<h1>LLVM 3.0 Release Notes</h1>
-<img align=right src="http://llvm.org/img/DragonSmall.png"
- width="136" height="136" alt="LLVM Dragon Logo">
+<div>
+<img style="float:right" src="http://llvm.org/img/DragonSmall.png"
+ width="136" height="136" alt="LLVM Dragon Logo">
+</div>
<ol>
<li><a href="#intro">Introduction</a></li>
<p>This document contains the release notes for the LLVM Compiler
Infrastructure, release 3.0. Here we describe the status of LLVM, including
- major improvements from the previous release and significant known problems.
+ major improvements from the previous release, improvements in various
+ subprojects of LLVM, and some of the current users of the code.
All LLVM releases may be downloaded from
the <a href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
<a href="http://llvm.org/releases/">releases page</a>.</p>
</div>
-
-<!-- Features that need text if they're finished for 3.1:
- ARM EHABI
- combiner-aa?
- strong phi elim
- loop dependence analysis
- CorrelatedValuePropagation
- lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
- -->
-
+
+
<!-- *********************************************************************** -->
<h2>
<a name="subproj">Sub-project Status Update</a>
<p>The LLVM 3.0 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
+ supporting tools), and the Clang 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>
provides a modular, library-based architecture that makes it suitable for
creating or integrating with other development tools. Clang is considered a
production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
- (32- and 64-bit), and for darwin/arm targets.</p>
+ (32- and 64-bit), and for Darwin/ARM targets.</p>
<p>In the LLVM 3.0 time-frame, the Clang team has made many improvements:</p>
-
<ul>
<li>Greatly improved support for building C++ applications, with greater
stability and better diagnostics.</li>
-
+
<li><a href="http://clang.llvm.org/cxx_status.html">Improved support</a> for
the <a href="http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50372">C++
- 2011</a> standard, including implementations of non-static data member
- initializers, alias templates, delegating constructors, the range-based
- for loop, and implicitly-generated move constructors and move assignment
+ 2011</a> standard (aka "C++'0x"), including implementations of non-static data member
+ initializers, alias templates, delegating constructors, range-based
+ for loops, and implicitly-generated move constructors and move assignment
operators, among others.</li>
<li>Implemented support for some features of the upcoming C1x standard,
including static assertions and generic selections.</li>
-
+
<li>Better detection of include and linking paths for system headers and
libraries, especially for Linux distributions.</li>
- <li>Implemented support
- for <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">Automatic
- Reference Counting</a> for Objective-C.</li>
+ <li>Several improvements to Objective-C support, including:
+
+ <ul>
+ <li><a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">
+ Automatic Reference Counting</a> (ARC) and an improved memory model
+ cleanly separating object and C memory.</li>
+
+ <li>A migration tool for moving manual retain/release code to ARC</li>
+
+ <li>Better support for data hiding, allowing instance variables to be
+ declared in implementation contexts or class extensions</li>
+ <li>Weak linking support for Objective-C classes</li>
+ <li>Improved static type checking by inferring the return type of methods
+ such as +alloc and -init.</li>
+ </ul>
+
+ Some new Objective-C features require either the Mac OS X 10.7 / iOS 5
+ Objective-C runtime, or version 1.6 or later of the GNUstep Objective-C
+ runtime version.</li>
<li>Implemented a number of optimizations in <tt>libclang</tt>, the Clang C
interface, to improve the performance of code completion and the mapping
from source locations to abstract syntax tree nodes.</li>
</ul>
+<p>For more details about the changes to Clang since the 2.9 release, see the
+<a href="http://clang.llvm.org/docs/ReleaseNotes.html">Clang release notes</a>
+</p>
+
-
<p>If Clang rejects your code but another compiler accepts it, please take a
look at the <a href="http://clang.llvm.org/compatibility.html">language
compatibility</a> guide to make sure this is not intentional or a known
<div>
<p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
<a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
- optimizers and code generators with LLVM's. Currently it requires a patched
- version of gcc-4.5. The plugin can target the x86-32 and x86-64 processor
- families and has been used successfully on the Darwin, FreeBSD and Linux
- platforms. The Ada, C, C++ and Fortran languages work well. The plugin is
- capable of compiling plenty of Obj-C, Obj-C++ and Java but it is not known
- whether the compiled code actually works or not!</p>
+ optimizers and code generators with LLVM's. It works with gcc-4.5 or gcc-4.6,
+ targets the x86-32 and x86-64 processor families, and has been successfully
+ used on the Darwin, FreeBSD, KFreeBSD, Linux and OpenBSD platforms. It fully
+ supports Ada, C, C++ and Fortran. It has partial support for Go, Java, Obj-C
+ and Obj-C++.</p>
<p>The 3.0 release has the following notable changes:</p>
-<ul>
-<!--
-<li></li>
--->
+ <ul>
+ <li>GCC version 4.6 is now fully supported.</li>
+
+ <li>Patching and building GCC is no longer required: the plugin should work
+ with your system GCC (version 4.5 or 4.6; on Debian/Ubuntu systems the
+ gcc-4.5-plugin-dev or gcc-4.6-plugin-dev package is also needed).</li>
+
+ <li>The <tt>-fplugin-arg-dragonegg-enable-gcc-optzns</tt> option, which runs
+ GCC's optimizers as well as LLVM's, now works much better. This is the
+ option to use if you want ultimate performance! It is still experimental
+ though: it may cause the plugin to crash. Setting the optimization level
+ to <tt>-O4</tt> when using this option will optimize even harder, though
+ this usually doesn't result in any improvement over <tt>-O3</tt>.</li>
+
+ <li>The type and constant conversion logic has been almost entirely rewritten,
+ fixing a multitude of obscure bugs.</li>
+
</ul>
</div>
implementations of this and other low-level routines (some are 3x faster than
the equivalent libgcc routines).</p>
-<p>In the LLVM 3.0 timeframe,</p>
+<p>In the LLVM 3.0 timeframe, the target specific ARM code has converted to
+ "unified" assembly syntax, and several new functions have been added to the
+ library.</p>
</div>
<div>
+<p>LLDB is a ground-up implementation of a command line debugger, as well as a
+ debugger API that can be used from other applications. LLDB makes use of the
+ Clang parser to provide high-fidelity expression parsing (particularly for
+ C++) and uses the LLVM JIT for target support.</p>
+
<p>LLDB has advanced by leaps and bounds in the 3.0 timeframe. It is
dramatically more stable and useful, and includes both a
new <a href="http://lldb.llvm.org/tutorial.html">tutorial</a> and
licensed</a> under the MIT and UIUC license, allowing it to be used more
permissively.</p>
+<p>Libc++ has been ported to FreeBSD and imported into the base system. It is
+ planned to be the default STL implementation for FreeBSD 10.</p>
+
+</div>
+
+<!--=========================================================================-->
+<h3>
+<a name="vmkit">VMKit</a>
+</h3>
+
+<div>
+
+ <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an
+ implementation of a Java Virtual Machine (Java VM or JVM) that uses LLVM for
+ static and just-in-time compilation.
