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			45 KiB
		
	
	
	
		
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			1183 lines
		
	
	
		
			45 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
| <!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 2.6 Release Notes</title>
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| </head>
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| <body>
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| 
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| <div class="doc_title">LLVM 2.6 Release Notes</div>
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| 
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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 2.6</a></li>
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|   <li><a href="#whatsnew">What's New in LLVM 2.6?</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></li>
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|   <li><a href="#additionalinfo">Additional Information</a></li>
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| </ol>
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| 
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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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| 
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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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| 
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| <div class="doc_text">
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| 
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| <p>This document contains the release notes for the LLVM Compiler
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| Infrastructure, release 2.6.  Here we describe the status of LLVM, including
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| major improvements from the previous release and significant known problems.
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| All LLVM releases may be downloaded from the <a
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| 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
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| release, please check out the <a href="http://llvm.org/">main LLVM
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| web site</a>.  If you have questions or comments, the <a
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| 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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| <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 release, please see the
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| <a href="http://llvm.org/releases/">releases page</a>.</p>
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| 
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| </div>
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|  
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| 
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| <!--
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| Almost dead code.
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|   include/llvm/Analysis/LiveValues.h => Dan
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|   lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
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|   llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
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| -->
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|  
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|    
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| <!-- Unfinished features in 2.6:
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|   gcc plugin.
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|   strong phi elim
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|   variable debug info for optimized code
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|   postalloc scheduler: anti dependence breaking, hazard recognizer?
 | |
|   metadata
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|   loop dependence analysis
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|   ELF Writer?  How stable?
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|   <li>PostRA scheduler improvements, ARM adoption (David Goodwin).</li>
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|   2.7 supports the GDB 7.0 jit interfaces for debug info.
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|  -->
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| 
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|  <!-- for announcement email:
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|  Logo web page.
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|  llvm devmtg
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|  compiler_rt
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|  klee web page at klee.llvm.org
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|  Many new papers added to /pubs/
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|    Mention gcc plugin.
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| 
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|    -->
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| 
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| <!-- *********************************************************************** -->
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| <div class="doc_section">
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|   <a name="subproj">Sub-project Status Update</a>
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| </div>
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| <!-- *********************************************************************** -->
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| 
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| <div class="doc_text">
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| <p>
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| The LLVM 2.6 distribution currently consists of code from the core LLVM
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| repository —which roughly includes the LLVM optimizers, code generators
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| 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
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| two which are the most actively developed are the <a href="#clang">Clang
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| Project</a> and the <a href="#vmkit">VMKit Project</a>.
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| </p>
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| 
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| </div>
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| 
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| 
 | |
| <!--=========================================================================-->
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| <div class="doc_subsection">
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| <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
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| </div>
 | |
| 
 | |
| <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 C family of languages.
 | |
| LLVM 2.6 is the first release to officially include Clang, and it provides a
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| production quality C and Objective-C compiler.  If you are interested in fast
 | |
| compiles and good diagnostics, we encourage you to try it out.</p>
 | |
| 
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| <p>In addition to supporting these languages, C++ support is also <a
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| href="http://clang.llvm.org/cxx_status.html">well under way</a>, and mainline
 | |
| Clang is able to parse the libstdc++ 4.2 headers and even codegen simple apps.
 | |
| If you are interested in Clang C++ support or any other Clang feature, we
 | |
| strongly encourage you to get involved on the <a 
 | |
| href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
 | |
| list</a>.</p>
 | |
| 
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| <p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
 | |
| 
 | |
| <ul>
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| <li>C and Objective-C support are now considered production quality.</li>
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| <li>AuroraUX / FreeBSD & OpenBSD Toolchain support.</li>
 | |
| <li>Most of Objective-C 2.0 is now supported with the GNU runtime.</li>
 | |
| <li>Many many bugs are fixed and many features have been added.</li>
 | |
| </ul>
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
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| <a name="clangsa">Clang Static Analyzer</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
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| <p><b>UPDATE!</b> Previously announced in the 2.4 and 2.5 LLVM releases, the Clang project also
 | |
| includes an early stage static source code analysis tool for <a
 | |
| href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
 | |
| in C and Objective-C programs. The tool performs a growing set of checks to find
 | |
| bugs that occur on a specific path within a program.</p>
 | |
| 
 | |
| <p>In the LLVM 2.6 time-frame there have been many significant improvements to
 | |
| XYZ.</p>
 | |
| 
 | |
| <p>The set of checks performed by the static analyzer continues to expand, and
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| future plans for the tool include full source-level inter-procedural analysis
 | |
| and deeper checks such as buffer overrun detection. There are many opportunities
 | |
| to extend and enhance the static analyzer, and anyone interested in working on
 | |
| this project is encouraged to get involved!</p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
 | |
| a JVM and a CLI Virtual Machine (Microsoft .NET is an
 | |
| implementation of the CLI) using LLVM for static and just-in-time
 | |
| compilation.</p>
 | |
| 
 | |
| <p>
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| VMKit version 0.26 builds with LLVM 2.6 and you can find it on its
 | |
| <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
 | |
| bug fixes, cleanup and new features. The major changes are:</p>
 | |
| 
 | |
| <ul>
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| 
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| <li>A new llcj tool to generate shared libraries or executables of Java
 | |
|     files.</li>
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| <li>Cooperative garbage collection. </li>
 | |
| <li>Fast subtype checking (paper from Click et al [JGI'02]). </li>
 | |
| <li>Implementation of a two-word header for Java objects instead of the orginal
 | |
|     three-word header. </li>
 | |
| <li>Better Java specification-compliance: division by zero checks, stack
 | |
|     overflow checks, finalization and references support. </li>
 | |
| 
 | |
| </ul>
 | |
| </div>
 | |
| 
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
 | |
| is a simple library that provides an implementation of the low-level
 | |
| target-specific hooks required by code generation and other runtime components.
