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| author | ed <ed@FreeBSD.org> | 2009-06-02 17:52:33 +0000 |
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| committer | ed <ed@FreeBSD.org> | 2009-06-02 17:52:33 +0000 |
| commit | 3277b69d734b9c90b44ebde4ede005717e2c3b2e (patch) | |
| tree | 64ba909838c23261cace781ece27d106134ea451 /docs/ReleaseNotes.html | |
| download | FreeBSD-src-3277b69d734b9c90b44ebde4ede005717e2c3b2e.zip FreeBSD-src-3277b69d734b9c90b44ebde4ede005717e2c3b2e.tar.gz | |
Import LLVM, at r72732.
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diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html new file mode 100644 index 0000000..b0165b05 --- /dev/null +++ b/docs/ReleaseNotes.html @@ -0,0 +1,964 @@ +<!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 2.5 Release Notes</title> +</head> +<body> + +<div class="doc_title">LLVM 2.5 Release Notes</div> + +<ol> + <li><a href="#intro">Introduction</a></li> + <li><a href="#subproj">Sub-project Status Update</a></li> + <li><a href="#externalproj">External Projects Using LLVM 2.5</a></li> + <li><a href="#whatsnew">What's New in LLVM 2.5?</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> + <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> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="intro">Introduction</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>This document contains the release notes for the LLVM Compiler +Infrastructure, release 2.5. 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> + +<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 release, please see the +<a href="http://llvm.org/releases/">releases page</a>.</p> + +</div> + +<!-- Unfinished features in 2.5: + Machine LICM + Machine Sinking + target-specific intrinsics + gold lto plugin + pre-alloc splitter, strong phi elim + <tt>llc -enable-value-prop</tt>, propagation of value info + (sign/zero ext info) from one MBB to another + debug info for optimized code + interpreter + libffi + postalloc scheduler: anti dependence breaking, hazard recognizer? + +initial support for debug line numbers when optimization enabled, not useful in + 2.5 but will be for 2.6. + + --> + + <!-- for announcement email: + --> + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="subproj">Sub-project Status Update</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> +<p> +The LLVM 2.5 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> + + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a> +</div> + +<div class="doc_text"> + +<p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build +a set of new 'LLVM native' front-end technologies for the LLVM optimizer and +code generator. While Clang is not included in the LLVM 2.5 release, it is +continuing to make major strides forward in all areas. Its C and Objective-C +parsing and code generation support is now very solid. For example, it is +capable of successfully building many real-world applications for X86-32 +and X86-64, +including the <a href="http://wiki.freebsd.org/BuildingFreeBSDWithClang">FreeBSD +kernel</a> and <a href="http://gcc.gnu.org/gcc-4.2/">gcc 4.2</a>. C++ is also +making <a href="http://clang.llvm.org/cxx_status.html">incredible progress</a>, +and work on templates has recently started. If you are +interested in fast compiles and good diagnostics, we encourage you to try it out +by <a href="http://clang.llvm.org/get_started.html">building from mainline</a> +and reporting any issues you hit to the <a +href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing +list</a>.</p> + +<p>In the LLVM 2.5 time-frame, the Clang team has made many improvements:</p> + +<ul> +<li>Clang now has a new driver, which is focused on providing a GCC-compatible + interface.</li> +<li>The X86-64 ABI is now supported, including support for the Apple + 64-bit Objective-C runtime and zero cost exception handling.</li> +<li>Precompiled header support is now implemented.</li> +<li>Objective-C support is significantly improved beyond LLVM 2.4, supporting + many features, such as Objective-C Garbage Collection.</li> +<li>Variable length arrays are now fully supported.</li> +<li>C99 designated initializers are now fully supported.</li> +<li>Clang now includes all major compiler headers, including a + redesigned <i>tgmath.h</i> and several more intrinsic headers.</li> +<li>Many many bugs are fixed and many features have been added.</li> +</ul> +</div> + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="clangsa">Clang Static Analyzer</a> +</div> + +<div class="doc_text"> + +<p>Previously announced in the last LLVM release, 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.</p> + +<p>In the LLVM 2.5 time-frame there have been many significant improvements to +the analyzer's core path simulation engine and machinery for generating +path-based bug reports to end-users. Particularly noteworthy improvements +include experimental support for full field-sensitivity and reasoning about heap +objects as well as an improved value-constraints subengine that does a much +better job of reasoning about inequality relationships (e.g., <tt>x > 2</tt>) +between variables and constants. + +<p>The set of checks performed by the static analyzer continues to expand, 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="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>Following LLVM 2.5, VMKit has its second release 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>Ahead of Time compiler: compiles .class files to llvm .bc. VMKit uses this +functionality to native compile the standard classes (e.g. java.lang.String). +Users can compile AoT .class files into dynamic libraries and run them with the +help of VMKit.