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| <div class="doc_title">LLVM 2.8 Release Notes</div> | |
| <img align=right src="http://llvm.org/img/DragonSmall.png" | |
| width="136" height="136" alt="LLVM Dragon Logo"> | |
| <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 2.8</a></li> | |
| <li><a href="#whatsnew">What's New in LLVM 2.8?</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> | |
| <!-- | |
| <h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8 | |
| release.<br> | |
| You may prefer the | |
| <a href="http://llvm.org/releases/2.7/docs/ReleaseNotes.html">LLVM 2.7 | |
| Release Notes</a>.</h1> | |
| --> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> | |
| <a name="intro">Introduction</a> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>This document contains the release notes for the LLVM Compiler | |
| Infrastructure, release 2.8. Here we describe the status of LLVM, including | |
| major improvements from the previous release and significant known problems. | |
| 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> | |
| <!-- | |
| Almost dead code. | |
| include/llvm/Analysis/LiveValues.h => Dan | |
| lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8. | |
| GEPSplitterPass | |
| --> | |
| <!-- Features that need text if they're finished for 2.9: | |
| combiner-aa? | |
| strong phi elim | |
| loop dependence analysis | |
| TBAA | |
| CorrelatedValuePropagation | |
| --> | |
| <!-- Announcement, lldb, libc++ --> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> | |
| <a name="subproj">Sub-project Status Update</a> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p> | |
| The LLVM 2.8 distribution currently consists of code from the core LLVM | |
| repository (which roughly includes the LLVM optimizers, code generators | |
| and supporting tools), the Clang repository and the llvm-gcc 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> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a> | |
| </div> | |
| <div class="doc_text"> | |
| <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 2.8 time-frame, the Clang team has made many improvements:</p> | |
| <ul> | |
| <li>Clang C++ is now feature-complete with respect to the ISO C++ 1998 and 2003 standards.</li> | |
| <li>Added support for Objective-C++.</li> | |
| <li>Clang now uses LLVM-MC to directly generate object code and to parse inline assembly (on Darwin).</li> | |
| <li>Introduced many new warnings, including <code>-Wmissing-field-initializers</code>, <code>-Wshadow</code>, <code>-Wno-protocol</code>, <code>-Wtautological-compare</code>, <code>-Wstrict-selector-match</code>, <code>-Wcast-align</code>, <code>-Wunused</code> improvements, and greatly improved format-string checking.</li> | |
| <li>Introduced the "libclang" library, a C interface to Clang intended to support IDE clients.</li> | |
| <li>Added support for <code>#pragma GCC visibility</code>, <code>#pragma align</code>, and others.</li> | |
| <li>Added support for SSE, ARM NEON, and Altivec.</li> | |
| <li>Improved support for many Microsoft extensions.</li> | |
| <li>Implemented support for blocks in C++.</li> | |
| <li>Implemented precompiled headers for C++.</li> | |
| <li>Improved abstract syntax trees to retain more accurate source information.</li> | |
| <li>Added driver support for handling LLVM IR and bitcode files directly.</li> | |
| <li>Major improvements to compiler correctness for exception handling.</li> | |
| <li>Improved generated code quality in some areas: | |
| <ul> | |
| <li>Good code generation for X86-32 and X86-64 ABI handling.</li> | |
| <li>Improved code generation for bit-fields, although important work remains.</li> | |
| </ul> | |
| </li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="clangsa">Clang Static Analyzer</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The <a href="http://clang-analyzer.llvm.org/">Clang Static Analyzer</a> | |
| project is an effort to use static source code analysis techniques to | |
| automatically find bugs in C and Objective-C programs (and hopefully <a | |
| href="http://clang-analyzer.llvm.org/dev_cxx.html">C++ in the | |
| future</a>!). The tool is very good at finding bugs that occur on specific | |
| paths through code, such as on error conditions.</p> | |
| <p>The LLVM 2.8 release fixes a number of bugs and slightly improves precision | |
| over 2.7, but there are no major new features in the release. | |
| </p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to | |
| gcc-4.5. Unlike llvm-gcc, dragonegg in theory does not require any gcc-4.5 | |
| modifications whatsoever (currently one small patch is needed) thanks to the | |
| new <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>. | |
| DragonEgg is a gcc plugin that makes gcc-4.5 use the LLVM optimizers and code | |
| generators instead of gcc's, just like with llvm-gcc. | |
| </p> | |
| <p> | |
| DragonEgg is still a work in progress, but it is able to compile a lot of code, | |
| for example all of gcc, LLVM and clang. Currently Ada, C, C++ and Fortran work | |
| well, while all other languages either don't work at all or only work poorly. | |
| For the moment only the x86-32 and x86-64 targets are supported, and only on | |
| linux and darwin (darwin may need additional gcc patches). | |
| </p> | |
| <p> | |
| The 2.8 release has the following notable changes: | |
| <ul> | |
| <li>The plugin loads faster due to exporting fewer symbols.</li> | |
| <li>Additional vector operations such as addps256 are now supported.</li> | |
| <li>Ada global variables with no initial value are no longer zero initialized, | |
| resulting in better optimization.</li> | |
| <li>The '-fplugin-arg-dragonegg-enable-gcc-optzns' flag now runs all gcc | |
| optimizers, rather than just a handful.</li> | |
| <li>Fortran programs using common variables now link correctly.</li> | |
