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875 lines
29 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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<meta encoding="utf8">
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<link rel="stylesheet" href="llvm.css" type="text/css">
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<title>LLVM 2.9 Release Notes</title>
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</head>
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<body>
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<h1 class="doc_title">LLVM 2.9 Release Notes</h1>
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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 2.9</a></li>
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<li><a href="#whatsnew">What's New in LLVM 2.9?</a></li>
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<li><a href="GettingStarted.html">Installation Instructions</a></li>
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<li><a href="#knownproblems">Known Problems</a></li>
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<li><a href="#additionalinfo">Additional Information</a></li>
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</ol>
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<div class="doc_author">
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<p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
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</div>
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<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.9
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release.<br>
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You may prefer the
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<a href="http://llvm.org/releases/2.8/docs/ReleaseNotes.html">LLVM 2.8
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Release Notes</a>.</h1>
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<!-- *********************************************************************** -->
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<h1>
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<a name="intro">Introduction</a>
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</h1>
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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 2.9. 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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<!-- Features that need text if they're finished for 3.1:
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ARM EHABI
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combiner-aa?
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strong phi elim
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loop dependence analysis
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CorrelatedValuePropagation
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lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
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-->
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<!-- *********************************************************************** -->
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<h1>
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<a name="subproj">Sub-project Status Update</a>
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</h1>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>
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The LLVM 2.9 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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<h2>
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<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
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</h2>
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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, Objective-C, C++ and Objective-C++ on x86
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(32- and 64-bit), and for darwin-arm targets.</p>
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<p>In the LLVM 2.9 time-frame, the Clang team has made many improvements in C,
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C++ and Objective-C support. C++ support is now generally rock solid, has
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been exercised on a broad variety of code, and has several new C++'0x features
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implemented (such as rvalue references and variadic templates). LLVM 2.9 has
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also brought in a large range of bug fixes and minor features (e.g. __label__
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support), and is much more compatible with the Linux Kernel.</p>
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<p>If Clang rejects your code that is built with another compiler, please take a
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look at the <a href="http://clang.llvm.org/compatibility.html">language
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compatibility</a> guide to make sure the issue isn't intentional or a known
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issue.
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</p>
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<ul>
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</ul>
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</div>
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<!--=========================================================================-->
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<h2>
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<a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
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</h2>
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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
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<a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
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optimizers and code generators with LLVM's.
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Currently it requires a patched version of gcc-4.5.
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The plugin can target the x86-32 and x86-64 processor families and has been
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used successfully on the Darwin, FreeBSD and Linux platforms.
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The Ada, C, C++ and Fortran languages work well.
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The plugin is capable of compiling plenty of Obj-C, Obj-C++ and Java but it is
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not known whether the compiled code actually works or not!
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</p>
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<p>
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The 2.9 release has the following notable changes:
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<ul>
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<li>The plugin is much more stable when compiling Fortran.</li>
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<li>Inline asm where an asm output is tied to an input of a different size is
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now supported in many more cases.</li>
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<li>Basic support for the __float128 type was added. It is now possible to
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generate LLVM IR from programs using __float128 but code generation does not
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work yet.</li>
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<li>Compiling Java programs no longer systematically crashes the plugin.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h2>
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<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
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</h2>
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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.
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compiler_rt is now dual licensed under MIT and UIUC license
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Several minor changes for better ARM support.
