<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 2.3 Release Notes</title>
+ <title>LLVM 2.8 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.3 Release Notes</div>
-
+<div class="doc_title">LLVM 2.8 Release Notes</div>
+
+<img align=right src="http://llvm.org/img/DragonSmall.png"
+ width="136" height="136" alt="LLVM Dragon Logo">
+
<ol>
<li><a href="#intro">Introduction</a></li>
- <li><a href="#whatsnew">What's New?</a></li>
+ <li><a href="#subproj">Sub-project Status Update</a></li>
+ <li><a href="#externalproj">External Projects Using LLVM 2.8</a></li>
+ <li><a href="#whatsnew">What's New in LLVM 2.8?</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><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>
+ <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
</div>
-<h1><font color="red">THIS IS A WORK IN PROGRESS FOR LLVM 2.3 (currently in
-progress on SVN HEAD)</font></h1>
+<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
+release.<br>
+You may prefer the
+<a href="http://llvm.org/releases/2.7/docs/ReleaseNotes.html">LLVM 2.7
+Release Notes</a>.</h1>
<!-- *********************************************************************** -->
<div class="doc_section">
<div class="doc_text">
-<p>This document contains the release notes for the LLVM compiler
-infrastructure, release 2.3. Here we describe the status of LLVM, including
-major improvements from the previous release and any known problems. All LLVM
-releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
-releases web site</a>.</p>
+<p>This document contains the release notes for the LLVM Compiler
+Infrastructure, release 2.8. 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>
+href="http://lists.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
+<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 releases, please see 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.
+ ABCD, GEPSplitterPass
+ MSIL backend?
+ lib/Transforms/Utils/SSI.cpp -> ABCD depends on it.
+-->
+
+
+<!-- Features that need text if they're finished for 2.8:
+ combiner-aa?
+ strong phi elim
+ llvm.dbg.value: variable debug info for optimized code
+ loop dependence analysis
+ -->
+
+ <!-- for announcement email:
+ Logo web page.
+ Many new papers added to /pubs/
+ -->
<!-- *********************************************************************** -->
<div class="doc_section">
- <a name="whatsnew">What's New?</a>
+ <a name="subproj">Sub-project Status Update</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
+<p>
+The LLVM 2.8 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>
-<p>This is the fourteenth public release of the LLVM Compiler Infrastructure.
-It includes many features and refinements from LLVM 2.2.</p>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
</div>
-<!-- Unfinished features in 2.3:
- Index Set Splitting not enabled by default
- Machine LICM
- Machine Sinking
- LegalizeDAGTypes
- -->
+<div class="doc_text">
+
+<p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
+C++, and Objective-C languages. Clang aims to provide a better user experience
+through expressive diagnostics, a high level of conformance to language
+standards, fast compilation, and low memory use. Like LLVM, Clang provides a
+modular, library-based architecture that makes it suitable for creating or
+integrating with other development tools. Clang is considered a
+production-quality compiler for C and Objective-C on x86 (32- and 64-bit).</p>
+
+<p>In the LLVM 2.7 time-frame, the Clang team has made many improvements:</p>
+
+<ul>
+
+<li>C++ Support: Clang is now capable of self-hosting! While still
+alpha-quality, Clang's C++ support has matured enough to build LLVM and Clang,
+and C++ is now enabled by default. See the <a
+href="http://clang.llvm.org/cxx_compatibility.html">Clang C++ compatibility
+page</a> for common C++ migration issues.</li>
+
+<li>Objective-C: Clang now includes experimental support for an updated
+Objective-C ABI on non-Darwin platforms. This includes support for non-fragile
+instance variables and accelerated proxies, as well as greater potential for
+future optimisations. The new ABI is used when compiling with the
+-fobjc-nonfragile-abi and -fgnu-runtime options. Code compiled with these
+options may be mixed with code compiled with GCC or clang using the old GNU ABI,
+but requires the libobjc2 runtime from the GNUstep project.</li>
+
+<li>New warnings: Clang contains a number of new warnings, including
+control-flow warnings (unreachable code, missing return statements in a
+non-<code>void</code> function, etc.), sign-comparison warnings, and improved
+format-string warnings.</li>
+
+<li>CIndex API and Python bindings: Clang now includes a C API as part of the
+CIndex library. Although we may make some changes to the API in the future, it
+is intended to be stable and has been designed for use by external projects. See
+the Clang
+doxygen <a href="http://clang.llvm.org/doxygen/group__CINDEX.html">CIndex</a>
+documentation for more details. The CIndex API also includes a preliminary
+set of Python bindings.</li>
+
+<li>ARM Support: Clang now has ABI support for both the Darwin and Linux ARM
+ABIs. Coupled with many improvements to the LLVM ARM backend, Clang is now
+suitable for use as a beta quality ARM compiler.</li>
+
+</ul>
+</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="deprecation">Removed features in LLVM 2.3</a>
+<a name="clangsa">Clang Static Analyzer</a>
</div>
<div class="doc_text">
-<p>LLVM 2.2 was the last LLVM release to support llvm-gcc 4.0 and llvm-upgrade.
