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@ -4,11 +4,11 @@
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="_static/llvm.css" type="text/css">
<title>LLVM 3.1 Release Notes</title>
<title>LLVM 3.2 Release Notes</title>
</head>
<body>
<h1>LLVM 3.1 Release Notes</h1>
<h1>LLVM 3.2 Release Notes</h1>
<div>
<img style="float:right" src="http://llvm.org/img/DragonSmall.png"
@ -18,7 +18,7 @@
<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 3.1</a></li>
<li><a href="#externalproj">External Projects Using LLVM 3.2</a></li>
<li><a href="#whatsnew">What's New in LLVM?</a></li>
<li><a href="GettingStarted.html">Installation Instructions</a></li>
<li><a href="#knownproblems">Known Problems</a></li>
@ -29,10 +29,10 @@
<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 3.1
<h1 style="color:red">These are in-progress notes for the upcoming LLVM 3.2
release.<br>
You may prefer the
<a href="http://llvm.org/releases/3.0/docs/ReleaseNotes.html">LLVM 3.0
<a href="http://llvm.org/releases/3.1/docs/ReleaseNotes.html">LLVM 3.1
Release Notes</a>.</h1>
<!-- *********************************************************************** -->
@ -44,11 +44,11 @@ Release Notes</a>.</h1>
<div>
<p>This document contains the release notes for the LLVM Compiler
Infrastructure, release 3.1. Here we describe the status of LLVM, including
Infrastructure, release 3.2. Here we describe the status of LLVM, including
major improvements from the previous release, improvements in various
subprojects of LLVM, and some of the current users of the code.
All LLVM releases may be downloaded from
the <a href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
subprojects of LLVM, and some of the current users of the code. All LLVM
releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
releases web site</a>.</p>
<p>For more information about LLVM, including information about the latest
release, please check out the <a href="http://llvm.org/">main LLVM web
@ -72,9 +72,9 @@ Release Notes</a>.</h1>
<div>
<p>The LLVM 3.1 distribution currently consists of code from the core LLVM
repository (which roughly includes the LLVM optimizers, code generators and
supporting tools), and the Clang repository. In addition to this code, the
<p>The LLVM 3.2 distribution currently consists of code from the core LLVM
repository, which roughly includes the LLVM optimizers, code generators and
supporting tools, and the Clang repository. In addition to this code, the
LLVM Project includes other sub-projects that are in development. Here we
include updates on these subprojects.</p>
@ -94,20 +94,13 @@ Release Notes</a>.</h1>
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 3.1 time-frame, the Clang team has made many improvements.
<p>In the LLVM 3.2 time-frame, the Clang team has made many improvements.
Highlights include:</p>
<ul>
<li>Greatly expanded <a href="http://clang.llvm.org/cxx_status.html">C++11
support</a> including lambdas, initializer lists, constexpr, user-defined
literals, and atomics.</li>
<li>A new <a href="http://clang.llvm.org/docs/Tooling.html">tooling</a>
library to ease building of clang-based standalone tools.</li>
<li>Extended support for
<a href="http://clang.llvm.org/docs/ObjectiveCLiterals.html">literals in
Objective C</a>.</li>
<li>...</li>
</ul>
<p>For more details about the changes to Clang since the 3.0 release, see the
<p>For more details about the changes to Clang since the 3.1 release, see the
<a href="http://clang.llvm.org/docs/ReleaseNotes.html">Clang release
notes.</a></p>
@ -133,23 +126,10 @@ Release Notes</a>.</h1>
Linux and OpenBSD platforms. It fully supports Ada, C, C++ and Fortran. It
has partial support for Go, Java, Obj-C and Obj-C++.</p>
<p>The 3.1 release has the following notable changes:</p>
<p>The 3.2 release has the following notable changes:</p>
<ul>
<li>Partial support for gcc-4.7. Ada support is poor, but other languages work
fairly well.</li>
<li>Support for ARM processors. Some essential gcc headers that are needed to
build DragonEgg for ARM are not installed by gcc. To work around this,
copy the missing headers from the gcc source tree.</li>
<li>Better optimization for Fortran by exploiting the fact that Fortran scalar
arguments have 'restrict' semantics.</li>
<li>Better optimization for all languages by passing information about type
