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@ -4,11 +4,11 @@
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
<title>LLVM 2.1 Release Notes</title>
<title>LLVM 2.2 Release Notes</title>
</head>
<body>
<div class="doc_title">LLVM 2.1 Release Notes</div>
<div class="doc_title">LLVM 2.2 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
@ -23,6 +23,7 @@
<p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="intro">Introduction</a>
@ -32,7 +33,7 @@
<div class="doc_text">
<p>This document contains the release notes for the LLVM compiler
infrastructure, release 2.1. Here we describe the status of LLVM, including
infrastructure, release 2.2. Here we describe the status of LLVM, including
major improvements from the previous release and any known problems. All LLVM
releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
releases web site</a>.</p>
@ -58,31 +59,197 @@ current one. To see the release notes for a specific releases, please see the
<div class="doc_text">
<p>This is the twelfth public release of the LLVM Compiler Infrastructure.
It includes many features and refinements from LLVM 2.0.</p>
<p>This is the thirteenth public release of the LLVM Compiler Infrastructure.
It includes many features and refinements from LLVM 2.1.</p>
</div>
<!-- Unfinished features in 2.2:
Index Set Splitting not enabled by default
Machine LICM
Machine Sinking
LegalizeDAGTypes
-->
<!--=========================================================================-->
<div class="doc_subsection">
<a name="deprecation">Deprecated features in LLVM 2.2</a>
</div>
<div class="doc_text">
<p>This is the last LLVM release to support llvm-gcc 4.0, llvm-upgrade, and
llvmc in its current form. llvm-gcc 4.0 has been replaced with llvm-gcc 4.2.
llvm-upgrade is useful for upgrading llvm 1.9 files to llvm 2.x syntax, but you
can always use an old release to do this. llvmc is currently mostly useless in
llvm 2.2, and will be redesigned or removed in llvm 2.3.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="frontends">New Frontends</a>
<a name="frontends">llvm-gcc 4.0, llvm-gcc 4.2, and clang</a>
</div>
<div class="doc_text">
<p>LLVM 2.1 brings two new beta C front-ends. First, a new version of llvm-gcc
based on GCC 4.2, innovatively called "llvm-gcc-4.2". This promises to bring
FORTRAN and Ada support to LLVM as well as features like atomic builtins and
OpenMP. None of these actually work yet, but don't let that stop you checking
it out!</p>
<p>LLVM 2.2 fully supports both the llvm-gcc 4.0 and llvm-gcc 4.2 front-ends (in
LLVM 2.1, llvm-gcc 4.2 was beta). Since LLVM 2.1, the llvm-gcc 4.2 front-end
has made leaps and bounds and is now at least as good as 4.0 in virtually every
area, and is better in several areas (for example, exception handling
correctness, support for Ada and Fortran, better ABI compatibility, etc). We
strongly recommend that you
migrate from llvm-gcc 4.0 to llvm-gcc 4.2 in this release cycle because
<b>LLVM 2.2 is the last release that will support llvm-gcc 4.0</b>: LLVM 2.3
will only support the llvm-gcc 4.2 front-end.</p>
<p>Second, LLVM now includes its own native C and Objective-C front-end (C++ is
in progress, but is not very far along) code named "<a
href="http://clang.llvm.org/">clang</a>". This front-end has a number of great
features, primarily aimed at source-level analysis and speeding up compile-time.
