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| |
| <h1>LLVM 3.2 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 3.2</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 3.2. Here we describe the status of LLVM, including |
| major improvements from the previous release, improvements in various |
| sub-projects 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 3.2 distribution currently consists of production-quality code |
| from the core LLVM repository, which roughly includes the LLVM optimizers, |
| code generators and supporting tools, as well as Clang, DragonEgg and |
| compiler-rt sub-project repositories. In addition to this code, the LLVM |
| Project includes other sub-projects that are in development. Here we |
| include updates on these sub-projects.</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.</p> |
| |
| <p>In the LLVM 3.2 time-frame, the Clang team has made many improvements. |
| Highlights include:</p> |
| <ul> |
| <li>Improvements to Clang's diagnostics</li> |
| <li>Support for tls_model attribute</li> |
| <li>Type safety attributes</li> |
| </ul> |
| |
| <p>For more details about the changes to Clang since the 3.1 release, see the |
| <a href="http://llvm.org/releases/3.2/tools/clang/docs/ReleaseNotes.html">Clang 3.2 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 3.2 release has the following notable changes:</p> |
| |
| <ul> |
| <li>Able to load LLVM plugins such as Polly.</li> |
| <li>Supports thread-local storage models.</li> |
| <li>Passes knowledge of variable lifetimes to the LLVM optimizers.</li> |
| <li>No longer requires GCC to be built with LTO support.</li> |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <h3> |
| <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a> |
| </h3> |
| |
| <div> |
| |
| |
| <p>The 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 |
| <code>__fixunsdfdi</code> 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>The 3.2 release has the following notable changes:</p> |
| |
| <ul> |
| <li><a href="http://llvm.org/releases/3.2/tools/clang/docs/ThreadSanitizer.html">ThreadSanitizer (TSan)</a> - data race detector run-time library for C/C++ has been added.</li> |
| <li>Improvements to <a href="http://llvm.org/releases/3.2/tools/clang/docs/AddressSanitizer.html">AddressSanitizer</a> including: better portability |
| (OSX, Android NDK), support for cmake based builds, enhanced error reporting and lots of bug fixes.</li> |
| <li>Added support for A6 'Swift' CPU.</li> |
| <li><code>divsi3</code> function has been enhanced to take advantage of a hardware unsigned divide when it is available.</li> |
| </ul> |
| |
| </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> |
| |
| <p>The 3.2 release has the following notable changes:</p> |
| |
| <ul> |
| <li>Linux build fixes for clang (see <a href="http://lldb.llvm.org/build.html">Building LLDB</a>)</li> |
| <li>Some Linux stability and usability improvements</li> |
| <li>Switch expression evaluation to use MCJIT (from legacy JIT) on Linux</li> |
| </ul> |
| |
| </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 3.2 time-frame there were the following highlights:</p> |
| |
| <ul> |
| <li> C++11 shared_ptr atomic access API (20.7.2.5) has been implemented.</li> |
| <li>Applied noexcept and constexpr throughout library.</li> |
| <li>Improved C++11 conformance in associative container emplace.</li> |
| <li>Performance improvements in: std::rotate algorithm and I/O.</li> |
| <li>Operator new/delete and type_infos for exception types moved from libc++ to libc++abi.</li> |
| <li>Bug fixes in: <code><atomic></code>; vector<code><bool></code> algorithms, |
| <code><future></code>,<code><tuple></code>, |
| <code><type_traits></code>,<code><fstream></code>,<code><istream></code>, |
| <code><iterator></code>, <code><condition_variable></code>,<code><complex></code> as well as visibility fixes. |
| </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>The 3.2 release has the following notable changes:</p> |
| |
| <ul> |
| <li>Bug fixes only, no functional changes.</li> |
| </ul> |
| |
| </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 parallelization (using the OpenMP run time). |
| Work in the area of automatic SIMD and accelerator code generation was |
