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HTML
849 lines
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HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link rel="stylesheet" href="llvm.css" type="text/css">
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<title>LLVM 2.3 Release Notes</title>
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</head>
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<body>
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<div class="doc_title">LLVM 2.3 Release Notes</div>
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<ol>
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<li><a href="#intro">Introduction</a></li>
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<li><a href="#changes">Major Changes and Sub-project Status</a></li>
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<li><a href="#whatsnew">What's New?</a></li>
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<li><a href="GettingStarted.html">Installation Instructions</a></li>
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<li><a href="#portability">Portability and Supported Platforms</a></li>
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<li><a href="#knownproblems">Known Problems</a>
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<li><a href="#additionalinfo">Additional Information</a></li>
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</ol>
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<div class="doc_author">
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<p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
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</div>
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<!-- Done through Week-of-Mon-20080324.txt -->
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="intro">Introduction</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This document contains the release notes for the LLVM compiler
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infrastructure, release 2.3. Here we describe the status of LLVM, including
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major improvements from the previous release and any known problems. All LLVM
|
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releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
|
|
releases web site</a>.</p>
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|
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<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
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|
list</a> is a good place to send them.</p>
|
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|
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<p>Note that if you are reading this file from a Subversion checkout or the
|
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main LLVM web page, this document applies to the <i>next</i> release, not the
|
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current one. To see the release notes for a specific releases, please see the
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<a href="http://llvm.org/releases/">releases page</a>.</p>
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</div>
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<!-- *********************************************************************** -->
|
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<div class="doc_section">
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<a name="changes">Major Changes and Sub-project Status</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This is the fourteenth public release of the LLVM Compiler Infrastructure.
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It includes a large number of features and refinements from LLVM 2.2.</p>
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</div>
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<!-- Unfinished features in 2.3:
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Machine LICM
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Machine Sinking
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LegalizeDAGTypes
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-->
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<!--=========================================================================-->
|
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<div class="doc_subsection">
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<a name="changes">Major Changes in LLVM 2.3</a>
|
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</div>
|
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|
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<div class="doc_text">
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|
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<p>LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with
|
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llvm-gcc 4.2.</p>
|
|
|
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<p>LLVM 2.3 no longer includes the <tt>llvm-upgrade</tt> tool. It was useful
|
|
for upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a
|
|
previous LLVM release to do this. One nice impact of this is that the LLVM
|
|
regression test suite no longer depends on llvm-upgrade, which makes it run
|
|
faster.</p>
|
|
|
|
<p>The <tt>llvm2cpp</tt> tool has been folded into llc, use
|
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<tt>llc -march=cpp</tt> instead of <tt>llvm2cpp</tt>.</p>
|
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|
|
<p>LLVM API Changes:</p>
|
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|
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<ul>
|
|
<li>Several core LLVM IR classes have migrated to use the
|
|
'<tt>FOOCLASS::Create(...)</tt>' pattern instead of '<tt>new
|
|
FOOCLASS(...)</tt>' (e.g. where FOOCLASS=<tt>BasicBlock</tt>). We hope to
|
|
standardize on <tt>FOOCLASS::Create</tt> for all IR classes in the future,
|
|
but not all of them have been moved over yet.</li>
|
|
<li>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to
|
|
<a href="http://llvm.org/doxygen/classllvm_1_1IRBuilder.html">IRBuilder</a>.