At this point though, the LLVM Code Generator component is still very early in
development, so it's mostly useful for people looking to build source-level
analysis tools or source-to-source translators.</p>
<p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
a set of new 'llvm native' front-end technologies for the LLVM optimizer
and code generator. Currently, its C and Objective-C support is maturing
nicely, and it has advanced source-to-source analysis and transformation
capabilities. If you are interested in building source-level tools for C and
Objective-C (and eventually C++), you should take a look. However, note that
clang is not an official part of the LLVM 2.2 release. If you are interested in
this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="majorfeatures">Major New Features</a>
</div>
<div class="doc_text">
<p>LLVM 2.2 includes several major new capabilities:</p>
<ul>
<li>A research team led by Scott Michel in the Computer Systems Research
Department at The Aerospace Corporation contributed the CellSPU backend, which
generates code for the vector coprocessors on the Sony/Toshiba/IBM Cell BE
processor. llvm-gcc 4.2 supports CellSPU as a 'configure' target and progress
is being made so that libgcc.a compiles cleanly. Notable pieces still in
development include full 64-bit integer and full double precision floating
point support.</li>
<li>Anton and Duncan significantly improved llvm-gcc 4.2 support for the GCC Ada
(GNAT) and Fortran (gfortran) front-ends. These front-ends should still be considered
experimental however: see the <a href="#knownproblems">list of known problems</a>.
The release binaries do not contain either front-end: they need to be built from
source (the Ada front-end only builds on x86-32 linux).</li>
<li>Dale contributed full support for long double on x86/x86-64 (where it is 80
bits) and on Darwin PPC/PPC64 (where it is 128 bits). In previous LLVM
releases, llvm-gcc silently mapped long double to double.</li>
<li>Gordon Henriksen rewrote most of the <a href="GarbageCollection.html"
>Accurate Garbage Collection</a> code in the code generator, making the
generated code more efficient and adding support for the OCaml garbage collector
metadata format.</li>
<li>Christopher Lamb contributed support for multiple address spaces in LLVM
IR. This is useful for supporting targets that have 'near' vs 'far' pointers,
'RAM' vs 'ROM' pointers, or that have non-local memory that can be accessed with
special instructions.</li>
<li>LLVM now includes a new set of detailed <a
href="tutorial/index.html">tutorials</a>, which explain how to implement a
language with LLVM and shows how to use several important APIs.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="coreimprovements">LLVM Core Improvements</a>
</div>
<div class="doc_text">
<p>New features include:
</p>
<ul>
<li>Gordon contributed support for C and OCaml Bindings for the basic LLVM IR
construction routines as well as several other auxiliary APIs.</li>
<li>Anton added readnone/readonly attributes for modeling function side effects.
Duncan hooked up GCC's pure/const attributes to them and enhanced mod/ref
analysis to use them.</li>
<li>Devang added LLVMFoldingBuilder, a version of LLVMBuilder that implicitly
simplifies the code as it is constructed.</li>
<li>Ted Kremenek added a framework for generic object serialization to bitcode
files. This support is only used by clang right now for ASTs but is extensible
and could be used for serializing arbitrary other data into bitcode files.</li>
<li>Duncan improved TargetData to distinguish between the size/alignment of a
type in a register, in memory according to the platform ABI, and in memory when
we have a choice.</li>
<li>Reid moved parameter attributes off of FunctionType and onto functions
and calls. This makes it much easier to add attributes to a function in a
transformation pass.</li>
<li>Dan Gohman added support for vector sin, cos, and pow intrinsics.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="codegen">Code Generator Improvements</a>
</div>
<div class="doc_text">
<p>We put a significant amount of work into the code generator infrastructure,
which allows us to implement more aggressive algorithms and make it run
faster:</p>
<ul>
<li>Owen refactored the existing LLVM dominator and loop information code to
allow it work on the machine code representation. He contributed support for
dominator and loop information on machine code and merged the code for forward
and backward dominator computation.</li>
<li>Dan added support for emitting debug information with .file and .loc
directives on platforms that support it, instead of emitting large tables in the .s
file.</li>
<li>Evan extended the DAG scheduler to model physical register dependencies
explicitly and have the BURR scheduler pick a correct schedule based on the
dependencies. This reduces our use of the 'flag' operand hack.</li>
<li>Evan added initial support for register coalescing of subregister
references.</li>
<li>Rafael Espindola implemented initial support for a new 'byval' attribute,
which allows more efficient by-value argument passing in the LLVM IR. Evan
finished support for it and enabled it in the X86 (32- and 64-bit) and C
backends.</li>
<li>The LLVM TargetInstrInfo class can now answer queries about the mod/ref and
side-effect behavior of MachineInstr's. This information is inferred
automatically by TableGen from .td files for all instructions with
patterns.</li>
<li>Evan implemented simple live interval splitting on basic block boundaries.