| started.</p> |
| |
| <p>Within the LLVM 3.2 time-frame there were the following highlights:</p> |
| |
| <ul> |
| <li>isl, the integer set library used by Polly, was relicensed under the MIT license.</li> |
| <li>isl based code generation.</li> |
| <li>MIT licensed replacement for CLooG (LGPLv2).</li> |
| <li>Fine grained option handling (separation of core and border computations, control overhead vs. code size).</li> |
| <li>Support for FORTRAN and Dragonegg.</li> |
| <li>OpenMP code generation fixes.</li> |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <h3> |
| <a name="StaticAnalyzer">Clang Static Analyzer</a> |
| </h3> |
| |
| <div> |
| |
| <p>The <a href="http://clang-analyzer.llvm.org/">Clang Static Analyzer</a> |
| is an advanced source code analysis tool integrated into Clang that performs |
| a deep analysis of code to find potential bugs.</p> |
| |
| <p>In the LLVM 3.2 release, the static analyzer has made significant improvements |
| in many areas, with notable highlights such as:</p> |
| |
| <ul> |
| <li>Improved interprocedural analysis within a translation unit (see details below), which greatly amplified the analyzer's ability to find bugs.</li> |
| <li>New infrastructure to model "well-known" APIs, allowing the analyzer to do a much better job when modeling calls to such functions.</li> |
| <li>Significant improvements to the APIs to write static analyzer checkers, with a more unified way of representing function/method calls in the checker API. Details can be found in the <a href="http://llvm.org/devmtg/2012-11#talk13">Building a Checker in 24 hours</a> talk. |
| </ul> |
| |
| <p>The release specifically includes notable improvements for Objective-C analysis, including:</p> |
| |
| <ul> |
| <li>Interprocedural analysis for Objective-C methods.</li> |
| <li>Interprocedural analysis of calls to "blocks".</li> |
| <li>Precise modeling of GCD APIs such as <tt>dispatch_once</tt> and friends.</li> |
| <li>Improved support for recently added Objective-C constructs such as array and dictionary literals.</li> |
| </ul> |
| |
| <p>The release specifically includes notable improvements for C++ analysis, including:</p> |
| |
| <ul> |
| <li>Interprocedural analysis for C++ methods (within a translation unit).</li> |
| <li>More precise modeling of C++ initializers and destructors.</li> |
| </ul> |
| |
| <p>Finally, this release includes many small improvements to <tt>scan-build</tt>, which can be used to drive the analyzer from the command line or a continuous integration system. This includes a directory-traversal issue, which could cause potential security problems in some cases. We would like to acknowledge Tim Brown of Portcullis Computer Security Ltd for reporting this issue.</p> |
| |
| </div> |
| |
| </div> |
| |
| <!-- *********************************************************************** --> |
| <h2> |
| <a name="externalproj">External Open Source Projects Using LLVM 3.2</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 3.2.</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>EmbToolkit</h3> |
| |
| <div> |
| |
| <p><a href="http://www.embtoolkit.org/">EmbToolkit</a> provides Linux cross-compiler |
| toolchain/SDK (GCC/binutils/C library (uclibc,eglibc,musl)), a build system for |
| package cross-compilation and optionally various root file systems. |
| It supports ARM and MIPS. There is an ongoing effort to provide a clang+llvm |
| environment for the 3.2 releases, |
| </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 2.7-3.2.</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. |
| It has been used for all the shading on such films as The Amazing Spider-Man, |
| Men in Black III, Hotel Transylvania, and may other films in-progress, |
| and also has been incorporated into several commercial and open source |
| rendering products such as Blender, VRay, and Autodesk Beast.</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 0.56 has been tested and is known to work with LLVM 3.2 (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 3.2?</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 3.2: |
| ARM EHABI |
| combiner-aa? |
| strong phi elim |
| loop dependence analysis |
| CorrelatedValuePropagation |
| lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.2. |