|
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</li>
|
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<li>MRegisterInfo was renamed to
|
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<a href="http://llvm.org/doxygen/classllvm_1_1TargetRegisterInfo.html">
|
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TargetRegisterInfo</a>.</li>
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<li>The MappedFile class is gone, please use
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<a href="http://llvm.org/doxygen/classllvm_1_1MemoryBuffer.html">
|
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MemoryBuffer</a> instead.</li>
|
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<li>The '<tt>-enable-eh</tt>' flag to llc has been removed. Now code should
|
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encode whether it is safe to omit unwind information for a function by
|
|
tagging the Function object with the '<tt>nounwind</tt>' attribute.</li>
|
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<li>The ConstantFP::get method that uses APFloat now takes one argument
|
|
instead of two. The type argument has been removed, and the type is
|
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now inferred from the size of the given APFloat value.</li>
|
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|
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="otherprojects">Other LLVM Sub-Projects</a>
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</div>
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<div class="doc_text">
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<p>
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The core LLVM 2.3 distribution currently consists of code from the core LLVM
|
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repository (which roughly contains the LLVM optimizer, 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 new <a href="#vmkit">vmkit Project</a>
|
|
and the <a href="#clang">Clang Project</a>.
|
|
</p>
|
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</div>
|
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|
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<!--=========================================================================-->
|
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<div class="doc_subsubsection">
|
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<a name="vmkit">vmkit</a>
|
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</div>
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|
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<div class="doc_text">
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<p>
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The "vmkit" project is a new addition to the LLVM family. It 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>
|
|
|
|
<p>The JVM, called JnJVM, executes real-world applications such as Apache
|
|
projects (e.g. Felix and Tomcat) and the SpecJVM98 benchmark. It uses the GNU
|
|
Classpath project for the base classes. The CLI implementation, called N3, is
|
|
its in early stages but can execute simple applications and the "pnetmark"
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|
benchmark. It uses the pnetlib project as its core library.</p>
|
|
|
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<p>The 'vmkit' VMs compare in performance with industrial and top open-source
|
|
VMs on scientific applications. Besides the JIT, the VMs use many features of
|
|
the LLVM framework, including the standard set of optimizations, atomic
|
|
operations, custom function provider and memory manager for JITed methods, and
|
|
specific virtual machine optimizations. vmkit is not an official part of LLVM
|
|
2.3 release. It is publicly available under the LLVM license and can be
|
|
downloaded from:
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|
</p>
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<div class="doc_code">
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<pre>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</pre>
|
|
</div>
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|
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</div>
|
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|
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<!--=========================================================================-->
|
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<div class="doc_subsubsection">
|
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<a name="clang">Clang</a>
|
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</div>
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|
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<div class="doc_text">
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|
|
<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>At this point, Clang is most useful if you are interested in source-to-source
|
|
transformations (such as refactoring) and other source-level tools for C and
|
|
Objective-C. Clang now also includes tools for turning C code into pretty HTML,
|
|
and includes a new <a href="http://clang.llvm.org/StaticAnalysis.html">static
|
|
analysis tool</a> in development. This tool focuses on automatically finding
|
|
bugs in C and Objective-C code.</p>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="whatsnew">What's New?</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM 2.3 includes a huge number of bug fixes, performance tweaks and minor
|
|
improvements. Some of the major improvements and new features are listed in
|
|
this section.
|
|
</p>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
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<div class="doc_subsection">
|
|
<a name="majorfeatures">Major New Features</a>
|
|
</div>
|
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|
|
<div class="doc_text">
|
|
|
|
<p>LLVM 2.3 includes several major new capabilities:</p>
|
|
|
|
<ul>
|
|
<li><p>The biggest change in LLVM 2.3 is Multiple Return Value (MRV) support.