</li> + +<li>New exception model: the dwarf exception model is very slow for +exception-intensive applications, so the JVM has had a new implementation of +exceptions which check at each function call if an exception happened. There is +a low performance penalty on applications without exceptions, but it is a big +gain for exception-intensive applications. For example the jack benchmark in +Spec JVM98 is 6x faster (performance gain of 83%).</li> + +<li>User-level management of thread stacks, so that thread local data access +at runtime is fast and portable. </li> + +<li>Implementation of biased locking for faster object synchronizations at +runtime.</li> + +<li>New support for OSX/X64, Linux/X64 (with the Boehm GC) and Linux/ppc32.</li> + +</ul> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="externalproj">External Projects Using LLVM 2.5</a> +</div> +<!-- *********************************************************************** --> + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="pure">Pure</a> +</div> + +<div class="doc_text"> +<p> +<a href="http://pure-lang.googlecode.com/">Pure</a> +is an algebraic/functional programming language based on term rewriting. +Programs are collections of equations which are used to evaluate expressions in +a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation, +lexical closures, a hygienic macro system (also based on term rewriting), +built-in list and matrix support (including list and matrix comprehensions) and +an easy-to-use C interface. The interpreter uses LLVM as a backend to + JIT-compile Pure programs to fast native code.</p> + +<p>In addition to the usual algebraic data structures, Pure also has +MATLAB-style matrices in order to support numeric computations and signal +processing in an efficient way. Pure is mainly aimed at mathematical +applications right now, but it has been designed as a general purpose language. +The dynamic interpreter environment and the C interface make it possible to use +it as a kind of functional scripting language for many application areas. +</p> +</div> + + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="ldc">LLVM D Compiler</a> +</div> + +<div class="doc_text"> +<p> +<a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of +the D Programming Language using the LLVM optimizer and code generator. +The LDC project works great with the LLVM 2.5 release. General improvements in +this +cycle have included new inline asm constraint handling, better debug info +support, general bugfixes, and better x86-64 support. This has allowed +some major improvements in LDC, getting us much closer to being as +fully featured as the original DMD compiler from DigitalMars. +</p> +</div> + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="RoadsendPHP">Roadsend PHP</a> +</div> + +<div class="doc_text"> +<p><a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open +source implementation of the PHP programming +language that uses LLVM for its optimizer, JIT, and static compiler. This is a +reimplementation of an earlier project that is now based on LLVM.</p> +</div> + + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="whatsnew">What's New in LLVM 2.5?</a> +</div> +<!-- *********************************************************************** --> + +<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="majorfeatures">Major New Features</a> +</div> + +<div class="doc_text"> + +<p>LLVM 2.5 includes several major new capabilities:</p> + +<ul> +<li>LLVM 2.5 includes a brand new <a +href="http://en.wikipedia.org/wiki/XCore">XCore</a> backend.</li> + +<li>llvm-gcc now generally supports the GFortran front-end, and the precompiled +release binaries now support Fortran, even on Mac OS/X.</li> + +<li>CMake is now used by the <a href="GettingStartedVS.html">LLVM build process +on Windows</a>. It automatically generates Visual Studio project files (and +more) from a set of simple text files. This makes it much easier to +maintain. In time, we'd like to standardize on CMake for everything.</li> + +<li>LLVM 2.5 now uses (and includes) Google Test for unit testing.</li> + +<li>The LLVM native code generator now supports arbitrary precision integers. +Types like <tt>i33</tt> have long been valid in the LLVM IR, but were previously +only supported by the interpreter. Note that the C backend still does not +support these.</li> + +<li>LLVM 2.5 no longer uses 'bison,' so it is easier to build on Windows.</li> +</ul> + +</div> + + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="llvm-gcc">llvm-gcc 4.2 Improvements</a> +</div> + +<div class="doc_text"> + +<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>In this release, the GCC inliner is completely disabled. Previously the GCC +inliner was used to handle always-inline functions and other cases. This caused +problems with code size growth, and it is completely disabled in this +release.