| 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 3.2 includes several major changes and big features:</p> |
| |
| <ul> |
| <li>Loop Vectorizer.</li> |
| <li>New implementation of SROA.</li> |
| <li>New NVPTX back-end (replacing existing PTX back-end) based on NVIDIA sources.</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>Thread local variables may have a specified TLS model. See the |
| <a href="LangRef.html#globalvars">Language Reference Manual</a>.</li> |
| <li>'TYPE_CODE_FUNCTION_OLD' type code and autoupgrade code for old function attributes format has been removed.</li> |
| <li>Internal representation of the Attributes class has been converted into a pointer to an |
| opaque object that's uniqued by and stored in the LLVMContext object. |
| The Attributes class then becomes a thin wrapper around this opaque object.</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> |
| |
| <p> Loop Vectorizer - We've added a loop vectorizer and we are now able to |
| vectorize small loops. The loop vectorizer is disabled by default and |
| can be enabled using the <b>-mllvm -vectorize-loops</b> flag. |
| The SIMD vector width can be specified using the flag |
| <b>-mllvm -force-vector-width=4</b>. |
| The default value is <b>0</b> which means auto-select. |
| <br/> |
| We can now vectorize this function: |
| |
| <pre class="doc_code"> |
| unsigned sum_arrays(int *A, int *B, int start, int end) { |
| unsigned sum = 0; |
| for (int i = start; i < end; ++i) |
| sum += A[i] + B[i] + i; |
| |
| return sum; |
| } |
| </pre> |
| |
| We vectorize under the following loops: |
| <ul> |
| <li>The inner most loops must have a single basic block.</li> |
| <li>The number of iterations are known before the loop starts to execute.</li> |
| <li>The loop counter needs to be incremented by one.</li> |
| <li>The loop trip count <b>can</b> be a variable.</li> |
| <li>Loops do <b>not</b> need to start at zero.</li> |
| <li>The induction variable can be used inside the loop.</li> |
| <li>Loop reductions are supported.</li> |
| <li>Arrays with affine access pattern do <b>not</b> need to be marked as 'noalias' and are checked at runtime.</li> |
| </ul> |
| |
| </p> |
| |
| <p>SROA - We’ve re-written SROA to be significantly more powerful and generate |
| code which is much more friendly to the rest of the optimization pipeline. |
| Previously this pass had scaling problems that required it to only operate on |
| relatively small aggregates, and at times it would mistakenly replace a large |
| aggregate with a single very large integer in order to make it a scalar SSA |
| value. The result was a large number of i1024 and i2048 values representing any |
| small stack buffer. These in turn slowed down many subsequent optimization |
| paths.</p> |
| <p>The new SROA pass uses a different algorithm that allows it to only promote to |
| scalars the pieces of the aggregate actively in use. Because of this it doesn’t |
| require any thresholds. It also always deduces the scalar values from the uses |
| of the aggregate rather than the specific LLVM type of the aggregate. These |
| features combine to both optimize more code with the pass but to improve the |
| compile time of many functions dramatically.</p> |
| |
| <ul> |
| <li>Branch weight metadata is preserved through more of the optimizer.</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> Added support for following assembler directives: <code>.ifb</code>, <code>.ifnb</code>, <code>.ifc</code>, |
| <code>.ifnc</code>, <code>.purgem</code>, <code>.rept</code> and <code>.version</code> (ELF) as well as Darwin specific |
| <code>.pushsection</code>, <code>.popsection</code> and <code>.previous</code> .</li> |
| <li>Enhanced handling of <code>.lcomm directive</code>.</li> |
| <li>MS style inline assembler: added implementation of the offset and TYPE operators.</li> |
| <li>Targets can specify minimum supported NOP size for NOP padding.</li> |
| <li>ELF improvements: added support for generating ELF objects on Windows.</li> |
| <li>MachO improvements: symbol-difference variables are marked as N_ABS, added direct-to-object attribute for data-in-code markers.</li> |
| <li>Added support for annotated disassembly output for x86 and arm targets.</li> |
