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1238 lines
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HTML
1238 lines
49 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 2.8 Release Notes</title>
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</head>
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<body>
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<div class="doc_title">LLVM 2.8 Release Notes</div>
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<img align=right src="http://llvm.org/img/DragonSmall.png"
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width="136" height="136" alt="LLVM Dragon Logo">
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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 2.8</a></li>
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<li><a href="#whatsnew">What's New in LLVM 2.8?</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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<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
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release.<br>
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You may prefer the
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<a href="http://llvm.org/releases/2.7/docs/ReleaseNotes.html">LLVM 2.7
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Release Notes</a>.</h1>
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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 2.8. 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://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
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Mailing List</a> is a good place to send them.</p>
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<p>Note that if you are reading this file from a Subversion checkout or the
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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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ABCD, GEPSplitterPass
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MSIL backend?
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lib/Transforms/Utils/SSI.cpp -> ABCD depends on it.
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-->
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<!-- Features that need text if they're finished for 2.8:
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combiner-aa?
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strong phi elim
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llvm.dbg.value: variable debug info for optimized code
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loop dependence analysis
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-->
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<!-- for announcement email:
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Logo web page.
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Many new papers added to /pubs/
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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 2.8 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><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
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C++, and Objective-C languages. Clang aims to provide a better user experience
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through expressive diagnostics, a high level of conformance to language
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standards, fast compilation, and low memory use. Like LLVM, Clang provides a
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modular, library-based architecture that makes it suitable for creating or
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integrating with other development tools. Clang is considered a
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production-quality compiler for C and Objective-C on x86 (32- and 64-bit).</p>
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<p>In the LLVM 2.7 time-frame, the Clang team has made many improvements:</p>
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<ul>
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<li>C++ Support: Clang is now capable of self-hosting! While still
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alpha-quality, Clang's C++ support has matured enough to build LLVM and Clang,
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and C++ is now enabled by default. See the <a
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href="http://clang.llvm.org/cxx_compatibility.html">Clang C++ compatibility
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page</a> for common C++ migration issues.</li>
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<li>Objective-C: Clang now includes experimental support for an updated
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Objective-C ABI on non-Darwin platforms. This includes support for non-fragile
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instance variables and accelerated proxies, as well as greater potential for
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|
future optimisations. The new ABI is used when compiling with the
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-fobjc-nonfragile-abi and -fgnu-runtime options. Code compiled with these
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options may be mixed with code compiled with GCC or clang using the old GNU ABI,
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but requires the libobjc2 runtime from the GNUstep project.</li>
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<li>New warnings: Clang contains a number of new warnings, including
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control-flow warnings (unreachable code, missing return statements in a
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non-<code>void</code> function, etc.), sign-comparison warnings, and improved
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format-string warnings.</li>
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<li>CIndex API and Python bindings: Clang now includes a C API as part of the
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CIndex library. Although we may make some changes to the API in the future, it
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is intended to be stable and has been designed for use by external projects. See
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the Clang
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doxygen <a href="http://clang.llvm.org/doxygen/group__CINDEX.html">CIndex</a>
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documentation for more details. The CIndex API also includes a preliminary
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set of Python bindings.</li>
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<li>ARM Support: Clang now has ABI support for both the Darwin and Linux ARM
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|
ABIs. Coupled with many improvements to the LLVM ARM backend, Clang is now
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suitable for use as a beta quality ARM compiler.</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="clangsa">Clang Static Analyzer</a>
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</div>
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<div class="doc_text">
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<p>The <a href="http://clang-analyzer.llvm.org/">Clang Static Analyzer</a>
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|
project is an effort to use static source code analysis techniques to
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automatically find bugs in C and Objective-C programs (and hopefully <a
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href="http://clang-analyzer.llvm.org/dev_cxx.html">C++ in the
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future</a>!). The tool is very good at finding bugs that occur on specific
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paths through code, such as on error conditions.</p>
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<p>In the LLVM 2.7 time-frame, the analyzer core has made several major and
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minor improvements, including better support for tracking the fields of
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structures, initial support (not enabled by default yet) for doing
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interprocedural (cross-function) analysis, and new checks have been added.
