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Commit 18665516 authored by Tanya Lattner's avatar Tanya Lattner
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Commit 2.7 release notes. 

Update getting started guide for 2.7

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......@@ -726,6 +726,7 @@ revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
subdirectories of the '<tt>tags</tt>' directory:</p>
<ul>
<li>Release 2.7: <b>RELEASE_27</b></li>
<li>Release 2.6: <b>RELEASE_26</b></li>
<li>Release 2.5: <b>RELEASE_25</b></li>
<li>Release 2.4: <b>RELEASE_24</b></li>
......
llvm/docs/ReleaseNotes.html
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......@@ -10,6 +10,9 @@
<div class="doc_title">LLVM 2.7 Release Notes</div>
<img align=right src="http://llvm.org/img/DragonSmall.png"
width="136" height="136" alt="LLVM Dragon Logo">
<ol>
<li><a href="#intro">Introduction</a></li>
<li><a href="#subproj">Sub-project Status Update</a></li>
......@@ -25,11 +28,12 @@
<p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
</div>
<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.7
<!--
<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
release.<br>
You may prefer the
<a href="http://llvm.org/releases/2.6/docs/ReleaseNotes.html">LLVM 2.6
Release Notes</a>.</h1>
<a href="http://llvm.org/releases/2.6/docs/ReleaseNotes.html">LLVM 2.7
Release Notes</a>.</h1>-->
<!-- *********************************************************************** -->
<div class="doc_section">
......@@ -48,8 +52,8 @@ href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
<p>For more information about LLVM, including information about the latest
release, please check out the <a href="http://llvm.org/">main LLVM
web site</a>. If you have questions or comments, the <a
href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
List</a> is a good place to send them.</p>
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
Mailing List</a> is a good place to send them.</p>
<p>Note that if you are reading this file from a Subversion checkout or the
main LLVM web page, this document applies to the <i>next</i> release, not the
......@@ -64,22 +68,17 @@ Almost dead code.
include/llvm/Analysis/LiveValues.h => Dan
lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
ABCD, SCCVN, GEPSplitterPass
ABCD, GEPSplitterPass
MSIL backend?
lib/Transforms/Utils/SSI.cpp -> ABCD depends on it.
-->
<!-- Features that need text if they're finished for 2.7:
gcc plugin.
combiner-aa?
strong phi elim
variable debug info for optimized code
postalloc scheduler: anti dependence breaking, hazard recognizer?
metadata
llvm.dbg.value: variable debug info for optimized code
loop dependence analysis
ELF Writer? How stable?
<li>PostRA scheduler improvements, ARM adoption (David Goodwin).</li>
2.7 supports the GDB 7.0 jit interfaces for debug info.
2.7 eliminates ADT/iterator.h
-->
<!-- for announcement email:
......@@ -88,8 +87,7 @@ Almost dead code.
compiler_rt
KLEE web page at klee.llvm.org
Many new papers added to /pubs/
Mention gcc plugin.
Mention gcc plugin.
-->
<!-- *********************************************************************** -->
......@@ -117,12 +115,49 @@ development. Here we include updates on these subprojects.
<div class="doc_text">
<p>The <a href="http://clang.llvm.org/">Clang project</a> is ...</p>
<p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
C++, and Objective-C languages. Clang aims to provide a better user experience
through expressive diagnostics, a high level of conformance to language
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 and Objective-C on x86 (32- and 64-bit).</p>
<p>In the LLVM 2.7 time-frame, the Clang team has made many improvements:</p>
<ul>
<li>...</li>
<li>C++ Support: Clang is now capable of self-hosting! While still
alpha-quality, Clang's C++ support has matured enough to build LLVM and Clang,
and C++ is now enabled by default. See the <a
href="http://clang.llvm.org/cxx_compatibility.html">Clang C++ compatibility
page</a> for common C++ migration issues.</li>
<li>Objective-C: Clang now includes experimental support for an updated
Objective-C ABI on non-Darwin platforms. This includes support for non-fragile
instance variables and accelerated proxies, as well as greater potential for
future optimisations. The new ABI is used when compiling with the
-fobjc-nonfragile-abi and -fgnu-runtime options. Code compiled with these
options may be mixed with code compiled with GCC or clang using the old GNU ABI,
but requires the libobjc2 runtime from the GNUstep project.</li>
<li>New warnings: Clang contains a number of new warnings, including
control-flow warnings (unreachable code, missing return statements in a
non-<code>void</code> function, etc.), sign-comparison warnings, and improved
format-string warnings.</li>
<li>CIndex API and Python bindings: Clang now includes a C API as part of the
CIndex library. Although we may make some changes to the API in the future, it
is intended to be stable and has been designed for use by external projects. See
the Clang
doxygen <a href="http://clang.llvm.org/doxygen/group__CINDEX.html">CIndex</a>
documentation for more details. The CIndex API also includes a preliminary
set of Python bindings.</li>
<li>ARM Support: Clang now has ABI support for both the Darwin and Linux ARM
ABIs. Coupled with many improvements to the LLVM ARM backend, Clang is now
suitable for use as a beta quality ARM compiler.</li>
</ul>
</div>
......@@ -133,13 +168,18 @@ development. Here we include updates on these subprojects.
