+
<!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 2.1 Release Notes</title>
+ <title>LLVM 2.3 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.1 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 2.1. Here we describe the status of LLVM, including
+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>.</p>
<!-- *********************************************************************** -->
<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 twelfth public release of the LLVM Compiler Infrastructure.
-It includes many features and refinements from LLVM 2.0.</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>
</div>
+<!-- Unfinished features in 2.3:
+ Machine LICM
+ Machine Sinking
+ LegalizeDAGTypes
+ -->
+
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="frontends">New Frontends</a>
+<a name="changes">Major Changes in LLVM 2.3</a>
</div>
<div class="doc_text">
-<p>LLVM 2.1 brings two new beta C front-ends. First, Duncan, Anton and Devang
-start syncing up llvm-gcc with GCC 4.2, yielding "llvm-gcc 4.2" (creative,
-huh?). llvm-gcc 4.2 has the promise to bring much better FORTRAN and Ada
-support to LLVM as well as features like atomic builtins, OpenMP, and many other
-things. Check it out!</p>
+<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>Second, LLVM now includes its own native C and Objective-C front-end (C++ is
-in progress, but is not very far along) code named "<a
-href="http://clang.llvm.org/">clang</a>". This front-end has a number of great
-features, primarily aimed at source-level analysis and speeding up compile-time.
-At this point though, the LLVM Code Generator component is still very early in
-development, so it's mostly useful for people looking to build source-level
-analysis tools or source-to-source translators.</p>
+<p>The <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="optimizer">Optimizer Improvements</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>
-<p>Some of the most noticable improvements this release have been in the
-optimizer, speeding it up and making it more aggressive</p>
+<!--=========================================================================-->
+<div class="doc_subsubsection">
+<a name="vmkit">vmkit</a>
+</div>
-<ul>
+<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>
-<li>Owen DSE and MemDep analysis</li>
-<li>Owen GVN</li>
-<li>Owen GVN-PRE, not in llvm-gcc</li>
-<li>Devang merged ETForest and DomTree into a single easier to use data
-structure.</li>
-<li>Nick Lewycky improved loop trip count analysis to handle many more common
-cases.</li>
+<p>
+<tt>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</tt>
+</p>
-</ul>
+</div>
+<!--=========================================================================-->
+<div class="doc_subsubsection">
+<a name="clang">Clang</a>
+</div>
+
+<div class="doc_text">
+
+<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="codegen">Code Generator Improvements</a>
+<a name="majorfeatures">Major New Features</a>
</div>
<div class="doc_text">
-<p>foo</p>
+<p>LLVM 2.3 includes several major new capabilities:</p>
<ul>
+<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>
-<li>Dale finished up the Tail Merging optimization in the code generator,
-enabling it by default. This produces smaller code that is also faster in some
-cases.</li>
+</ul>
-<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>
+</div>
-<li>Evan remat rewrite (coalesced intervals + folding of remat'd loads) and
-live intervals improvements.</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.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
+</div>
-<li>Christopher Lamb virtual register sub-register support, better truncates and
-extends on X86.</li>
+<div class="doc_text">
-<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>
+<p>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end.</p>
-<li>David Greene refactored the register allocator to split coalescing out from
-allocation, making coalescers pluggable.</li>
+<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>
-</ul>
+<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="targetspecific">Target Specific Improvements</a>
+<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>Bruno Cardoso Lopes contributed initial MIPS support.</li>
-<li>Bill Wendling added SSSE3 support.</li>
-<li>New Target independent if converter, ARM uses it so far</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.</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="llvmgccimprovements">llvm-gcc Improvements</a>
+<a name="optimizer">Optimizer Improvements</a>
</div>
<div class="doc_text">
-<p>New features include:
-</p>
+
+<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>
<ul>
-<li>Duncan and Anton exception handling in llvm-gcc 4.0/4.2</li>
-<li>Devang and Duncan: Bitfields, pragma pack</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>Tanya implemented support for __attribute__((noinline)) 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>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>Sheng Zhou and Christopher Lamb implemented alias analysis support for
-'restrict' arguments to functions.</li>
+<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
+<tt>memset</tt> is now more aggressive.</li>
-<li>Duncan contributed support for trampolines (pointers to nested functions),
-currently only supported on x86 target.</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>
-
+
+</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>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_subsection">
-<a name="coreimprovements">LLVM Core Improvements</a>
+<a name="x86specific">X86/X86-64 Specific Improvements</a>
</div>
<div class="doc_text">
-<p>New features include:
+<p>New target-specific features include:
</p>
<ul>
-<li>Neil Booth APFloat, foundation for long double support that will be wrapped
-up in 2.2. Dale contributed most of long double support, will be enabled in
-2.2.</li>
+<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>LLVM now provides an LLVMBuilder class which makes it significantly easier
