forked from OSchip/llvm-project
1339 lines
55 KiB
HTML
1339 lines
55 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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<div class="doc_title">LLVM 2.6 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="#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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<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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<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 2.6. 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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<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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</div>
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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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<!-- 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?
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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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2.7 eliminates ADT/iterator.h
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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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<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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<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), the Clang repository and the llvm-gcc repository. In
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addition to this code, the LLVM Project includes other sub-projects that are in
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development. Here we include updates on these subprojects.
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</p>
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</div>
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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>
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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
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a set of new 'LLVM native' front-end technologies for the C family of languages.
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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 <a
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href="http://clang.llvm.org/performance.html">fast compiles</a> and
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<a href="http://clang.llvm.org/diagnostics.html">good diagnostics</a>, we
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encourage you to try it out. Clang currently compiles typical Objective-C code
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3x faster than GCC and compiles C code about 30% faster than GCC at -O0 -g
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(which is when the most pressure is on the frontend).</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
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Clang is able to parse the libstdc++ 4.2 headers and even codegen simple apps.
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If you are interested in Clang C++ support or any other Clang feature, we
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strongly encourage you to get involved on the <a
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href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
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list</a>.</p>
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<p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
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<ul>
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<li>C and Objective-C support are now considered production quality.</li>
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<li>AuroraUX, FreeBSD and OpenBSD are now supported.</li>
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<li>Most of Objective-C 2.0 is now supported with the GNU runtime.</li>
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<li>Many many bugs are fixed and lots of features have been added.</li>
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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="clangsa">Clang Static Analyzer</a>
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</div>
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<div class="doc_text">
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<p>Previously announced in the 2.4 and 2.5 LLVM releases, the Clang project also
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includes an early stage static source code analysis tool for <a
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href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
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in C and Objective-C programs. The tool performs checks to find
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bugs that occur on a specific path within a program.</p>
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<p>In the LLVM 2.6 time-frame, the analyzer core has undergone several important
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improvements and cleanups and now includes a new <em>Checker</em> interface that
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is intended to eventually serve as a basis for domain-specific checks. Further,
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in addition to generating HTML files for reporting analysis results, the
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analyzer can now also emit bug reports in a structured XML format that is
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intended to be easily readable by other programs.</p>
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<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
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and deeper checks such as buffer overrun detection. There are many opportunities
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to extend and enhance the static analyzer, and anyone interested in working on
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this project is encouraged to get involved!</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
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</div>
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<div class="doc_text">
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<p>
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The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
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a JVM and a CLI Virtual Machine (Microsoft .NET is an
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implementation of the CLI) using LLVM for static and just-in-time
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compilation.</p>
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<p>
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VMKit version 0.26 builds with LLVM 2.6 and you can find it on its
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<a href="http://vmkit.llvm.org/releases/">web page</a>. The release includes
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bug fixes, cleanup and new features. The major changes are:</p>
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<ul>
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<li>A new llcj tool to generate shared libraries or executables of Java
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files.</li>
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<li>Cooperative garbage collection. </li>
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<li>Fast subtype checking (paper from Click et al [JGI'02]). </li>
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<li>Implementation of a two-word header for Java objects instead of the original
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three-word header. </li>
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<li>Better Java specification-compliance: division by zero checks, stack
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overflow checks, finalization and references support. </li>
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</ul>
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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="compiler-rt">compiler-rt: Compiler Runtime Library</a>
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</div>
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<div class="doc_text">
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<p>
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The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
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is a simple library that provides an implementation of the low-level
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target-specific hooks required by code generation and other runtime components.
