<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 2.2 Release Notes</title>
+ <title>LLVM 2.4 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.2 Release Notes</div>
-
+<div class="doc_title">LLVM 2.4 Release Notes</div>
+
<ol>
<li><a href="#intro">Introduction</a></li>
- <li><a href="#whatsnew">What's New?</a></li>
+ <li><a href="#subproj">Sub-project Status Update</a></li>
+ <li><a href="#whatsnew">What's New in LLVM?</a></li>
<li><a href="GettingStarted.html">Installation Instructions</a></li>
<li><a href="#portability">Portability and Supported Platforms</a></li>
- <li><a href="#knownproblems">Known Problems</a>
+ <li><a href="#knownproblems">Known Problems</a></li>
<li><a href="#additionalinfo">Additional Information</a></li>
</ol>
<div class="doc_author">
- <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
+ <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
</div>
-<h1><font color="red">THIS IS A WORK IN PROGRESS FOR THE LLVM 2.2
-RELEASE</font</h1>
-
<!-- *********************************************************************** -->
<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 2.2. 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>This document contains the release notes for the LLVM Compiler
+Infrastructure, release 2.4. Here we describe the status of LLVM, including
+major improvements from the previous release and significant 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
web site</a>. If you have questions or comments, the <a
-href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
-list</a> is a good place to send them.</p>
+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 a Subversion checkout or the
+<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
+current one. To see the release notes for a specific release, please see the
<a href="http://llvm.org/releases/">releases page</a>.</p>
</div>
+<!-- Unfinished features in 2.4:
+ Machine LICM
+ Machine Sinking
+ LegalizeDAGTypes
+ llc -enable-value-prop, propagation of value info (sign/zero ext info) from
+ one MBB to another
+ -->
+
+ <!-- for announcement email:
+ mention dev mtg
+ Xcode 3.1 and 3.1.1.
+ -->
+
<!-- *********************************************************************** -->
<div class="doc_section">
- <a name="whatsnew">What's New?</a>
+ <a name="subproj">Sub-project Status Update</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
-
-<p>This is the thirteenth public release of the LLVM Compiler Infrastructure.
-It includes many features and refinements from LLVM 2.1.</p>
+<p>
+The LLVM 2.4 distribution currently consists of code from the core LLVM
+repository (which roughly includes the LLVM optimizers, 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 <a href="#clang">Clang Project</a> and
+the <a href="#vmkit">VMKit Project</a>.
+</p>
</div>
-<!-- Unfinished features in 2.2:
- Index Set Splitting not enabled by default
- Machine LICM
- Machine Sinking
- LegalizeDAGTypes
- -->
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="deprecation">Deprecated features in LLVM 2.2</a>
+<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
</div>
<div class="doc_text">
-<p>This is the last LLVM release to support llvm-gcc 4.0, llvm-upgrade, and
-llvmc in its current form. llvm-gcc 4.0 has been replaced with llvm-gcc 4.2.
-llvm-upgrade is useful for upgrading llvm 1.9 files to llvm 2.x syntax, but you
-can always use an old release to do this. llvmc is currently mostly useless in
-llvm 2.2, and will be redesigned or removed in llvm 2.3.</p>
+<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>Clang, in conjunction with the <tt>ccc</tt> driver, is now usable as a
+replacement for gcc for building some small- to medium-sized C applications.
