<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.
-->
<!-- 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_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 — 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>.
+repository (which roughly includes the LLVM optimizers, code generators
+and supporting tools), the Clang repository and the llvm-gcc repository. In
+addition to this code, the LLVM Project includes other sub-projects that are in
+development. Here we include updates on these subprojects.
</p>
</div>
<div class="doc_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 2.6 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 2.6 time-frame, the Clang team has made many improvements:</p>
<ul>
-<li>Something wonderful!</li>
-<li>AuroraUX / FreeBSD & OpenBSD Toolchain support.</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>
<div class="doc_text">
-<p>Previously announced in the 2.4 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 2.6 time-frame there have been many significant improvements to
-XYZ.</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
<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 2.6, VMKit has its XYZ 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>Something wonderful!</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="compiler-rt">compiler-rt: Compiler Runtime Library</a>
+</div>
+
+<div class="doc_text">
+<p>
+The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
+is a simple library that provides an implementation of the low-level
+target-specific hooks required by code generation and other runtime components.
+For example, when compiling for a 32-bit target, converting a double to a 64-bit
+unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
+function. The compiler-rt library provides highly optimized implementations of
+this and other low-level routines (some are 3x faster than the equivalent
+libgcc routines).</p>
+
+<p>
+All of the code in the compiler-rt project is available under the standard LLVM
+License, a "BSD-style" license.</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.
+DragonEgg is a shared library (llvm.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. 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.
+</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 2.6</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>
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>
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>
</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_subsection">
-<a name="Unladen Swallow">Unladen Swallow</a>
+<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
+<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 class="doc_subsection">
-<a name="Rubinius">Rubinius</a>
+<a name="llvm-lua">llvm-lua</a>
</div>
<div class="doc_text">
-<p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is a new virtual
-machine for Ruby. It leverages LLVM to dynamically compile Ruby code down to
-machine code using LLVM's JIT.</p>
+<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_section">
<a name="whatsnew">What's New in LLVM 2.6?</a>
<div class="doc_text">
-<p>This release includes a huge number of bug fixes, performance tweaks, and
+<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>
<!--=========================================================================-->
<p>LLVM 2.6 includes several major new capabilities:</p>
<ul>
-<li>Something wonderful!</li>
-<li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005 programming language.</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="llvm-gcc">llvm-gcc 4.2 Improvements</a>
+<a name="coreimprovements">LLVM IR and Core Improvements</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 IR has several new features for better support of new targets and that
+expose new optimization opportunities:</p>
<ul>
-<li>Something wonderful!</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 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_subsection">
-<a name="coreimprovements">LLVM IR and Core Improvements</a>
+<a name="optimizer">Optimizer 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>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>Something wonderful!</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>
+
</ul>
</div>
+
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="optimizer">Optimizer Improvements</a>
+<a name="executionengine">Interpreter and JIT Improvements</a>
</div>
<div class="doc_text">
-<p>In addition to a large array of bug fixes and minor performance tweaks, this
-release includes a few major enhancements and additions to the optimizers:</p>
-
<ul>
-
-<li>Something wonderful!</li>
-
+<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 --with-oprofile, 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>
<ul>
-<li>Something wonderful!</li>
+<li>The <tt>llc -asm-verbose</tt> option (exposed from llvm-gcc and clang as
+ <tt>-fverbose-asm</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 !(subst), !(foreach), !car, !cdr, !null, !if, !cast.
+ 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
+ MachineRegisterInfo::setRegAllocationHint. 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 TargetRegisterInfo::ResolveRegAllocHint. 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>
<ul>
-<li>Something wonderful!</li>
+<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>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>
+</li>
</ul>
</div>
</p>
<ul>
-<li>Something wonderful!</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>
<p>Things not yet supported:</p>
<ul>
-<li>Floating point.</li>
-<li>Passing/returning aggregate types to and from functions.</li>
<li>Variable arguments.</li>
-<li>Indirect function calls.</li>
<li>Interrupts/programs.</li>
-<li>Debug info.</li>
</ul>
</div>
<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. The
-AAPCS-VFP "hard float" calling conventions are also supported with the
-<tt>-float-abi=hard</tt> flag. These features are still somewhat experimental
-and subject to change. The Neon intrinsics, in particular, may change in future
-releases of LLVM.