-llvm-gcc 4.0 has been replaced with llvm-gcc 4.2. llvm-upgrade was useful for
-upgrading llvm 1.9 files to llvm 2.x syntax, but you can always use a previous
-llvm release to do this.</p>
+<p>The <a href="http://clang-analyzer.llvm.org/">Clang Static Analyzer</a>
+ project is an effort to use static source code analysis techniques to
+ automatically find bugs in C and Objective-C programs (and hopefully <a
+ href="http://clang-analyzer.llvm.org/dev_cxx.html">C++ in the
+ future</a>!). The tool is very good at finding bugs that occur on specific
+ paths through code, such as on error conditions.</p>
+
+<p>In the LLVM 2.7 time-frame, the analyzer core has made several major and
+ minor improvements, including better support for tracking the fields of
+ structures, initial support (not enabled by default yet) for doing
+ interprocedural (cross-function) analysis, and new checks have been added.
+</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="frontends">llvm-gcc 4.2 and clang</a>
+<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>
+With the release of LLVM 2.7, VMKit has shifted to a great framework for writing
+virtual machines. VMKit now offers precise and efficient garbage collection with
+multi-threading support, thanks to the MMTk memory management toolkit, as well
+as just in time and ahead of time compilation with LLVM. The major changes in
+VMKit 0.27 are:</p>
-<p>LLVM 2.3 fully supports llvm-gcc 4.2 front-end. </p>
+<ul>
-<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 LLVM optimizer
-and code generator. Currently, its C and Objective-C support is maturing
-nicely, and it has advanced source-to-source analysis and transformation
-capabilities. If you are interested in building source-level tools for C and
-Objective-C (and eventually C++), you should take a look. However, note that
-clang is not an official part of the LLVM 2.3 release. If you are interested in
-this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
+<li>Garbage collection: VMKit now uses the MMTk toolkit for garbage collectors.
+ The first collector to be ported is the MarkSweep collector, which is precise,
+ and drastically improves the performance of VMKit.</li>
+<li>Line number information in the JVM: by using the debug metadata of LLVM, the
+ JVM now supports precise line number information, useful when printing a stack
+ trace.</li>
+<li>Interface calls in the JVM: we implemented a variant of the Interface Method
+ Table technique for interface calls in the JVM.
+</li>
+</ul>
</div>
+
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="majorfeatures">Major New Features</a>
+<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. New in LLVM 2.7: compiler_rt now
+supports ARM targets.</p>
-<p>LLVM 2.3 includes several major new capabilities:</p>
+</div>
-<ul>
-</ul>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a>
+</div>
+<div class="doc_text">
+<p>
+<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
+gcc-4.5. Unlike llvm-gcc, which makes many intrusive changes to the underlying
+gcc-4.2 code, dragonegg in theory does not require any gcc-4.5 modifications
+whatsoever (currently one small patch is needed). This is thanks to the new
+<a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>, which
+makes it possible to modify the behaviour of gcc at runtime by loading a plugin,
+which is nothing more than a dynamic library which conforms to the gcc plugin
+interface. DragonEgg is a gcc plugin that causes the LLVM optimizers to be run
+instead of the gcc optimizers, and the LLVM code generators instead of the gcc
+code generators, just like llvm-gcc. To use it, you add
+"-fplugin=path/dragonegg.so" to the gcc-4.5 command line, and gcc-4.5 magically
+becomes llvm-gcc-4.5!
+</p>
+
+<p>
+DragonEgg is still a work in progress. Currently C works very well, while C++,
+Ada and Fortran work fairly well. All other languages either don't work at all,
+or only work poorly. For the moment only the x86-32 and x86-64 targets are
+supported, and only on linux and darwin (darwin needs an additional gcc patch).