<div class="doc_text">
<p>Previously announced in the 2.4, 2.5, and 2.6 LLVM releases, the Clang project also
includes an early stage static source code analysis tool for <a
href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
in C and Objective-C programs. The tool performs checks to find
bugs that occur on a specific path within a program.</p>
<p>In the LLVM 2.7 time-frame, the analyzer core has ...</p>
<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>In the LLVM 2.7 time-frame, the analyzer core has made several major and
minor improvements, including better support for tracking the fields of
structures, initial support (not enabled by default yet) for doing
interprocedural (cross-function) analysis, and new checks have been added.
</p>
</div>
......@@ -156,13 +196,23 @@ implementation of the CLI) using LLVM for static and just-in-time
compilation.</p>
<p>
VMKit version ?? builds with LLVM 2.7 and you can find it on its
<a href="http://vmkit.llvm.org/releases/">web page</a>. The release includes
bug fixes, cleanup and new features. The major changes are:</p>
With the release of LLVM 2.7, VMKit has shifted to a great framework for writing
virtual machines. VMKit now offers precise and efficient garbage collection with
multi-threading support, thanks to the MMTk memory management toolkit, as well
as just in time and ahead of time compilation with LLVM. The major changes in
VMKit 0.27 are:</p>
<ul>
<li>...</li>
<li>Garbage collection: VMKit now uses the MMTk toolkit for garbage collectors.
The first collector to be ported is the MarkSweep collector, which is precise,
and drastically improves the performance of VMKit.</li>
<li>Line number information in the JVM: by using the debug metadata of LLVM, the
JVM now supports precise line number information, useful when printing a stack
trace.</li>
<li>Interface calls in the JVM: we implemented a variant of the Interface Method
Table technique for interface calls in the JVM.
</li>
</ul>
</div>
......@@ -186,39 +236,41 @@ libgcc routines).</p>
<p>
All of the code in the compiler-rt project is available under the standard LLVM
License, a "BSD-style" license.</p>
License, a "BSD-style" license. New in LLVM 2.7: compiler_rt now
supports ARM targets.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="klee">KLEE: Symbolic Execution and Automatic Test Case Generator</a>
<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a>
</div>
<div class="doc_text">
<p>
The new LLVM <a href="http://klee.llvm.org/">KLEE project</a> is a symbolic
execution framework for programs in LLVM bitcode form. KLEE tries to
symbolically evaluate "all" paths through the application and records state
transitions that lead to fault states. This allows it to construct testcases
that lead to faults and can even be used to verify algorithms. For more
details, please see the <a
href="http://llvm.org/pubs/2008-12-OSDI-KLEE.html">OSDI 2008 paper</a> about
KLEE.</p>
</div>
<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
gcc-4.5. Unlike llvm-gcc, which makes many intrusive changes to the underlying
gcc-4.2 code, dragonegg in theory does not require any gcc-4.5 modifications
whatsoever (currently one small patch is needed). This is thanks to the new
<a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>, which
makes it possible to modify the behaviour of gcc at runtime by loading a plugin,
which is nothing more than a dynamic library which conforms to the gcc plugin
interface. DragonEgg is a gcc plugin that causes the LLVM optimizers to be run
instead of the gcc optimizers, and the LLVM code generators instead of the gcc
code generators, just like llvm-gcc. To use it, you add
"-fplugin=path/dragonegg.so" to the gcc-4.5 command line, and gcc-4.5 magically
becomes llvm-gcc-4.5!
</p>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
</div>
<p>
DragonEgg is still a work in progress. Currently C works very well, while C++,
Ada and Fortran work fairly well. 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 needs an additional gcc patch).
</p>
<div class="doc_text">
<p>
The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (dragonegg.so)
that is loaded by gcc at runtime. It ...
DragonEgg is a new project which is seeing its first release with llvm-2.7.
</p>
</div>
......@@ -231,9 +283,27 @@ that is loaded by gcc at runtime. It ...
<div class="doc_text">
<p>
The LLVM Machine Code (MC) Toolkit project is ...
The LLVM Machine Code (aka MC) sub-project of LLVM 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. It is a sub-project of LLVM which provides it with a number of advantages
over other compilers that do not have tightly integrated assembly-level tools.