 | |
| For example, when compiling for a 32-bit target, converting a double to a 64-bit
 | |
| unsigned integer is compiling into a runtime call to the "__fixunsdfdi"
 | |
| function. The compiler-rt library provides optimized implementations of this and
 | |
| other low-level routines.</p>
 | |
| 
 | |
| <p>
 | |
| All of the code in the compiler-rt project is available under the standard LLVM
 | |
| License, a "BSD-style" license.</p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="klee">klee: Symbolic Execution and Automatic Test Case Generator</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| The new LLVM <a href="http://klee.llvm.org/">klee project</a> is a symbolic
 | |
| execution framework for programs in LLVM bitcode form.  Klee tries to
 | |
| symbolically evaluate "all" paths through the application and records state
 | |
| transitions that lead to fault states.  This allows it to construct testcases
 | |
| that lead to faults and can even be used to verify algorithms.  For more
 | |
| details, please see the <a
 | |
| href="http://llvm.org/pubs/2008-12-OSDI-KLEE.html">OSDI 2008 paper</a> about
 | |
| Klee.</p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="dragonegg">Dragon Egg: An LLVM backend plugin for GCC</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| <b>Duncan needs to write me</b>.
 | |
| </p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="mc">llvm-mc: Machine Code Toolkit</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| The LLVM Machine Code (MC) Toolkit project is a (very early) effort to build
 | |
| better tools for dealing with machine code, object file formats, etc.  The idea
 | |
| is to be able to generate most of the target specific details of assemblers and
 | |
| disassemblers from existing LLVM target .td files (with suitable enhancements),
 | |
| and to build infrastructure for reading and writing common object file formats.
 | |
| One of the first deliverables is to build a full assembler and integrate it into
 | |
| the compiler, which is predicted to substantially reduce compile time in some
 | |
| scenarios.
 | |
| </p>
 | |
| 
 | |
| <p>In the LLVM 2.6 timeframe, the MC framework has grown to the point where it
 | |
| can reliably parse and pretty print (with some encoding information) a
 | |
| darwin/x86 .s file successfully, and has the very early phases of a Mach-O
 | |
| assembler in progress.  Beyond the MC framework itself, major refactoring of the
 | |
| LLVM code generator has started.  The idea is to make the code generator reason
 | |
| about the code it is producing in a much more semantic way, rather than a
 | |
| textual way.  For example, the code generator now uses MCSection objects to
 | |
| represent section assignments, instead of text strings that print to .section
 | |
| directives.</p>
 | |
| 
 | |
| <p>MC is an early and ongoing project that will hopefully continue to lead to
 | |
| many improvements in the code generator and build infrastructure useful for many
 | |
| other situations.
 | |
| </p>
 | |
| 
 | |
| </div>	
 | |
| 
 | |
| 
 | |
| <!-- *********************************************************************** -->
 | |
| <div class="doc_section">
 | |
|   <a name="externalproj">External Projects Using LLVM 2.6</a>
 | |
| </div>
 | |
| <!-- *********************************************************************** -->
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="Rubinius">Rubinius</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
 | |
| for running Ruby code which strives to write as much of the core class
 | |
| implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
 | |
| uses LLVM to optimize and compile ruby code down to machine code. Techniques
 | |
| such as type feedback, method inlining, and uncommon traps are all used to
 | |
| remove dynamism from ruby execution and increase performance.</p>
 | |
| 
 | |
| <p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
 | |
| a counter based JIT, type feedback, and speculative method inlining.
