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11 <h1>LLVM 3.0 Release Notes</h1>
13 <img align=right src="http://llvm.org/img/DragonSmall.png"
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17 <li><a href="#intro">Introduction</a></li>
18 <li><a href="#subproj">Sub-project Status Update</a></li>
19 <li><a href="#externalproj">External Projects Using LLVM 3.0</a></li>
20 <li><a href="#whatsnew">What's New in LLVM 3.0?</a></li>
21 <li><a href="GettingStarted.html">Installation Instructions</a></li>
22 <li><a href="#knownproblems">Known Problems</a></li>
23 <li><a href="#additionalinfo">Additional Information</a></li>
26 <div class="doc_author">
27 <p>Written by the <a href="http://llvm.org/">LLVM Team</a></p>
31 <h1 style="color:red">These are in-progress notes for the upcoming LLVM 3.0
34 <a href="http://llvm.org/releases/2.9/docs/ReleaseNotes.html">LLVM 2.9
35 Release Notes</a>.</h1>
38 <!-- *********************************************************************** -->
40 <a name="intro">Introduction</a>
42 <!-- *********************************************************************** -->
46 <p>This document contains the release notes for the LLVM Compiler
47 Infrastructure, release 3.0. Here we describe the status of LLVM, including
48 major improvements from the previous release and significant known problems.
49 All LLVM releases may be downloaded from the <a
50 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
52 <p>For more information about LLVM, including information about the latest
53 release, please check out the <a href="http://llvm.org/">main LLVM
54 web site</a>. If you have questions or comments, the <a
55 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
56 Mailing List</a> is a good place to send them.</p>
58 <p>Note that if you are reading this file from a Subversion checkout or the
59 main LLVM web page, this document applies to the <i>next</i> release, not the
60 current one. To see the release notes for a specific release, please see the
61 <a href="http://llvm.org/releases/">releases page</a>.</p>
65 <!-- Features that need text if they're finished for 3.1:
69 loop dependence analysis
70 CorrelatedValuePropagation
71 lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
74 <!-- *********************************************************************** -->
76 <a name="subproj">Sub-project Status Update</a>
78 <!-- *********************************************************************** -->
82 The LLVM 3.0 distribution currently consists of code from the core LLVM
83 repository (which roughly includes the LLVM optimizers, code generators
84 and supporting tools), the Clang repository and the llvm-gcc repository. In
85 addition to this code, the LLVM Project includes other sub-projects that are in
86 development. Here we include updates on these subprojects.
89 <!--=========================================================================-->
91 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
96 <p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
97 C++, and Objective-C languages. Clang aims to provide a better user experience
98 through expressive diagnostics, a high level of conformance to language
99 standards, fast compilation, and low memory use. Like LLVM, Clang provides a
100 modular, library-based architecture that makes it suitable for creating or
101 integrating with other development tools. Clang is considered a
102 production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
103 (32- and 64-bit), and for darwin/arm targets.</p>
105 <p>In the LLVM 3.0 time-frame, the Clang team has made many improvements:</p>
108 <li>Greatly improved support for building C++ applications, with greater stability and better diagnostics.</li>
110 <li><a href="http://clang.llvm.org/cxx_status.html">Improved support</a> for the <a href="http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50372 ">C++ 2011</a> standard, including implementations of non-static data member initializers, alias templates, delegating constructors, the range-based for loop, and implicitly-generated move constructors and move assignment operators, among others.</li>
112 <li>Implemented support for some features of the upcoming C1x standard, including static assertions and generic selections.</li>
114 <li>Better detection of include and linking paths for system headers and libraries, especially for Linux distributions.</li>
116 <li>Implemented support for <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">Automatic Reference Counting</a> for Objective-C.</li>
118 <li>Implemented a number of optimizations in <tt>libclang</tt>, the Clang C interface, to improve the performance of code completion and the mapping from source locations to abstract syntax tree nodes.</li>
122 <p>If Clang rejects your code but another compiler accepts it, please take a
123 look at the <a href="http://clang.llvm.org/compatibility.html">language
124 compatibility</a> guide to make sure this is not intentional or a known issue.
129 <!--=========================================================================-->
131 <a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
136 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
137 <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
138 optimizers and code generators with LLVM's.
139 Currently it requires a patched version of gcc-4.5.
140 The plugin can target the x86-32 and x86-64 processor families and has been
141 used successfully on the Darwin, FreeBSD and Linux platforms.
142 The Ada, C, C++ and Fortran languages work well.
143 The plugin is capable of compiling plenty of Obj-C, Obj-C++ and Java but it is
144 not known whether the compiled code actually works or not!
148 The 3.0 release has the following notable changes:
157 <!--=========================================================================-->
159 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
164 The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
165 is a simple library that provides an implementation of the low-level
166 target-specific hooks required by code generation and other runtime components.