+Additionally, Clang now has code generation support for Objective-C on Mac OS X
+platform. Major highlights include:</p>
+
+<ul>
+ <li> Clang/ccc pass almost all of the LLVM test suite on Mac OS X and Linux
+on the 32-bit x86 architecture. This includes significant C
+applications such as <a href="http://www.sqlite.org">sqlite3</a>,
+<a href="http://www.lua.org">lua</a>, and
+<a href="http://www.clamav.net">Clam AntiVirus</a>. </li>
+
+ <li> Clang can build the majority of Objective-C examples shipped with the
+Mac OS X Developer Tools. </li>
+</ul>
+
+<p>Clang code generation still needs considerable testing and development,
+however. Some areas under active development include:</p>
+
+<ul>
+ <li> Improved support for C and Objective-C features, for example
+ variable-length arrays, va_arg, exception handling (Obj-C), and garbage
+ collection (Obj-C). </li>
+ <li> ABI compatibility, especially for platforms other than 32-bit
+ x86. </li>
+</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="frontends">llvm-gcc 4.0, llvm-gcc 4.2, and clang</a>
+<a name="clangsa">Clang Static Analyzer</a>
</div>
<div class="doc_text">
-<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 Clang project also includes an early stage static source code analysis
+tool for <a href="http://clang.llvm.org/StaticAnalysis.html">automatically
+finding bugs</a> in C and Objective-C programs. The tool performs a growing set
+of checks to find bugs that occur on a specific path within a program. Examples
+of bugs the tool finds include logic errors such as null dereferences,
+violations of various API rules, dead code, and potential memory leaks in
+Objective-C programs. Since its inception, public feedback on the tool has been
+extremely positive, and conservative estimates put the number of real bugs it
+has found in industrial-quality software on the order of thousands.</p>
+
+<p>The tool also provides a simple web GUI to inspect potential bugs found by
+the tool. While still early in development, the GUI illustrates some of the key
+features of Clang: accurate source location information, which is used by the
+GUI to highlight specific code expressions that relate to a bug (including those
+that span multiple lines); and built-in knowledge of macros, which is used to
+perform inline expansion of macros within the GUI itself.</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>
+<p>The set of checks performed by the static analyzer is gradually expanding,
+and future plans for the tool include full source-level inter-procedural
+analysis and deeper checks such as buffer overrun detection. There are many
+opportunities to extend and enhance the static analyzer, and anyone interested
+in working on this project is encouraged to get involved!</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="majorfeatures">Major New Features</a>
+<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
</div>
<div class="doc_text">
+<p>
+The <a href="http://vmkit.llvm.org/">VMKit project</a> 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>LLVM 2.2 includes several major new capabilities:</p>
+<p>Following LLVM 2.4, VMKit has its first release 0.24 that you can find on its
+<a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
+bug fixes, cleanup and new features. The major changes are:</p>
<ul>
-<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> Support for generics in the .Net virtual machine.</li>
+<li> Initial support for the Mono class libraries. </li>
+<li> Support for MacOSX/x86, following LLVM's support for exceptions in
+JIT on MacOSX/x86. </li>
+<li> A new vmkit driver: a program to run java or .net applications. The driver
+supports llvm command line arguments including the new "-fast" option. </li>
+<li> A new memory allocation scheme in the JVM that makes unloading a
+class loader very fast. </li>
+<li> VMKit now follows the LLVM Makefile machinery. </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>
+</ul>
+</div>
-<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>
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="whatsnew">What's New in LLVM?</a>
+</div>
+<!-- *********************************************************************** -->
-<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>
+<div class="doc_text">
+<p>This release includes a huge number of bug fixes, performance tweaks, and
+minor improvements. Some of the major improvements and new features are listed
+in this section.
+</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="coreimprovements">LLVM Core Improvements</a>
+<a name="majorfeatures">Major New Features</a>
</div>
<div class="doc_text">
-<p>New features include:
-</p>
+
+<p>LLVM 2.4 includes several major new capabilities:</p>
<ul>
-<li>Gordon contributed support for C and Ocaml Bindings for the basic LLVM IR
-construction routines as well as several other auxiliary APIs.</li>
+<li><p>The most visible end-user change in LLVM 2.4 is that it includes many
+optimizations and changes to make -O0 compile times much faster. You should see
+improvements in speed on the order of 30% (or more) than in LLVM 2.3. There are
+many pieces to this change described in more detail below. The speedups and new
+components can also be used for JIT compilers that want fast
+compilation.</p></li>
+
+<li><p>The biggest change to the LLVM IR is that Multiple Return Values (which
+were introduced in LLVM 2.3) have been generalized to full support for "First
+Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using
+structs and arrays as values in a function. This capability is mostly useful
+for front-end authors, who prefer to treat things like complex numbers, simple