| <li>GNU OMP constructs no longer crash the compiler.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a> | |
| </div> | |
| <div class="doc_text"> | |
| <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. As of LLVM 2.8, VMKit now supports copying garbage | |
| collectors, and can be configured to use MMTk's copy mark-sweep garbage | |
| collector. In LLVM 2.8, the VMKit .NET VM is no longer being maintained. | |
| </p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a> | |
| </div> | |
| <div class="doc_text"> | |
| <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> | |
| All of the code in the compiler-rt project is available under the standard LLVM | |
| License, a "BSD-style" license. New in LLVM 2.8, compiler_rt now supports | |
| soft floating point (for targets that don't have a real floating point unit), | |
| and includes an extensive testsuite for the "blocks" language feature and the | |
| blocks runtime included in compiler_rt.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="lldb">LLDB: Low Level Debugger</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://lldb.llvm.org/">LLDB</a> is a brand new member of the LLVM | |
| umbrella of projects. LLDB is a next generation, high-performance debugger. It | |
| is built as a set of reusable components which highly leverage existing | |
| libraries in the larger LLVM Project, such as the Clang expression parser, the | |
| LLVM disassembler and the LLVM JIT.</p> | |
| <p> | |
| LLDB is in early development and not included as part of the LLVM 2.8 release, | |
| but is mature enough to support basic debugging scenarios on Mac OS X in C, | |
| Objective-C and C++. We'd really like help extending and expanding LLDB to | |
| support new platforms, new languages, new architectures, and new features. | |
| </p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="libc++">libc++: C++ Standard Library</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://libc++.llvm.org/">libc++</a> is another new member of the LLVM | |
| family. It is an implementation of the C++ standard library, written from the | |
| ground up to specifically target the forthcoming C++'0X standard and focus on | |
| delivering great performance.</p> | |
| <p> | |
| As of the LLVM 2.8 release, libc++ is virtually feature complete, but would | |
| benefit from more testing and better integration with Clang++. It is also | |
| looking forward to the C++ committee finalizing the C++'0x standard. | |
| </p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="klee">KLEE: A Symbolic Execution Virtual Machine</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for | |
| programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths | |
| through the application and records state transitions that lead to fault | |
| states. This allows it to construct testcases that lead to faults and can even | |
| be used to verify some algorithms. | |
| </p> | |
| <p>Although KLEE does not have any major new features as of 2.8, we have made | |
| various minor improvements, particular to ease development:</p> | |
| <ul> | |
| <li>Added support for LLVM 2.8. KLEE currently maintains compatibility with | |
| LLVM 2.6, 2.7, and 2.8.</li> | |
| <li>Added a buildbot for 2.6, 2.7, and trunk. A 2.8 buildbot will be coming | |
| soon following release.</li> | |
| <li>Fixed many C++ code issues to allow building with Clang++. Mostly | |
| complete, except for the version of MiniSAT which is inside the KLEE STP | |
| version.</li> | |
| <li>Improved support for building with separate source and build | |
| directories.</li> | |
| <li>Added support for "long double" on x86.</li> | |
| <li>Initial work on KLEE support for using 'lit' test runner instead of | |
| DejaGNU.</li> | |
| <li>Added <tt>configure</tt> support for using an external version of | |
| STP.</li> | |
| </ul> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> | |
| <a name="externalproj">External Open Source Projects Using LLVM 2.8</a> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <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 2.8.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="tce">TTA-based Codesign Environment (TCE)</a> | |
| </div> | |
| <div class="doc_text"> | |
| <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 and parallel program binaries. Processor | |
| customization points include the register files, function units, supported | |
| operations, and the interconnection network.</p> | |
| <p>TCE uses llvm-gcc/Clang and LLVM for C/C++ language support, target | |
| independent optimizations and also for parts of code generation. It generates | |
| new LLVM-based code generators "on the fly" for the designed TTA processors and | |
| loads them in to the compiler backend as runtime libraries to avoid per-target | |
| recompilation of larger parts of the compiler chain.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="Horizon">Horizon Bytecode Compiler</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://www.quokforge.org/projects/horizon">Horizon</a> is a bytecode | |
| language and compiler written on top of LLVM, intended for producing | |
| single-address-space managed code operating systems that | |
| run faster than the equivalent multiple-address-space C systems. | |
| More in-depth blurb is available on the <a | |
| href="http://www.quokforge.org/projects/horizon/wiki/Wiki">wiki</a>.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="clamav">Clam AntiVirus</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://www.clamav.net">Clam AntiVirus</a> is an open source (GPL) | |
| anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail | |
| gateways. Since version 0.96 it has <a | |
| href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode | |
| signatures</a> that allow writing detections for complex malware. It | |
| uses LLVM's JIT to speed up the execution of bytecode on | |
| X86, X86-64, PPC32/64, falling back to its own interpreter otherwise. | |