+
+ <p>In the LLVM 3.0 time-frame, VMKit has had significant improvements on both
+ runtime and startup performance:</p>
+
+ <ul>
+ <li>Precompilation: by compiling ahead of time a small subset of Java's core
+ library, the startup performance have been highly optimized to the point that
+ running a 'Hello World' program takes less than 30 milliseconds.</li>
+
+ <li>Customization: by customizing virtual methods for individual classes,
+ the VM can statically determine the target of a virtual call, and decide to
+ inline it.</li>
+
+ <li>Inlining: the VM does more inlining than it did before, by allowing more
+ bytecode instructions to be inlined, and thanks to customization. It also
+ inlines GC barriers, and object allocations.</li>
+
+ <li>New exception model: the generated code for a method that does not do
+ any try/catch is not penalized anymore by the eventuality of calling a
+ method that throws an exception. Instead, the method that throws the
+ exception jumps directly to the method that could catch it.</li>
+ </ul>
+
</div>
</div>
-<!--=========================================================================-->
-<h3>
-<a name="vmkit">VMKit</a>
-</h3>
-
-<div>
-
-<p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
- of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
- just-in-time compilation. As of LLVM 3.0, VMKit now supports generational
- garbage collectors. The garbage collectors are provided by the MMTk
- framework, and VMKit can be configured to use one of the numerous implemented
- collectors of MMTk.</p>
-</div>
-
-
<!--=========================================================================-->
<!--
<h3>
<!--=========================================================================-->
<h3>AddressSanitizer</h3>
-
+
<div>
<p><a href="http://code.google.com/p/address-sanitizer/">AddressSanitizer</a>
<!--=========================================================================-->
<h3>ClamAV</h3>
-
+
<div>
<p><a href="http://www.clamav.net">Clam AntiVirus</a> is an open source (GPL)
<p>Since version 0.96 it
has <a href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode
- signatures</a> that allow writing detections for complex malware.</p>
-
-<p>It uses LLVM's JIT to speed up the execution of bytecode on X86, X86-64,
+ signatures</a> that allow writing detections for complex malware.
+ It uses LLVM's JIT to speed up the execution of bytecode on X86, X86-64,
PPC32/64, falling back to its own interpreter otherwise. The git version was
updated to work with LLVM 3.0.</p>
</div>
+<!--=========================================================================-->
+<h3>clang_complete for VIM</h3>
+
+<div>
+
+<p><a href="https://github.com/Rip-Rip/clang_complete">clang_complete</a> is a
+ VIM plugin, that provides accurate C/C++ autocompletion using the clang front
+ end. The development version of clang complete, can directly use libclang
+ which can maintain a cache to speed up auto completion.</p>
+
+</div>
+
<!--=========================================================================-->
<h3>clReflect</h3>
</div>
<!--=========================================================================-->
-<!-- FIXME: Comment out
+<h3>Cling C++ Interpreter</h3>
+
+<div>
+
+<p><a href="http://cern.ch/cling">Cling</a> is an interactive compiler interface
+ (aka C++ interpreter). It supports C++ and C, and uses LLVM's JIT and the
+ Clang parser. It has a prompt interface, runs source files, calls into shared
+ libraries, prints the value of expressions, even does runtime lookup of
+ identifiers (dynamic scopes). And it just behaves like one would expect from
+ an interpreter.</p>
+
+</div>
+
+<!--=========================================================================-->
<h3>Crack Programming Language</h3>
<div>
-<p>
-<a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide the
-ease of development of a scripting language with the performance of a compiled
-language. The language derives concepts from C++, Java and Python, incorporating
-object-oriented programming, operator overloading and strong typing.</p>
+
+<p><a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide
+ the ease of development of a scripting language with the performance of a
+ compiled language. The language derives concepts from C++, Java and Python,
+ incorporating object-oriented programming, operator overloading and strong
+ typing.</p>
+
+</div>
+
+<!--=========================================================================-->
+<h3>Eero</h3>
+
+<div>
+
+<p><a href="http://eerolanguage.org/">Eero</a> is a fully
+ header-and-binary-compatible dialect of Objective-C 2.0, implemented with a
+ patched version of the Clang/LLVM compiler. It features a streamlined syntax,
+ Python-like indentation, and new operators, for improved readability and
+ reduced code clutter. It also has new features such as limited forms of
+ operator overloading and namespaces, and strict (type-and-operator-safe)
+ enumerations. It is inspired by languages such as Smalltalk, Python, and
+ Ruby.</p>
+
+</div>
+
+<!--=========================================================================-->
+<h3>FAUST Real-Time Audio Signal Processing Language</h3>
+
+<div>
+
+<p><a href="http://faust.grame.fr/">FAUST</a> is a compiled language for
+ real-time audio signal processing. The name FAUST stands for Functional
+ AUdio STream. Its programming model combines two approaches: functional
+ programming and block diagram composition. In addition with the C, C++, Java
+ output formats, the Faust compiler can now generate LLVM bitcode, and works
+ with LLVM 2.7-3.0.
+ </p>
+
</div>
--->
-
+
<!--=========================================================================-->
<h3>Glasgow Haskell Compiler (GHC)</h3>
-
+
<div>
<p>GHC is an open source, state-of-the-art programming suite for Haskell, a
</div>
+<!--=========================================================================-->
+<h3>include-what-you-use</h3>
+
+<div>
+
+<p><a href="http://code.google.com/p/include-what-you-use">include-what-you-use</a>
+ is a tool to ensure that a file directly <code>#include</code>s
+ all <code>.h</code> files that provide a symbol that the file uses. It also
+ removes superfluous <code>#include</code>s from source files.</p>
+
+</div>
+
+<!--=========================================================================-->
+<h3>ispc: The Intel SPMD Program Compiler</h3>
+
+<div>
+
+<p><a href="http://ispc.github.com">ispc</a> is a compiler for "single program,
+ multiple data" (SPMD) programs. It compiles a C-based SPMD programming
+ language to run on the SIMD units of CPUs; it often delivers 5-6x speedups on
+ a single core of a CPU with an 8-wide SIMD unit compared to serial code,
+ while still providing a clean and easy-to-understand programming model. For
+ an introduction to the language and its performance,
+ see <a href="http://ispc.github.com/example.html">the walkthrough</a> of a short
+ example program. ispc is licensed under the BSD license.</p>
+
+</div>
+
+<!--=========================================================================-->
+<h3>The Julia Programming Language</h3>
+
+<div>
+
+<p><a href="http://github.com/JuliaLang/julia">Julia</a> is a high-level,
+ high-performance dynamic language for technical
+ computing. It provides a sophisticated compiler, distributed parallel
+ execution, numerical accuracy, and an extensive mathematical function
+ library. The compiler uses type inference to generate fast code