+tuples, dope vectors, etc., as Value*'s instead of as a tuple of Value*'s or as
+memory values. Bitcode files from LLVM 2.3 will automatically migrate to the
+general representation.</p></li>
+
+<li><p>LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This
+target only has support for 8 bit registers, and a number of other crazy
+constraints. While the port is still in early development stages, it shows some
+interesting things you can do with LLVM.</p></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>
+</ul>
-<li>Devang added LLVMFoldingBuilder, a version of LLVMBuilder that implicitly
-simplifies the code as it is constructed.</li>
+</div>
-<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>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
+</div>
+
+<div class="doc_text">
-<li>Dan Gohman added support for vector sin, cos, and pow intrinsics.</li>
+<p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
+front-ends and driver with the LLVM optimizer and code generator. It currently
+includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
+<ul>
+<li>LLVM 2.4 supports the full set of atomic <tt>__sync_*</tt> builtins. LLVM
+2.3 only supported those used by OpenMP, but 2.4 supports them all. Note that
+while llvm-gcc supports all of these builtins, not all targets do. X86 support
+them all in both 32-bit and 64-bit mode and PowerPC supports them all except for
+the 64-bit operations when in 32-bit mode.</li>
+
+<li>llvm-gcc now supports an <tt>-flimited-precision</tt> option, which tells
+the compiler that it is okay to use low-precision approximations of certain libm
+functions (like <tt>exp</tt>, <tt>log</tt>, etc). This allows you to get high
+performance if you only need (say) 12-bits of precision.</li>
+
+<li>llvm-gcc now supports a C language extension known as "<a
+href="http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-August/002670.html">Blocks</a>".
+This feature is similar to nested functions and closures, but does not
+require stack trampolines (with most ABIs), and supports returning closures
+from functions that define them. Note that actually <em>using</em> Blocks
+requires a small runtime that is not included with llvm-gcc.</li>
+
+<li>llvm-gcc now supports a new <tt>-flto</tt> option. On systems that support
+transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and
+later) this allows the use of LTO with other optimization levels like -Os.
+Previously, LTO could only be used with -O4, which implied optimizations in
+-O3 that can increase code size.</li>
</ul>
-
+
</div>
+
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="codegen">Code Generator Improvements</a>
+<a name="coreimprovements">LLVM Core 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>
+<p>New features include:</p>
<ul>
+<li>A major change to the <tt>Use</tt> class landed, which shrank it by 25%. Since
+this is a pervasive part of the LLVM, it ended up reducing the memory use of
+LLVM IR in general by 15% for most programs.</li>
+
+<li>Values with no names are now pretty printed by <tt>llvm-dis</tt> more
+nicely. They now print as "<tt>%3 = add i32 %A, 4</tt>" instead of
+"<tt>add i32 %A, 4 ; <i32>:3</tt>", which makes it much easier to read.
+</li>
+
+<li>LLVM 2.4 includes some changes for better vector support. First, the shift
+operations (<tt>shl</tt>, <tt>ashr</tt>, and <tt>lshr</tt>) now all support
+vectors and do an element-by-element shift (shifts of the whole vector can be
+accomplished by bitcasting the vector to <tt><1 x i128></tt>, for example). Second,
+there is initial support in development for vector comparisons with the
+<tt><a href="LangRef.html#i_fcmp">fcmp</a>/<a href="LangRef.html#i_icmp">icmp</a></tt>
+instructions. These instructions compare two vectors and return a vector of
+<tt>i1</tt>'s for each result. Note that there is very little codegen support
+available for any of these IR features though.</li>
+
+<li>A new <tt>DebugInfoBuilder</tt> class is available, which makes it much
+easier for front-ends to create debug info descriptors, similar to the way that
+<tt>IRBuilder</tt> makes it easier to create LLVM IR.</li>
+
+<li>The <tt>IRBuilder</tt> class is now parameterized by a class responsible
+for constant folding. The default <tt>ConstantFolder</tt> class does target independent
+constant folding. The <tt>NoFolder</tt> class does no constant folding at all, which is
+useful when learning how LLVM works. The <tt>TargetFolder</tt> class folds the most,
+doing target dependent constant folding.</li>
+
+<li>LLVM now supports "function attributes", which allow us to separate return
+value attributes from function attributes. LLVM now supports attributes on a
+function itself, a return value, and its parameters. New supported function
+attributes include <tt>noinline/alwaysinline</tt> and the <tt>opt-size</tt> flag,
+which says the function should be optimized for code size.</li>
+
+<li>LLVM IR now directly represents "common" linkage, instead of
+ representing it as a form of weak linkage.</li>
+
+</ul>
+
+</div>
-<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>
+<!--=========================================================================-->
+<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, this
+release includes a few major enhancements and additions to the optimizers:</p>
-<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>
+<ul>
-<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>The Global Value Numbering (GVN) pass now does local Partial Redundancy
+Elimination (PRE) to eliminate some partially redundant expressions in cases
+where doing so won't grow code size.</li>
