+
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 2.0 Release Notes</title>
+ <title>LLVM 2.3 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.0 Release Notes</div>
+<div class="doc_title">LLVM 2.3 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
+ <li><a href="#changes">Major Changes and Sub-project Status</a></li>
<li><a href="#whatsnew">What's New?</a></li>
<li><a href="GettingStarted.html">Installation Instructions</a></li>
<li><a href="#portability">Portability and Supported Platforms</a></li>
<p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
</div>
+<!-- Done through Week-of-Mon-20080324.txt -->
+
<!-- *********************************************************************** -->
<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 2.0. Here we describe the status of LLVM, including any
-known problems and major improvements from the previous release. All LLVM
+infrastructure, release 2.3. 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>.
+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_section">
- <a name="whatsnew">What's New?</a>
+ <a name="changes">Major Changes and Sub-project Status</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
-<p>This is the eleventh public release of the LLVM Compiler Infrastructure.
-Being the first major release since 1.0, this release is different in several
-ways from our previous releases:</p>
+<p>This is the fourteenth public release of the LLVM Compiler Infrastructure.
+It includes a large number of features and refinements from LLVM 2.2.</p>
-<ol>
-<li>We took this as an opportunity to
-break backwards compatibility with the LLVM 1.x bytecode and .ll file format.
-If you have LLVM 1.9 .ll files that you would like to upgrade to LLVM 2.x, we
-recommend the use of the stand alone <a href="#llvm-upgrade">llvm-upgrade</a>
-tool. We intend to keep compatibility with .ll and .bc formats within the 2.x
-release series, like we did within the 1.x series.</li>
-<li>There are several significant change to the LLVM IR and internal APIs, such
- as a major overhaul of the type system, the completely new bitcode file
- format, etc.</li>
-<li>We designed the release around a 6 month release cycle instead of the usual
- 3-month cycle. This gave us extra time to develop and test some of the
- more invasive features in this release.</li>
-<li>LLVM 2.0 no longer supports the llvm-gcc3 front-end.</li>
-</ol>
+</div>
-<p>Note that while this is a major version bump, this release has been
- extensively tested on a wide range of software. It is easy to say that this
- is our best release yet, in terms of both features and correctness.</p>
+<!-- Unfinished features in 2.3:
+ Machine LICM
+ Machine Sinking
+ LegalizeDAGTypes
+ -->
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="changes">Major Changes in LLVM 2.3</a>
+</div>
+
+<div class="doc_text">
+
+<p>LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with
+ llvm-gcc 4.2.</p>
+
+<p>LLVM 2.3 no longer includes the <tt>llvm-upgrade</tt> tool. It was useful
+ for upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a
+ previous LLVM release to do this. One nice impact of this is that the LLVM
+ regression test suite no longer depends on llvm-upgrade, which makes it run
+ faster.</p>
+
+<p>The <tt>llvm2cpp</tt> tool has been folded into llc, use
+ <tt>llc -march=cpp</tt> instead of <tt>llvm2cpp</tt>.</p>
+
+<p>LLVM API Changes:</p>
+
+<ul>
+<li>Several core LLVM IR classes have migrated to use the
+ '<tt>FOOCLASS::Create(...)</tt>' pattern instead of '<tt>new
+ FOOCLASS(...)</tt>' (e.g. where FOOCLASS=<tt>BasicBlock</tt>). We hope to
+ standardize on <tt>FOOCLASS::Create</tt> for all IR classes in the future,
+ but not all of them have been moved over yet.</li>
+<li>LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to
+ IRBuilder.</li>
+<li>MRegisterInfo was renamed to TargetRegisterInfo.</li>
+<li>The MappedFile class is gone, please use MemoryBuffer instead.</li>
+<li>The '<tt>-enable-eh</tt>' flag to llc has been removed. Now code should
+ encode whether it is safe to omit unwind information for a function by
+ tagging the Function object with the '<tt>nounwind</tt>' attribute.</li>
+
+</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="newfeatures">New Features in LLVM 2.0</a>
+<a name="otherprojects">Other LLVM Sub-Projects</a>
+</div>
+
+<div class="doc_text">
+<p>
+The core LLVM 2.3 distribution currently consists of code from the core LLVM
+repository (which roughly contains the LLVM optimizer, code generators and
+supporting tools) and the llvm-gcc repository. In addition to this code, the
+LLVM Project includes other sub-projects that are in development. The two which
+are the most actively developed are the new <a href="#vmkit">vmkit Project</a>
+and the <a href="#clang">Clang Project</a>.
