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diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html index bdaba71b74..95866dd625 100644 --- a/docs/ReleaseNotes.html +++ b/docs/ReleaseNotes.html @@ -4,17 +4,17 @@ <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <link rel="stylesheet" href="llvm.css" type="text/css"> - <title>LLVM 2.5 Release Notes</title> + <title>LLVM 2.6 Release Notes</title> </head> <body> -<div class="doc_title">LLVM 2.5 Release Notes</div> +<div class="doc_title">LLVM 2.6 Release Notes</div> <ol> <li><a href="#intro">Introduction</a></li> <li><a href="#subproj">Sub-project Status Update</a></li> - <li><a href="#externalproj">External Projects Using LLVM 2.5</a></li> - <li><a href="#whatsnew">What's New in LLVM 2.5?</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> @@ -34,7 +34,7 @@ <div class="doc_text"> <p>This document contains the release notes for the LLVM Compiler -Infrastructure, release 2.5. Here we describe the status of LLVM, including +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> @@ -51,25 +51,37 @@ 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> - -<!-- Unfinished features in 2.5: - Machine LICM - Machine Sinking - target-specific intrinsics - gold lto plugin - pre-alloc splitter, strong phi elim - <tt>llc -enable-value-prop</tt>, propagation of value info - (sign/zero ext info) from one MBB to another - debug info for optimized code - interpreter + libffi + + +<!-- +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? - -initial support for debug line numbers when optimization enabled, not useful in - 2.5 but will be for 2.6. - + 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. + --> <!-- *********************************************************************** --> @@ -80,12 +92,11 @@ initial support for debug line numbers when optimization enabled, not useful in <div class="doc_text"> <p> -The LLVM 2.5 distribution currently consists of code from the core LLVM -repository —which roughly includes the LLVM optimizers, 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 <a href="#clang">Clang -Project</a> and the <a href="#vmkit">VMKit Project</a>. +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> @@ -99,37 +110,30 @@ Project</a> and the <a href="#vmkit">VMKit Project</a>. <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 LLVM optimizer and -code generator. While Clang is not included in the LLVM 2.5 release, it is -continuing to make major strides forward in all areas. Its C and Objective-C -parsing and code generation support is now very solid. For example, it is -capable of successfully building many real-world applications for X86-32 -and X86-64, -including the <a href="http://wiki.freebsd.org/BuildingFreeBSDWithClang">FreeBSD -kernel</a> and <a href="http://gcc.gnu.org/gcc-4.2/">gcc 4.2</a>. C++ is also -making <a href="http://clang.llvm.org/cxx_status.html">incredible progress</a>, -and work on templates has recently started. If you are -interested in fast compiles and good diagnostics, we encourage you to try it out -by <a href="http://clang.llvm.org/get_started.html">building from mainline</a> -and reporting any issues you hit to the <a +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 2.5 time-frame, the Clang team has made many improvements:</p> +<p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p> <ul> -<li>Clang now has a new driver, which is focused on providing a GCC-compatible - interface.</li> -<li>The X86-64 ABI is now supported, including support for the Apple - 64-bit Objective-C runtime and zero cost exception handling.</li> -<li>Precompiled header support is now implemented.</li> -<li>Objective-C support is significantly improved beyond LLVM 2.4, supporting - many features, such as Objective-C Garbage Collection.</li> -<li>Variable length arrays are now fully supported.</li> -<li>C99 designated initializers are now fully supported.</li> -<li>Clang now includes all major compiler headers, including a - redesigned <i>tgmath.h</i> and several more intrinsic headers.</li> -<li>Many many bugs are fixed and many features have been added.</li> +<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> @@ -140,19 +144,18 @@ list</a>.</p> <div class="doc_text"> -<p>Previously announced in the last LLVM release, the Clang project also +<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 a growing set of checks to find +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 2.5 time-frame there have been many significant improvements to -the analyzer's core path simulation engine and machinery for generating -path-based bug reports to end-users. Particularly noteworthy improvements -include experimental support for full field-sensitivity and reasoning about heap -objects as well as an improved value-constraints subengine that does a much -better job of reasoning about inequality relationships (e.g., <tt>x > 2</tt>) -between variables and constants. +<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 @@ -170,44 +173,191 @@ this project is encouraged to get involved!</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 Machines (Microsoft .NET is an -implementation of the CLI) using the Just-In-Time compiler of LLVM.</p> +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>Following LLVM 2.5, VMKit has its second release that you can find on its -<a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes +<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>Ahead of Time compiler: compiles .class files to llvm .bc. VMKit uses this -functionality to native compile the standard classes (e.g. java.lang.String). -Users can compile AoT .class files into dynamic libraries and run them with the -help of VMKit.