-<li>Evan added initial support for register coalescing of subregister
-references.</li>
+<li>LLVM 2.4 includes a new loop deletion pass (which removes output-free
+provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE)
+pass that no longer uses control dependence information. These changes speed up
+the optimizer and also prevent it from deleting output-free infinite
+loops.</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 new AddReadAttrs pass works out which functions are read-only or
+read-none (these correspond to 'pure' and 'const' in GCC) and marks them
+with the appropriate attribute.</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>LLVM 2.4 now includes a new SparsePropagation framework, which makes it
+trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using
+this interface means that you just define objects to represent your lattice
+values and the transfer functions that operate on them. It handles the
+mechanics of worklist processing, liveness tracking, handling PHI nodes,
+etc.</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 Loop Strength Reduction and induction variable optimization passes have
+several improvements to avoid inserting MAX expressions, to optimize simple
+floating point induction variables and to analyze trip counts of more
+loops.</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>Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were
+pulled out of the Instruction Combining pass and put into a new
+<tt>ValueTracking.h</tt> header, where they can be reused by other passes.</li>
+
+<li>The tail duplication pass has been removed from the standard optimizer
+sequence used by llvm-gcc. This pass still exists, but the benefits it once
+provided are now achieved by other passes.</li>
-<li>The MachineInstr, MachineOperand and TargetInstrDesc classes are simpler,
-more consistent, and better documented.</li>
</ul>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="optimizer">Optimizer Improvements</a>
+<a name="codegen">Code Generator Improvements</a>
</div>
<div class="doc_text">
-<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>
+<p>We have 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>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>
+<li>The target-independent code generator supports (and the X86 backend
+ currently implements) a new interface for "fast" instruction selection. This
+ interface is optimized to produce code as quickly as possible, sacrificing
+ code quality to do it. This is used by default at -O0 or when using
+ "llc -fast" on X86. It is straight-forward to add support for
+ other targets if faster -O0 compilation is desired.</li>
+
+<li>In addition to the new 'fast' instruction selection path, many existing
+ pieces of the code generator have been optimized in significant ways.
+ SelectionDAG's are now pool allocated and use better algorithms in many
+ places, the ".s" file printers now use <tt>raw_ostream</tt> to emit text much faster,
+ etc. The end result of these improvements is that the compiler also takes
+ substantially less time to generate code that is just as good (and often
+ better) than before.</li>
+
+<li>Each target has been split to separate the ".s" file printing logic from the
+ rest of the target. This enables JIT compilers that don't link in the
+ (somewhat large) code and data tables used for printing a ".s" file.</li>
+
+<li>The code generator now includes a "stack slot coloring" pass, which packs
+ together individual spilled values into common stack slots. This reduces
+ the size of stack frames with many spills, which tends to increase L1 cache
+ effectiveness.</li>
+
+<li>Various pieces of the register allocator (e.g. the coalescer and two-address
+ operation elimination pass) now know how to rematerialize trivial operations
+ to avoid copies and include several other optimizations.</li>
+
+<li>The <a href="CodeGenerator.html#selectiondag_process">graphs</a> produced by
+ the <tt>llc -view-*-dags</tt> options are now significantly prettier and
+ easier to read.</li>
+
+<li>LLVM 2.4 includes a new register allocator based on Partitioned Boolean
+ Quadratic Programming (PBQP). This register allocator is still in
+ development, but is very simple and clean.</li>
</ul>
</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>
+<li>Exception handling is supported by default on Linux/x86-64.</li>
+<li>Position Independent Code (PIC) is now supported on Linux/x86-64.</li>
+<li><tt>@llvm.frameaddress</tt> now supports getting the frame address of stack frames
+ > 0 on x86/x86-64.</li>
+<li>MIPS has improved a lot since last release, the most important changes
+ are: Little endian support, floating point support, allegrex core and
+ intrinsics support. O32 ABI is improved but isn't complete. The EABI
+ was implemented and is fully supported. We also have support for small
+ sections and gp_rel relocation for its access, a threshold in bytes can be
+ specified through command line.</li>
+<li>The PowerPC backend now supports trampolines.</li>
</ul>
-
+
</div>
+
<!--=========================================================================-->
<div class="doc_subsection">
<a name="otherimprovements">Other Improvements</a>
</p>
<ul>
-<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>
+<li><tt>llvmc2</tt> (the generic compiler driver) gained plugin
+ support. It is now easier to experiment with <tt>llvmc2</tt> and
+ build your own tools based on it.</li>
+
+<li>LLVM 2.4 includes a number of new generic algorithms and data structures,
+ including a scoped hash table, 'immutable' data structures, a simple
+ free-list manager, and a <tt>raw_ostream</tt> class.