+</p>
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsubsection">
+<a name="vmkit">vmkit</a>
+</div>
+
+<div class="doc_text">
+<p>
+The "vmkit" project is a new addition to the LLVM family. It is an
+implementation of a JVM and a CLI Virtual Machines (Microsoft .NET is an
+implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
+
+<p>The JVM, called JnJVM, executes real-world applications such as Apache
+projects (e.g. Felix and Tomcat) and the SpecJVM98 benchmark. It uses the GNU
+Classpath project for the base classes. The CLI implementation, called N3, is
+its in early stages but can execute simple applications and the "pnetmark"
+benchmark. It uses the pnetlib project as its core library.</p>
+
+<p>The 'vmkit' VMs compare in performance with industrial and top open-source
+VMs on scientific applications. Besides the JIT, the VMs use many features of
+the LLVM framework, including the standard set of optimizations, atomic
+operations, custom function provider and memory manager for JITed methods, and
+specific virtual machine optimizations. vmkit is not an official part of LLVM
+2.3 release. It is publicly available under the LLVM license and can be
+downloaded from:
+</p>
+
+<p>
+<tt>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</tt>
+</p>
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsubsection">
+<a name="clang">Clang</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>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. Clang is continuing to make major strides forward in all
+areas. Its C and Objective-C parsing support is very solid, and the code
+generation support is far enough along to build many C applications. While not
+yet production quality, it is progressing very nicely. In addition, C++
+front-end work has started to make significant progress.</p>
+
+<p>At this point, Clang is most useful if you are interested in source-to-source
+transformations (such as refactoring) and other source-level tools for C and
+Objective-C. Clang now also includes tools for turning C code into pretty HTML,
+and includes a new <a href="http://clang.llvm.org/StaticAnalysis.html">static
+analysis tool</a> in development. This tool is automatically focused on finding
+bugs in C and Objective-C code.</p>
+
+</div>
+
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="whatsnew">What's New?</a>
+</div>
+<!-- *********************************************************************** -->
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="majorfeatures">Major New Features</a>
+</div>
+
+<div class="doc_text">
+
+<p>LLVM 2.3 includes several major new capabilities:</p>
<ul>
-<li></li>
+<li><p>The biggest change in LLVM 2.3 is Multiple Return Value (MRV) support.
+ MRVs allow LLVM IR to directly represent functions that return multiple
+ values without having to pass them "by reference" in the LLVM IR. This
+ allows a front-end to generate more efficient code, as MRVs are generally
+ returned in registers if a target supports them. See the <a
+ href="LangRef.html#i_getresult">LLVM IR Reference</a> for more details.</p>
+
+ <p>MRVs are fully supported in the LLVM IR, but are not yet fully supported in
+ on all targets. However, it is generally safe to return up to 2 values from
+ a function: most targets should be able to handle at least that. MRV
+ support is a critical requirement for X86-64 ABI support, as X86-64 requires
+ the ability to return multiple registers from functions, and we use MRVs to
+ accomplish this in a direct way.</p></li>
+
+<li><p>LLVM 2.3 includes a complete reimplementation of the "<tt>llvmc</tt>"
+ tool. It is designed to overcome several problems with the original
+ <tt>llvmc</tt> and to provide a superset of the features of the
+ '<tt>gcc</tt>' driver.</p>
+
+<p>The main features of <tt>llvmc2</tt> are:
+ <ul>
+ <li>Extended handling of command line options and smart rules for
+ dispatching them to different tools.</li>
+ <li>Flexible (and extensible) rules for defining different tools.</li>
+ <li>The different intermediate steps performed by tools are represented
+ as edges in the abstract graph.</li>
+ <li>The 'language' for driver behavior definition is tablegen and thus
+ it's relatively easy to add new features.</li>