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New in LLVM 2.9, UPDATE</p>
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</div>
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<!--=========================================================================-->
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<h2>
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<a name="lldb">LLDB: Low Level Debugger</a>
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</h2>
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<div class="doc_text">
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<p>
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<a href="http://lldb.llvm.org/">LLDB</a> is a brand new member of the LLVM
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umbrella of projects. LLDB is a next generation, high-performance debugger. It
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is built as a set of reusable components which highly leverage existing
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libraries in the larger LLVM Project, such as the Clang expression parser, the
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LLVM disassembler and the LLVM JIT.</p>
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<p>
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LLDB is in early development and not included as part of the LLVM 2.9 release,
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<!--
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but is mature enough to support basic debugging scenarios on Mac OS X in C,
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Objective-C and C++. We'd really like help extending and expanding LLDB to
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support new platforms, new languages, new architectures, and new features.-->
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</p>
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|
|
</div>
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|
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<!--=========================================================================-->
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<h2>
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<a name="libc++">libc++: C++ Standard Library</a>
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</h2>
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<div class="doc_text">
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<p>
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<a href="http://libcxx.llvm.org/">libc++</a> is another new member of the LLVM
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family. It is an implementation of the C++ standard library, written from the
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ground up to specifically target the forthcoming C++'0X standard and focus on
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delivering great performance.</p>
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<p>
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As of the LLVM 2.9 release, UPDATE!
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libc++ is now dual licensed under MIT and UIUC license
|
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<!--libc++ is virtually feature complete, but would
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benefit from more testing and better integration with Clang++. It is also
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looking forward to the C++ committee finalizing the C++'0x standard.-->
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</p>
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</div>
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<!--=========================================================================-->
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<!--
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<h2>
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<a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
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</h2>
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<div class="doc_text">
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<p>
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<a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
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programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
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through the application and records state transitions that lead to fault
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states. This allows it to construct testcases that lead to faults and can even
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be used to verify some algorithms.
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</p>
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<p>UPDATE!</p>
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</div>-->
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|
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<!-- *********************************************************************** -->
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<h1>
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<a name="externalproj">External Open Source Projects Using LLVM 2.9</a>
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</h1>
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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 2.9.</p>
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</div>
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|
|
|
|
|
|
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<!-- *********************************************************************** -->
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<h1>
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<a name="whatsnew">What's New in LLVM 2.9?</a>
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</h1>
|
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<!-- *********************************************************************** -->
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|
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<div class="doc_text">
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<p>This release includes a huge number of bug fixes, performance tweaks and
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minor improvements. Some of the major improvements and new features are listed
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in this section.
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</p>
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</div>
|
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|
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<!--=========================================================================-->
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<h2>
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<a name="majorfeatures">Major New Features</a>
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</h2>
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<div class="doc_text">
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<p>LLVM 2.9 includes several major new capabilities:</p>
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<ul>
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<li><pre>
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last release for llvm-gcc
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TBAA: On by default in clang. Disable it with -fno-strict-aliasing.
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Could be more aggressive for structs.
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Triple::normalize is new, llvm triples are always stored in normalized form internally.
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Triple x86_64--mingw64 is obsoleted. Use x86_64--mingw32 instead.
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MC Assembler: X86 now generates much better diagnostics for common errors,
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is much faster at matching instructions, is much more bug-compatible with
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the GAS assembler, and is now generally useful for a broad range of X86
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assembly.
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New Nvidia PTX backend, not generally useful in 2.9 though.
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Much better debug info generated, particularly in optimized code situations.
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ARM Fast ISel
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ELF MC support: on by default in clang. There are still known missing features
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for human written assembly.
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X86: Reimplemented all of MMX to introduce a new LLVM IR x86_mmx type. Now
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random types like <2 x i32> are not iseld to mmx without emms. The
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-disable-mmx flag is gone now.
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Some basic <a href="CodeGenerator.html#mc">internals documentation</a> for MC.
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MC Assembler support for .file and .loc.
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inline asm multiple alternative constraint support.
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LoopIdiom: memset/memcpy formation and memset_pattern on darwin. Build with
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-ffreestanding or -fno-builtin if your memcpy is being compiled into infinite
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recursion.
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TargetLibraryInfo
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X86 support for FS/GS relative loads and stores using address space 256/257 are
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reliable now.
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ARM: New code placement pass.
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unnamed_addr + PR8927
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PointerTracking has been removed from mainline, moved to ClamAV.