 | |
| </p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="macruby">MacRuby</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>
 | |
| <a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
 | |
| core Mac OS X technologies, such as the Objective-C common runtime and garbage
 | |
| collector, and the CoreFoundation framework. It is principally developed by
 | |
| Apple and aims at enabling the creation of full-fledged Mac OS X applications.
 | |
| </p>
 | |
| 
 | |
| <p>
 | |
| MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
 | |
| expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
 | |
| handling.</p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="pure">Pure</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| <a href="http://pure-lang.googlecode.com/">Pure</a>
 | |
| is an algebraic/functional programming language based on term rewriting.
 | |
| Programs are collections of equations which are used to evaluate expressions in
 | |
| a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
 | |
| lexical closures, a hygienic macro system (also based on term rewriting),
 | |
| built-in list and matrix support (including list and matrix comprehensions) and
 | |
| an easy-to-use C interface. The interpreter uses LLVM as a backend to
 | |
|  JIT-compile Pure programs to fast native code.</p>
 | |
| 
 | |
| <p>Pure versions 0.31 and later have been tested and are known to work with
 | |
| LLVM 2.6 (and continue to work with older LLVM releases >= 2.3 as well).
 | |
| </p>
 | |
| </div>
 | |
| 
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="ldc">LLVM D Compiler</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
 | |
| the D Programming Language using the LLVM optimizer and code generator.
 | |
| The LDC project works great with the LLVM 2.6 release.  General improvements in
 | |
| this
 | |
| cycle have included new inline asm constraint handling, better debug info
 | |
| support, general bugfixes, and better x86-64 support.  This has allowed
 | |
| some major improvements in LDC, getting us much closer to being as
 | |
| fully featured as the original DMD compiler from DigitalMars.
 | |
| </p>
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="RoadsendPHP">Roadsend PHP</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| <a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
 | |
| source implementation of the PHP programming 
 | |
| language that uses LLVM for its optimizer, JIT, and static compiler. This is a 
 | |
| reimplementation of an earlier project that is now based on LLVM.</p>
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="UnladenSwallow">Unladen Swallow</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| <a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
 | |
| branch of <a href="http://python.org/">Python</a> intended to be fully
 | |
| compatible and significantly faster.  It uses LLVM's optimization passes and JIT
 | |
| compiler.</p>
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="llvm-lua">llvm-lua</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>
 | |
| <a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
 | |
| & static compiling support to the Lua VM.  Lua bytecode is analyzed to
 | |
| remove type checks, then LLVM is used to compile those bytecodes down to machine
 | |
| code.</p>
 | |
| </div>
 | |
| 
 | |
| 
 | |
| 
 | |
| <!-- *********************************************************************** -->
 | |
| <div class="doc_section">
 | |
|   <a name="whatsnew">What's New in LLVM 2.6?</a>
 | |
| </div>
 | |
| <!-- *********************************************************************** -->
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>This release includes a huge number of bug fixes, performance tweaks, and
 | |
| minor improvements.  Some of the major improvements and new features are listed
 | |
| in this section.
 | |
| </p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="majorfeatures">Major New Features</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>LLVM 2.6 includes several major new capabilities:</p>
 | |
| 
 | |
| <ul>
 | |
| <li>New <a href="#compiler-rt">compiler-rt</a>, <A href="#klee">klee</a>,
 | |
|     and <a href="#mc">machine code toolkit</a> sub-projects.</li>
 | |
| <li>Debug information now includes line numbers when optimizations are enabled.
 | |
|     This allows statistical sampling tools like oprofile and Shark to map
 | |
|     samples back to source lines.</li>
 | |
| <li>LLVM now includes new experimental backends to support the MSP430, SystemZ,
 | |
|     and BlackFin architectures.</li>
 | |
| <li>LLVM supports a new <a href="GoldPlugin.html">Gold Linker Plugin</a> which
 | |
|     enables support for <a href="LinkTimeOptimization.html">transparent
 | |
|     link-time optimization</a> on ELF targets when used with the Gold binutils
 | |
|     linker.</li>
 | |
| <li>LLVM now supports doing optimization and code generation on multiple threads
 | |
|     by allowing multiple "LLVMContext" objects to exist.  Please see the <a 
 | |
|     href="ProgrammersManual.html#threading">threading entry in the Programmer's
 | |
|     Manual</a> for more information.</li>
 | |
| <li>LLVM now has experimental support for <a
 | |
|     href="http://nondot.org/~sabre/LLVMNotes/EmbeddedMetadata.txt">embedded
 | |
|     metadata</a> in LLVM IR, though the implementation is not guaranteed to be
 | |
|     final and the .bc file format may change in future releases.  Debug info 
 | |