|
|
MRVs allow LLVM IR to directly represent functions that return multiple
|
|
values without having to pass them "by reference" in the LLVM IR. This
|
|
allows a front-end to generate more efficient code, as MRVs are generally
|
|
returned in registers if a target supports them. See the <a
|
|
href="LangRef.html#i_getresult">LLVM IR Reference</a> for more details.</p>
|
|
|
|
<p>MRVs are fully supported in the LLVM IR, but are not yet fully supported in
|
|
on all targets. However, it is generally safe to return up to 2 values from
|
|
a function: most targets should be able to handle at least that. MRV
|
|
support is a critical requirement for X86-64 ABI support, as X86-64 requires
|
|
the ability to return multiple registers from functions, and we use MRVs to
|
|
accomplish this in a direct way.</p></li>
|
|
|
|
<li><p>LLVM 2.3 includes a complete reimplementation of the "<tt>llvmc</tt>"
|
|
tool. It is designed to overcome several problems with the original
|
|
<tt>llvmc</tt> and to provide a superset of the features of the
|
|
'<tt>gcc</tt>' driver.</p>
|
|
|
|
<p>The main features of <tt>llvmc2</tt> are:
|
|
<ul>
|
|
<li>Extended handling of command line options and smart rules for
|
|
dispatching them to different tools.</li>
|
|
<li>Flexible (and extensible) rules for defining different tools.</li>
|
|
<li>The different intermediate steps performed by tools are represented
|
|
as edges in the abstract graph.</li>
|
|
<li>The 'language' for driver behavior definition is tablegen and thus
|
|
it's relatively easy to add new features.</li>
|
|
<li>The definition of driver is transformed into set of C++ classes, thus
|
|
no runtime interpretation is needed.</li>
|
|
</ul>
|
|
</li>
|
|
|
|
<li><p>LLVM 2.3 includes a completely rewritten interface for <a
|
|
href="LinkTimeOptimization.html">Link Time Optimization</a>. This interface
|
|
is written in C, which allows for easier integration with C code bases, and
|
|
incorporates improvements we learned about from the first incarnation of the
|
|
interface.</p></li>
|
|
|
|
<li><p>The <a href="tutorial/LangImpl1.html">Kaleidoscope tutorial</a> now
|
|
includes a "port" of the tutorial that <a
|
|
href="tutorial/OCamlLangImpl1.html">uses the Ocaml bindings</a> to implement
|
|
the Kaleidoscope language.</p></li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end, and includes support
|
|
for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
|
|
|
|
<p>
|
|
<ul>
|
|
<li>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
|
|
front-end. Objective-C now works very well on Mac OS/X.</li>
|
|
|
|
<li>Fortran <tt>EQUIVALENCE</tt>s are now supported by the gfortran
|
|
front-end.</li>
|
|
|
|
<li>llvm-gcc 4.2 includes many other fixes which improve conformance with the
|
|
relevant parts of the GCC testsuite.</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="coreimprovements">LLVM Core Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>New features include:
|
|
</p>
|
|
|
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<ul>
|
|
<li>LLVM IR now directly represents "common" linkage, instead of representing it
|
|
as a form of weak linkage.</li>
|
|
|
|
<li>LLVM IR now has support for atomic operations, and this functionality can be
|
|
accessed through the llvm-gcc "<tt>__sync_synchronize</tt>",
|
|
"<tt>__sync_val_compare_and_swap</tt>", and related builtins. Support for
|
|
atomics are available in the Alpha, X86, X86-64, and PowerPC backends.</li>
|
|
|
|
<li>The C and Ocaml bindings have extended to cover pass managers, several
|
|
transformation passes, iteration over the LLVM IR, target data, and parameter
|
|
attribute lists.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="optimizer">Optimizer Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>In addition to a huge array of bug fixes and minor performance tweaks, the
|
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LLVM 2.3 optimizers support a few major enhancements:</p>
|
|
|
|
<ul>
|
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<li><p>Loop index set splitting on by default.