| The git version was updated to work with LLVM 2.8. | |
| </p> | |
| <p>The <a | |
| href="http://git.clamav.net/gitweb?p=clamav-bytecode-compiler.git;a=blob_plain;f=docs/user/clambc-user.pdf"> | |
| ClamAV bytecode compiler</a> uses Clang and LLVM to compile a C-like | |
| language, insert runtime checks, and generate ClamAV bytecode.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="pure">Pure</a> | |
| </div> | |
| <div class="doc_text"> | |
| <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. 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 C interface. The interpreter uses | |
| LLVM as a backend to JIT-compile Pure programs to fast native code.</p> | |
| <p>Pure versions 0.44 and later have been tested and are known to work with | |
| LLVM 2.8 (and continue to work with older LLVM releases >= 2.5).</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="GHC">Glasgow Haskell Compiler (GHC)</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://www.haskell.org/ghc/">GHC</a> is an open source, | |
| state-of-the-art programming suite for | |
| Haskell, a standard lazy functional programming language. It includes | |
| an optimizing static compiler generating good code for a variety of | |
| platforms, together with an interactive system for convenient, quick | |
| development.</p> | |
| <p>In addition to the existing C and native code generators, GHC 7.0 now | |
| supports an <a | |
| href="http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/Backends/LLVM">LLVM | |
| code generator</a>. GHC supports LLVM 2.7 and later.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="Clay">Clay Programming Language</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://tachyon.in/clay/">Clay</a> is a new systems programming | |
| language that is specifically designed for generic programming. It makes | |
| generic programming very concise thanks to whole program type propagation. It | |
| uses LLVM as its backend.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="llvm-py">llvm-py Python Bindings for LLVM</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://www.mdevan.org/llvm-py/">llvm-py</a> has been updated to work | |
| with LLVM 2.8. llvm-py provides Python bindings for LLVM, allowing you to write a | |
| compiler backend or a VM in Python.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="FAUST">FAUST Real-Time Audio Signal Processing Language</a> | |
| </div> | |
| <div class="doc_text"> | |
| <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 output formats, the | |
| Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7 and | |
| 2.8.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="jade">Jade Just-in-time Adaptive Decoder Engine</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p><a | |
| href="http://sourceforge.net/apps/trac/orcc/wiki/JadeDocumentation">Jade</a> | |
| (Just-in-time Adaptive Decoder Engine) is a generic video decoder engine using | |
| LLVM for just-in-time compilation of video decoder configurations. Those | |
| configurations are designed by MPEG Reconfigurable Video Coding (RVC) committee. | |
| MPEG RVC standard is built on a stream-based dataflow representation of | |
| decoders. It is composed of a standard library of coding tools written in | |
| RVC-CAL language and a dataflow configuration — block diagram — | |
| of a decoder.</p> | |
| <p>Jade project is hosted as part of the <a href="http://orcc.sf.net">Open | |
| RVC-CAL Compiler</a> and requires it to translate the RVC-CAL standard library | |
| of video coding tools into an LLVM assembly code.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="neko_llvm_jit">LLVM JIT for Neko VM</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p><a href="http://github.com/vava/neko_llvm_jit">Neko LLVM JIT</a> | |
| replaces the standard Neko JIT with an LLVM-based implementation. While not | |
| fully complete, it is already providing a 1.5x speedup on 64-bit systems. | |
| Neko LLVM JIT requires LLVM 2.8 or later.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="crack">Crack Scripting Language</a> | |
| </div> | |
| <div class="doc_text"> | |
| <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. Crack 0.2 works with LLVM 2.7, and the forthcoming Crack 0.2.1 release | |
| builds on LLVM 2.8.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="DresdenTM">Dresden TM Compiler (DTMC)</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://tm.inf.tu-dresden.de">DTMC</a> provides support for | |
| Transactional Memory, which is an easy-to-use and efficient way to synchronize | |
| accesses to shared memory. Transactions can contain normal C/C++ code (e.g., | |
| <code>__transaction { list.remove(x); x.refCount--; }</code>) and will be executed | |
| virtually atomically and isolated from other transactions.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="Kai">Kai Programming Language</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://www.oriontransfer.co.nz/research/kai">Kai</a> (Japanese 会 for | |
| meeting/gathering) is an experimental interpreter that provides a highly | |
| extensible runtime environment and explicit control over the compilation | |
| process. Programs are defined using nested symbolic expressions, which are all | |
| parsed into first-class values with minimal intrinsic semantics. Kai can | |
| generate optimised code at run-time (using LLVM) in order to exploit the nature | |
| of the underlying hardware and to integrate with external software libraries. | |
| It is a unique exploration into world of dynamic code compilation, and the | |
| interaction between high level and low level semantics.</p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="OSL">OSL: Open Shading Language</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| <a href="http://code.google.com/p/openshadinglanguage/">OSL</a> is a shading | |