+ <li>The definition of driver is transformed into set of C++ classes, thus
+ no runtime interpretation is needed.</li>
+ </ul></p>
+ </li>
+
+<li><p>LLVM 2.3 includes a completely rewritten interface for <a
+ href="LinkTimeOptimization.html">Link Time Optimization</a>. This interface
+ is written in C, which allows for easier integration with C code bases, and
+ incorporates improvements we learned about from the first incarnation of the
+ interface.</p></li>
+
+<li><p>The <a href="tutorial/LangImpl1.html">Kaleidoscope tutorial</a> now
+ includes a "port" of the tutorial that <a
+ href="tutorial/OCamlLangImpl1.html">uses the Ocaml bindings</a> to implement
+ the Kaleidoscope language.</p></li>
+
</ul>
-
+
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="codegen">Code
-Generator Enhancements</a></div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="llvm-gcc">llvm-gcc 4.2 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>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end.</p>
+
+<p>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
+front-end. Objective-C now works very well on Mac OS/X.</p>
+
+<p>Fortran EQUIVALENCEs are now supported by the gfortran front-end.</p>
+
+<p>llvm-gcc 4.2 includes many other fixes which improve conformance with the
+relevant parts of the GCC testsuite.</p>
+
+</div>
+
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="coreimprovements">LLVM Core Improvements</a>
+</div>
+
+<div class="doc_text">
+<p>New features include:
</p>
+
+Common linkage?
+
+Atomic operation support, Alpha, X86, X86-64, PowerPC. "__sync_synchronize",
+"__sync_val_compare_and_swap", etc
+
<ul>
-<li></li>
+<li>The C and Ocaml bindings have received additional improvements. The
+bindings now cover pass managers, several transformation passes, iteration
+over the LLVM IR, target data, and parameter attribute lists.</li>
</ul>
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="optimizer">Optimizer Improvements</a>
+</div>
+
+<div class="doc_text">
+
+<p>In addition to a huge array of bug fixes and minor performance tweaks, the
+LLVM 2.3 optimizers support a few major enhancements:</p>
-<p>In addition, the LLVM target description format has itself been extended in
- several ways:</p>
-
<ul>
-<li></li>
+
+<li>Loop index set splitting on by default.<p>
+This transformation hoists conditions from loop bodies and reduces loop's
+iteration space to improve performance. For example, <p>
+<pre>
+for (i = LB; i < UB; ++i)
+ if (i <= NV)
+ LOOP_BODY
+</pre>
+is transformed into
+<pre>
+NUB = min(NV+1, UB)
+for (i = LB; i < NUB; ++i)
+ LOOP_BODY
+</pre>
+</li>
+
+<li>LLVM includes a new <tt>memcpy</tt> optimization pass which removes
+dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and performs
+return slot optimization. The LLVM optimizer now notices long sequences of
+consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li>
+
+<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
+<tt>memset</tt> is now more aggressive.</li>
+
+<li>The aggressive dead code elimination (ADCE) optimization has been rewritten
+to make it both faster and safer in the presence of code containing infinite
+loops. Some of its prior functionality has been factored out into the loop
+deletion pass, which <em>is</em> safe for infinite loops.</li>
+
+<li>Several optimizations have been sped up, leading to faster code generation
+ with the same code quality.</li>
+
+<li>The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm
+ functions for C-based languages, has been rewritten to be a FunctionPass
+ instead a ModulePass. This allows it to be run more often and to be
+ included at -O1 in llvm-gcc. It was also extended to include more
+ optimizations and several corner case bugs were fixed.</li>
+
+<li>LLVM now includes a simple 'Jump Threading' pass, which attempts to simplify
+ conditional branches using information about predecessor blocks, simplifying
+ the control flow graph. This pass is pretty basic at this point, but
+ catches some important cases and provides a foundation to build on.</li>
+
+<li>Several corner case bugs which could lead to deleting volatile memory
+ accesses have been fixed.</li>
</ul>
-<p>Further, several significant target-specific enhancements are included in
