<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 1.9 Release Notes</title>
+ <title>LLVM 2.1 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 1.9 Release Notes</div>
+<div class="doc_title">LLVM 2.1 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
<div class="doc_text">
<p>This document contains the release notes for the LLVM compiler
-infrastructure, release 1.9. Here we describe the status of LLVM, including any
-known problems and major improvements from the previous release. The most
-up-to-date version of this document (corresponding to LLVM CVS) can be found
-on the <a
-href="http://llvm.org/releases/">LLVM releases web site</a>. If you are
-not reading this on the LLVM web pages, you should probably go there because
-this document may be updated after the release.</p>
+infrastructure, release 2.1. 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>
<p>For more information about LLVM, including information about the latest
release, please check out the <a href="http://llvm.org/">main LLVM
href="http://mail.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 CVS or the main LLVM web page,
-this document applies to the <i>next</i> release, not the current one. To see
-the release notes for the current or previous releases, see the <a
-href="http://llvm.org/releases/">releases page</a>.</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
+current one. To see the release notes for a specific releases, please see the
+<a href="http://llvm.org/releases/">releases page</a>.</p>
</div>
<div class="doc_text">
-<p>This is the tenth public release of the LLVM Compiler Infrastructure. This
-release incorporates a large number of enhancements, new features, and bug
-fixes. We recommend that all users of previous LLVM versions upgrade.
-</p>
+<p>This is the twelfth public release of the LLVM Compiler Infrastructure.
+It includes many features and refinements from LLVM 2.0.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="newfeatures">New Features in LLVM 1.9</a>
+<a name="frontends">New Frontends</a>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="x86-64">New X86-64 Backend</a></div>
<div class="doc_text">
-<p>LLVM 1.9 now fully supports the x86-64 instruction set on Mac OS/X, and
-supports it on Linux (and other operating systems) when compiling in -static
-mode. LLVM includes JIT support for X86-64, and supports both Intel EMT-64T
-and AMD-64 architectures. The X86-64 instruction set permits addressing a
-64-bit addressing space and provides the compiler with twice the
-number of integer registers to use.</p>
+
+<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>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>
+
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="lto">Link-Time Optimization integration
-with native linkers</a></div>
-<div class="doc_text">
-<p>LLVM now includes <a href="LinkTimeOptimization.html">liblto</a> which can
-be used to integrate LLVM Link-Time Optimization support into a native linker.
-This allows LLVM .bc to transparently participate with linking an application,
-even when some .o files are in LLVM form and some are not.</p>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="optimizer">Optimizer Improvements</a>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="dwarf">DWARF debugging
-support for Linux, Cygwin and MinGW on X86</a></div>
<div class="doc_text">
-<p>llvm-gcc4 now supports generating debugging info for Linux, Cygwin and MinGW.
-This extends the PPC/Darwin and X86/Darwin debugging support available in the
-1.8 release. DWARF is a standard debugging format used on many platforms.</p>
+
+<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>
+
+<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>
+
+</ul>
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="codegen">Code Generator Improvements</a>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="optimizer">Optimizer
-Improvements</a></div>
<div class="doc_text">
-<p>The mid-level optimizer is now faster and produces better code in many cases.
- Significant changes include:</p>
+
+<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>LLVM includes a new 'predicate simplifier' pass, which
- currently performs dominator tree-based optimizations.</li>
-<li>The complete loop unroll pass now supports unrolling of
- multiple basic block loops.</li>
-<li>The 'globalopt' pass can now perform the scalar replacement of
- aggregates transformation on some heap allocations.</li>
-<li>The globalsmodref-aa alias analysis can now track 'indirect pointer
- globals' more accurately.</li>
-<li>The instruction combiner can now perform element propagation
-analysis of vector expressions, eliminating computation of vector elements
-that are not used.</li>
+
+<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>
+
</ul>
-
+
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="codegen">Code
-Generator Enhancements</a></div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="targetspecific">Target Specific Improvements</a>
+</div>
<div class="doc_text">
-<p>
-The LLVM Target-Independent code generator now supports more target features and
-optimizes many cases more aggressively. New features include:
+<p>New features include:
</p>
<ul>
-<li>LLVM now includes a late branch folding pass which optimizes code
- layout, performs several branch optzns, and deletes unreachable code.</li>
-<li>The code generator now support targets that have pre/post-increment
- addressing modes.</li>
-<li>LLVM now supports dynamically-loadable register allocators and
- schedulers.</li>
-<li>LLVM 1.9 includes several improvements to inline asm support,
- including support for new constraints and modifiers.</li>
-<li>The register coalescer is now more aggressive than before,
- allowing it to eliminate more copies.</li>
-</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>
-<p>In addition, the LLVM target description format has itself been extended in
- several ways:</p>
-
-<ul>
-<li>tblgen now allows definition of '<a
- href="TableGenFundamentals.html#multiclass">multiclasses</a>' which can be
- used to factor instruction patterns more aggressively in .td files.</li>
-<li>LLVM has a new TargetAsmInfo class which captures a variety of
- information about the target assembly language format.</li>
-<li>.td files now support "<tt>${:foo}</tt>" syntax for encoding
- subtarget-specific assembler syntax into instruction descriptions.</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>
-<p>Further, several significant target-specific enhancements are included in
-LLVM 1.9:</p>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="llvmgccimprovements">llvm-gcc Improvements</a>
+</div>
+
+<div class="doc_text">
+<p>New features include:
+</p>
<ul>
-<li>The LLVM ARM backend now supports more instructions
- and the use of a frame pointer. It is now possible to build
- libgcc and a simple cross compiler, but it is not considered "complete" yet.