| language designed for use in physically based renderers and in particular | |
| production rendering. By using LLVM instead of the interpreter, it was able to | |
| meet its performance goals (>= C-code) while retaining the benefits of | |
| runtime specialization and a portable high-level language. | |
| </p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> | |
| <a name="whatsnew">What's New in LLVM 2.8?</a> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>This release includes a huge number of bug fixes, performance tweaks and | |
| minor improvements. Some of the major improvements and new features are listed | |
| in this section. | |
| </p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="majorfeatures">Major New Features</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM 2.8 includes several major new capabilities:</p> | |
| <ul> | |
| <li>As mentioned above, <a href="#libc++">libc++</a> and <a | |
| href="#lldb">LLDB</a> are major new additions to the LLVM collective.</li> | |
| <li>LLVM 2.8 now has pretty decent support for debugging optimized code. You | |
| should be able to reliably get debug info for function arguments, assuming | |
| that the value is actually available where you have stopped.</li> | |
| <li>A new 'llvm-diff' tool is available that does a semantic diff of .ll | |
| files.</li> | |
| <li>The <a href="#mc">MC subproject</a> has made major progress in this release. | |
| Direct .o file writing support for darwin/x86[-64] is now reliable and | |
| support for other targets and object file formats are in progress.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="coreimprovements">LLVM IR and Core Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>LLVM IR has several new features for better support of new targets and that | |
| expose new optimization opportunities:</p> | |
| <ul> | |
| <li>The <a href="LangRef.html#int_libc">memcpy, memmove, and memset</a> | |
| intrinsics now take address space qualified pointers and a bit to indicate | |
| whether the transfer is "<a href="LangRef.html#volatile">volatile</a>" or not. | |
| </li> | |
| <li>Per-instruction debug info metadata is much faster and uses less memory by | |
| using the new DebugLoc class.</li> | |
| <li>LLVM IR now has a more formalized concept of "<a | |
| href="LangRef.html#trapvalues">trap values</a>", which allow the optimizer | |
| to optimize more aggressively in the presence of undefined behavior, while | |
| still producing predictable results.</li> | |
| <li>LLVM IR now supports two new <a href="LangRef.html#linkage">linkage | |
| types</a> (linker_private_weak and linker_private_weak_def_auto) which map | |
| onto some obscure MachO concepts.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="optimizer">Optimizer Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>In addition to a large array of minor performance tweaks and bug fixes, this | |
| release includes a few major enhancements and additions to the optimizers:</p> | |
| <ul> | |
| <li>As mentioned above, the optimizer now has support for updating debug | |
| information as it goes. A key aspect of this is the new <a | |
| href="SourceLevelDebugging.html#format_common_value">llvm.dbg.value</a> | |
| intrinsic. This intrinsic represents debug info for variables that are | |
| promoted to SSA values (typically by mem2reg or the -scalarrepl passes).</li> | |
| <li>The JumpThreading pass is now much more aggressive about implied value | |
| relations, allowing it to thread conditions like "a == 4" when a is known to | |
| be 13 in one of the predecessors of a block. It does this in conjunction | |
| with the new LazyValueInfo analysis pass.</li> | |
| <li>The new RegionInfo analysis pass identifies single-entry single-exit regions | |
| in the CFG. You can play with it with the "opt -regions analyze" or | |
| "opt -view-regions" commands.</li> | |
| <li>The loop optimizer has significantly improved strength reduction and analysis | |
| capabilities. Notably it is able to build on the trap value and signed | |
| integer overflow information to optimize <= and >= loops.</li> | |
| <li>The CallGraphSCCPassManager now has some basic support for iterating within | |
| an SCC when a optimizer devirtualizes a function call. This allows inlining | |
| through indirect call sites that are devirtualized by store-load forwarding | |
| and other optimizations.</li> | |
| <li>The new <A href="Passes.html#loweratomic">-loweratomic</a> pass is available | |
| to lower atomic instructions into their non-atomic form. This can be useful | |
| to optimize generic code that expects to run in a single-threaded | |
| environment.</li> | |
| </ul> | |
| <!-- | |
| <p>In addition to these features that are done in 2.8, there is preliminary | |
| support in the release for Type Based Alias Analysis | |
| Preliminary work on TBAA but not usable in 2.8. | |
| New CorrelatedValuePropagation pass, not on by default in 2.8 yet. | |
| --> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="mc">MC Level Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p> | |
| The LLVM Machine Code (aka MC) subsystem was created to solve a number | |
| of problems in the realm of assembly, disassembly, object file format handling, | |
| and a number of other related areas that CPU instruction-set level tools work | |
| in.</p> | |
| <p>The MC subproject has made great leaps in LLVM 2.8. For example, support for | |
| directly writing .o files from LLC (and clang) now works reliably for | |
| darwin/x86[-64] (including inline assembly support) and the integrated | |
| assembler is turned on by default in Clang for these targets. This provides | |
| improved compile times among other things.</p> | |
| <ul> | |
| <li>The entire compiler has converted over to using the MCStreamer assembler API | |
| instead of writing out a .s file textually.</li> | |