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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="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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With the release of LLVM 2.7, VMKit has shifted to a great framework for writing
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virtual machines. VMKit now offers precise and efficient garbage collection with
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multi-threading support, thanks to the MMTk memory management toolkit, as well
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as just in time and ahead of time compilation with LLVM. The major changes in
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VMKit 0.27 are:</p>
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<ul>
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<li>Garbage collection: VMKit now uses the MMTk toolkit for garbage collectors.
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The first collector to be ported is the MarkSweep collector, which is precise,
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and drastically improves the performance of VMKit.</li>
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<li>Line number information in the JVM: by using the debug metadata of LLVM, the
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JVM now supports precise line number information, useful when printing a stack
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trace.</li>
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<li>Interface calls in the JVM: we implemented a variant of the Interface Method
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|
Table technique for interface calls in the JVM.
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</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
|
|
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
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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. New in LLVM 2.7: compiler_rt now
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supports ARM targets.</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
|
|
<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</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://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
|
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gcc-4.5. Unlike llvm-gcc, which makes many intrusive changes to the underlying
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gcc-4.2 code, dragonegg in theory does not require any gcc-4.5 modifications
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whatsoever (currently one small patch is needed). This is thanks to the new
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<a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>, which
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makes it possible to modify the behaviour of gcc at runtime by loading a plugin,
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|
which is nothing more than a dynamic library which conforms to the gcc plugin
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|
interface. DragonEgg is a gcc plugin that causes the LLVM optimizers to be run
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instead of the gcc optimizers, and the LLVM code generators instead of the gcc
|
|
code generators, just like llvm-gcc. To use it, you add
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"-fplugin=path/dragonegg.so" to the gcc-4.5 command line, and gcc-4.5 magically
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becomes llvm-gcc-4.5!
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|
</p>
|
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|
|
<p>
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DragonEgg is still a work in progress. Currently C works very well, while C++,
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Ada and Fortran work fairly well. All other languages either don't work at all,
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|
or only work poorly. For the moment only the x86-32 and x86-64 targets are
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supported, and only on linux and darwin (darwin needs an additional gcc patch).
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</p>
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<p>
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DragonEgg is a new project which is seeing its first release with llvm-2.7.
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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="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 (aka MC) sub-project of LLVM was created to solve a number
|
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of problems in the realm of assembly, disassembly, object file format handling,
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and a number of other related areas that CPU instruction-set level tools work
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in. It is a sub-project of LLVM which provides it with a number of advantages
|
|
over other compilers that do not have tightly integrated assembly-level tools.
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|
For a gentle introduction, please see the <a
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href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
|
|
LLVM MC Project Blog Post</a>.
|
|
</p>
|
|
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|
<p>2.7 includes major parts of the work required by the new MC Project. A few
|
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targets have been refactored to support it, and work is underway to support a
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native assembler in LLVM. This work is not complete in LLVM 2.7, but it has
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made substantially more progress on LLVM mainline.</p>
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<p>One minor example of what MC can do is to transcode an AT&T syntax
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X86 .s file into intel syntax. You can do this with something like:</p>
|
|
<pre>
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llvm-mc foo.s -output-asm-variant=1 -o foo-intel.s
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</pre>
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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 Open Source Projects Using LLVM 2.7</a>
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|
</div>
|
|
<!-- *********************************************************************** -->
|
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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 2.7.</p>
|
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</div>
|
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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>
|
|
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),
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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 0.43 and later have been tested and are known to work with
|
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LLVM 2.7 (and continue to work with older LLVM releases >= 2.5).</p>
|
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|
|
</div>
|
|
|
|
<!--=========================================================================-->
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<div class="doc_subsection">
|
|
<a name="RoadsendPHP">Roadsend PHP</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://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.
|
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</p>
|
|
</div>
|
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|
|
<!--=========================================================================-->
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<div class="doc_subsection">
|
|
<a name="tce">TTA-based Codesign Environment (TCE)</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
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|
<a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing
|
|
application-specific processors (ASP) based on the Transport triggered
|
|
architecture (TTA). The toolset provides a complete co-design flow from C/C++
|
|
programs down to synthesizable VHDL and parallel program binaries. Processor
|
|
customization points include the register files, function units, supported
|
|
operations, and the interconnection network.</p>
|
|
|
|
<p>TCE uses llvm-gcc/Clang and LLVM for C/C++ language support, target
|
|
independent optimizations and also for parts of code generation. It generates
|
|
new LLVM-based code generators "on the fly" for the designed TTA processors and
|
|
loads them in to the compiler backend as runtime libraries to avoid per-target
|
|
recompilation of larger parts of the compiler chain.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="safecode">SAFECode Compiler</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://safecode.cs.illinois.edu">SAFECode</a> is a memory safe C
|
|
compiler built using LLVM. It takes standard, unannotated C code, analyzes the
|
|
code to ensure that memory accesses and array indexing operations are safe, and
|
|
instruments the code with run-time checks when safety cannot be proven
|
|
statically.
