-
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- <title>LLVM 2.3 Release Notes</title>
+ <title>LLVM 2.6 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.3 Release Notes</div>
-
+<div class="doc_title">LLVM 2.6 Release Notes</div>
+
<ol>
<li><a href="#intro">Introduction</a></li>
- <li><a href="#changes">Major Changes and Sub-project Status</a></li>
- <li><a href="#whatsnew">What's New?</a></li>
+ <li><a href="#subproj">Sub-project Status Update</a></li>
+ <li><a href="#externalproj">External Projects Using LLVM 2.6</a></li>
+ <li><a href="#whatsnew">What's New in LLVM 2.6?</a></li>
<li><a href="GettingStarted.html">Installation Instructions</a></li>
<li><a href="#portability">Portability and Supported Platforms</a></li>
- <li><a href="#knownproblems">Known Problems</a>
+ <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>
+ <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
</div>
-<!-- Done through Week-of-Mon-20080324.txt -->
-
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="intro">Introduction</a>
<div class="doc_text">
-<p>This document contains the release notes for the LLVM compiler
-infrastructure, release 2.3. Here we describe the status of LLVM, including
-major improvements from the previous release and any known problems. All LLVM
-releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
-releases web site</a>.</p>
+<p>This document contains the release notes for the LLVM Compiler
+Infrastructure, release 2.6. 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://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
-list</a> is a good place to send them.</p>
+href="http://mail.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
+<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 releases, please see 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.
+ llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
+-->
+
+
+<!-- Unfinished features in 2.6:
+ gcc plugin.
+ strong phi elim
+ variable debug info for optimized code
+ postalloc scheduler: anti dependence breaking, hazard recognizer?
+ metadata
+ loop dependence analysis
+ ELF Writer? How stable?
+ <li>PostRA scheduler improvements, ARM adoption (David Goodwin).</li>
+ 2.7 supports the GDB 7.0 jit interfaces for debug info.
+ 2.7 eliminates ADT/iterator.h
+ -->
+
+ <!-- for announcement email:
+ Logo web page.
+ llvm devmtg
+ compiler_rt
+ KLEE web page at klee.llvm.org
+ Many new papers added to /pubs/
+ Mention gcc plugin.
+
+ -->
<!-- *********************************************************************** -->
<div class="doc_section">
- <a name="changes">Major Changes and Sub-project Status</a>
+ <a name="subproj">Sub-project Status Update</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
+<p>
+The LLVM 2.6 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>
-<p>This is the fourteenth public release of the LLVM Compiler Infrastructure.
-It includes a large number of features and refinements from LLVM 2.2.</p>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
</div>
-<!-- Unfinished features in 2.3:
- Machine LICM
- Machine Sinking
- LegalizeDAGTypes
- -->
+<div class="doc_text">
+
+<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
+a set of new 'LLVM native' front-end technologies for the C family of languages.
+LLVM 2.6 is the first release to officially include Clang, and it provides a
+production quality C and Objective-C compiler. If you are interested in <a
+href="http://clang.llvm.org/performance.html">fast compiles</a> and
+<a href="http://clang.llvm.org/diagnostics.html">good diagnostics</a>, we
+encourage you to try it out. Clang currently compiles typical Objective-C code
+3x faster than GCC and compiles C code about 30% faster than GCC at -O0 -g
+(which is when the most pressure is on the frontend).</p>
+
+<p>In addition to supporting these languages, C++ support is also <a
+href="http://clang.llvm.org/cxx_status.html">well under way</a>, and mainline
+Clang is able to parse the libstdc++ 4.2 headers and even codegen simple apps.
+If you are interested in Clang C++ support or any other Clang feature, we
+strongly encourage you to get involved on the <a
+href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
+list</a>.</p>
+
+<p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
+
+<ul>
+<li>C and Objective-C support are now considered production quality.</li>
+<li>AuroraUX, FreeBSD and OpenBSD are now supported.</li>
+<li>Most of Objective-C 2.0 is now supported with the GNU runtime.</li>
+<li>Many many bugs are fixed and lots of features have been added.</li>
+</ul>
+</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="changes">Major Changes in LLVM 2.3</a>
+<a name="clangsa">Clang Static Analyzer</a>
</div>
<div class="doc_text">
-<p>LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with
- llvm-gcc 4.2.</p>
+<p>Previously announced in the 2.4 and 2.5 LLVM releases, the Clang project also
+includes an early stage static source code analysis tool for <a
+href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
+in C and Objective-C programs. The tool performs checks to find
+bugs that occur on a specific path within a program.</p>
+
+<p>In the LLVM 2.6 time-frame, the analyzer core has undergone several important
+improvements and cleanups and now includes a new <em>Checker</em> interface that
+is intended to eventually serve as a basis for domain-specific checks. Further,
+in addition to generating HTML files for reporting analysis results, the
+analyzer can now also emit bug reports in a structured XML format that is
+intended to be easily readable by other programs.</p>
+
+<p>The set of checks performed by the static analyzer continues to expand, and
+future plans for the tool include full source-level inter-procedural analysis
+and deeper checks such as buffer overrun detection. There are many opportunities
+to extend and enhance the static analyzer, and anyone interested in working on
+this project is encouraged to get involved!</p>
-<p>LLVM 2.3 no longer includes the <tt>llvm-upgrade</tt> tool. It was useful
- for upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a
- previous LLVM release to do this. One nice impact of this is that the LLVM
- regression test suite no longer depends on llvm-upgrade, which makes it run
- faster.</p>
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
+</div>
-<p>The <tt>llvm2cpp</tt> tool has been folded into llc, use
- <tt>llc -march=cpp</tt> instead of <tt>llvm2cpp</tt>.</p>
+<div class="doc_text">
+<p>
+The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
+a JVM and a CLI Virtual Machine (Microsoft .NET is an
+implementation of the CLI) using LLVM for static and just-in-time
+compilation.</p>
-<p>LLVM API Changes:</p>
+<p>
+VMKit version 0.26 builds with LLVM 2.6 and you can find it on its
+<a href="http://vmkit.llvm.org/releases/">web page</a>. The release includes
+bug fixes, cleanup and new features. The major changes are:</p>
<ul>
-<li>Several core LLVM IR classes have migrated to use the
- '<tt>FOOCLASS::Create(...)</tt>' pattern instead of '<tt>new
- FOOCLASS(...)</tt>' (e.g. where FOOCLASS=<tt>BasicBlock</tt>). We hope to
- standardize on <tt>FOOCLASS::Create</tt> for all IR classes in the future,
- but not all of them have been moved over yet.</li>
-<li>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to
- <a href="http://llvm.org/doxygen/classllvm_1_1IRBuilder.html">IRBuilder</a>.
