<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 2.4 Release Notes</title>
+ <title>LLVM 2.8 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.4 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="#subproj">Sub-project Status Update</a></li>
- <li><a href="#whatsnew">What's New in LLVM?</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 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">
<a name="intro">Introduction</a>
<div class="doc_text">
<p>This document contains the release notes for the LLVM Compiler
-Infrastructure, release 2.4. Here we describe the status of LLVM, including
+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
+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
main LLVM web page, this document applies to the <i>next</i> release, not the
<a href="http://llvm.org/releases/">releases page</a>.</p>
</div>
-
-<!-- Unfinished features in 2.4:
- Machine LICM
- Machine Sinking
- LegalizeDAGTypes
- llc -enable-value-prop, propagation of value info (sign/zero ext info) from
- one MBB to another
+
+
+<!--
+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:
- mention dev mtg
- Xcode 3.1 and 3.1.1.
- -->
+ Logo web page.
+ Many new papers added to /pubs/
+ -->
<!-- *********************************************************************** -->
<div class="doc_section">
<div class="doc_text">
<p>
-The LLVM 2.4 distribution currently consists of code from the core LLVM
-repository (which roughly includes the LLVM optimizers, code generators and
-supporting tools) and the llvm-gcc repository. In addition to this code, the
-LLVM Project includes other sub-projects that are in development. The two which
-are the most actively developed are the <a href="#clang">Clang Project</a> and
-the <a href="#vmkit">vmkit Project</a>.
+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>
<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 LLVM optimizer
-and code generator. Clang is continuing to make major strides forward in all
-areas. Its C and Objective-C parsing support is very solid, and the code
-generation support is far enough along to build many C applications. While not
-yet production quality, it is progressing very nicely. In addition, C++
-front-end work has started to make significant progress.</p>
+<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>
-<p>Codegen progress/state [DANIEL]</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_text">
-<p>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 a growing set
-of checks to find bugs that occur on a specific path within a program. Examples
-of bugs the tool finds include logic errors such as null dereferences,
-violations of various API rules, dead code, and potential memory leaks in
-Objective-C programs. Since its inception, public feedback on the tool has been
-extremely positive, and conservative estimates put the number of real bugs it
-has found in industrial-quality software on the order of thousands.</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="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>
+
+<ul>
+
+<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="compiler-rt">compiler-rt: Compiler Runtime Library</a>
+</div>
-<p>The tool also provides a simple web GUI to inspect potential bugs found by
-the tool. While still early in development, the GUI illustrates some of the key
-features of Clang: accurate source location information, which is used by the
-GUI to highlight specific code expressions that relate to a bug (including those
-that span multiple lines) and built-in knowledge of macros, which is used to
-perform inline expansion of macros within the GUI itself.</p>
+<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>The set of checks performed by the static analyzer is gradually expanding,
-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>
+<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>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="vmkit">vmkit: JVM/CLI Virtual Machine Implementation</a>
+<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</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 Machines (Microsoft .NET is an
-implementation of the CLI) using the Just-In-Time compiler of LLVM.</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>[NICOLAS]</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="whatsnew">What's New in LLVM?</a>
+ <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="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 0.43 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>
<!-- *********************************************************************** -->
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>
+<a name="orgchanges">LLVM Community Changes</a>
</div>
<div class="doc_text">
-<p>LLVM 2.4 includes several major new capabilities:</p>
+<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><p>The most visible end-user change in LLVM 2.4 is that it includes many
-optimizations and changes to make -O0 compile times much faster. You should see
-improvements on the order of 30% (or more) faster than LLVM 2.3. There are many
-pieces to this change, described in more detail below. The speedups and new