aliasing and type ranges to the LLVM optimizers.</li>
<li>A regression test-suite was added.</li>
<li>...</li>
</ul>
</div>
@ -166,13 +146,15 @@ Release Notes</a>.</h1>
target-specific hooks required by code generation and other runtime
components. For example, when compiling for a 32-bit target, converting a
double to a 64-bit unsigned integer is compiled into a runtime call to the
"__fixunsdfdi" function. The compiler-rt library provides highly optimized
implementations of this and other low-level routines (some are 3x faster than
the equivalent libgcc routines).</p>
<code>__fixunsdfdi</code> 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>As of 3.1, compiler-rt includes the helper functions for atomic operations,
allowing atomic operations on arbitrary-sized quantities to work. These
functions follow the specification defined by gcc and are used by clang.</p>
<p>The 3.2 release has the following notable changes:</p>
<ul>
<li>...</li>
</ul>
</div>
@ -189,6 +171,12 @@ Release Notes</a>.</h1>
expression parsing (particularly for C++) and uses the LLVM JIT for target
support.</p>
<p>The 3.2 release has the following notable changes:</p>
<ul>
<li>...</li>
</ul>
</div>
<!--=========================================================================-->
@ -202,15 +190,10 @@ Release Notes</a>.</h1>
licensed</a> under the MIT and UIUC license, allowing it to be used more
permissively.</p>
<p>Within the LLVM 3.1 time-frame there were the following highlights:</p>
<p>Within the LLVM 3.2 time-frame there were the following highlights:</p>
<ul>
<li>The <code>&lt;atomic&gt;</code> header is now passing all tests, when
compiling with clang and linking against the support code from
compiler-rt.</li>
<li>FreeBSD now includes libc++ as part of the base system.</li>
<li>libc++ has been ported to Solaris and, in combination with libcxxrt and
clang, is working with a large body of existing code.</li>
<li>...</li>
</ul>
</div>
@ -226,8 +209,11 @@ Release Notes</a>.</h1>
of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
just-in-time compilation.</p>
<p>In the LLVM 3.1 time-frame, VMKit has had significant improvements on both
runtime and startup performance.</p>
<p>The 3.2 release has the following notable changes:</p>
<ul>
<li>...</li>
</ul>
</div>
@ -245,16 +231,10 @@ Release Notes</a>.</h1>
Work in the area of automatic SIMD and accelerator code generation was
started.</p>
<p>Within the LLVM 3.1 time-frame there were the following highlights:</p>
<p>Within the LLVM 3.2 time-frame there were the following highlights:</p>
<ul>
<li>Polly became an official LLVM project</li>
<li>Polly can be loaded directly into clang (enabled by '-O3 -mllvm -polly')</li>
<li>An automatic scheduling optimizer (derived
from <a href="http://pluto-compiler.sourceforge.net/">Pluto</a>) was
integrated. It performs loop transformations to optimize for data-locality
and parallelism. The transformations include, but are not limited to
interchange, fusion, fission, skewing and tiling.</li>
<li>...</li>
</ul>
</div>
@ -263,7 +243,7 @@ Release Notes</a>.</h1>
<!-- *********************************************************************** -->
<h2>
<a name="externalproj">External Open Source Projects Using LLVM 3.1</a>
<a name="externalproj">External Open Source Projects Using LLVM 3.2</a>
</h2>
<!-- *********************************************************************** -->
@ -271,7 +251,7 @@ Release Notes</a>.</h1>
<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 3.1.</p>
projects that have already been updated to work with LLVM 3.2.</p>
<h3>Crack</h3>
@ -415,7 +395,7 @@ Release Notes</a>.</h1>
<!-- *********************************************************************** -->
<h2>
<a name="whatsnew">What's New in LLVM 3.1?</a>
<a name="whatsnew">What's New in LLVM 3.2?</a>
</h2>
<!-- *********************************************************************** -->
@ -432,13 +412,13 @@ Release Notes</a>.</h1>
<div>
<!-- Features that need text if they're finished for 3.1:
<!-- Features that need text if they're finished for 3.2:
ARM EHABI
combiner-aa?
strong phi elim
loop dependence analysis
CorrelatedValuePropagation
lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.2.
Integrated assembler on by default for arm/thumb?
-->
@ -449,17 +429,10 @@ Release Notes</a>.</h1>
llvm/lib/Archive - replace with lib object?
