+
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 2.0 Release Notes</title>
+ <title>LLVM 2.3 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.0 Release Notes</div>
+<div class="doc_title">LLVM 2.3 Release Notes</div>
<ol>
<li><a href="#intro">Introduction</a></li>
+ <li><a href="#changes">Major Changes and Sub-project Status</a></li>
<li><a href="#whatsnew">What's New?</a></li>
<li><a href="GettingStarted.html">Installation Instructions</a></li>
<li><a href="#portability">Portability and Supported Platforms</a></li>
<p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
</div>
+<!-- Done through Week-of-Mon-20080324.txt -->
+
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="intro">Introduction</a>
<div class="doc_text">
<p>This document contains the release notes for the LLVM compiler
-infrastructure, release 2.0. Here we describe the status of LLVM, including any
-known problems and major improvements from the previous release. All LLVM
+infrastructure, release 2.3. Here we describe the status of LLVM, including
+major improvements from the previous release and any known problems. All LLVM
releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
-releases web site</a>.
+releases web site</a>.</p>
<p>For more information about LLVM, including information about the latest
release, please check out the <a href="http://llvm.org/">main LLVM
href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
list</a> is a good place to send them.</p>
-<p>Note that if you are reading this file from CVS or the main LLVM web page,
-this document applies to the <i>next</i> release, not the current one. To see
-the release notes for the current or previous releases, see the <a
-href="http://llvm.org/releases/">releases page</a>.</p>
+<p>Note that if you are reading this file from a Subversion checkout or the
+main LLVM web page, this document applies to the <i>next</i> release, not the
+current one. To see the release notes for a specific releases, please see the
+<a href="http://llvm.org/releases/">releases page</a>.</p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
- <a name="whatsnew">What's New?</a>
+ <a name="changes">Major Changes and Sub-project Status</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
-<p>This is the eleventh public release of the LLVM Compiler Infrastructure.
-Being the first major release since 1.0, this release is different in several
-ways from our previous releases:</p>
-
-<ol>
-<li>We took this as an opportunity to
-break backwards compatibility with the LLVM 1.x bytecode and .ll file format.
-If you have LLVM 1.9 .ll files that you would like to upgrade to LLVM 2.x, we
-recommend the use of the stand alone <a href="#llvm-upgrade">llvm-upgrade</a>
-tool (which is included with 2.0). We intend to keep compatibility with .ll
-and .bc formats within the 2.x release series, like we did within the 1.x
-series.</li>
-<li>There are several significant change to the LLVM IR and internal APIs, such
- as a major overhaul of the type system, the completely new bitcode file
- format, etc.</li>
-<li>We designed the release around a 6 month release cycle instead of the usual
- 3-month cycle. This gave us extra time to develop and test some of the
- more invasive features in this release.</li>
-<li>LLVM 2.0 no longer supports the llvm-gcc3 front-end.</li>
-</ol>
-
-<p>Note that while this is a major version bump, this release has been
- extensively tested on a wide range of software. It is easy to say that this
- is our best release yet, in terms of both features and correctness.</p>
+<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="newfeatures">New Features in LLVM 2.0</a>
+<a name="changes">Major Changes in LLVM 2.3</a>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="majorchanges">Major Changes</a></div>
<div class="doc_text">
-<p>blah
-</p>
-
-<ul>
-
-<li>llvm-gcc3 is now officially unsupported. Users are required to
- upgrade to llvm-gcc4. llvm-gcc4 includes many features over
- llvm-gcc3, is faster, and is much easier to build.</li>
-<li>Integer types are now completely signless. This means that we
- have types like i8/i16/i32 instead of ubyte/sbyte/short/ushort/int
- etc. LLVM operations that depend on sign have been split up into
- separate instructions (<a href="http://llvm.org/PR950">PR950</a>).</li>
+<p>LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with
+ llvm-gcc 4.2.</p>
-<li>Arbitrary bitwidth integers (e.g. i13, i36, i42, etc) are now
- supported in the LLVM IR and optimizations. However, neither llvm-gcc nor
- the native code generators support non-standard width integers
- (<a href="http://llvm.org/PR1043">PR1043</a>).</li>
+<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>
-<li>'type planes' have been removed (<a href="http://llvm.org/PR411">PR411</a>).