-components can also be used for JIT compilers that want fast compilation as
-well.</p></li>
-
-<li><p>The biggest change to the LLVM IR is that Multiple Return Values (which
-were introduced in LLVM 2.3) have been generalized to full support for "First
-Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using
-structs and arrays as values in a function. This capability is mostly useful
-for front-end authors, who prefer to treat things like complex numbers, simple
-tuples, dope vectors, etc as Value*'s instead of as a tuple of Value*'s or as
-memory values. Bitcode files from LLVM 2.3 will automatically migrate to the
-general representation.</p></li>
-
-<li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This
-is the LLVM target that only has support for 8 bit registers, and a number of
-other crazy constraints. While the port is still in early development stages,
-it shows some interesting things you can do with LLVM.</p></li>
+<li>LLVM has a new <a href="http://llvm.org/Logo.html">official logo</a>!</li>
-</ul>
+<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>
-</div>
+<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="llvm-gcc">llvm-gcc 4.2 Improvements</a>
+<a name="majorfeatures">Major New Features</a>
</div>
<div class="doc_text">
-<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
-front-ends and driver with the LLVM optimizer and code generator. It currently
-includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
+<p>LLVM 2.7 includes several major new capabilities:</p>
<ul>
-<li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM
-2.3 only supported those used by OpenMP, but 2.4 supports them all. While
-llvm-gcc supports all of these builtins, note that not all targets do. X86
-support them all in both 32-bit and 64-bit mode and PowerPC supports them all
-except for the 64-bit operations when in 32-bit mode.</li>
-
-<li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells
-the compiler that it is ok to use low-precision approximations of certain libm
-functions (like tan, log, etc). This allows you to get high performance if you
-only need (say) 14-bits of precision.</li>
-
-<li>llvm-gcc now supports a C language extension known as "<a
-href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks
-</a>". This feature is similar to nested functions and closures, but does not
-require stack trampolines (with most ABIs) and supports returning closures
-from functions that define them. Note that actually <em>using</em> Blocks
-requires a small runtime that is not included with llvm-gcc.</li>
-
-<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support
-transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and
-later) this allows the use of LTO with other optimization levels like -Os.
-Previously, LTO could only be used with -O4, which implied optimizations in
--O3 that can increase code size.</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 Core Improvements</a>
+<a name="coreimprovements">LLVM IR and Core Improvements</a>
</div>
<div class="doc_text">
-<p>New features include:
-</p>
+<p>LLVM IR has several new features for better support of new targets and that
+expose new optimization opportunities:</p>
<ul>
-<li>A major change to the <tt>Use</tt> class landed, which shrank it by 25%. Since
-this is a pervasive part of the LLVM, it ended up reducing the memory use of
-LLVM IR in general by 15% for most programs.</li>
+<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>
-<li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more
-nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of
-"<tt>add i32 %A, 4 ; <i32>:3</tt>", which makes it much easier to read.
-</li>
-
-<li>LLVM 2.4 includes some changes for better vector support. First, the shift
-operations (<tt>shl</tt>, <tt>ashr</tt>, <tt>lshr</tt>) now all support vectors
-and do an element-by-element shift (shifts of the whole vector can be
-accomplished by bitcasting the vector to <1 x i128> for example). Second,
-there is initial support in development for vector comparisons with the
-<a href="LangRef.html#i_fcmp">fcmp</a>/<a href="LangRef.html#i_icmp">icmp</a>
-instructions. These instructions compare two vectors and return a vector of
-i1's for each result. Note that there is very little codegen support available
-for any of these IR features though.</li>
-
-<li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much
-easier for front-ends to create debug info descriptors, similar to the way that
-IRBuilder makes it easier to create LLVM IR.</li>
-
-<li>The <tt>IRBuilder</tt> class is now parametrized by a class responsible
-for constant folding. The default <tt>ConstantFolder</tt> class does target independent
-constant folding. The <tt>NoFolder</tt> class does no constant folding at all, which is
-useful when learning how LLVM works. The <tt>TargetFolder</tt> class folds the most,
-doing target dependent constant folding.</li>
-
-<li>LLVM now supports "function attributes", which allows us to separate return
-value attributes from function attributes. LLVM now supports attributes on a
-function itself, a return value, and its parameters. New supported function
-attributes include noinline/alwaysinline and the "opt-size" flag which says the
