6. from 12% to 6% overhead on SPEC
-CPU2000).</li>
-<li>The C bindings (in the llvm/include/llvm-c directory) include many newly
- supported APIs.</li>
-<li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005
- programming language.</li>
-
-<li>The LLVMC driver has several new features:
- <ul>
- <li>Dynamic plugins now work on Windows.</li>
- <li>New option property: init. Makes possible to provide default values for
- options defined in plugins (interface to <tt>cl::init</tt>).</li>
- <li>New example: Skeleton, shows how to create a standalone LLVMC-based
- driver.</li>
- <li>New example: mcc16, a driver for the PIC16 toolchain.</li>
- </ul>
-</li>
-
-</ul>
-
-</div>
-
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="changes">Major Changes and Removed Features</a>
-</div>
-
-<div class="doc_text">
-
-<p>If you're already an LLVM user or developer with out-of-tree changes based
-on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading
-from the previous release.</p>
-
-<ul>
-<li>The Itanium (IA64) backend has been removed. It was not actively supported
- and had bitrotted.</li>
-<li>The BigBlock register allocator has been removed, it had also bitrotted.</li>
-<li>The C Backend (<tt>-march=c</tt>) is no longer considered part of the LLVM release
-criteria. We still want it to work, but no one is maintaining it and it lacks
-support for arbitrary precision integers and other important IR features.</li>
-
-<li>All LLVM tools now default to overwriting their output file, behaving more
- like standard unix tools. Previously, this only happened with the '<tt>-f</tt>'
- option.</li>
-<li>LLVM build now builds all libraries as .a files instead of some
- libraries as relinked .o files. This requires some APIs like
- InitializeAllTargets.h.
- </li>
-</ul>
-
-
-<p>In addition, many APIs have changed in this release. Some of the major LLVM
-API changes are:</p>
-
-<ul>
-<li>All uses of <tt>hash_set</tt> and <tt>hash_map</tt> have been removed from
- the LLVM tree and the wrapper headers have been removed.</li>
-<li>The llvm/Streams.h and <tt>DOUT</tt> member of Debug.h have been removed. The
- <tt>llvm::Ostream</tt> class has been completely removed and replaced with
- uses of <tt>raw_ostream</tt>.</li>
-<li>LLVM's global uniquing tables for <tt>Type</tt>s and <tt>Constant</tt>s have
- been privatized into members of an <tt>LLVMContext</tt>. A number of APIs
- now take an <tt>LLVMContext</tt> as a parameter. To smooth the transition
- for clients that will only ever use a single context, the new
- <tt>getGlobalContext()</tt> API can be used to access a default global
- context which can be passed in any and all cases where a context is
- required.
-<li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
-<li>The <tt>Add</tt>, <tt>Sub</tt> and <tt>Mul</tt> operators are no longer
- overloaded for floating-point types. Floating-point addition, subtraction
- and multiplication are now represented with new operators <tt>FAdd</tt>,
- <tt>FSub</tt> and <tt>FMul</tt>. In the <tt>IRBuilder</tt> API,
- <tt>CreateAdd</tt>, <tt>CreateSub</tt>, <tt>CreateMul</tt> and
- <tt>CreateNeg</tt> should only be used for integer arithmetic now;
- <tt>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt> and
- <tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
-<li>The <tt>DynamicLibrary</tt> class can no longer be constructed, its functionality has
- moved to static member functions.</li>
-<li><tt>raw_fd_ostream</tt>'s constructor for opening a given filename now
- takes an extra <tt>Force</tt> argument. If <tt>Force</tt> is set to
- <tt>false</tt>, an error will be reported if a file with the given name
- already exists. If <tt>Force</tt> is set to <tt>true</tt>, the file will
- be silently truncated (which is the behavior before this flag was
- added).</li>
-<li><tt>SCEVHandle</tt> no longer exists, because reference counting is no
- longer done for <tt>SCEV*</tt> objects, instead <tt>const SCEV*</tt>
- should be used.</li>
-
-<li>Many APIs, notably <tt>llvm::Value</tt>, now use the <tt>StringRef</tt>
-and <tt>Twine</tt> classes instead of passing <tt>const char*</tt>
-or <tt>std::string</tt>, as described in
-the <a href="ProgrammersManual.html#string_apis">Programmer's Manual</a>. Most
-clients should be unaffected by this transition, unless they are used to
-<tt>Value::getName()</tt> returning a string. Here are some tips on updating to
-2.6:
- <ul>
- <li><tt>getNameStr()</tt> is still available, and matches the old
- behavior. Replacing <tt>getName()</tt> calls with this is an safe option,
- although more efficient alternatives are now possible.</li>
-
- <li>If you were just relying on <tt>getName()</tt> being able to be sent to
- a <tt>std::ostream</tt>, consider migrating
- to <tt>llvm::raw_ostream</tt>.</li>
-
- <li>If you were using <tt>getName().c_str()</tt> to get a <tt>const
- char*</tt> pointer to the name, you can use <tt>getName().data()</tt>.