- It is no longer possible to have two values with the same name in the
- same symbol table. This simplifies LLVM internals, allowing significant
- speedups.</li>
+<p>The <tt>llvm2cpp</tt> tool has been folded into llc, use
+ <tt>llc -march=cpp</tt> instead of <tt>llvm2cpp</tt>.</p>
-<li>Global variables and functions in .ll files are now prefixed with
- @ instead of % (<a href="http://llvm.org/PR645">PR645</a>).</li>
+<p>LLVM API Changes:</p>
-<li>The LLVM 1.x "bytecode" format has been replaced with a
- completely new binary representation, named 'bitcode'. Because we
- plan to maintain binary compatibility between LLVM 2.x ".bc" files,
- this is an important change to get right. Bitcode brings a number of
- advantages to the LLVM over the old bytecode format. It is denser
- (files are smaller), more extensible, requires less memory to read,
- is easier to keep backwards compatible (so LLVM 2.5 will read 2.0 .bc
- files), and has many other nice features.</li>
-
-<li>Support was added for alignment values on load and store
- instructions (<a href="http://www.llvm.org/PR400">PR400</a>). This
- allows the IR to express loads that are not
- sufficiently aligned (e.g. due to pragma packed) or to capture extra
- alignment information. </li>
-
-<li>LLVM now has a new MSIL backend. llc - march=msil will now turn LLVM
- into MSIL (".net") bytecode. This is still fairly early development
- with a number of limitations.</li>
-
-<li>Support has been added for 'protected visibility' in ELF.</li>
-
-<li>Thread Local Storage with the __thread keyword was implemented along
- with added codegen support for Linux on X86 and ARM.</li>
-
-<li>ELF symbol aliases supported has been added.</li>
-
-<li>Added support for 'polymorphic intrinsics', allowing things like
- llvm.ctpop to work on arbitrary width integers.</li>
+<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
+ <a href="http://llvm.org/doxygen/classllvm_1_1IRBuilder.html">IRBuilder</a>.
+ </li>
+<li>MRegisterInfo was renamed to
+ <a href="http://llvm.org/doxygen/classllvm_1_1TargetRegisterInfo.html">
+ TargetRegisterInfo</a>.</li>
+<li>The MappedFile class is gone, please use
+ <a href="http://llvm.org/doxygen/classllvm_1_1MemoryBuffer.html">
+ MemoryBuffer</a> 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>
+<li>The ConstantFP::get method that uses APFloat now takes one argument
+ instead of two. The type argument has been removed, and the type is
+ now inferred from the size of the given APFloat value.</li>
</ul>
-
</div>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="otherprojects">Other LLVM Sub-Projects</a>
+</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="llvmgccfeatures">llvm-gcc
-Improvements</a></div>
<div class="doc_text">
-<p>New features include:
+<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>
-<ul>
-<li>Precompiled Headers (PCH) support has been implemented.</li>
-
-<li>Support for external weak linkage and hidden visibility has been added.</li>
-
-<li>Packed structure types are now supported , which allows LLVM to express
- unaligned data more naturally.</li>
-
-<li>Inline assembly support has been improved and many bugs were fixed.
