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a33612c1f2
The register allocators don't currently support adding reserved registers while they are running. Extend the MRI API to keep track of the set of reserved registers when register allocation started. Target hooks like hasFP() and needsStackRealignment() can look at this set to avoid reserving more registers during register allocation. llvm-svn: 147577
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link rel="stylesheet" href="llvm.css" type="text/css">
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<title>LLVM 3.1 Release Notes</title>
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<body>
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<h1>LLVM 3.1 Release Notes</h1>
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<img style="float:right" src="http://llvm.org/img/DragonSmall.png"
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width="136" height="136" alt="LLVM Dragon Logo">
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</div>
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<ol>
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<li><a href="#intro">Introduction</a></li>
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<li><a href="#subproj">Sub-project Status Update</a></li>
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<li><a href="#externalproj">External Projects Using LLVM 3.1</a></li>
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<li><a href="#whatsnew">What's New in LLVM?</a></li>
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<li><a href="GettingStarted.html">Installation Instructions</a></li>
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<li><a href="#knownproblems">Known Problems</a></li>
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<li><a href="#additionalinfo">Additional Information</a></li>
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</ol>
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<div class="doc_author">
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<p>Written by the <a href="http://llvm.org/">LLVM Team</a></p>
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</div>
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<h1 style="color:red">These are in-progress notes for the upcoming LLVM 3.1
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release.<br>
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You may prefer the
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<a href="http://llvm.org/releases/3.0/docs/ReleaseNotes.html">LLVM 3.0
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Release Notes</a>.</h1>
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<!-- *********************************************************************** -->
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<h2>
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<a name="intro">Introduction</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>This document contains the release notes for the LLVM Compiler
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Infrastructure, release 3.1. Here we describe the status of LLVM, including
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major improvements from the previous release, improvements in various
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subprojects of LLVM, and some of the current users of the code.
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All LLVM releases may be downloaded from
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the <a href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
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<p>For more information about LLVM, including information about the latest
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release, please check out the <a href="http://llvm.org/">main LLVM web
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site</a>. If you have questions or comments,
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the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM
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Developer's Mailing List</a> is a good place to send them.</p>
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<p>Note that if you are reading this file from a Subversion checkout or the main
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LLVM web page, this document applies to the <i>next</i> release, not the
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current one. To see the release notes for a specific release, please see the
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<a href="http://llvm.org/releases/">releases page</a>.</p>
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="subproj">Sub-project Status Update</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>The LLVM 3.1 distribution currently consists of code from the core LLVM
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repository (which roughly includes the LLVM optimizers, code generators and
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supporting tools), and the Clang repository. In
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addition to this code, the LLVM Project includes other sub-projects that are
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in development. Here we include updates on these subprojects.</p>
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<!--=========================================================================-->
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<h3>
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<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
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</h3>
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<div>
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<p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
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C++, and Objective-C languages. Clang aims to provide a better user
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experience through expressive diagnostics, a high level of conformance to
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language standards, fast compilation, and low memory use. Like LLVM, Clang
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provides a modular, library-based architecture that makes it suitable for
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creating or integrating with other development tools. Clang is considered a
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production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
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(32- and 64-bit), and for Darwin/ARM targets.</p>
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<p>In the LLVM 3.1 time-frame, the Clang team has made many improvements:</p>
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<ul>
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<li>...</li>
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</ul>
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<p>For more details about the changes to Clang since the 2.9 release, see the
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<a href="http://clang.llvm.org/docs/ReleaseNotes.html">Clang release notes</a>
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</p>
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<p>If Clang rejects your code but another compiler accepts it, please take a
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look at the <a href="http://clang.llvm.org/compatibility.html">language
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compatibility</a> guide to make sure this is not intentional or a known
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issue.</p>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
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</h3>
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<div>
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<p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
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<a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
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optimizers and code generators with LLVM's. It works with gcc-4.5 or gcc-4.6,
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targets the x86-32 and x86-64 processor families, and has been successfully
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used on the Darwin, FreeBSD, KFreeBSD, Linux and OpenBSD platforms. It fully
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supports Ada, C, C++ and Fortran. It has partial support for Go, Java, Obj-C
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and Obj-C++.</p>
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<p>The 3.1 release has the following notable changes:</p>
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<ul>
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<li>...</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
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</h3>
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<div>
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<p>The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
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is a simple library that provides an implementation of the low-level
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target-specific hooks required by code generation and other runtime
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components. For example, when compiling for a 32-bit target, converting a
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double to a 64-bit unsigned integer is compiled into a runtime call to the
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"__fixunsdfdi" function. The compiler-rt library provides highly optimized
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implementations of this and other low-level routines (some are 3x faster than
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the equivalent libgcc routines).</p>
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<p>....</p>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="lldb">LLDB: Low Level Debugger</a>
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</h3>
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<div>
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<p>LLDB is a ground-up implementation of a command line debugger, as well as a
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debugger API that can be used from other applications. LLDB makes use of the
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Clang parser to provide high-fidelity expression parsing (particularly for
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C++) and uses the LLVM JIT for target support.</p>
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<p>...</p>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="libc++">libc++: C++ Standard Library</a>
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</h3>
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<div>
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<p>Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
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licensed</a> under the MIT and UIUC license, allowing it to be used more
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permissively.</p>
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<p>...</p>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="vmkit">VMKit</a>
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</h3>
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<div>
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<p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an
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implementation of a Java Virtual Machine (Java VM or JVM) that uses LLVM for
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static and just-in-time compilation.