167 For example, when compiling for a 32-bit target, converting a double to a 64-bit
168 unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
169 function. The compiler-rt library provides highly optimized implementations of
170 this and other low-level routines (some are 3x faster than the equivalent
171 libgcc routines).</p>
173 <p>In the LLVM 3.0 timeframe,</p>
177 <!--=========================================================================-->
179 <a name="lldb">LLDB: Low Level Debugger</a>
184 <a href="http://lldb.llvm.org/">LLDB</a> is a brand new member of the LLVM
185 umbrella of projects. LLDB is a next generation, high-performance debugger. It
186 is built as a set of reusable components which highly leverage existing
187 libraries in the larger LLVM Project, such as the Clang expression parser, the
188 LLVM disassembler and the LLVM JIT.</p>
191 LLDB is has advanced by leaps and bounds in the 3.0 timeframe. It is
192 dramatically more stable and useful, and includes both a new <a
193 href="http://lldb.llvm.org/tutorial.html">tutorial</a> and a <a
194 href="http://lldb.llvm.org/lldb-gdb.html">side-by-side comparison with
199 <!--=========================================================================-->
201 <a name="libc++">libc++: C++ Standard Library</a>
206 <a href="http://libcxx.llvm.org/">libc++</a> is another new member of the LLVM
207 family. It is an implementation of the C++ standard library, written from the
208 ground up to specifically target the forthcoming C++'0X standard and focus on
209 delivering great performance.</p>
212 In the LLVM 3.0 timeframe,</p>
215 Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
216 licensed</a> under the MIT and UIUC license, allowing it to be used more
223 <!--=========================================================================-->
225 <a name="LLBrowse">LLBrowse: IR Browser</a>
230 <a href="http://llvm.org/svn/llvm-project/llbrowse/trunk/doc/LLBrowse.html">
231 LLBrowse</a> is an interactive viewer for LLVM modules. It can load any LLVM
232 module and displays its contents as an expandable tree view, facilitating an
233 easy way to inspect types, functions, global variables, or metadata nodes. It
234 is fully cross-platform, being based on the popular wxWidgets GUI toolkit.
238 <!--=========================================================================-->
240 <a name="vmkit">VMKit</a>
244 <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
245 of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
246 just-in-time compilation. As of LLVM 3.0, VMKit now supports generational
247 garbage collectors. The garbage collectors are provided by the MMTk framework,
248 and VMKit can be configured to use one of the numerous implemented collectors
254 <!--=========================================================================-->
257 <a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
262 <a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
263 programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
264 through the application and records state transitions that lead to fault
265 states. This allows it to construct testcases that lead to faults and can even
266 be used to verify some algorithms.
274 <!-- *********************************************************************** -->
276 <a name="externalproj">External Open Source Projects Using LLVM 3.0</a>
278 <!-- *********************************************************************** -->
282 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
283 a lot of other language and tools projects. This section lists some of the
284 projects that have already been updated to work with LLVM 3.0.</p>
286 <!--=========================================================================-->
287 <h3>Crack Programming Language</h3>
291 <a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide the
292 ease of development of a scripting language with the performance of a compiled
293 language. The language derives concepts from C++, Java and Python, incorporating
294 object-oriented programming, operator overloading and strong typing.</p>
298 <!--=========================================================================-->
299 <h3>TTA-based Codesign Environment (TCE)</h3>
302 <p>TCE is a toolset for designing application-specific processors (ASP) based on
303 the Transport triggered architecture (TTA). The toolset provides a complete
304 co-design flow from C/C++ programs down to synthesizable VHDL and parallel
305 program binaries. Processor customization points include the register files,
306 function units, supported operations, and the interconnection network.</p>
308 <p>TCE uses Clang and LLVM for C/C++ language support, target independent
309 optimizations and also for parts of code generation. It generates new LLVM-based
310 code generators "on the fly" for the designed TTA processors and loads them in
311 to the compiler backend as runtime libraries to avoid per-target recompilation
312 of larger parts of the compiler chain.</p>
317 <!--=========================================================================-->
321 <p><a href="http://gitorious.org/pinavm/pages/Home">PinaVM</a> is an open
322 source, <a href="http://www.systemc.org/">SystemC</a> front-end. Unlike many
323 other front-ends, PinaVM actually executes the elaboration of the
324 program analyzed using LLVM's JIT infrastructure. It later enriches the
325 bitcode with SystemC-specific information.</p>
328 <!--=========================================================================-->
332 <p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
