forked from OSchip/llvm-project
904 lines
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904 lines
33 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link rel="stylesheet" href="_static/llvm.css" type="text/css">
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<title>LLVM 3.1 Release Notes</title>
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</head>
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<body>
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<h1>LLVM 3.1 Release Notes</h1>
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<div>
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<img style="float:right" src="http://llvm.org/img/DragonSmall.png"
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width="136" height="136" alt="LLVM Dragon Logo">
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</div>
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<ol>
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<li><a href="#intro">Introduction</a></li>
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<li><a href="#subproj">Sub-project Status Update</a></li>
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<li><a href="#externalproj">External Projects Using LLVM 3.1</a></li>
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<li><a href="#whatsnew">What's New in LLVM?</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 3.1
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release.<br>
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You may prefer the
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<a href="http://llvm.org/releases/3.0/docs/ReleaseNotes.html">LLVM 3.0
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Release Notes</a>.</h1>
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<!-- *********************************************************************** -->
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<h2>
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<a name="intro">Introduction</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>This document contains the release notes for the LLVM Compiler
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Infrastructure, release 3.1. Here we describe the status of LLVM, including
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major improvements from the previous release, improvements in various
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subprojects of LLVM, and some of the current users of the code.
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All LLVM releases may be downloaded from
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the <a 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 web
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site</a>. If you have questions or comments,
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the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM
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Developer's 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 main
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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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<h2>
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<a name="subproj">Sub-project Status Update</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>The LLVM 3.1 distribution currently consists of code from the core LLVM
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repository (which roughly includes the LLVM optimizers, code generators and
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supporting tools), and the Clang repository. In addition to this code, the
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LLVM Project includes other sub-projects that are in development. Here we
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include updates on these subprojects.</p>
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<!--=========================================================================-->
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<h3>
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<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
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</h3>
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<div>
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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
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experience through expressive diagnostics, a high level of conformance to
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language standards, fast compilation, and low memory use. Like LLVM, Clang
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provides a modular, library-based architecture that makes it suitable for
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creating or 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 3.1 time-frame, the Clang team has made many improvements.
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Highlights include:</p>
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<ul>
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<li>Greatly expanded <a href="http://clang.llvm.org/cxx_status.html">C++11
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support</a> including lambdas, initializer lists, constexpr, user-defined
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literals, and atomics.</li>
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<li>A new <a href="http://clang.llvm.org/docs/Tooling.html">tooling</a>
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library to ease building of clang-based standalone tools.</li>
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<li>Extended support for
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<a href="http://clang.llvm.org/docs/ObjectiveCLiterals.html">literals in
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Objective C</a>.</li>
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</ul>
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<p>For more details about the changes to Clang since the 3.0 release, see the
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<a href="http://clang.llvm.org/docs/ReleaseNotes.html">Clang release
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notes.</a></p>
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<p>If Clang rejects your code but another compiler accepts it, 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 this is not intentional or a known
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issue.</p>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
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</h3>
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<div>
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<p><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. It works with gcc-4.5 and gcc-4.6
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(and partially with gcc-4.7), can target the x86-32/x86-64 and ARM processor
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families, and has been successfully used on the Darwin, FreeBSD, KFreeBSD,
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Linux and OpenBSD platforms. It fully supports Ada, C, C++ and Fortran. It
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has partial support for Go, Java, Obj-C and Obj-C++.</p>
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<p>The 3.1 release has the following notable changes:</p>
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<ul>
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<li>Partial support for gcc-4.7. Ada support is poor, but other languages work
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fairly well.</li>
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<li>Support for ARM processors. Some essential gcc headers that are needed to
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build DragonEgg for ARM are not installed by gcc. To work around this,
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copy the missing headers from the gcc source tree.</li>