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EarlyCSE pass.
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LoopInstSimplify pass.
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- DIBuilder provides simpler interface for front ends like Clang to encode debug info in LLVM IR.
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- This interface hides implementation details (e.g. DIDerivedType, existence of compile unit etc..) that any front end should not know about.
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For example, DIFactory DebugFactory;
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Ty = DebugFactory.CreateDerivedType(DW_TAG_volatile_type,
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findRegion(TYPE_CONTEXT(type)),
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StringRef(),
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getOrCreateFile(main_input_filename),
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0 /*line no*/,
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NodeSizeInBits(type),
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NodeAlignInBits(type),
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0 /*offset */,
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0 /* flags */,
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MainTy);
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can be replaced by
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DbgTy = DBuilder.createQualifiedType(DW_TAG_volatile_type, MainTy);
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DIFactory is gone now.
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PPC: Switched to MCInstPrinter, and MCCodeEmitter. Ready to implement support
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for directly writing out mach-o object files, but noone seems interested.
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ARM: Improved code generation for Cortex-A8 and Cortex-A9 CPUs.
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Scheduler now models operand latency and pipeline forwarding.
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Can optimize printf to iprintf when no floating point is used, for embedded
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targets with smaller iprintf implementation.
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error_code + libsystem + PathV2 changes
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The system_error header from C++0x was added.
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* Use if (error_code ec = function()) to check for error conditions
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from functions which return it.
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* error_code::message returns a human readable description of the error.
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PathV1 has been deprecated in favor of PathV2 (sorry I didn't finish
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this before the release).
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* No Path class, use a r-value convertible to a twine instead.
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* Assumes all paths are UTF-8.
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new macho-dump tool
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Major regalloc rewrite, not on by default for 2.9 and not advised to use it.
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* New basic register allocator that can be used as a safe fallback when
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debugging. Enable with -regalloc=basic.
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* New infrastructure for live range splitting. SplitKit can break a live
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interval into smaller pieces while preserving SSA form, and SpillPlacement
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can help find the best split points. This is a work in progress so the API
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is changing quickly.
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* The inline spiller has learned to clean up after live range splitting. It
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can hoist spills out of loops, and it can eliminate redundant spills.
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Rematerialization works with live range splitting.
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* New greedy register allocator using live range splitting. This will be the
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default register allocator in the next LLVM release, but it is not turned on
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by default in 2.9.
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ARM: __builtin_prefetch turns into prefetch instructions.
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MC assembler support for 3dNow! and 3DNowA instructions.
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tblgen support for assembler aliases: <a
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href="CodeGenerator.html#na_instparsing">MnemonicAlias and InstAlias</a>
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LoopIndexSplit pass was removed, unmaintained.
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LiveValues, SimplifyHalfPowrLibCalls, and GEPSplitter were removed.
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include/llvm/System merged into include/llvm/Support.
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Win32 PE-COFF support in the MC assembler has made a lot of progress in the 2.9
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timeframe, but is still not generally useful. Please see
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"http://llvm.org/bugs/showdependencytree.cgi?id=9100&hide_resolved=1" for open bugs?
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New <a href="WritingAnLLVMPass.html#RegionPass">RegionPass</a> infrastructure
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for region-based optimizations.
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MicroBlaze: major updates for aggressive delay slot filler, MC-based assembly
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printing, assembly instruction parsing, ELF .o file emission, and MC
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instruction disassembler.
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Countless ARM microoptimizations.
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Speedups to various mid-level passes:
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GVN is much faster on functions with deep dominator trees / lots of BBs.
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DomTree and DominatorFrontier are much faster to compute, and preserved by
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more passes (so they are computed less often)
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SRoA is also much faster and doesn't use DominanceFrontier.
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new 'hotpatch' attribute: LangRef.html#fnattrs
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APInt API changes, see PR5207.