|
|
This transformation hoists conditions from loop bodies and reduces a loop's
|
|
iteration space to improve performance. For example,</p>
|
|
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<div class="doc_code">
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<pre>
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for (i = LB; i < UB; ++i)
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if (i <= NV)
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LOOP_BODY
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</pre>
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</div>
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<p>is transformed into:</p>
|
|
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<p><div class="doc_code">
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<pre>
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NUB = min(NV+1, UB)
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for (i = LB; i < NUB; ++i)
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LOOP_BODY
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</pre>
|
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</div>
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</p>
|
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</li>
|
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<li>LLVM now includes a new <tt>memcpy</tt> optimization pass which removes
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dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and performs
|
|
return slot optimization. The LLVM optimizer now notices long sequences of
|
|
consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li>
|
|
|
|
<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
|
|
<tt>memset</tt> is now more aggressive.</li>
|
|
|
|
<li>The Aggressive Dead Code Elimination (ADCE) optimization has been rewritten
|
|
to make it both faster and safer in the presence of code containing infinite
|
|
loops. Some of its prior functionality has been factored out into the loop
|
|
deletion pass, which <em>is</em> safe for infinite loops. The new ADCE pass is
|
|
no longer based on control dependence, making it run faster.</li>
|
|
|
|
<li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm
|
|
functions for C-based languages, has been rewritten to be a FunctionPass
|
|
instead a ModulePass. This allows it to be run more often and to be
|
|
included at -O1 in llvm-gcc. It was also extended to include more
|
|
optimizations and several corner case bugs were fixed.</li>
|
|
|
|
<li>LLVM now includes a simple 'Jump Threading' pass, which attempts to simplify
|
|
conditional branches using information about predecessor blocks, simplifying
|
|
the control flow graph. This pass is pretty basic at this point, but
|
|
catches some important cases and provides a foundation to build on.</li>
|
|
|
|
<li>Several corner case bugs which could lead to deleting volatile memory
|
|
accesses have been fixed.</li>
|
|
|
|
<li>Several optimizations have been sped up, leading to faster code generation
|
|
with the same code quality.</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="codegen">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>
|
|
|
|
<ul>
|
|
<li>The code generator now has support for carrying information about memory
|
|
references throughout the entire code generation process, via the
|
|
<a href="http://llvm.org/doxygen/classllvm_1_1MachineMemOperand.html">
|
|
MachineMemOperand</a> class. In the future this will be used to improve
|
|
both pre-pass and post-pass scheduling, and to improve compiler-debugging
|
|
output.</li>
|
|
|
|
<li>The target-independent code generator infrastructure now uses LLVM's
|
|
<a href="http://llvm.org/doxygen/classllvm_1_1APInt.html">APInt</a>
|
|
class to handle integer values, which allows it to support integer types
|
|
larger than 64 bits (for example i128). Note that support for such types is
|
|
also dependent on target-specific support. Use of APInt is also a step
|
|
toward support for non-power-of-2 integer sizes.</li>
|
|
|
|
<li>LLVM 2.3 includes several compile time speedups for code with large basic
|
|
blocks, particularly in the instruction selection phase, register
|
|
allocation, scheduling, and tail merging/jump threading.</li>
|
|
|
|
<li>LLVM 2.3 includes several improvements which make llc's
|
|
<tt>--view-sunit-dags</tt> visualization of scheduling dependency graphs
|
|
easier to understand.</li>
|
|
|
|
<li>The code generator allows targets to write patterns that generate subreg
|
|
references directly in .td files now.</li>
|
|
|
|
<li><tt>memcpy</tt> lowering in the backend is more aggressive, particularly for
|
|
<tt>memcpy</tt> calls introduced by the code generator when handling
|
|
pass-by-value structure argument copies.</li>
|
|
|
|
<li>Inline assembly with multiple register results now returns those results
|
|
directly in the appropriate registers, rather than going through memory.
|
|
Inline assembly that uses constraints like "ir" with immediates now use the
|
|
'i' form when possible instead of always loading the value in a register.