+</p>
+
+<p>
+DragonEgg is a new project which is seeing its first release with llvm-2.7.
+</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 (aka MC) sub-project of LLVM was created to solve a number
+of problems in the realm of assembly, disassembly, object file format handling,
+and a number of other related areas that CPU instruction-set level tools work
+in. It is a sub-project of LLVM which provides it with a number of advantages
+over other compilers that do not have tightly integrated assembly-level tools.
+For a gentle introduction, please see the <a
+href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
+LLVM MC Project Blog Post</a>.
+</p>
+
+<p>2.7 includes major parts of the work required by the new MC Project. A few
+ targets have been refactored to support it, and work is underway to support a
+ native assembler in LLVM. This work is not complete in LLVM 2.7, but it has
+ made substantially more progress on LLVM mainline.</p>
+
+<p>One minor example of what MC can do is to transcode an AT&T syntax
+ X86 .s file into intel syntax. You can do this with something like:</p>
+<pre>
+ llvm-mc foo.s -output-asm-variant=1 -o foo-intel.s
+</pre>
+
+</div>
+
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="externalproj">External Open Source Projects Using LLVM 2.7</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 2.7.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="coreimprovements">LLVM Core Improvements</a>
+<a name="pure">Pure</a>
</div>
<div class="doc_text">
-<p>New features include:
+<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 0.43 and later have been tested and are known to work with
+LLVM 2.7 (and continue to work with older LLVM releases >= 2.5).</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="tce">TTA-based Codesign Environment (TCE)</a>
+</div>
+
+<div class="doc_text">
+<p>
+<a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing
+application-specific processors (ASP) based on the Transport triggered
+architecture (TTA). The toolset provides a complete co-design flow from C/C++
+programs down to synthesizable VHDL and parallel program binaries. Processor
+customization points include the register files, function units, supported
+operations, and the interconnection network.</p>
+
+<p>TCE uses llvm-gcc/Clang and LLVM for C/C++ language support, target
+independent optimizations and also for parts of code generation. It generates
+new LLVM-based code generators "on the fly" for the designed TTA processors and
+loads them in to the compiler backend as runtime libraries to avoid per-target
+recompilation of larger parts of the compiler chain.</p>
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="safecode">SAFECode Compiler</a>
+</div>
+
+<div class="doc_text">
+<p>
+<a href="http://safecode.cs.illinois.edu">SAFECode</a> is a memory safe C
+compiler built using LLVM. It takes standard, unannotated C code, analyzes the
+code to ensure that memory accesses and array indexing operations are safe, and
+instruments the code with run-time checks when safety cannot be proven
+statically.
+</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>
+<p>Icedtea6 1.8 and later have been tested and are known to work with
+LLVM 2.7 (and continue to work with older LLVM releases >= 2.6 as well).
+</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>
+<p>LLVM-Lua 1.2.0 have been tested and is known to work with LLVM 2.7.
+</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 based on
+core Mac OS technologies, sponsored by Apple Inc. It uses LLVM at runtime for
+optimization passes, JIT compilation and exception handling. It also allows
+static (ahead-of-time) compilation of Ruby code straight to machine code.
+</p>
+<p>The upcoming MacRuby 0.6 release works with LLVM 2.7.