For a gentle introduction, 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>
<p>2.7 includes major parts of the work required by the new MC Project. A few
targets have been refactored to support it, and work is underway to support a
native assembler in LLVM. This work is not complete in LLVM 2.7, but it has
made substantially more progress on LLVM mainline.</p>
<p>One minor example of what MC can do is to transcode an AT&amp;T syntax
X86 .s file into intel syntax. You can do this with something like:</p>
<pre>
llvm-mc foo.s -output-asm-variant=1 -o foo-intel.s
</pre>
</div>
......@@ -250,144 +320,163 @@ The LLVM Machine Code (MC) Toolkit project is ...
projects that have already been updated to work with LLVM 2.7.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="Rubinius">Rubinius</a>
<a name="pure">Pure</a>
</div>
<div class="doc_text">
<p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
for running Ruby code which strives to write as much of the core class
implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
uses LLVM to optimize and compile ruby code down to machine code. Techniques
such as type feedback, method inlining, and uncommon traps are all used to
remove dynamism from ruby execution and increase performance.</p>
<p>
<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>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
a counter based JIT, type feedback and speculative method inlining.
</p>
<p>Pure versions 0.43 and later have been tested and are known to work with
LLVM 2.7 (and continue to work with older LLVM releases >= 2.5).</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="macruby">MacRuby</a>
<a name="RoadsendPHP">Roadsend PHP</a>
</div>
<div class="doc_text">
<p>
<a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
core Mac OS X technologies, such as the Objective-C common runtime and garbage
collector and the CoreFoundation framework. It is principally developed by
Apple and aims at enabling the creation of full-fledged Mac OS X applications.
<a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
source implementation of the PHP programming
language that uses LLVM for its optimizer, JIT and static compiler. This is a
reimplementation of an earlier project that is now based on LLVM.
</p>
</div>
<p>
MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
handling.</p>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="UnladenSwallow">Unladen Swallow</a>
</div>
<div class="doc_text">
<p>
<a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
branch of <a href="http://python.org/">Python</a> intended to be fully
compatible and significantly faster. It uses LLVM's optimization passes and JIT
compiler.
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="pure">Pure</a>
<a name="tce">TTA-based Codesign Environment (TCE)</a>
</div>
<div class="doc_text">
<p>
<a href="http://pure-lang.googlecode.com/">Pure</a>
is an algebraic/functional programming language based on term rewriting.
Programs are collections of equations which are used to evaluate expressions in
a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
lexical closures, a hygienic macro system (also based on term rewriting),
built-in list and matrix support (including list and matrix comprehensions) and
an easy-to-use C interface. The interpreter uses LLVM as a backend to
JIT-compile Pure programs to fast native code.</p>
<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>Pure versions ??? and later have been tested and are known to work with
LLVM 2.7 (and continue to work with older LLVM releases >= 2.3 as well).
</p>
</div>
<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>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="ldc">LLVM D Compiler</a>
<a name="safecode">SAFECode Compiler</a>
</div>
<div class="doc_text">
<p>
<a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
the D Programming Language using the LLVM optimizer and code generator.
The LDC project works great with the LLVM 2.6 release. General improvements in
this
cycle have included new inline asm constraint handling, better debug info
support, general bug fixes and better x86-64 support. This has allowed
some major improvements in LDC, getting it much closer to being as
fully featured as the original DMD compiler from DigitalMars.
<a href="http://safecode.cs.illinois.edu">SAFECode</a> is a memory safe C
compiler built using LLVM. It takes standard, unannotated C code, analyzes the
code to ensure that memory accesses and array indexing operations are safe, and
instruments the code with run-time checks when safety cannot be proven
statically.
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="RoadsendPHP">Roadsend PHP</a>
<a name="icedtea">IcedTea Java Virtual Machine Implementation</a>
</div>
<div class="doc_text">
<p>
<a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
source implementation of the PHP programming
language that uses LLVM for its optimizer, JIT and static compiler. This is a
reimplementation of an earlier project that is now based on LLVM.</p>
<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>Icedtea6 1.8 and later have been tested and are known to work with
LLVM 2.7 (and continue to work with older LLVM releases >= 2.6 as well).
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="UnladenSwallow">Unladen Swallow</a>
<a name="llvm-lua">LLVM-Lua</a>
</div>
<div class="doc_text">
<p>
<a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
branch of <a href="http://python.org/">Python</a> intended to be fully
compatible and significantly faster. It uses LLVM's optimization passes and JIT
compiler.</p>
<a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM
to add JIT and static compiling support to the Lua VM. Lua
bytecode is analyzed to remove type checks, then LLVM is used to compile the
bytecode down to machine code.
</p>
<p>LLVM-Lua 1.2.0 have been tested and is known to work with LLVM 2.7.
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="llvm-lua">llvm-lua</a>
<a name="MacRuby">MacRuby</a>
</div>
<div class="doc_text">
<p>
<a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
and static compiling support to the Lua VM. Lua bytecode is analyzed to
remove type checks, then LLVM is used to compile the bytecode down to machine
code.</p>
<a href="http://macruby.org">MacRuby</a> is an implementation of Ruby based on
core Mac OS technologies, sponsored by Apple Inc. It uses LLVM at runtime for
optimization passes, JIT compilation and exception handling. It also allows
static (ahead-of-time) compilation of Ruby code straight to machine code.