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<li>Better optimization for Fortran by exploiting the fact that Fortran scalar
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arguments have 'restrict' semantics.</li>
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<li>Better optimization for all languages by passing information about type
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aliasing and type ranges to the LLVM optimizers.</li>
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<li>A regression test-suite was added.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
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</h3>
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<div>
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<p>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
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components. For example, when compiling for a 32-bit target, converting a
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double to a 64-bit unsigned integer is compiled into a runtime call to the
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"__fixunsdfdi" function. The compiler-rt library provides highly optimized
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implementations of this and other low-level routines (some are 3x faster than
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the equivalent libgcc routines).</p>
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<p>As of 3.1, compiler-rt includes the helper functions for atomic operations,
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allowing atomic operations on arbitrary-sized quantities to work. These
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functions follow the specification defined by gcc and are used by clang.</p>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="lldb">LLDB: Low Level Debugger</a>
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</h3>
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<div>
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<p><a href="http://lldb.llvm.org">LLDB</a> is a ground-up implementation of a
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command line debugger, as well as a debugger API that can be used from other
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applications. LLDB makes use of the Clang parser to provide high-fidelity
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expression parsing (particularly for C++) and uses the LLVM JIT for target
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support.</p>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="libc++">libc++: C++ Standard Library</a>
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</h3>
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<div>
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<p>Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
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licensed</a> under the MIT and UIUC license, allowing it to be used more
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permissively.</p>
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<p>Within the LLVM 3.1 time-frame there were the following highlights:</p>
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<ul>
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<li>The <code><atomic></code> header is now passing all tests, when
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compiling with clang and linking against the support code from
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compiler-rt.</li>
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<li>FreeBSD now includes libc++ as part of the base system.</li>
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<li>libc++ has been ported to Solaris and, in combination with libcxxrt and
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clang, is working with a large body of existing code.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="vmkit">VMKit</a>
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</h3>
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<div>
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<p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
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of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
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just-in-time compilation.</p>
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<p>In the LLVM 3.1 time-frame, VMKit has had significant improvements on both
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runtime and startup performance.</p>
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</div>
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<!--=========================================================================-->
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<h3>
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<a name="Polly">Polly: Polyhedral Optimizer</a>
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</h3>
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<div>
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<p><a href="http://polly.llvm.org/">Polly</a> is an <em>experimental</em>
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optimizer for data locality and parallelism. It currently provides high-level
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loop optimizations and automatic parallelisation (using the OpenMP run time).
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Work in the area of automatic SIMD and accelerator code generation was
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started.</p>
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<p>Within the LLVM 3.1 time-frame there were the following highlights:</p>
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<ul>
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<li>Polly became an official LLVM project</li>
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<li>Polly can be loaded directly into clang (enabled by '-O3 -mllvm -polly')</li>
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<li>An automatic scheduling optimizer (derived
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from <a href="http://pluto-compiler.sourceforge.net/">Pluto</a>) was
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integrated. It performs loop transformations to optimize for data-locality
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and parallelism. The transformations include, but are not limited to
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interchange, fusion, fission, skewing and tiling.</li>
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</ul>
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</div>
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="externalproj">External Open Source Projects Using LLVM 3.1</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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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 3.1.</p>
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<h3>Crack</h3>
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<div>
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<p><a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide
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the ease of development of a scripting language with the performance of a
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compiled language. The language derives concepts from C++, Java and Python,
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incorporating object-oriented programming, operator overloading and strong
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typing.</p>
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</div>
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<h3>FAUST</h3>
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<div>
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<p><a href="http://faust.grame.fr/">FAUST</a> is a compiled language for
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real-time audio signal processing. The name FAUST stands for Functional
