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Commit b6316e8a authored by Bill Wendling's avatar Bill Wendling
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Update the release notes.

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......@@ -5,11 +5,11 @@
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta encoding="utf8">
<link rel="stylesheet" href="llvm.css" type="text/css">
<title>LLVM 2.8 Release Notes</title>
<title>LLVM 2.9 Release Notes</title>
</head>
<body>
<div class="doc_title">LLVM 2.8 Release Notes</div>
<h1 class="doc_title">LLVM 2.9 Release Notes</h1>
<img align=right src="http://llvm.org/img/DragonSmall.png"
width="136" height="136" alt="LLVM Dragon Logo">
......@@ -17,8 +17,8 @@
<ol>
<li><a href="#intro">Introduction</a></li>
<li><a href="#subproj">Sub-project Status Update</a></li>
<li><a href="#externalproj">External Projects Using LLVM 2.8</a></li>
<li><a href="#whatsnew">What's New in LLVM 2.8?</a></li>
<li><a href="#externalproj">External Projects Using LLVM 2.9</a></li>
<li><a href="#whatsnew">What's New in LLVM 2.9?</a></li>
<li><a href="GettingStarted.html">Installation Instructions</a></li>
<li><a href="#knownproblems">Known Problems</a></li>
<li><a href="#additionalinfo">Additional Information</a></li>
......@@ -29,23 +29,23 @@
</div>
<!--
<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.9
release.<br>
You may prefer the
<a href="http://llvm.org/releases/2.7/docs/ReleaseNotes.html">LLVM 2.7
<a href="http://llvm.org/releases/2.8/docs/ReleaseNotes.html">LLVM 2.8
Release Notes</a>.</h1>
-->
-->
<!-- *********************************************************************** -->
<div class="doc_section">
<h1>
<a name="intro">Introduction</a>
</div>
</h1>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>This document contains the release notes for the LLVM Compiler
Infrastructure, release 2.8. Here we describe the status of LLVM, including
Infrastructure, release 2.9. Here we describe the status of LLVM, including
major improvements from the previous release and significant known problems.
All LLVM releases may be downloaded from the <a
href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
......@@ -62,36 +62,25 @@ current one. To see the release notes for a specific release, please see the
<a href="http://llvm.org/releases/">releases page</a>.</p>
</div>
<!--
Almost dead code.
include/llvm/Analysis/LiveValues.h => Dan
lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
GEPSplitterPass
-->
<!-- Features that need text if they're finished for 2.9:
<!-- Features that need text if they're finished for 3.1:
ARM EHABI
combiner-aa?
strong phi elim
loop dependence analysis
TBAA
CorrelatedValuePropagation
lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
-->
<!-- Announcement, lldb, libc++ -->
<!-- *********************************************************************** -->
<div class="doc_section">
<h1>
<a name="subproj">Sub-project Status Update</a>
</div>
</h1>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>
The LLVM 2.8 distribution currently consists of code from the core LLVM
The LLVM 2.9 distribution currently consists of code from the core LLVM
repository (which roughly includes the LLVM optimizers, code generators
and supporting tools), the Clang repository and the llvm-gcc repository. In
addition to this code, the LLVM Project includes other sub-projects that are in
......@@ -102,9 +91,9 @@ development. Here we include updates on these subprojects.
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
</div>
</h2>
<div class="doc_text">
......@@ -115,110 +104,61 @@ standards, fast compilation, and low memory use. Like LLVM, Clang provides a
modular, library-based architecture that makes it suitable for creating or
integrating with other development tools. Clang is considered a
production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
(32- and 64-bit), and for darwin-arm targets.</p>
<p>In the LLVM 2.8 time-frame, the Clang team has made many improvements:</p>
<ul>
<li>Clang C++ is now feature-complete with respect to the ISO C++ 1998 and 2003 standards.</li>
<li>Added support for Objective-C++.</li>
<li>Clang now uses LLVM-MC to directly generate object code and to parse inline assembly (on Darwin).</li>
<li>Introduced many new warnings, including <code>-Wmissing-field-initializers</code>, <code>-Wshadow</code>, <code>-Wno-protocol</code>, <code>-Wtautological-compare</code>, <code>-Wstrict-selector-match</code>, <code>-Wcast-align</code>, <code>-Wunused</code> improvements, and greatly improved format-string checking.</li>
<li>Introduced the "libclang" library, a C interface to Clang intended to support IDE clients.</li>
<li>Added support for <code>#pragma GCC visibility</code>, <code>#pragma align</code>, and others.</li>
<li>Added support for SSE, AVX, ARM NEON, and AltiVec.</li>
<li>Improved support for many Microsoft extensions.</li>
<li>Implemented support for blocks in C++.</li>
<li>Implemented precompiled headers for C++.</li>
<li>Improved abstract syntax trees to retain more accurate source information.</li>
<li>Added driver support for handling LLVM IR and bitcode files directly.</li>
<li>Major improvements to compiler correctness for exception handling.</li>
<li>Improved generated code quality in some areas:
<ul>
<li>Good code generation for X86-32 and X86-64 ABI handling.</li>
<li>Improved code generation for bit-fields, although important work remains.</li>
</ul>
</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="clangsa">Clang Static Analyzer</a>
</div>
<div class="doc_text">
<p>The <a href="http://clang-analyzer.llvm.org/">Clang Static Analyzer</a>
project is an effort to use static source code analysis techniques to
automatically find bugs in C and Objective-C programs (and hopefully <a
href="http://clang-analyzer.llvm.org/dev_cxx.html">C++ in the
future</a>!). The tool is very good at finding bugs that occur on specific
paths through code, such as on error conditions.</p>
<p>The LLVM 2.8 release fixes a number of bugs and slightly improves precision
over 2.7, but there are no major new features in the release.
(32- and 64-bit), and for darwin/arm targets.</p>
<p>In the LLVM 2.9 time-frame, the Clang team has made many improvements in C,
C++ and Objective-C support. C++ support is now generally rock solid, has
been exercised on a broad variety of code, and has several new <a
href="http://clang.llvm.org/cxx_status.html#cxx0x">C++'0x features</a>
implemented (such as rvalue references and variadic templates). LLVM 2.9 has
also brought in a large range of bug fixes and minor features (e.g. __label__
support), and is much more compatible with the Linux Kernel.</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 issue.
</p>
<ul>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a>
</div>
<h2>
<a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
</h2>
<div class="doc_text">
<p>
<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
gcc-4.5. Unlike llvm-gcc, dragonegg in theory does not require any gcc-4.5
modifications whatsoever (currently one small patch is needed) thanks to the
new <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>.
DragonEgg is a gcc plugin that makes gcc-4.5 use the LLVM optimizers and code
generators instead of gcc's, just like with llvm-gcc.
<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>
<p>
DragonEgg is still a work in progress, but it is able to compile a lot of code,
for example all of gcc, LLVM and clang. Currently Ada, C, C++ and Fortran work
well, while all other languages either don't work at all or only work poorly.