-function should be optimized for code size.</li>
-
-<li>LLVM IR now directly represents "common" linkage, instead of
- representing it as a form of weak linkage.</li>
-
</ul>
</div>
<div class="doc_text">
-<p>In addition to a huge array of bug fixes and minor performance tweaks, this
+<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 Global Value Numbering (GVN) pass now does local Partial Redundancy
-Elimination (PRE) to eliminate some partially redundant expressions in cases
-where doing so won't grow code size.</li>
+<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>
-<li>LLVM 2.4 includes a new loop deletion pass (which removes output-free
-provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE)
-pass that no longer uses control dependence information. These changes speed up
-the optimizer and also prevents it from deleting output-free infinite
-loops.</li>
-<li>The new AddReadAttrs pass works out which functions are read-only or
-read-none (these correspond to 'pure' and 'const' in C) and marks them
-with the appropriate attribute.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="executionengine">Interpreter and JIT Improvements</a>
+</div>
-<li>LLVM 2.4 now includes a new SparsePropagation framework, which makes it
-trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using
-this interface means that you just define objects to represent your lattice
-values and the transfer functions that operate on them. It handles the
-mechanics of worklist processing, liveness tracking, handling PHI nodes,
-etc.</li>
+<div class="doc_text">
-<li>The Loop Strength Reduction and induction variable optimization passes have
-several improvements to avoid inserting MAX expressions, to optimize simple
-floating point induction variables and to analyze trip counts of more
-loops.</li>
+<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>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were
-pulled out of the Instruction Combining pass and put into a new
-<tt>ValueTracking.h</tt> header, where they can be reused by other passes.</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>The tail duplication pass has been removed from the standard optimizer
-sequence used by llvm-gcc. This pass still exists, but the benefits it once
-provided are now achieved by other passes.</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 class="doc_subsection">
-<a name="codegen">Code Generator Improvements</a>
+<a name="codegen">Target Independent Code Generator Improvements</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>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 target-independent code generator supports (and the X86 backend
- currently implements) a new interface for "fast" instruction selection. This
- interface is optimized to produce code as quickly as possible, sacrificing
- code quality to do it. This is used by default at -O0 or when using
- "llc -fast" on X86. It is straight-forward to add support for
- other targets if faster -O0 compilation is desired.</li>
-
-<li>In addition to the new 'fast' instruction selection path, many existing
- pieces of the code generator have been optimized in significant ways.
- SelectionDAG's are now pool allocated and use better algorithms in many
- places, the ".s" file printers now use raw_ostream to emit text much faster,
- etc. The end result of these improvements is that the compiler also takes
- substantially less time to generate code that is just as good (and often
- better) than before.</li>
-
-<li>Each target has been split to separate the .s file printing logic from the
- rest of the target. This enables JIT compilers that don't link in the
- (somewhat large) code and data tables used for printing a .s file.</li>
-
-<li>The code generator now includes a "stack slot coloring" pass, which packs
- together individual spilled values into common stack slots. This reduces
- the size of stack frames with many spills, which tends to increase L1 cache
- effectiveness.</li>
+<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>
-<li>Various pieces of the register allocator (e.g. the coalescer and two-address
- operation elimination pass) now know how to rematerialize trivial operations
- to avoid copies and include several other optimizations.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="x86">X86-32 and X86-64 Target Improvements</a>
+</div>
-<li>The <a href="CodeGenerator.html#selectiondag_process">graphs</a> produced by
- the <tt>llc -view-*-dags</tt> options are now significantly prettier and
- easier to read.</li>
+<div class="doc_text">
+<p>New features of the X86 target include:
+</p>
-<li>LLVM 2.4 includes a new register allocator based on Partitioned Boolean
- Quadratic Programming (PBQP). This register allocator is still in
- development, but is very simple and clean.</li>
+<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="targetspecific">Target Specific Improvements</a>
+<a name="ARM">ARM Target Improvements</a>
</div>
<div class="doc_text">
-<p>New target-specific features include:
+<p>New features of the ARM target include:
</p>
<ul>
-<li>Exception handling is supported by default on Linux/x86-64.</li>