|
|
</p>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="icedtea">IcedTea Java Virtual Machine Implementation</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
|
|
harness to build OpenJDK using only free software build tools and to provide
|
|
replacements for the not-yet free parts of OpenJDK. One of the extensions that
|
|
IcedTea provides is a new JIT compiler named <a
|
|
href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
|
|
to provide native code generation without introducing processor-dependent
|
|
code.
|
|
</p>
|
|
<p>Icedtea6 1.8 and later have been tested and are known to work with
|
|
LLVM 2.7 (and continue to work with older LLVM releases >= 2.6 as well).
|
|
</p>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="llvm-lua">LLVM-Lua</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM
|
|
to add JIT and static compiling support to the Lua VM. Lua
|
|
bytecode is analyzed to remove type checks, then LLVM is used to compile the
|
|
bytecode down to machine code.
|
|
</p>
|
|
<p>LLVM-Lua 1.2.0 have been tested and is known to work with LLVM 2.7.
|
|
</p>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="MacRuby">MacRuby</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://macruby.org">MacRuby</a> is an implementation of Ruby based on
|
|
core Mac OS technologies, sponsored by Apple Inc. It uses LLVM at runtime for
|
|
optimization passes, JIT compilation and exception handling. It also allows
|
|
static (ahead-of-time) compilation of Ruby code straight to machine code.
|
|
</p>
|
|
<p>The upcoming MacRuby 0.6 release works with LLVM 2.7.
|
|
</p>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="GHC">Glasgow Haskell Compiler (GHC)</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://www.haskell.org/ghc/">GHC</a> is an open source,
|
|
state-of-the-art programming suite for Haskell, a standard lazy
|
|
functional programming language. It includes an optimizing static
|
|
compiler generating good code for a variety of platforms, together
|
|
with an interactive system for convenient, quick development.</p>
|
|
|
|
<p>In addition to the existing C and native code generators, GHC now
|
|
supports an <a
|
|
href="http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/Backends/LLVM">LLVM
|
|
code generator</a>. GHC supports LLVM 2.7.</p>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="whatsnew">What's New in LLVM 2.7?</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<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="orgchanges">LLVM Community Changes</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>In addition to changes to the code, between LLVM 2.6 and 2.7, a number of
|
|
organization changes have happened:
|
|
</p>
|
|
|
|
<ul>
|
|
<li>LLVM has a new <a href="http://llvm.org/Logo.html">official logo</a>!</li>
|
|
|
|
<li>Ted Kremenek and Doug Gregor have stepped forward as <a
|
|
href="http://llvm.org/docs/DeveloperPolicy.html#owners">Code Owners</a> of the
|
|
Clang static analyzer and the Clang frontend, respectively.</li>
|
|
|
|
<li>LLVM now has an <a href="http://blog.llvm.org">official Blog</a> at
|
|
<a href="http://blog.llvm.org">http://blog.llvm.org</a>. This is a great way
|
|
to learn about new LLVM-related features as they are implemented. Several
|
|
features in this release are already explained on the blog.</li>
|
|
|
|
<li>The LLVM web pages are now checked into the SVN server, in the "www",
|
|
"www-pubs" and "www-releases" SVN modules. Previously they were hidden in a
|
|
largely inaccessible old CVS server.</li>
|
|
|
|
<li><a href="http://llvm.org">llvm.org</a> is now hosted on a new (and much
|
|
faster) server. It is still graciously hosted at the University of Illinois
|
|
of Urbana Champaign.</li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="majorfeatures">Major New Features</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM 2.7 includes several major new capabilities:</p>
|
|
|
|
<ul>
|
|
<li>2.7 includes initial support for the <a
|
|
href="http://en.wikipedia.org/wiki/MicroBlaze">MicroBlaze</a> target.