+ without any type declarations, and uses LLVM's optimization passes and
+ JIT compiler. The language is designed around multiple dispatch,
+ giving programs a large degree of flexibility. It is ready for use on many
+ kinds of problems.</p>
+</div>
+
<!--=========================================================================-->
<h3>LanguageKit and Pragmatic Smalltalk</h3>
its own interpreter. Pragmatic Smalltalk is a dialect of Smalltalk, built on
top of LanguageKit, that interfaces directly with Objective-C, sharing the
same object representation and message sending behaviour. These projects are
- developed as part of the Étoié desktop environment.</p>
+ developed as part of the Étoilé desktop environment.</p>
+
+</div>
+
+<!--=========================================================================-->
+<h3>LuaAV</h3>
+
+<div>
+
+<p><a href="http://lua-av.mat.ucsb.edu/blog/">LuaAV</a> is a real-time
+ audiovisual scripting environment based around the Lua language and a
+ collection of libraries for sound, graphics, and other media protocols. LuaAV
+ uses LLVM and Clang to JIT compile efficient user-defined audio synthesis
+ routines specified in a declarative syntax.</p>
</div>
binary compatible with Microsoft.NET. Has an optional, dynamically-loaded
LLVM code generation backend in Mini, the JIT compiler.</p>
-<p>Note that we use a Git mirror of LLVM with some patches. See:
- https://github.com/mono/llvm</p>
+<p>Note that we use a Git mirror of LLVM <a
+ href="https://github.com/mono/llvm">with some patches</a>.</p>
+
+</div>
+
+<!--=========================================================================-->
+<h3>Polly</h3>
+
+<div>
+
+<p><a href="http://polly.grosser.es">Polly</a> is an advanced data-locality
+ optimizer and automatic parallelizer. It uses an advanced, mathematical
+ model to calculate detailed data dependency information which it uses to
+ optimize the loop structure of a program. Polly can speed up sequential code
+ by improving memory locality and consequently the cache use. Furthermore,
+ Polly is able to expose different kind of parallelism which it exploits by
+ introducing (basic) OpenMP and SIMD code. A mid-term goal of Polly is to
+ automatically create optimized GPU code.</p>
</div>
<!--=========================================================================-->
<h3>Pure</h3>
-
+
<div>
<p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
algebraic/functional programming language based on term rewriting. Programs
languages (including the ability to load LLVM bitcode modules, and inline C,
C++, Fortran and Faust code in Pure programs if the corresponding LLVM-enabled
compilers are installed).</p>
-
+
<p>Pure version 0.48 has been tested and is known to work with LLVM 3.0
(and continues to work with older LLVM releases >= 2.5).</p>
co-design flow from C/C++ programs down to synthesizable VHDL and parallel
program binaries. Processor customization points include the register files,
function units, supported operations, and the interconnection network.</p>
-
+
<p>TCE uses Clang and LLVM for C/C++ language support, target independent
optimizations and also for parts of code generation. It generates new
LLVM-based code generators "on the fly" for the designed TTA processors and
per-target recompilation of larger parts of the compiler chain.</p>
</div>
-
+
<!--=========================================================================-->
<h3>Tart Programming Language</h3>
<p><a href="http://code.google.com/p/data-race-test/">ThreadSanitizer</a> is a
data race detector for (mostly) C and C++ code, available for Linux, Mac OS
and Windows. On different systems, we use binary instrumentation frameworks
- (Valgrind, Pin and DynamoRio) as frontends that generate the program events
- for the race detection algorithm. On Linux, there's an option of using
- LLVM-based compile-time instrumentation.</p>
+ (Valgrind and Pin) as frontends that generate the program events for the race
+ detection algorithm. On Linux, there's an option of using LLVM-based
+ compile-time instrumentation.</p>
</div>
+</div>
+
+<!-- *********************************************************************** -->
+<h2>
+ <a name="whatsnew">What's New in LLVM 3.0?</a>
+</h2>
+<!-- *********************************************************************** -->
+
+<div>
+
+<p>This release includes a huge number of bug fixes, performance tweaks and
+ minor improvements. Some of the major improvements and new features are
+ listed in this section.</p>
+
<!--=========================================================================-->
-<h3>The ZooLib C++ Cross-Platform Application Framework</h3>
+<h3>
+<a name="majorfeatures">Major New Features</a>
+</h3>
<div>
-<p><a href="http://www.zoolib.org/">ZooLib</a> is Open Source under the MIT
- License. It provides GUI, filesystem access, TCP networking, thread-safe
- memory management, threading and locking for Mac OS X, Classic Mac OS,
- Microsoft Windows, POSIX operating systems with X11, BeOS, Haiku, Apple's iOS
- and Research in Motion's BlackBerry.</p>
+ <!-- Features that need text if they're finished for 3.1:
+ ARM EHABI
+ combiner-aa?
+ strong phi elim
+ loop dependence analysis
+ CorrelatedValuePropagation
+ lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
+ Integrated assembler on by default for arm/thumb?
+
+ -->
+
+ <!-- Near dead:
+ Analysis/RegionInfo.h + Dom Frontiers
+ SparseBitVector: used in LiveVar.
+ llvm/lib/Archive - replace with lib object?
+ -->
+
+<p>LLVM 3.0 includes several major changes and big features:</p>
-<p>My current work is to use CLang's static analyzer to improve ZooLib's code
- quality. I also plan to set up LLVM compiles of the demo programs and test
- programs using CLang and LLVM on all the platforms that CLang, LLVM and
- ZooLib all support.</p>
+<ul>
+<li>llvm-gcc is no longer supported, and not included in the release. We
+ recommend switching to <a
+ href="http://clang.llvm.org/">Clang</a> or <a
+ href="http://dragonegg.llvm.org/">DragonEgg</a>.</li>
+
+<li>The linear scan register allocator has been replaced with a new "greedy"
+ register allocator, enabling live range splitting and many other
+ optimizations that lead to better code quality. Please see its <a
+ href="http://blog.llvm.org/2011/09/greedy-register-allocation-in-llvm-30.html">blog post</a> or its talk at the <a
+ href="http://llvm.org/devmtg/2011-11/">Developer Meeting</a>
+ for more information.</li>
+<li>LLVM IR now includes full support for <a href="Atomics.html">atomics
+ memory operations</a> intended to support the C++'11 and C'1x memory models.
+ This includes <a href="LangRef.html#memoryops">atomic load and store,
+ compare and exchange, and read/modify/write instructions</a> as well as a
+ full set of <a href="LangRef.html#ordering">memory ordering constraints</a>.
+ Please see the <a href="Atomics.html">Atomics Guide</a> for more
+ information.
+</li>
+<li>The LLVM IR exception handling representation has been redesigned and
+ reimplemented, making it more elegant, fixing a huge number of bugs, and
+ enabling inlining and other optimizations. Please see its <a href=
+ "http://blog.llvm.org/2011/11/llvm-30-exception-handling-redesign.html">blog
+ post</a> and the <a href="ExceptionHandling.html">Exception Handling
+ documentation</a> for more information.</li>
+<li>The LLVM IR Type system has been redesigned and reimplemented, making it
+ faster and solving some long-standing problems.