+</p>
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="GHC">Glasgow Haskell Compiler (GHC)</a>
+</div>
+
+<div class="doc_text">
+<p>
+<a href="http://www.haskell.org/ghc/">GHC</a> is an open source,
+state-of-the-art programming suite for Haskell, a standard lazy
+functional programming language. It includes an optimizing static
+compiler generating good code for a variety of platforms, together
+with an interactive system for convenient, quick development.</p>
+
+<p>In addition to the existing C and native code generators, GHC now
+supports an <a
+href="http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/Backends/LLVM">LLVM
+code generator</a>. GHC supports LLVM 2.7.</p>
+
+</div>
+
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="whatsnew">What's New in LLVM 2.7?</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="orgchanges">LLVM Community Changes</a>
+</div>
+
+<div class="doc_text">
+
+<p>In addition to changes to the code, between LLVM 2.6 and 2.7, a number of
+organization changes have happened:
</p>
<ul>
+<li>LLVM has a new <a href="http://llvm.org/Logo.html">official logo</a>!</li>
+
+<li>Ted Kremenek and Doug Gregor have stepped forward as <a
+ href="http://llvm.org/docs/DeveloperPolicy.html#owners">Code Owners</a> of the
+ Clang static analyzer and the Clang frontend, respectively.</li>
+
+<li>LLVM now has an <a href="http://blog.llvm.org">official Blog</a> at
+ <a href="http://blog.llvm.org">http://blog.llvm.org</a>. This is a great way
+ to learn about new LLVM-related features as they are implemented. Several
+ features in this release are already explained on the blog.</li>
+<li>The LLVM web pages are now checked into the SVN server, in the "www",
+ "www-pubs" and "www-releases" SVN modules. Previously they were hidden in a
+ largely inaccessible old CVS server.</li>
+
+<li><a href="http://llvm.org">llvm.org</a> is now hosted on a new (and much
+ faster) server. It is still graciously hosted at the University of Illinois
+ of Urbana Champaign.</li>
</ul>
-
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="codegen">Code Generator Improvements</a>
+<a name="majorfeatures">Major New Features</a>
</div>
<div class="doc_text">
-<p>We 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>
+<p>LLVM 2.7 includes several major new capabilities:</p>
<ul>
-<li>MemOperand in the code generator.</li>
+<li>2.7 includes initial support for the <a
+ href="http://en.wikipedia.org/wiki/MicroBlaze">MicroBlaze</a> target.
+ MicroBlaze is a soft processor core designed for Xilinx FPGAs.</li>
+
+<li>2.7 includes a new LLVM IR "extensible metadata" feature. This feature
+ supports many different use cases, including allowing front-end authors to
+ encode source level information into LLVM IR, which is consumed by later
+ language-specific passes. This is a great way to do high-level optimizations
+ like devirtualization, type-based alias analysis, etc. See the <a
+ href="http://blog.llvm.org/2010/04/extensible-metadata-in-llvm-ir.html">
+ Extensible Metadata Blog Post</a> for more information.</li>
+
+<li>2.7 encodes <a href="SourceLevelDebugging.html">debug information</a>
+in a completely new way, built on extensible metadata. The new implementation
+is much more memory efficient and paves the way for improvements to optimized
+code debugging experience.</li>
+
+<li>2.7 now directly supports taking the address of a label and doing an
+ indirect branch through a pointer. This is particularly useful for
+ interpreter loops, and is used to implement the GCC "address of label"
+ extension. For more information, see the <a
+href="http://blog.llvm.org/2010/01/address-of-label-and-indirect-branches.html">
+Address of Label and Indirect Branches in LLVM IR Blog Post</a>.
+
+<li>2.7 is the first release to start supporting APIs for assembling and
+ disassembling target machine code. These APIs are useful for a variety of
+ low level clients, and are surfaced in the new "enhanced disassembly" API.
+ For more information see the <a
+ href="http://blog.llvm.org/2010/01/x86-disassembler.html">The X86
+ Disassembler Blog Post</a> for more information.</li>
+
+<li>2.7 includes major parts of the work required by the new MC Project,
+ see the <a href="#mc">MC update above</a> for more information.</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>LLVM IR now supports a 16-bit "half float" data type through <a
+ href="LangRef.html#int_fp16">two new intrinsics</a> and APFloat support.</li>
+<li>LLVM IR supports two new <a href="LangRef.html#fnattrs">function
+ attributes</a>: inlinehint and alignstack(n). The former is a hint to the
+ optimizer that a function was declared 'inline' and thus the inliner should
+ weight it higher when considering inlining it. The later
+ indicates to the code generator that the function diverges from the platform
+ ABI on stack alignment.</li>
+<li>The new <a href="LangRef.html#int_objectsize">llvm.objectsize</a> intrinsic
+ allows the optimizer to infer the sizes of memory objects in some cases.
+ This intrinsic is used to implement the GCC <tt>__builtin_object_size</tt>
+ extension.</li>
+<li>LLVM IR now supports marking load and store instructions with <a
+ href="LangRef.html#i_load">"non-temporal" hints</a> (building on the new
+ metadata feature). This hint encourages the code
+ generator to generate non-temporal accesses when possible, which are useful
+ for code that is carefully managing cache behavior. Currently, only the
+ X86 backend provides target support for this feature.</li>
+
+<li>LLVM 2.7 has pre-alpha support for <a
+ href="LangRef.html#t_union">unions in LLVM IR</a>.