- </li>
-<li>MRegisterInfo was renamed to
- <a href="http://llvm.org/doxygen/classllvm_1_1TargetRegisterInfo.html">
- TargetRegisterInfo</a>.</li>
-<li>The MappedFile class is gone, please use
- <a href="http://llvm.org/doxygen/classllvm_1_1MemoryBuffer.html">
- MemoryBuffer</a> instead.</li>
-<li>The '<tt>-enable-eh</tt>' flag to llc has been removed. Now code should
- encode whether it is safe to omit unwind information for a function by
- tagging the Function object with the '<tt>nounwind</tt>' attribute.</li>
+
+<li>A new llcj tool to generate shared libraries or executables of Java
+ files.</li>
+<li>Cooperative garbage collection. </li>
+<li>Fast subtype checking (paper from Click et al [JGI'02]). </li>
+<li>Implementation of a two-word header for Java objects instead of the original
+ three-word header. </li>
+<li>Better Java specification-compliance: division by zero checks, stack
+ overflow checks, finalization and references support. </li>
</ul>
</div>
+
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="otherprojects">Other LLVM Sub-Projects</a>
+<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
</div>
<div class="doc_text">
<p>
-The core LLVM 2.3 distribution currently consists of code from the core LLVM
-repository (which roughly contains the LLVM optimizer, code generators and
-supporting tools) and the llvm-gcc repository. In addition to this code, the
-LLVM Project includes other sub-projects that are in development. The two which
-are the most actively developed are the new <a href="#vmkit">vmkit Project</a>
-and the <a href="#clang">Clang Project</a>.
-</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.</p>
+
</div>
<!--=========================================================================-->
-<div class="doc_subsubsection">
-<a name="vmkit">vmkit</a>
+<div class="doc_subsection">
+<a name="klee">KLEE: Symbolic Execution and Automatic Test Case Generator</a>
</div>
<div class="doc_text">
<p>
-The "vmkit" project is a new addition to the LLVM family. It is an
-implementation of a JVM and a CLI Virtual Machines (Microsoft .NET is an
-implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
-
-<p>The JVM, called JnJVM, executes real-world applications such as Apache
-projects (e.g. Felix and Tomcat) and the SpecJVM98 benchmark. It uses the GNU
-Classpath project for the base classes. The CLI implementation, called N3, is
-its in early stages but can execute simple applications and the "pnetmark"
-benchmark. It uses the pnetlib project as its core library.</p>
-
-<p>The 'vmkit' VMs compare in performance with industrial and top open-source
-VMs on scientific applications. Besides the JIT, the VMs use many features of
-the LLVM framework, including the standard set of optimizations, atomic
-operations, custom function provider and memory manager for JITed methods, and
-specific virtual machine optimizations. vmkit is not an official part of LLVM
-2.3 release. It is publicly available under the LLVM license and can be
-downloaded from:
-</p>
+The new LLVM <a href="http://klee.llvm.org/">KLEE project</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 algorithms. For more
+details, please see the <a
+href="http://llvm.org/pubs/2008-12-OSDI-KLEE.html">OSDI 2008 paper</a> about
+KLEE.</p>
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
+</div>
+<div class="doc_text">
<p>
-<tt>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</tt>
+The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
+gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
+<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (dragonegg.so)
+that is loaded by gcc at runtime. It uses the new gcc plugin architecture to
+disable the GCC optimizers and code generators, and schedule the LLVM optimizers
+and code generators (or direct output of LLVM IR) instead. Currently only Linux
+and Darwin are supported, and only on x86-32 and x86-64. It should be easy to
+add additional unix-like architectures and other processor families. In theory
+it should be possible to use <a href="http://dragonegg.llvm.org/">DragonEgg</a>
+with any language supported by gcc, however only C and Fortran work well for the
+moment. Ada and C++ work to some extent, while Java, Obj-C and Obj-C++ are so
+far entirely untested. Since gcc-4.5 has not yet been released, neither has
+<a href="http://dragonegg.llvm.org/">DragonEgg</a>. To build
+<a href="http://dragonegg.llvm.org/">DragonEgg</a> you will need to check out the
+development versions of <a href="http://gcc.gnu.org/svn.html/"> gcc</a>,
+<a href="http://llvm.org/docs/GettingStarted.html#checkout">llvm</a> and
+<a href="http://dragonegg.llvm.org/">DragonEgg</a> from their respective
+subversion repositories, and follow the instructions in the
+<a href="http://dragonegg.llvm.org/">DragonEgg</a> README.
</p>
</div>
+
<!--=========================================================================-->
-<div class="doc_subsubsection">
-<a name="clang">Clang</a>
+<div class="doc_subsection">
+<a name="mc">llvm-mc: Machine Code Toolkit</a>
</div>
<div class="doc_text">
+<p>
+The LLVM Machine Code (MC) Toolkit project is a (very early) effort to build
+better tools for dealing with machine code, object file formats, etc. The idea
+is to be able to generate most of the target specific details of assemblers and
+disassemblers from existing LLVM target .td files (with suitable enhancements),
+and to build infrastructure for reading and writing common object file formats.
+One of the first deliverables is to build a full assembler and integrate it into
+the compiler, which is predicted to substantially reduce compile time in some
+scenarios.
+</p>
-<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
-a set of new 'LLVM native' front-end technologies for the LLVM optimizer
-and code generator. Clang is continuing to make major strides forward in all
-areas. Its C and Objective-C parsing support is very solid, and the code
-generation support is far enough along to build many C applications. While not
-yet production quality, it is progressing very nicely. In addition, C++
-front-end work has started to make significant progress.</p>
-
-<p>At this point, Clang is most useful if you are interested in source-to-source
-transformations (such as refactoring) and other source-level tools for C and
-Objective-C. Clang now also includes tools for turning C code into pretty HTML,
-and includes a new <a href="http://clang.llvm.org/StaticAnalysis.html">static
-analysis tool</a> in development. This tool is automatically focused on finding
-bugs in C and Objective-C code.</p>
+<p>In the LLVM 2.6 timeframe, the MC framework has grown to the point where it
+can reliably parse and pretty print (with some encoding information) a
+darwin/x86 .s file successfully, and has the very early phases of a Mach-O
+assembler in progress. Beyond the MC framework itself, major refactoring of the
+LLVM code generator has started. The idea is to make the code generator reason
+about the code it is producing in a much more semantic way, rather than a
+textual way. For example, the code generator now uses MCSection objects to
+represent section assignments, instead of text strings that print to .section
+directives.</p>
+
+<p>MC is an early and ongoing project that will hopefully continue to lead to
+many improvements in the code generator and build infrastructure useful for many
+other situations.