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DSE is more aggressive with stores of different types: e.g. a large store
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following a small one to the same address.
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New naming rules in coding standards: CodingStandards.html#ll_naming
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LiveDebugVariables is a new pass that keeps track of debugging information for
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user variables that are kept in registers in optimized builds.
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We now optimize various idioms for overflow detection into check of the flag
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register on various CPUs, e.g.:
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unsigned long t = a+b;
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if (t < a) ...
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into:
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addq %rdi, %rbx
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jno LBB0_2
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X86: Much better codegen for several cases using adc/sbb instead of cmovs for
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conditional increment and other idioms.
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MVT::Flag renamed to MVT::Glue
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Removed the PartialSpecialization pass, it was unmaintained and buggy.
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SPARC: Many improvements, including using the Y registers for multiplications
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and addition of a simple delay slot filler.
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udiv, ashr, lshr, shl now have exact and nuw/nsw bits: PR8862 / LangRef.html
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lib/Object and llvm-objdump
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Target Independent Code Gen:
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The pre-register-allocation (preRA) instruction scheduler models register pressure
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much more accurately in some cases. This allows the adoption of more
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aggressive scheduling heuristics.
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The X86 backend has adopted a new preRA scheduling
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mode, "list-ilp", to shorten the height of instruction schedules
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without inducing register spills.
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The ARM backend preRA scheduler now models machine resources at cycle
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granularity. This allows the scheduler to both accurately model
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instruction latency and avoid overcommitting functional units.
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|
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</pre></li>
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</ul>
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</div>
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|
|
<!--=========================================================================-->
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<h2>
|
|
<a name="coreimprovements">LLVM IR and Core Improvements</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
<p>LLVM IR has several new features for better support of new targets and that
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|
expose new optimization opportunities:</p>
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|
|
|
<ul>
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|
</ul>
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|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h2>
|
|
<a name="optimizer">Optimizer Improvements</a>
|
|
</h2>
|
|
|
|
<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>TBAA.</li>
|
|
<li>LTO has been improved to use MC for parsing inline asm and now
|
|
can build large programs like Firefox 4 on both OS X and Linux.</li>
|
|
</ul>
|
|
|
|
<!--
|
|
<p>In addition to these features that are done in 2.8, there is preliminary
|
|
support in the release for Type Based Alias Analysis
|
|
Preliminary work on TBAA but not usable in 2.8.
|
|
New CorrelatedValuePropagation pass, not on by default in 2.8 yet.
|
|
-->
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h2>
|
|
<a name="mc">MC Level Improvements</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
The LLVM Machine Code (aka MC) subsystem was created to solve a number
|
|
of problems in the realm of assembly, disassembly, object file format handling,
|
|
and a number of other related areas that CPU instruction-set level tools work
|
|
in.</p>
|
|
|
|
<ul>
|
|
<li>MC is now used by default for ELF systems on x86 and
|
|
x86-64.</li>
|
|
<li>MC supports and CodeGen uses the <tt>.loc</tt> directives for
|
|
producing line number debug info. This produces more compact line
|
|
tables.</li>
|
|
<li>MC supports the <tt>.cfi_*</tt> directives for producing DWARF
|
|
frame information, but it is still not used by CodeGen by default.</li>
|
|
<li>COFF support?</li>
|
|
</ul>
|
|
|
|
<p>For more information, please see the <a
|
|
href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
|
|
LLVM MC Project Blog Post</a>.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h2>
|
|
<a name="codegen">Target Independent Code Generator Improvements</a>
|
|
</h2>
|
|
|
|
<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>
|
|
<!-- SplitKit -->
|
|
FastISel for ARM.