This allows the register allocator to be more successful at keeping values in
registers in some parts of a value's live range, even if they need to be spilled
in some other block.</li>
<li>The new MachineRegisterInfo.h class provides support for efficiently
iterating over all defs/uses of a register, and this information is
automatically kept up-to-date. This support is similar to the use_iterator in
the LLVM IR level.</li>
<li>The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler,
more consistent, and better documented.</li>
</ul>
</div>
@ -93,78 +260,24 @@ analysis tools or source-to-source translators.</p>
<div class="doc_text">
<p>Some of the most noticable feature improvements this release have been in the
optimizer, speeding it up and making it more aggressive. For example:</p>
<p>In addition to a huge array of bug fixes and minor performance tweaks, the
LLVM 2.2 optimizers support a few major enhancements:</p>
<ul>
<li>Owen Anderson wrote the new MemoryDependenceAnalysis pass, which provides
a lazy, caching layer on top of <a
href="AliasAnalysis.html">AliasAnalysis</a>. He then used it to rewrite
DeadStoreElimination which resulted in significantly better compile time in
common cases, </li>
<li>Owen implemented the new GVN pass, which is also based on
MemoryDependenceAnalysis. This pass replaces GCSE/LoadVN in the standard
set of passes, providing more aggressive optimization at a some-what
improved compile-time cost.</li>
<li>Owen implemented GVN-PRE, a partial redundancy elimination algorithm that
shares some details with the new GVN pass. It is still in need of compile
time tuning, and is not turned on by default.</li>
<li>Devang merged ETForest and DomTree into a single easier to use data
structure. This makes it more obvious which datastructure to choose
(because there is only one) and makes the compiler more memory and time
efficient (less stuff to keep up-to-date).</li>
<li>Nick Lewycky improved loop trip count analysis to handle many more common
cases.</li>
<li>Daniel Berlin and Curtis Dunham rewrote Andersen's alias analysis to be
several orders of magnitude faster, and implemented Offline Variable
Substitution and Lazy Cycle Detection. Note that Andersen's is not enabled in
llvm-gcc by default, but can be accessed through 'opt'.</li>
</ul>
<li>Dan Gohman contributed several enhancements to Loop Strength Reduction (LSR)
to make it more aggressive with SSE intrinsics and when induction variables are
used by non-memory instructions.</li>
</div>
<li>Evan added support for simple exit value substitution to LSR.</li>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="codegen">Code Generator Improvements</a>
</div>
<div class="doc_text">
<p>One of the main focuses of this release was performance tuning and bug
fixing. In addition to these, several new major changes occurred:</p>
<ul>
<li>Dale finished up the Tail Merging optimization in the code generator, and
enabled it by default. This produces smaller code that is also faster in
some cases.</li>
<li>Christopher Lamb implemented support for virtual register sub-registers,
which can be used to better model many forms of subregisters. As an example
use, he modified the X86 backend to use this to model truncates and
extends more accurately (leading to better code).</li>
<li>Dan Gohman changed the way we represent vectors before legalization,
significantly simplifying the SelectionDAG representation for these and
making the code generator faster for vector code.</li>
<li>Evan contributed a new target independent if-converter. While it is
target independent, so far only the ARM backend uses it.</li>
<li>Evan rewrote the way the register allocator handles rematerialization,
allowing it to be much more effective on two-address targets like X86,
and taught it to fold loads away when possible (also a big win on X86).</li>
<li>Dan Gohman contributed support for better alignment and volatility handling
in the code generator, and significantly enhanced alignment analysis for SSE
load/store instructions. With his changes, an insufficiently-aligned SSE
load instruction turns into <tt>movups</tt>, for example.</li>
<li>Duraid Madina contributed a new "bigblock" register allocator, and Roman
Levenstein contributed several big improvements. BigBlock is optimized for
code that uses very large basic blocks. It is slightly slower than the