|     does not yet use this format in LLVM 2.6.</p>
 | |
|     
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="coreimprovements">LLVM IR and Core Improvements</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>LLVM IR has several new features that are used by our existing front-ends and
 | |
| can be useful if you are writing a front-end for LLVM:</p>
 | |
| 
 | |
| <ul>
 | |
| <li>Getelementpr instruction now allows any integer type for array/pointer indexes.</li>
 | |
| <li>Inbounds for GEP</li>
 | |
| <li>NSW/NUW/exact div</li>
 | |
| <li>LSR promotes int induction variables to 64-bit on 64-bit targets, major perf boost for numerical code.</li>
 | |
| <li>LSR now analyzes pointer expressions (e.g. getelementptrs), not just integers.</li>
 | |
| <li>new linkage types linkonce_odr, weak_odr, linker_private, and available_externally.</li>
 | |
| <li>New fadd, fsub, fmul instructions and classes. </li>
 | |
| <li>Target intrinsics can now return multiple results.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="optimizer">Optimizer Improvements</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>In addition to a large array of bug fixes and minor performance tweaks, this
 | |
| release includes a few major enhancements and additions to the optimizers:</p>
 | |
| 
 | |
| <ul>
 | |
| 
 | |
| <li>SRoA improvements for vector unions, memset, arbitrary weird bitfield accesses etc.  It now produces "strange" sized integers.</li>
 | |
| <li>Inliner reuse stack space when inlining arrays?</li>
 | |
| <li>Enabled GVN Load PRE.</li>
 | |
| <li>New Static Single Information (SSI) construction pass (not used by anything yet, experimental).</li>
 | |
| </li>
 | |
| 
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="codegen">Target Independent Code Generator Improvements</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>We have put a significant amount of work into the code generator
 | |
| infrastructure, which allows us to implement more aggressive algorithms and make
 | |
| it run faster:</p>
 | |
| 
 | |
| <ul>
 | |
| 
 | |
| <li>    -asm-verbose now prints location info (with -g) and loop nest info.</li>
 | |
| <li>Tblgen now supports multiclass inheritance and a number of new string and
 | |
|     list operations like !(subst), !(foreach), !car, !cdr, !null, !if, !cast.
 | |
|     These make the .td files more expressive and allow more aggressive factoring
 | |
|     of duplication across instruction patterns.</li>
 | |
| <li>New MachineVerifier pass.</li>
 | |
| <li>Machine LICM, hoists things like constant pool loads, loads from readonly stubs, vector constant synthesization code, etc.</li>
 | |
| <li>Machine Sinking</li>
 | |
| <li>target-specific intrinsics (r63765)</li>
 | |
| <li>Regalloc improvements for commuting, various spiller peephole optimizations, cross-class coalescing.</li>
 | |
| <li><tt>llc -enable-value-prop</tt>, propagation of value info (sign/zero ext info) from one MBB to another</li>
 | |
| <li>Regalloc hints for allocation stuff: Evan r73381/r73671.  Finished/enabled?</li>
 | |
| <li>Stack slot coloring for register spills (denser stack frames)</li>
 | |
| <li>SelectionDAGS: New BuildVectorSDNode (r65296), and ISD::VECTOR_SHUFFLE (r69952 / PR2957)</li>
 | |
| <li>Experimental support for shrink wrapping support in PEI.</li>
 | |
| <li>Experimental support for writing ELF .o files directly from the compiler,
 | |
|     it works well for many simple C testcases, but doesn't support exception
 | |
|     handling, debug info, inline assembly, etc.</li>
 | |
| <li>Targets can now specify register allocation hints through
 | |
|    MachineRegisterInfo:: setRegAllocationHint. A regalloc hint consists 1) hint
 | |
|    type, 2) physical register number. A hint type of zero specifies a register
 | |
|    allocation preference. Other hint type values are target specific which are
 | |
|    resolved by TargetRegisterInfo::ResolveRegAllocHint. An example of which is
 | |
|    the ARM target can uses register hint to request that the register allocator
 | |
|    provide an even / odd register pair to two virtual registers.  It is
 | |
|    important to note the register allocation hints are just hints.  There is no
 | |
|    guarantee the register allocators will be able to satisfy the hints.</li>
 | |
|    
 | |
| </ul>
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="x86">X86-32 and X86-64 Target Improvements</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>New features of the X86 target include:
 | |
| </p>
 | |
| 
 | |
| <ul>
 | |
| 
 | |
| <li>Preliminary support for addrspace 256 -> GS, 257 -> FS, known problems: CodeGenerator.html#x86_memory</li>
 | |
| <li>Support for softfloat modes, typically used by OS kernels.</li>
 | |
| 
 | |
| <li>X86-64: better modeling of implicit zero extensions, eliminates a lot of redundant zexts</li>
 | |
| <li>X86-64 TLS support for local exec and initial exec.</li>
 | |
| <li>Better modeling of H registerts as subregs.</li>
 | |
| <li>Vector icmp/fcmp now work with SSE codegen.</li>
 | |
| <li>SSE 4.2 support.</li>
 | |
| <li>all global variable reference logic is now in ClassifyGlobalReference.</li>
 | |
| </li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="pic16">PIC16 Target Improvements</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>New features of the PIC16 target include:
 | |
| </p>
 | |
| 
 | |
| <ul>
 | |
| <li>Support for floating-point, indirect function calls, and
 | |
|     passing/returning aggregate types to functions.
