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| <h1>LLVM 3.1 Release Notes</h1> | |
| <div> | |
| <img style="float:right" src="http://llvm.org/img/DragonSmall.png" | |
| width="136" height="136" alt="LLVM Dragon Logo"> | |
| </div> | |
| <ol> | |
| <li><a href="#intro">Introduction</a></li> | |
| <li><a href="#subproj">Sub-project Status Update</a></li> | |
| <li><a href="#externalproj">External Projects Using LLVM 3.1</a></li> | |
| <li><a href="#whatsnew">What's New in LLVM?</a></li> | |
| <li><a href="GettingStarted.html">Installation Instructions</a></li> | |
| <li><a href="#knownproblems">Known Problems</a></li> | |
| <li><a href="#additionalinfo">Additional Information</a></li> | |
| </ol> | |
| <div class="doc_author"> | |
| <p>Written by the <a href="http://llvm.org/">LLVM Team</a></p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <h2> | |
| <a name="intro">Introduction</a> | |
| </h2> | |
| <!-- *********************************************************************** --> | |
| <div> | |
| <p>This document contains the release notes for the LLVM Compiler | |
| Infrastructure, release 3.1. Here we describe the status of LLVM, including | |
| major improvements from the previous release, improvements in various | |
| subprojects of LLVM, and some of the current users of the code. | |
| All LLVM releases may be downloaded from | |
| the <a href="http://llvm.org/releases/">LLVM releases web site</a>.</p> | |
| <p>For more information about LLVM, including information about the latest | |
| release, please check out the <a href="http://llvm.org/">main LLVM web | |
| site</a>. If you have questions or comments, | |
| the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM | |
| Developer's Mailing List</a> is a good place to send them.</p> | |
| <p>Note that if you are reading this file from a Subversion checkout or the main | |
| LLVM web page, this document applies to the <i>next</i> release, not the | |
| current one. To see the release notes for a specific release, please see the | |
| <a href="http://llvm.org/releases/">releases page</a>.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <h2> | |
| <a name="subproj">Sub-project Status Update</a> | |
| </h2> | |
| <!-- *********************************************************************** --> | |
| <div> | |
| <p>The LLVM 3.1 distribution currently consists of code from the core LLVM | |
| repository (which roughly includes the LLVM optimizers, code generators and | |
| supporting tools), and the Clang repository. In addition to this code, the | |
| LLVM Project includes other sub-projects that are in development. Here we | |
| include updates on these subprojects.</p> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a> | |
| </h3> | |
| <div> | |
| <p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C, | |
| C++, and Objective-C languages. Clang aims to provide a better user | |
| experience through expressive diagnostics, a high level of conformance to | |
| language standards, fast compilation, and low memory use. Like LLVM, Clang | |
| provides a modular, library-based architecture that makes it suitable for | |
| creating or integrating with other development tools. Clang is considered a | |
| production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86 | |
| (32- and 64-bit), and for Darwin/ARM targets.</p> | |
| <p>In the LLVM 3.1 time-frame, the Clang team has made many improvements. | |
| Highlights include:</p> | |
| <ul> | |
| <li>Greatly expanded <a href="http://clang.llvm.org/cxx_status.html">C++11 | |
| support</a> including lambdas, initializer lists, constexpr, user-defined | |
| literals, and atomics.</li> | |
| <li>A new <a href="http://clang.llvm.org/docs/Tooling.html">tooling</a> | |
| library to ease building of clang-based standalone tools.</li> | |
| <li>Extended support for | |
| <a href="http://clang.llvm.org/docs/ObjectiveCLiterals.html">literals in | |
| Objective C</a>.</li> | |
| </ul> | |
| <p>For more details about the changes to Clang since the 3.0 release, see the | |
| <a href="http://clang.llvm.org/docs/ReleaseNotes.html">Clang release | |
| notes.</a></p> | |
| <p>If Clang rejects your code but another compiler accepts it, please take a | |
| look at the <a href="http://clang.llvm.org/compatibility.html">language | |
| compatibility</a> guide to make sure this is not intentional or a known | |
| issue.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a> | |
| </h3> | |