|
|
This saves an instruction and reduces register use.</li>
|
|
|
|
<li>Added support for PIC/GOT style <a
|
|
href="CodeGenerator.html#tailcallopt">tail calls</a> on X86/32 and initial
|
|
support for tail calls on PowerPC 32 (it may also work on PowerPC 64 but is
|
|
not thoroughly tested).</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="x86specific">X86/X86-64 Specific Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>New target-specific features include:
|
|
</p>
|
|
|
|
<ul>
|
|
<li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the
|
|
area of passing and returning structures by value. llvm-gcc compiled code
|
|
now interoperates very well on X86-64 systems with other compilers.</li>
|
|
|
|
<li>Support for Win64 was added. This includes code generation itself, JIT
|
|
support, and necessary changes to llvm-gcc.</li>
|
|
|
|
<li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and
|
|
the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins. Various
|
|
generic vector operations (insert/extract/shuffle) are much more efficient
|
|
when SSE 4.1 is enabled. The JIT automatically takes advantage of these
|
|
instructions, but llvm-gcc must be explicitly told to use them, e.g. with
|
|
<tt>-march=penryn</tt>.</li>
|
|
|
|
<li>The X86 backend now does a number of optimizations that aim to avoid
|
|
converting numbers back and forth from SSE registers to the X87 floating
|
|
point stack. This is important because most X86 ABIs require return values
|
|
to be on the X87 Floating Point stack, but most CPUs prefer computation in
|
|
the SSE units.</li>
|
|
|
|
<li>The X86 backend supports stack realignment, which is particularly useful for
|
|
vector code on OS's without 16-byte aligned stacks, such as Linux and
|
|
Windows.</li>
|
|
|
|
<li>The X86 backend now supports the "sseregparm" options in GCC, which allow
|
|
functions to be tagged as passing floating point values in SSE
|
|
registers.</li>
|
|
|
|
<li>Trampolines (taking the address of a nested function) now work on
|
|
Linux/X86-64.</li>
|
|
|
|
<li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch
|
|
instructions instead of being ignored.</li>
|
|
|
|
<li>128-bit integers are now supported on X86-64 targets. This can be used
|
|
through <tt>__attribute__((TImode))</tt> in llvm-gcc.</li>
|
|
|
|
<li>The register allocator can now rematerialize PIC-base computations, which is
|
|
an important optimization for register use.</li>
|
|
|
|
<li>The "t" and "f" inline assembly constraints for the X87 floating point stack
|
|
now work. However, the "u" constraint is still not fully supported.</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="targetspecific">Other Target Specific Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>New target-specific features include:
|
|
</p>
|
|
|
|
<ul>
|
|
<li>The LLVM C backend now supports vector code.</li>
|
|
<li>The Cell SPU backend includes a number of improvements. It generates better
|
|
code and its stability/completeness is improving.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="otherimprovements">Other Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>New features include:
|
|
</p>
|
|
|
|
<ul>
|
|
<li>LLVM now builds with GCC 4.3.</li>
|
|
<li>Bugpoint now supports running custom scripts (with the <tt>-run-custom</tt>
|
|
option) to determine how to execute the command and whether it is making
|
|
forward process.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="portability">Portability and Supported Platforms</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM is known to work on the following platforms:</p>
|
|
|
|
<ul>
|
|
<li>Intel and AMD machines (IA32) 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 running on Win32 using MinGW libraries (native).</li>
|
|
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
|
|
support is available for native builds with Visual C++).</li>
|
|
<li>Sun UltraSPARC workstations running Solaris 10.</li>
|
|
<li>Alpha-based machines running Debian GNU/Linux.</li>
|
|
<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
|
|
</ul>
|
|
|
|
<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
|
|
to the machine and operating system on which it is built. However, minor
|
|
porting may be required to get LLVM to work on new platforms. We welcome your
|
|
portability patches and reports of successful builds or error messages.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="knownproblems">Known Problems</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>This section contains 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
|
|
href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
|
|
there isn't already one.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="experimental">Experimental features included with this release</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The following components of this LLVM release are either untested, known to
|
|
be broken or unreliable, or are in early development. These components should
|
|
not be relied on, and bugs should not be filed against them, but they may be
|
|
useful to some people. In particular, if you would like to work on one of these
|
|
components, please contact us on the <a
|
|
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
|
|
|
|
<ul>
|
|
<li>The MSIL, 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>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="x86-be">Known problems with the X86 back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>The X86 backend does not yet support
|
|