+</p>
-</div>
+</div>
<!-- *********************************************************************** -->
<div class="doc_section">
- <a name="whatsnew">What's New?</a>
+ <a name="externalproj">External Open Source Projects Using LLVM 2.6</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
-<p>LLVM 2.3 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>
+<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 2.6.</p>
</div>
+
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="majorfeatures">Major New Features</a>
+<a name="Rubinius">Rubinius</a>
</div>
<div class="doc_text">
+<p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
+for running Ruby code which strives to write as much of the core class
+implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
+uses LLVM to optimize and compile ruby code down to machine code. Techniques
+such as type feedback, method inlining, and uncommon traps are all used to
+remove dynamism from ruby execution and increase performance.</p>
+
+<p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
+a counter based JIT, type feedback and speculative method inlining.
+</p>
-<p>LLVM 2.3 includes several major new capabilities:</p>
+</div>
-<ul>
-<li><p>The biggest change in LLVM 2.3 is Multiple Return Value (MRV) support.
- MRVs allow LLVM IR to directly represent functions that return multiple
- values without having to pass them "by reference" in the LLVM IR. This
- allows a front-end to generate more efficient code, as MRVs are generally
- returned in registers if a target supports them. See the <a
- href="LangRef.html#i_getresult">LLVM IR Reference</a> for more details.</p>
-
- <p>MRVs are fully supported in the LLVM IR, but are not yet fully supported in
- on all targets. However, it is generally safe to return up to 2 values from
- a function: most targets should be able to handle at least that. MRV
- support is a critical requirement for X86-64 ABI support, as X86-64 requires
- the ability to return multiple registers from functions, and we use MRVs to
- accomplish this in a direct way.</p></li>
-
-<li><p>LLVM 2.3 includes a complete reimplementation of the "<tt>llvmc</tt>"
- tool. It is designed to overcome several problems with the original
- <tt>llvmc</tt> and to provide a superset of the features of the
- '<tt>gcc</tt>' driver.</p>
-
-<p>The main features of <tt>llvmc2</tt> are:
- <ul>
- <li>Extended handling of command line options and smart rules for
- dispatching them to different tools.</li>
- <li>Flexible (and extensible) rules for defining different tools.</li>
- <li>The different intermediate steps performed by tools are represented
- as edges in the abstract graph.</li>
- <li>The 'language' for driver behavior definition is tablegen and thus
- it's relatively easy to add new features.</li>
- <li>The definition of driver is transformed into set of C++ classes, thus
- no runtime interpretation is needed.</li>
- </ul></p>
- </li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="macruby">MacRuby</a>
+</div>
-<li><p>LLVM 2.3 includes a completely rewritten interface for <a
- href="LinkTimeOptimization.html">Link Time Optimization</a>. This interface
- is written in C, which allows for easier integration with C code bases, and
- incorporates improvements we learned about from the first incarnation of the
- interface.</p></li>
+<div class="doc_text">
-<li><p>The <a href="tutorial/LangImpl1.html">Kaleidoscope tutorial</a> now
- includes a "port" of the tutorial that <a
- href="tutorial/OCamlLangImpl1.html">uses the Ocaml bindings</a> to implement
- the Kaleidoscope language.</p></li>
+<p>
+<a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
+core Mac OS X technologies, such as the Objective-C common runtime and garbage
+collector and the CoreFoundation framework. It is principally developed by
+Apple and aims at enabling the creation of full-fledged Mac OS X applications.
+</p>
-</ul>
+<p>
+MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
+expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
+handling.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
+<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 0.31 and later have been tested and are known to work with
+LLVM 2.6 (and continue to work with older LLVM releases >= 2.3 as well).
+</p>
+</div>
+
-<p>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end, and includes support
-for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="ldc">LLVM D Compiler</a>
+</div>
+<div class="doc_text">
<p>
-<ul>
-<li>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
-front-end. Objective-C now works very well on Mac OS/X.</li>
+<a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
+the D Programming Language using the LLVM optimizer and code generator.
+The LDC project works great with the LLVM 2.6 release. General improvements in
+this
+cycle have included new inline asm constraint handling, better debug info
+support, general bug fixes and better x86-64 support. This has allowed
+some major improvements in LDC, getting it much closer to being as
+fully featured as the original DMD compiler from DigitalMars.
+</p>
+</div>
-<li>Fortran EQUIVALENCEs are now supported by the gfortran front-end.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="RoadsendPHP">Roadsend PHP</a>
+</div>
-<li>llvm-gcc 4.2 includes many other fixes which improve conformance with the
-relevant parts of the GCC testsuite.</li>
+<div class="doc_text">
+<p>
+<a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
+source implementation of the PHP programming
+language that uses LLVM for its optimizer, JIT and static compiler. This is a
+reimplementation of an earlier project that is now based on LLVM.</p>
+</div>
-</ul></p>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="UnladenSwallow">Unladen Swallow</a>
+</div>
+<div class="doc_text">
+<p>
+<a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
+branch of <a href="http://python.org/">Python</a> intended to be fully
+compatible and significantly faster. It uses LLVM's optimization passes and JIT
+compiler.</p>
</div>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="llvm-lua">llvm-lua</a>
+</div>
+
+<div class="doc_text">
+<p>
+<a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
+and static compiling support to the Lua VM. Lua bytecode is analyzed to
+remove type checks, then LLVM is used to compile the bytecode down to machine
+code.</p>
+</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="coreimprovements">LLVM Core Improvements</a>
+<a name="icedtea">IcedTea Java Virtual Machine Implementation</a>
</div>
<div class="doc_text">
-<p>New features include:
+<p>
+<a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
+harness to build OpenJDK using only free software build tools and to provide
+replacements for the not-yet free parts of OpenJDK. One of the extensions that
+IcedTea provides is a new JIT compiler named <a
+href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
+to provide native code generation without introducing processor-dependent
+code.
</p>
+</div>
+
+
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="whatsnew">What's New in LLVM 2.6?</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 2.6 includes several major new capabilities:</p>
<ul>
-<li>LLVM IR now directly represents "common" linkage, instead of representing it
-as a form of weak linkage.</li>
+<li>New <a href="#compiler-rt">compiler-rt</a>, <A href="#klee">KLEE</a>
+ and <a href="#mc">machine code toolkit</a> sub-projects.</li>
+<li>Debug information now includes line numbers when optimizations are enabled.