</li> + +<li>llvm-gcc (and LLVM in general) now support code generation for stack +canaries, which is an effective form of <a +href="http://en.wikipedia.org/wiki/Stack-smashing_protection">buffer overflow +protection</a>. llvm-gcc supports this with the <tt>-fstack-protector</tt> +command line option (just like GCC). In LLVM IR, you can request code +generation for stack canaries with function attributes. +</li> +</ul> + +</div> + + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="coreimprovements">LLVM IR and Core Improvements</a> +</div> + +<div class="doc_text"> +<p>LLVM IR has several new features that are used by our existing front-ends and +can be useful if you are writing a front-end for LLVM:</p> + +<ul> +<li>The <a href="LangRef.html#i_shufflevector">shufflevector</a> instruction +has been generalized to allow different shuffle mask width than its input +vectors. This allows you to use shufflevector to combine two +"<4 x float>" vectors into a "<8 x float>" for example.</li> + +<li>LLVM IR now supports new intrinsics for computing and acting on <a +href="LangRef.html#int_overflow">overflow of integer operations</a>. This allows +efficient code generation for languages that must trap or throw an exception on +overflow. While these intrinsics work on all targets, they only generate +efficient code on X86 so far.</li> + +<li>LLVM IR now supports a new <a href="LangRef.html#linkage">private +linkage</a> type to produce labels that are stripped by the assembler before it +produces a .o file (thus they are invisible to the linker).</li> + +<li>LLVM IR supports two new attributes for better alias analysis. The <a +href="LangRef.html#paramattrs">noalias</a> attribute can now be used on the +return value of a function to indicate that it returns new memory (e.g. +'malloc', 'calloc', etc). +The new <a href="LangRef.html#paramattrs">nocapture</a> attribute can be used +on pointer arguments to indicate that the function does not return the pointer, +store it in an object that outlives the call, or let the value of the pointer +escape from the function in any other way. +Note that it is the pointer itself that must not escape, not the value it +points to: loading a value out of the pointer is perfectly fine. +Many standard library functions (e.g. 'strlen', 'memcpy') have this property. +<!-- The simplifylibcalls pass applies these attributes to standard libc functions. --> +</li> + +<li>The parser for ".ll" files in lib/AsmParser is now completely rewritten as a +recursive descent parser. This parser produces better error messages (including +caret diagnostics), is less fragile (less likely to crash on strange things), +does not leak memory, is more efficient, and eliminates LLVM's last use of the +'bison' tool.</li> + +<li>Debug information representation and manipulation internals have been + consolidated to use a new set of classes in + <tt>llvm/Analysis/DebugInfo.h</tt>. These routines are more + efficient, robust, and extensible and replace the older mechanisms. + llvm-gcc, clang, and the code generator now use them to create and process + debug information.</li> + +</ul> + +</div> + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="optimizer">Optimizer Improvements</a> +</div> + +<div class="doc_text"> + +<p>In addition to a large array of bug fixes and minor performance tweaks, this +release includes a few major enhancements and additions to the optimizers:</p> + +<ul> + +<li>The loop optimizer now improves floating point induction variables in +several ways, including adding shadow induction variables to avoid +"integer <-> floating point" conversions in loops when safe.</li> + +<li>The "-mem2reg" pass is now much faster on code with large basic blocks.</li> + +<li>The "-jump-threading" pass is more powerful: it is iterative + and handles threading based on values with fully and partially redundant + loads.</li> + +<li>The "-memdep" memory dependence analysis pass (used by GVN and memcpyopt) is + both faster and more aggressive.</li> + +<li>The "-scalarrepl" scalar replacement of aggregates pass is more aggressive + about promoting unions to registers.</li> + +</ul> + +</div> + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="codegen">Target Independent Code Generator Improvements</a> +</div> + +<div class="doc_text"> + +<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>The <a href="WritingAnLLVMBackend.html">Writing an LLVM Compiler +Backend</a> document has been greatly expanded and is substantially more +complete.</li> + +<li>The SelectionDAG type legalization logic has been completely rewritten, is +now more powerful (it supports arbitrary precision integer types for example), +and is more correct in several corner cases. The type legalizer converts +operations on types that are not natively supported by the target machine into +equivalent code sequences that only use natively supported types. The old type +legalizer is still available (for now) and will be used if +<tt>-disable-legalize-types</tt> is passed to the code generator. +</li> + +<li>The code generator now supports widening illegal vectors to larger legal +ones (for example, converting operations on <3 x float> to work on +<4 x float>) which is very important for common graphics +applications.</li> + +<li>The assembly printers for each target are now split out into their own +libraries that are separate from the main code generation logic. This reduces +the code size of JIT compilers by not requiring them to be linked in.