334 programming language based on term rewriting. Programs are collections
335 of equations which are used to evaluate expressions in a symbolic
336 fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
337 programs to fast native code. Pure offers dynamic typing, eager and lazy
338 evaluation, lexical closures, a hygienic macro system (also based on
339 term rewriting), built-in list and matrix support (including list and
340 matrix comprehensions) and an easy-to-use interface to C and other
341 programming languages (including the ability to load LLVM bitcode
342 modules, and inline C, C++, Fortran and Faust code in Pure programs if
343 the corresponding LLVM-enabled compilers are installed).</p>
345 <p>Pure version 0.47 has been tested and is known to work with LLVM 3.0
346 (and continues to work with older LLVM releases >= 2.5).</p>
349 <!--=========================================================================-->
350 <h3 id="icedtea">IcedTea Java Virtual Machine Implementation</h3>
354 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
355 harness to build OpenJDK using only free software build tools and to provide
356 replacements for the not-yet free parts of OpenJDK. One of the extensions that
357 IcedTea provides is a new JIT compiler named <a
358 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
359 to provide native code generation without introducing processor-dependent
363 <p> OpenJDK 7 b112, IcedTea6 1.9 and IcedTea7 1.13 and later have been tested
364 and are known to work with LLVM 3.0 (and continue to work with older LLVM
365 releases >= 2.6 as well).</p>
368 <!--=========================================================================-->
369 <h3>Glasgow Haskell Compiler (GHC)</h3>
372 <p>GHC is an open source, state-of-the-art programming suite for Haskell,
373 a standard lazy functional programming language. It includes an
374 optimizing static compiler generating good code for a variety of
375 platforms, together with an interactive system for convenient, quick
378 <p>In addition to the existing C and native code generators, GHC 7.0 now
379 supports an LLVM code generator. GHC supports LLVM 2.7 and later.</p>
382 <!--=========================================================================-->
383 <h3>Polly - Polyhedral optimizations for LLVM</h3>
386 <p>Polly is a project that aims to provide advanced memory access optimizations
387 to better take advantage of SIMD units, cache hierarchies, multiple cores or
388 even vector accelerators for LLVM. Built around an abstract mathematical
389 description based on Z-polyhedra, it provides the infrastructure to develop
390 advanced optimizations in LLVM and to connect complex external optimizers. In
391 its first year of existence Polly already provides an exact value-based
392 dependency analysis as well as basic SIMD and OpenMP code generation support.
393 Furthermore, Polly can use PoCC(Pluto) an advanced optimizer for data-locality
397 <!--=========================================================================-->
401 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
402 for running Ruby code which strives to write as much of the implementation in
403 Ruby as possible. Combined with a bytecode interpreting VM, it uses LLVM to
404 optimize and compile ruby code down to machine code. Techniques such as type
405 feedback, method inlining, and deoptimization are all used to remove dynamism
406 from ruby execution and increase performance.</p>
410 <!--=========================================================================-->
412 <a name="FAUST">FAUST Real-Time Audio Signal Processing Language</a>
417 <a href="http://faust.grame.fr">FAUST</a> is a compiled language for real-time
418 audio signal processing. The name FAUST stands for Functional AUdio STream. Its
419 programming model combines two approaches: functional programming and block
420 diagram composition. In addition with the C, C++, JAVA output formats, the
421 Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7-3.0.</p>
427 <!-- *********************************************************************** -->
429 <a name="whatsnew">What's New in LLVM 3.0?</a>
431 <!-- *********************************************************************** -->
435 <p>This release includes a huge number of bug fixes, performance tweaks and
436 minor improvements. Some of the major improvements and new features are listed
440 <!--=========================================================================-->
442 <a name="majorfeatures">Major New Features</a>
447 <p>LLVM 3.0 includes several major new capabilities:</p>
459 <!--=========================================================================-->
461 <a name="coreimprovements">LLVM IR and Core Improvements</a>
465 <p>LLVM IR has several new features for better support of new targets and that
466 expose new optimization opportunities:</p>
476 <!--=========================================================================-->
478 <a name="optimizer">Optimizer Improvements</a>
483 <p>In addition to a large array of minor performance tweaks and bug fixes, this
484 release includes a few major enhancements and additions to the optimizers:</p>
496 <!--=========================================================================-->
498 <a name="mc">MC Level Improvements</a>
503 The LLVM Machine Code (aka MC) subsystem was created to solve a number
504 of problems in the realm of assembly, disassembly, object file format handling,
505 and a number of other related areas that CPU instruction-set level tools work