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AUdio STream. Its programming model combines two approaches: functional
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programming and block diagram composition. In addition with the C, C++, Java,
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JavaScript output formats, the Faust compiler can generate LLVM bitcode, and
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works with LLVM 2.7-3.1.</p>
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</div>
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<h3>Glasgow Haskell Compiler (GHC)</h3>
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<div>
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<p><a href="http://www.haskell.org/ghc/">GHC</a> is an open source compiler and
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programming suite for Haskell, a lazy functional programming language. It
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includes an optimizing static compiler generating good code for a variety of
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platforms, together with an interactive system for convenient, quick
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development.</p>
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<p>GHC 7.0 and onwards include an LLVM code generator, supporting LLVM 2.8 and
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later.</p>
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</div>
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<h3>Julia</h3>
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<div>
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<p><a href="https://github.com/JuliaLang/julia">Julia</a> is a high-level,
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high-performance dynamic language for technical computing. It provides a
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sophisticated compiler, distributed parallel execution, numerical accuracy,
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and an extensive mathematical function library. The compiler uses type
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inference to generate fast code without any type declarations, and uses
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LLVM's optimization passes and JIT compiler. The
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<a href="http://julialang.org/"> Julia Language</a> is designed
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around multiple dispatch, giving programs a large degree of flexibility. It
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is ready for use on many kinds of problems.</p>
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</div>
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<h3>LLVM D Compiler</h3>
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<div>
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<p><a href="https://github.com/ldc-developers/ldc">LLVM D Compiler</a> (LDC) is
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a compiler for the D programming Language. It is based on the DMD frontend
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and uses LLVM as backend.</p>
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</div>
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<h3>Open Shading Language</h3>
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<div>
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<p><a href="https://github.com/imageworks/OpenShadingLanguage/">Open Shading
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Language (OSL)</a> is a small but rich language for programmable shading in
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advanced global illumination renderers and other applications, ideal for
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describing materials, lights, displacement, and pattern generation. It uses
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LLVM to JIT complex shader networks to x86 code at runtime.</p>
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<p>OSL was developed by Sony Pictures Imageworks for use in its in-house
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renderer used for feature film animation and visual effects, and is
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distributed as open source software with the "New BSD" license.</p>
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</div>
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<h3>Portable OpenCL (pocl)</h3>
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<div>
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<p>In addition to producing an easily portable open source OpenCL
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implementation, another major goal of <a href="http://pocl.sourceforge.net/">
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pocl</a> is improving performance portability of OpenCL programs with
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compiler optimizations, reducing the need for target-dependent manual
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optimizations. An important part of pocl is a set of LLVM passes used to
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statically parallelize multiple work-items with the kernel compiler, even in
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the presence of work-group barriers. This enables static parallelization of
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the fine-grained static concurrency in the work groups in multiple ways
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(SIMD, VLIW, superscalar,...).</p>
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</div>
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<h3>Pure</h3>
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<div>
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<p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
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algebraic/functional programming language based on term rewriting. Programs
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are collections of equations which are used to evaluate expressions in a
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symbolic fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
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programs to fast native code. Pure offers dynamic typing, eager and lazy
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evaluation, lexical closures, a hygienic macro system (also based on term
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rewriting), built-in list and matrix support (including list and matrix
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comprehensions) and an easy-to-use interface to C and other programming
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languages (including the ability to load LLVM bitcode modules, and inline C,
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C++, Fortran and Faust code in Pure programs if the corresponding
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LLVM-enabled compilers are installed).</p>
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<p>Pure version 0.54 has been tested and is known to work with LLVM 3.1 (and
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continues to work with older LLVM releases >= 2.5).</p>
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</div>
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<h3>TTA-based Co-design Environment (TCE)</h3>
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<div>
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<p><a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing
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application-specific processors (ASP) based on the Transport triggered
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architecture (TTA). The toolset provides a complete co-design flow from C/C++
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programs down to synthesizable VHDL/Verilog and parallel program binaries.