|
|
MicroBlaze is a soft processor core designed for Xilinx FPGAs.</li>
|
|
|
|
<li>2.7 includes a new LLVM IR "extensible metadata" feature. This feature
|
|
supports many different use cases, including allowing front-end authors to
|
|
encode source level information into LLVM IR, which is consumed by later
|
|
language-specific passes. This is a great way to do high-level optimizations
|
|
like devirtualization, type-based alias analysis, etc. See the <a
|
|
href="http://blog.llvm.org/2010/04/extensible-metadata-in-llvm-ir.html">
|
|
Extensible Metadata Blog Post</a> for more information.</li>
|
|
|
|
<li>2.7 encodes <a href="SourceLevelDebugging.html">debug information</a>
|
|
in a completely new way, built on extensible metadata. The new implementation
|
|
is much more memory efficient and paves the way for improvements to optimized
|
|
code debugging experience.</li>
|
|
|
|
<li>2.7 now directly supports taking the address of a label and doing an
|
|
indirect branch through a pointer. This is particularly useful for
|
|
interpreter loops, and is used to implement the GCC "address of label"
|
|
extension. For more information, see the <a
|
|
href="http://blog.llvm.org/2010/01/address-of-label-and-indirect-branches.html">
|
|
Address of Label and Indirect Branches in LLVM IR Blog Post</a>.
|
|
|
|
<li>2.7 is the first release to start supporting APIs for assembling and
|
|
disassembling target machine code. These APIs are useful for a variety of
|
|
low level clients, and are surfaced in the new "enhanced disassembly" API.
|
|
For more information see the <a
|
|
href="http://blog.llvm.org/2010/01/x86-disassembler.html">The X86
|
|
Disassembler Blog Post</a> for more information.</li>
|
|
|
|
<li>2.7 includes major parts of the work required by the new MC Project,
|
|
see the <a href="#mc">MC update above</a> for more information.</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="coreimprovements">LLVM 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>LLVM IR now supports a 16-bit "half float" data type through <a
|
|
href="LangRef.html#int_fp16">two new intrinsics</a> and APFloat support.</li>
|
|
<li>LLVM IR supports two new <a href="LangRef.html#fnattrs">function
|
|
attributes</a>: inlinehint and alignstack(n). The former is a hint to the
|
|
optimizer that a function was declared 'inline' and thus the inliner should
|
|
weight it higher when considering inlining it. The later
|
|
indicates to the code generator that the function diverges from the platform
|
|
ABI on stack alignment.</li>
|
|
<li>The new <a href="LangRef.html#int_objectsize">llvm.objectsize</a> intrinsic
|
|
allows the optimizer to infer the sizes of memory objects in some cases.
|
|
This intrinsic is used to implement the GCC <tt>__builtin_object_size</tt>
|
|
extension.</li>
|
|
<li>LLVM IR now supports marking load and store instructions with <a
|
|
href="LangRef.html#i_load">"non-temporal" hints</a> (building on the new
|
|
metadata feature). This hint encourages the code
|
|
generator to generate non-temporal accesses when possible, which are useful
|
|
for code that is carefully managing cache behavior. Currently, only the
|
|
X86 backend provides target support for this feature.</li>
|
|
|
|
<li>LLVM 2.7 has pre-alpha support for <a
|
|
href="LangRef.html#t_union">unions in LLVM IR</a>.