| <li>The "assembler parser" is far more mature than in 2.7, supporting a full | |
| complement of directives, now supports assembler macros, etc.</li> | |
| <li>The "assembler backend" has been completed, including support for relaxation | |
| relocation processing and all the other things that an assembler does.</li> | |
| <li>The MachO file format support is now fully functional and works.</li> | |
| <li>The MC disassembler now fully supports ARM and Thumb. ARM assembler support | |
| is still in early development though.</li> | |
| <li>The X86 MC assembler now supports the X86 AES and AVX instruction set.</li> | |
| <li>Work on ELF and COFF object files and ARM target support is well underway, | |
| but isn't useful yet in LLVM 2.8. Please contact the llvmdev mailing list | |
| if you're interested in this.</li> | |
| </ul> | |
| <p>For more information, please see the <a | |
| href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the | |
| LLVM MC Project Blog Post</a>. | |
| </p> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="codegen">Target Independent Code Generator Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>We have put a significant amount of work into the code generator | |
| infrastructure, which allows us to implement more aggressive algorithms and make | |
| it run faster:</p> | |
| <ul> | |
| <li>The clang/gcc -momit-leaf-frame-pointer argument is now supported.</li> | |
| <li>The clang/gcc -ffunction-sections and -fdata-sections arguments are now | |
| supported on ELF targets (like GCC).</li> | |
| <li>The MachineCSE pass is now tuned and on by default. It eliminates common | |
| subexpressions that are exposed when lowering to machine instructions.</li> | |
| <li>The "local" register allocator was replaced by a new "fast" register | |
| allocator. This new allocator (which is often used at -O0) is substantially | |
| faster and produces better code than the old local register allocator.</li> | |
| <li>A new LLC "-regalloc=default" option is available, which automatically | |
| chooses a register allocator based on the -O optimization level.</li> | |
| <li>The common code generator code was modified to promote illegal argument and | |
| return value vectors to wider ones when possible instead of scalarizing | |
| them. For example, <3 x float> will now pass in one SSE register | |
| instead of 3 on X86. This generates substantially better code since the | |
| rest of the code generator was already expecting this.</li> | |
| <li>The code generator uses a new "COPY" machine instruction. This speeds up | |
| the code generator and eliminates the need for targets to implement the | |
| isMoveInstr hook. Also, the copyRegToReg hook was renamed to copyPhysReg | |
| and simplified.</li> | |
| <li>The code generator now has a "LocalStackSlotPass", which optimizes stack | |
| slot access for targets (like ARM) that have limited stack displacement | |
| addressing.</li> | |
| <li>A new "PeepholeOptimizer" is available, which eliminates sign and zero | |
| extends, and optimizes away compare instructions when the condition result | |
| is available from a previous instruction.</li> | |
| <li>Atomic operations now get legalized into simpler atomic operations if not | |
| natively supported, easing the implementation burden on targets.</li> | |
| <li>We have added two new bottom-up pre-allocation register pressure aware schedulers: | |
| <ol> | |
| <li>The hybrid scheduler schedules aggressively to minimize schedule length when registers are available and avoid overscheduling in high pressure situations.</li> | |
| <li>The instruction-level-parallelism scheduler schedules for maximum ILP when registers are available and avoid overscheduling in high pressure situations.</li> | |
| </ol></li> | |
| <li>The tblgen type inference algorithm was rewritten to be more consistent and | |
| diagnose more target bugs. If you have an out-of-tree backend, you may | |
| find that it finds bugs in your target description. This support also | |
| allows limited support for writing patterns for instructions that return | |
| multiple results (e.g. a virtual register and a flag result). The | |
| 'parallel' modifier in tblgen was removed, you should use the new support | |
| for multiple results instead.</li> | |
| <li>A new (experimental) "-rendermf" pass is available which renders a | |
| MachineFunction into HTML, showing live ranges and other useful | |
| details.</li> | |
| <li>The new SubRegIndex tablegen class allows subregisters to be indexed | |
| symbolically instead of numerically. If your target uses subregisters you | |
| will need to adapt to use SubRegIndex when you upgrade to 2.8.</li> | |
| <!-- SplitKit --> | |
| <li>The -fast-isel instruction selection path (used at -O0 on X86) was rewritten | |
| to work bottom-up on basic blocks instead of top down. This makes it | |
| slightly faster (because the MachineDCE pass is not needed any longer) and | |
| allows it to generate better code in some cases.</li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="x86">X86-32 and X86-64 Target Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>New features and major changes in the X86 target include: | |
| </p> | |
| <ul> | |
| <li>The X86 backend now supports holding X87 floating point stack values | |
| in registers across basic blocks, dramatically improving performance of code | |
| that uses long double, and when targeting CPUs that don't support SSE.</li> | |
| <li>The X86 backend now uses a SSEDomainFix pass to optimize SSE operations. On | |
| Nehalem ("Core i7") and newer CPUs there is a 2 cycle latency penalty on | |
| using a register in a different domain than where it was defined. This pass | |
| optimizes away these stalls.</li> | |
| <li>The X86 backend now promotes 16-bit integer operations to 32-bits when | |
| possible. This avoids 0x66 prefixes, which are slow on some | |
| microarchitectures and bloat the code on all of them.</li> | |