+ The <tt>raw_ostream</tt> class and
+ <tt>format</tt> allow for efficient file output, and various pieces of LLVM
+ have switched over to use it. The eventual goal is to eliminate
+ use of <tt>std::ostream</tt> in favor of it.</li>
+
+<li>LLVM 2.4 includes an optional build system based on CMake. It
+ still is in its early stages but can be useful for Visual C++
+ users who can not use the Visual Studio IDE.</li>
+
</ul>
-
+
+</div>
+
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="changes">Major Changes and Removed Features</a>
+</div>
+
+<div class="doc_text">
+
+<p>If you're already an LLVM user or developer with out-of-tree changes based
+on LLVM 2.3, this section lists some "gotchas" that you may run into upgrading
+from the previous release.</p>
+
+<ul>
+
+<li>The LLVM IR generated by llvm-gcc no longer names all instructions. This
+ makes it run faster, but may be more confusing to some people. If you
+ prefer to have names, the '<tt>opt -instnamer</tt>' pass will add names to
+ all instructions.</li>
+
+<li>The LoadVN and GCSE passes have been removed from the tree. They are
+ obsolete and have been replaced with the GVN and MemoryDependence passes.
+ </li>
+</ul>
+
+
+<p>In addition, many APIs have changed in this release. Some of the major LLVM
+API changes are:</p>
+
+<ul>
+
+<li>Now, function attributes and return value attributes are managed
+separately. Interface exported by <tt>ParameterAttributes.h</tt> header is now
+exported by <tt>Attributes.h</tt> header. The new attributes interface changes are:
+<ul>
+<li><tt>getParamAttrs</tt> method is now replaced by
+<tt>getParamAttributes</tt>, <tt>getRetAttributes</tt> and
+<tt>getFnAttributes</tt> methods.</li>
+<li> Return value attributes are stored at index 0. Function attributes are
+stored at index ~0U. Parameter attributes are stored at index that matches
+parameter number.</li>
+<li> <tt>ParamAttr</tt> namespace is now renamed as <tt>Attribute</tt>.</li>
+<li> The name of the class that manages reference count of opaque
+attributes is changed from <tt>PAListPtr</tt> to <tt>AttrListPtr</tt>.</li>
+<li> <tt>ParamAttrsWithIndex</tt> is now renamed as <tt>AttributeWithIndex</tt>.
+</li>
+</ul>
+</li>
+
+<li>The <tt>DbgStopPointInst</tt> methods <tt>getDirectory</tt> and
+<tt>getFileName</tt> now return <tt>Value*</tt> instead of strings. These can be
+converted to strings using <tt>llvm::GetConstantStringInfo</tt> defined via
+"<tt>llvm/Analysis/ValueTracking.h</tt>".</li>
+
+<li>The APIs to create various instructions have changed from lower case
+ "create" methods to upper case "Create" methods (e.g.
+ <tt>BinaryOperator::create</tt>). LLVM 2.4 includes both cases, but the
+ lower case ones are removed in mainline (2.5 and later), please migrate.</li>
+
+<li>Various header files like "<tt>llvm/ADT/iterator</tt>" were given a ".h" suffix.