- The two large missing features are support for 80-bit floating point stack
- registers on X86 (<a href="http://llvm.org/PR879">PR879</a>), and support for inline asm in the C backend (<a href="http://llvm.org/PR802">PR802</a>).</li>
-
-<li>Ada support, such as nested functions, has been improved.</li>
-
-<li>Tracking function parameter/result attributes is now possible.</li>
-
-<li>Its is now easier to configure llvm-gcc for linux.</li>
-
-<li>Many enhancements have been added, such as improvements to NON_LVALUE_EXPR,
- arrays with non-zero base, structs with variable sized fields,
- VIEW_CONVERT_EXPR, CEIL_DIV_EXPR, and many other things.</li>
-
-<li>Improved "attribute packed" support in the CFE, and handle many
- other obscure struct layout cases correctly.</li>
-
-</ul>
-
+<!--=========================================================================-->
+<div class="doc_subsubsection">
+<a name="vmkit">vmkit</a>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="optimizer">Optimizer
-Improvements</a></div>
<div class="doc_text">
-<p>New features include:
+<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>
-<ul>
-<li>The pass manager has been entirely rewritten, making it significantly
- smaller, simpler, and more extensible. Support has been added to run
- FunctionPasses interlaced with CallGraphSCCPasses.</li>
+<div class="doc_code">
+<pre>svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit</pre>
+</div>
-<li>The -scalarrepl pass can now promote unions containing FP values into
- a register, it can also handle unions of vectors of the same size.</li>
+</div>
-<li>The predicate simplifier pass has been improved, making it able to do
- simple value range propagation and eliminate more conditionals.</li>
+<!--=========================================================================-->
+<div class="doc_subsubsection">
+<a name="clang">Clang</a>
+</div>
-<li>There is a new new LoopPass class. The passmanager has been
- modified to support it, and all existing loop xforms have been
- converted to use it. </li>
+<div class="doc_text">
-<li>There is a new loop rotation pass, which converts "for loops" into
- "do/while loops", where the condition is at the bottom of the loop.</li>
+<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>
-<li>ModulePasses may now use the result of FunctionPasses.</li>
+<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 focuses on automatically finding
+bugs in C and Objective-C code.</p>
-<li>The [Post]DominatorSet classes have been removed from LLVM and clients switched to use the far-more-efficient ETForest class instead. </li>
+</div>
-<li>The ImmediateDominator class has also been removed, and clients have been switched to use DominatorTree instead.</li>
-</ul>
-
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="whatsnew">What's New?</a>
</div>
-
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="codegen">Code
-Generator Enhancements</a></div>
+<!-- *********************************************************************** -->
<div class="doc_text">
-<p>
-New features include:
-</p>
-<ul>
-<li>Support for Zero-cost DWARF exception handling has been added. It is mostly
- complete and just in need of continued bug fixes and optimizations at
- this point.</li>
+<p>LLVM 2.3 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>
-<li>Progress has been made on a direct Mach-o .o file writer. Many small
- apps work, but it is not quite complete yet.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="majorfeatures">Major New Features</a>
+</div>
-<li>Support was added for software floating point routines.</li>
+<div class="doc_text">
-<li>DWARF debug information generation has been improved. LLVM now passes
- most of the GDB testsuite on MacOS and debug info is more dense.</li>
+<p>LLVM 2.3 includes several major new capabilities:</p>
-<li>A new register scavenger has been implemented, which is useful for
- finding free registers after register allocation. This is useful when
- rewriting frame references on RISC targets, for example.</li>
+<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>
+</li>
-<li>Heuristics have been added to avoid coalescing vregs with very large live
- ranges to physregs.</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>Support now exists for very simple (but still very useful)
- rematerialization the register allocator, enough to move
- instructions like "load immediate" and constant pool loads.</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>Significantly improved 'switch' lowering, improving codegen for
- sparse switches that have dense subregions, and implemented support
- for the shift/and trick.</li>
+</ul>
-<li>The code generator now has more accurate and general hooks for
- describing addressing modes ("isLegalAddressingMode") to
- optimizations like loop strength reduction and code sinking.</li>
+</div>
-<li>The Loop Strength Reduction pass has been improved, and support added
- for sinking expressions across blocks to reduce register pressure.</li>
-<li>Added support for tracking physreg sub-registers and super-registers
- in the code generator, as well as extensive register
- allocator changes to track them.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
+</div>
-<li>There is initial support for virtreg sub-registers
- (<a href="http://llvm.org/PR1350">PR1350</a>).</li>
+<div class="doc_text">
-</ul>
+<p>LLVM 2.3 fully supports the llvm-gcc 4.2 front-end, and includes support
+for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