|
|
Unfortunately, this support is not really usable in 2.7, so if you're
|
|
interested in pushing it forward, please help contribute to LLVM mainline.</li>
|
|
|
|
</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 inliner now merges arrays stack objects in different callees when
|
|
inlining multiple call sites into one function. This reduces the stack size
|
|
of the resultant function.</li>
|
|
<li>The -basicaa alias analysis pass (which is the default) has been improved to
|
|
be less dependent on "type safe" pointers. It can now look through bitcasts
|
|
and other constructs more aggressively, allowing better load/store
|
|
optimization.</li>
|
|
<li>The load elimination optimization in the GVN Pass [<a
|
|
href="http://blog.llvm.org/2009/12/introduction-to-load-elimination-in-gvn.html">intro
|
|
blog post</a>] has been substantially improved to be more aggressive about
|
|
partial redundancy elimination and do more aggressive phi translation. Please
|
|
see the <a
|
|
href="http://blog.llvm.org/2009/12/advanced-topics-in-redundant-load.html">
|
|
Advanced Topics in Redundant Load Elimination with a Focus on PHI Translation
|
|
Blog Post</a> for more details.</li>
|
|
<li>The module <a href="LangRef.html#datalayout">target data string</a> now
|
|
includes a notion of 'native' integer data types for the target. This
|
|
helps mid-level optimizations avoid promoting complex sequences of
|
|
operations to data types that are not natively supported (e.g. converting
|
|
i32 operations to i64 on 32-bit chips).</li>
|
|
<li>The mid-level optimizer is now conservative when operating on a module with
|
|
no target data. Previously, it would default to SparcV9 settings, which is
|
|
not what most people expected.</li>
|
|
<li>Jump threading is now much more aggressive at simplifying correlated
|
|
conditionals and threading blocks with otherwise complex logic. It has
|
|
subsumed the old "Conditional Propagation" pass, and -condprop has been
|
|
removed from LLVM 2.7.</li>
|
|
<li>The -instcombine pass has been refactored from being one huge file to being
|
|
a library of its own. Internally, it uses a customized IRBuilder to clean
|
|
it up and simplify it.</li>
|
|
|
|
<li>The optimal edge profiling pass is reliable and much more complete than in
|
|
2.6. It can be used with the llvm-prof tool but isn't wired up to the
|
|
llvm-gcc and clang command line options yet.</li>
|
|
|
|
<li>A new experimental alias analysis implementation, -scev-aa, has been added.
|
|
It uses LLVM's Scalar Evolution implementation to do symbolic analysis of
|
|
pointer offset expressions to disambiguate pointers. It can catch a few
|
|
cases that basicaa cannot, particularly in complex loop nests.</li>
|
|
|
|
<li>The default pass ordering has been tweaked for improved optimization
|
|
effectiveness.</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="executionengine">Interpreter and JIT Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>The JIT now supports generating debug information and is compatible with
|
|
the new GDB 7.0 (and later) interfaces for registering dynamically generated
|
|
debug info.</li>
|
|
|
|
<li>The JIT now <a href="http://llvm.org/PR5184">defaults
|
|
to compiling eagerly</a> to avoid a race condition in the lazy JIT.
|
|
Clients that still want the lazy JIT can switch it on by calling
|
|
<tt>ExecutionEngine::DisableLazyCompilation(false)</tt>.</li>
|
|
|
|
<li>It is now possible to create more than one JIT instance in the same process.
|
|
These JITs can generate machine code in parallel,
|
|
although <a href="http://llvm.org/docs/ProgrammersManual.html#jitthreading">you
|
|
still have to obey the other threading restrictions</a>.</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<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 'llc -asm-verbose' option (which is now the default) has been enhanced
|
|
to emit many useful comments to .s files indicating information about spill
|
|
slots and loop nest structure. This should make it much easier to read and
|
|
understand assembly files. This is wired up in llvm-gcc and clang to
|
|
the <tt>-fverbose-asm</tt> option.</li>
|
|
|
|
<li>New LSR with "full strength reduction" mode, which can reduce address
|
|
register pressure in loops where address generation is important.</li>
|
|
|
|
<li>A new codegen level Common Subexpression Elimination pass (MachineCSE)
|
|
is available and enabled by default. It catches redundancies exposed by
|
|
lowering.</li>
|
|
<li>A new pre-register-allocation tail duplication pass is available and enabled
|
|
by default, it can substantially improve branch prediction quality in some
|
|
cases.</li>
|
|
<li>A new sign and zero extension optimization pass (OptimizeExtsPass)
|
|
is available and enabled by default. This pass can takes advantage
|
|
architecture features like x86-64 implicit zero extension behavior and
|
|
sub-registers.</li>
|
|
<li>The code generator now supports a mode where it attempts to preserve the