For the moment only the x86-32 and x86-64 targets are supported, and only on
linux and darwin (darwin may need additional gcc patches).
</p>
<p>
The 2.8 release has the following notable changes:
The 2.9 release has the following notable changes:
<ul>
<li>The plugin loads faster due to exporting fewer symbols.</li>
<li>Additional vector operations such as addps256 are now supported.</li>
<li>Ada global variables with no initial value are no longer zero initialized,
resulting in better optimization.</li>
<li>The '-fplugin-arg-dragonegg-enable-gcc-optzns' flag now runs all gcc
optimizers, rather than just a handful.</li>
<li>Fortran programs using common variables now link correctly.</li>
<li>GNU OMP constructs no longer crash the compiler.</li>
<li>The plugin is much more stable when compiling Fortran.</li>
<li>Inline assembly where an asm output is tied to an input of a different size
is now supported in many more cases.</li>
<li>Basic support for the __float128 type was added. It is now possible to
generate LLVM IR from programs using __float128 but code generation does not
work yet.</li>
<li>Compiling Java programs no longer systematically crashes the plugin.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
</div>
<div class="doc_text">
<p>
The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
just-in-time compilation. As of LLVM 2.8, VMKit now supports copying garbage
collectors, and can be configured to use MMTk's copy mark-sweep garbage
collector. In LLVM 2.8, the VMKit .NET VM is no longer being maintained.
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
</div>
</h2>
<div class="doc_text">
<p>
......@@ -231,19 +171,20 @@ function. The compiler-rt library provides highly optimized implementations of
this and other low-level routines (some are 3x faster than the equivalent
libgcc routines).</p>
<p>
All of the code in the compiler-rt project is available under the standard LLVM
License, a "BSD-style" license. New in LLVM 2.8, compiler_rt now supports
soft floating point (for targets that don't have a real floating point unit),
and includes an extensive testsuite for the "blocks" language feature and the
blocks runtime included in compiler_rt.</p>
<p>In the LLVM 2.9 timeframe, compiler_rt has had several minor changes for
better ARM support, and a fairly major license change. All of the code in the
compiler-rt project is now <a href="DeveloperPolicy.html#license">dual
licensed</a> under MIT and UIUC license, which allows you to use compiler-rt
in applications without the binary copyright reproduction clause. If you
prefer the LLVM/UIUC license, you are free to continue using it under that
license as well.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="lldb">LLDB: Low Level Debugger</a>
</div>
</h2>
<div class="doc_text">
<p>
......@@ -254,18 +195,18 @@ libraries in the larger LLVM Project, such as the Clang expression parser, the
LLVM disassembler and the LLVM JIT.</p>
<p>
LLDB is in early development and not included as part of the LLVM 2.8 release,
but is mature enough to support basic debugging scenarios on Mac OS X in C,
Objective-C and C++. We'd really like help extending and expanding LLDB to
support new platforms, new languages, new architectures, and new features.
</p>
LLDB is has advanced by leaps and bounds in the 2.9 timeframe. It is
dramatically more stable and useful, and includes both a new <a
href="http://lldb.llvm.org/tutorial.html">tutorial</a> and a <a
href="http://lldb.llvm.org/lldb-gdb.html">side-by-side comparison with
GDB</a>.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="libc++">libc++: C++ Standard Library</a>
</div>
</h2>
<div class="doc_text">
<p>
......@@ -275,19 +216,54 @@ ground up to specifically target the forthcoming C++'0X standard and focus on
delivering great performance.</p>
<p>
As of the LLVM 2.8 release, libc++ is virtually feature complete, but would
benefit from more testing and better integration with Clang++. It is also
looking forward to the C++ committee finalizing the C++'0x standard.
In the LLVM 2.9 timeframe, libc++ has had numerous bugs fixed, and is now being
co-developed with Clang's C++'0x mode.</p>
<p>
Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
licensed</a> under the MIT and UIUC license, allowing it to be used more
permissively.
</p>
</div>
<!--=========================================================================-->
<h2>
<a name="LLBrowse">LLBrowse: IR Browser</a>
</h2>
<div class="doc_text">
<p>
<a href="http://llvm.org/svn/llvm-project/llbrowse/trunk/doc/LLBrowse.html">
LLBrowse</a> is an interactive viewer for LLVM modules. It can load any LLVM
module and displays its contents as an expandable tree view, facilitating an
easy way to inspect types, functions, global variables, or metadata nodes. It
is fully cross-platform, being based on the popular wxWidgets GUI toolkit.
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
<h2>
<a name="vmkit">VMKit</a>
</h2>
<div class="doc_text">
<p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
just-in-time compilation. As of LLVM 2.9, 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>
<!--=========================================================================-->
<!--
<h2>
<a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
</h2>
<div class="doc_text">
<p>
......@@ -298,171 +274,145 @@ states. This allows it to construct testcases that lead to faults and can even
be used to verify some algorithms.
</p>
<p>Although KLEE does not have any major new features as of 2.8, we have made
various minor improvements, particular to ease development:</p>
<ul>
<li>Added support for LLVM 2.8. KLEE currently maintains compatibility with
LLVM 2.6, 2.7, and 2.8.</li>
<li>Added a buildbot for 2.6, 2.7, and trunk. A 2.8 buildbot will be coming
soon following release.</li>
<li>Fixed many C++ code issues to allow building with Clang++. Mostly
complete, except for the version of MiniSAT which is inside the KLEE STP
version.</li>
<li>Improved support for building with separate source and build
directories.</li>
<li>Added support for "long double" on x86.</li>
<li>Initial work on KLEE support for using 'lit' test runner instead of
DejaGNU.</li>
<li>Added <tt>configure</tt> support for using an external version of
STP.</li>
</ul>
</div>
<p>UPDATE!</p>
</div>-->
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="externalproj">External Open Source Projects Using LLVM 2.8</a>
</div>
<h1>
<a name="externalproj">External Open Source Projects Using LLVM 2.9</a>
</h1>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>An exciting aspect of LLVM is that it is used as an enabling technology for
a lot of other language and tools projects. This section lists some of the
projects that have already been updated to work with LLVM 2.8.</p>
projects that have already been updated to work with LLVM 2.9.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="tce">TTA-based Codesign Environment (TCE)</a>
</div>
<h2>Crack Programming Language</h2>
<div class="doc_text">
<p>
<a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing
application-specific processors (ASP) based on the Transport triggered
architecture (TTA). The toolset provides a complete co-design flow from C/C++
programs down to synthesizable VHDL and parallel program binaries. Processor
customization points include the register files, function units, supported
operations, and the interconnection network.</p>
<p>TCE uses llvm-gcc/Clang and LLVM for C/C++ language support, target
independent optimizations and also for parts of code generation. It generates
new LLVM-based code generators "on the fly" for the designed TTA processors and
loads them in to the compiler backend as runtime libraries to avoid per-target
recompilation of larger parts of the compiler chain.</p>
<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>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="Horizon">Horizon Bytecode Compiler</a>
</div>
<h2>TTA-based Codesign Environment (TCE)</h2>
<div class="doc_text">
<p>
<a href="http://www.quokforge.org/projects/horizon">Horizon</a> is a bytecode
language and compiler written on top of LLVM, intended for producing
single-address-space managed code operating systems that
run faster than the equivalent multiple-address-space C systems.