+ This allows statistical sampling tools like OProfile and Shark to map
+ samples back to source lines.</li>
+<li>LLVM now includes new experimental backends to support the MSP430, SystemZ
+ and BlackFin architectures.</li>
+<li>LLVM supports a new <a href="GoldPlugin.html">Gold Linker Plugin</a> which
+ enables support for <a href="LinkTimeOptimization.html">transparent
+ link-time optimization</a> on ELF targets when used with the Gold binutils
+ linker.</li>
+<li>LLVM now supports doing optimization and code generation on multiple
+ threads. Please see the <a href="ProgrammersManual.html#threading">LLVM
+ Programmer's Manual</a> for more information.</li>
+<li>LLVM now has experimental support for <a
+ href="http://nondot.org/~sabre/LLVMNotes/EmbeddedMetadata.txt">embedded
+ metadata</a> in LLVM IR, though the implementation is not guaranteed to be
+ final and the .bc file format may change in future releases. Debug info
+ does not yet use this format in LLVM 2.6.</li>
+</ul>
-<li>LLVM IR now has support for atomic operations, and this functionality can
-be accessed through the llvm-gcc "__sync_synchronize",
-"__sync_val_compare_and_swap", and related builtins. Support for atomics are
-available in the Alpha, X86, X86-64, and PowerPC backends.</li>
+</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>
-<li>The C and Ocaml bindings have extended to cover pass managers, several
-transformation passes, iteration over the LLVM IR, target data, and parameter
-attribute lists.</li>
+<ul>
+<li>The <a href="LangRef.html#i_add">add</a>, <a
+ href="LangRef.html#i_sub">sub</a> and <a href="LangRef.html#i_mul">mul</a>
+ instructions have been split into integer and floating point versions (like
+ divide and remainder), introducing new <a
+ href="LangRef.html#i_fadd">fadd</a>, <a href="LangRef.html#i_fsub">fsub</a>,
+ and <a href="LangRef.html#i_fmul">fmul</a> instructions.</li>
+<li>The <a href="LangRef.html#i_add">add</a>, <a
+ href="LangRef.html#i_sub">sub</a> and <a href="LangRef.html#i_mul">mul</a>
+ instructions now support optional "nsw" and "nuw" bits which indicate that
+ the operation is guaranteed to not overflow (in the signed or
+ unsigned case, respectively). This gives the optimizer more information and
+ can be used for things like C signed integer values, which are undefined on
+ overflow.</li>
+<li>The <a href="LangRef.html#i_sdiv">sdiv</a> instruction now supports an
+ optional "exact" flag which indicates that the result of the division is
+ guaranteed to have a remainder of zero. This is useful for optimizing pointer
+ subtraction in C.</li>
+<li>The <a href="LangRef.html#i_getelementptr">getelementptr</a> instruction now
+ supports arbitrary integer index values for array/pointer indices. This
+ allows for better code generation on 16-bit pointer targets like PIC16.</li>
+<li>The <a href="LangRef.html#i_getelementptr">getelementptr</a> instruction now
+ supports an "inbounds" optimization hint that tells the optimizer that the
+ pointer is guaranteed to be within its allocated object.</li>
+<li>LLVM now support a series of new linkage types for global values which allow
+ for better optimization and new capabilities:
+ <ul>
+ <li><a href="LangRef.html#linkage_linkonce">linkonce_odr</a> and
+ <a href="LangRef.html#linkage_weak">weak_odr</a> have the same linkage
+ semantics as the non-"odr" linkage types. The difference is that these
+ linkage types indicate that all definitions of the specified function
+ are guaranteed to have the same semantics. This allows inlining
+ templates functions in C++ but not inlining weak functions in C,
+ which previously both got the same linkage type.</li>
+ <li><a href="LangRef.html#linkage_available_externally">available_externally
+ </a> is a new linkage type that gives the optimizer visibility into the
+ definition of a function (allowing inlining and side effect analysis)
+ but that does not cause code to be generated. This allows better
+ optimization of "GNU inline" functions, extern templates, etc.</li>
+ <li><a href="LangRef.html#linkage_linker_private">linker_private</a> is a
+ new linkage type (which is only useful on Mac OS X) that is used for
+ some metadata generation and other obscure things.</li>
+ </ul></li>
+<li>Finally, target-specific intrinsics can now return multiple values, which
+ is useful for modeling target operations with multiple results.</li>
</ul>
-
+
</div>
<!--=========================================================================-->
<div class="doc_text">
-<p>In addition to a huge array of bug fixes and minor performance tweaks, the
-LLVM 2.3 optimizers support a few major enhancements:</p>
+<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><p>Loop index set splitting on by default.
-This transformation hoists conditions from loop bodies and reduces a loop's
-iteration space to improve performance. For example,</p>
+<li>The <a href="Passes.html#scalarrepl">Scalar Replacement of Aggregates</a>
+ pass has many improvements that allow it to better promote vector unions,
+ variables which are memset, and much more strange code that can happen to
+ do bitfield accesses to register operations. An interesting change is that
+ it now produces "unusual" integer sizes (like i1704) in some cases and lets
+ other optimizers clean things up.</li>
+<li>The <a href="Passes.html#loop-reduce">Loop Strength Reduction</a> pass now
+ promotes small integer induction variables to 64-bit on 64-bit targets,
+ which provides a major performance boost for much numerical code. It also
+ promotes shorts to int on 32-bit hosts, etc. LSR now also analyzes pointer
+ expressions (e.g. getelementptrs), as well as integers.</li>
+<li>The <a href="Passes.html#gvn">GVN</a> pass now eliminates partial
+ redundancies of loads in simple cases.</li>
+<li>The <a href="Passes.html#inline">Inliner</a> now reuses stack space when
+ inlining similar arrays from multiple callees into one caller.</li>
+<li>LLVM includes a new experimental Static Single Information (SSI)
+ construction pass.</li>
-<pre>
-for (i = LB; i < UB; ++i)
- if (i <= NV)
- LOOP_BODY
-</pre>
+</ul>
-<p>is transformed into:</p>
+</div>
-<pre>
-NUB = min(NV+1, UB)
-for (i = LB; i < NUB; ++i)
- LOOP_BODY
-</pre>
-</li>
-<li>LLVM now includes a new <tt>memcpy</tt> optimization pass which removes
-dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and performs
-return slot optimization. The LLVM optimizer now notices long sequences of
-consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li>
-
-<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
-<tt>memset</tt> is now more aggressive.</li>
-
-<li>The Aggressive Dead Code Elimination (ADCE) optimization has been rewritten
-to make it both faster and safer in the presence of code containing infinite
-loops. Some of its prior functionality has been factored out into the loop
-deletion pass, which <em>is</em> safe for infinite loops. The new ADCE pass is
-no longer based on control dependence, making it run faster.</li>
-
-<li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm
- functions for C-based languages, has been rewritten to be a FunctionPass
- instead a ModulePass. This allows it to be run more often and to be
- included at -O1 in llvm-gcc. It was also extended to include more
- optimizations and several corner case bugs were fixed.</li>
-
-<li>LLVM now includes a simple 'Jump Threading' pass, which attempts to simplify
- conditional branches using information about predecessor blocks, simplifying
- the control flow graph. This pass is pretty basic at this point, but
- catches some important cases and provides a foundation to build on.</li>
-
-<li>Several corner case bugs which could lead to deleting volatile memory
- accesses have been fixed.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="executionengine">Interpreter and JIT Improvements</a>
+</div>
+
+<div class="doc_text">
-<li>Several optimizations have been sped up, leading to faster code generation
- with the same code quality.</li>
-
+<ul>
+<li>LLVM has a new "EngineBuilder" class which makes it more obvious how to
+ set up and configure an ExecutionEngine (a JIT or interpreter).</li>
+<li>The JIT now supports generating more than 16M of code.</li>