+ Please see its <a
+ href="http://blog.llvm.org/2011/11/llvm-30-type-system-rewrite.html">blog
+ post</a> for more information.</li>
+
+<li>The MIPS backend has made major leaps in this release, going from an
+ experimental target to being virtually production quality and supporting a
+ wide variety of MIPS subtargets. See the <a href="#MIPS">MIPS section</a>
+ below for more information.</li>
+
+<li>The optimizer and code generator now supports gprof and gcov-style coverage
+ and profiling information, and includes a new llvm-cov tool (but also works
+ with gcov). Clang exposes coverage and profiling through GCC-compatible
+ command line options.</li>
+</ul>
</div>
+
<!--=========================================================================-->
-<!--
-<h3>PinaVM</h3>
-
+<h3>
+<a name="coreimprovements">LLVM IR and Core Improvements</a>
+</h3>
+
<div>
-<p><a href="http://gitorious.org/pinavm/pages/Home">PinaVM</a> is an open
-source, <a href="http://www.systemc.org/">SystemC</a> front-end. Unlike many
-other front-ends, PinaVM actually executes the elaboration of the
-program analyzed using LLVM's JIT infrastructure. It later enriches the
-bitcode with SystemC-specific information.</p>
-</div>
--->
+<p>LLVM IR has several new features for better support of new targets and that
+ expose new optimization opportunities:</p>
+
+ <ul>
+ <li><a href="Atomics.html">Atomic memory accesses and memory ordering</a> are
+ now directly expressible in the IR.</li>
+ <li>A new <a href="LangRef.html#int_fma">llvm.fma intrinsic</a> directly
+ represents floating point multiply accumulate operations without an
+ intermediate rounding stage.</li>
+ <li>A new <a href="LangRef.html#int_expect">llvm.expect intrinsic</a> allows a
+ frontend to express expected control flow (and the
+ <a href="BranchWeightMetadata.html#builtin_expect">
+ <code>__builtin_expect</code></a> from GNU C).</li>
+ <li>The <a href="LangRef.html#int_prefetch">llvm.prefetch intrinsic</a> now
+ takes a 4th argument that specifies whether the prefetch happens from the
+ icache or dcache.</li>
+ <li>The new <a href="LangRef.html#uwtable">uwtable function attribute</a>
+ allows a frontend to control emission of unwind tables.</li>
+ <li>The new <a href="LangRef.html#fnattrs">nonlazybind function
+ attribute</a> allow optimization of Global Offset Table (GOT) accesses.</li>
+ <li>The new <a href="LangRef.html#returns_twice">returns_twice attribute</a>
+ allows better modeling of functions like setjmp.</li>
+ <li>The <a href="LangRef.html#datalayout">target datalayout</a> string can now
+ encode the natural alignment of the target's stack for better optimization.
+ </li>
+ </ul>
+</div>
<!--=========================================================================-->
-<!--
-<h3 id="icedtea">IcedTea Java Virtual Machine Implementation</h3>
+<h3>
+<a name="optimizer">Optimizer Improvements</a>
+</h3>
<div>
-<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>
-<p> OpenJDK 7 b112, IcedTea6 1.9 and IcedTea7 1.13 and later have been tested
-and are known to work with LLVM 3.0 (and continue to work with older LLVM
-releases >= 2.6 as well).</p>
+<p>In addition to many minor performance tweaks and bug fixes, this
+ release includes a few major enhancements and additions to the
+ optimizers:</p>
+
+<ul>
+<li>The pass manager now has an extension API that allows front-ends and plugins
+ to insert their own optimizations in the well-known places in the standard
+ pass optimization pipeline.</li>
+
+<li>Information about <a href="BranchWeightMetadata.html">branch probability</a>
+ and basic block frequency is now available within LLVM, based on a
+ combination of static branch prediction heuristics and
+ <code>__builtin_expect</code> calls. That information is currently used for
+ register spill placement and if-conversion, with additional optimizations
+ planned for future releases. The same framework is intended for eventual
+ use with profile-guided optimization.</li>
+
+<li>The "-indvars" induction variable simplification pass only modifies
+ induction variables when profitable. Sign and zero extension
+ elimination, linear function test replacement, loop unrolling, and
+ other simplifications that require induction variable analysis have
+ been generalized so they no longer require loops to be rewritten into
+ canonical form prior to optimization. This new design
+ preserves more IR level information, avoids undoing earlier loop
+ optimizations (particularly hand-optimized loops), and no longer
+ requires the code generator to reconstruct loops into an optimal form -
+ an intractable problem.</li>
+
+<li>LLVM now includes a pass to optimize retain/release calls for the
+ <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">Automatic
+ Reference Counting</a> (ARC) Objective-C language feature (in
+ lib/Transforms/Scalar/ObjCARC.cpp). It is a decent example of implementing
+ a source-language-specific optimization in LLVM.</li>
+
+</ul>
+
</div>
--->
<!--=========================================================================-->
-<!--
-<h3>Polly - Polyhedral optimizations for LLVM</h3>
-
+<h3>
+<a name="mc">MC Level Improvements</a>
+</h3>
+
<div>
-<p>Polly is a project that aims to provide advanced memory access optimizations
-to better take advantage of SIMD units, cache hierarchies, multiple cores or
-even vector accelerators for LLVM. Built around an abstract mathematical
-description based on Z-polyhedra, it provides the infrastructure to develop
-advanced optimizations in LLVM and to connect complex external optimizers. In
-its first year of existence Polly already provides an exact value-based
-dependency analysis as well as basic SIMD and OpenMP code generation support.
-Furthermore, Polly can use PoCC(Pluto) an advanced optimizer for data-locality
-and parallelism.</p>
+
+<p>The LLVM Machine Code (aka MC) subsystem was created to solve a number of
+ problems in the realm of assembly, disassembly, object file format handling,
+ and a number of other related areas that CPU instruction-set level tools work
+ in. For more information, please see
+ the <a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
+ to the LLVM MC Project Blog Post</a>.</p>
+
+<ul>
+ <li>The MC layer has undergone significant refactoring to eliminate layering
+ violations that caused it to pull in the LLVM compiler backend code.</li>
+ <li>The ELF object file writers are much more full featured.</li>
+ <li>The integrated assembler now supports #line directives.</li>
+ <li>An early implementation of a JIT built on top of the MC framework (known
+ as MC-JIT) has been implemented and will eventually replace the old JIT.
+ It emits object files direct to memory and uses a runtime dynamic linker to
+ resolve references and drive lazy compilation. The MC-JIT enables much
+ greater code reuse between the JIT and the static compiler and provides
+ better integration with the platform ABI as a result.
+ </li>
+ <li>The assembly printer now makes uses of assemblers instruction aliases
+ (InstAliases) to print simplified mneumonics when possible.</li>
+ <li>TableGen can now autogenerate MC expansion logic for pseudo
+ instructions that expand to multiple MC instructions (through the
+ PseudoInstExpansion class).</li>
+ <li>A new llvm-dwarfdump tool provides a start of a drop-in
+ replacement for the corresponding tool that use LLVM libraries. As part of
+ this, LLVM has the beginnings of a dwarf parsing library.</li>
+ <li>llvm-objdump has more output including, symbol by symbol disassembly,
+ inline relocations, section headers, symbol tables, and section contents.
+ Support for archive files has also been added.</li>
+ <li>llvm-nm has gained support for archives of binary files.</li>
+ <li>llvm-size has been added. This tool prints out section sizes.</li>
+</ul>
+
</div>
--->
<!--=========================================================================-->
-<!--
-<h3>Rubinius</h3>
+<h3>
+<a name="codegen">Target Independent Code Generator Improvements</a>
+</h3>
<div>
- <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 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 deoptimization are all used to remove dynamism
- from ruby execution and increase performance.</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>LLVM can now produce code that works with libgcc
+ to <a href="SegmentedStacks.html">dynamically allocate stack
+ segments</a>, as opposed to allocating a worst-case chunk of
+ virtual memory for each thread.</li>
+<li>LLVM generates substantially better code for indirect gotos due to a new
+ tail duplication pass, which can be a substantial performance win for
+ interpreter loops that use them.</li>
+<li>Exception handling and debug frame information is now emitted with CFI
+ directives. This lets the assembler produce more compact info as it knows
+ the final offsets, yielding <a href="http://blog.mozilla.com/respindola/2011/05/12/cfi-directives/">much smaller executables</a> for some C++ applications.