"local" allocator, but produces much better code.</li>
<li>David Greene refactored the register allocator to split coalescing out from
allocation, making coalescers pluggable.</li>
<li>Evan enhanced LSR to support induction variable reuse when the induction
variables have different widths.</li>
</ul>
@ -177,91 +290,22 @@ optimizer, speeding it up and making it more aggressive. For example:</p>
</div>
<div class="doc_text">
<p>New features include:
<p>New target-specific features include:
</p>
<ul>
<li>Bruno Cardoso Lopes contributed initial MIPS support. It is sufficient to
run many small programs, but is still incomplete and is not yet
fully performant.</li>
<li>Bill Wendling added SSSE3 support to the X86 backend.</li>
<li>Nicholas Geoffray contributed improved linux/ppc ABI and JIT support.</li>
<li>Dale Johannesen rewrote handling of 32-bit float values in the X86 backend
when using the floating point stack, fixing several nasty bugs.</li>
<li>Dan contributed rematerialization support for the X86 backend, in addition
to several X86-specific micro optimizations.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="llvmgccimprovements">llvm-gcc Improvements</a>
</div>
<div class="doc_text">
<p>New features include:
</p>
<ul>
<li>Duncan and Anton made significant progress chasing down a number of problems
with C++ Zero-Cost exception handling in llvm-gcc 4.0 and 4.2. It is now at
the point where it "just works" on linux/X86-32 and has partial support on
other targets.</li>
<li>Devang and Duncan fixed a huge number of bugs relating to bitfields, pragma
pack, and variable sized fields in structures.</li>
<li>Tanya implemented support for <tt>__attribute__((noinline))</tt> in
llvm-gcc, and added support for generic variable annotations which are
propagated into the LLVM IR, e.g.
"<tt>int X __attribute__((annotate("myproperty")));</tt>".</li>
<li>Sheng Zhou and Christopher Lamb implemented alias analysis support for
"restrict" pointer arguments to functions.</li>
<li>Duncan contributed support for trampolines (taking the address of a nested
function). Currently this is only supported on the X86-32 target.</li>
<li>Lauro Ramos Venancio contributed support to encode alignment info in
load and store instructions, the foundation for other alignment-related
work.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="coreimprovements">LLVM Core Improvements</a>
</div>
<div class="doc_text">
<p>New features include:
</p>
<ul>
<li>Neil Booth contributed a new "APFloat" class, which ensures that floating
point representation and constant folding is not dependent on the host
architecture that builds the application. This support is the foundation
for "long double" support that will be wrapped up in LLVM 2.2.</li>
<li>Based on the APFloat class, Dale redesigned the internals of the ConstantFP
class and has been working on extending the core and optimizer components to
support various target-specific 'long double's. We expect this work to be
completed in LLVM 2.2.</li>
<li>LLVM now provides an LLVMBuilder class, which makes it significantly easier
to create LLVM IR instructions.</li>
<li>Reid contributed support for intrinsics that take arbitrary integer typed
arguments. Dan Gohman and Chandler extended it to support arbitrary
floating point arguments and vectors.</li>
<li>Evan contributed support to the X86 backend to model the mod/ref behavior
of the EFLAGS register explicitly in all instructions. This gives more freedom
to the scheduler, and is a more explicit way to model the instructions.</li>
<li>Dale contributed support for exception handling on Darwin/PPC and he and
Anton got x86-64 working.</li>
<li>Evan turned on if-conversion by default for ARM, allowing LLVM to take
advantage of its predication features.</li>
<li>Bruno added PIC support to the MIPS backend, fixed many bugs and improved
support for architecture variants.</li>
<li>Arnold Schwaighofer added initial support for X86 tail calls.</li>
<li>Evan contributed several enhancements to Darwin/x86 debug information.</li>
<li>Duncan added x86-64 support for trampolines (pointers to nested functions).</li>
</ul>
</div>
@ -276,13 +320,18 @@ optimizer, speeding it up and making it more aggressive. For example:</p>
</p>
<ul>
<li>Sterling Stein contributed a new BrainF frontend, located in llvm/examples.