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For example, when compiling for a 32-bit target, converting a double to a 64-bit
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unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
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function. The compiler-rt library provides highly optimized implementations of
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this and other low-level routines (some are 3x faster than the equivalent
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libgcc routines).</p>
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<p>
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All of the code in the compiler-rt project is available under the standard LLVM
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License, a "BSD-style" license.</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="klee">KLEE: Symbolic Execution and Automatic Test Case Generator</a>
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</div>
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<div class="doc_text">
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<p>
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The new LLVM <a href="http://klee.llvm.org/">KLEE project</a> is a symbolic
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execution framework for programs in LLVM bitcode form. KLEE tries to
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symbolically evaluate "all" paths through the application and records state
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transitions that lead to fault states. This allows it to construct testcases
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that lead to faults and can even be used to verify algorithms. For more
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details, please see the <a
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href="http://llvm.org/pubs/2008-12-OSDI-KLEE.html">OSDI 2008 paper</a> about
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KLEE.</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
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</div>
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<div class="doc_text">
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<p>
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The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
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gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
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<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (llvm.so)
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that is loaded by gcc at runtime. It uses the new gcc plugin architecture to
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disable the GCC optimizers and code generators, and schedule the LLVM optimizers
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and code generators (or direct output of LLVM IR) instead. Currently only Linux
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and Darwin are supported, and only on x86-32 and x86-64. It should be easy to
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add additional unix-like architectures and other processor families. In theory
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it should be possible to use <a href="http://dragonegg.llvm.org/">DragonEgg</a>
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with any language supported by gcc, however only C and Fortran work well for the
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moment. Ada and C++ work to some extent, while Java, Obj-C and Obj-C++ are so
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far entirely untested. Since gcc-4.5 has not yet been released, neither has
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<a href="http://dragonegg.llvm.org/">DragonEgg</a>. To build
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<a href="http://dragonegg.llvm.org/">DragonEgg</a> you will need to check out the
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development versions of <a href="http://gcc.gnu.org/svn.html/"> gcc</a>,
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<a href="http://llvm.org/docs/GettingStarted.html#checkout">llvm</a> and
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<a href="http://dragonegg.llvm.org/">DragonEgg</a> from their respective
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subversion repositories, and follow the instructions in the
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<a href="http://dragonegg.llvm.org/">DragonEgg</a> README.
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</p>
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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="mc">llvm-mc: Machine Code Toolkit</a>
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</div>
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<div class="doc_text">
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<p>
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The LLVM Machine Code (MC) Toolkit project is a (very early) effort to build
|
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better tools for dealing with machine code, object file formats, etc. The idea
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is to be able to generate most of the target specific details of assemblers and
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disassemblers from existing LLVM target .td files (with suitable enhancements),
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and to build infrastructure for reading and writing common object file formats.
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One of the first deliverables is to build a full assembler and integrate it into
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the compiler, which is predicted to substantially reduce compile time in some
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scenarios.
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</p>
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<p>In the LLVM 2.6 timeframe, the MC framework has grown to the point where it
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can reliably parse and pretty print (with some encoding information) a
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darwin/x86 .s file successfully, and has the very early phases of a Mach-O
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assembler in progress. Beyond the MC framework itself, major refactoring of the
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LLVM code generator has started. The idea is to make the code generator reason
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about the code it is producing in a much more semantic way, rather than a
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textual way. For example, the code generator now uses MCSection objects to
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represent section assignments, instead of text strings that print to .section
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directives.</p>
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<p>MC is an early and ongoing project that will hopefully continue to lead to
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many improvements in the code generator and build infrastructure useful for many
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other situations.
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</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="externalproj">External Projects Using LLVM 2.6</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>An exciting aspect of LLVM is that it is used as an enabling technology for
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a lot of other language and tools projects. This section lists some of the
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projects that have already been updated to work with LLVM 2.6.</p>
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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="Rubinius">Rubinius</a>
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</div>
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<div class="doc_text">
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<p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
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for running Ruby code which strives to write as much of the core class
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implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
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uses LLVM to optimize and compile ruby code down to machine code. Techniques
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such as type feedback, method inlining, and uncommon traps are all used to
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remove dynamism from ruby execution and increase performance.</p>
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<p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
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a counter based JIT, type feedback and speculative method inlining.