| <div> | |
| <p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a | |
| <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's | |
| optimizers and code generators with LLVM's. It works with gcc-4.5 and gcc-4.6 | |
| (and partially with gcc-4.7), can target the x86-32/x86-64 and ARM processor | |
| families, and has been successfully used on the Darwin, FreeBSD, KFreeBSD, | |
| Linux and OpenBSD platforms. It fully supports Ada, C, C++ and Fortran. It | |
| has partial support for Go, Java, Obj-C and Obj-C++.</p> | |
| <p>The 3.1 release has the following notable changes:</p> | |
| <ul> | |
| <li>Partial support for gcc-4.7. Ada support is poor, but other languages work | |
| fairly well.</li> | |
| <li>Support for ARM processors. Some essential gcc headers that are needed to | |
| build DragonEgg for ARM are not installed by gcc. To work around this, | |
| copy the missing headers from the gcc source tree.</li> | |
| <li>Better optimization for Fortran by exploiting the fact that Fortran scalar | |
| arguments have 'restrict' semantics.</li> | |
| <li>Better optimization for all languages by passing information about type | |
| aliasing and type ranges to the LLVM optimizers.</li> | |
| <li>A regression test-suite was added.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a> | |
| </h3> | |
| <div> | |
| <p>The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a> | |
| is a simple library that provides an implementation of the low-level | |
| target-specific hooks required by code generation and other runtime | |
| components. For example, when compiling for a 32-bit target, converting a | |
| double to a 64-bit unsigned integer is compiled into a runtime call to the | |
| "__fixunsdfdi" function. The compiler-rt library provides highly optimized | |
| implementations of this and other low-level routines (some are 3x faster than | |
| the equivalent libgcc routines).</p> | |
| <p>As of 3.1, compiler-rt includes the helper functions for atomic operations, | |
| allowing atomic operations on arbitrary-sized quantities to work. These | |
| functions follow the specification defined by gcc and are used by clang.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="lldb">LLDB: Low Level Debugger</a> | |
| </h3> | |
| <div> | |
| <p><a href="http://lldb.llvm.org">LLDB</a> is a ground-up implementation of a | |
| command line debugger, as well as a debugger API that can be used from other | |
| applications. LLDB makes use of the Clang parser to provide high-fidelity | |
| expression parsing (particularly for C++) and uses the LLVM JIT for target | |
| support.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="libc++">libc++: C++ Standard Library</a> | |
| </h3> | |
| <div> | |
| <p>Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual | |
| licensed</a> under the MIT and UIUC license, allowing it to be used more | |
| permissively.</p> | |
| <p>Within the LLVM 3.1 time-frame there were the following highlights:</p> | |
| <ul> | |
| <li>The <code><atomic></code> header is now passing all tests, when | |
| compiling with clang and linking against the support code from | |
| compiler-rt.</li> | |
| <li>FreeBSD now includes libc++ as part of the base system.</li> | |
| <li>libc++ has been ported to Solaris and, in combination with libcxxrt and | |
| clang, is working with a large body of existing code.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="vmkit">VMKit</a> | |
| </h3> | |
| <div> | |
| <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation | |
| of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and | |
| just-in-time compilation.</p> | |
| <p>In the LLVM 3.1 time-frame, VMKit has had significant improvements on both | |
| runtime and startup performance.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="Polly">Polly: Polyhedral Optimizer</a> | |
| </h3> | |
| <div> | |
| <p><a href="http://polly.llvm.org/">Polly</a> is an <em>experimental</em> | |
| optimizer for data locality and parallelism. It currently provides high-level | |
| loop optimizations and automatic parallelisation (using the OpenMP run time). | |
| Work in the area of automatic SIMD and accelerator code generation was | |
| started.</p> | |
| <p>Within the LLVM 3.1 time-frame there were the following highlights:</p> | |
| <ul> | |
| <li>Polly became an official LLVM project</li> | |
| <li>Polly can be loaded directly into clang (enabled by '-O3 -mllvm -polly')</li> | |