More in-depth blurb is available on the <a
href="http://www.quokforge.org/projects/horizon/wiki/Wiki">wiki</a>.</p>
<p>TCE is a toolset for designing application-specific processors (ASP) based on
the Transport triggered architecture (TTA). The toolset provides a complete
co-design flow from C/C++ programs down to synthesizable VHDL and parallel
program binaries. Processor customization points include the register files,
function units, supported operations, and the interconnection network.</p>
<p>TCE uses Clang and LLVM for C/C++ language support, target independent
optimizations and also for parts of code generation. It generates new LLVM-based
code generators "on the fly" for the designed TTA processors and loads them in
to the compiler backend as runtime libraries to avoid per-target recompilation
of larger parts of the compiler chain.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="clamav">Clam AntiVirus</a>
<h2>PinaVM</h2>
<div class="doc_text">
<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>
<!--=========================================================================-->
<h2>Pure</h2>
<div class="doc_text">
<p>
<a href="http://www.clamav.net">Clam AntiVirus</a> is an open source (GPL)
anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail
gateways. Since version 0.96 it has <a
href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode
signatures</a> that allow writing detections for complex malware. It
uses LLVM's JIT to speed up the execution of bytecode on
X86, X86-64, PPC32/64, falling back to its own interpreter otherwise.
The git version was updated to work with LLVM 2.8.
</p>
<p>The <a
href="http://git.clamav.net/gitweb?p=clamav-bytecode-compiler.git;a=blob_plain;f=docs/user/clambc-user.pdf">
ClamAV bytecode compiler</a> uses Clang and LLVM to compile a C-like
language, insert runtime checks, and generate ClamAV bytecode.</p>
<p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
algebraic/functional
programming language based on term rewriting. Programs are collections
of equations which are used to evaluate expressions in a symbolic
fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
programs to fast native code. Pure offers dynamic typing, eager and lazy
evaluation, lexical closures, a hygienic macro system (also based on
term rewriting), built-in list and matrix support (including list and
matrix comprehensions) and an easy-to-use interface to C and other
programming 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 0.47 has been tested and is known to work with LLVM 2.9
(and continues to work with older LLVM releases &gt;= 2.5).</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="pure">Pure</a>
</div>
<h2 id="icedtea">IcedTea Java Virtual Machine Implementation</h2>
<div class="doc_text">
<p>
<a href="http://pure-lang.googlecode.com/">Pure</a>
is an algebraic/functional
programming language based on term rewriting. Programs are collections
of equations which are used to evaluate expressions in a symbolic
fashion. Pure offers dynamic typing, eager and lazy evaluation, lexical
closures, a hygienic macro system (also based on term rewriting),
built-in list and matrix support (including list and matrix
comprehensions) and an easy-to-use C interface. The interpreter uses
LLVM as a backend to JIT-compile Pure programs to fast native code.</p>
<p>Pure versions 0.44 and later have been tested and are known to work with
LLVM 2.8 (and continue to work with older LLVM releases >= 2.5).</p>
<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 2.9 (and continue to work with older LLVM
releases &gt;= 2.6 as well).</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="GHC">Glasgow Haskell Compiler (GHC)</a>
</div>
<h2>Glasgow Haskell Compiler (GHC)</h2>
<div class="doc_text">
<p>
<a href="http://www.haskell.org/ghc/">GHC</a> is an open source,
state-of-the-art programming suite for
Haskell, a standard lazy functional programming language. It includes
an optimizing static compiler generating good code for a variety of
<p>GHC is an open source, state-of-the-art programming suite for Haskell,
a standard lazy functional programming language. It includes an
optimizing static compiler generating good code for a variety of
platforms, together with an interactive system for convenient, quick
development.</p>
<p>In addition to the existing C and native code generators, GHC 7.0 now
supports an <a
href="http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/Backends/LLVM">LLVM
code generator</a>. GHC supports LLVM 2.7 and later.</p>
supports an LLVM code generator. GHC supports LLVM 2.7 and later.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="Clay">Clay Programming Language</a>
</div>
<h2>Polly - Polyhedral optimizations for LLVM</h2>
<div class="doc_text">
<p>
<a href="http://tachyon.in/clay/">Clay</a> is a new systems programming
language that is specifically designed for generic programming. It makes
generic programming very concise thanks to whole program type propagation. It
uses LLVM as its backend.</p>
<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>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="llvm-py">llvm-py Python Bindings for LLVM</a>
</div>
<h2>Rubinius</h2>
<div class="doc_text">
<p>
<a href="http://www.mdevan.org/llvm-py/">llvm-py</a> has been updated to work
with LLVM 2.8. llvm-py provides Python bindings for LLVM, allowing you to write a
compiler backend or a VM in Python.</p>
<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>
</div>
......@@ -477,118 +427,14 @@ compiler backend or a VM in Python.</p>
audio signal processing. The name FAUST stands for Functional AUdio STream. Its
programming model combines two approaches: functional programming and block
diagram composition. In addition with the C, C++, JAVA output formats, the
Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7 and
2.8.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="jade">Jade Just-in-time Adaptive Decoder Engine</a>
</div>
<div class="doc_text">
<p><a
href="http://sourceforge.net/apps/trac/orcc/wiki/JadeDocumentation">Jade</a>
(Just-in-time Adaptive Decoder Engine) is a generic video decoder engine using
LLVM for just-in-time compilation of video decoder configurations. Those
configurations are designed by MPEG Reconfigurable Video Coding (RVC) committee.
MPEG RVC standard is built on a stream-based dataflow representation of
decoders. It is composed of a standard library of coding tools written in
RVC-CAL language and a dataflow configuration &#8212; block diagram &#8212;
of a decoder.</p>
<p>Jade project is hosted as part of the <a href="http://orcc.sf.net">Open
RVC-CAL Compiler</a> and requires it to translate the RVC-CAL standard library
of video coding tools into an LLVM assembly code.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="neko_llvm_jit">LLVM JIT for Neko VM</a>
</div>
<div class="doc_text">
<p><a href="http://github.com/vava/neko_llvm_jit">Neko LLVM JIT</a>
replaces the standard Neko JIT with an LLVM-based implementation. While not
fully complete, it is already providing a 1.5x speedup on 64-bit systems.