+ Change your code to #include "<tt>llvm/ADT/iterator.h</tt>" instead.</li>
+
+<li>The <tt>getresult</tt> instruction has been removed and replaced with the
+ <tt>extractvalue</tt> instruction. This is part of support for first class
+ aggregates.</li>
+
+<li>In the code generator, many <tt>MachineOperand</tt> predicates were renamed to be
+ shorter (e.g. <tt>isFrameIndex()</tt> -> <tt>isFI()</tt>),
+ <tt>SDOperand</tt> was renamed to <tt>SDValue</tt> (and the "<tt>Val</tt>"
+ member was changed to be the <tt>getNode()</tt> accessor), and the
+ <tt>MVT::ValueType</tt> enum has been replaced with an "<tt>MVT</tt>"
+ struct. The <tt>getSignExtended</tt> and <tt>getValue</tt> methods in the
+ ConstantSDNode class were renamed to <tt>getSExtValue</tt> and
+ <tt>getZExtValue</tt> respectively, to be more consistent with
+ the <tt>ConstantInt</tt> class.</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
- (and probably other unix-like systems).</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 (IA32, X86-64, AMD64, EMT-64) 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 10.3 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>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>
<div class="doc_text">
-<p>This section contains all known problems with the LLVM system, listed by
-component. As new problems are discovered, they will be added to these
-sections. If you run into a problem, please check the <a
+<p>This section contains significant known problems with the LLVM system,
+listed by component. If you run into a problem, please check the <a
href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
there isn't already one.</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 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
+<li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 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>
<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 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>
+ <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> due to lack of support for the
+ 'u' inline assembly constraint and X87 floating point inline assembly.</li>
+ <li>The X86-64 backend does not yet support the LLVM IR instruction
+ <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
+ argument constructs on X86-64 by lowering them manually.</li>
</ul>
</div>
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>
</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="mips-be">Known problems with the MIPS back-end</a>
+</div>
+
+<div class="doc_text">
+
+<ul>
+<li>The O32 ABI is not fully supported.</li>
+<li>64-bit MIPS targets are not supported yet.</li>
+</ul>
+
+</div>
+
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="alpha-be">Known problems with the Alpha back-end</a>
<div class="doc_text">
<ul>
-
-<li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
-made where the argument is not 16-byte aligned, as required on IA64. (Strictly
-speaking this is not a bug in the IA64 back-end; it will also be encountered
-when building C++ programs using the C back-end.)</li>
-
-<li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
-ABI compliant layout of v-tables</a>. In particular, it just stores function
-pointers instead of function descriptors in the vtable. This bug prevents
-mixing C++ code compiled with LLVM with C++ objects compiled by other C++
-compilers.</li>
-
-<li>There are a few ABI violations which will lead to problems when mixing LLVM
-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>The Itanium backend has bitrotted somewhat.</li>
+<li>The Itanium backend is highly experimental, and has a number of known
+ issues. We are looking for a maintainer for the Itanium backend. If you
+ are interested, please contact the LLVMdev mailing list.</li>
</ul>
</div>
<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/PR1126">The C backend does not support vectors
- yet</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>
+ 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_subsubsection">Bugs</div>
-
<div class="doc_text">
<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>
+LLVMdev mailing list if you are interested.</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>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><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.
- 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>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>
-
- <b>Ignored:</b> <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>
+<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. Currently
+ only Linux and Darwin targets are supported (both 32 and 64 bit).</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>
+ <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
</div>
<div class="doc_text">
-
-<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 only works well on the X86 and PowerPC targets.</li>
+<li>Fortran support generally works, but there are still several unresolved bugs
+ in Bugzilla. Please see the tools/gfortran component for details.</li>
+
+<li>The Fortran front-end currently does not build on Darwin (without tweaks)
+ due to unresolved dependencies on the C front-end.</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, <a href="http://llvm.org/PR2010">c393010</a>
+and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
+(c380004 also fails with gcc-4.2 mainline).</li>
+<li>Some gcc specific Ada tests continue to crash the compiler.</li>
+<li>The -E binder option (exception backtraces)
+<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
+crashing if an exception is raised. Workaround: do not use -E.</li>
+<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
+or finish at a non-byte offset</a> in a record. Workaround: do not pack records
+or use representation clauses that result in a field of a non-discrete type
+starting or finishing in the middle of a byte.</li>
+<li>The <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">
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