-->
<p>LLVM 3.1 includes several major changes and big features:</p>
<p>LLVM 3.2 includes several major changes and big features:</p>
<ul>
<li><a href="../tools/clang/docs/AddressSanitizer.html">AddressSanitizer</a>,
a fast memory error detector.</li>
<li><a href="CodeGenerator.html#machineinstrbundle">MachineInstr Bundles</a>,
Support to model instruction bundling / packing.</li>
<li><a href="#armintegratedassembler">ARM Integrated Assembler</a>,
A full featured assembler and direct-to-object support for ARM.</li>
<li><a href="#blockplacement">Basic Block Placement</a>
Probability driven basic block placement.</li>
<li>...</li>
</ul>
</div>
@ -476,19 +449,7 @@ Release Notes</a>.</h1>
expose new optimization opportunities:</p>
<ul>
<li>A new type representing 16 bit <i>half</i> floating point values has
been added.</li>
<li>IR now supports vectors of pointers, including vector GEPs.</li>
<li>Module flags have been introduced. They convey information about the
module as a whole to LLVM subsystems. This is currently used to encode
Objective C ABI information.</li>
<li>Loads can now have range metadata attached to them to describe the
possible values being loaded.</li>
<li>The <tt>llvm.ctlz</tt> and <tt>llvm.cttz</tt> intrinsics now have an
additional argument which indicates whether the behavior of the intrinsic
is undefined on a zero input. This can be used to generate more efficient
code on platforms that only have instructions which don't return the type
size when counting bits in 0.</li>
<li>...</li>
</ul>
</div>
@ -500,22 +461,11 @@ Release Notes</a>.</h1>
<div>
<p>In addition to many minor performance tweaks and bug fixes, this
release includes a few major enhancements and additions to the
optimizers:</p>
<p>In addition to many minor performance tweaks and bug fixes, this release
includes a few major enhancements and additions to the optimizers:</p>
<ul>
<li>The loop unroll pass now is able to unroll loops with run-time trip counts.
This feature is turned off by default, and is enabled with the
<code>-unroll-runtime</code> flag.</li>
<li>A new basic-block autovectorization pass is available. Pass
<code>-vectorize</code> to run this pass along with some associated
post-vectorization cleanup passes. For more information, see the EuroLLVM
2012 slides: <a href="http://llvm.org/devmtg/2012-04-12/Slides/Hal_Finkel.pdf">
Autovectorization with LLVM</a>.</li>
<li>Inline cost heuristics have been completely overhauled and now closely
model constant propagation through call sites, disregard trivially dead
code costs, and can model C++ STL iterator patterns.</li>
<li>...</li>
</ul>
</div>
@ -530,14 +480,12 @@ Release Notes</a>.</h1>
<p>The LLVM Machine Code (aka MC) subsystem was created to solve a number of
problems in the realm of assembly, disassembly, object file format handling,
and a number of other related areas that CPU instruction-set level tools work
in. For more information, please see
the <a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
in. For more information, please see the
<a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
to the LLVM MC Project Blog Post</a>.</p>
<ul>
<li>The integrated assembler can optionally emit debug information when
assembling a </tt>.s</tt> file. It can be enabled by passing the
<tt>-g</tt> option to <tt>llvm-mc</tt>.</li>
<li>...</li>
</ul>
</div>
@ -562,21 +510,7 @@ Release Notes</a>.</h1>
make it run faster:</p>
<ul>
<li>TableGen can now synthesize register classes that are only needed to
represent combinations of constraints from instructions and sub-registers.
The synthetic register classes inherit most of their properties form their
closest user-defined super-class.</li>
<li><code>MachineRegisterInfo</code> now allows the reserved registers to be
frozen when register allocation starts. Target hooks should use the
<code>MRI-&gt;canReserveReg(FramePtr)</code> method to avoid accidentally
disabling frame pointer elimination during register allocation.</li>
<li>A new kind of <code>MachineOperand</code> provides a compact
representation of large clobber lists on call instructions. The register
mask operand references a bit mask of preserved registers. Everything else
is clobbered.</li>
<li>The DWARF debug info writer gained support for emitting data for the
<a href="SourceLevelDebugging.html#acceltable">name accelerator tables
DWARF extension</a>. It is used by LLDB to speed up name lookup.</li>
<li>...</li>
</ul>
<p> We added new TableGen infrastructure to support bundling for
@ -593,11 +527,14 @@ Release Notes</a>.</h1>
<h4>
<a name="blockplacement">Basic Block Placement</a>
</h4>
<div>
<p>A probability based block placement and code layout algorithm was added to
LLVM's code generator. This layout pass supports probabilities derived from
static heuristics as well as source code annotations such as
<code>__builtin_expect</code>.</p>
LLVM's code generator. This layout pass supports probabilities derived from
static heuristics as well as source code annotations such as
<code>__builtin_expect</code>.</p>
</div>
<!--=========================================================================-->
@ -610,14 +547,7 @@ static heuristics as well as source code annotations such as
<p>New features and major changes in the X86 target include:</p>
<ul>
<li>Greatly improved support for AVX2.</li>
<li>Lots of bug fixes and improvements for AVX1.</li>
<li>Support for the FMA4 and XOP instruction set extensions.</li>
<li>Call instructions use the new register mask operands for faster compile
times and better support for different calling conventions. The old WINCALL
instructions are no longer needed.</li>
<li>DW2 Exception Handling is enabled on Cygwin and MinGW.</li>
<li>Support for implicit TLS model used with MSVC runtime.</li>
<li>...</li>
</ul>
</div>
@ -632,65 +562,45 @@ static heuristics as well as source code annotations such as
<p>New features of the ARM target include:</p>
<ul>
<li>The constant island pass now supports basic block and constant pool entry
alignments greater than 4 bytes.</li>
<li>On Darwin, the ARM target now has a full-featured integrated assembler.