</p>
<p>The upcoming MacRuby 0.6 release works with LLVM 2.7.
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="icedtea">IcedTea Java Virtual Machine Implementation</a>
<a name="GHC">Glasgow Haskell Compiler (GHC)</a>
</div>
<div class="doc_text">
<p>
<a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
harness to build OpenJDK using only free software build tools and to provide
replacements for the not-yet free parts of OpenJDK. One of the extensions that
IcedTea provides is a new JIT compiler named <a
href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
to provide native code generation without introducing processor-dependent
code.
</p>
</div>
<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 platforms, together
with an interactive system for convenient, quick development.</p>
<p>In addition to the existing C and native code generators, GHC 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.</p>
</div>
<!-- *********************************************************************** -->
......@@ -405,6 +494,39 @@ in this section.
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="orgchanges">LLVM Community Changes</a>
</div>
<div class="doc_text">
<p>In addition to changes to the code, between LLVM 2.6 and 2.7, a number of
organization changes have happened:
</p>
<ul>
<li>LLVM has a new <a href="http://llvm.org/Logo.html">official logo</a>!</li>
<li>Ted Kremenek and Doug Gregor have stepped forward as <a
href="http://llvm.org/docs/DeveloperPolicy.html#owners">Code Owners</a> of the
Clang static analyzer and the Clang frontend, respectively.</li>
<li>LLVM now has an <a href="http://blog.llvm.org">official Blog</a> at
<a href="http://blog.llvm.org">http://blog.llvm.org</a>. This is a great way
to learn about new LLVM-related features as they are implemented. Several
features in this release are already explained on the blog.</li>
<li>The LLVM web pages are now checked into the SVN server, in the "www",
"www-pubs" and "www-releases" SVN modules. Previously they were hidden in a
largely inaccessible old CVS server.</li>
<li><a href="http://llvm.org">llvm.org</a> is now hosted on a new (and much
faster) server. It is still graciously hosted at the University of Illinois
of Urbana Champaign.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="majorfeatures">Major New Features</a>
......@@ -415,7 +537,40 @@ in this section.
<p>LLVM 2.7 includes several major new capabilities:</p>
<ul>
<li>...</li>
<li>2.7 includes initial support for the <a
href="http://en.wikipedia.org/wiki/MicroBlaze">MicroBlaze</a> target.
MicroBlaze is a soft processor core designed for Xilinx FPGAs.</li>
<li>2.7 includes a new LLVM IR "extensible metadata" feature. This feature
supports many different use cases, including allowing front-end authors to
encode source level information into LLVM IR, which is consumed by later
language-specific passes. This is a great way to do high-level optimizations
like devirtualization, type-based alias analysis, etc. See the <a
href="http://blog.llvm.org/2010/04/extensible-metadata-in-llvm-ir.html">
Extensible Metadata Blog Post</a> for more information.</li>
<li>2.7 encodes <a href="SourceLevelDebugging.html">debug information</a>
in a completely new way, built on extensible metadata. The new implementation
is much more memory efficient and paves the way for improvements to optimized
code debugging experience.</li>
<li>2.7 now directly supports taking the address of a label and doing an
indirect branch through a pointer. This is particularly useful for
interpreter loops, and is used to implement the GCC "address of label"
extension. For more information, see the <a
href="http://blog.llvm.org/2010/01/address-of-label-and-indirect-branches.html">
Address of Label and Indirect Branches in LLVM IR Blog Post</a>.
<li>2.7 is the first release to start supporting APIs for assembling and
disassembling target machine code. These APIs are useful for a variety of
low level clients, and are surfaced in the new "enhanced disassembly" API.
For more information see the <a
href="http://blog.llvm.org/2010/01/x86-disassembler.html">The X86
Disassembler Blog Post</a> for more information.</li>
<li>2.7 includes major parts of the work required by the new MC Project,
see the <a href="#mc">MC update above</a> for more information.</li>
</ul>
</div>
......@@ -430,7 +585,30 @@ in this section.
expose new optimization opportunities:</p>
<ul>
<li>...</li>
<li>LLVM IR now supports a 16-bit "half float" data type through <a
href="LangRef.html#int_fp16">two new intrinsics</a> and APFloat support.</li>
<li>LLVM IR supports two new <a href="LangRef.html#fnattrs">function
attributes</a>: inlinehint and alignstack(n). The former is a hint to the
optimizer that a function was declared 'inline' and thus the inliner should
weight it higher when considering inlining it. The later
indicates to the code generator that the function diverges from the platform
ABI on stack alignment.</li>
<li>The new <a href="LangRef.html#int_objectsize">llvm.objectsize</a> intrinsic
allows the optimizer to infer the sizes of memory objects in some cases.