Neko LLVM JIT requires LLVM 2.8 or later.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="crack">Crack Scripting Language</a>
</div>
<div class="doc_text">
<p>
<a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide
the ease of development of a scripting language with the performance of a
compiled language. The language derives concepts from C++, Java and Python,
incorporating object-oriented programming, operator overloading and strong
typing. Crack 0.2 works with LLVM 2.7, and the forthcoming Crack 0.2.1 release
builds on LLVM 2.8.</p>
Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7-2.9.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="DresdenTM">Dresden TM Compiler (DTMC)</a>
</div>
<div class="doc_text">
<p>
<a href="http://tm.inf.tu-dresden.de">DTMC</a> provides support for
Transactional Memory, which is an easy-to-use and efficient way to synchronize
accesses to shared memory. Transactions can contain normal C/C++ code (e.g.,
<code>__transaction { list.remove(x); x.refCount--; }</code>) and will be executed
virtually atomically and isolated from other transactions.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="Kai">Kai Programming Language</a>
</div>
<div class="doc_text">
<p>
<a href="http://www.oriontransfer.co.nz/research/kai">Kai</a> (Japanese 会 for
meeting/gathering) is an experimental interpreter that provides a highly
extensible runtime environment and explicit control over the compilation
process. Programs are defined using nested symbolic expressions, which are all
parsed into first-class values with minimal intrinsic semantics. Kai can
generate optimised code at run-time (using LLVM) in order to exploit the nature
of the underlying hardware and to integrate with external software libraries.
It is a unique exploration into world of dynamic code compilation, and the
interaction between high level and low level semantics.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="OSL">OSL: Open Shading Language</a>
</div>
<div class="doc_text">
<p>
<a href="http://code.google.com/p/openshadinglanguage/">OSL</a> is a shading
language designed for use in physically based renderers and in particular
production rendering. By using LLVM instead of the interpreter, it was able to
meet its performance goals (&gt;= C-code) while retaining the benefits of
runtime specialization and a portable high-level language.
</p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="whatsnew">What's New in LLVM 2.8?</a>
</div>
<h1>
<a name="whatsnew">What's New in LLVM 2.9?</a>
</h1>
<!-- *********************************************************************** -->
<div class="doc_text">
......@@ -601,60 +447,66 @@ in this section.
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="majorfeatures">Major New Features</a>
</div>
</h2>
<div class="doc_text">
<p>LLVM 2.8 includes several major new capabilities:</p>
<p>LLVM 2.9 includes several major new capabilities:</p>
<ul>
<li>As mentioned above, <a href="#libc++">libc++</a> and <a
href="#lldb">LLDB</a> are major new additions to the LLVM collective.</li>
<li>LLVM 2.8 now has pretty decent support for debugging optimized code. You
should be able to reliably get debug info for function arguments, assuming
that the value is actually available where you have stopped.</li>
<li>A new 'llvm-diff' tool is available that does a semantic diff of .ll
files.</li>
<li>The <a href="#mc">MC subproject</a> has made major progress in this release.
Direct .o file writing support for darwin/x86[-64] is now reliable and
support for other targets and object file formats are in progress.</li>
</ul>
<li>Type Based Alias Analysis (TBAA) is now implemented and turned on by default
in Clang. This allows substantially better load/store optimization in some
cases. TBAA can be disabled by passing -fno-strict-aliasing.
</li>
<li>This release has seen a continued focus on quality of debug information.
LLVM now generates much higher fidelity debug information, particularly when
debugging optimized code.</li>
<li>Inline assembly now supports multiple alternative constraints.</li>
<li>A new backend for the NVIDIA PTX virtual ISA (used to target its GPUs) is
under rapid development. It is not generally useful in 2.9, but is making
rapid progress.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="coreimprovements">LLVM IR and Core Improvements</a>
</div>
</h2>
<div class="doc_text">
<p>LLVM IR has several new features for better support of new targets and that
expose new optimization opportunities:</p>
<ul>
<li>The <a href="LangRef.html#int_libc">memcpy, memmove, and memset</a>
intrinsics now take address space qualified pointers and a bit to indicate
whether the transfer is "<a href="LangRef.html#volatile">volatile</a>" or not.
</li>
<li>Per-instruction debug info metadata is much faster and uses less memory by
using the new DebugLoc class.</li>
<li>LLVM IR now has a more formalized concept of "<a
href="LangRef.html#trapvalues">trap values</a>", which allow the optimizer
to optimize more aggressively in the presence of undefined behavior, while
still producing predictable results.</li>
<li>LLVM IR now supports two new <a href="LangRef.html#linkage">linkage
types</a> (linker_private_weak and linker_private_weak_def_auto) which map
onto some obscure MachO concepts.</li>
<li>The <a href="LangRef.html#bitwiseops">udiv, ashr, lshr, and shl</a>
instructions now have support exact and nuw/nsw bits to indicate that they
don't overflow or shift out bits. This is useful for optimization of <a
href="http://llvm.org/PR8862">pointer differences</a> and other cases.</li>
<li>LLVM IR now supports the <a href="LangRef.html#globalvars">unnamed_addr</a>
attribute to indicate that constant global variables with identical
initializers can be merged. This fixed <a href="http://llvm.org/PR8927">an
issue</a> where LLVM would incorrectly merge two globals which were supposed
to have distinct addresses.</li>
<li>The new <a href="LangRef.html#fnattrs">hotpatch attribute</a> has been added
to allow runtime patching of functions.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="optimizer">Optimizer Improvements</a>
</div>
</h2>
<div class="doc_text">
......@@ -662,45 +514,67 @@ expose new optimization opportunities:</p>
release includes a few major enhancements and additions to the optimizers:</p>
<ul>
<li>As mentioned above, the optimizer now has support for updating debug
information as it goes. A key aspect of this is the new <a
href="SourceLevelDebugging.html#format_common_value">llvm.dbg.value</a>
intrinsic. This intrinsic represents debug info for variables that are
promoted to SSA values (typically by mem2reg or the -scalarrepl passes).</li>
<li>The JumpThreading pass is now much more aggressive about implied value
relations, allowing it to thread conditions like "a == 4" when a is known to
be 13 in one of the predecessors of a block. It does this in conjunction
with the new LazyValueInfo analysis pass.</li>
<li>The new RegionInfo analysis pass identifies single-entry single-exit regions
in the CFG. You can play with it with the "opt -regions -analyze" or
"opt -view-regions" commands.</li>
<li>The loop optimizer has significantly improved strength reduction and analysis
capabilities. Notably it is able to build on the trap value and signed
integer overflow information to optimize &lt;= and &gt;= loops.</li>
<li>The CallGraphSCCPassManager now has some basic support for iterating within
an SCC when a optimizer devirtualizes a function call. This allows inlining
through indirect call sites that are devirtualized by store-load forwarding
and other optimizations.</li>
<li>The new <A href="Passes.html#loweratomic">-loweratomic</a> pass is available
to lower atomic instructions into their non-atomic form. This can be useful
to optimize generic code that expects to run in a single-threaded
environment.</li>
</ul>
<li>Link Time Optimization (LTO) has been improved to use MC for parsing inline
assembly and now can build large programs like Firefox 4 on both Mac OS X and
Linux.</li>
<li>The new -loop-idiom pass recognizes memset/memcpy loops (and memset_pattern
on darwin), turning them into library calls, which are typically better
optimized than inline code. If you are building a libc and notice that your
memcpy and memset functions are compiled into infinite recursion, please build
with -ffreestanding or -fno-builtin to disable this pass.</li>
<li>A new -early-cse pass does a fast pass over functions to fold constants,
simplify expressions, perform simple dead store elimination, and perform
common subexpression elimination. It does a good job at catching some of the
trivial redundancies that exist in unoptimized code, making later passes more
effective.</li>
<li>A new -loop-instsimplify pass is used to clean up loop bodies in the loop
optimizer.</li>
<li>The new TargetLibraryInfo interface allows mid-level optimizations to know
whether the current target's runtime library has certain functions. For
example, the optimizer can now transform integer-only printf calls to call
iprintf, allowing reduced code size for embedded C libraries (e.g. newlib).