</li>
<li>...</li>
</ul>
<!--_________________________________________________________________________-->
<h4>
<a name="armintegratedassembler">ARM Integrated Assembler</a>
</h4>
<div>
<p>The ARM target now includes a full featured macro assembler, including
direct-to-object module support for clang. The assembler is currently enabled
by default for Darwin only pending testing and any additional necessary
platform specific support for Linux.</p>
direct-to-object module support for clang. The assembler is currently enabled
by default for Darwin only pending testing and any additional necessary
platform specific support for Linux.</p>
<p>Full support is included for Thumb1, Thumb2 and ARM modes, along with
subtarget and CPU specific extensions for VFP2, VFP3 and NEON.</p>
subtarget and CPU specific extensions for VFP2, VFP3 and NEON.</p>
<p>The assembler is Unified Syntax only (see ARM Architecural Reference Manual
for details). While there is some, and growing, support for pre-unfied (divided)
syntax, there are still significant gaps in that support.</p>
for details). While there is some, and growing, support for pre-unfied
(divided) syntax, there are still significant gaps in that support.</p>
</div>
</div>
<!--=========================================================================-->
<h3>
<a name="MIPS">MIPS Target Improvements</a>
</h3>
<div>
New features and major changes in the MIPS target include:</p>
<p>New features and major changes in the MIPS target include:</p>
<ul>
<li>MIPS32 little-endian direct object code emission is functional.</li>
<li>MIPS64 little-endian code generation is largely functional for N64 ABI in assembly printing mode with the exception of handling of long double (f128) type.</li>
<li>Support for new instructions has been added, which includes swap-bytes
instructions (WSBH and DSBH), floating point multiply-add/subtract and
negative multiply-add/subtract instructions, and floating
point load/store instructions with reg+reg addressing (LWXC1, etc.)</li>
<li>Various fixes to improve performance have been implemented.</li>
<li>Post-RA scheduling is now enabled at -O3.</li>
<li>Support for soft-float code generation has been added.</li>
<li>clang driver's support for MIPS 64-bits targets.</li>
<li>Support for MIPS floating point ABI option in clang driver.</li>
<li>...</li>
</ul>
</div>
<!--=========================================================================-->
<h3>
<a name="PTX">PTX Target Improvements</a>
</h3>
<div>
<p>An outstanding conditional inversion bug was fixed in this release.</p>
<p><b>NOTE</b>: LLVM 3.1 marks the last release of the PTX back-end, in its
current form. The back-end is currently being replaced by the NVPTX
back-end, currently in SVN ToT.</p>
</div>
@ -702,7 +612,7 @@ New features and major changes in the MIPS target include:</p>
<div>
<ul>
<li>Support for Qualcomm's Hexagon VLIW processor has been added.</li>
<li>...</li>
</ul>
</div>
@ -715,25 +625,11 @@ New features and major changes in the MIPS target include:</p>
<div>
<p>If you're already an LLVM user or developer with out-of-tree changes based on
LLVM 3.1, this section lists some "gotchas" that you may run into upgrading
LLVM 3.2, this section lists some "gotchas" that you may run into upgrading
from the previous release.</p>
<ul>
<li>LLVM's build system now requires a python 2 interpreter to be present at
build time. A perl interpreter is no longer required.</li>
<li>The C backend has been removed. It had numerous problems, to the point of
not being able to compile any nontrivial program.</li>
<li>The Alpha, Blackfin and SystemZ targets have been removed due to lack of
maintenance.</li>
<li>LLVM 3.1 removes support for reading LLVM 2.9 bitcode files. Going
forward, we aim for all future versions of LLVM to read bitcode files and
<tt>.ll</tt> files produced by LLVM 3.0 and later.</li>
<li>The <tt>unwind</tt> instruction is now gone. With the introduction of the
new exception handling system in LLVM 3.0, the <tt>unwind</tt> instruction
became obsolete.</li>
<li>LLVM 3.0 and earlier automatically added the returns_twice fo functions
like setjmp based on the name. This functionality was removed in 3.1.