This intrinsic is used to implement the GCC <tt>__builtin_object_size</tt>
extension.</li>
<li>LLVM IR now supports marking load and store instructions with <a
href="LangRef.html#i_load">"non-temporal" hints</a> (building on the new
metadata feature). This hint encourages the code
generator to generate non-temporal accesses when possible, which are useful
for code that is carefully managing cache behavior. Currently, only the
X86 backend provides target support for this feature.</li>
<li>LLVM 2.7 has pre-alpha support for <a
href="LangRef.html#t_union">unions in LLVM IR</a>.
Unfortunately, this support is not really usable in 2.7, so if you're
interested in pushing it forward, please help contribute to LLVM mainline.</li>
</ul>
</div>
......@@ -447,12 +625,51 @@ release includes a few major enhancements and additions to the optimizers:</p>
<ul>
<li>...</li>
<li>The inliner reuses now merges arrays stack objects in different callees when
inlining multiple call sites into one function. This reduces the stack size
of the resultant function.</li>
<li>The -basicaa alias analysis pass (which is the default) has been improved to
be less dependent on "type safe" pointers. It can now look through bitcasts
and other constructs more aggressively, allowing better load/store
optimization.</li>
<li>The load elimination optimization in the GVN Pass [<a
href="http://blog.llvm.org/2009/12/introduction-to-load-elimination-in-gvn.html">intro
blog post</a>] has been substantially improved to be more aggressive about
partial redundancy elimination and do more aggressive phi translation. Please
see the <a
href="http://blog.llvm.org/2009/12/advanced-topics-in-redundant-load.html">
Advanced Topics in Redundant Load Elimination with a Focus on PHI Translation
Blog Post</a> for more details.</li>
<li>The module <a href="LangRef.html#datalayout">target data string</a> now
includes a notion of 'native' integer data types for the target. This
helps mid-level optimizations avoid promoting complex sequences of
operations to data types that are not natively supported (e.g. converting
i32 operations to i64 on 32-bit chips).</li>
<li>The mid-level optimizer is now conservative when operating on a module with
no target data. Previously, it would default to SparcV9 settings, which is
not what most people expected.</li>
<li>Jump threading is now much more aggressive at simplifying correlated
conditionals and threading blocks with otherwise complex logic. It has
subsumed the old "Conditional Propagation" pass, and -condprop has been
removed from LLVM 2.7.</li>
<li>The -instcombine pass has been refactored from being one huge file to being
a library of its own. Internally, it uses a customized IRBuilder to clean
it up and simplify it.</li>
<li>The optimal edge profiling pass is reliable and much more complete than in
2.6. It can be used with the llvm-prof tool but isn't wired up to the
llvm-gcc and clang command line options yet.</li>
<li>A new experimental alias analysis implementation, -scev-aa, has been added.
It uses LLVM's Scalar Evolution implementation to do symbolic analysis of
pointer offset expressions to disambiguate pointers. It can catch a few
cases that basicaa cannot, particularly in complex loop nests.</li>
<li>The default pass ordering has been tweaked for improved optimization
effectiveness.</li>
</ul>
<p>Also, -anders-aa was removed</p>
</div>
......@@ -464,15 +681,20 @@ release includes a few major enhancements and additions to the optimizers:</p>
<div class="doc_text">
<ul>
<li>The JIT now <a
href="http://llvm.org/viewvc/llvm-project?view=rev&revision=85295">defaults
<li>The JIT now supports generating debug information and is compatible with
the new GDB 7.0 (and later) interfaces for registering dynamically generated
debug info.</li>
<li>The JIT now <a href="http://llvm.org/PR5184">defaults
to compiling eagerly</a> to avoid a race condition in the lazy JIT.
Clients that still want the lazy JIT can switch it on by calling
<tt>ExecutionEngine::DisableLazyCompilation(false)</tt>.</li>
<li>It is now possible to create more than one JIT instance in the same process.