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Processor customization points include the register files, function units,
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supported operations, and the interconnection network.</p>
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<p>TCE uses Clang and LLVM for C/C++ language support, target independent
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optimizations and also for parts of code generation. It generates new
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LLVM-based code generators "on the fly" for the designed TTA processors and
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loads them in to the compiler backend as runtime libraries to avoid
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per-target recompilation of larger parts of the compiler chain.</p>
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</div>
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|
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</div>
|
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|
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<!-- *********************************************************************** -->
|
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<h2>
|
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<a name="whatsnew">What's New in LLVM 3.1?</a>
|
|
</h2>
|
|
<!-- *********************************************************************** -->
|
|
|
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<div>
|
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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
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listed in this section.</p>
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<!--=========================================================================-->
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<h3>
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<a name="majorfeatures">Major New Features</a>
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</h3>
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|
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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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Integrated assembler on by default for arm/thumb?
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-->
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<!-- Near dead:
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Analysis/RegionInfo.h + Dom Frontiers
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SparseBitVector: used in LiveVar.
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llvm/lib/Archive - replace with lib object?
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-->
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<p>LLVM 3.1 includes several major changes and big features:</p>
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<ul>
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<li><a href="../tools/clang/docs/AddressSanitizer.html">AddressSanitizer</a>,
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a fast memory error detector.</li>
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<li><a href="CodeGenerator.html#machineinstrbundle">MachineInstr Bundles</a>,
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Support to model instruction bundling / packing.</li>
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<li><a href="#armintegratedassembler">ARM Integrated Assembler</a>,
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A full featured assembler and direct-to-object support for ARM.</li>
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<li><a href="#blockplacement">Basic Block Placement</a>
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Probability driven basic block placement.</li>
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</ul>
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|
|
</div>
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|
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<!--=========================================================================-->
|
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<h3>
|
|
<a name="coreimprovements">LLVM IR and Core Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
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<p>LLVM IR has several new features for better support of new targets and that
|
|
expose new optimization opportunities:</p>
|
|
|
|
<ul>
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<li>A new type representing 16 bit <i>half</i> floating point values has
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been added.</li>
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|
<li>IR now supports vectors of pointers, including vector GEPs.</li>
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|
<li>Module flags have been introduced. They convey information about the
|
|
module as a whole to LLVM subsystems. This is currently used to encode
|
|
Objective C ABI information.</li>
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|
<li>Loads can now have range metadata attached to them to describe the
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possible values being loaded.</li>
|
|
<li>The <tt>llvm.ctlz</tt> and <tt>llvm.cttz</tt> intrinsics now have an
|
|
additional argument which indicates whether the behavior of the intrinsic
|
|
is undefined on a zero input. This can be used to generate more efficient
|
|
code on platforms that only have instructions which don't return the type
|
|
size when counting bits in 0.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="optimizer">Optimizer Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>In addition to many minor performance tweaks and bug fixes, this
|
|
release includes a few major enhancements and additions to the
|
|
optimizers:</p>
|
|
|
|
<ul>
|
|
<li>The loop unroll pass now is able to unroll loops with run-time trip counts.
|
|
This feature is turned off by default, and is enabled with the
|
|
<code>-unroll-runtime</code> flag.</li>
|
|
<li>A new basic-block autovectorization pass is available. Pass
|
|
<code>-vectorize</code> to run this pass along with some associated
|
|
post-vectorization cleanup passes. For more information, see the EuroLLVM
|
|
2012 slides: <a href="http://llvm.org/devmtg/2012-04-12/Slides/Hal_Finkel.pdf">
|
|
Autovectorization with LLVM</a>.</li>
|
|
<li>Inline cost heuristics have been completely overhauled and now closely
|
|
model constant propagation through call sites, disregard trivially dead
|
|
code costs, and can model C++ STL iterator patterns.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="mc">MC Level Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<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. 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>
|
|
|
|
<ul>
|
|
<li>The integrated assembler can optionally emit debug information when
|
|
assembling a </tt>.s</tt> file. It can be enabled by passing the
|
|
<tt>-g</tt> option to <tt>llvm-mc</tt>.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="codegen">Target Independent Code Generator Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>We have changed the way that the Type Legalizer legalizes vectors. The type
|
|
legalizer now attempts to promote integer elements. This enabled the
|
|
implementation of vector-select. Additionally, we see a performance boost on
|
|
workloads which use vectors of chars and shorts, since they are now promoted
|
|
to 32-bit types, which are better supported by the SIMD instruction set.