| <li>An automatic scheduling optimizer (derived | |
| from <a href="http://pluto-compiler.sourceforge.net/">Pluto</a>) was | |
| integrated. It performs loop transformations to optimize for data-locality | |
| and parallelism. The transformations include, but are not limited to | |
| interchange, fusion, fission, skewing and tiling.</li> | |
| </ul> | |
| </div> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <h2> | |
| <a name="externalproj">External Open Source Projects Using LLVM 3.1</a> | |
| </h2> | |
| <!-- *********************************************************************** --> | |
| <div> | |
| <p>An exciting aspect of LLVM is that it is used as an enabling technology for | |
| a lot of other language and tools projects. This section lists some of the | |
| projects that have already been updated to work with LLVM 3.1.</p> | |
| <h3>Crack</h3> | |
| <div> | |
| <p><a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide | |
| the ease of development of a scripting language with the performance of a | |
| compiled language. The language derives concepts from C++, Java and Python, | |
| incorporating object-oriented programming, operator overloading and strong | |
| typing.</p> | |
| </div> | |
| <h3>FAUST</h3> | |
| <div> | |
| <p><a href="http://faust.grame.fr/">FAUST</a> is a compiled language for | |
| real-time audio signal processing. The name FAUST stands for Functional | |
| AUdio STream. Its programming model combines two approaches: functional | |
| programming and block diagram composition. In addition with the C, C++, Java, | |
| JavaScript output formats, the Faust compiler can generate LLVM bitcode, and | |
| works with LLVM 2.7-3.1.</p> | |
| </div> | |
| <h3>Glasgow Haskell Compiler (GHC)</h3> | |
| <div> | |
| <p><a href="http://www.haskell.org/ghc/">GHC</a> is an open source compiler and | |
| programming suite for Haskell, a lazy functional programming language. It | |
| includes an optimizing static compiler generating good code for a variety of | |
| platforms, together with an interactive system for convenient, quick | |
| development.</p> | |
| <p>GHC 7.0 and onwards include an LLVM code generator, supporting LLVM 2.8 and | |
| later.</p> | |
| </div> | |
| <h3>Julia</h3> | |
| <div> | |
| <p><a href="https://github.com/JuliaLang/julia">Julia</a> is a high-level, | |
| high-performance dynamic language for technical computing. It provides a | |
| sophisticated compiler, distributed parallel execution, numerical accuracy, | |
| and an extensive mathematical function library. The compiler uses type | |
| inference to generate fast code without any type declarations, and uses | |
| LLVM's optimization passes and JIT compiler. The | |
| <a href="http://julialang.org/"> Julia Language</a> is designed | |
| around multiple dispatch, giving programs a large degree of flexibility. It | |
| is ready for use on many kinds of problems.</p> | |
| </div> | |
| <h3>LLVM D Compiler</h3> | |
| <div> | |
| <p><a href="https://github.com/ldc-developers/ldc">LLVM D Compiler</a> (LDC) is | |
| a compiler for the D programming Language. It is based on the DMD frontend | |
| and uses LLVM as backend.</p> | |
| </div> | |
| <h3>Open Shading Language</h3> | |
| <div> | |
| <p><a href="https://github.com/imageworks/OpenShadingLanguage/">Open Shading | |
| Language (OSL)</a> is a small but rich language for programmable shading in | |
| advanced global illumination renderers and other applications, ideal for | |
| describing materials, lights, displacement, and pattern generation. It uses | |
| LLVM to JIT complex shader networks to x86 code at runtime.</p> | |
| <p>OSL was developed by Sony Pictures Imageworks for use in its in-house | |
| renderer used for feature film animation and visual effects, and is | |
| distributed as open source software with the "New BSD" license.</p> | |
| </div> | |
| <h3>Portable OpenCL (pocl)</h3> | |
| <div> | |
| <p>In addition to producing an easily portable open source OpenCL | |
| implementation, another major goal of <a href="http://pocl.sourceforge.net/"> | |
| pocl</a> is improving performance portability of OpenCL programs with | |
| compiler optimizations, reducing the need for target-dependent manual | |
| optimizations. An important part of pocl is a set of LLVM passes used to | |
| statically parallelize multiple work-items with the kernel compiler, even in | |
| the presence of work-group barriers. This enables static parallelization of | |