+ If the system assembler doesn't support it, MC exands the directives when
+ the integrated assembler is not used.
+</li>
+
+<li>The code generator now supports vector "select" operations on vector
+ comparisons, turning them into various optimized code sequences (e.g.
+ using the SSE4/AVX "blend" instructions).</li>
+<li>The SSE execution domain fix pass and the ARM NEON move fix pass have been
+ merged to a target independent execution dependency fix pass. This pass is
+ used to select alternative equivalent opcodes in a way that minimizes
+ execution domain crossings. Closely connected instructions are moved to
+ the same execution domain when possible. Targets can override the
+ <code>getExecutionDomain</code> and <code>setExecutionDomain</code> hooks
+ to use the pass.</li>
+</ul>
</div>
--->
<!--=========================================================================-->
-<!--
<h3>
-<a name="FAUST">FAUST Real-Time Audio Signal Processing Language</a>
+<a name="x86">X86-32 and X86-64 Target Improvements</a>
</h3>
<div>
-<p>
-<a href="http://faust.grame.fr">FAUST</a> is a compiled language for real-time
-audio signal processing. The name FAUST stands for Functional AUdio STream. Its
-programming model combines two approaches: functional programming and block
-diagram composition. In addition with the C, C++, JAVA output formats, the
-Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7-3.0.</p>
-</div>
--->
-
+<p>New features and major changes in the X86 target include:</p>
+
+<ul>
+<li>The X86 backend, assembler and disassembler now have full support for AVX 1.
+ To enable it pass <code>-mavx</code> to the compiler. AVX2 implementation is
+ underway on mainline.</li>
+<li>The integrated assembler and disassembler now support a broad range of new
+ instructions including Atom, Ivy Bridge, <a
+ href="http://en.wikipedia.org/wiki/SSE4a">SSE4a/BMI</a> instructions, <a
+ href="http://en.wikipedia.org/wiki/RdRand">rdrand</a> and many others.</li>
+<li>The X86 backend now fully supports the <a href="http://llvm.org/PR879">X87
+ floating point stack inline assembly constraints</a>.</li>
+<li>The integrated assembler now supports the <tt>.code32</tt> and
+ <tt>.code64</tt> directives to switch between 32-bit and 64-bit
+ instructions.</li>
+<li>The X86 backend now synthesizes horizontal add/sub instructions from generic
+ vector code when the appropriate instructions are enabled.</li>
+<li>The X86-64 backend generates smaller and faster code at -O0 due to
+ improvements in fast instruction selection.</li>
+<li><a href="http://code.google.com/p/nativeclient/">Native Client</a>
+ subtarget support has been added.</li>
+
+<li>The CRC32 intrinsics have been renamed. The intrinsics were previously
+ <code>@llvm.x86.sse42.crc32.[8|16|32]</code>
+ and <code>@llvm.x86.sse42.crc64.[8|64]</code>. They have been renamed to
+ <code>@llvm.x86.sse42.crc32.32.[8|16|32]</code> and
+ <code>@llvm.x86.sse42.crc32.64.[8|64]</code>.</li>
+</ul>
+
</div>
-<!-- *********************************************************************** -->
-<h2>
- <a name="whatsnew">What's New in LLVM 3.0?</a>
-</h2>
-<!-- *********************************************************************** -->
+<!--=========================================================================-->
+<h3>
+<a name="ARM">ARM Target Improvements</a>
+</h3>
<div>
-<p>This release includes a huge number of bug fixes, performance tweaks and
- minor improvements. Some of the major improvements and new features are
- listed in this section.</p>
+<p>New features of the ARM target include:</p>
+
+<ul>
+<li>The ARM backend generates much faster code for Cortex-A9 chips.</li>
+<li>The ARM backend has improved support for Cortex-M series processors.</li>
+<li>The ARM inline assembly constraints have been implemented and are now fully
+ supported.</li>
+<li>NEON code produced by Clang often runs much faster due to improvements in
+ the Scalar Replacement of Aggregates pass.</li>
+<li>The old ARM disassembler is replaced with a new one based on autogenerated
+ encoding information from ARM .td files.</li>
+<li>The integrated assembler has made major leaps forward, but is still beta quality in LLVM 3.0.</li>
+</ul>
+</div>
+
<!--=========================================================================-->
<h3>
-<a name="majorfeatures">Major New Features</a>
+<a name="MIPS">MIPS Target Improvements</a>
</h3>
<div>
-<p>LLVM 3.0 includes several major new capabilities:</p>
+<p>This release has seen major new work on just about every aspect of the MIPS
+ backend. Some of the major new features include:</p>
<ul>
-
-<!--
-<li></li>
--->
-
+ <li>Most MIPS32r1 and r2 instructions are now supported.</li>
+ <li>LE/BE MIPS32r1/r2 has been tested extensively.</li>
+ <li>O32 ABI has been fully tested.</li>
+ <li>MIPS backend has migrated to using the MC infrastructure for assembly printing. Initial support for direct object code emission has been implemented too.</li>
+ <li>Delay slot filler has been updated. Now it tries to fill delay slots with useful instructions instead of always filling them with NOPs.</li>
+ <li>Support for old-style JIT is complete.</li>
+ <li>Support for old architectures (MIPS1 and MIPS2) has been removed.</li>
+ <li>Initial support for MIPS64 has been added.</li>
</ul>
-
</div>
<!--=========================================================================-->
<h3>
-<a name="coreimprovements">LLVM IR and Core Improvements</a>
+ <a name="PTX">PTX Target Improvements</a>
</h3>
<div>
-<p>LLVM IR has several new features for better support of new targets and that
- expose new optimization opportunities:</p>
+ <p>
+ The PTX back-end is still experimental, but is fairly usable for compute kernels
+ in LLVM 3.0. Most scalar arithmetic is implemented, as well as intrinsics to
+ access the special PTX registers and sync instructions. The major missing
+ pieces are texture/sampler support and some vector operations.</p>
-<p>One of the biggest changes is that 3.0 has a new exception handling
- system. The old system used LLVM intrinsics to convey the exception handling
- information to the code generator. It worked in most cases, but not
- all. Inlining was especially difficult to get right. Also, the intrinsics
- could be moved away from the <code>invoke</code> instruction, making it hard
- to recover that information.</p>
+ <p>That said, the backend is already being used for domain-specific languages
+ and can be used by Clang to
+ <a href="http://clang.llvm.org/docs/ReleaseNotes.html#opencl">compile OpenCL
+ C code</a> into PTX.</p>
-<p>The new EH system makes exception handling a first-class member of the IR. It
- adds two new instructions:</p>
+</div>
+
+<!--=========================================================================-->
+<h3>
+<a name="OtherTS">Other Target Specific Improvements</a>
+</h3>
+
+<div>
<ul>
- <li><a href="LangRef.html#i_landingpad"><code>landingpad</code></a> —
- this instruction defines a landing pad basic block. It contains all of the
- information that's needed by the code generator. It's also required to be
- the first non-PHI instruction in the landing pad. In addition, a landing
- pad may be jumped to only by the unwind edge of an <code>invoke</code>
- instruction.</li>
+<li>Many PowerPC improvements have been implemented for ELF targets, including
+ support for varargs and initial support for direct .o file emission.</li>
+
+<li>MicroBlaze scheduling itineraries were added that model the
+ 3-stage and the 5-stage pipeline architectures. The 3-stage
+ pipeline model can be selected with <code>-mcpu=mblaze3</code>
+ and the 5-stage pipeline model can be selected with
+ <code>-mcpu=mblaze5</code>.</li>
- <li><a href="LangRef.html#i_resume"><code>resume</code></a> — this
- instruction causes the current exception to resume traveling up the
- stack. It replaces the <code>@llvm.eh.resume</code> intrinsic.</li>
-</ul>
-
-<p>Converting from the old EH API to the new EH API is rather simple, because a
- lot of complexity has been removed. The two intrinsics,
- <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code> have been
- superceded by the <code>landingpad</code> instruction. Instead of generating
- a call to <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code>:
-
-<div class="doc_code">
-<pre>
-Function *ExcIntr = Intrinsic::getDeclaration(TheModule,
- Intrinsic::eh_exception);
-Function *SlctrIntr = Intrinsic::getDeclaration(TheModule,
- Intrinsic::eh_selector);
-
-// The exception pointer.