+<li>When configured with <tt>--with-oprofile</tt>, the JIT can now inform
+ OProfile about JIT'd code, allowing OProfile to get line number and function
+ name information for JIT'd functions.</li>
+<li>When "libffi" is available, the LLVM interpreter now uses it, which supports
+ calling almost arbitrary external (natively compiled) functions.</li>
+<li>Clients of the JIT can now register a 'JITEventListener' object to receive
+ callbacks when the JIT emits or frees machine code. The OProfile support
+ uses this mechanism.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="codegen">Code Generator Improvements</a>
+<a name="codegen">Target Independent Code Generator Improvements</a>
</div>
<div class="doc_text">
-<p>We 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 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 code generator now has support for carrying information about memory
- references throughout the entire code generation process, via the
- <a href="http://llvm.org/doxygen/classllvm_1_1MachineMemOperand.html">
- MachineMemOperand</a> class. In the future this will be used to improve
- both pre-pass and post-pass scheduling, and to improve compiler-debugging
- output.</li>
-
-<li>The target-independent code generator infrastructure now uses LLVM's
- <a href="http://llvm.org/doxygen/classllvm_1_1APInt.html">APInt</a>
- class to handle integer values, which allows it to support integer types
- larger than 64 bits. Note that support for such types is also dependent on
- target-specific support. Use of APInt is also a step toward support for
- non-power-of-2 integer sizes.</li>
-
-<li>LLVM 2.3 includes several compile time speedups for code with large basic
- blocks, particularly in the instruction selection phase, register
- allocation, scheduling, and tail merging/jump threading.</li>
-<li>Several improvements which make llc's <tt>--view-sunit-dags</tt>
- visualization of scheduling dependency graphs easier to understand.</li>
-
-<li>The code generator allows targets to write patterns that generate subreg
- references directly in .td files now.</li>
-
-<li><tt>memcpy</tt> lowering in the backend is more aggressive, particularly for
- <tt>memcpy</tt> calls introduced by the code generator when handling
- pass-by-value structure argument copies.</li>
-
-<li>Inline assembly with multiple register results now returns those results
- directly in the appropriate registers, rather than going through memory.
- Inline assembly that uses constraints like "ir" with immediates now use the
- 'i' form when possible instead of always loading the value in a register.
- This saves an instruction and reduces register use.</li>
-
-<li>Added support for PIC/GOT style tail calls on x86/32 and initial support
- for tail calls on PowerPC 32 (it may also work on ppc64 but not
- thoroughly tested).</li>
+<li>The <tt>llc -asm-verbose</tt> option (exposed from llvm-gcc as <tt>-dA</tt>
+ and clang as <tt>-fverbose-asm</tt> or <tt>-dA</tt>) now adds a lot of
+ useful information in comments to
+ the generated .s file. This information includes location information (if
+ built with <tt>-g</tt>) and loop nest information.</li>
+<li>The code generator now supports a new MachineVerifier pass which is useful
+ for finding bugs in targets and codegen passes.</li>
+<li>The Machine LICM is now enabled by default. It hoists instructions out of
+ loops (such as constant pool loads, loads from read-only stubs, vector
+ constant synthesization code, etc.) and is currently configured to only do
+ so when the hoisted operation can be rematerialized.</li>
+<li>The Machine Sinking pass is now enabled by default. This pass moves
+ side-effect free operations down the CFG so that they are executed on fewer
+ paths through a function.</li>
+<li>The code generator now performs "stack slot coloring" of register spills,
+ which allows spill slots to be reused. This leads to smaller stack frames
+ in cases where there are lots of register spills.</li>
+<li>The register allocator has many improvements to take better advantage of
+ commutable operations, various spiller peephole optimizations, and can now
+ coalesce cross-register-class copies.</li>
+<li>Tblgen now supports multiclass inheritance and a number of new string and
+ list operations like <tt>!(subst)</tt>, <tt>!(foreach)</tt>, <tt>!car</tt>,
+ <tt>!cdr</tt>, <tt>!null</tt>, <tt>!if</tt>, <tt>!cast</tt>.
+ These make the .td files more expressive and allow more aggressive factoring
+ of duplication across instruction patterns.</li>
+<li>Target-specific intrinsics can now be added without having to hack VMCore to
+ add them. This makes it easier to maintain out-of-tree targets.</li>
+<li>The instruction selector is better at propagating information about values
+ (such as whether they are sign/zero extended etc.) across basic block
+ boundaries.</li>
+<li>The SelectionDAG datastructure has new nodes for representing buildvector
+ and <a href="http://llvm.org/PR2957">vector shuffle</a> operations. This
+ makes operations and pattern matching more efficient and easier to get
+ right.</li>
+<li>The Prolog/Epilog Insertion Pass now has experimental support for performing
+ the "shrink wrapping" optimization, which moves spills and reloads around in
+ the CFG to avoid doing saves on paths that don't need them.</li>
+<li>LLVM includes new experimental support for writing ELF .o files directly
+ from the compiler. It works well for many simple C testcases, but doesn't
+ support exception handling, debug info, inline assembly, etc.</li>
+<li>Targets can now specify register allocation hints through
+ <tt>MachineRegisterInfo::setRegAllocationHint</tt>. A regalloc hint consists
+ of hint type and physical register number. A hint type of zero specifies a
+ register allocation preference. Other hint type values are target specific
+ which are resolved by <tt>TargetRegisterInfo::ResolveRegAllocHint</tt>. An
+ example is the ARM target which uses register hints to request that the
+ register allocator provide an even / odd register pair to two virtual
+ registers.</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 of the X86 target include:
+</p>
+
+<ul>
+
+<li>SSE 4.2 builtins are now supported.</li>
+<li>GCC-compatible soft float modes are now supported, which are typically used
+ by OS kernels.</li>
+<li>X86-64 now models implicit zero extensions better, which allows the code
+ generator to remove a lot of redundant zexts. It also models the 8-bit "H"
+ registers as subregs, which allows them to be used in some tricky
+ situations.</li>
+<li>X86-64 now supports the "local exec" and "initial exec" thread local storage
+ model.</li>
+<li>The vector forms of the <a href="LangRef.html#i_icmp">icmp</a> and <a
+ href="LangRef.html#i_fcmp">fcmp</a> instructions now select to efficient
+ SSE operations.</li>
+<li>Support for the win64 calling conventions have improved. The primary
+ missing feature is support for varargs function definitions. It seems to
+ work well for many win64 JIT purposes.</li>
+<li>The X86 backend has preliminary support for <a
+ href="CodeGenerator.html#x86_memory">mapping address spaces to segment
+ register references</a>. This allows you to write GS or FS relative memory
+ accesses directly in LLVM IR for cases where you know exactly what you're
+ doing (such as in an OS kernel). There are some known problems with this
+ support, but it works in simple cases.</li>
+<li>The X86 code generator has been refactored to move all global variable
+ reference logic to one place
+ (<tt>X86Subtarget::ClassifyGlobalReference</tt>) which
+ makes it easier to reason about.</li>
+
+</ul>
+
+</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="x86specific">X86/X86-64 Specific Improvements</a>
+<a name="pic16">PIC16 Target Improvements</a>
</div>
<div class="doc_text">
-<p>New target-specific features include:
+<p>New features of the PIC16 target include:
</p>
<ul>
-<li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the
- area of passing and returning structures by value. llvm-gcc compiled code
- now interoperates very well on X86-64 systems with other compilers.</li>
+<li>Support for floating-point, indirect function calls, and
+ passing/returning aggregate types to functions.