| the fine-grained static concurrency in the work groups in multiple ways | |
| (SIMD, VLIW, superscalar,...).</p> | |
| </div> | |
| <h3>Pure</h3> | |
| <div> | |
| <p><a href="http://pure-lang.googlecode.com/">Pure</a> is an | |
| algebraic/functional programming language based on term rewriting. Programs | |
| are collections of equations which are used to evaluate expressions in a | |
| symbolic fashion. The interpreter uses LLVM as a backend to JIT-compile Pure | |
| programs to fast native code. Pure offers dynamic typing, eager and lazy | |
| evaluation, lexical closures, a hygienic macro system (also based on term | |
| rewriting), built-in list and matrix support (including list and matrix | |
| comprehensions) and an easy-to-use interface to C and other programming | |
| languages (including the ability to load LLVM bitcode modules, and inline C, | |
| C++, Fortran and Faust code in Pure programs if the corresponding | |
| LLVM-enabled compilers are installed).</p> | |
| <p>Pure version 0.54 has been tested and is known to work with LLVM 3.1 (and | |
| continues to work with older LLVM releases >= 2.5).</p> | |
| </div> | |
| <h3>TTA-based Co-design Environment (TCE)</h3> | |
| <div> | |
| <p><a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing | |
| application-specific processors (ASP) based on the Transport triggered | |
| architecture (TTA). The toolset provides a complete co-design flow from C/C++ | |
| programs down to synthesizable VHDL/Verilog and parallel program binaries. | |
| Processor customization points include the register files, function units, | |
| supported operations, and the interconnection network.</p> | |
| <p>TCE uses Clang and LLVM for C/C++ language support, target independent | |
| optimizations and also for parts of code generation. It generates new | |
| LLVM-based code generators "on the fly" for the designed TTA processors and | |
| loads them in to the compiler backend as runtime libraries to avoid | |
| per-target recompilation of larger parts of the compiler chain.</p> | |
| </div> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <h2> | |
| <a name="whatsnew">What's New in LLVM 3.1?</a> | |
| </h2> | |
| <!-- *********************************************************************** --> | |
| <div> | |
| <p>This release includes a huge number of bug fixes, performance tweaks and | |
| minor improvements. Some of the major improvements and new features are | |
| listed in this section.</p> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="majorfeatures">Major New Features</a> | |
| </h3> | |
| <div> | |
| <!-- Features that need text if they're finished for 3.1: | |
| ARM EHABI | |
| combiner-aa? | |
| strong phi elim | |
| loop dependence analysis | |
| CorrelatedValuePropagation | |
| lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1. | |
| Integrated assembler on by default for arm/thumb? | |
| --> | |
| <!-- Near dead: | |
| Analysis/RegionInfo.h + Dom Frontiers | |
| SparseBitVector: used in LiveVar. | |
| llvm/lib/Archive - replace with lib object? | |
| --> | |
| <p>LLVM 3.1 includes several major changes and big features:</p> | |
| <ul> | |
| <li><a href="../tools/clang/docs/AddressSanitizer.html">AddressSanitizer</a>, | |
| a fast memory error detector.</li> | |
| <li><a href="CodeGenerator.html#machineinstrbundle">MachineInstr Bundles</a>, | |
| Support to model instruction bundling / packing.</li> | |
| <li><a href="#armintegratedassembler">ARM Integrated Assembler</a>, | |
| A full featured assembler and direct-to-object support for ARM.</li> | |
| <li><a href="#blockplacement">Basic Block Placement</a> | |
| Probability driven basic block placement.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <h3> | |
| <a name="coreimprovements">LLVM IR and Core Improvements</a> | |
| </h3> | |
| <div> | |
| <p>LLVM IR has several new features for better support of new targets and that | |
| expose new optimization opportunities:</p> | |
| <ul> | |
| <li>A new type representing 16 bit <i>half</i> floating point values has | |
| been added.</li> | |
| <li>IR now supports vectors of pointers, including vector GEPs.</li> | |
| <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> | |
| <li>Loads can now have range metadata attached to them to describe the | |
| 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> | |
| <!-- *********************************************************************** --> | |
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