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</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="macruby">MacRuby</a>
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</div>
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<div class="doc_text">
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<p>
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<a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
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core Mac OS X technologies, such as the Objective-C common runtime and garbage
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collector and the CoreFoundation framework. It is principally developed by
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Apple and aims at enabling the creation of full-fledged Mac OS X applications.
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</p>
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<p>
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MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
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expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
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handling.</p>
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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="pure">Pure</a>
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</div>
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<div class="doc_text">
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<p>
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<a href="http://pure-lang.googlecode.com/">Pure</a>
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is an algebraic/functional programming language based on term rewriting.
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Programs are collections of equations which are used to evaluate expressions in
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a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
|
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lexical closures, a hygienic macro system (also based on term rewriting),
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built-in list and matrix support (including list and matrix comprehensions) and
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an easy-to-use C interface. The interpreter uses LLVM as a backend to
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JIT-compile Pure programs to fast native code.</p>
|
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<p>Pure versions 0.31 and later have been tested and are known to work with
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LLVM 2.6 (and continue to work with older LLVM releases >= 2.3 as well).
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</p>
|
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</div>
|
|
|
|
|
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<!--=========================================================================-->
|
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<div class="doc_subsection">
|
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<a name="ldc">LLVM D Compiler</a>
|
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</div>
|
|
|
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<div class="doc_text">
|
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<p>
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<a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
|
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the D Programming Language using the LLVM optimizer and code generator.
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The LDC project works great with the LLVM 2.6 release. General improvements in
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|
this
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cycle have included new inline asm constraint handling, better debug info
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|
support, general bug fixes and better x86-64 support. This has allowed
|
|
some major improvements in LDC, getting it 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>
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<a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
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|
source implementation of the PHP programming
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|
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>
|
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</div>
|
|
|
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<!--=========================================================================-->
|
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<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>
|
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<a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
|
|
and static compiling support to the Lua VM. Lua bytecode is analyzed to
|
|
remove type checks, then LLVM is used to compile the bytecode down to machine
|
|
code.</p>
|
|
</div>
|
|
|
|
|
|
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<!-- *********************************************************************** -->
|
|
<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>
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<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. Please see the <a href="ProgrammersManual.html#threading">LLVM
|
|
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.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="coreimprovements">LLVM IR and Core Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>LLVM IR has several new features for better support of new targets and that
|
|
expose new optimization opportunities:</p>
|
|
|
|
<ul>
|
|
<li>The <a href="LangRef.html#i_add">add</a>, <a
|
|
href="LangRef.html#i_sub">sub</a> and <a href="LangRef.html#i_mul">mul</a>
|
|
instructions have been split into integer and floating point versions (like
|
|
divide and remainder), introducing new <a
|
|
href="LangRef.html#i_fadd">fadd</a>, <a href="LangRef.html#i_fsub">fsub</a>,
|
|
and <a href="LangRef.html#i_fmul">fmul</a> instructions.</li>
|
|
<li>The <a href="LangRef.html#i_add">add</a>, <a