</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> -<li>New exception model: the dwarf exception model is very slow for -exception-intensive applications, so the JVM has had a new implementation of -exceptions which check at each function call if an exception happened. There is -a low performance penalty on applications without exceptions, but it is a big -gain for exception-intensive applications. For example the jack benchmark in -Spec JVM98 is 6x faster (performance gain of 83%).</li> +</ul> +</div> -<li>User-level management of thread stacks, so that thread local data access -at runtime is fast and portable. </li> -<li>Implementation of biased locking for faster object synchronizations at -runtime.</li> +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a> +</div> -<li>New support for OSX/X64, Linux/X64 (with the Boehm GC) and Linux/ppc32.</li> +<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> -</ul> +<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_subsection"> +<a name="klee">KLEE: Symbolic Execution and Automatic Test Case Generator</a> </div> +<div class="doc_text"> +<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> +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_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>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 class="doc_section"> - <a name="externalproj">External Projects Using LLVM 2.5</a> + <a name="externalproj">External Open Source Projects Using LLVM 2.6</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 2.6.</p> +</div> + + +<!--=========================================================================--> +<div class="doc_subsection"> +<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> + +</div> + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="macruby">MacRuby</a> +</div> + +<div class="doc_text"> + +<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> + +<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="pure">Pure</a> @@ -224,12 +374,8 @@ 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>In addition to the usual algebraic data structures, Pure also has -MATLAB-style matrices in order to support numeric computations and signal -processing in an efficient way. Pure is mainly aimed at mathematical -applications right now, but it has been designed as a general purpose language. -The dynamic interpreter environment and the C interface make it possible to use -it as a kind of functional scripting language for many application areas. +<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> @@ -243,11 +389,11 @@ it as a kind of functional scripting language for many application areas. <p> <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 2.5 release. General improvements in +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 bugfixes, and better x86-64 support. This has allowed -some major improvements in LDC, getting us much closer to being as +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> @@ -258,142 +404,160 @@ fully featured as the original DMD compiler from DigitalMars. </div> <div class="doc_text"> -<p><a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open +<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 +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> - -<!-- *********************************************************************** --> -<div class="doc_section"> - <a name="whatsnew">What's New in LLVM 2.5?</a> +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="UnladenSwallow">Unladen Swallow</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> +<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="majorfeatures">Major New Features</a> +<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> -<p>LLVM 2.5 includes several major new capabilities:</p> +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="icedtea">IcedTea Java Virtual Machine Implementation</a> +</div> -<ul> -<li>LLVM 2.5 includes a brand new <a -href="http://en.wikipedia.org/wiki/XCore">XCore</a> backend.</li> +<div class="doc_text"> +<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> -<li>llvm-gcc now generally supports the GFortran front-end, and the precompiled -release binaries now support Fortran, even on Mac OS/X.</li> -<li>CMake is now used by the <a href="GettingStartedVS.html">LLVM build process -on Windows</a>. It automatically generates Visual Studio project files (and -more) from a set of simple text files. This makes it much easier to -maintain. In time, we'd like to standardize on CMake for everything.</li> -<li>LLVM 2.5 now uses (and includes) Google Test for unit testing.</li> +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="whatsnew">What's New in LLVM 2.6?</a> +</div> +<!-- *********************************************************************** --> -<li>The LLVM native code generator now supports arbitrary precision integers. -Types like <tt>i33</tt> have long been valid in the LLVM IR, but were previously -only supported by the interpreter. Note that the C backend still does not -support these.</li> +<div class="doc_text"> -<li>LLVM 2.5 no longer uses 'bison,' so it is easier to build on Windows.</li> -</ul> +<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="llvm-gcc">llvm-gcc 4.2 Improvements</a> +<a name="majorfeatures">Major New Features</a> </div> <div class="doc_text"> -<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC -front-ends and driver with the LLVM optimizer and code generator. It currently -includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p> +<p>LLVM 2.6 includes several major new capabilities:</p> <ul> -<li>In this release, the GCC inliner is completely disabled. Previously the GCC -inliner was used to handle always-inline functions and other cases. This caused -problems with code size growth, and it is completely disabled in this -release.