+ Unfortunately, this support is not really usable in 2.7, so if you're
+ interested in pushing it forward, please help contribute to LLVM mainline.</li>
+
</ul>
</div>
<div class="doc_text">
-<p>In addition to a huge array of bug fixes and minor performance tweaks, the
-LLVM 2.3 optimizers support a few major enhancements:</p>
+<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 inliner now merges arrays stack objects in different callees when
+ inlining multiple call sites into one function. This reduces the stack size
+ of the resultant function.</li>
+<li>The -basicaa alias analysis pass (which is the default) has been improved to
+ be less dependent on "type safe" pointers. It can now look through bitcasts
+ and other constructs more aggressively, allowing better load/store
+ optimization.</li>
+<li>The load elimination optimization in the GVN Pass [<a
+href="http://blog.llvm.org/2009/12/introduction-to-load-elimination-in-gvn.html">intro
+ blog post</a>] has been substantially improved to be more aggressive about
+ partial redundancy elimination and do more aggressive phi translation. Please
+ see the <a
+ href="http://blog.llvm.org/2009/12/advanced-topics-in-redundant-load.html">
+ Advanced Topics in Redundant Load Elimination with a Focus on PHI Translation
+ Blog Post</a> for more details.</li>
+<li>The module <a href="LangRef.html#datalayout">target data string</a> now
+ includes a notion of 'native' integer data types for the target. This
+ helps mid-level optimizations avoid promoting complex sequences of
+ operations to data types that are not natively supported (e.g. converting
+ i32 operations to i64 on 32-bit chips).</li>
+<li>The mid-level optimizer is now conservative when operating on a module with
+ no target data. Previously, it would default to SparcV9 settings, which is
+ not what most people expected.</li>
+<li>Jump threading is now much more aggressive at simplifying correlated
+ conditionals and threading blocks with otherwise complex logic. It has
+ subsumed the old "Conditional Propagation" pass, and -condprop has been
+ removed from LLVM 2.7.</li>
+<li>The -instcombine pass has been refactored from being one huge file to being
+ a library of its own. Internally, it uses a customized IRBuilder to clean
+ it up and simplify it.</li>
+
+<li>The optimal edge profiling pass is reliable and much more complete than in
+ 2.6. It can be used with the llvm-prof tool but isn't wired up to the
+ llvm-gcc and clang command line options yet.</li>
+
+<li>A new experimental alias analysis implementation, -scev-aa, has been added.
+ It uses LLVM's Scalar Evolution implementation to do symbolic analysis of
+ pointer offset expressions to disambiguate pointers. It can catch a few
+ cases that basicaa cannot, particularly in complex loop nests.</li>
+
+<li>The default pass ordering has been tweaked for improved optimization
+ effectiveness.</li>
+
+</ul>
+
+</div>
+
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="executionengine">Interpreter and JIT Improvements</a>
+</div>
+
+<div class="doc_text">
<ul>
+<li>The JIT now supports generating debug information and is compatible with
+the new GDB 7.0 (and later) interfaces for registering dynamically generated
+debug info.</li>
+
+<li>The JIT now <a href="http://llvm.org/PR5184">defaults
+to compiling eagerly</a> to avoid a race condition in the lazy JIT.
+Clients that still want the lazy JIT can switch it on by calling
+<tt>ExecutionEngine::DisableLazyCompilation(false)</tt>.</li>
-<li>Index set splitting on by default.</li>
+<li>It is now possible to create more than one JIT instance in the same process.