-<p>In addition, the LLVM target description format has itself been extended in
- several ways:</p>
-
+<p>
<ul>
-<li>Extended TargetData to support better target parameterization in
- the .ll/.bc files, eliminating the 'pointersize/endianness' attributes
- in the files (<a href="http://llvm.org/PR761">PR761</a>).</li>
+<li>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.</li>
-<li>TargetData was generalized for finer grained alignment handling,
- handling of vector alignment, and handling of preferred alignment</li>
+<li>Fortran <tt>EQUIVALENCE</tt>s are now supported by the gfortran
+front-end.</li>
-<li>LLVM now supports describing target calling conventions
- explicitly in .td files, reducing the amount of C++ code that needs
- to be written for a port.</li>
+<li>llvm-gcc 4.2 includes many other fixes which improve conformance with the
+relevant parts of the GCC testsuite.</li>
</ul>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="specifictargets">Target-Specific
-Improvements</a></div>
-<div class="doc_text">
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="coreimprovements">LLVM Core Improvements</a>
+</div>
-<p>X86-Specific Code Generator Enhancements:
+<div class="doc_text">
+<p>New features include:
</p>
<ul>
-<li>The scheduler was improved to better reduce register pressure on
- X86 and other targets that are register pressure sensitive</li>
-<li>Linux/x86-64 support has been improved.</li>
-<li>PIC support for linux/x86 has been added.</li>
-<li>Support now exists for the GCC regparm attribute, and code in the X86
- backend to respect it.</li>
-<li>Various improvements have been made for the X86-64 JIT, allowing it to
- generate code in the large code model</li>
-<li>LLVM now supports inline asm with multiple constraint letters per operand
- (like "ri") which is common in X86 inline asms.</li>
-<li>Early support has been added for X86 inline asm in the C backend.</li>
-<li>Added support for the X86 MMX instruction set.</li>
+<li>LLVM IR now directly represents "common" linkage, instead of representing it
+as a form of weak linkage.</li>
+<li>LLVM IR now has support for atomic operations, and this functionality can be
+accessed through the llvm-gcc "<tt>__sync_synchronize</tt>",
+"<tt>__sync_val_compare_and_swap</tt>", and related builtins. Support for
+atomics are available in the Alpha, X86, X86-64, and PowerPC backends.</li>
+
+<li>The C and Ocaml bindings have extended to cover pass managers, several
+transformation passes, iteration over the LLVM IR, target data, and parameter
+attribute lists.</li>
</ul>
+
+</div>
-<p>ARM-Specific Code Generator Enhancements:
-</p>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="optimizer">Optimizer Improvements</a>
+</div>
+
+<div class="doc_text">
+
+<p>In addition to a huge array of bug fixes and minor performance tweaks, the
+LLVM 2.3 optimizers support a few major enhancements:</p>
<ul>
-<li>Several improvements have been made to the ARM backend, including basic
- inline asm support, weak linkage support, static ctor/dtor support and
- many bug fixes.</li>
-<li>There are major enhancements to the ARM backend, including support for ARM
- v4-v6, vfp support, soft float, pre/postinc support, load/store multiple
- generation, constant pool entry motion (to support large functions),
- and enhancements to ARM constant island pass.
- </li>
-<li>Added support for Thumb code generation (an ARM subtarget).</li>
-<li>More aggressive size analysis for ARM inline asm strings was
- implemented.</li>
-</ul>
+<li><p>Loop index set splitting on by default.
+This transformation hoists conditions from loop bodies and reduces a loop's
+iteration space to improve performance. For example,</p>
+
+<div class="doc_code">
+<pre>
+for (i = LB; i < UB; ++i)
+ if (i <= NV)
+ LOOP_BODY
+</pre>
</div>
-<p>Other Target-Specific Code Generator Enhancements:
+<p>is transformed into:</p>
+
+<p><div class="doc_code">
+<pre>
+NUB = min(NV+1, UB)
+for (i = LB; i < NUB; ++i)
+ LOOP_BODY
+</pre>
+</div>
</p>
+</li>
-<ul>
-<li>The PowerPC 64 JIT now supports addressing code loaded above the 2G
- boundary.</li>
+<li>LLVM now includes a new <tt>memcpy</tt> optimization pass which removes
+dead <tt>memcpy</tt> calls, unneeded copies of aggregates, and performs
+return slot optimization. The LLVM optimizer now notices long sequences of
+consecutive stores and merges them into <tt>memcpy</tt>'s where profitable.</li>
+
+<li>Alignment detection for vector memory references and for <tt>memcpy</tt> and
+<tt>memset</tt> is now more aggressive.</li>
+
+<li>The Aggressive Dead Code Elimination (ADCE) optimization has been rewritten
+to make it both faster and safer in the presence of code containing infinite
+loops. Some of its prior functionality has been factored out into the loop
+deletion pass, which <em>is</em> safe for infinite loops. The new ADCE pass is
+no longer based on control dependence, making it run faster.</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>
-<li>Improved support for the Linux/ppc ABI and the linux/ppc JIT is fully
- functional now. llvm-gcc and static compilation are not fully supported
- yet though.</li>
+<li>Several optimizations have been sped up, leading to faster code generation
+ with the same code quality.</li>
+
+</ul>
-<li>Many bugs fixed for PowerPC 64.</li>
+</div>
-<li>Support was added for the ARM AAPCS and EABI ABIs and PIC codegen on
- arm/linux.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="codegen">Code Generator Improvements</a>
+</div>
-<li>Several bugs in DWARF debug emission on linux and cygwin/mingw were fixed.