- Note that this string (as before), may not be the entire name if the
- name contains embedded null characters.</li>
-
- <li>If you were using <tt>operator +</tt> on the result of <tt>getName()</tt> and
- treating the result as an <tt>std::string</tt>, you can either
- use <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
- could move to a <tt>Twine</tt> based design.</li>
-
- <li><tt>isName()</tt> should be replaced with comparison
- against <tt>getName()</tt> (this is now efficient).
- </ul>
-</li>
-
-<li>The registration interfaces for backend Targets has changed (what was
-previously <tt>TargetMachineRegistry</tt>). For backend authors, see the <a
-href="WritingAnLLVMBackend.html#TargetRegistration">Writing An LLVM Backend</a>
-guide. For clients, the notable API changes are:
- <ul>
- <li><tt>TargetMachineRegistry</tt> has been renamed
- to <tt>TargetRegistry</tt>.</li>
-
- <li>Clients should move to using the <tt>TargetRegistry::lookupTarget()</tt>
- function to find targets.</li>
- </ul>
-</li>
-</ul>
-
-</div>
-
-
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="portability">Portability and Supported Platforms</a>
-</div>
-<!-- *********************************************************************** -->
-
-<div class="doc_text">
-
-<p>LLVM is known to work on the following platforms:</p>
-
-<ul>
-<li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
- Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
- systems).</li>
-<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
- and 64-bit modes.</li>
-<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
-<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
- support is available for native builds with Visual C++).</li>
-<li>Sun UltraSPARC workstations running Solaris 10.</li>
-<li>Alpha-based machines running Debian GNU/Linux.</li>
-</ul>
-
-<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
-to the machine and operating system on which it is built. However, minor
-porting may be required to get LLVM to work on new platforms. We welcome your
-portability patches and reports of successful builds or error messages.</p>
-
-</div>
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="knownproblems">Known Problems</a>
-</div>
-<!-- *********************************************************************** -->
-
-<div class="doc_text">
-
-<p>This section contains significant known problems with the LLVM system,
-listed by component. If you run into a problem, please check the <a
-href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
-there isn't already one.</p>
-
-<ul>
-<li>The llvm-gcc bootstrap will fail with some versions of binutils (e.g. 2.15)
- with a message of "<tt><a href="http://llvm.org/PR5004">Error: can not do 8
- byte pc-relative relocation</a></tt>" when building C++ code. We intend to
- fix this on mainline, but a workaround for 2.6 is to upgrade to binutils
- 2.17 or later.</li>
-
-<li>LLVM will not correctly compile on Solaris and/or OpenSolaris
-using the stock GCC 3.x.x series 'out the box',
-See: <a href="#brokengcc">Broken versions of GCC and other tools</a>.