| <li>Arm support has been improved by adding support for ARM TARGET2 relocation |
| and fixing hadling of ARM-style "$d.*" labels.</li> |
| <li>Implemented local-exec TLS on PowerPC.</li> |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <h3> |
| <a name="codegen">Target Independent Code Generator Improvements</a> |
| </h3> |
| |
| <div> |
| |
| <p>Stack Coloring - We have implemented a new optimization pass |
| to merge stack objects which are used in disjoin areas of the code. |
| This optimization reduces the required stack space significantly, in cases |
| where it is clear to the optimizer that the stack slot is not shared. |
| We use the lifetime markers to tell the codegen that a certain alloca |
| is used within a region.</p> |
| |
| <p> We now merge consecutive loads and stores. </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> |
| |
| <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> |
| |
| <p> We have added new TableGen infrastructure to support relationship maps |
| between instructions. This feature enables TableGen to automatically |
| construct a set of relation tables and query functions that can be used |
| to switch between various forms of instructions. For more information, |
| please refer to <a href="http://llvm.org/docs/HowToUseInstrMappings.html"> |
| How To Use Instruction Mappings</a>.</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>Small codegen optimizations, especially for AVX2.</li> |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <h3> |
| <a name="ARM">ARM Target Improvements</a> |
| </h3> |
| |
| <div> |
| |
| <p>New features of the ARM target include:</p> |
| |
| <ul> |
| <li>Support and performance tuning for the A6 'Swift' CPU.</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 |
| sub-target 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> |
| |
| <p>New features and major changes in the MIPS target include:</p> |
| |
| <ul> |
| <li>Integrated assembler support: |
| MIPS32 works for both PIC and static, known limitation is the PR14456 where |
| R_MIPS_GPREL16 relocation is generated with the wrong addend. |
| MIPS64 support is incomplete, for example exception handling is not working.</li> |
| <li>Support for fast calling convention has been added.</li> |
| <li>Support for Android MIPS toolchain has been added to clang driver.</li> |
| <li>Added clang driver support for MIPS N32 ABI through "-mabi=n32" option.</li> |
| <li>MIPS32 and MIPS64 disassembler has been implemented.</li> |
| <li>Support for compiling programs with large GOTs (exceeding 64kB in size) has been added |
| through llc option "-mxgot".</li> |
| <li>Added experimental support for MIPS32 DSP intrinsics.</li> |
| <li>Experimental support for MIPS16 with following limitations: only soft float is supported, |
| C++ exceptions are not supported, large stack frames (> 32000 bytes) are not supported, |
| direct object code emission is not supported only .s .</li> |
| <li>Standalone assembler (llvm-mc): implementation is in progress and considered experimental.</li> |
| <li>All classic JIT and MCJIT tests pass on Little and Big Endian MIPS32 platforms.</li> |
| <li>Inline asm support: all common constraints and operand modifiers have been implemented.</li> |
| <li>Added tail call optimization support, use llc option "-enable-mips-tail-calls" |
| or clang options "-mllvm -enable-mips-tail-calls"to enable it.</li> |
| <li>Improved register allocation by removing registers $fp, $gp, $ra and $at from the list of reserved registers.</li> |
| <li>Long branch expansion pass has been implemented, which expands branch |
| instructions with offsets that do not fit in the 16-bit field.</li> |
| <li>Cavium Octeon II board is used for testing builds (llvm-mips-linux builder).</li> |
| </ul> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <h3> |
| <a name="PowerPC">PowerPC Target Improvements</a> |
| </h3> |
| |
| <div> |
| |
| <p>Many fixes and changes across LLVM (and Clang) for better compliance with |
| the 64-bit PowerPC ELF Application Binary Interface, interoperability with |
| GCC, and overall 64-bit PowerPC support. Some highlights include:</p> |
| <ul> |
| <li> MCJIT support added.</li> |
| <li> PPC64 relocation support and (small code model) TOC handling |
| added.</li> |