+<li>The code generator is able to generate debug info into output COFF files.
+<li>Support for placing an object into a specific section or at a specific
+ address in memory.</li>
+</ul>
-<li>Support for Win64 was added. This includes code generation itself, JIT
- support and necessary changes to llvm-gcc.</li>
+<p>Things not yet supported:</p>
-<li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and
- the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins. Various
- generic vector operations (insert/extract/shuffle) are much more efficient
- when SSE 4.1 is enabled. The JIT automatically takes advantage of these
- instructions, but llvm-gcc must be explicitly told to use them, e.g. with
- <tt>-march=penryn</tt>.</li>
+<ul>
+<li>Variable arguments.</li>
+<li>Interrupts/programs.</li>
+</ul>
-<li>The X86 backend now does a number of optimizations that aim to avoid
- converting numbers back and forth from SSE registers to the X87 floating
- point stack.</li>
+</div>
-<li>The X86 backend supports stack realignment, which is particularly useful for
- vector code on OS's without 16-byte aligned stacks.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="ARM">ARM Target Improvements</a>
+</div>
-<li>The X86 backend now supports the "sseregparm" options in GCC, which allow
- functions to be tagged as passing floating point values in SSE
- registers.</li>
+<div class="doc_text">
+<p>New features of the ARM target include:
+</p>
-<li>Trampolines (taking the address of a nested function) now work on
- Linux/X86-64.</li>
+<ul>
-<li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch
- instructions instead of being ignored.</li>
+<li>Preliminary support for processors, such as the Cortex-A8 and Cortex-A9,
+that implement version v7-A of the ARM architecture. The ARM backend now
+supports both the Thumb2 and Advanced SIMD (Neon) instruction sets.</li>
-<li>128-bit integers are now supported on X86-64 targets.</li>
+<li>The AAPCS-VFP "hard float" calling conventions are also supported with the
+<tt>-float-abi=hard</tt> flag.</li>
-<li>The register allocator can now rematerialize PIC-base computations.</li>
+<li>The ARM calling convention code is now tblgen generated instead of resorting
+ to C++ code.</li>
+</ul>
+
+<p>These features are still somewhat experimental
+and subject to change. The Neon intrinsics, in particular, may change in future
+releases of LLVM. ARMv7 support has progressed a lot on top of tree since 2.6
+branched.</p>
+
+
+</div>
-<li>The "t" and "f" inline assembly constraints for the X87 floating point stack
- now work. However, the "u" constraint is still not fully supported.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="OtherTarget">Other Target Specific Improvements</a>
+</div>
+<div class="doc_text">
+<p>New features of other targets include:
+</p>
+
+<ul>
+<li>Mips now supports O32 Calling Convention.</li>
+<li>Many improvements to the 32-bit PowerPC SVR4 ABI (used on powerpc-linux)
+ support, lots of bugs fixed.</li>
+<li>Added support for the 64-bit PowerPC SVR4 ABI (used on powerpc64-linux).
+ Needs more testing.</li>
</ul>
-
+
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="targetspecific">Other Target Specific Improvements</a>
+<a name="newapis">New Useful APIs</a>
</div>
<div class="doc_text">
-<p>New target-specific features include:
+
+<p>This release includes a number of new APIs that are used internally, which
+ may also be useful for external clients.
</p>
<ul>
-<li>The LLVM C backend now supports vector code.</li>
+<li>New <a href="http://llvm.org/doxygen/PrettyStackTrace_8h-source.html">
+ <tt>PrettyStackTrace</tt> class</a> allows crashes of llvm tools (and applications
+ that integrate them) to provide more detailed indication of what the
+ compiler was doing at the time of the crash (e.g. running a pass).
+ At the top level for each LLVM tool, it includes the command line arguments.
+ </li>
+<li>New <a href="http://llvm.org/doxygen/StringRef_8h-source.html">StringRef</a>
+ and <a href="http://llvm.org/doxygen/Twine_8h-source.html">Twine</a> classes
+ make operations on character ranges and
+ string concatenation to be more efficient. <tt>StringRef</tt> is just a <tt>const
+ char*</tt> with a length, <tt>Twine</tt> is a light-weight rope.</li>
+<li>LLVM has new <tt>WeakVH</tt>, <tt>AssertingVH</tt> and <tt>CallbackVH</tt>
+ classes, which make it easier to write LLVM IR transformations. <tt>WeakVH</tt>
+ is automatically drops to null when the referenced <tt>Value</tt> is deleted,
+ and is updated across a <tt>replaceAllUsesWith</tt> operation.