These JITs can generate machine code in parallel,
although <a href="http://llvm.org/docs/ProgrammersManual.html#jitthreading">you
still have to obey the other threading restrictions</a>.</li>
</ul>
</div>
......@@ -489,8 +711,49 @@ infrastructure, which allows us to implement more aggressive algorithms and make
it run faster:</p>
<ul>
<li>...</li>
<li>The 'llc -asm-verbose' option (which is now the default) has been enhanced
to emit many useful comments to .s files indicating information about spill
slots and loop nest structure. This should make it much easier to read and
understand assembly files. This is wired up in llvm-gcc and clang to
the <tt>-fverbose-asm</tt> option.</li>
<li>New LSR with "full strength reduction" mode, which can reduce address
register pressure in loops where address generation is important.</li>
<li>A new codegen level Common Subexpression Elimination pass (MachineCSE)
is available and enabled by default. It catches redundancies exposed by
lowering.</li>
<li>A new pre-register-allocation tail duplication pass is available and enabled
by default, it can substantially improve branch prediction quality in some
cases.</li>
<li>A new sign and zero extension optimization pass (OptimizeExtsPass)
is available and enabled by default. This pass can takes advantage
architecture features like x86-64 implicit zero extension behavior and
sub-registers.</li>
<li>The code generator now supports a mode where it attempts to preserve the
order of instructions in the input code. This is important for source that
is hand scheduled and extremely sensitive to scheduling. It is compatible
with the GCC <tt>-fno-schedule-insns</tt> option.</li>
<li>The target-independent code generator now supports generating code with
arbitrary numbers of result values. Returning more values than was
previously supported is handled by returning through a hidden pointer. In
2.7, only the X86 and XCore targets have adopted support for this
though.</li>
<li>The code generator now supports generating code that follows the
<a href="LangRef.html#callingconv">Glasgow Haskell Compiler Calling
Convention</a> and ABI.</li>
<li>The "<a href="CodeGenerator.html#selectiondag_select">DAG instruction
selection</a>" phase of the code generator has been largely rewritten for
2.7. Previously, tblgen spit out tons of C++ code which was compiled and
linked into the target to do the pattern matching, now it emits a much
smaller table which is read by the target-independent code. The primary
advantages of this approach is that the size and compile time of various
targets is much improved. The X86 code generator shrunk by 1.5MB of code,
for example.</li>
<li>Almost the entire code generator has switched to emitting code through the
MC interfaces instead of printing textually to the .s file. This led to a
number of cleanups and speedups. In 2.7, debug an exception handling
information does not go through MC yet.</li>
</ul>
</div>
......@@ -504,35 +767,16 @@ it run faster:</p>
</p>
<ul>
<li>...</li>
<li>The X86 backend now optimizes tails calls much more aggressively for
functions that use the standard C calling convention.</li>
<li>The X86 backend now models scalar SSE registers as subregs of the SSE vector
registers, making the code generator more aggressive in cases where scalars
and vector types are mixed.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="pic16">PIC16 Target Improvements</a>
</div>
<div class="doc_text">
<p>New features of the PIC16 target include:
</p>
<ul>
<li>...</li>
</ul>
<p>Things not yet supported:</p>
<ul>
<li>Variable arguments.</li>
<li>Interrupts/programs.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="ARM">ARM Target Improvements</a>
......@@ -544,25 +788,31 @@ it run faster:</p>
<ul>
<li>...</li>
</ul>
<li>The ARM backend now generates instructions in unified assembly syntax.</li>
<li>llvm-gcc now has complete support for the ARM v7 NEON instruction set. This
support differs slightly from the GCC implementation. Please see the
<a
href="http://blog.llvm.org/2010/04/arm-advanced-simd-neon-intrinsics-and.html">
ARM Advanced SIMD (NEON) Intrinsics and Types in LLVM Blog Post</a> for
helpful information if migrating code from GCC to LLVM-GCC.</li>
<li>The ARM and Thumb code generators now use register scavenging for stack
object address materialization. This allows the use of R3 as a general
purpose register in Thumb1 code, as it was previous reserved for use in
stack address materialization. Secondly, sequential uses of the same
value will now re-use the materialized constant.</li>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="OtherTarget">Other Target Specific Improvements</a>
</div>
<li>The ARM backend now has good support for ARMv4 targets and has been tested
on StrongARM hardware. Previously, LLVM only supported ARMv4T and
newer chips.</li>
<div class="doc_text">
<p>New features of other targets include:
</p>
<li>Atomic builtins are now supported for ARMv6 and ARMv7 (__sync_synchronize,
__sync_fetch_and_add, etc.).</li>
<ul>
<li>...</li>
</ul>
</div>
<!--=========================================================================-->
......@@ -577,7 +827,34 @@ it run faster:</p>
</p>
<ul>
<li>...</li>
<li>The optimizer uses the new CodeMetrics class to measure the size of code.
Various passes (like the inliner, loop unswitcher, etc) all use this to make
more accurate estimates of the code size impact of various
optimizations.</li>
<li>A new <a href="http://llvm.org/doxygen/InstructionSimplify_8h-source.html">
llvm/Analysis/InstructionSimplify.h</a> interface is available for doing
symbolic simplification of instructions (e.g. <tt>a+0</tt> -&gt; <tt>a</tt>)
without requiring the instruction to exist. This centralizes a lot of
ad-hoc symbolic manipulation code scattered in various passes.</li>
<li>The optimizer now uses a new <a
href="http://llvm.org/doxygen/SSAUpdater_8h-source.html">SSAUpdater</a>
class which efficiently supports
doing unstructured SSA update operations. This centralized a bunch of code
scattered throughout various passes (e.g. jump threading, lcssa,
loop rotate, etc) for doing this sort of thing. The code generator has a
similar <a href="http://llvm.org/doxygen/MachineSSAUpdater_8h-source.html">
MachineSSAUpdater</a> class.</li>
<li>The <a href="http://llvm.org/doxygen/Regex_8h-source.html">
llvm/Support/Regex.h</a> header exposes a platform independent regular
expression API. Building on this, the <a
href="TestingGuide.html#FileCheck">FileCheck</a> utility now supports
regular exressions.</li>
<li>raw_ostream now supports a circular "debug stream" accessed with "dbgs()".