|
|
order of instructions in the input code. This is important for source that
|
|
is hand scheduled and extremely sensitive to scheduling. It is compatible
|
|
with the GCC <tt>-fno-schedule-insns</tt> option.</li>
|
|
<li>The target-independent code generator now supports generating code with
|
|
arbitrary numbers of result values. Returning more values than was
|
|
previously supported is handled by returning through a hidden pointer. In
|
|
2.7, only the X86 and XCore targets have adopted support for this
|
|
though.</li>
|
|
<li>The code generator now supports generating code that follows the
|
|
<a href="LangRef.html#callingconv">Glasgow Haskell Compiler Calling
|
|
Convention</a> and ABI.</li>
|
|
<li>The "<a href="CodeGenerator.html#selectiondag_select">DAG instruction
|
|
selection</a>" phase of the code generator has been largely rewritten for
|
|
2.7. Previously, tblgen spit out tons of C++ code which was compiled and
|
|
linked into the target to do the pattern matching, now it emits a much
|
|
smaller table which is read by the target-independent code. The primary
|
|
advantages of this approach is that the size and compile time of various
|
|
targets is much improved. The X86 code generator shrunk by 1.5MB of code,
|
|
for example.</li>
|
|
<li>Almost the entire code generator has switched to emitting code through the
|
|
MC interfaces instead of printing textually to the .s file. This led to a
|
|
number of cleanups and speedups. In 2.7, debug an exception handling
|
|
information does not go through MC yet.</li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<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>The X86 backend now optimizes tails calls much more aggressively for
|
|
functions that use the standard C calling convention.</li>
|
|
<li>The X86 backend now models scalar SSE registers as subregs of the SSE vector
|
|
registers, making the code generator more aggressive in cases where scalars
|
|
and vector types are mixed.</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="ARM">ARM Target Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>New features of the ARM target include:
|
|
</p>
|
|
|
|
<ul>
|
|
|
|
<li>The ARM backend now generates instructions in unified assembly syntax.</li>
|
|
|
|
<li>llvm-gcc now has complete support for the ARM v7 NEON instruction set. This
|
|
support differs slightly from the GCC implementation. Please see the
|
|
<a
|
|
href="http://blog.llvm.org/2010/04/arm-advanced-simd-neon-intrinsics-and.html">
|
|
ARM Advanced SIMD (NEON) Intrinsics and Types in LLVM Blog Post</a> for
|
|
helpful information if migrating code from GCC to LLVM-GCC.</li>
|
|
|
|
<li>The ARM and Thumb code generators now use register scavenging for stack
|
|
object address materialization. This allows the use of R3 as a general
|
|
purpose register in Thumb1 code, as it was previous reserved for use in
|
|
stack address materialization. Secondly, sequential uses of the same
|
|
value will now re-use the materialized constant.</li>
|
|
|
|
<li>The ARM backend now has good support for ARMv4 targets and has been tested
|
|
on StrongARM hardware. Previously, LLVM only supported ARMv4T and
|
|
newer chips.</li>
|
|
|
|
<li>Atomic builtins are now supported for ARMv6 and ARMv7 (__sync_synchronize,
|
|
__sync_fetch_and_add, etc.).</li>
|
|
|
|
</ul>
|
|
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div 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>The optimizer uses the new CodeMetrics class to measure the size of code.
|
|
Various passes (like the inliner, loop unswitcher, etc) all use this to make
|
|
more accurate estimates of the code size impact of various
|
|
optimizations.</li>
|
|
<li>A new <a href="http://llvm.org/doxygen/InstructionSimplify_8h-source.html">
|
|
llvm/Analysis/InstructionSimplify.h</a> interface is available for doing
|
|
symbolic simplification of instructions (e.g. <tt>a+0</tt> -> <tt>a</tt>)
|
|
without requiring the instruction to exist. This centralizes a lot of
|
|
ad-hoc symbolic manipulation code scattered in various passes.</li>
|
|
<li>The optimizer now uses a new <a
|
|
href="http://llvm.org/doxygen/SSAUpdater_8h-source.html">SSAUpdater</a>
|
|
class which efficiently supports
|
|
doing unstructured SSA update operations. This centralized a bunch of code
|
|
scattered throughout various passes (e.g. jump threading, lcssa,
|
|
loop rotate, etc) for doing this sort of thing. The code generator has a
|
|
similar <a href="http://llvm.org/doxygen/MachineSSAUpdater_8h-source.html">
|
|
MachineSSAUpdater</a> class.</li>
|
|
<li>The <a href="http://llvm.org/doxygen/Regex_8h-source.html">
|
|
llvm/Support/Regex.h</a> header exposes a platform independent regular
|
|
expression API. Building on this, the <a
|
|
href="TestingGuide.html#FileCheck">FileCheck</a> utility now supports
|
|
regular exressions.</li>
|
|
<li>raw_ostream now supports a circular "debug stream" accessed with "dbgs()".