</li>
<li>LLVM has a new <a href="WritingAnLLVMPass.html#RegionPass">RegionPass</a>
infrastructure for region-based optimizations.</li>
<li>Several optimizer passes have been substantially sped up:
GVN is much faster on functions with deep dominator trees and lots of basic
blocks. The dominator tree and dominance frontier passes are much faster to
compute, and preserved by more passes (so they are computed less often). The
-scalar-repl pass is also much faster and doesn't use DominanceFrontier.
</li>
<!--
<p>In addition to these features that are done in 2.8, there is preliminary
support in the release for Type Based Alias Analysis
Preliminary work on TBAA but not usable in 2.8.
New CorrelatedValuePropagation pass, not on by default in 2.8 yet.
-->
<li>The Dead Store Elimination pass is more aggressive optimizing stores of
different types: e.g. a large store following a small one to the same address.
The MemCpyOptimizer pass handles several new forms of memcpy elimination.</li>
<li>LLVM now optimizes various idioms for overflow detection into check of the
flag register on various CPUs. For example, we now compile:
<pre>
unsigned long t = a+b;
if (t &lt; a) ...
</pre>
into:
<pre>
addq %rdi, %rbx
jno LBB0_2
</pre>
</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="mc">MC Level Improvements</a>
</div>
</h2>
<div class="doc_text">
<p>
......@@ -709,26 +583,39 @@ of problems in the realm of assembly, disassembly, object file format handling,
and a number of other related areas that CPU instruction-set level tools work
in.</p>
<p>The MC subproject has made great leaps in LLVM 2.8. For example, support for
directly writing .o files from LLC (and clang) now works reliably for
darwin/x86[-64] (including inline assembly support) and the integrated
assembler is turned on by default in Clang for these targets. This provides
improved compile times among other things.</p>
<ul>
<li>The entire compiler has converted over to using the MCStreamer assembler API
instead of writing out a .s file textually.</li>
<li>The "assembler parser" is far more mature than in 2.7, supporting a full
complement of directives, now supports assembler macros, etc.</li>
<li>The "assembler backend" has been completed, including support for relaxation
relocation processing and all the other things that an assembler does.</li>
<li>The MachO file format support is now fully functional and works.</li>
<li>The MC disassembler now fully supports ARM and Thumb. ARM assembler support
is still in early development though.</li>
<li>The X86 MC assembler now supports the X86 AES and AVX instruction set.</li>
<li>Work on ELF and COFF object files and ARM target support is well underway,
but isn't useful yet in LLVM 2.8. Please contact the llvmdev mailing list
if you're interested in this.</li>
<li>ELF MC support has matured enough for the integrated assembler to be turned
on by default in Clang on X86-32 and X86-64 ELF systems.</li>
<li>MC supports and CodeGen uses the <tt>.file</tt> and <tt>.loc</tt> directives
for producing line number debug info. This produces more compact line
tables and easier to read .s files.</li>
<li>MC supports the <tt>.cfi_*</tt> directives for producing DWARF
frame information, but it is still not used by CodeGen by default.</li>
<li>The MC assembler now generates much better diagnostics for common errors,
is much faster at matching instructions, is much more bug-compatible with
the GAS assembler, and is now generally useful for a broad range of X86
assembly.</li>
<li>We now have some basic <a href="CodeGenerator.html#mc">internals
documentation</a> for MC.</li>
<li>.td files can now specify assembler aliases directly with the <a
href="CodeGenerator.html#na_instparsing">MnemonicAlias and InstAlias</a>
tblgen classes.</li>
<li>LLVM now has an experimental format-independent object file manipulation
library (lib/Object). It supports both PE/COFF and ELF. The llvm-nm tool has
been extended to work with native object files, and the new llvm-objdump tool
supports disassembly of object files (but no relocations are displayed yet).
</li>
<li>Win32 PE-COFF support in the MC assembler has made a lot of progress in the
2.9 timeframe, but is still not generally useful.</li>
</ul>
<p>For more information, please see the <a
......@@ -736,13 +623,12 @@ href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
LLVM MC Project Blog Post</a>.
</p>
</div>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="codegen">Target Independent Code Generator Improvements</a>
</div>
</h2>
<div class="doc_text">
......@@ -751,343 +637,187 @@ infrastructure, which allows us to implement more aggressive algorithms and make
it run faster:</p>
<ul>
<li>The clang/gcc -momit-leaf-frame-pointer argument is now supported.</li>
<li>The clang/gcc -ffunction-sections and -fdata-sections arguments are now
supported on ELF targets (like GCC).</li>
<li>The MachineCSE pass is now tuned and on by default. It eliminates common
subexpressions that are exposed when lowering to machine instructions.</li>
<li>The "local" register allocator was replaced by a new "fast" register
allocator. This new allocator (which is often used at -O0) is substantially
faster and produces better code than the old local register allocator.</li>
<li>A new LLC "-regalloc=default" option is available, which automatically
chooses a register allocator based on the -O optimization level.</li>
<li>The common code generator code was modified to promote illegal argument and
return value vectors to wider ones when possible instead of scalarizing
them. For example, &lt;3 x float&gt; will now pass in one SSE register
instead of 3 on X86. This generates substantially better code since the
rest of the code generator was already expecting this.</li>
<li>The code generator uses a new "COPY" machine instruction. This speeds up
the code generator and eliminates the need for targets to implement the
isMoveInstr hook. Also, the copyRegToReg hook was renamed to copyPhysReg
and simplified.</li>
<li>The code generator now has a "LocalStackSlotPass", which optimizes stack
slot access for targets (like ARM) that have limited stack displacement
addressing.</li>
<li>A new "PeepholeOptimizer" is available, which eliminates sign and zero
extends, and optimizes away compare instructions when the condition result
is available from a previous instruction.</li>
<li>Atomic operations now get legalized into simpler atomic operations if not
natively supported, easing the implementation burden on targets.</li>
<li>We have added two new bottom-up pre-allocation register pressure aware schedulers:
<ol>
<li>The hybrid scheduler schedules aggressively to minimize schedule length when registers are available and avoid overscheduling in high pressure situations.</li>
<li>The instruction-level-parallelism scheduler schedules for maximum ILP when registers are available and avoid overscheduling in high pressure situations.</li>
</ol></li>
<li>The tblgen type inference algorithm was rewritten to be more consistent and
diagnose more target bugs. If you have an out-of-tree backend, you may
find that it finds bugs in your target description. This support also
allows limited support for writing patterns for instructions that return
multiple results (e.g. a virtual register and a flag result). The
'parallel' modifier in tblgen was removed, you should use the new support
for multiple results instead.</li>
<li>A new (experimental) "-rendermf" pass is available which renders a
MachineFunction into HTML, showing live ranges and other useful
details.</li>
<li>The new SubRegIndex tablegen class allows subregisters to be indexed
symbolically instead of numerically. If your target uses subregisters you
will need to adapt to use SubRegIndex when you upgrade to 2.8.</li>
<!-- SplitKit -->
<li>The -fast-isel instruction selection path (used at -O0 on X86) was rewritten
to work bottom-up on basic blocks instead of top down. This makes it
slightly faster (because the MachineDCE pass is not needed any longer) and
allows it to generate better code in some cases.</li>
<li>The pre-register-allocation (preRA) instruction scheduler models register
pressure much more accurately in some cases. This allows the adoption of more
aggressive scheduling heuristics without causing spills to be generated.