|
|
href="LangRef.html#i_sub">sub</a> and <a href="LangRef.html#i_mul">mul</a>
|
|
instructions now support optional "nsw" and "nuw" bits which indicate that
|
|
the operation is guaranteed to not overflow (in the signed or
|
|
unsigned case, respectively). This gives the optimizer more information and
|
|
can be used for things like C signed integer values, which are undefined on
|
|
overflow.</li>
|
|
<li>The <a href="LangRef.html#i_sdiv">sdiv</a> instruction now supports an
|
|
optional "exact" flag which indicates that the result of the division is
|
|
guaranteed to have a remainder of zero. This is useful for optimizing pointer
|
|
subtraction in C.</li>
|
|
<li>The <a href="LangRef.html#i_getelementptr">getelementptr</a> instruction now
|
|
supports arbitrary integer index values for array/pointer indices. This
|
|
allows for better code generation on 16-bit pointer targets like PIC16.</li>
|
|
<li>The <a href="LangRef.html#i_getelementptr">getelementptr</a> instruction now
|
|
supports an "inbounds" optimization hint that tells the optimizer that the
|
|
pointer is guaranteed to be within its allocated object.</li>
|
|
<li>LLVM now support a series of new linkage types for global values which allow
|
|
for better optimization and new capabilities:
|
|
<ul>
|
|
<li><a href="LangRef.html#linkage_linkonce">linkonce_odr</a> and
|
|
<a href="LangRef.html#linkage_weak">weak_odr</a> have the same linkage
|
|
semantics as the non-"odr" linkage types. The difference is that these
|
|
linkage types indicate that all definitions of the specified function
|
|
are guaranteed to have the same semantics. This allows inlining
|
|
templates functions in C++ but not inlining weak functions in C,
|
|
which previously both got the same linkage type.</li>
|
|
<li><a href="LangRef.html#linkage_available_externally">available_externally
|
|
</a> is a new linkage type that gives the optimizer visibility into the
|
|
definition of a function (allowing inlining and side effect analysis)
|
|
but that does not cause code to be generated. This allows better
|
|
optimization of "GNU inline" functions, extern templates, etc.</li>
|
|
<li><a href="LangRef.html#linkage_linker_private">linker_private</a> is a
|
|
new linkage type (which is only useful on Mac OS X) that is used for
|
|
some metadata generation and other obscure things.</li>
|
|
</ul></li>
|
|
<li>Finally, target-specific intrinsics can now return multiple values, which
|
|
is useful for modeling target operations with 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 minor performance tweaks and bug fixes, this
|
|
release includes a few major enhancements and additions to the optimizers:</p>
|
|
|
|
<ul>
|
|
|
|
<li>The <a href="Passes.html#scalarrepl">Scalar Replacement of Aggregates</a>
|
|
pass has many improvements that allow it to better promote vector unions,
|
|
variables which are memset, and much more strange code that can happen to
|
|
do bitfield accesses to register operations. An interesting change is that
|
|
it now produces "unusual" integer sizes (like i1704) in some cases and lets
|
|
other optimizers clean things up.</li>
|
|
<li>The <a href="Passes.html#loop-reduce">Loop Strength Reduction</a> pass now
|
|
promotes small integer induction variables to 64-bit on 64-bit targets,
|
|
which provides a major performance boost for much numerical code. It also
|
|
promotes shorts to int on 32-bit hosts, etc. LSR now also analyzes pointer
|
|
expressions (e.g. getelementptrs), as well as integers.</li>
|
|
<li>The <a href="Passes.html#gvn">GVN</a> pass now eliminates partial
|
|
redundancies of loads in simple cases.</li>
|
|
<li>The <a href="Passes.html#inline">Inliner</a> now reuses stack space when
|
|
inlining similar arrays from multiple callees into one caller.</li>
|
|
<li>LLVM includes a new experimental Static Single Information (SSI)
|
|
construction pass.</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="executionengine">Interpreter and JIT Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>LLVM has a new "EngineBuilder" class which makes it more obvious how to
|
|
set up and configure an ExecutionEngine (a JIT or interpreter).</li>
|
|
<li>The JIT now supports generating more than 16M of code.</li>
|
|
<li>When configured with <tt>--with-oprofile</tt>, 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="codegen">Target Independent Code Generator Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>We have put a significant amount of work into the code generator
|
|
infrastructure, which allows us to implement more aggressive algorithms and make
|
|
it run faster:</p>
|
|
|
|
<ul>
|
|
|
|
<li>The <tt>llc -asm-verbose</tt> option (exposed from llvm-gcc as <tt>-dA</tt>
|
|
and clang as <tt>-fverbose-asm</tt> or <tt>-dA</tt>) now adds a lot of
|
|
useful information in comments to
|
|
the generated .s file. This information includes location information (if
|
|
built with <tt>-g</tt>) and loop nest information.</li>
|
|
<li>The code generator now supports a new MachineVerifier pass which is useful
|
|
for finding bugs in targets and codegen passes.</li>
|
|
<li>The Machine LICM is now enabled by default. It hoists instructions out of
|
|
loops (such as constant pool loads, loads from read-only stubs, vector
|
|
constant synthesization code, etc.) and is currently configured to only do
|
|
so when the hoisted operation can be rematerialized.</li>
|
|
<li>The Machine Sinking pass is now enabled by default. This pass moves
|
|
side-effect free operations down the CFG so that they are executed on fewer
|
|
paths through a function.</li>
|
|
<li>The code generator now performs "stack slot coloring" of register spills,
|
|
which allows spill slots to be reused. This leads to smaller stack frames
|
|
in cases where there are lots of register spills.</li>
|
|
<li>The register allocator has many improvements to take better advantage of
|
|
commutable operations, various spiller peephole optimizations, and can now
|
|
coalesce cross-register-class copies.</li>
|
|
<li>Tblgen now supports multiclass inheritance and a number of new string and
|
|
list operations like <tt>!(subst)</tt>, <tt>!(foreach)</tt>, <tt>!car</tt>,
|
|
<tt>!cdr</tt>, <tt>!null</tt>, <tt>!if</tt>, <tt>!cast</tt>.