- </li>
-<li>LLVM supports the Win32 dllimport/dllexport linkage and
- stdcall/fastcall calling conventions.</li>
+<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_subsubsection"><a name="other">Other Improvements</a></div>
<div class="doc_text">
-<p>This release includes many other improvements, including improvements to
- the optimizers and code generators (improving the generated code) changes to
- speed up the compiler in many ways (improving algorithms and fine tuning
- code), and changes to reduce the code size of the compiler itself.</p>
-
-<p>More specific changes include:</p>
+<p>New features include:
+</p>
<ul>
-<li>The llvm-test framework now supports SPEC2006.</li>
-<li>LLVM now includes a <a href="GetElementPtr.html">FAQ about the
-<tt>getelementptr</tt> instruction</a>.</li>
-<li>Bugpoint now supports a new "<tt>-find-bugs</tt>" mode. This mode makes
- bugpoint permute pass sequences to try to expose bugs due to pass
- sequencing.</li>
-<li>The JIT now supports lazily streaming code from multiple modules at a
- time, implicitly linking the code as it goes.</li>
+<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>
</ul>
+
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="apichanges">Significant API Changes in LLVM 1.9</a>
+<a name="otherimprovements">Other Improvements</a>
</div>
<div class="doc_text">
-
-<p>Several significant API changes have been made. If you are maintaining
-out-of-tree code, please be aware that:</p>
+<p>New features include:
+</p>
<ul>
-<li>The ConstantSInt and ConstantUInt classes have been merged into the
- ConstantInt class.</li>
-<li><p>As a step towards making LLVM's integer types signless, several new
-instructions have been added to LLVM. The <tt>Div</tt> instruction is now
-<tt>UDiv</tt>, <tt>SDiv</tt>, and <tt>FDiv</tt>. The <tt>Rem</tt> instruction
-is now <tt>URem</tt>, <tt>SRem</tt> and <tt>FRem</tt>. See the
-<a href="LangRef.html">Language Reference</a> for details on these new
-instructions.</p>
-<li><p><tt>ConstantBool::True</tt> and <tt>ConstantBool::False</tt> have been
- renamed to <tt>ConstantBool::getTrue()</tt> and
- <tt>ConstantBool::getFalse()</tt>.</p></li>
-<li>The 'analyze' tool has been merged into the 'opt' tool.</li>
+<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>David Green contributed a new <tt>--enable-expensive-checks</tt> configure
+ option which enables STL checking, and fixed several bugs exposed by
+ it.</li>
</ul>
+
</div>
-
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="portability">Portability and Supported Platforms</a>
<p>LLVM is known to work on the following platforms:</p>
<ul>
- <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
+<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
+ 64-bit modes.</li>
<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
-<li>Sun UltraSPARC workstations running Solaris 8.</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>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
- 64-bit modes.</li>
+<li>Sun UltraSPARC workstations running Solaris 8.</li>
<li>Alpha-based machines running Debian GNU/Linux.</li>
<li>Itanium-based machines running Linux and HP-UX.</li>
</ul>
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 in a
+<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 ARM code generator is experimental.</li>
-<li>The Alpha JIT 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>
</ul>
<ul>
<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
- assembly that uses the X86 floating point stack</a>. See the <a
- href="http://llvm.org/PR879">bug</a> for details on workarounds on
- Linux.</li>
+ assembly that uses the X86 floating point stack</a>.</li>
+<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>
</ul>
</div>
<ul>
<li><a href="http://llvm.org/PR642">PowerPC backend does not correctly
implement ordered FP comparisons</a>.</li>
-<li>The 64-bit PowerPC backend is not fully stable. If you desire PPC64 support,
- please use mainline CVS LLVM, which has several important bug fixes.</li>
+<li>The Linux PPC32/ABI support needs testing for the interpreter and static
+compilation, and lacks support for debug information.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="sparc-be">Known problems with the SPARC back-end</a>
+ <a name="arm-be">Known problems with the ARM back-end</a>
</div>
<div class="doc_text">
<ul>
-<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
- support the 64-bit SPARC ABI (-m64).</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>
+<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
+programs compiled with LLVM. Please use more recent versions of QEMU.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="c-be">Known problems with the C back-end</a>
+ <a name="sparc-be">Known problems with the SPARC back-end</a>
</div>
<div class="doc_text">
<ul>
-
-<li>The C back-end produces code that violates the ANSI C Type-Based Alias