+supports both the Thumb2 and Advanced SIMD (Neon) instruction sets.</li>
+
+<li>The AAPCS-VFP "hard float" calling conventions are also supported with the
+<tt>-float-abi=hard</tt> flag.</li>
+
+<li>The ARM calling convention code is now tblgen generated instead of resorting
+ to C++ code.</li>
</li>
+
+
+<p>These features are still somewhat experimental
+and subject to change. The Neon intrinsics, in particular, may change in future
+releases of LLVM.</p>
+
</ul>
</div>
+<!--=========================================================================-->
+<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="llvmc">Improvements in LLVMC</a>
+<a name="newapis">New Useful APIs</a>
</div>
<div class="doc_text">
-<p>New features include:</p>
+
+<p>This release includes a number of new APIs that are used internally, which
+ may also be useful for external clients.
+</p>
<ul>
-<li>Something wonderful!</li>
+<li>New <a href="http://llvm.org/doxygen/PrettyStackTrace_8h-source.html">
+ PrettyStackTrace classes</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. StringRef is just a <tt>const
+ char*</tt> with a length, Twine is a light-weight rope.</li>
+<li>LLVM has new WeakVH, AssertingVH and CallbackVH classes, which make it
+ easier to write LLVM IR transformations. WeakVH is automatically drops to
+ null when the referenced Value is deleted, and is updated across a
+ replaceAllUsesWith operation. AssertingVH aborts the program if the
+ referenced value is destroyed while it is being referenced. CallbackVH 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">
+ SourceMgr and SMLoc 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 cl::init).</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>
from the previous release.</p>
<ul>
-
-<li>Something horrible!</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 (-march=c) 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 '-f'
+ 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>
API changes are:</p>
<ul>
+<li>All uses of hash_set and hash_map have been removed from the LLVM tree and
+ the wrapper headers have been removed.</li>
+<li>The llvm/Streams.h and DOUT member of Debug.h have been removed. The
+ llvm::Ostream class has been completely removed and replaced with uses of
+ raw_ostream.</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
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,
+<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>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>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt> and
<tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
<li>The DynamicLibrary class can no longer be constructed, its functionality has
moved to static member functions.</li>
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:
+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,
<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 containts embedded null characters.</li>
+ name contains embedded null characters.</li>
<li>If you were using operator plus on the result of <tt>getName()</tt> and
treating the result as an <tt>std::string</tt>, you can either
- uses <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
+ 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
</li>
<li>The registration interfaces for backend Targets has changed (what was
-previously TargetMachineRegistry). For backend authors, see the <a href="WritingAnLLVMBackend.html#TargetRegistration">Writing An LLVM Backend</a> guide. For clients, the notable API changes are:
+previously TargetMachineRegistry). 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>
function to find targets.</li>
</ul>
</li>
-
-<li>llvm-dis now fails if output file exists, instead of dumping to stdout.
-FIXME: describe any other tool changes due to the raw_fd_ostream change. FIXME:
-This is not an API change, maybe there should be a tool changes section?</li>
-<li>temporarely due to Context API change passes should call doInitialization()
-method of the pass they inherit from, otherwise Context is NULL.
-FIXME: remove this entry when this is no longer needed.<li>
</ul>
</div>
<ul>
<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>
+ 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>
+ 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>
using the stock GCC 3.x.x series 'out the box',
See: <a href="#brokengcc">Broken versions of GCC and other tools</a>.
However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
-for x86/x64 has been made available from the third party AuroraUX Project
-that has been meticulously tested for bootstrapping LLVM & Clang.</li>
+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, Alpha, SPU, MIPS, and PIC16 backends are experimental.</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.</li>
+ 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>
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>
-<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 O32 ABI is not fully supported.</li>
<li>64-bit MIPS targets are not supported yet.</li>
</ul>
<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
<div class="doc_text">
<ul>
<li>Fortran support generally works, but there are still several unresolved bugs
- in Bugzilla. Please see the tools/gfortran component for details.</li>
+ in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
+ tools/gfortran component for details.</li>
</ul>
</div>
projects / oota-llvm.git / blobdiff