+These JITs can generate machine code in parallel,
+although <a href="http://llvm.org/docs/ProgrammersManual.html#jitthreading">you
+still have to obey the other threading restrictions</a>.</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 'llc -asm-verbose' option (which is now the default) has been enhanced
+ to emit many useful comments to .s files indicating information about spill
+ slots and loop nest structure. This should make it much easier to read and
+ understand assembly files. This is wired up in llvm-gcc and clang to
+ the <tt>-fverbose-asm</tt> option.</li>
+
+<li>New LSR with "full strength reduction" mode, which can reduce address
+ register pressure in loops where address generation is important.</li>
+
+<li>A new codegen level Common Subexpression Elimination pass (MachineCSE)
+ is available and enabled by default. It catches redundancies exposed by
+ lowering.</li>
+<li>A new pre-register-allocation tail duplication pass is available and enabled
+ by default, it can substantially improve branch prediction quality in some
+ cases.</li>
+<li>A new sign and zero extension optimization pass (OptimizeExtsPass)
+ is available and enabled by default. This pass can takes advantage
+ architecture features like x86-64 implicit zero extension behavior and
+ sub-registers.</li>
+<li>The code generator now supports a mode where it attempts to preserve the
+ order of instructions in the input code. This is important for source that
+ is hand scheduled and extremely sensitive to scheduling. It is compatible
+ with the GCC <tt>-fno-schedule-insns</tt> option.</li>
+<li>The target-independent code generator now supports generating code with
+ arbitrary numbers of result values. Returning more values than was
+ previously supported is handled by returning through a hidden pointer. In
+ 2.7, only the X86 and XCore targets have adopted support for this
+ though.</li>
+<li>The code generator now supports generating code that follows the
+ <a href="LangRef.html#callingconv">Glasgow Haskell Compiler Calling
+ Convention</a> and ABI.</li>
+<li>The "<a href="CodeGenerator.html#selectiondag_select">DAG instruction
+ selection</a>" phase of the code generator has been largely rewritten for
+ 2.7. Previously, tblgen spit out tons of C++ code which was compiled and
+ linked into the target to do the pattern matching, now it emits a much
+ smaller table which is read by the target-independent code. The primary
+ advantages of this approach is that the size and compile time of various
+ targets is much improved. The X86 code generator shrunk by 1.5MB of code,
+ for example.</li>
+<li>Almost the entire code generator has switched to emitting code through the
+ MC interfaces instead of printing textually to the .s file. This led to a
+ number of cleanups and speedups. In 2.7, debug an exception handling
+ information does not go through MC yet.</li>
+</ul>
+</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="targetspecific">Target Specific Improvements</a>
+<a name="x86">X86-32 and X86-64 Target Improvements</a>
</div>
<div class="doc_text">
-<p>New target-specific features include:
+<p>New features of the X86 target include:
</p>
<ul>
+<li>The X86 backend now optimizes tails calls much more aggressively for
+ functions that use the standard C calling convention.</li>
+<li>The X86 backend now models scalar SSE registers as subregs of the SSE vector
+ registers, making the code generator more aggressive in cases where scalars
+ and vector types are mixed.</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>The ARM backend now generates instructions in unified assembly syntax.</li>
+
+<li>llvm-gcc now has complete support for the ARM v7 NEON instruction set. This
+ support differs slightly from the GCC implementation. Please see the
+ <a
+href="http://blog.llvm.org/2010/04/arm-advanced-simd-neon-intrinsics-and.html">
+ ARM Advanced SIMD (NEON) Intrinsics and Types in LLVM Blog Post</a> for
+ helpful information if migrating code from GCC to LLVM-GCC.</li>
+<li>The ARM and Thumb code generators now use register scavenging for stack
+ object address materialization. This allows the use of R3 as a general
+ purpose register in Thumb1 code, as it was previous reserved for use in
+ stack address materialization. Secondly, sequential uses of the same
+ value will now re-use the materialized constant.</li>
+
+<li>The ARM backend now has good support for ARMv4 targets and has been tested
+ on StrongARM hardware. Previously, LLVM only supported ARMv4T and
+ newer chips.</li>
+
+<li>Atomic builtins are now supported for ARMv6 and ARMv7 (__sync_synchronize,
+ __sync_fetch_and_add, etc.).</li>
+
+</ul>
+
+
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="otherimprovements">Other Improvements</a>
+<a name="newapis">New Useful APIs</a>
</div>
<div class="doc_text">
-<p>New features include:
+
+<p>This release includes a number of new APIs that are used internally, which
+ may also be useful for external clients.
</p>
<ul>
+<li>The optimizer uses the new CodeMetrics class to measure the size of code.
+ Various passes (like the inliner, loop unswitcher, etc) all use this to make
+ more accurate estimates of the code size impact of various
+ optimizations.</li>
+<li>A new <a href="http://llvm.org/doxygen/InstructionSimplify_8h-source.html">
+ llvm/Analysis/InstructionSimplify.h</a> interface is available for doing
+ symbolic simplification of instructions (e.g. <tt>a+0</tt> -> <tt>a</tt>)
+ without requiring the instruction to exist. This centralizes a lot of
+ ad-hoc symbolic manipulation code scattered in various passes.</li>
+<li>The optimizer now uses a new <a
+ href="http://llvm.org/doxygen/SSAUpdater_8h-source.html">SSAUpdater</a>
+ class which efficiently supports
+ doing unstructured SSA update operations. This centralized a bunch of code
+ scattered throughout various passes (e.g. jump threading, lcssa,
+ loop rotate, etc) for doing this sort of thing. The code generator has a
+ similar <a href="http://llvm.org/doxygen/MachineSSAUpdater_8h-source.html">
+ MachineSSAUpdater</a> class.</li>
+<li>The <a href="http://llvm.org/doxygen/Regex_8h-source.html">
+ llvm/Support/Regex.h</a> header exposes a platform independent regular
+ expression API. Building on this, the <a
+ href="TestingGuide.html#FileCheck">FileCheck</a> utility now supports
+ regular exressions.</li>
+<li>raw_ostream now supports a circular "debug stream" accessed with "dbgs()".