- Debugging basically works on these targets now.</li>
+<div class="doc_text">
-<li>Support has been added for the X86-64 large code model to the JIT,
- which is useful if JIT'd function bodies are more than 2G away from
- library functions.</li>
+<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>
-<li>Several bugs were fixed for DWARF debug info generation on arm/linux.</li>
+<ul>
+<li>The code generator now has support for carrying information about memory
+ references throughout the entire code generation process, via the
+ <a href="http://llvm.org/doxygen/classllvm_1_1MachineMemOperand.html">
+ MachineMemOperand</a> class. In the future this will be used to improve
+ both pre-pass and post-pass scheduling, and to improve compiler-debugging
+ output.</li>
+
+<li>The target-independent code generator infrastructure now uses LLVM's
+ <a href="http://llvm.org/doxygen/classllvm_1_1APInt.html">APInt</a>
+ class to handle integer values, which allows it to support integer types
+ larger than 64 bits (for example i128). 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, particularly in the instruction selection phase, register
+ allocation, scheduling, and tail merging/jump threading.</li>
+<li>LLVM 2.3 includes 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 <a
+ href="CodeGenerator.html#tailcallopt">tail calls</a> on X86/32 and initial
+ support for tail calls on PowerPC 32 (it may also work on PowerPC 64 but is
+ not thoroughly tested).</li>
</ul>
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="other">Other Improvements</a></div>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="x86specific">X86/X86-64 Specific Improvements</a>
+</div>
+
<div class="doc_text">
+<p>New target-specific features include:
+</p>
-<p>This release includes many other improvements, including
-performance work, specifically designed to tune datastructure
-usage. This makes several critical components faster.</p>
+<ul>
+<li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the
+ area of passing and returning structures by value. llvm-gcc compiled code
+ now interoperates very well on X86-64 systems with other compilers.</li>
-<p>More specific changes include:</p>
+<li>Support for Win64 was added. This includes code generation itself, JIT
+ support, and necessary changes to llvm-gcc.</li>
-<ul>
-<li>LLVM no longer relies on static destructors to shut itself down. Instead,
- it lazily initializes itself and shuts down when llvm_shutdown() is
- explicitly called.</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>LLVM now has significantly fewer static constructors, reducing startup time.