By default, this stream works the same way as "errs()", but if you pass
<tt>-debug-buffer-size=1000</tt> to opt, the debug stream is capped to a
fixed sized circular buffer and the output is printed at the end of the
program's execution. This is helpful if you have a long lived compiler
process and you're interested in seeing snapshots in time.</li>
</ul>
......@@ -592,7 +869,16 @@ it run faster:</p>
<p>Other miscellaneous features include:</p>
<ul>
<li>...</li>
<li>You can now build LLVM as a big dynamic library (e.g. "libllvm2.7.so"). To
get this, configure LLVM with the --enable-shared option.</li>
<li>LLVM command line tools now overwrite their output by default. Previously,
they would only do this with -f. This makes them more convenient to use, and
behave more like standard unix tools.</li>
<li>The opt and llc tools now autodetect whether their input is a .ll or .bc
file, and automatically do the right thing. This means you don't need to
explicitly use the llvm-as tool for most things.</li>
</ul>
</div>
......@@ -610,20 +896,48 @@ on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading
from the previous release.</p>
<ul>
<li>
The Andersen's alias analysis ("anders-aa") pass, the Predicate Simplifier
("predsimplify") pass, the LoopVR pass, the GVNPRE pass, and the random sampling
profiling ("rsprofiling") passes have all been removed. They were not being
actively maintained and had substantial problems. If you are interested in
these components, you are welcome to ressurect them from SVN, fix the
correctness problems, and resubmit them to mainline.</li>
<li>LLVM now defaults to building most libraries with RTTI turned off, providing
a code size reduction. Packagers who are interested in building LLVM to support
plugins that require RTTI information should build with "make REQUIRE_RTTI=1"
and should read the new <a href="Packaging.html">Advice on Packaging LLVM</a>
document.</li>
<li>The LLVM interpreter now defaults to <em>not</em> using <tt>libffi</tt> even
if you have it installed. This makes it more likely that an LLVM built on one
system will work when copied to a similar system. To use <tt>libffi</tt>,
configure with <tt>--enable-libffi</tt>.
</li>
</ul>
configure with <tt>--enable-libffi</tt>.</li>
<li>Debug information uses a completely different representation, an LLVM 2.6
.bc file should work with LLVM 2.7, but debug info won't come forward.</li>
<li>The LLVM 2.6 (and earlier) "malloc" and "free" instructions got removed,
along with LowerAllocations pass. Now you should just use a call to the
malloc and free functions in libc. These calls are optimized as well as
the old instructions were.</li>
</ul>
<p>In addition, many APIs have changed in this release. Some of the major LLVM
API changes are:</p>
<ul>
<li>Just about everything has been converted to use <tt>raw_ostream</tt> instead of
<tt>std::ostream</tt>.</li>
<li><tt>llvm/ADT/iterator.h</tt> has been removed, just use <tt>&lt;iterator&gt;</tt>
instead.</li>
<li>The <tt>Streams.h</tt> file and <tt>DOUT</tt> got removed, use <tt>DEBUG(errs() &lt;&lt; ...);</tt>
instead.</li>
<li>The <tt>TargetAsmInfo</tt> interface was renamed to <tt>MCAsmInfo</tt>.</li>
<li><tt>ModuleProvider</tt> has been <a
href="http://llvm.org/viewvc/llvm-project?view=rev&revision=94686">removed</a>
href="http://llvm.org/viewvc/llvm-project?view=rev&amp;revision=94686">removed</a>
and its methods moved to <tt>Module</tt> and <tt>GlobalValue</tt>.