 | |
| <li>The code generator is able to generate debug info into output COFF files.
 | |
| <li>Support for placing an object into a specific section or at a specific
 | |
|     address in memory.</li>
 | |
| </ul>
 | |
| 
 | |
| <p>Things not yet supported:</p>
 | |
| 
 | |
| <ul>
 | |
| <li>Variable arguments.</li>
 | |
| <li>Interrupts/programs.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="ARM">ARM Target Improvements</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>New features of the ARM target include:
 | |
| </p>
 | |
| 
 | |
| <ul>
 | |
| 
 | |
| <li>Preliminary support for processors, such as the Cortex-A8 and Cortex-A9,
 | |
| that implement version v7-A of the ARM architecture.  The ARM backend now
 | |
| supports both the Thumb2 and Advanced SIMD (Neon) instruction sets. The
 | |
| AAPCS-VFP "hard float" calling conventions are also supported with the
 | |
| <tt>-float-abi=hard</tt> flag. These features are still somewhat experimental
 | |
| and subject to change. The Neon intrinsics, in particular, may change in future
 | |
| releases of LLVM.
 | |
| </li>
 | |
| 
 | |
|   ARM AAPCS-VFP hard float ABI is supported. 
 | |
|   ARM calling convention code is now tblgen generated instead of manual.
 | |
|   ARM: NEON support. neonfp for doing single precision fp with neon instead of VFP.
 | |
| 
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="OtherTarget">Other Target Specific Improvements</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>New features of other targets include:
 | |
| </p>
 | |
| 
 | |
| <ul>
 | |
| <li>Mips now supports O32 Calling Convention.</li>
 | |
| <li>Many improvements to the 32-bit PowerPC SVR4 ABI (used on powerpc-linux)
 | |
|     support, lots of bugs fixed.</li>
 | |
| <li>Added support for the 64-bit PowerPC SVR4 ABI (used on powerpc64-linux).
 | |
|     Needs more testing.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="executionengine">Interpreter and JIT Improvements</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <ul>
 | |
| <li>The JIT now supports generating more than 16M of code.</li>
 | |
| <li>When configured with --with-oprofile, the JIT can now inform oprofile about
 | |
|      JIT'd code, allowing oprofile to get line number and function name
 | |
|      information for JIT'd functions.</li>
 | |
| <li>When "libffi" is available, the LLVM interpreter now uses it, which supports
 | |
|     calling almost arbitrary external (natively compiled) functions.</li>
 | |
| <li>Clients of the JIT can now register a 'JITEventListener' object to receive
 | |
|     callbacks when the JIT emits or frees machine code. The OProfile support
 | |
|     uses this mechanism.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="newapis">New Useful APIs</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <ul>
 | |
| <li>New EngineBuilder class for creating JITs: r76276</li>
 | |
|   New PrettyStackTrace, crashes of llvm tools should give some indication of what the compiler was doing at the time of the crash (e.g. running a pass), and print out command line arguments.
 | |
|   StringRef class, Twine class.
 | |
|     New WeakVH and AssertingVH and CallbackVH classes.
 | |
|   New llvm/ADT/Triple class.
 | |
|  llvm_report_error() error handling API (llvm/Support/ErrorHandling.h)
 | |
|   New llvm/System/Atomic.h, llvm/System/RWMutex.h for portable atomic ops, rw locks.
 | |
|   New SourceMgr, SMLoc classes for simple parsers with caret diagnostics and #include support, (used by
 | |
|     tablegen, llvm-mc, the .ll parser, FileCheck, etc)
 | |
| 
 | |
| </ul>
 | |
| 
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="otherimprovements">Other Improvements and New Features</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <p>Other miscellaneous features include:</p>
 | |
| 
 | |
| <ul>
 | |
| <li>LLVM now includes a new internal '<a 
 | |
|     href="http://llvm.org/cmds/FileCheck.html">FileCheck</a>' tool which allows
 | |
|     writing much more accurate regression tests that run faster.  Please see the
 | |
|     <a href="TestingGuide.html#FileCheck">FileCheck section of the Testing
 | |
|     Guide</a> for more information.</li>
 | |
| <li>LLVM profile information support has been significantly improved to produce
 | |
| correct use counts, and has support for edge profiling with reduced runtime
 | |
| overhead.  Combined, the generated profile information is both more correct and
 | |
| imposes about half as much overhead (2.6. from 12% to 6% overhead on SPEC
 | |
| CPU2000).</li>
 | |
| <li>Many extensions to the C APIs.</li>
 | |
| <li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005
 | |
| programming language.</li>
 | |
| 
 | |
| <li>LLVMC:
 | |
| 
 | |
| * Dynamic plugins now work on Windows.
