<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 2.2 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 1.9 Release Notes</div>
+<div class="doc_title">LLVM 2.2 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
<p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
</div>
+
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="intro">Introduction</a>
<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 2.2. 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>
<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 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="newfeatures">New Features in LLVM 1.9</a>
+<a name="deprecation">Deprecated features in LLVM 2.2</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>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_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="frontends">llvm-gcc 4.0, llvm-gcc 4.2, and clang</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>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). 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>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_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>LLVM 2.2 includes several major new capabilities:</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>Scott Michel contributed an SPU backend, which generates code for the
+vector coprocessors on the Cell processor. (Status?)</li>
+
+<li>llvm-gcc 4.2 has significantly improved support for the GCC Ada (GNAT) and
+FORTRAN (gfortran) frontends. Duncan has the llvm-gcc 4.2 GNAT front-end
+supporting almost all of the ACATS testsuite (except 2 tests?). 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>
+
+<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_subsubsection"><a name="codegen">Code
-Generator Enhancements</a></div>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="coreimprovements">LLVM Core 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>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 use 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>Duncan 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>
-<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>
</ul>
+
+</div>
-<p>Further, several significant target-specific enhancements are included in
-LLVM 1.9:</p>
+<!--=========================================================================-->
+<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>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>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 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>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="other">Other Improvements</a></div>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="optimizer">Optimizer 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>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>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>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>
+
+<li>Dan Gohman contributed several enhancements to Loop Strength Reduction (LSR)
+to make it more aggressive with SSE intrinsics.</li>
+
+<li>Evan added support for simple exit value substitution to LSR.</li>
+
+<li>Evan enhanced LSR to support induction variable reuse when the induction
+variables have different widths.</li>
+
</ul>
+
</div>
+
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="apichanges">Significant API Changes in LLVM 1.9</a>
+<a name="targetspecific">Target Specific Improvements</a>
</div>
<div class="doc_text">
+<p>New target-specific features include:
+</p>
+
+<ul>
+<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/x86-64 and
+Darwin/ppc.</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 support for X86 tail calls (limitations?
+details?).</li>
+<li>Evan contributed several enhancements to Darwin/x86 debug information,
+and improvements at -O0 (details?).</li>
+</ul>
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="otherimprovements">Other Improvements</a>
+</div>
-<p>Several significant API changes have been made. If you are maintaining
-out-of-tree code, please be aware that:</p>
+<div class="doc_text">
+<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>Gordon expanded and updated the <a href="Passes.html">LLVM Analysis and
+Transformation Passes</a> reference to include descriptions for each pass.</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>
-
<!-- *********************************************************************** -->
<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>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
-<li>Sun UltraSPARC workstations running Solaris 8.</li>
+<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 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
- future release.</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>"<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>
<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>
+<li>The X86 backend generates inefficient floating point code when configured to
+ generate code for systems that don't have SSE2.</li>
</ul>
</div>
<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 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-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>
</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>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>format</tt>, <tt>format_arg</tt>, <tt>non_null</tt>,
- <tt>noreturn</tt>, <tt>constructor</tt>, <tt>destructor</tt>,
- <tt>unused</tt>, <tt>used</tt>,
- <tt>deprecated</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>section</tt>, <tt>alias</tt>,
- <tt>visibility</tt>, <tt>regparm</tt>, <tt>stdcall</tt>,
- <tt>fastcall</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>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>section</tt>, <tt>shared</tt>, <tt>tls_model</tt>,
- <tt>vector_size</tt>, <tt>dllimport</tt>,
- <tt>dllexport</tt>, all target specific attributes.</li>
+ <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>noinline</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>
- <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>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>
+itself, Qt, Mozilla, etc.</p>
-</div>
-
-<!-- _______________________________________________________________________ -->
-<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>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.</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>
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+ <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
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