-LLVM 2.0:</p>
+</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></li>
+<li>MemOperand in the code generator: describe me!.</li>
+
+<li>The target-independent code generator infrastructure now uses LLVM's APInt
+ class to handle integer values, which allows it to support integer types
+ larger than 64 bits. Note that support for such types is also dependent on
+ target-specific support. Use of APInt is also a step toward support for
+ non-power-of-2 integer sizes.</li>
+
+<li>LLVM 2.3 includes several compile time speedups for code with large basic
+ blocks, particular in the instruction selection phase, register allocation,
+ scheduling, and tail merging/jump threading.</li>
+
+<li>Several improvements which make llc's <tt>--view-sunit-dags</tt>
+ visualization of scheduling dependency graphs easier to understand.</li>
+
+<li>The code generator allows targets to write patterns that generate subreg
+ references directly in .td files now.</li>
+
+<li><tt>memcpy</tt> lowering in the backend is more aggressive, particularly for
+ <tt>memcpy</tt> calls introduced by the code generator when handling
+ pass-by-value structure argument copies.</li>
+
+<li>Inline assembly with multiple register results now returns those results
+ directly in the appropriate registers, rather than going through memory.
+ Inline assembly that uses constraints like "ir" with immediates now use the
+ 'i' form when possible instead of always loading the value in a register.
+ This saves an instruction and reduces register use.</li>
+
+<li>Added support for PIC/GOT style tail calls on x86/32 and initial support
+ for tail calls on PowerPC 32 (it may also work on ppc64 but not
+ thoroughly tested).</li>
</ul>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="other">Other Improvements</a></div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="x86specific">X86/X86-64 Specific Improvements</a>
+</div>
+
<div class="doc_text">
-<p></p>
+<p>New target-specific features include:
+</p>
+
+<ul>
+<li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the
+ area of passing and returning structures by value. llvm-gcc compiled code
+ now interoperates very well on X86-64 systems with other compilers.</li>
+
+<li>Support for Win64 was added. This includes code generation itself, JIT
+ support and necessary changes to llvm-gcc.</li>
+
+<li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and
+ the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins. Various
+ generic vector operations (insert/extract/shuffle) are much more efficient
+ when SSE 4.1 is enabled. The JIT automatically takes advantage of these
+ instructions, but llvm-gcc must be explicitly told to use them, e.g. with
+ <tt>-march=penryn</tt>.</li>
+
+<li>The X86 backend now does a number of optimizations that aim to avoid
+ converting numbers back and forth from SSE registers to the X87 floating
+ point stack.</li>
+
+<li>The X86 backend supports stack realignment, which is particularly useful for
+ vector code on OS's without 16-byte aligned stacks.</li>
-<p>More specific changes include:</p>
+<li>The X86 backend now supports the "sseregparm" options in GCC, which allow
+ functions to be tagged as passing floating point values in SSE
+ registers.</li>
+
+<li>Trampolines (taking the address of a nested function) now work on
+ Linux/X86-64.</li>
+
+<li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch
+ instructions instead of being ignored.</li>
+
+<li>128-bit integers are now supported on X86-64 targets.</li>
+
+<li>The register allocator can now rematerialize PIC-base computations.</li>
+
+<li>The "t" and "f" inline assembly constraints for the X87 floating point stack
+ now work. However, the "u" constraint is still not fully supported.</li>
+
+</ul>
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="targetspecific">Other Target Specific Improvements</a>
+</div>
+
+<div class="doc_text">
+<p>New target-specific features include:
+</p>
<ul>
-<li></li>
+<li>The LLVM C backend now supports vector code.</li>
</ul>
+
+</div>
+
+
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="otherimprovements">Other Improvements</a>
</div>
+<div class="doc_text">
+<p>New features include:
+</p>
+<ul>
+<li>LLVM now builds with GCC 4.3.</li>