-to create LLVM IR instructions.</li>
+<li>Support for Win64 was added. This includes code generation itself, JIT
+ support and necessary changes to llvm-gcc.</li>
-<li>Reid contributed support for intrinsics that take arbitrary integer typed
-arguments, Dan Gohman and Chandler extended it to support FP and vectors.</li>
-</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>
+
+<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 class="doc_subsection">
-<a name="otherimprovements">Other Improvements</a>
+<a name="targetspecific">Other Target Specific Improvements</a>
</div>
<div class="doc_text">
-<p>New features include:
+<p>New target-specific features include:
</p>
<ul>
-<li>BrainF frontend by Sterling Stein.</li>
+<li>The LLVM C backend now supports vector code.</li>
+</ul>
+
+</div>
-<li>David Green contributed a new --enable-expensive-checks configure option
-which enables STL checking, and fixed several bugs exposed by it.</li>
-</li>
+<!--=========================================================================-->
+<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>
<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>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
+<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
64-bit modes.</li>
-<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
+<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
support is available for native builds with Visual C++).</li>
-<li>Sun UltraSPARC workstations running Solaris 8.</li>
+<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 is disabled for this release.</li>
-<li>The MSIL backend is experimental.</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>
<ul>
<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
-processors, thumb program can crash or produces wrong
+processors, thumb programs can crash or produce wrong
results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
</li>
-<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
+<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
+ execute
programs compiled with LLVM. Please use more recent versions of QEMU.</li>
</ul>
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_text">
<ul>
-<li><a href="http://llvm.org/PR802">The C backend does not support inline
- assembly code</a>.</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="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>llvm-gcc4 does not currently support <a href="http://llvm.org/PR869">Link-Time
-Optimization</a> on most platforms "out-of-the-box". Please inquire on the
+<p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
+Optimization</a> on most platforms "out-of-the-box". Please inquire on the
llvmdev mailing list if you are interested.</p>
-</div>
-
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsubsection">
- Notes
-</div>
-
-<div class="doc_text">
-<ul>
-
-<li><p>"long double" is silently transformed by the front-end into "double". There
-is no support for floating point data types of any size other than 32 and 64
-bits.</p></li>
-
-<li><p>llvm-gcc does <b>not</b> support <tt>__builtin_apply</tt> yet.
- See <a href="http://gcc.gnu.org/onlinedocs/gcc/Constructing-Calls.html#Constructing%20Calls">Constructing Calls</a>: Dispatching a call to another function.</p>
-</li>
-
-<li><p>llvm-gcc <b>partially</b> supports these GCC extensions:</p>
- <ol>
- <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.<br>
- Nested functions are supported, but llvm-gcc does not support non-local
- gotos or taking the address of a nested function.</li>
-
- <li><a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function%20Attributes">Function Attributes</a>:
+<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>
- Declaring that functions have no side effects or that they can never
- return.<br>
-
- <b>Supported:</b> <tt>alias</tt>, <tt>always_inline</tt>, <tt>cdecl</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>pure</tt>, <tt>const</tt>, <tt>nothrow</tt>,
- <tt>malloc</tt>, <tt>no_instrument_function</tt></li>
- </ol>
-</li>
-
-<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>
- <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>
-
-</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>
+<p>If you run into GCC extensions which are not supported, please let us know.
+</p>
</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">
itself, Qt, Mozilla, etc.</p>
<ul>
-<li>llvm-gcc4 only has partial support for <a href="http://llvm.org/PR870">C++
-Exception Handling</a>, and it is not enabled by default.</li>
-
-<!-- NO EH Support!
-
-<li>Destructors for local objects are not always run when a <tt>longjmp</tt> is
- performed. In particular, destructors for objects in the <tt>longjmp</tt>ing
- function and in the <tt>setjmp</tt> receiver function may not be run.
- Objects in intervening stack frames will be destroyed, however (which is
- better than most compilers).</li>
-
-<li>The LLVM C++ front-end follows the <a
- href="http://www.codesourcery.com/cxx-abi">Itanium C++ ABI</a>.
- This document, which is not Itanium specific, specifies a standard for name
- mangling, class layout, v-table layout, RTTI formats, and other C++
- representation issues. Because we use this API, code generated by the LLVM
- compilers should be binary compatible with machine code generated by other
- Itanium ABI C++ compilers (such as G++, the Intel and HP compilers, etc).
- <i>However</i>, the exception handling mechanism used by llvm-gcc3 is very
- different from the model used in the Itanium ABI, so <b>exceptions will not
- interact correctly</b>. </li>
--->
+<li>Exception handling 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>
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <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>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>
<!-- *********************************************************************** -->
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