-<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
-<li>@llvm.frameaddress now supports getting the frame address of stack frames
- > 0 on x86/x86-64.</li>
-<li>MIPS floating point support? [BRUNO]</li>
-<li>The PowerPC backend now supports trampolines.</li>
+
+<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>
<!--=========================================================================-->
<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><tt>llvmc2</tt> (the generic compiler driver) gained plugin
- support. It is now easier to experiment with <tt>llvmc2</tt> and
- build your own tools based on it.</li>
-
-<li>LLVM 2.4 includes a number of new generic algorithms and data structures,
- include a scoped hash table, 'immutable' data structures, and a
- <tt>raw_ostream</tt> class. The <tt>raw_ostream</tt> class and
- <tt>format</tt> allow for efficient file output, and various pieces of LLVM
- have switched over to use it. The eventual goal is to eliminate
- std::ostream in favor of it.</li>
-
-<li>Recycler + pool allocation stuff? [DAN]</li>
+<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 class="doc_text">
<p>If you're already an LLVM user or developer with out-of-tree changes based
-on LLVM 2.3, this section lists some "gotchas" that you may run into upgrading
+on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading
from the previous release.</p>
<ul>
-<li>The LLVM IR generated by llvm-gcc no longer names all instructions. This
- makes it run faster, but may be more confusing to some people. If you
- prefer to have names, the '<tt>opt -instnamer</tt>' pass will add names to
- all instructions.</li>
-
-<li>The LoadVN and GCSE passes have been removed from the tree. They are
- obsolete and have been replaced with the GVN and MemoryDependence passes.
- </li>
+<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>Attributes changes [DEVANG] </li>
-
-<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and
-<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be
-converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via
-"llvm/Analysis/ValueTracking.h".</li>
-
-<li>The APIs to create various instructions have changed from lower case
- "create" methods to upper case "Create" methods (e.g.
- <tt>BinaryOperator::create</tt>). LLVM 2.4 includes both cases, but the
- lower case ones are removed in mainline, please migrate.</li>
-
-<li>Various header files like "llvm/ADT/iterator" were given a .h suffix.
- Change your code to #include "llvm/ADT/iterator.h" instead.</li>
+<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>
-<li>In the code generator, many MachineOperand predicates were renamed to be
- shorter (e.g. <tt>isFrameIndex()</tt> -> <tt>isFI()</tt>),
- <tt>SDOperand</tt> was renamed to <tt>SDValue</tt> (and the "<tt>Val</tt>"
- member was changed to be the <tt>getNode()</tt> accessor), and the
- <tt>MVT::ValueType</tt> enum has been replaced with an "<tt>MVT</tt>"
- struct.</li>
</ul>
</div>
<p>LLVM is known to work on the following platforms:</p>
<ul>
-<li>Intel and AMD machines (IA32) 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 10.</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 (IA64) machines running Linux and HP-UX.</li>
</ul>
<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
<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 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>
<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 mingw64 runtime
- currently due
- to <a href="http://llvm.org/PR2255">several</a>
- <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
- 'u' inline assembly constraint and X87 floating point inline assembly.</li>
+ 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, the llvm-gcc front-end supports variadic
+ <tt>va_arg</tt>. Currently, front-ends support variadic
argument constructs on X86-64 by lowering them manually.</li>
</ul>
<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>The Itanium backend is highly experimental, and has a number of known
- issues. We are looking for a maintainer for the Itanium backend. If you
- are interested, please contact the llvmdev mailing list.</li>
-</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>
<!-- ======================================================================= -->
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 llvm-gcc C front-end</a>
+ <a name="c-fe">Known problems with the llvm-gcc C and C++ front-end</a>
</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>
-
<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>
+ <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 works well on the X86 and PowerPC targets. Currently
- only linux and darwin targets are supported (both 32 and 64 bit).</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 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>
+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>
+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).</li>
-<li>Some gcc specific Ada tests continue to crash the compiler.</li>
-<li>The -E binder option (exception backtraces)
+(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
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