+ By default, this stream works the same way as "errs()", but if you pass
+ <tt>-debug-buffer-size=1000</tt> to opt, the debug stream is capped to a
+ fixed sized circular buffer and the output is printed at the end of the
+ program's execution. This is helpful if you have a long lived compiler
+ process and you're interested in seeing snapshots in time.</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>You can now build LLVM as a big dynamic library (e.g. "libllvm2.7.so"). To
+ get this, configure LLVM with the --enable-shared option.</li>
+
+<li>LLVM command line tools now overwrite their output by default. Previously,
+ they would only do this with -f. This makes them more convenient to use, and
+ behave more like standard unix tools.</li>
+
+<li>The opt and llc tools now autodetect whether their input is a .ll or .bc
+ file, and automatically do the right thing. This means you don't need to
+ explicitly use the llvm-as tool for most things.</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 2.6, this section lists some "gotchas" that you may run into upgrading
+from the previous release.</p>
+
+<ul>
+
+<li>
+The Andersen's alias analysis ("anders-aa") pass, the Predicate Simplifier
+("predsimplify") pass, the LoopVR pass, the GVNPRE pass, and the random sampling
+profiling ("rsprofiling") passes have all been removed. They were not being
+actively maintained and had substantial problems. If you are interested in
+these components, you are welcome to ressurect them from SVN, fix the
+correctness problems, and resubmit them to mainline.</li>
+
+<li>LLVM now defaults to building most libraries with RTTI turned off, providing
+a code size reduction. Packagers who are interested in building LLVM to support
+plugins that require RTTI information should build with "make REQUIRE_RTTI=1"
+and should read the new <a href="Packaging.html">Advice on Packaging LLVM</a>
+document.</li>
+
+<li>The LLVM interpreter now defaults to <em>not</em> using <tt>libffi</tt> even
+if you have it installed. This makes it more likely that an LLVM built on one
+system will work when copied to a similar system. To use <tt>libffi</tt>,
+configure with <tt>--enable-libffi</tt>.</li>
+
+<li>Debug information uses a completely different representation, an LLVM 2.6
+.bc file should work with LLVM 2.7, but debug info won't come forward.</li>
+
+<li>The LLVM 2.6 (and earlier) "malloc" and "free" instructions got removed,
+ along with LowerAllocations pass. Now you should just use a call to the
+ malloc and free functions in libc. These calls are optimized as well as
+ the old instructions were.</li>
+</ul>
+
+<p>In addition, many APIs have changed in this release. Some of the major LLVM
+API changes are:</p>
+
+<ul>
+
+<li>The <tt>add</tt>, <tt>sub</tt>, and <tt>mul</tt> instructions no longer
+support floating-point operands. The <tt>fadd</tt>, <tt>fsub</tt>, and
+<tt>fmul</tt> instructions should be used for this purpose instead.</li>
+
+</ul>
+
</div>
+
+
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="portability">Portability and Supported Platforms</a>
<p>LLVM is known to work on the following platforms:</p>
<ul>
-<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
- (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 (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 10.4 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 8.</li>
+<li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</li>
<li>Alpha-based machines running Debian GNU/Linux.</li>
-<li>Itanium-based machines running Linux and HP-UX.</li>
</ul>
-<p>The core LLVM infrastructure uses
-<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
+<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 class="doc_text">
-<p>This section contains all known problems with the LLVM system, listed by
-component. As new problems are discovered, they will be added to these
-sections. If you run into a problem, please check the <a
+<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>LLVM will not correctly compile on Solaris and/or OpenSolaris
+using the stock GCC 3.x.x series 'out the box',
+See: <a href="GettingStarted.html#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>
<!-- ======================================================================= -->
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
<ul>
-<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
-<li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
- value for this option.</li>
-<li>The llvmc tool is not supported.</li>
+<li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430, SystemZ and MicroBlaze
+ backends are experimental.</li>
+<li><tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
+ supported value for this option. The MachO writer is experimental, and
+ works much better in mainline SVN.</li>
</ul>
</div>
<div class="doc_text">
<ul>
-<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
- assembly that uses the X86 floating point stack</a>.</li>
-<li>The X86 backend occasionally has <a href="http://llvm.org/PR1649">alignment
- problems</a> on operating systems that don't require 16-byte stack alignment
- (including most non-darwin OS's like linux).</li>
-<li>The X86 backend generates inefficient floating point code when configured to
- generate code for systems that don't have SSE2.</li>