|
|
Floating point types are still widened as before.</p>
|
|
|
|
|
|
<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>TableGen can now synthesize register classes that are only needed to
|
|
represent combinations of constraints from instructions and sub-registers.
|
|
The synthetic register classes inherit most of their properties form their
|
|
closest user-defined super-class.</li>
|
|
<li><code>MachineRegisterInfo</code> now allows the reserved registers to be
|
|
frozen when register allocation starts. Target hooks should use the
|
|
<code>MRI->canReserveReg(FramePtr)</code> method to avoid accidentally
|
|
disabling frame pointer elimination during register allocation.</li>
|
|
<li>A new kind of <code>MachineOperand</code> provides a compact
|
|
representation of large clobber lists on call instructions. The register
|
|
mask operand references a bit mask of preserved registers. Everything else
|
|
is clobbered.</li>
|
|
<li>The DWARF debug info writer gained support for emitting data for the
|
|
<a href="SourceLevelDebugging.html#acceltable">name accelerator tables
|
|
DWARF extension</a>. It is used by LLDB to speed up name lookup.</li>
|
|
</ul>
|
|
|
|
<p> We added new TableGen infrastructure to support bundling for
|
|
Very Long Instruction Word (VLIW) architectures. TableGen can now
|
|
automatically generate a deterministic finite automaton from a VLIW
|
|
target's schedule description which can be queried to determine
|
|
legal groupings of instructions in a bundle.</p>
|
|
|
|
<p> We have added a new target independent VLIW packetizer based on the
|
|
DFA infrastructure to group machine instructions into bundles.</p>
|
|
|
|
</div>
|
|
|
|
<h4>
|
|
<a name="blockplacement">Basic Block Placement</a>
|
|
</h4>
|
|
<div>
|
|
<p>A probability based block placement and code layout algorithm was added to
|
|
LLVM's code generator. This layout pass supports probabilities derived from
|
|
static heuristics as well as source code annotations such as
|
|
<code>__builtin_expect</code>.</p>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="x86">X86-32 and X86-64 Target Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>New features and major changes in the X86 target include:</p>
|
|
|
|
<ul>
|
|
<li>Greatly improved support for AVX2.</li>
|
|
<li>Lots of bug fixes and improvements for AVX1.</li>
|
|
<li>Support for the FMA4 and XOP instruction set extensions.</li>
|
|
<li>Call instructions use the new register mask operands for faster compile
|
|
times and better support for different calling conventions. The old WINCALL
|
|
instructions are no longer needed.</li>
|
|
<li>DW2 Exception Handling is enabled on Cygwin and MinGW.</li>
|
|
<li>Support for implicit TLS model used with MSVC runtime.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="ARM">ARM Target Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>New features of the ARM target include:</p>
|
|
|
|
<ul>
|
|
<li>The constant island pass now supports basic block and constant pool entry
|
|
alignments greater than 4 bytes.</li>
|
|
<li>On Darwin, the ARM target now has a full-featured integrated assembler.