|
|
</ul>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h2>
|
|
<a name="x86">X86-32 and X86-64 Target Improvements</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
<p>New features and major changes in the X86 target include:
|
|
</p>
|
|
|
|
<ul>
|
|
<li>Several bugs have been fixed for Windows x64 code generator.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h2>
|
|
<a name="ARM">ARM Target Improvements</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
<p>New features of the ARM target include:
|
|
</p>
|
|
|
|
<ul>
|
|
</ul>
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<h2>
|
|
<a name="changes">Major Changes and Removed Features</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>If you're already an LLVM user or developer with out-of-tree changes based
|
|
on LLVM 2.8, this section lists some "gotchas" that you may run into upgrading
|
|
from the previous release.</p>
|
|
|
|
<ul>
|
|
</ul>
|
|
|
|
|
|
|
|
<p>In addition, many APIs have changed in this release. Some of the major LLVM
|
|
API changes are:</p>
|
|
<ul>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h2>
|
|
<a name="devtree_changes">Development Infrastructure Changes</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>This section lists changes to the LLVM development infrastructure. This
|
|
mostly impacts users who actively work on LLVM or follow development on
|
|
mainline, but may also impact users who leverage the LLVM build infrastructure
|
|
or are interested in LLVM qualification.</p>
|
|
|
|
<ul>
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h1>
|
|
<a name="knownproblems">Known Problems</a>
|
|
</h1>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<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>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="experimental">Experimental features included with this release</a>
|
|
</h2>
|
|
|
|
<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 Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ
|
|
and XCore backends are experimental.</li>
|
|
<li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets
|
|
other than darwin-i386 and darwin-x86_64. FIXME: Not true on ELF anymore?</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="x86-be">Known problems with the X86 back-end</a>
|
|
</h2>
|
|
|
|
<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 X86-64 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>
|
|
<li>Windows x64 (aka Win64) code generator has a few issues.
|
|
<ul>
|
|
<li>llvm-gcc cannot build the mingw-w64 runtime currently
|
|
due to lack of support for the 'u' inline assembly
|
|
constraint and for X87 floating point inline assembly.</li>
|
|
<li>On mingw-w64, you will see unresolved symbol <tt>__chkstk</tt>
|
|
due to <a href="http://llvm.org/bugs/show_bug.cgi?id=8919">Bug 8919</a>.
|
|
It is fixed in <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110321/118499.html">r128206</a>.</li>
|
|
<li>Miss-aligned MOVDQA might crash your program. It is due to
|
|
<a href="http://llvm.org/bugs/show_bug.cgi?id=9483">Bug 9483</a>,
|
|
lack of handling aligned internal globals.</li>
|
|
</ul>
|
|
</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="ppc-be">Known problems with the PowerPC back-end</a>
|
|
</h2>
|
|
|
|
<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>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="arm-be">Known problems with the ARM back-end</a>
|
|
</h2>
|
|
|
|
<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>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="sparc-be">Known problems with the SPARC back-end</a>
|
|
</h2>
|
|
|
|
<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>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="mips-be">Known problems with the MIPS back-end</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>64-bit MIPS targets are not supported yet.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="alpha-be">Known problems with the Alpha back-end</a>
|
|
</h2>
|
|
|
|
<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>
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="c-be">Known problems with the C back-end</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The C backend has numerous problems and is not being actively maintained.
|
|
Depending on it for anything serious is not advised.</p>
|
|
|
|
<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>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<h2>
|
|
<a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
|
|
</h2>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>llvm-gcc is generally very stable for the C family of languages. 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>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. Note that llvm-gcc is missing major
|
|
Fortran performance work in the frontend and library that went into GCC after
|
|
4.2. If you are interested in Fortran, we recommend that you consider using
|
|
<a href="#dragonegg">dragonegg</a> instead.</p>
|
|
|
|
<p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
|
|
actively maintained. If you are interested in Ada, we recommend that you
|
|
consider using <a href="#dragonegg">dragonegg</a> instead.</p>
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h1>
|
|
<a name="additionalinfo">Additional Information</a>
|
|
</h1>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<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>
|
|
|
|
</body>
|
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</html>
|