This affects Clang users, if -ffreestanding is used.</li>
<li>...</li>
</ul>
</div>
@ -749,40 +645,7 @@ New features and major changes in the MIPS target include:</p>
LLVM API changes are:</p>
<ul>
<li>Target specific options have been moved from global variables to members
on the new <code>TargetOptions</code> class, which is local to each
<code>TargetMachine</code>. As a consequence, the associated flags will
no longer be accepted by <tt>clang -mllvm</tt>. This includes:
<ul>
<li><code>llvm::PrintMachineCode</code></li>
<li><code>llvm::NoFramePointerElim</code></li>
<li><code>llvm::NoFramePointerElimNonLeaf</code></li>
<li><code>llvm::DisableFramePointerElim(const MachineFunction &)</code></li>
<li><code>llvm::LessPreciseFPMADOption</code></li>
<li><code>llvm::LessPrecideFPMAD()</code></li>
<li><code>llvm::NoExcessFPPrecision</code></li>
<li><code>llvm::UnsafeFPMath</code></li>
<li><code>llvm::NoInfsFPMath</code></li>
<li><code>llvm::NoNaNsFPMath</code></li>
<li><code>llvm::HonorSignDependentRoundingFPMathOption</code></li>
<li><code>llvm::HonorSignDependentRoundingFPMath()</code></li>
<li><code>llvm::UseSoftFloat</code></li>
<li><code>llvm::FloatABIType</code></li>
<li><code>llvm::NoZerosInBSS</code></li>
<li><code>llvm::JITExceptionHandling</code></li>
<li><code>llvm::JITEmitDebugInfo</code></li>
<li><code>llvm::JITEmitDebugInfoToDisk</code></li>
<li><code>llvm::GuaranteedTailCallOpt</code></li>
<li><code>llvm::StackAlignmentOverride</code></li>
<li><code>llvm::RealignStack</code></li>
<li><code>llvm::DisableJumpTables</code></li>
<li><code>llvm::EnableFastISel</code></li>
<li><code>llvm::getTrapFunctionName()</code></li>
<li><code>llvm::EnableSegmentedStacks</code></li>
</ul></li>
<li>The <code>MDBuilder</code> class has been added to simplify the creation
of metadata.</li>
<li>...</li>
</ul>
</div>
@ -797,13 +660,8 @@ New features and major changes in the MIPS target include:</p>
<p>In addition, some tools have changed in this release. Some of the changes
are:</p>
<ul>
<li><tt>llvm-stress</tt> is a command line tool for generating random
<tt>.ll</tt> files to fuzz different LLVM components. </li>
<li>The <tt>llvm-ld</tt> tool has been removed. The clang driver provides a
more reliable solution for turning a set of bitcode files into a binary.
To merge bitcode files <tt>llvm-link</tt> can be used instead.</li>
<li>...</li>
</ul>
</div>
@ -817,19 +675,12 @@ New features and major changes in the MIPS target include:</p>
<div>
<p>Officially supported Python bindings have been added! Feature support is far
from complete. The current bindings support interfaces to:</p>
from complete. The current bindings support interfaces to:</p>
<ul>
<li>Object File Interface</li>
<li>Disassembler</li>
<li>...</li>
</ul>
<p>Using the Object File Interface, it is possible to inspect binary object files.
Think of it as a Python version of readelf or llvm-objdump.</p>
<p>Support for additional features is currently being developed by community
contributors. If you are interested in shaping the direction of the Python
bindings, please express your intent on IRC or the developers list.</p>
</div>
</div>
@ -845,10 +696,10 @@ bindings, please express your intent on IRC or the developers list.</p>
<p>LLVM is generally a production quality compiler, and is used by a broad range
of applications and shipping in many products. That said, not every
subsystem is as mature as the aggregate, particularly the more obscure
targets. If you run into a problem, please check the <a
href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
there isn't already one or ask on the <a
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
targets. If you run into a problem, please check
the <a href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
there isn't already one or ask on
the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
list</a>.</p>
<p>Known problem areas include:</p>