</li>
<li>LiveDebugVariables is a new pass that keeps track of debugging information
for user variables that are promoted to registers in optimized builds.</li>
<li>The scheduler now models operand latency and pipeline forwarding.</li>
<li>A major register allocator infrastructure rewrite is underway. It is not on
by default for 2.9 and you are not advised to use it, but it has made
substantial progress in the 2.9 timeframe:
<ul>
<li>A new -regalloc=basic "basic" register allocator can be used as a simple
fallback when debugging. It uses the new infrastructure.</li>
<li>New infrastructure is in place for live range splitting. "SplitKit" can
break a live interval into smaller pieces while preserving SSA form, and
SpillPlacement can help find the best split points. This is a work in
progress so the API is changing quickly.</li>
<li>The inline spiller has learned to clean up after live range splitting. It
can hoist spills out of loops, and it can eliminate redundant spills.</li>
<li>Rematerialization works with live range splitting.</li>
<li>The new "greedy" register allocator using live range splitting. This will
be the default register allocator in the next LLVM release, but it is not
turned on by default in 2.9.</li>
</ul>
</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="x86">X86-32 and X86-64 Target Improvements</a>
</div>
</h2>
<div class="doc_text">
<p>New features and major changes in the X86 target include:
</p>
<ul>
<li>The X86 backend now supports holding X87 floating point stack values
in registers across basic blocks, dramatically improving performance of code
that uses long double, and when targeting CPUs that don't support SSE.</li>
<li>The X86 backend now uses a SSEDomainFix pass to optimize SSE operations. On
Nehalem ("Core i7") and newer CPUs there is a 2 cycle latency penalty on
using a register in a different domain than where it was defined. This pass
optimizes away these stalls.</li>
<li>The X86 backend now promotes 16-bit integer operations to 32-bits when
possible. This avoids 0x66 prefixes, which are slow on some
microarchitectures and bloat the code on all of them.</li>
<li>The X86 backend now supports the Microsoft "thiscall" calling convention,
and a <a href="LangRef.html#callingconv">calling convention</a> to support
<a href="#GHC">ghc</a>.</li>
<li>The X86 backend supports a new "llvm.x86.int" intrinsic, which maps onto
the X86 "int $42" and "int3" instructions.</li>
<li>At the IR level, the &lt;2 x float&gt; datatype is now promoted and passed
around as a &lt;4 x float&gt; instead of being passed and returned as an MMX
vector. If you have a frontend that uses this, please pass and return a
&lt;2 x i32&gt; instead (using bitcasts).</li>
<li>When printing .s files in verbose assembly mode (the default for clang -S),
the X86 backend now decodes X86 shuffle instructions and prints human
readable comments after the most inscrutable of them, e.g.:
<pre>
insertps $113, %xmm3, %xmm0 <i># xmm0 = zero,xmm0[1,2],xmm3[1]</i>
unpcklps %xmm1, %xmm0 <i># xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1]</i>
pshufd $1, %xmm1, %xmm1 <i># xmm1 = xmm1[1,0,0,0]</i>
</pre>
<li>LLVM 2.9 includes a complete reimplementation of the MMX instruction set.
The reimplementation uses a new LLVM IR <a
href="LangRef.html#t_x86mmx">x86_mmx</a> type to ensure that MMX operations
are <em>only</em> generated from source that uses MMX builtin operations. With
this, random types like &lt;2 x i32&gt; are not turned into MMX operations
(which can be catastrophic without proper "emms" insertion). Because the X86
code generator always generates reliable code, the -disable-mmx flag is now
removed.
</li>
<li>X86 support for FS/GS relative loads and stores using <a
href="CodeGenerator.html#x86_memory">address space 256/257</a> works reliably
now.</li>
<li>LLVM 2.9 generates much better code in several cases by using adc/sbb to
avoid generation of conditional move instructions for conditional increment
and other idioms.</li>
<li>The X86 backend has adopted a new preRA scheduling mode, "list-ilp", to
shorten the height of instruction schedules without inducing register spills.
</li>
<li>The MC assembler supports 3dNow! and 3DNowA instructions.</li>
<li>Several bugs have been fixed for Windows x64 code generator.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="ARM">ARM Target Improvements</a>
</div>
</h2>
<div class="doc_text">
<p>New features of the ARM target include:
</p>
<ul>
<li>The ARM backend now optimizes tail calls into jumps.</li>
<li>Scheduling is improved through the new list-hybrid scheduler as well
as through better modeling of structural hazards.</li>
<li><a href="LangRef.html#int_fp16">Half float</a> instructions are now
supported.</li>
<li>NEON support has been improved to model instructions which operate onto
multiple consecutive registers more aggressively. This avoids lots of
extraneous register copies.</li>
<li>The ARM backend now uses a new "ARMGlobalMerge" pass, which merges several
global variables into one, saving extra address computation (all the global
variables can be accessed via same base address) and potentially reducing
register pressure.</li>
<li>The ARM backend has received many minor improvements and tweaks which lead
to substantially better performance in a wide range of different scenarios.
</li>
<li>The ARM backend now has a fast instruction selector, which dramatically
improves -O0 compile times.</li>
<li>The ARM backend has new tuning for Cortex-A8 and Cortex-A9 CPUs.</li>
<li>The __builtin_prefetch builtin (and llvm.prefetch intrinsic) is compiled
into prefetch instructions instead of being discarded.</li>
<li>The ARM NEON intrinsics have been substantially reworked to reduce
redundancy and improve code generation. Some of the major changes are:
<ol>
<li>
All of the NEON load and store intrinsics (llvm.arm.neon.vld* and
llvm.arm.neon.vst*) take an extra parameter to specify the alignment in bytes
of the memory being accessed.