|
|
</li>
|
|
</ul>
|
|
|
|
<h4>
|
|
<a name="armintegratedassembler">ARM Integrated Assembler</a>
|
|
</h4>
|
|
<div>
|
|
<p>The ARM target now includes a full featured macro assembler, including
|
|
direct-to-object module support for clang. The assembler is currently enabled
|
|
by default for Darwin only pending testing and any additional necessary
|
|
platform specific support for Linux.</p>
|
|
|
|
<p>Full support is included for Thumb1, Thumb2 and ARM modes, along with
|
|
subtarget and CPU specific extensions for VFP2, VFP3 and NEON.</p>
|
|
|
|
<p>The assembler is Unified Syntax only (see ARM Architecural Reference Manual
|
|
for details). While there is some, and growing, support for pre-unfied (divided)
|
|
syntax, there are still significant gaps in that support.</p>
|
|
</div>
|
|
|
|
</div>
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="MIPS">MIPS Target Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
New features and major changes in the MIPS target include:</p>
|
|
|
|
<ul>
|
|
<li>MIPS32 little-endian direct object code emission is functional.</li>
|
|
<li>MIPS64 little-endian code generation is largely functional for N64 ABI in assembly printing mode with the exception of handling of long double (f128) type.</li>
|
|
<li>Support for new instructions has been added, which includes swap-bytes
|
|
instructions (WSBH and DSBH), floating point multiply-add/subtract and
|
|
negative multiply-add/subtract instructions, and floating
|
|
point load/store instructions with reg+reg addressing (LWXC1, etc.)</li>
|
|
<li>Various fixes to improve performance have been implemented.</li>
|
|
<li>Post-RA scheduling is now enabled at -O3.</li>
|
|
<li>Support for soft-float code generation has been added.</li>
|
|
<li>clang driver's support for MIPS 64-bits targets.</li>
|
|
<li>Support for MIPS floating point ABI option in clang driver.</li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="PTX">PTX Target Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>An outstanding conditional inversion bug was fixed in this release.</p>
|
|
|
|
<p><b>NOTE</b>: LLVM 3.1 marks the last release of the PTX back-end, in its
|
|
current form. The back-end is currently being replaced by the NVPTX
|
|
back-end, currently in SVN ToT.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="OtherTS">Other Target Specific Improvements</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<ul>
|
|
<li>Support for Qualcomm's Hexagon VLIW processor has been added.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="changes">Major Changes and Removed Features</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>If you're already an LLVM user or developer with out-of-tree changes based on
|
|
LLVM 3.1, this section lists some "gotchas" that you may run into upgrading
|
|
from the previous release.</p>
|
|
|
|
<ul>
|
|
<li>LLVM's build system now requires a python 2 interpreter to be present at
|
|
build time. A perl interpreter is no longer required.</li>
|
|
<li>The C backend has been removed. It had numerous problems, to the point of
|
|
not being able to compile any nontrivial program.</li>
|
|
<li>The Alpha, Blackfin and SystemZ targets have been removed due to lack of
|
|
maintenance.</li>
|
|
<li>LLVM 3.1 removes support for reading LLVM 2.9 bitcode files. Going
|
|
forward, we aim for all future versions of LLVM to read bitcode files and
|
|
<tt>.ll</tt> files produced by LLVM 3.0 and later.</li>
|
|
<li>The <tt>unwind</tt> instruction is now gone. With the introduction of the
|
|
new exception handling system in LLVM 3.0, the <tt>unwind</tt> instruction
|
|
became obsolete.</li>
|
|
<li>LLVM 3.0 and earlier automatically added the returns_twice fo functions
|
|
like setjmp based on the name. This functionality was removed in 3.1.