| <li>The X86 backend now supports the Microsoft "thiscall" calling convention, | |
| and a <a href="LangRef.html#callingconv">calling convention</a> to support | |
| <a href="#GHC">ghc</a>.</li> | |
| <li>The X86 backend supports a new "llvm.x86.int" intrinsic, which maps onto | |
| the X86 "int $42" and "int3" instructions.</li> | |
| <li>At the IR level, the <2 x float> datatype is now promoted and passed | |
| around as a <4 x float> instead of being passed and returned as an MMX | |
| vector. If you have a frontend that uses this, please pass and return a | |
| <2 x i32> instead (using bitcasts).</li> | |
| <li>When printing .s files in verbose assembly mode (the default for clang -S), | |
| the X86 backend now decodes X86 shuffle instructions and prints human | |
| readable comments after the most inscrutable of them, e.g.: | |
| <pre> | |
| insertps $113, %xmm3, %xmm0 <i># xmm0 = zero,xmm0[1,2],xmm3[1]</i> | |
| unpcklps %xmm1, %xmm0 <i># xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1]</i> | |
| pshufd $1, %xmm1, %xmm1 <i># xmm1 = xmm1[1,0,0,0]</i> | |
| </pre> | |
| </li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="ARM">ARM Target Improvements</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>New features of the ARM target include: | |
| </p> | |
| <ul> | |
| <li>The ARM backend now optimizes tail calls into jumps.</li> | |
| <li>Scheduling is improved through the new list-hybrid scheduler as well | |
| as through better modeling of structural hazards.</li> | |
| <li><a href="LangRef.html#int_fp16">Half float</a> instructions are now | |
| supported.</li> | |
| <li>NEON support has been improved to model instructions which operate onto | |
| multiple consecutive registers more aggressively. This avoids lots of | |
| extraneous register copies.</li> | |
| <li>The ARM backend now uses a new "ARMGlobalMerge" pass, which merges several | |
| global variables into one, saving extra address computation (all the global | |
| variables can be accessed via same base address) and potentially reducing | |
| register pressure.</li> | |
| <li>The ARM has received many minor improvements and tweaks which lead to | |
| substantially better performance in a wide range of different scenarios.</li> | |
| <li>The ARM NEON intrinsics have been substantially reworked to reduce | |
| redundancy and improve code generation. Some of the major changes are: | |
| <ol> | |
| <li> | |
| All of the NEON load and store intrinsics (llvm.arm.neon.vld* and | |
| llvm.arm.neon.vst*) take an extra parameter to specify the alignment in bytes | |
| of the memory being accessed. | |
| </li> | |
| <li> | |
| The llvm.arm.neon.vaba intrinsic (vector absolute difference and | |
| accumulate) has been removed. This operation is now represented using | |
| the llvm.arm.neon.vabd intrinsic (vector absolute difference) followed by a | |
| vector add. | |
| </li> | |
| <li> | |
| The llvm.arm.neon.vabdl and llvm.arm.neon.vabal intrinsics (lengthening | |
| vector absolute difference with and without accumulation) have been removed. | |
| They are represented using the llvm.arm.neon.vabd intrinsic (vector absolute | |
| difference) followed by a vector zero-extend operation, and for vabal, | |
| a vector add. | |
| </li> | |
| <li> | |
| The llvm.arm.neon.vmovn intrinsic has been removed. Calls of this intrinsic | |
| are now replaced by vector truncate operations. | |
| </li> | |
| <li> | |
| The llvm.arm.neon.vmovls and llvm.arm.neon.vmovlu intrinsics have been | |
| removed. They are now represented as vector sign-extend (vmovls) and | |
| zero-extend (vmovlu) operations. | |
| </li> | |
| <li> | |
| The llvm.arm.neon.vaddl*, llvm.arm.neon.vaddw*, llvm.arm.neon.vsubl*, and | |
| llvm.arm.neon.vsubw* intrinsics (lengthening vector add and subtract) have | |
| been removed. They are replaced by vector add and vector subtract operations | |
| where one (vaddw, vsubw) or both (vaddl, vsubl) of the operands are either | |
| sign-extended or zero-extended. | |
| </li> | |
| <li> | |
| The llvm.arm.neon.vmulls, llvm.arm.neon.vmullu, llvm.arm.neon.vmlal*, and | |
| llvm.arm.neon.vmlsl* intrinsics (lengthening vector multiply with and without | |
| accumulation and subtraction) have been removed. These operations are now | |
| represented as vector multiplications where the operands are either | |
| sign-extended or zero-extended, followed by a vector add for vmlal or a | |
| vector subtract for vmlsl. Note that the polynomial vector multiply | |
| intrinsic, llvm.arm.neon.vmullp, remains unchanged. | |
| </li> | |
| </ol> | |
| </li> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="changes">Major Changes and Removed Features</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>If you're already an LLVM user or developer with out-of-tree changes based | |
| on LLVM 2.7, this section lists some "gotchas" that you may run into upgrading | |
| from the previous release.</p> | |
| <ul> | |
| <li>The build configuration machinery changed the output directory names. It | |
| wasn't clear to many people that a "Release-Asserts" build was a release build | |
| without asserts. To make this more clear, "Release" does not include | |
| assertions and "Release+Asserts" does (likewise, "Debug" and | |
| "Debug+Asserts").</li> | |
| <li>The MSIL Backend was removed, it was unsupported and broken.</li> | |
| <li>The ABCD, SSI, and SCCVN passes were removed. These were not fully | |
| functional and their behavior has been or will be subsumed by the | |
| LazyValueInfo pass.</li> | |
| <li>The LLVM IR 'Union' feature was removed. While this is a desirable feature | |
| for LLVM IR to support, the existing implementation was half baked and | |
| barely useful. We'd really like anyone interested to resurrect the work and | |
| finish it for a future release.</li> | |
| <li>If you're used to reading .ll files, you'll probably notice that .ll file | |