</li> + +<li>The 'fast' instruction selection path (used at -O0 and for fast JIT + compilers) now supports accelerating codegen for code that uses exception + handling constructs.</li> + +<li>The optional PBQP register allocator now supports register coalescing.</li> +</ul> +</div> + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="x86">X86-32 and X86-64 Target Improvements</a> +</div> + +<div class="doc_text"> +<p>New features of the X86 target include: +</p> + +<ul> +<li>The <tt><a href="LangRef.html#int_returnaddress">llvm.returnaddress</a></tt> +intrinsic (which is used to implement <tt>__builtin_return_address</tt>) now +supports non-zero stack depths on X86.</li> + +<li>The X86 backend now supports code generation of vector shift operations +using SSE instructions.</li> + +<li>X86-64 code generation now takes advantage of red zone, unless the +<tt>-mno-red-zone</tt> option is specified.</li> + +<li>The X86 backend now supports using address space #256 in LLVM IR as a way of +performing memory references off the GS segment register. This allows a +front-end to take advantage of very low-level programming techniques when +targeting X86 CPUs. See <tt>test/CodeGen/X86/movgs.ll</tt> for a simple +example.</li> + +<li>The X86 backend now supports a <tt>-disable-mmx</tt> command line option to + prevent use of MMX even on chips that support it. This is important for cases + where code does not contain the proper <tt>llvm.x86.mmx.emms</tt> + intrinsics.</li> + +<li>The X86 JIT now detects the new Intel <a + href="http://en.wikipedia.org/wiki/Intel_Core_i7">Core i7</a> and <a + href="http://en.wikipedia.org/wiki/Intel_Atom">Atom</a> chips and + auto-configures itself appropriately for the features of these chips.</li> + +<li>The JIT now supports exception handling constructs on Linux/X86-64 and + Darwin/x86-64.</li> + +<li>The JIT supports Thread Local Storage (TLS) on Linux/X86-32 but not yet on + X86-64.</li> +</ul> + +</div> + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="pic16">PIC16 Target Improvements</a> +</div> + +<div class="doc_text"> +<p>New features of the PIC16 target include: +</p> + +<ul> +<li>Both direct and indirect load/stores work now.</li> +<li>Logical, bitwise and conditional operations now work for integer data +types.</li> +<li>Function calls involving basic types work now.</li> +<li>Support for integer arrays.</li> +<li>The compiler can now emit libcalls for operations not supported by m/c +instructions.</li> +<li>Support for both data and ROM address spaces.</li> +</ul> + +<p>Things not yet supported:</p> + +<ul> +<li>Floating point.</li> +<li>Passing/returning aggregate types to and from functions.</li> +<li>Variable arguments.</li> +<li>Indirect function calls.</li> +<li>Interrupts/programs.</li> +<li>Debug info.</li> +</ul> + +</div> + + +<!--=========================================================================--> +<div class="doc_subsection"> +<a name="llvmc">Improvements in LLVMC</a> +</div> + +<div class="doc_text"> +<p>New features include:</p> + +<ul> +<li>Beginning with LLVM 2.5, <tt>llvmc2</tt> is known as + just <tt>llvmc</tt>. The old <tt>llvmc</tt> driver was removed.</li> + +<li>The Clang plugin was substantially improved and is now enabled + by default. The command <tt>llvmc --clang</tt> can be now used as a + synonym to <tt>ccc</tt>.</li> + +<li>There is now a <tt>--check-graph</tt> option, which is supposed to catch + common errors like multiple default edges, mismatched output/input language + names and cycles. In general, these checks can't be done at compile-time + because of the need to support plugins.</li> + +<li>Plugins are now more flexible and can refer to compilation graph nodes and + options defined in other plugins. To manage dependencies, a priority-sorting + mechanism was introduced. This change affects the TableGen file syntax. See the + documentation for details.</li> + +<li>Hooks can now be provided with arguments. The syntax is "<tt>$CALL(MyHook, + 'Arg1', 'Arg2', 'Arg3')</tt>".</li> + +<li>A new option type: multi-valued option, for options that take more than one + argument (for example, "<tt>-foo a b c</tt>").</li> + +<li>New option properties: '<tt>one_or_more</tt>', '<tt>zero_or_more</tt>', +'<tt>hidden</tt>' and '<tt>really_hidden</tt>'.</li> + +<li>The '<tt>case</tt>' expression gained an '<tt>error</tt>' action and + an '<tt>empty</tt>' test (equivalent to "<tt>(not (not_empty ...))</tt>").</li> + +<li>Documentation now looks more consistent to the rest of the LLVM + docs. There is also a man page now.</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 2.4, this section lists some "gotchas" that you may run into upgrading +from the previous release.</p> + +<ul> + +<li>llvm-gcc defaults to <tt>-fno-math-errno</tt> on all X86 targets.</li> + +</ul> + + +<p>In addition, many APIs have changed in this release. Some of the major LLVM +API changes are:</p> + +<ul> +<li>Some deprecated interfaces to create <tt>Instruction</tt> subclasses, that + were spelled with lower case "create," have been removed.</li> +</ul> + +</div> + + + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="portability">Portability and Supported Platforms</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>LLVM is known to work on the following platforms:</p> + +<ul> +<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 10.