| <li> Parameter passing and return value fixes (alignment issues, |
| padding, varargs support, proper register usage, odd-sized |
| structure support, float support, extension of return values |
| for i32 return values).</li> |
| <li> Fixes in spill and reload code for vector registers.</li> |
| <li> C++ exception handling enabled.</li> |
| <li> Changes to remediate double-rounding compatibility issues with |
| respect to GCC behavior.</li> |
| <li> Refactoring to disentangle ppc64-elf-linux ABI from Darwin |
| ppc64 ABI support.</li> |
| <li> Assorted new test cases and test case fixes (endian and word |
| size issues).</li> |
| <li> Fixes for big-endian codegen bugs, instruction encodings, and |
| instruction constraints.</li> |
| <li> Implemented -integrated-as support.</li> |
| <li> Additional support for Altivec compare operations.</li> |
| <li> IBM long double support.</li> |
| </ul> |
| <p>There have also been code generation improvements for both 32- and 64-bit |
| code. Instruction scheduling support for the Freescale e500mc and e5500 |
| cores has been added.</p> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <h3> |
| <a name="NVPTX">PTX/NVPTX Target Improvements</a> |
| </h3> |
| |
| <div> |
| |
| <p>The PTX back-end has been replaced by the NVPTX back-end, which is based on |
| the LLVM back-end used by NVIDIA in their CUDA (nvcc) and OpenCL compiler. |
| Some highlights include:</p> |
| <ul> |
| <li>Compatibility with PTX 3.1 and SM 3.5</li> |
| <li>Support for NVVM intrinsics as defined in the NVIDIA Compiler SDK</li> |
| <li>Full compatibility with old PTX back-end, with much greater coverage of |
| LLVM IR</li> |
| </ul> |
| |
| <p>Please submit any back-end bugs to the LLVM Bugzilla site.</p> |
| |
| </div> |
| |
| <!--=========================================================================--> |
| <h3> |
| <a name="OtherTS">Other Target Specific Improvements</a> |
| </h3> |
| |
| <div> |
| |
| <ul> |
| <li>Added support for custom names for library functions in TargetLibraryInfo.</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 3.2, this section lists some "gotchas" that you may run into upgrading |
| from the previous release.</p> |
| |
| <ul> |
| <li>llvm-ld and llvm-stub have been removed, llvm-ld functionality can be partially replaced by |
| llvm-link | opt | {llc | as, llc -filetype=obj} | ld, or fully replaced by Clang. </li> |
| <li>MCJIT: added support for inline assembly (requires asm parser), added faux remote target execution to lli option '-remote-mcjit'.</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> |
| |
| <p> We've added a new interface for allowing IR-level passes to access |
| target-specific information. A new IR-level pass, called |
| "TargetTransformInfo" provides a number of low-level interfaces. |
| LSR and LowerInvoke already use the new interface. </p> |
| |
| <p> The TargetData structure has been renamed to DataLayout and moved to VMCore |
| to remove a dependency on Target. </p> |
| |
| </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>opt: added support for '-mtriple' option.</li> |
| <li>llvm-mc : - added '-disassemble' support for '-show-inst' and '-show-encoding' options, added '-edis' option to produce annotated |
| disassembly output for X86 and ARM targets.</li> |
| <li>libprofile: allows the profile data file name to be specified by the LLVMPROF_OUTPUT environment variable.</li> |
| <li>llvm-objdump: has been changed to display available targets, '-arch' option accepts x86 and x86-64 as valid arch names.</li> |
| <li>llc and opt: added FMA formation from pairs of FADD + FMUL or FSUB + FMUL enabled by option '-enable-excess-fp-precision' or option '-enable-unsafe-fp-math', |
| option '-fp-contract' controls the creation by optimizations of fused FP by selecting Fast, Standard, or Strict mode.</li> |
| <li>llc: object file output from llc is no longer considered experimental.</li> |
| <li>gold plugin: handles Position Independent Executables.</li> |
| </ul> |
| |
| </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, and XCore backends are experimental, and the CellSPU backend will be removed in LLVM 3.3.</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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