+ <tt>AssertingVH</tt> aborts the program if the
+ referenced value is destroyed while it is being referenced. <tt>CallbackVH</tt>
+ is a customizable class for handling value references. See <a
+ href="http://llvm.org/doxygen/ValueHandle_8h-source.html">ValueHandle.h</a>
+ for more information.</li>
+<li>The new '<a href="http://llvm.org/doxygen/Triple_8h-source.html">Triple
+ </a>' class centralizes a lot of logic that reasons about target
+ triples.</li>
+<li>The new '<a href="http://llvm.org/doxygen/ErrorHandling_8h-source.html">
+ llvm_report_error()</a>' set of APIs allows tools to embed the LLVM
+ optimizer and backend and recover from previously unrecoverable errors.</li>
+<li>LLVM has new abstractions for <a
+ href="http://llvm.org/doxygen/Atomic_8h-source.html">atomic operations</a>
+ and <a href="http://llvm.org/doxygen/RWMutex_8h-source.html">reader/writer
+ locks</a>.</li>
+<li>LLVM has new <a href="http://llvm.org/doxygen/SourceMgr_8h-source.html">
+ <tt>SourceMgr</tt> and <tt>SMLoc</tt> classes</a> which implement caret
+ diagnostics and basic include stack processing for simple parsers. It is
+ used by tablegen, llvm-mc, the .ll parser and FileCheck.</li>
</ul>
-
+
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="otherimprovements">Other Improvements and New Features</a>
</div>
+<div class="doc_text">
+<p>Other miscellaneous features include:</p>
+
+<ul>
+<li>LLVM now includes a new internal '<a
+ href="http://llvm.org/cmds/FileCheck.html">FileCheck</a>' tool which allows
+ writing much more accurate regression tests that run faster. Please see the
+ <a href="TestingGuide.html#FileCheck">FileCheck section of the Testing
+ Guide</a> for more information.</li>
+<li>LLVM profile information support has been significantly improved to produce
+correct use counts, and has support for edge profiling with reduced runtime
+overhead. Combined, the generated profile information is both more correct and
+imposes about half as much overhead (2.6. from 12% to 6% overhead on SPEC
+CPU2000).</li>
+<li>The C bindings (in the llvm/include/llvm-c directory) include many newly
+ supported APIs.</li>
+<li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005
+ programming language.</li>
+
+<li>The LLVMC driver has several new features:
+ <ul>
+ <li>Dynamic plugins now work on Windows.</li>
+ <li>New option property: init. Makes possible to provide default values for
+ options defined in plugins (interface to <tt>cl::init</tt>).</li>
+ <li>New example: Skeleton, shows how to create a standalone LLVMC-based
+ driver.</li>
+ <li>New example: mcc16, a driver for the PIC16 toolchain.</li>
+ </ul>
+</li>
+
+</ul>
+
+</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="otherimprovements">Other Improvements</a>
+<a name="changes">Major Changes and Removed Features</a>
</div>
<div class="doc_text">
-<p>New features include:
-</p>
+
+<p>If you're already an LLVM user or developer with out-of-tree changes based
+on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading
+from the previous release.</p>
<ul>
-<li>LLVM now builds with GCC 4.3.</li>
-<li>Bugpoint now supports running custom scripts (with the <tt>-run-custom</tt>
- option) to determine how to execute the command and whether it is making
- forward process.</li>
+<li>The Itanium (IA64) backend has been removed. It was not actively supported
+ and had bitrotted.</li>
+<li>The BigBlock register allocator has been removed, it had also bitrotted.</li>
+<li>The C Backend (<tt>-march=c</tt>) is no longer considered part of the LLVM release
+criteria. We still want it to work, but no one is maintaining it and it lacks
+support for arbitrary precision integers and other important IR features.</li>
+
+<li>All LLVM tools now default to overwriting their output file, behaving more
+ like standard unix tools. Previously, this only happened with the '<tt>-f</tt>'
+ option.</li>
+<li>LLVM build now builds all libraries as .a files instead of some
+ libraries as relinked .o files. This requires some APIs like
+ InitializeAllTargets.h.
+ </li>
</ul>
-
+
+
+<p>In addition, many APIs have changed in this release. Some of the major LLVM
+API changes are:</p>
+
+<ul>
+<li>All uses of <tt>hash_set</tt> and <tt>hash_map</tt> have been removed from
+ the LLVM tree and the wrapper headers have been removed.</li>
+<li>The llvm/Streams.h and <tt>DOUT</tt> member of Debug.h have been removed. The
+ <tt>llvm::Ostream</tt> class has been completely removed and replaced with
+ uses of <tt>raw_ostream</tt>.</li>
+<li>LLVM's global uniquing tables for <tt>Type</tt>s and <tt>Constant</tt>s have
+ been privatized into members of an <tt>LLVMContext</tt>. A number of APIs
+ now take an <tt>LLVMContext</tt> as a parameter. To smooth the transition
+ for clients that will only ever use a single context, the new
+ <tt>getGlobalContext()</tt> API can be used to access a default global
+ context which can be passed in any and all cases where a context is
+ required.
+<li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
+<li>The <tt>Add</tt>, <tt>Sub</tt> and <tt>Mul</tt> operators are no longer
+ overloaded for floating-point types. Floating-point addition, subtraction
+ and multiplication are now represented with new operators <tt>FAdd</tt>,
+ <tt>FSub</tt> and <tt>FMul</tt>. In the <tt>IRBuilder</tt> API,
+ <tt>CreateAdd</tt>, <tt>CreateSub</tt>, <tt>CreateMul</tt> and
+ <tt>CreateNeg</tt> should only be used for integer arithmetic now;
+ <tt>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt> and
+ <tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
+<li>The <tt>DynamicLibrary</tt> class can no longer be constructed, its functionality has
+ moved to static member functions.</li>
+<li><tt>raw_fd_ostream</tt>'s constructor for opening a given filename now
+ takes an extra <tt>Force</tt> argument. If <tt>Force</tt> is set to
+ <tt>false</tt>, an error will be reported if a file with the given name
+ already exists. If <tt>Force</tt> is set to <tt>true</tt>, the file will
+ be silently truncated (which is the behavior before this flag was
+ added).</li>
+<li><tt>SCEVHandle</tt> no longer exists, because reference counting is no
+ longer done for <tt>SCEV*</tt> objects, instead <tt>const SCEV*</tt>
+ should be used.</li>
+
+<li>Many APIs, notably <tt>llvm::Value</tt>, now use the <tt>StringRef</tt>
+and <tt>Twine</tt> classes instead of passing <tt>const char*</tt>
+or <tt>std::string</tt>, as described in
+the <a href="ProgrammersManual.html#string_apis">Programmer's Manual</a>. Most
+clients should be unaffected by this transition, unless they are used to
+<tt>Value::getName()</tt> returning a string. Here are some tips on updating to
+2.6:
+ <ul>
+ <li><tt>getNameStr()</tt> is still available, and matches the old
+ behavior. Replacing <tt>getName()</tt> calls with this is an safe option,
+ although more efficient alternatives are now possible.</li>
+
+ <li>If you were just relying on <tt>getName()</tt> being able to be sent to
+ a <tt>std::ostream</tt>, consider migrating
+ to <tt>llvm::raw_ostream</tt>.</li>
+
+ <li>If you were using <tt>getName().c_str()</tt> to get a <tt>const
+ char*</tt> pointer to the name, you can use <tt>getName().data()</tt>.
+ Note that this string (as before), may not be the entire name if the
+ name contains embedded null characters.</li>
+
+ <li>If you were using <tt>operator +</tt> on the result of <tt>getName()</tt> and
+ treating the result as an <tt>std::string</tt>, you can either
+ use <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
+ could move to a <tt>Twine</tt> based design.</li>
+
+ <li><tt>isName()</tt> should be replaced with comparison
+ against <tt>getName()</tt> (this is now efficient).