 | |
| * New option property: init. Makes possible to provide default values for
 | |
|  options defined in plugins (interface to cl::init).
 | |
| * New example: Skeleton, shows how to create a standalone LLVMC-based driver.
 | |
| * New example: mcc16, a driver for the PIC16 toolchain.</li>
 | |
| 
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| 
 | |
| <!--=========================================================================-->
 | |
| <div class="doc_subsection">
 | |
| <a name="changes">Major Changes and Removed Features</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>If you're already an LLVM user or developer with out-of-tree changes based
 | |
| on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading
 | |
| from the previous release.</p>
 | |
| 
 | |
| <ul>
 | |
| 
 | |
| <li>The Itanium (IA64) backend has been removed.  It was not supported and
 | |
|     bitrotted.</li>
 | |
| <li>The BigBlock register allocator has been removed, it also bitrotted.</li>
 | |
| <li>The C Backend (-march=c) is no longer considered part of the LLVM release
 | |
| criteria.  We still want it to work, but no one is maintaining it and it lacks
 | |
| support for arbitrary precision integers and other important IR features.</li>
 | |
| </ul>
 | |
| 
 | |
|   LLVM build now builds all libraries as .a files instead of some
 | |
|   libraries as relinked .o files.  This requires some APIs like
 | |
|   InitializeAllTargets.h.  TargetRegistry! 
 | |
| 
 | |
| 
 | |
| 
 | |
| 
 | |
| <p>In addition, many APIs have changed in this release.  Some of the major LLVM
 | |
| API changes are:</p>
 | |
| 
 | |
| 
 | |
|   API Cleanup:
 | |
|     no use of hash_set/hash_map, no more llvm::OStream
 | |
|     Use raw_ostream for everything, killed off llvm/Streams.h and DOUT
 | |
| 
 | |
| <ul>
 | |
| <li>LLVM's global uniquing tables for <tt>Type</tt>s and <tt>Constant</tt>s have
 | |
|     been privatized into members of an <tt>LLVMContext</tt>.  A number of APIs
 | |
|     now take an <tt>LLVMContext</tt> as a parameter.  To smooth the transition
 | |
|     for clients that will only ever use a single context, the new 
 | |
|     <tt>getGlobalContext()</tt> API can be used to access a default global 
 | |
|     context which can be passed in any and all cases where a context is 
 | |
|     required.
 | |
| <li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
 | |
| <li>The <tt>Add</tt>, <tt>Sub</tt>, and <tt>Mul</tt> operators are no longer
 | |
|     overloaded for floating-point types. Floating-point addition, subtraction,
 | |
|     and multiplication are now represented with new operators <tt>FAdd</tt>,
 | |
|     <tt>FSub</tt>, and <tt>FMul</tt>. In the <tt>IRBuilder</tt> API,
 | |
|     <tt>CreateAdd</tt>, <tt>CreateSub</tt>, <tt>CreateMul</tt>, and
 | |
|     <tt>CreateNeg</tt> should only be used for integer arithmetic now;
 | |
|     <tt>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt>, and
 | |
|     <tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
 | |
| <li>The DynamicLibrary class can no longer be constructed, its functionality has
 | |
|     moved to static member functions.</li>
 | |
| <li><tt>raw_fd_ostream</tt>'s constructor for opening a given filename now
 | |
|     takes an extra <tt>Force</tt> argument. If <tt>Force</tt> is set to
 | |
|     <tt>false</tt>, an error will be reported if a file with the given name
 | |
|     already exists. If <tt>Force</tt> is set to <tt>true</tt>, the file will
 | |
|     be silently truncated (which is the behavior before this flag was
 | |
|     added).</li>
 | |
| <li><tt>SCEVHandle</tt> no longer exists, because reference counting is no
 | |
| longer done for <tt>SCEV*</tt> objects, instead <tt>const SCEV*</tt> should be
 | |
| used.</li>
 | |
| 
 | |
| <li>Many APIs, notably <tt>llvm::Value</tt>, now use the <tt>StringRef</tt>
 | |
| and <tt>Twine</tt> classes instead of passing <tt>const char*</tt>
 | |
| or <tt>std::string</tt>, as described in
 | |
| the <a href="ProgrammersManual.html#string_apis">Programmer's Manual</a>. Most
 | |
| clients should be unaffected by this transition, unless they are used to <tt>Value::getName()</tt> returning a string. Here are some tips on updating to 2.6:
 | |
|   <ul>
 | |
|     <li><tt>getNameStr()</tt> is still available, and matches the old
 | |
|       behavior. Replacing <tt>getName()</tt> calls with this is an safe option,
 | |
|       although more efficient alternatives are now possible.</li>
 | |
| 
 | |
|     <li>If you were just relying on <tt>getName()</tt> being able to be sent to
 | |
|       a <tt>std::ostream</tt>, consider migrating
 | |
|       to <tt>llvm::raw_ostream</tt>.</li>
 | |
|       
 | |
|     <li>If you were using <tt>getName().c_str()</tt> to get a <tt>const
 | |
|         char*</tt> pointer to the name, you can use <tt>getName().data()</tt>.