all <a href="http://llvm.org/PR879">inline assembly that uses the X86
|
|
floating point stack</a>. It supports the 'f' and 't' constraints, but not
|
|
'u'.</li>
|
|
<li>The X86 backend generates inefficient floating point code when configured
|
|
to generate code for systems that don't have SSE2.</li>
|
|
<li>Win64 code generation wasn't widely tested. Everything should work, but we
|
|
expect small issues to happen. Also, llvm-gcc cannot build 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>
|
|
<li>The X86-64 backend does not yet support position-independent code (PIC)
|
|
generation on Linux targets.</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
|
|
argument constructs on X86-64 by lowering them manually.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ppc-be">Known problems with the PowerPC back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>The Linux PPC32/ABI support needs testing for the interpreter and static
|
|
compilation, and lacks support for debug information.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="arm-be">Known problems with the ARM back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>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>
|
|
<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_subsection">
|
|
<a name="sparc-be">Known problems with the SPARC back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
|
|
support the 64-bit SPARC ABI (-m64).</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="alpha-be">Known problems with the Alpha back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
|
|
<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
|
|
appropriate nops inserted to ensure restartability.</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ia64-be">Known problems with the IA64 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>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="c-be">Known problems with the C back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li><a href="http://llvm.org/PR802">The C backend has only basic support for
|
|
inline assembly code</a>.</li>
|
|
<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
|
|
C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
|
|
C++ code compiled with llc or native compilers.</li>
|
|
<li>The C backend does not support all exception handling constructs.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="c-fe">Known problems with the llvm-gcc C front-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>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>
|
|
</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, including
|
|
X86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is
|
|
supported on X86-64 linux, but that is disabled by default in this release.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
|
|
technology and problems should be expected.
|
|
<ul>
|
|
<li>The Ada front-end currently only builds on X86-32. This is mainly due
|
|
to lack of trampoline support (pointers to nested functions) on other platforms,
|
|
however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
|
|
which does support trampolines.</li>
|
|
<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
|
|
Workaround: configure with --disable-bootstrap.</li>
|
|
<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
|
|
fail (c380004 also fails with gcc-4.2 mainline). When built at -O3, the
|
|
<a href="http://llvm.org/PR2421">cxg2021</a> ACATS test also fails.</li>
|
|
<li>Some gcc specific Ada tests continue to crash the compiler. The testsuite
|
|
reports most tests as having failed even though they pass.</li>
|
|
<li>The -E 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>
|
|
<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
|
|
or finish at a non-byte offset</a> in a record. Workaround: do not pack records
|
|
or use representation clauses that result in a field of a non-discrete type
|
|
starting or finishing in the middle of a byte.</li>
|
|
<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
|
|
'main' as generated by the Ada binder to be invalid</a>.
|
|
Workaround: hand edit the file to use pointers for <tt>argv</tt> and
|
|
<tt>envp</tt> rather than integers.</li>
|
|
<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
|
|
ignored</a>.</li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="additionalinfo">Additional Information</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>A wide variety of additional information is available on the <a
|
|
href="http://llvm.org">LLVM web page</a>, in particular in the <a
|
|
href="http://llvm.org/docs/">documentation</a> section. The web page also
|
|
contains versions of the API documentation which is up-to-date with the
|
|
Subversion version of the source code.
|
|
You can access versions of these documents specific to this release by going
|
|
into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
|
|
|
|
<p>If you have any questions or comments about LLVM, please feel free to contact
|
|
us via the <a href="http://llvm.org/docs/#maillist"> mailing
|
|
lists</a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
<hr>
|
|
<address>
|
|
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
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src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
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<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
|
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Last modified: $Date$
|
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</address>
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