-Value *ExnPtr = Builder.CreateCall(ExcIntr, "exc_ptr");
-
-std::vector<Value*> Args;
-Args.push_back(ExnPtr);
-Args.push_back(Builder.CreateBitCast(Personality,
- Type::getInt8PtrTy(Context)));
-
-<i>// Add selector clauses to Args.</i>
-
-// The selector call.
-Builder.CreateCall(SlctrIntr, Args, "exc_sel");
-</pre>
-</div>
-
-<p>You should instead generate a <code>landingpad</code> instruction, that
- returns an exception object and selector value:</p>
-
-<div class="doc_code">
-<pre>
-LandingPadInst *LPadInst =
- Builder.CreateLandingPad(StructType::get(Int8PtrTy, Int32Ty, NULL),
- Personality, 0);
-
-Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
-Builder.CreateStore(LPadExn, getExceptionSlot());
-
-Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
-Builder.CreateStore(LPadSel, getEHSelectorSlot());
-</pre>
-</div>
-
-<p>It's now trivial to add the individual clauses to the <code>landingpad</code>
- instruction.</p>
-
-<div class="doc_code">
-<pre>
-<i><b>// Adding a catch clause</b></i>
-Constant *TypeInfo = getTypeInfo();
-LPadInst->addClause(TypeInfo);
-
-<i><b>// Adding a C++ catch-all</b></i>
-LPadInst->addClause(Constant::getNullValue(Builder.getInt8PtrTy()));
-
-<i><b>// Adding a cleanup</b></i>
-LPadInst->setCleanup(true);
-
-<i><b>// Adding a filter clause</b></i>
-std::vector<Constant*> TypeInfos;
-Constant *TypeInfo = getFilterTypeInfo();
-TypeInfos.push_back(Builder.CreateBitCast(TypeInfo, Builder.getInt8PtrTy()));
-
-ArrayType *FilterTy = ArrayType::get(Int8PtrTy, TypeInfos.size());
-LPadInst->addClause(ConstantArray::get(FilterTy, TypeInfos));
-</pre>
-</div>
-
-<p>Converting from using the <code>@llvm.eh.resume</code> intrinsic to
- the <code>resume</code> instruction is trivial. It takes the exception
- pointer and exception selector values returned by
- the <code>landingpad</code> instruction:</p>
-
-<div class="doc_code">
-<pre>
-Type *UnwindDataTy = StructType::get(Builder.getInt8PtrTy(),
- Builder.getInt32Ty(), NULL);
-Value *UnwindData = UndefValue::get(UnwindDataTy);
-Value *ExcPtr = Builder.CreateLoad(getExceptionObjSlot());
-Value *ExcSel = Builder.CreateLoad(getExceptionSelSlot());
-UnwindData = Builder.CreateInsertValue(UnwindData, ExcPtr, 0, "exc_ptr");
-UnwindData = Builder.CreateInsertValue(UnwindData, ExcSel, 1, "exc_sel");
-Builder.CreateResume(UnwindData);
-</pre>
-</div>
-
-</div>
-
-<!--=========================================================================-->
-<h3>
-<a name="optimizer">Optimizer Improvements</a>
-</h3>
-
-<div>
-
-<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></li>
--->
-</li>
-
-</ul>
-
-</div>
-
-<!--=========================================================================-->
-<h3>
-<a name="mc">MC Level Improvements</a>
-</h3>
-
-<div>
-
-<p>The LLVM Machine Code (aka MC) subsystem was created to solve a number of
- problems in the realm of assembly, disassembly, object file format handling,
- and a number of other related areas that CPU instruction-set level tools work
- in.</p>
-
-<ul>
-<!--
-<li></li>
--->
-</ul>
-
-<p>For more information, please see
- the <a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
- to the LLVM MC Project Blog Post</a>.</p>
-
-</div>
-
-<!--=========================================================================-->
-<h3>
-<a name="codegen">Target Independent Code Generator Improvements</a>
-</h3>
-
-<div>
-
-<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></li>
--->
-</ul>
-</div>
-
-<!--=========================================================================-->
-<h3>
-<a name="x86">X86-32 and X86-64 Target Improvements</a>
-</h3>
-
-<div>
-
-<p>New features and major changes in the X86 target include:</p>
-
-<ul>
-
- <li>The CRC32 intrinsics have been renamed. The intrinsics were previously
- <code>@llvm.x86.sse42.crc32.[8|16|32]</code>
- and <code>@llvm.x86.sse42.crc64.[8|64]</code>. They have been renamed to
- <code>@llvm.x86.sse42.crc32.32.[8|16|32]</code> and
- <code>@llvm.x86.sse42.crc32.64.[8|64]</code>.</li>
-
-</ul>
-
-</div>
-
-<!--=========================================================================-->
-<h3>
-<a name="ARM">ARM Target Improvements</a>
-</h3>
-
-<div>
-
-<p>New features of the ARM target include:</p>
-
-<ul>
-<!--
-<li></li>
--->
-</ul>
-</div>
-
-<!--=========================================================================-->
-<h3>
-<a name="OtherTS">Other Target Specific Improvements</a>
-</h3>
-
-<div>
-
-<ul>
-<!--
-<li></li>
--->
</ul>
</div>
from the previous release.</p>
<ul>
- <li>The <code>LLVMC</code> front end code was removed while separating
- out language independence.</li>
- <li>The <code>LowerSetJmp</code> pass wasn't used effectively by any
- target and has been removed.</li>
+<li>LLVM 3.0 removes support for reading LLVM 2.8 and earlier files, and LLVM
+ 3.1 will eliminate support for reading LLVM 2.9 files. Going forward, we
+ aim for all future versions of LLVM to read bitcode files and .ll files
+ produced by LLVM 3.0.</li>
+<li>Tablegen has been split into a library, allowing the clang tblgen pieces
+ to now live in the clang tree. The llvm version has been renamed to
+ llvm-tblgen instead of tblgen.</li>
+ <li>The <code>LLVMC</code> meta compiler driver was removed.</li>
+ <li>The unused PostOrder Dominator Frontiers and LowerSetJmp passes were removed.</li>
+
+
<li>The old <code>TailDup</code> pass was not used in the standard pipeline
and was unable to update ssa form, so it has been removed.