Most clients can remove uses of <tt>ExistingModuleProvider</tt>,
replace <tt>getBitcodeModuleProvider</tt> with
......@@ -641,15 +955,24 @@ Clients must replace calls to
<tt>GlobalValue::hasNotBeenReadFromBitcode</tt> with
<tt>GlobalValue::isMaterializable</tt>.</li>
<li>FIXME: Debug info has been totally redone. Add pointers to new APIs. Substantial caveats about compatibility of .ll and .bc files.</li>
<li>The <tt>llvm/Support/DataTypes.h</tt> header has moved
to <tt>llvm/System/DataTypes.h</tt>.</li>
<li>The <tt>isInteger</tt>, <tt>isIntOrIntVector</tt>, <tt>isFloatingPoint</tt>,
<tt>isFPOrFPVector</tt> and <tt>isFPOrFPVector</tt> methods have been renamed
<tt>isIntegerTy</tt>, <tt>isIntOrIntVectorTy</tt>, <tt>isFloatingPointTy</tt>,
<tt>isFPOrFPVectorTy</tt> and <tt>isFPOrFPVectorTy</tt> respectively.</li>
<li><tt>llvm::Instruction::clone()</tt> no longer takes argument.</li>
<li><tt>raw_fd_ostream</tt>'s constructor now takes a flag argument, not individual
booleans (see <tt>include/llvm/Support/raw_ostream.h</tt> for details).</li>
<li>Some header files have been renamed:
<ul>
<li><tt>llvm/Support/AIXDataTypesFix.h</tt> to
<tt>llvm/System/AIXDataTypesFix.h</tt></li>
<li><tt>llvm/Support/DataTypes.h</tt> to <tt>llvm/System/DataTypes.h</tt></li>
<li><tt>llvm/Transforms/Utils/InlineCost.h</tt> to
<tt>llvm/Analysis/InlineCost.h</tt></li>
<li><tt>llvm/Support/Mangler.h</tt> to <tt>llvm/Target/Mangler.h</tt></li>
<li><tt>llvm/Analysis/Passes.h</tt> to <tt>llvm/CodeGen/Passes.h</tt></li>
</ul></li>
</ul>
</div>
......@@ -670,7 +993,7 @@ to <tt>llvm/System/DataTypes.h</tt>.</li>
<li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
systems).</li>
<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
<li>PowerPC and X86-based Mac OS X systems, running 10.4 and above in 32-bit
and 64-bit modes.</li>
<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
......@@ -699,13 +1022,7 @@ listed by component. If you run into a problem, please check the <a
href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
there isn't already one.</p>
<ul>
<li>The llvm-gcc bootstrap will fail with some versions of binutils (e.g. 2.15)
with a message of "<tt><a href="http://llvm.org/PR5004">Error: can not do 8
byte pc-relative relocation</a></tt>" when building C++ code. We intend to
fix this on mainline, but a workaround is to upgrade to binutils 2.17 or
later.</li>
<ul>
<li>LLVM will not correctly compile on Solaris and/or OpenSolaris
using the stock GCC 3.x.x series 'out the box',
See: <a href="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
......@@ -731,10 +1048,11 @@ components, please contact us on the <a
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
<ul>
<li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430 and SystemZ backends are
experimental.</li>
<li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
supported value for this option. The ELF writer is experimental.</li>
<li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430, SystemZ and MicroBlaze
backends are experimental.</li>
<li><tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
supported value for this option. The MachO writer is experimental, and
works much better in mainline SVN.</li>
</ul>
</div>
......@@ -755,13 +1073,10 @@ href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
to generate code for systems that don't have SSE2.</li>
<li>Win64 code generation wasn't widely tested. Everything should work, but we
expect small issues to happen. Also, llvm-gcc cannot build the mingw64
runtime currently due
to <a href="http://llvm.org/PR2255">several</a>
<a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
the
'u' inline assembly constraint and for X87 floating point inline assembly.</li>
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, the llvm-gcc and front-ends support variadic
<tt>va_arg</tt>. Currently, front-ends support variadic
argument constructs on X86-64 by lowering them manually.</li>
</ul>
......@@ -789,9 +1104,6 @@ compilation, and lacks support for debug information.</li>
<div class="doc_text">
<ul>
<li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
and not well tested. Some features may not work at all, and the code quality
may be poor in some cases.</li>
<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
processors, thumb programs can crash or produce wrong
results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
......@@ -865,7 +1177,7 @@ appropriate nops inserted to ensure restartability.</li>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="c-fe">Known problems with the llvm-gcc C front-end</a>
<a name="c-fe">Known problems with the llvm-gcc C and C++ front-end</a>
</div>
<div class="doc_text">
......@@ -876,27 +1188,6 @@ appropriate nops inserted to ensure restartability.</li>
supported on some targets (these are used when you take the address of a
nested function).</p>
<p>If you run into GCC extensions which are not supported, please let us know.
</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
</div>
<div class="doc_text">
<p>The C++ front-end is considered to be fully
tested and works for a number of non-trivial programs, including LLVM
itself, Qt, Mozilla, etc.</p>
<ul>
<li>Exception handling works well on the X86 and PowerPC targets. Currently
only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
</ul>
</div>
<!-- ======================================================================= -->
......@@ -951,20 +1242,6 @@ ignored</a>.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="ocaml-bindings">Known problems with the O'Caml bindings</a>
</div>
<div class="doc_text">
<p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
<tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
<tt>Llvm.Linkage.Link_once</tt> will be correct. If you need any of the other linkage
modes, you'll have to write an external C library in order to expose the
functionality. This has been fixed in the trunk.</p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="additionalinfo">Additional Information</a>
......
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