 | |
|         Note that this string (as before), may not be the entire name if the
 | |
|         name containts embedded null characters.</li>
 | |
| 
 | |
|     <li>If you were using operator plus on the result of <tt>getName()</tt> and
 | |
|       treating the result as an <tt>std::string</tt>, you can either
 | |
|       uses <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
 | |
|       could move to a <tt>Twine</tt> based design.</li>
 | |
| 
 | |
|     <li><tt>isName()</tt> should be replaced with comparison
 | |
|       against <tt>getName()</tt> (this is now efficient).
 | |
|   </ul>
 | |
| </li>
 | |
| 
 | |
| <li>The registration interfaces for backend Targets has changed (what was
 | |
| previously TargetMachineRegistry). For backend authors, see the <a href="WritingAnLLVMBackend.html#TargetRegistration">Writing An LLVM Backend</a> guide. For clients, the notable API changes are:
 | |
|   <ul>
 | |
|     <li><tt>TargetMachineRegistry</tt> has been renamed
 | |
|       to <tt>TargetRegistry</tt>.</li>
 | |
| 
 | |
|     <li>Clients should move to using the <tt>TargetRegistry::lookupTarget()</tt>
 | |
|       function to find targets.</li>
 | |
|   </ul>
 | |
| </li>
 | |
| 
 | |
| <li>llvm-dis now fails if output file exists, instead of dumping to stdout.
 | |
| FIXME: describe any other tool changes due to the raw_fd_ostream change.  FIXME:
 | |
| This is not an API change, maybe there should be a tool changes section?</li>
 | |
| <li>temporarely due to Context API change passes should call doInitialization()
 | |
| method of the pass they inherit from, otherwise Context is NULL.
 | |
| FIXME: remove this entry when this is no longer needed.<li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| 
 | |
| 
 | |
| <!-- *********************************************************************** -->
 | |
| <div class="doc_section">
 | |
|   <a name="portability">Portability and Supported Platforms</a>
 | |
| </div>
 | |
| <!-- *********************************************************************** -->
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>LLVM is known to work on the following platforms:</p>
 | |
| 
 | |
| <ul>
 | |
| <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
 | |
| Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like systems).</li>
 | |
| <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
 | |
| and 64-bit modes.</li>
 | |
| <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
 | |
| <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
 | |
|     support is available for native builds with Visual C++).</li>
 | |
| <li>Sun UltraSPARC workstations running Solaris 10.</li>
 | |
| <li>Alpha-based machines running Debian GNU/Linux.</li>
 | |
| </ul>
 | |
| 
 | |
| <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
 | |
| to the machine and operating system on which it is built.  However, minor
 | |
| porting may be required to get LLVM to work on new platforms.  We welcome your
 | |
| portability patches and reports of successful builds or error messages.</p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- *********************************************************************** -->
 | |
| <div class="doc_section">
 | |
|   <a name="knownproblems">Known Problems</a>
 | |
| </div>
 | |
| <!-- *********************************************************************** -->
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>This section contains significant known problems with the LLVM system,
 | |
| listed by component.  If you run into a problem, please check the <a
 | |
| href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
 | |
| there isn't already one.</p>
 | |
| 
 | |
| <ul>
 | |
| <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
 | |
| using the stock GCC 3.x.x series 'out the box',
 | |
| See: <a href="#brokengcc">Broken versions of GCC and other tools</a>.