|
|
By default, this stream works the same way as "errs()", but if you pass
|
|
<tt>-debug-buffer-size=1000</tt> to opt, the debug stream is capped to a
|
|
fixed sized circular buffer and the output is printed at the end of the
|
|
program's execution. This is helpful if you have a long lived compiler
|
|
process and you're interested in seeing snapshots in time.</li>
|
|
</ul>
|
|
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="otherimprovements">Other Improvements and New Features</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>Other miscellaneous features include:</p>
|
|
|
|
<ul>
|
|
<li>You can now build LLVM as a big dynamic library (e.g. "libllvm2.7.so"). To
|
|
get this, configure LLVM with the --enable-shared option.</li>
|
|
|
|
<li>LLVM command line tools now overwrite their output by default. Previously,
|
|
they would only do this with -f. This makes them more convenient to use, and
|
|
behave more like standard unix tools.</li>
|
|
|
|
<li>The opt and llc tools now autodetect whether their input is a .ll or .bc
|
|
file, and automatically do the right thing. This means you don't need to
|
|
explicitly use the llvm-as tool for most things.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="changes">Major Changes and Removed Features</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>If you're already an LLVM user or developer with out-of-tree changes based
|
|
on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading
|
|
from the previous release.</p>
|
|
|
|
<ul>
|
|
|
|
<li>
|
|
The Andersen's alias analysis ("anders-aa") pass, the Predicate Simplifier
|
|
("predsimplify") pass, the LoopVR pass, the GVNPRE pass, and the random sampling
|
|
profiling ("rsprofiling") passes have all been removed. They were not being
|
|
actively maintained and had substantial problems. If you are interested in
|
|
these components, you are welcome to ressurect them from SVN, fix the
|
|
correctness problems, and resubmit them to mainline.</li>
|
|
|
|
<li>LLVM now defaults to building most libraries with RTTI turned off, providing
|
|
a code size reduction. Packagers who are interested in building LLVM to support
|
|
plugins that require RTTI information should build with "make REQUIRE_RTTI=1"
|
|
and should read the new <a href="Packaging.html">Advice on Packaging LLVM</a>
|
|
document.</li>
|
|
|
|
<li>The LLVM interpreter now defaults to <em>not</em> using <tt>libffi</tt> even
|
|
if you have it installed. This makes it more likely that an LLVM built on one
|
|
system will work when copied to a similar system. To use <tt>libffi</tt>,
|
|
configure with <tt>--enable-libffi</tt>.</li>
|
|
|
|
<li>Debug information uses a completely different representation, an LLVM 2.6
|
|
.bc file should work with LLVM 2.7, but debug info won't come forward.</li>
|
|
|
|
<li>The LLVM 2.6 (and earlier) "malloc" and "free" instructions got removed,
|
|
along with LowerAllocations pass. Now you should just use a call to the
|
|
malloc and free functions in libc. These calls are optimized as well as
|
|
the old instructions were.</li>
|
|
</ul>
|
|
|
|
<p>In addition, many APIs have changed in this release. Some of the major LLVM
|
|
API changes are:</p>
|
|
|
|
<ul>
|
|
|
|
<li>The <tt>add</tt>, <tt>sub</tt>, and <tt>mul</tt> instructions no longer
|
|
support floating-point operands. The <tt>fadd</tt>, <tt>fsub</tt>, and
|
|
<tt>fmul</tt> instructions should be used for this purpose instead.</li>
|
|
|
|
</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 10.4 and above in 32-bit
|
|
and 64-bit modes.</li>
|
|
<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
|
|
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
|
|
support is available for native builds with Visual C++).</li>
|
|
<li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</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="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
|
|
However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
|
|
for x86/x86-64 has been made available from the third party AuroraUX Project
|
|
that has been meticulously tested for bootstrapping LLVM & Clang.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<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, SystemZ and MicroBlaze
|
|
backends are experimental.</li>
|
|
<li><tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
|
|
supported value for this option. The MachO writer is experimental, and
|
|
works much better in mainline SVN.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<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 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, 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>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 and 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>
|
|
|
|
</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_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>
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|
|
<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
|
|
Last modified: $Date$
|
|
</address>
|
|
|
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</body>
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</html>
|