</li> - -<li>llvm-gcc (and LLVM in general) now support code generation for stack -canaries, which is an effective form of <a -href="http://en.wikipedia.org/wiki/Stack-smashing_protection">buffer overflow -protection</a>. llvm-gcc supports this with the <tt>-fstack-protector</tt> -command line option (just like GCC). In LLVM IR, you can request code -generation for stack canaries with function attributes. -</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> </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 that are used by our existing front-ends and -can be useful if you are writing a front-end for LLVM:</p> +<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#i_shufflevector">shufflevector</a> instruction -has been generalized to allow different shuffle mask width than its input -vectors. This allows you to use shufflevector to combine two -"<4 x float>" vectors into a "<8 x float>" for example.</li> - -<li>LLVM IR now supports new intrinsics for computing and acting on <a -href="LangRef.html#int_overflow">overflow of integer operations</a>. This allows -efficient code generation for languages that must trap or throw an exception on -overflow. While these intrinsics work on all targets, they only generate -efficient code on X86 so far.</li> - -<li>LLVM IR now supports a new <a href="LangRef.html#linkage">private -linkage</a> type to produce labels that are stripped by the assembler before it -produces a .o file (thus they are invisible to the linker).</li> - -<li>LLVM IR supports two new attributes for better alias analysis. The <a -href="LangRef.html#paramattrs">noalias</a> attribute can now be used on the -return value of a function to indicate that it returns new memory (e.g. -'malloc', 'calloc', etc). -The new <a href="LangRef.html#paramattrs">nocapture</a> attribute can be used -on pointer arguments to indicate that the function does not return the pointer, -store it in an object that outlives the call, or let the value of the pointer -escape from the function in any other way. -Note that it is the pointer itself that must not escape, not the value it -points to: loading a value out of the pointer is perfectly fine. -Many standard library functions (e.g. 'strlen', 'memcpy') have this property. -<!-- The simplifylibcalls pass applies these attributes to standard libc functions. --> -</li> - -<li>The parser for ".ll" files in lib/AsmParser is now completely rewritten as a -recursive descent parser. This parser produces better error messages (including -caret diagnostics), is less fragile (less likely to crash on strange things), -does not leak memory, is more efficient, and eliminates LLVM's last use of the -'bison' tool.</li> - -<li>Debug information representation and manipulation internals have been - consolidated to use a new set of classes in - <tt>llvm/Analysis/DebugInfo.h</tt>. These routines are more - efficient, robust, and extensible and replace the older mechanisms. - llvm-gcc, clang, and the code generator now use them to create and process - debug information.</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 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> @@ -405,27 +569,53 @@ does not leak memory, is more efficient, and eliminates LLVM's last use of the <div class="doc_text"> -<p>In addition to a large array of bug fixes and minor performance tweaks, this +<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>The loop optimizer now improves floating point induction variables in -several ways, including adding shadow induction variables to avoid -"integer <-> floating point" conversions in loops when safe.</li> +<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> -<li>The "-mem2reg" pass is now much faster on code with large basic blocks.</li> +</ul> + +</div> -<li>The "-jump-threading" pass is more powerful: it is iterative - and handles threading based on values with fully and partially redundant - loads.</li> -<li>The "-memdep" memory dependence analysis pass (used by GVN and memcpyopt) is - both faster and more aggressive.</li> +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="executionengine">Interpreter and JIT Improvements</a> +</div> -<li>The "-scalarrepl" scalar replacement of aggregates pass is more aggressive - about promoting unions to registers.</li> +<div class="doc_text"> +<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> @@ -442,33 +632,55 @@ infrastructure, which allows us to implement more aggressive algorithms and make it run faster:</p> <ul> -<li>The <a href="WritingAnLLVMBackend.html">Writing an LLVM Compiler -Backend</a> document has been greatly expanded and is substantially more -complete.</li> - -<li>The SelectionDAG type legalization logic has been completely rewritten, is -now more powerful (it supports arbitrary precision integer types for example), -and is more correct in several corner cases. The type legalizer converts -operations on types that are not natively supported by the target machine into -equivalent code sequences that only use natively supported types. The old type -legalizer is still available (for now) and will be used if -<tt>-disable-legalize-types</tt> is passed to the code generator. -</li> -<li>The code generator now supports widening illegal vectors to larger legal -ones (for example, converting operations on <3 x float> to work on -<4 x float>) which is very important for common graphics -applications.</li> - -<li>The assembly printers for each target are now split out into their own -libraries that are separate from the main code generation logic. This reduces -the code size of JIT compilers by not requiring them to be linked in.</li> - -<li>The 'fast' instruction selection path (used at -O0 and for fast JIT - compilers) now supports accelerating codegen for code that uses exception - handling constructs.</li> - -<li>The optional PBQP register allocator now supports register coalescing.</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</ |