</li>
<li>
The llvm.arm.neon.vaba intrinsic (vector absolute difference and
accumulate) has been removed. This operation is now represented using
the llvm.arm.neon.vabd intrinsic (vector absolute difference) followed by a
vector add.
</li>
<li>
The llvm.arm.neon.vabdl and llvm.arm.neon.vabal intrinsics (lengthening
vector absolute difference with and without accumulation) have been removed.
They are represented using the llvm.arm.neon.vabd intrinsic (vector absolute
difference) followed by a vector zero-extend operation, and for vabal,
a vector add.
</li>
<li>
The llvm.arm.neon.vmovn intrinsic has been removed. Calls of this intrinsic
are now replaced by vector truncate operations.
</li>
<li>
The llvm.arm.neon.vmovls and llvm.arm.neon.vmovlu intrinsics have been
removed. They are now represented as vector sign-extend (vmovls) and
zero-extend (vmovlu) operations.
</li>
<li>
The llvm.arm.neon.vaddl*, llvm.arm.neon.vaddw*, llvm.arm.neon.vsubl*, and
llvm.arm.neon.vsubw* intrinsics (lengthening vector add and subtract) have
been removed. They are replaced by vector add and vector subtract operations
where one (vaddw, vsubw) or both (vaddl, vsubl) of the operands are either
sign-extended or zero-extended.
</li>
<li>
The llvm.arm.neon.vmulls, llvm.arm.neon.vmullu, llvm.arm.neon.vmlal*, and
llvm.arm.neon.vmlsl* intrinsics (lengthening vector multiply with and without
accumulation and subtraction) have been removed. These operations are now
represented as vector multiplications where the operands are either
sign-extended or zero-extended, followed by a vector add for vmlal or a
vector subtract for vmlsl. Note that the polynomial vector multiply
intrinsic, llvm.arm.neon.vmullp, remains unchanged.
</li>
</ol>
</li>
<li> The ARM backend preRA scheduler now models machine resources at cycle
granularity. This allows the scheduler to both accurately model
instruction latency and avoid overcommitting functional units.</li>
<li>Countless ARM microoptimizations have landed in LLVM 2.9.</li>
</ul>
</div>
<!--=========================================================================-->
<h2>
<a name="OtherTS">Other Target Specific Improvements</a>
</h2>
<div class="doc_text">
<ul>
<li>MicroBlaze: major updates for aggressive delay slot filler, MC-based
assembly printing, assembly instruction parsing, ELF .o file emission, and MC
instruction disassembler have landed.</li>
<li>SPARC: Many improvements, including using the Y registers for
multiplications and addition of a simple delay slot filler.</li>
<li>PowerPC: The backend has been largely MC'ized and is ready to support
directly writing out mach-o object files. No one seems interested in finishing
this final step though.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<h2>
<a name="changes">Major Changes and Removed Features</a>
</div>
</h2>
<div class="doc_text">
<p>If you're already an LLVM user or developer with out-of-tree changes based
on LLVM 2.7, this section lists some "gotchas" that you may run into upgrading
on LLVM 2.8, this section lists some "gotchas" that you may run into upgrading
from the previous release.</p>
<ul>
<li>The build configuration machinery changed the output directory names. It
wasn't clear to many people that a "Release-Asserts" build was a release build
without asserts. To make this more clear, "Release" does not include
assertions and "Release+Asserts" does (likewise, "Debug" and
"Debug+Asserts").</li>
<li>The MSIL Backend was removed, it was unsupported and broken.</li>
<li>The ABCD, SSI, and SCCVN passes were removed. These were not fully
functional and their behavior has been or will be subsumed by the
LazyValueInfo pass.</li>
<li>The LLVM IR 'Union' feature was removed. While this is a desirable feature
for LLVM IR to support, the existing implementation was half baked and
barely useful. We'd really like anyone interested to resurrect the work and
finish it for a future release.</li>
<li>If you're used to reading .ll files, you'll probably notice that .ll file
dumps don't produce #uses comments anymore. To get them, run a .bc file
through "llvm-dis --show-annotations".</li>
<li>Target triples are now stored in a normalized form, and all inputs from
humans are expected to be normalized by Triple::normalize before being
stored in a module triple or passed to another library.</li>
</ul>
<li><b>This is the last release to support the llvm-gcc frontend.</b></li>
<li>LLVM has a new <a href="CodingStandards.html#ll_naming">naming
convention standard</a>, though the codebase hasn't fully adopted it yet.</li>
<li>The new DIBuilder class provides a simpler interface for front ends to
encode debug info in LLVM IR, and has replaced DIFactory.</li>
<li>LLVM IR and other tools always work on normalized target triples (which have
been run through <tt>Triple::normalize</tt>).</li>
<p>In addition, many APIs have changed in this release. Some of the major LLVM
API changes are:</p>
<ul>
<li>LLVM 2.8 changes the internal order of operands in <a
href="http://llvm.org/doxygen/classllvm_1_1InvokeInst.html"><tt>InvokeInst</tt></a>
and <a href="http://llvm.org/doxygen/classllvm_1_1CallInst.html"><tt>CallInst</tt></a>.
To be portable across releases, please use the <tt>CallSite</tt> class and the
high-level accessors, such as <tt>getCalledValue</tt> and
<tt>setUnwindDest</tt>.
</li>
<li>
You can no longer pass use_iterators directly to cast&lt;&gt; (and similar),
because these routines tend to perform costly dereference operations more
than once. You have to dereference the iterators yourself and pass them in.
</li>
<li>
llvm.memcpy.*, llvm.memset.*, llvm.memmove.* intrinsics take an extra
parameter now ("i1 isVolatile"), totaling 5 parameters, and the pointer
operands are now address-space qualified.
If you were creating these intrinsic calls and prototypes yourself (as opposed
to using Intrinsic::getDeclaration), you can use
UpgradeIntrinsicFunction/UpgradeIntrinsicCall to be portable across releases.
</li>
<li>
SetCurrentDebugLocation takes a DebugLoc now instead of a MDNode.
Change your code to use
SetCurrentDebugLocation(DebugLoc::getFromDILocation(...)).
</li>
<li>
The <tt>RegisterPass</tt> and <tt>RegisterAnalysisGroup</tt> templates are
considered deprecated, but continue to function in LLVM 2.8. Clients are
strongly advised to use the upcoming <tt>INITIALIZE_PASS()</tt> and
<tt>INITIALIZE_AG_PASS()</tt> macros instead.
</li>
<li>
The constructor for the Triple class no longer tries to understand odd triple
specifications. Frontends should ensure that they only pass valid triples to
LLVM. The Triple::normalize utility method has been added to help front-ends
deal with funky triples.