|
|
These make the .td files more expressive and allow more aggressive factoring
|
|
of duplication across instruction patterns.</li>
|
|
<li>Target-specific intrinsics can now be added without having to hack VMCore to
|
|
add them. This makes it easier to maintain out-of-tree targets.</li>
|
|
<li>The instruction selector is better at propagating information about values
|
|
(such as whether they are sign/zero extended etc.) across basic block
|
|
boundaries.</li>
|
|
<li>The SelectionDAG datastructure has new nodes for representing buildvector
|
|
and <a href="http://llvm.org/PR2957">vector shuffle</a> operations. This
|
|
makes operations and pattern matching more efficient and easier to get
|
|
right.</li>
|
|
<li>The Prolog/Epilog Insertion Pass now has experimental support for performing
|
|
the "shrink wrapping" optimization, which moves spills and reloads around in
|
|
the CFG to avoid doing saves on paths that don't need them.</li>
|
|
<li>LLVM includes new 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
|
|
<tt>MachineRegisterInfo::setRegAllocationHint</tt>. A regalloc hint consists
|
|
of hint type and physical register number. A hint type of zero specifies a
|
|
register allocation preference. Other hint type values are target specific
|
|
which are resolved by <tt>TargetRegisterInfo::ResolveRegAllocHint</tt>. An
|
|
example is the ARM target which uses register hints to request that the
|
|
register allocator provide an even / odd register pair to two virtual
|
|
registers.</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>SSE 4.2 builtins are now supported.</li>
|
|
<li>GCC-compatible soft float modes are now supported, which are typically used
|
|
by OS kernels.</li>
|
|
<li>X86-64 now models implicit zero extensions better, which allows the code
|
|
generator to remove a lot of redundant zexts. It also models the 8-bit "H"
|
|
registers as subregs, which allows them to be used in some tricky
|
|
situations.</li>
|
|
<li>X86-64 now supports the "local exec" and "initial exec" thread local storage
|
|
model.</li>
|
|
<li>The vector forms of the <a href="LangRef.html#i_icmp">icmp</a> and <a
|
|
href="LangRef.html#i_fcmp">fcmp</a> instructions now select to efficient
|
|
SSE operations.</li>
|
|
<li>Support for the win64 calling conventions have improved. The primary
|
|
missing feature is support for varargs function definitions. It seems to
|
|
work well for many win64 JIT purposes.</li>
|
|
<li>The X86 backend has preliminary support for <a
|
|
href="CodeGenerator.html#x86_memory">mapping address spaces to segment
|
|
register references</a>. This allows you to write GS or FS relative memory
|
|
accesses directly in LLVM IR for cases where you know exactly what you're
|
|
doing (such as in an OS kernel). There are some known problems with this
|
|
support, but it works in simple cases.</li>
|
|
<li>The X86 code generator has been refactored to move all global variable
|
|
reference logic to one place
|
|
(<tt>X86Subtarget::ClassifyGlobalReference</tt>) which
|
|
makes it easier to reason about.</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.</li>
|
|
|
|
<li>The AAPCS-VFP "hard float" calling conventions are also supported with the
|
|
<tt>-float-abi=hard</tt> flag.</li>
|
|
|
|
<li>The ARM calling convention code is now tblgen generated instead of resorting
|
|
to C++ code.</li>
|
|
|
|
<p>These features are still somewhat experimental
|
|
and subject to change. The Neon intrinsics, in particular, may change in future
|
|
releases of LLVM. ARMv7 support has progressed a lot on top of tree since 2.6
|
|
branched.</p>
|
|
|
|
</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="newapis">New Useful APIs</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>This release includes a number of new APIs that are used internally, which
|
|
may also be useful for external clients.