<li>The syntax of volatile loads and stores in IR has been changed to
"<code>load volatile</code>"/"<code>store volatile</code>". The old
syntax ("<code>volatile load</code>"/"<code>volatile store</code>")
- is still accepted, but is now considered deprecated.</li>
- <li>The old atomic intrinscs (<code>llvm.memory.barrier</code> and
+ is still accepted, but is now considered deprecated and will be removed in
+ 3.1.</li>
+ <li>llvm-gcc's frontend tests have been removed from llvm/test/Frontend*, sunk
+ into the clang and dragonegg testsuites.</li>
+ <li>The old atomic intrinsics (<code>llvm.memory.barrier</code> and
<code>llvm.atomic.*</code>) are now gone. Please use the new atomic
instructions, described in the <a href="Atomics.html">atomics guide</a>.
+ <li>LLVM's configure script doesn't depend on llvm-gcc anymore, eliminating a
+ strange circular dependence between projects.</li>
</ul>
<h4>Windows (32-bit)</h4>
LLVM API changes are:</p>
<ul>
- <li>The biggest and most pervasive change is that llvm::Type's are no longer
- returned or accepted as 'const' values. Instead, just pass around
- non-const Type's.</li>
-
+ <li>The biggest and most pervasive change is that the type system has been
+ rewritten: <code>PATypeHolder</code> and <code>OpaqueType</code> are gone,
+ and all APIs deal with <code>Type*</code> instead of <code>const
+ Type*</code>. If you need to create recursive structures, then create a
+ named structure, and use <code>setBody()</code> when all its elements are
+ built. Type merging and refining is gone too: named structures are not
+ merged with other structures, even if their layout is identical. (of
+ course anonymous structures are still uniqued by layout).</li>
+
<li><code>PHINode::reserveOperandSpace</code> has been removed. Instead, you
must specify how many operands to reserve space for when you create the
PHINode, by passing an extra argument
use <code>DIBuilder::finalize()</code> at the end of translation unit to
complete debugging information encoding.</li>
- <li>The way the type system works has been
- rewritten: <code>PATypeHolder</code> and <code>OpaqueType</code> are gone,
- and all APIs deal with <code>Type*</code> instead of <code>const
- Type*</code>. If you need to create recursive structures, then create a
- named structure, and use <code>setBody()</code> when all its elements are
- built. Type merging and refining is gone too: named structures are not
- merged with other structures, even if their layout is identical. (of
- course anonymous structures are still uniqued by layout).</li>
-
<li>TargetSelect.h moved to Support/ from Target/</li>
<li>UpgradeIntrinsicCall no longer upgrades pre-2.9 intrinsic calls (for
<div>
-<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>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="experimental">Experimental features included with this release</a>
-</h3>
-
-<div>
+<p>LLVM is generally a production quality compiler, and is used by a broad range
+ of applications and shipping in many products. That said, not every
+ subsystem is as mature as the aggregate, particularly the more obscure
+ targets. If you run into a problem, please check the <a
+ href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
+ there isn't already one or ask on the <a
+ href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
+ list</a>.</p>
-<p>The following components of this LLVM release are either untested, known to
- be broken or unreliable, or are in early development. These components
- should not be relied on, and bugs should not be filed against them, but they
- may be useful to some people. In particular, if you would like to work on
- one of these components, please contact us on
- the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
- list</a>.</p>
+ <p>Known problem areas include:</p>
<ul>
- <li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ and
- XCore backends are experimental.</li>
+ <li>The Alpha, Blackfin, CellSPU, MSP430, PTX, SystemZ and
+ XCore backends are experimental, and the Alpha, Blackfin and SystemZ
+ targets have already been removed from mainline.</li>
+
+ <li>The integrated assembler, disassembler, and JIT is not supported by
+ several targets. If an integrated assembler is not supported, then a
+ system assembler is required. For more details, see the <a
+ href="CodeGenerator.html#targetfeatures">Target Features Matrix</a>.
+ </li>
- <li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets other
- than darwin and ELF X86 systems.</li>
+ <li>The C backend has numerous problems and is not being actively maintained.
+ Depending on it for anything serious is not advised.</li>
</ul>
</div>
-<!-- ======================================================================= -->
-<h3>
- <a name="x86-be">Known problems with the X86 back-end</a>
-</h3>
+<!-- *********************************************************************** -->
+<h2>
+ <a name="additionalinfo">Additional Information</a>
+</h2>
+<!-- *********************************************************************** -->
<div>
-<ul>
- <li>The X86 backend does not yet support
- all <a href="http://llvm.org/PR879">inline assembly that uses the X86
- floating point stack</a>. It supports the 'f' and 't' constraints, but
- not 'u'.</li>
-
- <li>The X86-64 backend does not yet support the LLVM IR instruction
- <tt>va_arg</tt>. Currently, front-ends support variadic argument
- constructs on X86-64 by lowering them manually.</li>
-
- <li>Windows x64 (aka Win64) code generator has a few issues.
- <ul>
- <li>llvm-gcc cannot build the mingw-w64 runtime currently due to lack of
- support for the 'u' inline assembly constraint and for X87 floating
- point inline assembly.</li>
-
- <li>On mingw-w64, you will see unresolved symbol <tt>__chkstk</tt> due
- to <a href="http://llvm.org/bugs/show_bug.cgi?id=8919">Bug 8919</a>.
- It is fixed
- in <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110321/118499.html">r128206</a>.</li>
-
- <li>Miss-aligned MOVDQA might crash your program. It is due to
- <a href="http://llvm.org/bugs/show_bug.cgi?id=9483">Bug 9483</a>, lack
- of handling aligned internal globals.</li>
- </ul>
- </li>
+<p>A wide variety of additional information is available on
+ the <a href="http://llvm.org/">LLVM web page</a>, in particular in
+ the <a href="http://llvm.org/docs/">documentation</a> section. The web page
+ also contains versions of the API documentation which is up-to-date with the
+ Subversion version of the source code. You can access versions of these
+ documents specific to this release by going into the "<tt>llvm/doc/</tt>"
+ directory in the LLVM tree.</p>
-</ul>
+<p>If you have any questions or comments about LLVM, please feel free to contact
+ us via the <a href="http://llvm.org/docs/#maillist"> mailing lists</a>.</p>
</div>
-<!-- ======================================================================= -->
-<h3>
- <a name="ppc-be">Known problems with the PowerPC back-end</a>
-</h3>
+<!--=========================================================================-->
-<div>
+<!-- EH details: to be moved to a blog post:
-<ul>
- <li>The Linux PPC32/ABI support needs testing for the interpreter and static
- compilation, and lacks support for debug information.</li>
-</ul>
-</div>
-<!-- ======================================================================= -->
-<h3>
- <a name="arm-be">Known problems with the ARM back-end</a>
-</h3>
-<div>
+<p>One of the biggest changes is that 3.0 has a new exception handling
+ system. The old system used LLVM intrinsics to convey the exception handling
+ information to the code generator. It worked in most cases, but not
+ all. Inlining was especially difficult to get right. Also, the intrinsics
+ could be moved away from the <code>invoke</code> instruction, making it hard
+ to recover that information.</p>
+
+<p>The new EH system makes exception handling a first-class member of the IR. It
+ adds two new instructions:</p>
<ul>
- <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
- processors, thumb programs can crash or produce wrong results
- (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
+ <li><a href="LangRef.html#i_landingpad"><code>landingpad</code></a> —
+ this instruction defines a landing pad basic block. It contains all of the
+ information that's needed by the code generator. It's also required to be
+ the first non-PHI instruction in the landing pad. In addition, a landing
+ pad may be jumped to only by the unwind edge of an <code>invoke</code>
+ instruction.</li>
- <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully
- tested.</li>
+ <li><a href="LangRef.html#i_resume"><code>resume</code></a> — this
+ instruction causes the current exception to resume traveling up the
+ stack. It replaces the <code>@llvm.eh.resume</code> intrinsic.</li>
</ul>
-</div>
-
-<!-- ======================================================================= -->
-<h3>
- <a name="sparc-be">Known problems with the SPARC back-end</a>
-</h3>
-
-<div>
-
-<ul>
- <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
- support the 64-bit SPARC ABI (-m64).</li>
-</ul>
+<p>Converting from the old EH API to the new EH API is rather simple, because a
+ lot of complexity has been removed. The two intrinsics,
+ <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code> have been
+ superseded by the <code>landingpad</code> instruction. Instead of generating
+ a call to <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code>:
-</div>
+<div class="doc_code">
+<pre>
+Function *ExcIntr = Intrinsic::getDeclaration(TheModule,
+ Intrinsic::eh_exception);
+Function *SlctrIntr = Intrinsic::getDeclaration(TheModule,
+ Intrinsic::eh_selector);
-<!-- ======================================================================= -->
-<h3>
- <a name="mips-be">Known problems with the MIPS back-end</a>
-</h3>
+// The exception pointer.