+<li>Bugpoint now supports running custom scripts (with the <tt>-run-custom</tt>
+ option) to determine how to execute the command and whether it is making
+ forward process.</li>
+</ul>
+
+</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<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 (IA32) 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 10.</li>
<li>Alpha-based machines running Debian GNU/Linux.</li>
-<li>Itanium-based machines running Linux and HP-UX.</li>
+<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
</ul>
-<p>The core LLVM infrastructure uses
-<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
+<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
to the machine and operating system on which it is built. However, minor
porting may be required to get LLVM to work on new platforms. We welcome your
portability patches and reports of successful builds or error messages.</p>
be broken or unreliable, or are in early development. These components should
not be relied on, and bugs should not be filed against them, but they may be
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>
+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>C++ EH support</li>
-<li>The IA64 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 MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
+<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
+ value for this option.</li>
</ul>
</div>
<div class="doc_text">
<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>.</li>
+ <li>The X86 backend does not yet support
+ all <a href="http://llvm.org/PR879">inline assembly that uses the X86
+ floating point stack</a>. It supports the 'f' and 't' constraints, but not
+ 'u'.</li>
+ <li>The X86 backend generates inefficient floating point code when configured
+ to generate code for systems that don't have SSE2.</li>
+ <li>Win64 code generation wasn't widely tested. Everything should work, but we
+ expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
+ currently due
+ to <a href="http://llvm.org/PR2255">several</a>
+ <a href="http://llvm.org/PR2257">bugs</a> in FP stackifier
</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 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#int_stacksave"><tt>llvm.stacksave</tt></a> or
-<a href="LangRef.html#int_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>
output with code built with other compilers, particularly for floating-point
programs.</li>
-<li>Defining vararg functions is not supported (but calling them is ok).</li>
+<li>Defining vararg functions is not supported (but calling them is OK).</li>
<li>The Itanium backend has bitrotted somewhat.</li>
</ul>
<!-- ======================================================================= -->
<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 Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
-processors, any thumb program compiled with LLVM crashes or produces 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>QEMU-ARM (<= 0.9.0) wrongly executes programs compiled with LLVM. A non-affected QEMU version must be used or this
-<a href="http://cvs.savannah.nongnu.org/viewcvs/qemu/target-arm/translate.c?root=qemu&r1=1.46&r2=1.47&makepatch=1&diff_format=h">
-patch</a> must be applied on QEMU.</li>
+<li><a href="http://llvm.org/PR802">The C backend has only basic support for
+ inline assembly code</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>
+<li>The C backend does not support all exception handling constructs.</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">
- <a name="c-fe">Known problems with the C front-end</a>
+ <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_text">
-<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>
-<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>The only major language feature of GCC not supported by llvm-gcc is
+ the <tt>__builtin_apply</tt> family of builtins. However, some extensions
+ are only supported on some targets. For example, trampolines are only
+ supported on some targets (these are used when you take the address of a
+ nested function).</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>If you run into GCC extensions which are not supported, please let us know.