|
|
</p>
|
|
|
|
<ul>
|
|
<li>New <a href="http://llvm.org/doxygen/PrettyStackTrace_8h-source.html">
|
|
<tt>PrettyStackTrace</tt> class</a> allows crashes of llvm tools (and applications
|
|
that integrate them) to provide more detailed indication of what the
|
|
compiler was doing at the time of the crash (e.g. running a pass).
|
|
At the top level for each LLVM tool, it includes the command line arguments.
|
|
</li>
|
|
<li>New <a href="http://llvm.org/doxygen/StringRef_8h-source.html">StringRef</a>
|
|
and <a href="http://llvm.org/doxygen/Twine_8h-source.html">Twine</a> classes
|
|
make operations on character ranges and
|
|
string concatenation to be more efficient. <tt>StringRef</tt> is just a <tt>const
|
|
char*</tt> with a length, <tt>Twine</tt> is a light-weight rope.</li>
|
|
<li>LLVM has new <tt>WeakVH</tt>, <tt>AssertingVH</tt> and <tt>CallbackVH</tt>
|
|
classes, which make it easier to write LLVM IR transformations. <tt>WeakVH</tt>
|
|
is automatically drops to null when the referenced <tt>Value</tt> is deleted,
|
|
and is updated across a <tt>replaceAllUsesWith</tt> operation.
|
|
<tt>AssertingVH</tt> aborts the program if the
|
|
referenced value is destroyed while it is being referenced. <tt>CallbackVH</tt>
|
|
is a customizable class for handling value references. See <a
|
|
href="http://llvm.org/doxygen/ValueHandle_8h-source.html">ValueHandle.h</a>
|
|
for more information.</li>
|
|
<li>The new '<a href="http://llvm.org/doxygen/Triple_8h-source.html">Triple
|
|
</a>' class centralizes a lot of logic that reasons about target
|
|
triples.</li>
|
|
<li>The new '<a href="http://llvm.org/doxygen/ErrorHandling_8h-source.html">
|
|
llvm_report_error()</a>' set of APIs allows tools to embed the LLVM
|
|
optimizer and backend and recover from previously unrecoverable errors.</li>
|
|
<li>LLVM has new abstractions for <a
|
|
href="http://llvm.org/doxygen/Atomic_8h-source.html">atomic operations</a>
|
|
and <a href="http://llvm.org/doxygen/RWMutex_8h-source.html">reader/writer
|
|
locks</a>.</li>
|
|
<li>LLVM has new <a href="http://llvm.org/doxygen/SourceMgr_8h-source.html">
|
|
<tt>SourceMgr</tt> and <tt>SMLoc</tt> classes</a> which implement caret
|
|
diagnostics and basic include stack processing for simple parsers. It is
|
|
used by tablegen, llvm-mc, the .ll parser and FileCheck.</li>
|
|
</ul>
|
|
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="otherimprovements">Other Improvements and New Features</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>Other miscellaneous features include:</p>
|
|
|
|
<ul>
|
|
<li>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>The C bindings (in the llvm/include/llvm-c directory) include many newly
|
|
supported APIs.</li>
|
|
<li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005
|
|
programming language.</li>
|
|
|
|
<li>The LLVMC driver has several new features:
|
|
<ul>
|
|
<li>Dynamic plugins now work on Windows.</li>
|
|
<li>New option property: init. Makes possible to provide default values for
|
|
options defined in plugins (interface to <tt>cl::init</tt>).</li>
|
|
<li>New example: Skeleton, shows how to create a standalone LLVMC-based
|
|
driver.</li>
|
|
<li>New example: mcc16, a driver for the PIC16 toolchain.</li>
|
|
</ul>
|
|
</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 actively supported
|
|
and had bitrotted.</li>
|
|
<li>The BigBlock register allocator has been removed, it had also bitrotted.</li>
|
|
<li>The C Backend (<tt>-march=c</tt>) 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>
|
|
|
|
<li>All LLVM tools now default to overwriting their output file, behaving more
|
|
like standard unix tools. Previously, this only happened with the '<tt>-f</tt>'
|
|
option.</li>
|
|
<li>LLVM build now builds all libraries as .a files instead of some
|
|
libraries as relinked .o files. This requires some APIs like
|
|
InitializeAllTargets.h.