+ <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 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, front-ends support variadic
+ argument constructs on X86-64 by lowering them manually.</li>
</ul>
</div>
<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>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
</li>
-<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
-programs compiled with LLVM. Please use more recent versions of QEMU.</li>
</ul>
</div>
<div class="doc_text">
<ul>
-<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
+<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 class="doc_subsection">
- <a name="alpha-be">Known problems with the Alpha back-end</a>
+ <a name="mips-be">Known problems with the MIPS 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>
-
+<li>64-bit MIPS targets are not supported yet.</li>
</ul>
+
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="ia64-be">Known problems with the IA64 back-end</a>
+ <a name="alpha-be">Known problems with the Alpha back-end</a>
</div>
<div class="doc_text">
<ul>
-<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
-made where the argument is not 16-byte aligned, as required on IA64. (Strictly
-speaking this is not a bug in the IA64 back-end; it will also be encountered
-when building C++ programs using the C back-end.)</li>
-
-<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
-ABI compliant layout of v-tables</a>. In particular, it just stores function
-pointers instead of function descriptors in the vtable. This bug prevents
-mixing C++ code compiled with LLVM with C++ objects compiled by other C++
-compilers.</li>
-
-<li>There are a few ABI violations which will lead to problems when mixing LLVM
-output with code built with other compilers, particularly for floating-point
-programs.</li>
-
-<li>Defining vararg functions is not supported (but calling them is ok).</li>
+<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
+appropriate nops inserted to ensure restartability.</li>
-<li>The Itanium backend has bitrotted somewhat.</li>
</ul>
-
</div>
<!-- ======================================================================= -->
<div class="doc_text">
<ul>
-<li><a href="http://llvm.org/PR802">The C backend does not support inline
- assembly code</a>.</li>
-<li><a href="http://llvm.org/PR1126">The C backend does not support vectors
- yet</a>.</li>
+<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 LLC or native compilers.</li>
+ 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 C front-end</a>
-</div>
-
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">Bugs</div>
-
-<div class="doc_text">
-
-<p>llvm-gcc 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>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">
- Notes
+ <a name="c-fe">Known problems with the llvm-gcc C and C++ front-end</a>
</div>
<div class="doc_text">
-<ul>
-
-<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
- 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>
-
-<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 X86 targets)
- or non-local gotos.</li>
-
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
-
- Declaring that functions have no side effects or that they can never
- return.<br>
-
- <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
- <tt>const</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
- <tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
- <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noinline</tt>,
- <tt>noreturn</tt>, <tt>nothrow</tt>, <tt>pure</tt>, <tt>regparm</tt>
- <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>malloc</tt>,
- <tt>no_instrument_function</tt></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>
+<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>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="c++-fe">Known problems with the C++ front-end</a>
+ <a name="fortran-fe">Known problems with the llvm-gcc Fortran 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 X86 and PowerPC targets.
-It works well for x86-64 darwin but not x86-64 linux.</li>
+<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 Ada front-end</a>
+ <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.
+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>
+<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>.
-Workaround: configure with --disable-bootstrap.</li>
-<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
-fail (c380004 also fails with gcc-4.2 mainline).</li>
-<li>Many gcc specific Ada tests continue to crash the compiler.</li>
-<li>The -E binder option (exception backtraces)
+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 -E.</li>
+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 lli 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 argv and envp rather than
-integers.</li>
-<li>The -fstack-check option <a href="http://llvm.org/PR2008">is ignored</a>.</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="fortran-fe">Known problems with the Fortran front-end</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
-<li>The llvm-gcc 4.2 gfortran front-end supports a broad range of Fortran code, but does
-<a href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
-</ul>
-</div>
-
-
-
<!-- *********************************************************************** -->
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