This shows a some of the more modern APIs for building a front-end, and
demonstrates JIT compiler support.</li>
<li>Gordon expanded and updated the <a href="Passes.html">LLVM Analysis and
Transformation Passes</a> reference to include descriptions for each pass.</li>
<li>David Green contributed a new <tt>--enable-expensive-checks</tt> configure
option which enables STL checking, and fixed several bugs exposed by
it.</li>
<li>We rewrote the lexer and parser used by TableGen to make them simpler
and cleaner. This gives tblgen support for 'caret diagnostics'. The .ll file
lexer was also rewritten to support caret diagnostics but doesn't use this
support yet.</li>
<li>Dale has been grinding through the GCC testsuite, and marked many
LLVM-incompatible tests as not-to-be-run (for example, if they are grepping
through some GCC dump file that LLVM doesn't produce), he also found and fixed
many LLVM bugs exposed by the testsuite.</li>
</ul>
</div>
@ -300,9 +349,9 @@ optimizer, speeding it up and making it more aggressive. For example:</p>
<ul>
<li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
(and probably other unix-like systems).</li>
<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
<li>PowerPC and X86-based Mac OS X systems, running 10.3 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 using MinGW libraries (native).</li>
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
support is available for native builds with Visual C++).</li>
<li>Sun UltraSPARC workstations running Solaris 8.</li>
@ -348,13 +397,12 @@ useful to some people. In particular, if you would like to work on one of these
components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
<ul>
<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in a
future release.</li>
<li>The MSIL backend is experimental.</li>
<li>The IA64 code generator is experimental.</li>
<li>The Alpha backend is experimental.</li>
<li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
<tt>-filetype</tt> llc option.</li>
<li>The <tt>-cee</tt> pass is known to be buggy and will be removed in
LLVM 2.3.</li>
<li>The MSIL, IA64, Alpha, and MIPS backends are experimental.</li>
<li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
value for this option.</li>
<li>The llvmc tool is not supported.</li>
</ul>
</div>
@ -372,6 +420,8 @@ components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/l
<li>The X86 backend occasionally has <a href="http://llvm.org/PR1649">alignment
problems</a> on operating systems that don't require 16-byte stack alignment
(including most non-darwin OS's like linux).</li>
<li>The X86 backend generates inefficient floating point code when configured to
generate code for systems that don't have SSE2.</li>
</ul>
</div>
@ -384,8 +434,6 @@ components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/l
<div class="doc_text">
<ul>
<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
implement ordered FP comparisons</a>.</li>
<li>The Linux PPC32/ABI support needs testing for the interpreter and static
compilation, and lacks support for debug information.</li>
</ul>
@ -405,7 +453,7 @@ processors, thumb programs can crash or produce wrong
results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
</li>
<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
<li>There is a bug in QEMU-ARM (&lt;= 0.9.0) which causes it to incorrectly execute
programs compiled with LLVM. Please use more recent versions of QEMU.</li>
</ul>
@ -486,6 +534,7 @@ programs.</li>
<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
C++ code compiled with LLC or native compilers.</li>
<li>The C backend does not support all exception handling constructs.</li>
</ul>
</div>
@ -496,13 +545,59 @@ programs.</li>
<a name="c-fe">Known problems with the C front-end</a>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="ada-fe">Known problems with the Ada front-end</a>
</div>
<div class="doc_text">
The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
technology and problems should be expected.