-Analysis rules. As such, special options may be necessary to compile the code
-(for example, GCC requires the <tt>-fno-strict-aliasing</tt> option). This
-problem probably cannot be fixed.</li>
-
-<li><a href="http://llvm.org/PR56">Zero arg vararg functions are not
-supported</a>. This should not affect LLVM produced by the C or C++
-frontends.</li>
-
-<li>The C backend does not correctly implement the <a
-href="LangRef.html#i_stacksave"><tt>llvm.stacksave</tt></a> or
-<a href="LangRef.html#i_stackrestore"><tt>llvm.stackrestore</tt></a>
-intrinsics. This means that some code compiled by it can run out of stack
-space if they depend on these (e.g. C99 varargs).</li>
-
-<li><a href="http://llvm.org/PR802">The C backend does not support inline
- assembly code</a>.</li>
+<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
+ support the 64-bit SPARC ABI (-m64).</li>
</ul>
</div>
<li>Defining vararg functions is not supported (but calling them is ok).</li>
+<li>The Itanium backend has bitrotted somewhat.</li>
</ul>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="arm-be">Known problems with the ARM back-end</a>
+ <a name="c-be">Known problems with the C back-end</a>
</div>
<div class="doc_text">
<ul>
-<li>The ARM backend is currently in early development stages, it is not
-ready for production use.</li>
+<li><a href="http://llvm.org/PR802">The C backend does not support inline
+ assembly code</a>.</li>
+<li><a href="http://llvm.org/PR1126">The C backend does not support vectors
+ yet</a>.</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>
</ul>
</div>
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="core">Known problems with the LLVM Core</a>
-</div>
-
-<div class="doc_text">
-
-<ul>
- <li>In the JIT, <tt>dlsym()</tt> on a symbol compiled by the JIT will not
- work.</li>
-</ul>
-</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<div class="doc_text">
-<p>
-
-<p>llvm-gcc4 is far more stable and produces better code than llvm-gcc3, but
-does not currently support <a href="http://llvm.org/PR869">Link-Time
-Optimization</a> or <a href="http://llvm.org/PR870">C++ Exception Handling</a>,
-which llvm-gcc3 does.</p>
-
-<p>llvm-gcc4 does not support the <a href="http://llvm.org/PR947">GCC indirect
-goto extension</a>, but llvm-gcc3 does.</p>
+<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
+llvmdev mailing list if you are interested.</p>
</div>
</div>
<div class="doc_text">
-
<ul>
-<li>"long double" is 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.</li>
+<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>Although many GCC extensions are supported, some are not. In particular,
- the following extensions are known to <b>not be</b> supported:
- <ol>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>: As in Algol and Pascal, lexical scoping of functions.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
- </ol>
-
- <p>The following GCC extensions are <b>partially</b> supported. An ignored
- attribute means that the LLVM compiler ignores the presence of the attribute,
- but the code should still work. An unsupported attribute is one which is
- ignored by the LLVM compiler and will cause a different interpretation of
- the program.</p>
+<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>
+<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
<ol>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
- Arrays whose length is computed at run time.<br>
- Supported, but allocated stack space is not freed until the function returns (noted above).</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nested%20Functions">Nested Functions</a>:
+
+ 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)
+ or non-local gotos.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
Declaring that functions have no side effects or that they can never
return.<br>
- <b>Supported:</b> <tt>constructor</tt>, <tt>destructor</tt>,
+ <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</tt>,
+ <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>noreturn</tt>,
+ <tt>format_arg</tt>, <tt>non_null</tt>, <tt>noinline</tt>,
+ <tt>noreturn</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>noinline</tt>,
- <tt>always_inline</tt>, <tt>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
- <tt>malloc</tt>, <tt>no_instrument_function</tt>, <tt>cdecl</tt><br>
-
- <b>Unsupported:</b> <tt>alias</tt>, <tt>regparm</tt>, all other target specific
- attributes</li>
-
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
- Specifying attributes of variables.<br>
- <b>Supported:</b> <tt>cleanup</tt>, <tt>common</tt>, <tt>nocommon</tt>,
- <tt>deprecated</tt>, <tt>dllimport</tt>, <tt>dllexport</tt>,
- <tt>section</tt>, <tt>transparent_union</tt>, <tt>unused</tt>,
- <tt>used</tt>, <tt>weak</tt><br>
-
- <b>Unsupported:</b> <tt>aligned</tt>, <tt>mode</tt>, <tt>packed</tt>,
- <tt>shared</tt>, <tt>tls_model</tt>,
- <tt>vector_size</tt>, all target specific attributes.