|
|
This affects Clang users, if -ffreestanding is used.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="api_changes">Internal API Changes</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>In addition, many APIs have changed in this release. Some of the major
|
|
LLVM API changes are:</p>
|
|
|
|
<ul>
|
|
<li>Target specific options have been moved from global variables to members
|
|
on the new <code>TargetOptions</code> class, which is local to each
|
|
<code>TargetMachine</code>. As a consequence, the associated flags will
|
|
no longer be accepted by <tt>clang -mllvm</tt>. This includes:
|
|
<ul>
|
|
<li><code>llvm::PrintMachineCode</code></li>
|
|
<li><code>llvm::NoFramePointerElim</code></li>
|
|
<li><code>llvm::NoFramePointerElimNonLeaf</code></li>
|
|
<li><code>llvm::DisableFramePointerElim(const MachineFunction &)</code></li>
|
|
<li><code>llvm::LessPreciseFPMADOption</code></li>
|
|
<li><code>llvm::LessPrecideFPMAD()</code></li>
|
|
<li><code>llvm::NoExcessFPPrecision</code></li>
|
|
<li><code>llvm::UnsafeFPMath</code></li>
|
|
<li><code>llvm::NoInfsFPMath</code></li>
|
|
<li><code>llvm::NoNaNsFPMath</code></li>
|
|
<li><code>llvm::HonorSignDependentRoundingFPMathOption</code></li>
|
|
<li><code>llvm::HonorSignDependentRoundingFPMath()</code></li>
|
|
<li><code>llvm::UseSoftFloat</code></li>
|
|
<li><code>llvm::FloatABIType</code></li>
|
|
<li><code>llvm::NoZerosInBSS</code></li>
|
|
<li><code>llvm::JITExceptionHandling</code></li>
|
|
<li><code>llvm::JITEmitDebugInfo</code></li>
|
|
<li><code>llvm::JITEmitDebugInfoToDisk</code></li>
|
|
<li><code>llvm::GuaranteedTailCallOpt</code></li>
|
|
<li><code>llvm::StackAlignmentOverride</code></li>
|
|
<li><code>llvm::RealignStack</code></li>
|
|
<li><code>llvm::DisableJumpTables</code></li>
|
|
<li><code>llvm::EnableFastISel</code></li>
|
|
<li><code>llvm::getTrapFunctionName()</code></li>
|
|
<li><code>llvm::EnableSegmentedStacks</code></li>
|
|
</ul></li>
|
|
|
|
<li>The <code>MDBuilder</code> class has been added to simplify the creation
|
|
of metadata.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="tools_changes">Tools Changes</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>In addition, some tools have changed in this release. Some of the changes
|
|
are:</p>
|
|
|
|
|
|
<ul>
|
|
<li><tt>llvm-stress</tt> is a command line tool for generating random
|
|
<tt>.ll</tt> files to fuzz different LLVM components. </li>
|
|
<li>The <tt>llvm-ld</tt> tool has been removed. The clang driver provides a
|
|
more reliable solution for turning a set of bitcode files into a binary.
|
|
To merge bitcode files <tt>llvm-link</tt> can be used instead.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<h3>
|
|
<a name="python">Python Bindings</a>
|
|
</h3>
|
|
|
|
<div>
|
|
|
|
<p>Officially supported Python bindings have been added! Feature support is far
|
|
from complete. The current bindings support interfaces to:</p>
|
|
<ul>
|
|
<li>Object File Interface</li>
|
|
<li>Disassembler</li>
|
|
</ul>
|
|
|
|
<p>Using the Object File Interface, it is possible to inspect binary object files.
|
|
Think of it as a Python version of readelf or llvm-objdump.</p>
|
|
|
|
<p>Support for additional features is currently being developed by community
|
|
contributors. If you are interested in shaping the direction of the Python
|
|
bindings, please express your intent on IRC or the developers list.</p>
|
|
|
|
</div>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2>
|
|
<a name="knownproblems">Known Problems</a>
|
|
</h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<p>LLVM is generally a production quality compiler, and is used by a broad range
|
|
of applications and shipping in many products. That said, not every
|
|
subsystem is as mature as the aggregate, particularly the more obscure
|
|
targets. 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 or ask on the <a
|
|
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
|
|
list</a>.</p>
|
|
|
|
<p>Known problem areas include:</p>
|
|
|
|
<ul>
|
|
<li>The CellSPU, MSP430, PTX and XCore backends are experimental.</li>
|
|
|
|
<li>The integrated assembler, disassembler, and JIT is not supported by
|
|
several targets. If an integrated assembler is not supported, then a
|
|
system assembler is required. For more details, see the <a
|
|
href="CodeGenerator.html#targetfeatures">Target Features Matrix</a>.
|
|
</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<h2>
|
|
<a name="additionalinfo">Additional Information</a>
|
|
</h2>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div>
|
|
|
|
<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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src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
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|
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<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
|
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Last modified: $Date$
|
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</address>
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</body>
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|