| dumps don't produce #uses comments anymore. To get them, run a .bc file | |
| through "llvm-dis --show-annotations".</li> | |
| <li>Target triples are now stored in a normalized form, and all inputs from | |
| humans are expected to be normalized by Triple::normalize before being | |
| stored in a module triple or passed to another library.</li> | |
| </ul> | |
| <p>In addition, many APIs have changed in this release. Some of the major LLVM | |
| API changes are:</p> | |
| <ul> | |
| <li>LLVM 2.8 changes the internal order of operands in <a | |
| href="http://llvm.org/doxygen/classllvm_1_1InvokeInst.html"><tt>InvokeInst</tt></a> | |
| and <a href="http://llvm.org/doxygen/classllvm_1_1CallInst.html"><tt>CallInst</tt></a>. | |
| To be portable across releases, please use the <tt>CallSite</tt> class and the | |
| high-level accessors, such as <tt>getCalledValue</tt> and | |
| <tt>setUnwindDest</tt>. | |
| </li> | |
| <li> | |
| You can no longer pass use_iterators directly to cast<> (and similar), | |
| because these routines tend to perform costly dereference operations more | |
| than once. You have to dereference the iterators yourself and pass them in. | |
| </li> | |
| <li> | |
| llvm.memcpy.*, llvm.memset.*, llvm.memmove.* intrinsics take an extra | |
| parameter now ("i1 isVolatile"), totaling 5 parameters, and the pointer | |
| operands are now address-space qualified. | |
| If you were creating these intrinsic calls and prototypes yourself (as opposed | |
| to using Intrinsic::getDeclaration), you can use | |
| UpgradeIntrinsicFunction/UpgradeIntrinsicCall to be portable across releases. | |
| </li> | |
| <li> | |
| SetCurrentDebugLocation takes a DebugLoc now instead of a MDNode. | |
| Change your code to use | |
| SetCurrentDebugLocation(DebugLoc::getFromDILocation(...)). | |
| </li> | |
| <li> | |
| The <tt>RegisterPass</tt> and <tt>RegisterAnalysisGroup</tt> templates are | |
| considered deprecated, but continue to function in LLVM 2.8. Clients are | |
| strongly advised to use the upcoming <tt>INITIALIZE_PASS()</tt> and | |
| <tt>INITIALIZE_AG_PASS()</tt> macros instead. | |
| </li> | |
| <li> | |
| The constructor for the Triple class no longer tries to understand odd triple | |
| specifications. Frontends should ensure that they only pass valid triples to | |
| LLVM. The Triple::normalize utility method has been added to help front-ends | |
| deal with funky triples. | |
| </li> | |
| <li> | |
| Some APIs were renamed: | |
| <ul> | |
| <li>llvm_report_error -> report_fatal_error</li> | |
| <li>llvm_install_error_handler -> install_fatal_error_handler</li> | |
| <li>llvm::DwarfExceptionHandling -> llvm::JITExceptionHandling</li> | |
| <li>VISIBILITY_HIDDEN -> LLVM_LIBRARY_VISIBILITY</li> | |
| </ul> | |
| </li> | |
| <li> | |
| Some public headers were renamed: | |
| <ul> | |
| <li><tt>llvm/Assembly/AsmAnnotationWriter.h</tt> was renamed | |
| to <tt>llvm/Assembly/AssemblyAnnotationWriter.h</tt> | |
| </li> | |
| </ul> | |
| </ul> | |
| </div> | |
| <!--=========================================================================--> | |
| <div class="doc_subsection"> | |
| <a name="devtree_changes">Development Infrastructure Changes</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>This section lists changes to the LLVM development infrastructure. This | |
| mostly impacts users who actively work on LLVM or follow development on | |
| mainline, but may also impact users who leverage the LLVM build infrastructure | |
| or are interested in LLVM qualification.</p> | |
| <ul> | |
| <li>The default for <tt>make check</tt> is now to use | |
| the <a href="http://llvm.org/cmds/lit.html">lit</a> testing tool, which is | |
| part of LLVM itself. You can use <tt>lit</tt> directly as well, or use | |
| the <tt>llvm-lit</tt> tool which is created as part of a Makefile or CMake | |
| build (and knows how to find the appropriate tools). See the <tt>lit</tt> | |
| documentation and the <a href="http://blog.llvm.org/2009/12/lit-it.html">blog | |
| post</a>, and <a href="http://llvm.org/bugs/show_bug.cgi?id=5217">PR5217</a> | |
| for more information.</li> | |
| <li>The LLVM <tt>test-suite</tt> infrastructure has a new "simple" test format | |
| (<tt>make TEST=simple</tt>). The new format is intended to require only a | |
| compiler and not a full set of LLVM tools. This makes it useful for testing | |
| released compilers, for running the test suite with other compilers (for | |
| performance comparisons), and makes sure that we are testing the compiler as | |
| users would see it. The new format is also designed to work using reference | |
| outputs instead of comparison to a baseline compiler, which makes it run much | |
| faster and makes it less system dependent.</li> | |
| <li>Significant progress has been made on a new interface to running the | |
| LLVM <tt>test-suite</tt> (aka the LLVM "nightly tests") using | |
| the <a href="http://llvm.org/docs/lnt">LNT</a> infrastructure. The LNT | |
| interface to the <tt>test-suite</tt> brings significantly improved reporting | |
| capabilities for monitoring the correctness and generated code quality | |
| produced by LLVM over time.</li> | |
| </ul> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> | |
| <a name="knownproblems">Known Problems</a> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>This section contains significant known problems with the LLVM system, | |
| listed by component. If you run into a problem, please check the <a | |
| href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if | |
| there isn't already one.</p> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="experimental">Experimental features included with this release</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The following components of this LLVM release are either untested, known to | |
| be broken or unreliable, or are in early development. These components should | |