-However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
-for x86/x86-64 has been made available from the third party AuroraUX Project
-that has been meticulously tested for bootstrapping LLVM & Clang.</li>
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="experimental">Experimental features included with this release</a>
-</div>
-
-<div class="doc_text">
-
-<p>The following components of this LLVM release are either untested, known to
-be broken or unreliable, or are in early development. These components should
-not be relied on, and bugs should not be filed against them, but they may be
-useful to some people. In particular, if you would like to work on one of these
-components, please contact us on the <a
-href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
-
-<ul>
-<li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430 and SystemZ backends are
- experimental.</li>
-<li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
- supported value for this option. The ELF writer is experimental.</li>
-<li>The implementation of Andersen's Alias Analysis has many known bugs.</li>
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="x86-be">Known problems with the X86 back-end</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
- <li>The X86 backend does not yet support
- all <a href="http://llvm.org/PR879">inline assembly that uses the X86
- floating point stack</a>. It supports the 'f' and 't' constraints, but not
- 'u'.</li>
- <li>The X86 backend generates inefficient floating point code when configured
- to generate code for systems that don't have SSE2.</li>
- <li>Win64 code generation wasn't widely tested. Everything should work, but we
- expect small issues to happen. Also, llvm-gcc cannot build the mingw64
- runtime currently due
- to <a href="http://llvm.org/PR2255">several</a>
- <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
- the
- 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
- <li>The X86-64 backend does not yet support the LLVM IR instruction
- <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
- argument constructs on X86-64 by lowering them manually.</li>
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="ppc-be">Known problems with the PowerPC back-end</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
-<li>The Linux PPC32/ABI support needs testing for the interpreter and static
-compilation, and lacks support for debug information.</li>
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="arm-be">Known problems with the ARM back-end</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
-<li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
-and not well tested. Some features may not work at all, and the code quality
-may be poor in some cases.</li>
-<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
-processors, thumb programs can crash or produce wrong
-results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
-<li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
-</li>
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="sparc-be">Known problems with the SPARC back-end</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
-<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
- support the 64-bit SPARC ABI (-m64).</li>
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="mips-be">Known problems with the MIPS back-end</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
-<li>64-bit MIPS targets are not supported yet.</li>
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="alpha-be">Known problems with the Alpha back-end</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
-
-<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
-appropriate nops inserted to ensure restartability.</li>
-
-</ul>
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="c-be">Known problems with the C back-end</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
-<li><a href="http://llvm.org/PR802">The C backend has only basic support for
- inline assembly code</a>.</li>
-<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
- C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
- C++ code compiled with <tt>llc</tt> or native compilers.</li>
-<li>The C backend does not support all exception handling constructs.</li>
-<li>The C backend does not support arbitrary precision integers.</li>
-</ul>
-
-</div>
-
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
-</div>
-
-<div class="doc_text">
-
-<p>The only major language feature of GCC not supported by llvm-gcc is
- the <tt>__builtin_apply</tt> family of builtins. However, some extensions
- are only supported on some targets. For example, trampolines are only
- supported on some targets (these are used when you take the address of a
- nested function).</p>
-
-<p>If you run into GCC extensions which are not supported, please let us know.
-</p>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="c++-fe">Known problems with the llvm-gcc 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 works well on the X86 and PowerPC targets. Currently
- only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
-</ul>
-
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
-</div>
-
-<div class="doc_text">
-<ul>
-<li>Fortran support generally works, but there are still several unresolved bugs
- in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
- tools/gfortran component for details.</li>
-</ul>
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
-</div>
-
-<div class="doc_text">
-The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
-technology, and problems should be expected.
-<ul>
-<li>The Ada front-end currently only builds on X86-32. This is mainly due
-to lack of trampoline support (pointers to nested functions) on other platforms.
-However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
-which does support trampolines.</li>
-<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
-This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
-exception handling, which is used internally by the compiler.
-Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
-<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
-and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
-(c380004 also fails with gcc-4.2 mainline).
-If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
-causes the compiler to go into an infinite loop, using up all system memory.</li>
-<li>Some GCC specific Ada tests continue to crash the compiler.</li>
-<li>The <tt>-E</tt> binder option (exception backtraces)
-<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
-crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
-<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
-or finish at a non-byte offset</a> in a record. Workaround: do not pack records
-or use representation clauses that result in a field of a non-discrete type
-starting or finishing in the middle of a byte.</li>
-<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
-'main' as generated by the Ada binder to be invalid</a>.
-Workaround: hand edit the file to use pointers for <tt>argv</tt> and
-<tt>envp</tt> rather than integers.</li>
-<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
-ignored</a>.</li>
-</ul>
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="ocaml-bindings">Known problems with the O'Caml bindings</a>
-</div>
-
-<div class="doc_text">
-
-<p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
-<tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
-<tt>Llvm.Linkage.Link_once</tt> will be correct. If you need any of the other linkage
-modes, you'll have to write an external C library in order to expose the
-functionality. This has been fixed in the trunk.</p>
-</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>
-
-<!-- *********************************************************************** -->
-
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