 | |
| However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
 | |
| for x86/x64 has been made available from the third party AuroraUX Project
 | |
| that has been meticulously tested for bootstrapping LLVM & Clang.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="experimental">Experimental features included with this release</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>The following components of this LLVM release are either untested, known to
 | |
| be broken or unreliable, or are in early development.  These components should
 | |
| not be relied on, and bugs should not be filed against them, but they may be
 | |
| useful to some people.  In particular, if you would like to work on one of these
 | |
| components, please contact us on the <a
 | |
| href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
 | |
| 
 | |
| <ul>
 | |
| <li>The MSIL, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
 | |
| <li>The <tt>llc</tt> "<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 the mingw64
 | |
|     runtime currently due
 | |
|     to <a href="http://llvm.org/PR2255">several</a>
 | |
|     <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
 | |
|     the
 | |
|     'u' inline assembly constraint and for X87 floating point inline assembly.</li>
 | |
|   <li>The X86-64 backend does not yet support the LLVM IR instruction
 | |
|       <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
 | |
|       argument constructs on X86-64 by lowering them manually.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="ppc-be">Known problems with the PowerPC back-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <ul>
 | |
| <li>The Linux PPC32/ABI support needs testing for the interpreter and static
 | |
| compilation, and lacks support for debug information.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="arm-be">Known problems with the ARM back-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <ul>
 | |
| <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
 | |
| and not well tested.  Some features may not work at all, and the code quality
 | |
| may be poor in some cases.</li>
 | |
| <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
 | |
| processors, thumb programs can crash or produce wrong
 | |
| results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
 | |
| <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
 | |
| </li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="sparc-be">Known problems with the SPARC back-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <ul>
 | |
| <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
 | |
|     support the 64-bit SPARC ABI (-m64).</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="mips-be">Known problems with the MIPS back-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <ul>
 | |
| <li>The O32 ABI is not fully supported.</li>
 | |
| <li>64-bit MIPS targets are not supported yet.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="alpha-be">Known problems with the Alpha back-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <ul>
 | |
| 
 | |
| <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
 | |
| appropriate nops inserted to ensure restartability.</li>
 | |
| 
 | |
| </ul>
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="c-be">Known problems with the C back-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <ul>
 | |
| <li><a href="http://llvm.org/PR802">The C backend has only basic support for
 | |
|     inline assembly code</a>.</li>
 | |
| <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
 | |
|     C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
 | |
|     C++ code compiled with <tt>llc</tt> or native compilers.</li>
 | |
| <li>The C backend does not support all exception handling constructs.</li>
 | |
| <li>The C backend does not support arbitrary precision integers.</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>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. Currently
 | |
|   only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
 | |
| </ul>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| <ul>
 | |
| <li>Fortran support generally works, but there are still several unresolved bugs
 | |
|     in Bugzilla.  Please see the tools/gfortran component for details.</li>
 | |
| </ul>
 | |
| </div>
 | |
| 
 | |
| <!-- ======================================================================= -->
 | |
| <div class="doc_subsection">
 | |
|   <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
 | |
| technology, and problems should be expected.
 | |
| <ul>
 | |
| <li>The Ada front-end currently only builds on X86-32.  This is mainly due
 | |
| to lack of trampoline support (pointers to nested functions) on other platforms.
 | |
| However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
 | |
| which does support trampolines.</li>
 | |
| <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
 | |
| This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
 | |
| exception handling, which is used internally by the compiler.
 | |
| Workaround: configure with --disable-bootstrap.</li>
 | |
| <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
 | |
| and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
 | |
| (c380004 also fails with gcc-4.2 mainline).
 | |
| If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
 | |
| causes the compiler to go into an infinite loop, using up all system memory.</li>
 | |
| <li>Some GCC specific Ada tests continue to crash the compiler.</li>
 | |
| <li>The -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_subsection">
 | |
| 	<a name="ocaml-bindingse">Known problems with the O'Caml bindings</a>
 | |
| </div>
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>The Llvm.Linkage module is broken, and has incorrect values. Only
 | |
| Llvm.Linkage.External, Llvm.Linkage.Available_externally, and
 | |
| Llvm.Linkage.Link_once will be correct. If you need any of the other linkage
 | |
| modes, you'll have to write an external C library in order to expose the
 | |
| functionality. This has been fixed in the trunk.</p>
 | |
| </div>
 | |
| 
 | |
| <!-- *********************************************************************** -->
 | |
| <div class="doc_section">
 | |
|   <a name="additionalinfo">Additional Information</a>
 | |
| </div>
 | |
| <!-- *********************************************************************** -->
 | |
| 
 | |
| <div class="doc_text">
 | |
| 
 | |
| <p>A wide variety of additional information is available on the <a
 | |
| href="http://llvm.org">LLVM web page</a>, in particular in the <a
 | |
| href="http://llvm.org/docs/">documentation</a> section.  The web page also
 | |
| contains versions of the API documentation which is up-to-date with the
 | |
| Subversion version of the source code.
 | |
| You can access versions of these documents specific to this release by going
 | |
| into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
 | |
| 
 | |
| <p>If you have any questions or comments about LLVM, please feel free to contact
 | |
| us via the <a href="http://llvm.org/docs/#maillist"> mailing
 | |
| lists</a>.</p>
 | |
| 
 | |
| </div>
 | |
| 
 | |
| <!-- *********************************************************************** -->
 | |
| 
 | |
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