- </li>
-
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.<br>
- <b>Supported:</b> <tt>transparent_union</tt>, <tt>unused</tt>,
- <tt>deprecated</tt>, <tt>may_alias</tt><br>
-
- <b>Unsupported:</b> <tt>aligned</tt>, <tt>packed</tt>,
- all target specific attributes.</li>
-
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
- Other built-in functions.<br>
- We support all builtins which have a C language equivalent (e.g.,
- <tt>__builtin_cos</tt>), <tt>__builtin_alloca</tt>,
- <tt>__builtin_types_compatible_p</tt>, <tt>__builtin_choose_expr</tt>,
- <tt>__builtin_constant_p</tt>, and <tt>__builtin_expect</tt>
- (currently ignored). We also support builtins for ISO C99 floating
- point comparison macros (e.g., <tt>__builtin_islessequal</tt>),
- <tt>__builtin_prefetch</tt>, <tt>__builtin_popcount[ll]</tt>,
- <tt>__builtin_clz[ll]</tt>, and <tt>__builtin_ctz[ll]</tt>.</li>
+ <b>Ignored:</b> <tt>nothrow</tt>, <tt>malloc</tt>,
+ <tt>no_instrument_function</tt></li>
</ol>
+</li>
- <p>The following extensions <b>are</b> known to be supported:</p>
+<li><p>llvm-gcc supports the vast majority of GCC extensions, including:</p>
<ol>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas">Pragmas</a>: Pragmas accepted by GCC.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Local-Labels.html#Local%20Labels">Local Labels</a>: Labels local to a block.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#Other%20Builtins">Other Builtins</a>:
+ Other built-in functions.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html#Variable%20Attributes">Variable Attributes</a>:
+ Specifying attributes of variables.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html#Type%20Attributes">Type Attributes</a>: Specifying attributes of types.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Thread_002dLocal.html">Thread-Local</a>: Per-thread variables.</li>
+ <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html#Variable%20Length">Variable Length</a>:
+ Arrays whose length is computed at run time.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels%20as%20Values">Labels as Values</a>: Getting pointers to labels and computed gotos.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html#Statement%20Exprs">Statement Exprs</a>: Putting statements and declarations inside expressions.</li>
<li><a href="http://gcc.gnu.org/onlinedocs/gcc/Typeof.html#Typeof">Typeof</a>: <code>typeof</code>: referring to the type of an expression.</li>
<div class="doc_text">
-<p>For this release, the C++ front-end is considered to be fully
+<p>The C++ front-end is considered to be fully
tested and works for a number of non-trivial programs, including LLVM
-itself.</p>
-
-</div>
+itself, Qt, Mozilla, etc.</p>
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">
- Notes
-</div>
-
-<div class="doc_text">
<ul>
-<li>llvm-gcc4 does not support C++ exception handling at all yet.</li>
+<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
<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>
-
+-->
</ul>
</div>
<div class="doc_text">
<p>A wide variety of additional information is available on the <a
-href="http://llvm.org">LLVM web page</a>, including <a
-href="http://llvm.org/docs/">documentation</a> and <a
-href="http://llvm.org/pubs/">publications describing algorithms and
-components implemented in LLVM</a>. The web page also contains versions of the
-API documentation which is up-to-date with the CVS version of the source code.
+href="http://llvm.org">LLVM web page</a>, in particular in the <a
+href="http://llvm.org/docs/">documentation</a> section. The web page also
+contains versions of the API documentation which is up-to-date with the
+Subversion version of the source code.
You can access versions of these documents specific to this release by going
into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
<a href="http://validator.w3.org/check/referer"><img
src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
- <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
+ <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Last modified: $Date$
</address>
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