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<p>In the LLVM 3.1 time-frame, VMKit has had significant improvements on both
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runtime and startup performance:</p>
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<ul>
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<li>...</li>
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</ul>
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</div>
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="externalproj">External Open Source Projects Using LLVM 3.1</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>An exciting aspect of LLVM is that it is used as an enabling technology for
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a lot of other language and tools projects. This section lists some of the
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projects that have already been updated to work with LLVM 3.1.</p>
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|
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... to be filled in right before the release ...
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="whatsnew">What's New in LLVM 3.1?</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>This release includes a huge number of bug fixes, performance tweaks and
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minor improvements. Some of the major improvements and new features are
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listed in this section.</p>
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<!--=========================================================================-->
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<h3>
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<a name="majorfeatures">Major New Features</a>
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</h3>
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<div>
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<!-- Features that need text if they're finished for 3.1:
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ARM EHABI
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combiner-aa?
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strong phi elim
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loop dependence analysis
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CorrelatedValuePropagation
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lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
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Integrated assembler on by default for arm/thumb?
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-->
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<!-- Near dead:
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Analysis/RegionInfo.h + Dom Frontiers
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SparseBitVector: used in LiveVar.
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llvm/lib/Archive - replace with lib object?
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-->
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<p>LLVM 3.1 includes several major changes and big features:</p>
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<ul>
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<li><a href="../tools/clang/docs/AddressSanitizer.html">AddressSanitizer</a>,
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a fast memory error detector.</li>
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<li><a href="CodeGenerator.html#machineinstrbundle">MachineInstr Bundles</a>,
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Support to model instruction bundling / packing.</li>
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<li>....</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="coreimprovements">LLVM IR and Core Improvements</a>
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</h3>
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<div>
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<p>LLVM IR has several new features for better support of new targets and that
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expose new optimization opportunities:</p>
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<ul>
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<li>IR support for half float</li>
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<li>IR support for vectors of pointers, including vector GEPs.</li>
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<li>....</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="optimizer">Optimizer Improvements</a>
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</h3>
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<div>
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<p>In addition to many minor performance tweaks and bug fixes, this
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release includes a few major enhancements and additions to the
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optimizers:</p>
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<ul>
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<li>....</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="mc">MC Level Improvements</a>
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</h3>
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<div>
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<p>The LLVM Machine Code (aka MC) subsystem was created to solve a number of
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problems in the realm of assembly, disassembly, object file format handling,
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and a number of other related areas that CPU instruction-set level tools work
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in. For more information, please see
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the <a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
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to the LLVM MC Project Blog Post</a>.</p>
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<ul>
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<li>....</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="codegen">Target Independent Code Generator Improvements</a>
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</h3>
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<div>
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<p>We have changed the way that the Type Legalizer legalizes vectors.
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The type legalizer now attempts to promote integer elements.
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This enabled the implementation of vector-select.
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Additionally, we see a performance boost on workloads which use vectors of chars and shorts, since they are now promoted
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to 32-bit types, which are better supported by the SIMD instruction set.