+ </ul>
+</li>
+
+<li>The registration interfaces for backend Targets has changed (what was
+previously <tt>TargetMachineRegistry</tt>). For backend authors, see the <a
+href="WritingAnLLVMBackend.html#TargetRegistration">Writing An LLVM Backend</a>
+guide. For clients, the notable API changes are:
+ <ul>
+ <li><tt>TargetMachineRegistry</tt> has been renamed
+ to <tt>TargetRegistry</tt>.</li>
+
+ <li>Clients should move to using the <tt>TargetRegistry::lookupTarget()</tt>
+ function to find targets.</li>
+ </ul>
+</li>
+</ul>
+
</div>
+
+
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="portability">Portability and Supported Platforms</a>
<p>LLVM is known to work on the following platforms:</p>
<ul>
-<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
- (and probably other unix-like systems).</li>
-<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
- 64-bit modes.</li>
+<li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
+ Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
+ systems).</li>
+<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
+ and 64-bit modes.</li>
<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
support is available for native builds with Visual C++).</li>
-<li>Sun UltraSPARC workstations running Solaris 10.</li>
+<li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</li>
<li>Alpha-based machines running Debian GNU/Linux.</li>
-<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
</ul>
<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
<div class="doc_text">
-<p>This section contains all known problems with the LLVM system, listed by
-component. As new problems are discovered, they will be added to these
-sections. If you run into a problem, please check the <a
+<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>
+<ul>
+<li>The llvm-gcc bootstrap will fail with some versions of binutils (e.g. 2.15)
+ with a message of "<tt><a href="http://llvm.org/PR5004">Error: can not do 8
+ byte pc-relative relocation</a></tt>" when building C++ code. We intend to
+ fix this on mainline, but a workaround for 2.6 is to upgrade to binutils
+ 2.17 or later.</li>
+
+<li>LLVM will not correctly compile on Solaris and/or OpenSolaris
+using the stock GCC 3.x.x series 'out the box',
+See: <a href="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
+However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
+for x86/x86-64 has been made available from the third party AuroraUX Project
+that has been meticulously tested for bootstrapping LLVM & Clang.</li>
+</ul>
+
</div>
<!-- ======================================================================= -->
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
<ul>
-<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
-<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
- value for this option.</li>
+<li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430 and SystemZ backends are
+ experimental.</li>
+<li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
+ supported value for this option. The ELF writer is experimental.</li>
+<li>The implementation of Andersen's Alias Analysis has many known bugs.</li>
</ul>
</div>
<li>The X86 backend generates inefficient floating point code when configured
to generate code for systems that don't have SSE2.</li>
<li>Win64 code generation wasn't widely tested. Everything should work, but we
- expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
- currently due
+ expect small issues to happen. Also, llvm-gcc cannot build the mingw64
+ runtime currently due
to <a href="http://llvm.org/PR2255">several</a>
- <a href="http://llvm.org/PR2257">bugs</a> in FP stackifier
+ <a href="http://llvm.org/PR2257">bugs</a> and 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, the llvm-gcc and front-ends support variadic
+ argument constructs on X86-64 by lowering them manually.</li>
</ul>
</div>
<div class="doc_text">
<ul>
+<li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
+and not well tested. Some features may not work at all, and the code quality
+may be poor in some cases.</li>
<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>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
</li>
-<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
- execute
-programs compiled with LLVM. Please use more recent versions of QEMU.</li>
</ul>
</div>
<div class="doc_text">
<ul>
-<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
+<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 class="doc_subsection">
- <a name="alpha-be">Known problems with the Alpha back-end</a>
+ <a name="mips-be">Known problems with the MIPS 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>
-
+<li>64-bit MIPS targets are not supported yet.</li>
</ul>
+
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="ia64-be">Known problems with the IA64 back-end</a>
+ <a name="alpha-be">Known problems with the Alpha back-end</a>
</div>
<div class="doc_text">
<ul>
-<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
-made where the argument is not 16-byte aligned, as required on IA64. (Strictly
-speaking this is not a bug in the IA64 back-end; it will also be encountered
-when building C++ programs using the C back-end.)</li>
-
-<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
-ABI compliant layout of v-tables</a>. In particular, it just stores function
-pointers instead of function descriptors in the vtable. This bug prevents
-mixing C++ code compiled with LLVM with C++ objects compiled by other C++
-compilers.</li>
-
-<li>There are a few ABI violations which will lead to problems when mixing LLVM
-output with code built with other compilers, particularly for floating-point
-programs.</li>
-
-<li>Defining vararg functions is not supported (but calling them is OK).</li>
+<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
+appropriate nops inserted to ensure restartability.</li>
-<li>The Itanium backend has bitrotted somewhat.</li>
</ul>
-
</div>
<!-- ======================================================================= -->
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 llc or native compilers.</li>
+ 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>
<a name="c-fe">Known problems with the llvm-gcc C front-end</a>
</div>
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">Bugs</div>
-
<div class="doc_text">
-<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
-Optimization</a> on most platforms "out-of-the-box". Please inquire on the
-llvmdev mailing list if you are interested.</p>
-
<p>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
itself, Qt, Mozilla, etc.</p>
<ul>
-<li>Exception handling works well on the X86 and PowerPC targets, including
-X86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is
-supported on X86-64 linux, but that is disabled by default in this release.</li>
+<li>Exception handling works well on the X86 and PowerPC targets. Currently
+ only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
</ul>
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
+</div>
+
+<div class="doc_text">
+<ul>
+<li>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.</li>
+</ul>
+</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
</div>
<div class="doc_text">
-The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
-technology and problems should be expected.
+The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
+technology, and problems should be expected.
<ul>
<li>The Ada front-end currently only builds on X86-32. This is mainly due
-to lack of trampoline support (pointers to nested functions) on other platforms,
-
however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
+to lack of trampoline support (pointers to nested functions) on other platforms.
+
However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
which does support trampolines.</li>
<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
-Workaround: configure with --disable-bootstrap.</li>
-<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
-fail (c380004 also fails with gcc-4.2 mainline). When built at -O3, the
-<a href="http://llvm.org/PR2421">cxg2021</a> ACATS test also fails.</li>
-<li>Some gcc specific Ada tests continue to crash the compiler. The testsuite
-reports most tests as having failed even though they pass.</li>
-<li>The -E binder option (exception backtraces)
+This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
+exception handling, which is used internally by the compiler.
+Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
+<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
+and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
+(c380004 also fails with gcc-4.2 mainline).
+If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
+causes the compiler to go into an infinite loop, using up all system memory.</li>
+<li>Some GCC specific Ada tests continue to crash the compiler.</li>
+<li>The <tt>-E</tt> binder option (exception backtraces)
<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
-crashing if an exception is raised. Workaround: do not use -E.</li>
+crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
or finish at a non-byte offset</a> in a record. Workaround: do not pack records
or use representation clauses that result in a field of a non-discrete type
</ul>
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="ocaml-bindings">Known problems with the O'Caml bindings</a>
+</div>
+
+<div class="doc_text">
+
+<p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
+<tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
+<tt>Llvm.Linkage.Link_once</tt> will be correct. If you need any of the other linkage
+modes, you'll have to write an external C library in order to expose the
+functionality. This has been fixed in the trunk.</p>
+</div>
+
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="additionalinfo">Additional Information</a>
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