| not be relied on, and bugs should not be filed against them, but they may be | |
| useful to some people. In particular, if you would like to work on one of these | |
| components, please contact us on the <a | |
| href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p> | |
| <ul> | |
| <li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PIC16, SystemZ | |
| and XCore backends are experimental.</li> | |
| <li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets | |
| other than darwin-i386 and darwin-x86_64.</li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="x86-be">Known problems with the X86 back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>The X86 backend does not yet support | |
| all <a href="http://llvm.org/PR879">inline assembly that uses the X86 | |
| floating point stack</a>. It supports the 'f' and 't' constraints, but not | |
| 'u'.</li> | |
| <li>Win64 code generation wasn't widely tested. Everything should work, but we | |
| expect small issues to happen. Also, llvm-gcc cannot build the mingw64 | |
| runtime currently due to lack of support for the 'u' inline assembly | |
| constraint and for X87 floating point inline assembly.</li> | |
| <li>The X86-64 backend does not yet support the LLVM IR instruction | |
| <tt>va_arg</tt>. Currently, front-ends support variadic | |
| argument constructs on X86-64 by lowering them manually.</li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="ppc-be">Known problems with the PowerPC back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>The Linux PPC32/ABI support needs testing for the interpreter and static | |
| compilation, and lacks support for debug information.</li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="arm-be">Known problems with the ARM back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6 | |
| processors, thumb programs can crash or produce wrong | |
| results (<a href="http://llvm.org/PR1388">PR1388</a>).</li> | |
| <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested. | |
| </li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="sparc-be">Known problems with the SPARC back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not | |
| support the 64-bit SPARC ABI (-m64).</li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="mips-be">Known problems with the MIPS back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>64-bit MIPS targets are not supported yet.</li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="alpha-be">Known problems with the Alpha back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <ul> | |
| <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the | |
| appropriate nops inserted to ensure restartability.</li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="c-be">Known problems with the C back-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>The C backend has numerous problems and is not being actively maintained. | |
| Depending on it for anything serious is not advised.</p> | |
| <ul> | |
| <li><a href="http://llvm.org/PR802">The C backend has only basic support for | |
| inline assembly code</a>.</li> | |
| <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common | |
| C++ programs</a>, preventing intermixing between C++ compiled by the CBE and | |
| C++ code compiled with <tt>llc</tt> or native compilers.</li> | |
| <li>The C backend does not support all exception handling constructs.</li> | |
| <li>The C backend does not support arbitrary precision integers.</li> | |
| </ul> | |
| </div> | |
| <!-- ======================================================================= --> | |
| <div class="doc_subsection"> | |
| <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a> | |
| </div> | |
| <div class="doc_text"> | |
| <p>llvm-gcc is generally very stable for the C family of languages. The only | |
| major language feature of GCC not supported by llvm-gcc is the | |
| <tt>__builtin_apply</tt> family of builtins. However, some extensions | |
| are only supported on some targets. For example, trampolines are only | |
| supported on some targets (these are used when you take the address of a | |
| nested function).</p> | |
| <p>Fortran support generally works, but there are still several unresolved bugs | |
| in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the | |
| tools/gfortran component for details. Note that llvm-gcc is missing major | |
| Fortran performance work in the frontend and library that went into GCC after | |
| 4.2. If you are interested in Fortran, we recommend that you consider using | |
| <a href="#dragonegg">dragonegg</a> instead.</p> | |
| <p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being | |
| actively maintained. If you are interested in Ada, we recommend that you | |
| consider using <a href="#dragonegg">dragonegg</a> instead.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_section"> | |
| <a name="additionalinfo">Additional Information</a> | |
| </div> | |
| <!-- *********************************************************************** --> | |
| <div class="doc_text"> | |
| <p>A wide variety of additional information is available on the <a | |
| href="http://llvm.org">LLVM web page</a>, in particular in the <a | |
| href="http://llvm.org/docs/">documentation</a> section. The web page also | |
| contains versions of the API documentation which is up-to-date with the | |
| Subversion version of the source code. | |
| You can access versions of these documents specific to this release by going | |
| into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p> | |
| <p>If you have any questions or comments about LLVM, please feel free to contact | |
| us via the <a href="http://llvm.org/docs/#maillist"> mailing | |
| lists</a>.</p> | |
| </div> | |
| <!-- *********************************************************************** --> | |
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