- </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. This is important because most X86 ABIs require return values
+ to be on the X87 Floating Point stack, but most CPUs prefer computation in
+ the SSE units.</li>
+
+<li>The X86 backend supports stack realignment, which is particularly useful for
+ vector code on OS's without 16-byte aligned stacks, such as Linux and
+ Windows.</li>
-<li>Several classes have been refactored to reduce the amount of code that
- gets linked into apps that use the JIT.</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>Construction of intrinsic function declarations has been simplified.</li>
+<li>Trampolines (taking the address of a nested function) now work on
+ Linux/X86-64.</li>
-<li>The llvm-upgrade tool now exists. This migrates LLVM 1.9 .ll files to
- LLVM 2.0 syntax.</li>
+<li><tt>__builtin_prefetch</tt> is now compiled into the appropriate prefetch
+ instructions instead of being ignored.</li>
-<li>The gccas/gccld tools have been removed.</li>
+<li>128-bit integers are now supported on X86-64 targets. This can be used
+ through <tt>__attribute__((TImode))</tt> in llvm-gcc.</li>
-<li>Support has been added to llvm-test for running on low-memory
- or slow machines (make SMALL_PROBLEM_SIZE=1).</li>
+<li>The register allocator can now rematerialize PIC-base computations, which is
+ an important optimization for register use.</li>
-<li>llvm-test is now more portable and should build with MS Visual Studio.</li>
+<li>The "t" and "f" inline assembly constraints for the X87 floating point stack
+ now work. However, the "u" constraint is still not fully supported.</li>
</ul>
+
</div>
-<!--_________________________________________________________________________-->
-<div class="doc_subsubsection"><a name="apichanges">API Changes</a></div>
-<div class="doc_text">
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="targetspecific">Other Target Specific Improvements</a>
+</div>
-<p>LLVM 2.0 contains a revamp of the type system and several other significant
-internal changes. If you are programming to the C++ API, be aware of the
-following major changes:</p>
+<div class="doc_text">
+<p>New target-specific features include:
+</p>
<ul>
-<li>Pass registration is slightly different in LLVM 2.0 (you now needs an
- intptr_t in your constructor), as explained in the <a
- href="WritingAnLLVMPass.html#basiccode">Writing an LLVM Pass</a>
- document.</li>
-
-<li><tt>ConstantBool</tt>, <tt>ConstantIntegral</tt> and <tt>ConstantInt</tt>
- classes have been merged together, we now just have
- <tt>ConstantInt</tt>.</li>
-
-<li><tt>Type::IntTy</tt>, <tt>Type::UIntTy</tt>, <tt>Type::SByteTy</tt>, ... are
- replaced by <tt>Type::Int8Ty</tt>, <tt>Type::Int16Ty</tt>, etc. LLVM types
- have always corresponded to fixed size types
- (e.g. long was always 64-bits), but the type system no longer includes
- information about the sign of the type.</li>
-
-<li>Several classes (<tt>CallInst</tt>, <tt>GetElementPtrInst</tt>,
- <tt>ConstantArray</tt>, etc), that once took <tt>std::vector</tt> as
- arguments now take ranges instead. For example, you can create a
- <tt>GetElementPtrInst</tt> with code like:
-
- <pre>
- Value *Ops[] = { Op1, Op2, Op3 };
- GEP = new GetElementPtrInst(BasePtr, Ops, 3);
- </pre>
-
- This avoids creation of a temporary vector (and a call to malloc/free). If
- you have an std::vector, use code like this:
- <pre>
- std::vector<Value*> Ops = ...;
- GEP = new GetElementPtrInst(BasePtr, &Ops[0], Ops.size());
- </pre>
+<li>The LLVM C backend now supports vector code.</li>
+<li>The Cell SPU backend includes a number of improvements. It generates better
+ code and its stability/completeness is improving.</li>
+</ul>
+
+</div>
- </li>
-
-<li>CastInst is now abstract and its functionality is split into several parts,
- one for each of the <a href="LangRef.html#convertops">new cast
- instructions</a>.</li>
-<li><tt>Instruction::getNext()/getPrev()</tt> are now private (along with
- <tt>BasicBlock::getNext</tt>, etc), for efficiency reasons (they are now no
- longer just simple pointers). Please use BasicBlock::iterator, etc instead.