+</p>
</div>
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">
- Notes
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
</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>
-
- <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/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>alias</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>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> 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>alias</tt>, <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>
- </ol>
-
- <p>The following extensions <b>are</b> known to be supported:</p>
-
- <ol>
- <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>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc-3.4.0/gcc/Lvalues.html#Lvalues">Lvalues</a>: Using <code>?:</code>, "<code>,</code>" and casts in lvalues.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals">Conditionals</a>: Omitting the middle operand of a <code>?:</code> expression.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html#Long%20Long">Long Long</a>: Double-word integers.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Complex.html#Complex">Complex</a>: Data types for complex numbers.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Hex-Floats.html#Hex%20Floats">Hex Floats</a>:Hexadecimal floating-point constants.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html#Zero%20Length">Zero Length</a>: Zero-length arrays.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html#Empty%20Structures">Empty Structures</a>: Structures with no members.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Variadic-Macros.html#Variadic%20Macros">Variadic Macros</a>: Macros with a variable number of arguments.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Escaped-Newlines.html#Escaped%20Newlines">Escaped Newlines</a>: Slightly looser rules for escaped newlines.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Extended%20Asm">Extended Asm</a>: Assembler instructions with C expressions as operands.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Constraints.html#Constraints">Constraints</a>: Constraints for asm operands.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html#Asm%20Labels">Asm Labels</a>: Specifying the assembler name to use for a C symbol.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Explicit-Reg-Vars.html#Explicit%20Reg%20Vars">Explicit Reg Vars</a>: Defining variables residing in specified registers.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html#Vector%20Extensions">Vector Extensions</a>: Using vector instructions through built-in functions.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Target-Builtins.html#Target%20Builtins">Target Builtins</a>: Built-in functions specific to particular targets.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Subscripting.html#Subscripting">Subscripting</a>: Any array can be subscripted, even if not an lvalue.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html#Pointer%20Arith">Pointer Arith</a>: Arithmetic on <code>void</code>-pointers and function pointers.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Initializers.html#Initializers">Initializers</a>: Non-constant initializers.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Compound-Literals.html#Compound%20Literals">Compound Literals</a>: Compound literals give structures, unions,
-or arrays as values.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated%20Inits">Designated Inits</a>: Labeling elements of initializers.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Cast-to-Union.html#Cast%20to%20Union">Cast to Union</a>: Casting to union type from any member of the union.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Case-Ranges.html#Case%20Ranges">Case Ranges</a>: `case 1 ... 9' and such.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Mixed-Declarations.html#Mixed%20Declarations">Mixed Declarations</a>: Mixing declarations and code.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Prototypes.html#Function%20Prototypes">Function Prototypes</a>: Prototype declarations and old-style definitions.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Comments.html#C_002b_002b-Comments">C++ Comments</a>: C++ comments are recognized.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html#Dollar%20Signs">Dollar Signs</a>: Dollar sign is allowed in identifiers.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Character-Escapes.html#Character%20Escapes">Character Escapes</a>: <code>\e</code> stands for the character <ESC>.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alignment.html#Alignment">Alignment</a>: Inquiring about the alignment of a type or variable.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline">Inline</a>: Defining inline functions (as fast as macros).</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Alternate-Keywords.html#Alternate%20Keywords">Alternate Keywords</a>:<code>__const__</code>, <code>__asm__</code>, etc., for header files.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Incomplete-Enums.html#Incomplete%20Enums">Incomplete Enums</a>: <code>enum foo;</code>, with details to follow.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function%20Names">Function Names</a>: Printable strings which are the name of the current function.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html#Return%20Address">Return Address</a>: Getting the return or frame address of a function.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Unnamed-Fields.html#Unnamed%20Fields">Unnamed Fields</a>: Unnamed struct/union fields within structs/unions.</li>
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute%20Syntax">Attribute Syntax</a>: Formal syntax for attributes.</li>
- </ol></li>
+<p>The C++ front-end is considered to be fully
+tested and works for a number of non-trivial programs, including LLVM
+itself, Qt, Mozilla, etc.</p>
+<ul>
+<li>Exception handling works well on the X86 and PowerPC targets, including
+X86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is
+supported on X86-64 linux, but that is disabled by default in this release.</li>
</ul>
-<p>If you run into GCC extensions which have not been included in any of these
-lists, please let us know (also including whether or not they work).</p>
-
</div>
+
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="c++-fe">Known problems with the C++ front-end</a>
-</div>
-
-<div class="doc_text">
-
-<p>For this release, the C++ front-end is considered to be fully
-tested and works for a number of non-trivial programs, including LLVM
-itself.</p>
-
-</div>
-
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">
- Notes
+ <a name="ada-fe">Known problems with the llvm-gcc 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>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>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). When built at -O3, the
+<a href="http://llvm.org/PR2421">cxg2021</a> ACATS test also fails.</li>
+<li>Some gcc specific Ada tests continue to crash the compiler. The testsuite
+reports most tests as having failed even though they pass.</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 <tt>lli</tt> 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 <tt>argv</tt> and
+<tt>envp</tt> rather than integers.</li>
+<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
+ignored</a>.</li>
</ul>
-
</div>
-
-
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="additionalinfo">Additional Information</a>
<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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