<ul>
<li>The Ada front-end currently only builds on x86-32. This is mainly due
to lack of trampoline support (pointers to nested functions) on other platforms,
however it <a href="http://llvm.org/PR2006">also fails to build on x86-64</a>
which does support trampolines.</li>
<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
Workaround: configure with --disable-bootstrap.</li>
<li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
fail (c380004 also fails with gcc-4.2 mainline).</li>
<li>Many gcc specific Ada tests continue to crash the compiler.</li>
<li>The -E binder option (exception backtraces)
<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
crashing if an exception is raised. Workaround: do not use -E.</li>
<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
or finish at a non-byte offset</a> in a record. Workaround: do not pack records
or use representation clauses that result in a field of a non-discrete type
starting or finishing in the middle of a byte.</li>
<li>The lli interpreter <a href="http://llvm.org/PR2009">considers 'main'
as generated by the Ada binder to be invalid</a>.
Workaround: hand edit the file to use pointers for argv and envp rather than
integers.</li>
<li>The -fstack-check option <a href="http://llvm.org/PR2008">is ignored</a>.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="fortran-fe">Known problems with the Fortran front-end</a>
</div>
<div class="doc_text">
<ul>
<li>The llvm-gcc 4.2 gfortran front-end supports a broad range of Fortran code, but does
<a href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
</ul>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">Bugs</div>
<div class="doc_text">
<p>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
Optimization</a> on most platforms "out-of-the-box". Please inquire on the
<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
Optimization</a> on most platforms "out-of-the-box". Please inquire on the
llvmdev mailing list if you are interested.</p>
</div>
@ -515,10 +610,6 @@ llvmdev mailing list if you are interested.</p>
<div class="doc_text">
<ul>
<li><p>"long double" is silently transformed by the front-end into "double". There
is no support for floating point data types of any size other than 32 and 64
bits.</p></li>
<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
</li>
@ -529,7 +620,7 @@ bits.</p></li>
As in Algol and Pascal, lexical scoping of functions.
Nested functions are supported, but llvm-gcc does not support
taking the address of a nested function (except on the X86-32 target)
taking the address of a nested function (except on X86 targets)
or non-local gotos.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
@ -541,11 +632,11 @@ bits.</p></li>
<tt>const</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
<tt>deprecated</tt>, <tt>fastcall</tt>, <tt>format</tt>,
<tt>format_arg</tt>, <tt>non_null</tt>, <tt>noinline</tt>,
<tt>noreturn</tt>, <tt>pure</tt>, <tt>regparm</tt>
<tt>noreturn</tt>, <tt>nothrow</tt>, <tt>pure</tt>, <tt>regparm</tt>
<tt>section</tt>, <tt>stdcall</tt>, <tt>unused</tt>, <tt>used</tt>,
<tt>visibility</tt>, <tt>warn_unused_result</tt>, <tt>weak</tt><br>
<b>Ignored:</b> <tt>nothrow</tt>, <tt>malloc</tt>,
<b>Ignored:</b> <tt>malloc</tt>,
<tt>no_instrument_function</tt></li>
</ol>
</li>
@ -623,29 +714,8 @@ tested and works for a number of non-trivial programs, including LLVM
itself, Qt, Mozilla, etc.</p>
<ul>
<li>Exception handling only works well on the linux/X86-32 target.
In some cases, illegally throwing an exception does not result
in a call to terminate.</li>
<!-- NO EH Support!
<li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
function and in the <tt>setjmp</tt> receiver function may not be run.
Objects in intervening stack frames will be destroyed, however (which is
better than most compilers).</li>
<li>The LLVM C++ front-end follows the <a
href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
This document, which is not Itanium specific, specifies a standard for name
mangling, class layout, v-table layout, RTTI formats, and other C++
representation issues. Because we use this API, code generated by the LLVM
compilers should be binary compatible with machine code generated by other
Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
<i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
different from the model used in the Itanium ABI, so <b>exceptions will not
interact correctly</b>. </li>
-->
<li>Exception handling only works well on the X86 and PowerPC targets.
It works well for x86-64 darwin but not x86-64 linux.</li>
</ul>
</div>
@ -681,7 +751,7 @@ lists</a>.</p>
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src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
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