-</li>
-<li><tt>Module::getNamedFunction()</tt> is now called
- <tt>Module::getFunction()</tt>.</li>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="otherimprovements">Other Improvements</a>
+</div>
+
+<div class="doc_text">
+<p>New features include:
+</p>
-<li><tt>SymbolTable.h</tt> has been split into <tt>ValueSymbolTable.h</tt> and
-<tt>TypeSymbolTable.h</tt>.</li>
+<ul>
+<li>LLVM now builds with GCC 4.3.</li>
+<li>Bugpoint now supports running custom scripts (with the <tt>-run-custom</tt>
+ option) to determine how to execute the command and whether it is making
+ forward process.</li>
</ul>
+
</div>
-
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="portability">Portability and Supported Platforms</a>
<p>LLVM is known to work on the following platforms:</p>
<ul>
- <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
+<li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
(and probably other unix-like systems).</li>
-<li>Intel and AMD machines running on Win32 using MinGW libraries (native)</li>
-<li>Sun UltraSPARC workstations running Solaris 8.</li>
+<li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
+ 64-bit modes.</li>
+<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
support is available for native builds with Visual C++).</li>
-<li>PowerPC and X86-based Mac OS X systems, running 10.2 and above in 32-bit and
- 64-bit modes.</li>
+<li>Sun UltraSPARC workstations running Solaris 10.</li>
<li>Alpha-based machines running Debian GNU/Linux.</li>
-<li>Itanium-based machines running Linux and HP-UX.</li>
+<li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
</ul>
-<p>The core LLVM infrastructure uses
-<a href="http://www.gnu.org/software/autoconf/">GNU autoconf</a> to adapt itself
+<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
to the machine and operating system on which it is built. However, minor
porting may be required to get LLVM to work on new platforms. We welcome your
portability patches and reports of successful builds or error messages.</p>
be broken or unreliable, or are in early development. These components should
not be relied on, and bugs should not be filed against them, but they may be
useful to some people. In particular, if you would like to work on one of these
-components, please contact us on the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
+components, please contact us on the <a
+href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
<ul>
-<li>The <tt>-cee</tt> pass is known to be buggy, and may be removed in in a
- future release.</li>
-<li>C++ EH support</li>
-<li>The IA64 code generator is experimental.</li>
-<li>The Alpha JIT is experimental.</li>
-<li>"<tt>-filetype=asm</tt>" (the default) is the only supported value for the
- <tt>-filetype</tt> llc option.</li>
+<li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
+<li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
+ value for this option.</li>
</ul>
</div>
<div class="doc_text">
<ul>
-<li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
- assembly that uses the X86 floating point stack</a>.</li>
+ <li>The X86 backend does not yet support
+ all <a href="http://llvm.org/PR879">inline assembly that uses the X86
+ floating point stack</a>. It supports the 'f' and 't' constraints, but not
+ 'u'.</li>
+ <li>The X86 backend generates inefficient floating point code when configured
+ to generate code for systems that don't have SSE2.</li>
+ <li>Win64 code generation wasn't widely tested. Everything should work, but we
+ expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
+ currently due
+ to <a href="http://llvm.org/PR2255">several</a>
+ <a href="http://llvm.org/PR2257">bugs</a> 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 position-independent code (PIC)
+ generation on Linux targets.</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>
<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 Dwarf debugging informations.
+compilation, and lacks support for debug information.</li>
</ul>
</div>
<div class="doc_text">
<ul>
-<li>The Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
-processors, any thumb program compiled with LLVM crashes or produces wrong
-results. (<a href="http://llvm.org/PR1388">PR1388</a>)</li>
+<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
+processors, thumb programs can crash or produce wrong
+results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
<li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
</li>
-<li>QEMU-ARM (<= 0.9.0) wrongly executes programs compiled with LLVM. A non-affected QEMU version must be used or this
-<a href="http://cvs.savannah.nongnu.org/viewcvs/qemu/target-arm/translate.c?root=qemu&r1=1.46&r2=1.47&makepatch=1&diff_format=h">
-patch</a> must be applied on QEMU.</li>
+<li>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_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/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_subsubsection">Bugs</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 tthese 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>:
-
- 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>
+<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>
-</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>
<!-- *********************************************************************** -->
<div class="doc_section">
<div class="doc_text">
<p>A wide variety of additional information is available on the <a
-href="http://llvm.org">LLVM web page</a>, including <a
-href="http://llvm.org/docs/">documentation</a> and <a
-href="http://llvm.org/pubs/">publications describing algorithms and
-components implemented in LLVM</a>. The web page also contains versions of the
-API documentation which is up-to-date with the CVS version of the source code.
+href="http://llvm.org">LLVM web page</a>, in particular in the <a
+href="http://llvm.org/docs/">documentation</a> section. The web page also
+contains versions of the API documentation which is up-to-date with the
+Subversion version of the source code.
You can access versions of these documents specific to this release by going
into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
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+ <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
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