+Value *ExnPtr = Builder.CreateCall(ExcIntr, "exc_ptr");
-<div>
+std::vector<Value*> Args;
+Args.push_back(ExnPtr);
+Args.push_back(Builder.CreateBitCast(Personality,
+ Type::getInt8PtrTy(Context)));
-<ul>
- <li>64-bit MIPS targets are not supported yet.</li>
-</ul>
+<i>// Add selector clauses to Args.</i>
+// The selector call.
+Builder.CreateCall(SlctrIntr, Args, "exc_sel");
+</pre>
</div>
-<!-- ======================================================================= -->
-<h3>
- <a name="alpha-be">Known problems with the Alpha back-end</a>
-</h3>
+<p>You should instead generate a <code>landingpad</code> instruction, that
+ returns an exception object and selector value:</p>
-<div>
+<div class="doc_code">
+<pre>
+LandingPadInst *LPadInst =
+ Builder.CreateLandingPad(StructType::get(Int8PtrTy, Int32Ty, NULL),
+ Personality, 0);
-<ul>
- <li>On 21164s, some rare FP arithmetic sequences which may trap do not have
- the appropriate nops inserted to ensure restartability.</li>
-</ul>
+Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
+Builder.CreateStore(LPadExn, getExceptionSlot());
+Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
+Builder.CreateStore(LPadSel, getEHSelectorSlot());
+</pre>
</div>
-<!-- ======================================================================= -->
-<h3>
- <a name="c-be">Known problems with the C back-end</a>
-</h3>
-
-<div>
-
-<p>The C backend has numerous problems and is not being actively maintained.
- Depending on it for anything serious is not advised.</p>
+<p>It's now trivial to add the individual clauses to the <code>landingpad</code>
+ instruction.</p>
-<ul>
- <li><a href="http://llvm.org/PR802">The C backend has only basic support for
- inline assembly code</a>.</li>
+<div class="doc_code">
+<pre>
+<i><b>// Adding a catch clause</b></i>
+Constant *TypeInfo = getTypeInfo();
+LPadInst->addClause(TypeInfo);
- <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
- C++ programs</a>, preventing intermixing between C++ compiled by the CBE
- and C++ code compiled with <tt>llc</tt> or native compilers.</li>
+<i><b>// Adding a C++ catch-all</b></i>
+LPadInst->addClause(Constant::getNullValue(Builder.getInt8PtrTy()));
- <li>The C backend does not support all exception handling constructs.</li>
+<i><b>// Adding a cleanup</b></i>
+LPadInst->setCleanup(true);
- <li>The C backend does not support arbitrary precision integers.</li>
-</ul>
+<i><b>// Adding a filter clause</b></i>
+std::vector<Constant*> TypeInfos;
+Constant *TypeInfo = getFilterTypeInfo();
+TypeInfos.push_back(Builder.CreateBitCast(TypeInfo, Builder.getInt8PtrTy()));
+ArrayType *FilterTy = ArrayType::get(Int8PtrTy, TypeInfos.size());
+LPadInst->addClause(ConstantArray::get(FilterTy, TypeInfos));
+</pre>
</div>
+<p>Converting from using the <code>@llvm.eh.resume</code> intrinsic to
+ the <code>resume</code> instruction is trivial. It takes the exception
+ pointer and exception selector values returned by
+ the <code>landingpad</code> instruction:</p>
-<!-- ======================================================================= -->
-<h3>
- <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
-</h3>
-
-<div>
-
-<p><b>LLVM 2.9 was the last release of llvm-gcc.</b></p>
-
-<p>llvm-gcc is generally very stable for the C family of languages. The only
- major language feature of GCC not supported by llvm-gcc is the
- <tt>__builtin_apply</tt> family of builtins. However, some extensions
- are only supported on some targets. For example, trampolines are only
- supported on some targets (these are used when you take the address of a
- nested function).</p>
-
-<p>Fortran support generally works, but there are still several unresolved bugs
- in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
- tools/gfortran component for details. Note that llvm-gcc is missing major
- Fortran performance work in the frontend and library that went into GCC after
- 4.2. If you are interested in Fortran, we recommend that you consider using
- <a href="#dragonegg">dragonegg</a> instead.</p>
-
-<p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
- actively maintained. If you are interested in Ada, we recommend that you
- consider using <a href="#dragonegg">dragonegg</a> instead.</p>
-
-</div>
-
+<div class="doc_code">
+<pre>
+Type *UnwindDataTy = StructType::get(Builder.getInt8PtrTy(),
+ Builder.getInt32Ty(), NULL);
+Value *UnwindData = UndefValue::get(UnwindDataTy);
+Value *ExcPtr = Builder.CreateLoad(getExceptionObjSlot());
+Value *ExcSel = Builder.CreateLoad(getExceptionSelSlot());
+UnwindData = Builder.CreateInsertValue(UnwindData, ExcPtr, 0, "exc_ptr");
+UnwindData = Builder.CreateInsertValue(UnwindData, ExcSel, 1, "exc_sel");
+Builder.CreateResume(UnwindData);
+</pre>
</div>
-<!-- *********************************************************************** -->
-<h2>
- <a name="additionalinfo">Additional Information</a>
-</h2>
-<!-- *********************************************************************** -->
-<div>
-<p>A wide variety of additional information is available on
- the <a href="http://llvm.org/">LLVM web page</a>, in particular in
- the <a href="http://llvm.org/docs/">documentation</a> section. The web page
- also contains versions of the API documentation which is up-to-date with the
- Subversion version of the source code. You can access versions of these
- documents specific to this release by going into the "<tt>llvm/doc/</tt>"
- directory in the LLVM tree.</p>
-<p>If you have any questions or comments about LLVM, please feel free to contact
- us via the <a href="http://llvm.org/docs/#maillist"> mailing lists</a>.</p>
+ -->
-</div>
<!-- *********************************************************************** -->
projects / oota-llvm.git / blobdiff