</li>
<li>
The signature of the <tt>GCMetadataPrinter::finishAssembly</tt> virtual
function changed: the <tt>raw_ostream</tt> and <tt>MCAsmInfo</tt> arguments
were dropped. GC plugins which compute stack maps must be updated to avoid
having the old definition overload the new signature.
</li>
<li>
The signature of <tt>MemoryBuffer::getMemBuffer</tt> changed. Unfortunately
calls intended for the old version still compile, but will not work correctly,
leading to a confusing error about an invalid header in the bitcode.
</li>
<li>
Some APIs were renamed:
<ul>
<li>llvm_report_error -&gt; report_fatal_error</li>
<li>llvm_install_error_handler -&gt; install_fatal_error_handler</li>
<li>llvm::DwarfExceptionHandling -&gt; llvm::JITExceptionHandling</li>
<li>VISIBILITY_HIDDEN -&gt; LLVM_LIBRARY_VISIBILITY</li>
</ul>
</li>
<li>The target triple x86_64--mingw64 is obsoleted. Use x86_64--mingw32
instead.</li>
<li>
Some public headers were renamed:
<ul>
<li><tt>llvm/Assembly/AsmAnnotationWriter.h</tt> was renamed
to <tt>llvm/Assembly/AssemblyAnnotationWriter.h</tt>
</li>
</ul>
<li>The PointerTracking pass has been removed from mainline, and moved to The
ClamAV project (its only client).</li>
<li>The LoopIndexSplit, LiveValues, SimplifyHalfPowrLibCalls, GEPSplitter, and
PartialSpecialization passes were removed. They were unmaintained,
buggy, or deemed to be a bad idea.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="devtree_changes">Development Infrastructure Changes</a>
</div>
<h2>
<a name="api_changes">Internal API Changes</a>
</h2>
<div class="doc_text">
<p>This section lists changes to the LLVM development infrastructure. This
mostly impacts users who actively work on LLVM or follow development on
mainline, but may also impact users who leverage the LLVM build infrastructure
or are interested in LLVM qualification.</p>
<p>In addition, many APIs have changed in this release. Some of the major
LLVM API changes are:</p>
<ul>
<li>The default for <tt>make check</tt> is now to use
the <a href="http://llvm.org/cmds/lit.html">lit</a> testing tool, which is
part of LLVM itself. You can use <tt>lit</tt> directly as well, or use
the <tt>llvm-lit</tt> tool which is created as part of a Makefile or CMake
build (and knows how to find the appropriate tools). See the <tt>lit</tt>
documentation and the <a href="http://blog.llvm.org/2009/12/lit-it.html">blog
post</a>, and <a href="http://llvm.org/bugs/show_bug.cgi?id=5217">PR5217</a>
for more information.</li>
<li>The LLVM <tt>test-suite</tt> infrastructure has a new "simple" test format
(<tt>make TEST=simple</tt>). The new format is intended to require only a
compiler and not a full set of LLVM tools. This makes it useful for testing
released compilers, for running the test suite with other compilers (for
performance comparisons), and makes sure that we are testing the compiler as
users would see it. The new format is also designed to work using reference
outputs instead of comparison to a baseline compiler, which makes it run much
faster and makes it less system dependent.</li>
<li>Significant progress has been made on a new interface to running the
LLVM <tt>test-suite</tt> (aka the LLVM "nightly tests") using
the <a href="http://llvm.org/docs/lnt">LNT</a> infrastructure. The LNT
interface to the <tt>test-suite</tt> brings significantly improved reporting
capabilities for monitoring the correctness and generated code quality
produced by LLVM over time.</li>
<li>include/llvm/System merged into include/llvm/Support.</li>
<li>The <a href="http://llvm.org/PR5207">llvm::APInt API</a> was significantly
cleaned up.</li>
<li>In the code generator, MVT::Flag was renamed to MVT::Glue to more accurately
describe its behavior.</li>
<li>The system_error header from C++0x was added, and is now pervasively used to
capture and handle i/o and other errors in LLVM.</li>
<li>The old sys::Path API has been deprecated in favor of the new PathV2 API,
which is more efficient and flexible.</li>
</ul>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<h1>
<a name="knownproblems">Known Problems</a>
</div>
</h1>
<!-- *********************************************************************** -->
<div class="doc_text">
......@@ -1100,9 +830,9 @@ there isn't already one.</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="experimental">Experimental features included with this release</a>
</div>
</h2>
<div class="doc_text">
......@@ -1114,18 +844,19 @@ components, please contact us on the <a
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
<ul>
<li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, SystemZ
<li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ
and XCore backends are experimental.</li>
<li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets
other than darwin-i386 and darwin-x86_64.</li>
other than darwin and ELF X86 systems.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="x86-be">Known problems with the X86 back-end</a>
</div>
</h2>
<div class="doc_text">
......@@ -1134,21 +865,31 @@ href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
all <a href="http://llvm.org/PR879">inline assembly that uses the X86
floating point stack</a>. It supports the 'f' and 't' constraints, but not
'u'.</li>
<li>Win64 code generation wasn't widely tested. Everything should work, but we
expect small issues to happen. Also, llvm-gcc cannot build the mingw64
runtime currently due to lack of support for the 'u' inline assembly
constraint and for X87 floating point inline assembly.</li>
<li>The X86-64 backend does not yet support the LLVM IR instruction
<tt>va_arg</tt>. Currently, front-ends support variadic
argument constructs on X86-64 by lowering them manually.</li>
<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>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="ppc-be">Known problems with the PowerPC back-end</a>
</div>
</h2>
<div class="doc_text">
......@@ -1160,9 +901,9 @@ compilation, and lacks support for debug information.</li>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="arm-be">Known problems with the ARM back-end</a>
</div>
</h2>
<div class="doc_text">
......@@ -1177,9 +918,9 @@ results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="sparc-be">Known problems with the SPARC back-end</a>
</div>
</h2>
<div class="doc_text">
......@@ -1191,9 +932,9 @@ results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="mips-be">Known problems with the MIPS back-end</a>
</div>
</h2>
<div class="doc_text">
......@@ -1204,9 +945,9 @@ results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="alpha-be">Known problems with the Alpha back-end</a>
</div>
</h2>
<div class="doc_text">
......@@ -1219,9 +960,9 @@ appropriate nops inserted to ensure restartability.</li>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="c-be">Known problems with the C back-end</a>
</div>
</h2>
<div class="doc_text">
......@@ -1242,12 +983,14 @@ Depending on it for anything serious is not advised.</p>
<!-- ======================================================================= -->
<div class="doc_subsection">
<h2>
<a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
</div>
</h2>
<div class="doc_text">
<p><b>LLVM 2.9 will be 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
......@@ -1268,9 +1011,9 @@ consider using <a href="#dragonegg">dragonegg</a> instead.</p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<h1>
<a name="additionalinfo">Additional Information</a>
</div>
</h1>
<!-- *********************************************************************** -->
<div class="doc_text">
......
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