|
|
</li>
|
|
</ul>
|
|
|
|
|
|
<p>In addition, many APIs have changed in this release. Some of the major LLVM
|
|
API changes are:</p>
|
|
|
|
<ul>
|
|
<li>All uses of <tt>hash_set</tt> and <tt>hash_map</tt> have been removed from
|
|
the LLVM tree and the wrapper headers have been removed.</li>
|
|
<li>The llvm/Streams.h and <tt>DOUT</tt> member of Debug.h have been removed. The
|
|
<tt>llvm::Ostream</tt> class has been completely removed and replaced with
|
|
uses of <tt>raw_ostream</tt>.</li>
|
|
<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 <tt>DynamicLibrary</tt> 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 contains embedded null characters.</li>
|
|
|
|
<li>If you were using <tt>operator +</tt> on the result of <tt>getName()</tt> and
|
|
treating the result as an <tt>std::string</tt>, you can either
|
|
use <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 <tt>TargetMachineRegistry</tt>). 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>
|
|
</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>The llvm-gcc bootstrap will fail with some versions of binutils (e.g. 2.15)
|
|
with a message of "<tt><a href="http://llvm.org/PR5004">Error: can not do 8
|
|
byte pc-relative relocation</a></tt>" when building C++ code. We intend to
|
|
fix this on mainline, but a workaround for 2.6 is to upgrade to binutils
|
|
2.17 or later.</li>
|
|
|
|
<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/x86-64 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, PIC16, Blackfin, MSP430 and SystemZ backends are
|
|
experimental.</li>
|
|
<li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
|
|
supported value for this option. The ELF writer is experimental.</li>
|
|
<li>The implementation of Andersen's Alias Analysis has many known bugs.</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>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>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 <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
|
|
tools/gfortran component for details.</li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
|
|
technology, and problems should be expected.
|
|
<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 <tt>--disable-bootstrap</tt>.</li>
|
|
<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
|
|
and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
|
|
(c380004 also fails with gcc-4.2 mainline).
|
|
If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
|
|
causes the compiler to go into an infinite loop, using up all system memory.</li>
|
|
<li>Some GCC specific Ada tests continue to crash the compiler.</li>
|
|
<li>The <tt>-E</tt> binder option (exception backtraces)
|
|
<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
|
|
crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
|
|
<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
|
|
or finish at a non-byte offset</a> in a record. Workaround: do not pack records
|
|
or use representation clauses that result in a field of a non-discrete type
|
|
starting or finishing in the middle of a byte.</li>
|
|
<li>The <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-bindings">Known problems with the O'Caml bindings</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
|
|
<tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
|
|
<tt>Llvm.Linkage.Link_once</tt> 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>
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
<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-blue" alt="Valid CSS"></a>
|
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<a href="http://validator.w3.org/check/referer"><img
|
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src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
|
|
|
|
<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
|
|
Last modified: $Date$
|
|
</address>
|
|
|
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</body>
|
|
</html>
|