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Floating point types are still widened as before.</p>
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<p>We have put a significant amount of work into the code generator
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infrastructure, which allows us to implement more aggressive algorithms and
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make it run faster:</p>
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<ul>
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<li>TableGen can now synthesize register classes that are only needed to
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represent combinations of constraints from instructions and sub-registers.
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The synthetic register classes inherit most of their properties form their
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closest user-defined super-class.</li>
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<li><code>MachineRegisterInfo</code> now allows the reserved registers to be
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frozen when register allocation starts. Target hooks should use the
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<code>MRI->canReserveReg(FramePtr)</code> method to avoid accidentally
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disabling frame pointer elimination during register allocation.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="x86">X86-32 and X86-64 Target Improvements</a>
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</h3>
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<div>
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<p>New features and major changes in the X86 target include:</p>
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<ul>
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<li>Bug fixes and improved support for AVX1</li>
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<li>Support for AVX2 (still incomplete at this point)</li>
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<li>....</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="ARM">ARM Target Improvements</a>
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</h3>
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<div>
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<p>New features of the ARM target include:</p>
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<ul>
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<li>The constant island pass now supports basic block and constant pool entry
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alignments greater than 4 bytes.</li> </ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="MIPS">MIPS Target Improvements</a>
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</h3>
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<div>
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<p>This release has seen major new work on just about every aspect of the MIPS
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backend. Some of the major new features include:</p>
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<ul>
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<li>....</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="OtherTS">Other Target Specific Improvements</a>
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</h3>
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<div>
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<ul>
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<li>....</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="changes">Major Changes and Removed Features</a>
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</h3>
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<div>
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<p>If you're already an LLVM user or developer with out-of-tree changes based on
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LLVM 3.1, this section lists some "gotchas" that you may run into upgrading
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from the previous release.</p>
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<ul>
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<li>LLVM 3.1 removes support for reading LLVM 2.9 bitcode files. Going forward,
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we aim for all future versions of LLVM to read bitcode files and .ll files
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produced by LLVM 3.0 and later.</li>
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<li>....</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="api_changes">Internal API Changes</a>
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</h3>
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<div>
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<p>In addition, many APIs have changed in this release. Some of the major
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LLVM API changes are:</p>
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<ul>
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<li>....</li>
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</ul>
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</div>
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="knownproblems">Known Problems</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>LLVM is generally a production quality compiler, and is used by a broad range
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of applications and shipping in many products. That said, not every
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subsystem is as mature as the aggregate, particularly the more obscure
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targets. If you run into a problem, please check the <a
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href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
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there isn't already one or ask on the <a
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href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
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list</a>.</p>
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<p>Known problem areas include:</p>
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<ul>
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<li>The Alpha, Blackfin, CellSPU, MSP430, PTX, SystemZ and
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XCore backends are experimental, and the Alpha, Blackfin and SystemZ
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targets have already been removed from mainline.</li>
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<li>The integrated assembler, disassembler, and JIT is not supported by
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several targets. If an integrated assembler is not supported, then a
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system assembler is required. For more details, see the <a
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href="CodeGenerator.html#targetfeatures">Target Features Matrix</a>.
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</li>
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<li>The C backend has numerous problems and is not being actively maintained.
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Depending on it for anything serious is not advised.</li>
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</ul>
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|
</div>
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|
|
<!-- *********************************************************************** -->
|
|
<h2>
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|
<a name="additionalinfo">Additional Information</a>
|
|
</h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
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<p>A wide variety of additional information is available on
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the <a href="http://llvm.org/">LLVM web page</a>, in particular in
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the <a href="http://llvm.org/docs/">documentation</a> section. The web page
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|
also contains versions of the API documentation which is up-to-date with the
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Subversion version of the source code. You can access versions of these
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documents specific to this release by going into the "<tt>llvm/doc/</tt>"
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directory in the LLVM tree.</p>
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<p>If you have any questions or comments about LLVM, please feel free to contact
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us via the <a href="http://llvm.org/docs/#maillist"> mailing lists</a>.</p>
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|
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</div>
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<!-- *********************************************************************** -->
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<hr>
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<address>
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|
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
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src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
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src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
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<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
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Last modified: $Date$
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</address>
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</body>
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</html>
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