</li> +<li>Alpha-based machines running Debian GNU/Linux.</li> +<li>Itanium-based (IA64) machines running Linux and HP-UX.</li> +</ul> + +<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> + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="knownproblems">Known Problems</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<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> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="experimental">Experimental features included with this release</a> +</div> + +<div class="doc_text"> + +<p>The following components of this LLVM release are either untested, known to +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> + +<ul> +<li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li> +<li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only + supported value for this option.</li> +</ul> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="x86-be">Known problems with the X86 back-end</a> +</div> + +<div class="doc_text"> + +<ul> + <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 the mingw64 + runtime currently due + to <a href="http://llvm.org/PR2255">several</a> + <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for + the + 'u' inline assembly constraint and for 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 and front-ends support variadic + argument constructs on X86-64 by lowering them manually.</li> +</ul> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="ppc-be">Known problems with the PowerPC back-end</a> +</div> + +<div class="doc_text"> + +<ul> +<li>The Linux PPC32/ABI support needs testing for the interpreter and static +compilation, and lacks support for debug information.</li> +</ul> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="arm-be">Known problems with the ARM back-end</a> +</div> + +<div class="doc_text"> + +<ul> +<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6 +processors, thumb programs can crash or produce wrong +results (<a href="http://llvm.org/PR1388">PR1388</a>).</li> +<li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested. +</li> +<li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly + execute +programs compiled with LLVM. Please use more recent versions of QEMU.</li> +</ul> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="sparc-be">Known problems with the SPARC back-end</a> +</div> + +<div class="doc_text"> + +<ul> +<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not + support the 64-bit SPARC ABI (-m64).</li> +</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> + +<div class="doc_text"> + +<ul> + +<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the +appropriate nops inserted to ensure restartability.</li> + +</ul> +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="ia64-be">Known problems with the IA64 back-end</a> +</div> + +<div class="doc_text"> + +<ul> +<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_subsection"> + <a name="c-be">Known problems with the C back-end</a> +</div> + +<div class="doc_text"> + +<ul> +<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 <tt>llc</tt> or native compilers.</li> +<li>The C backend does not support all exception handling constructs.</li> +<li>The C backend does not support arbitrary precision integers.</li> +</ul> + +</div> + + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="c-fe">Known problems with the llvm-gcc C front-end</a> +</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> + +<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_subsection"> + <a name="c++-fe">Known problems with the llvm-gcc C++ 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 works well on the X86 and PowerPC targets. Currently + only Linux and Darwin targets are supported (both 32 and 64 bit).</li> +</ul> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a> +</div> + +<div class="doc_text"> +<ul> +<li>Fortran support generally works, but there are still several unresolved bugs + in Bugzilla. Please see the tools/gfortran component for details.</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>. +This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style +exception handling, which is used internally by the compiler. +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). +If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a> +causes the compiler to go into an infinite loop, using up all system memory.</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"> + <a name="additionalinfo">Additional Information</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>A wide variety of additional information is available on the <a +href="http://llvm.org">LLVM web page</a>, 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> + +<p>If you have any questions or comments about LLVM, please feel free to contact +us via the <a href="http://llvm.org/docs/#maillist"> mailing +lists</a>.</p> + +</div> + +<!-- *********************************************************************** --> + +<hr> +<address> + <a href="http://jigsaw.w3.org/css-validator/check/referer"><img + src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a> + <a href="http://validator.w3.org/check/referer"><img + src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a> + + <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br> + Last modified: $Date: 2009-03-02 21:08:12 +0100 (Mon, 02 Mar 2009) $ +</address> + +</body> +</html> |