514 <p>For more information, please see the <a
515 href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
516 LLVM MC Project Blog Post</a>.
521 <!--=========================================================================-->
523 <a name="codegen">Target Independent Code Generator Improvements</a>
528 <p>We have put a significant amount of work into the code generator
529 infrastructure, which allows us to implement more aggressive algorithms and make
539 <!--=========================================================================-->
541 <a name="x86">X86-32 and X86-64 Target Improvements</a>
545 <p>New features and major changes in the X86 target include:
549 <li>The CRC32 intrinsics have been renamed. The intrinsics were previously
550 @llvm.x86.sse42.crc32.[8|16|32] and @llvm.x86.sse42.crc64.[8|64]. They have
551 been renamed to @llvm.x86.sse42.crc32.32.[8|16|32] and
552 @llvm.x86.sse42.crc32.64.[8|64].</li>
558 <!--=========================================================================-->
560 <a name="ARM">ARM Target Improvements</a>
564 <p>New features of the ARM target include:
574 <!--=========================================================================-->
576 <a name="OtherTS">Other Target Specific Improvements</a>
587 <!--=========================================================================-->
589 <a name="changes">Major Changes and Removed Features</a>
594 <p>If you're already an LLVM user or developer with out-of-tree changes based on
595 LLVM 2.9, this section lists some "gotchas" that you may run into upgrading
596 from the previous release.</p>
599 <li>The <code>LLVMC</code> front end code was removed while separating
600 out language independence.</li>
601 <li>The <code>LowerSetJmp</code> pass wasn't used effectively by any
602 target and has been removed.</li>
603 <li>The old <code>TailDup</code> pass was not used in the standard pipeline
604 and was unable to update ssa form, so it has been removed.
605 <li>The syntax of volatile loads and stores in IR has been changed to
606 "<code>load volatile</code>"/"<code>store volatile</code>". The old
607 syntax ("<code>volatile load</code>"/"<code>volatile store</code>")
608 is still accepted, but is now considered deprecated.</li>
611 <h4>Windows (32-bit)</h4>
614 <li>On Win32(MinGW32 and MSVC), Windows 2000 will not be supported.
615 Windows XP or higher is required.</li>
621 <!--=========================================================================-->
623 <a name="api_changes">Internal API Changes</a>
628 <p>In addition, many APIs have changed in this release. Some of the major
629 LLVM API changes are:</p>
632 <li>The biggest and most pervasive change is that llvm::Type's are no longer
633 returned or accepted as 'const' values. Instead, just pass around non-const
636 <li><code>PHINode::reserveOperandSpace</code> has been removed. Instead, you
637 must specify how many operands to reserve space for when you create the
638 PHINode, by passing an extra argument into <code>PHINode::Create</code>.</li>
640 <li>PHINodes no longer store their incoming BasicBlocks as operands. Instead,
641 the list of incoming BasicBlocks is stored separately, and can be accessed
642 with new functions <code>PHINode::block_begin</code>
643 and <code>PHINode::block_end</code>.</li>
645 <li>Various functions now take an <code>ArrayRef</code> instead of either a pair
646 of pointers (or iterators) to the beginning and end of a range, or a pointer
647 and a length. Others now return an <code>ArrayRef</code> instead of a
648 reference to a <code>SmallVector</code> or <code>std::vector</code>. These
651 <!-- Please keep this list sorted. -->
652 <li><code>CallInst::Create</code></li>
653 <li><code>ComputeLinearIndex</code> (in <code>llvm/CodeGen/Analysis.h</code>)</li>
654 <li><code>ConstantArray::get</code></li>
655 <li><code>ConstantExpr::getExtractElement</code></li>
656 <li><code>ConstantExpr::getGetElementPtr</code></li>
657 <li><code>ConstantExpr::getInBoundsGetElementPtr</code></li>
658 <li><code>ConstantExpr::getIndices</code></li>
659 <li><code>ConstantExpr::getInsertElement</code></li>
660 <li><code>ConstantExpr::getWithOperands</code></li>
661 <li><code>ConstantFoldCall</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
662 <li><code>ConstantFoldInstOperands</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
663 <li><code>ConstantVector::get</code></li>
664 <li><code>DIBuilder::createComplexVariable</code></li>
665 <li><code>DIBuilder::getOrCreateArray</code></li>
666 <li><code>ExtractValueInst::Create</code></li>
667 <li><code>ExtractValueInst::getIndexedType</code></li>
668 <li><code>ExtractValueInst::getIndices</code></li>
669 <li><code>FindInsertedValue</code> (in <code>llvm/Analysis/ValueTracking.h</code>)</li>
670 <li><code>gep_type_begin</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
671 <li><code>gep_type_end</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
672 <li><code>GetElementPtrInst::Create</code></li>
673 <li><code>GetElementPtrInst::CreateInBounds</code></li>
674 <li><code>GetElementPtrInst::getIndexedType</code></li>
675 <li><code>InsertValueInst::Create</code></li>
676 <li><code>InsertValueInst::getIndices</code></li>
677 <li><code>InvokeInst::Create</code></li>
678 <li><code>IRBuilder::CreateCall</code></li>
679 <li><code>IRBuilder::CreateExtractValue</code></li>
680 <li><code>IRBuilder::CreateGEP</code></li>
681 <li><code>IRBuilder::CreateInBoundsGEP</code></li>
682 <li><code>IRBuilder::CreateInsertValue</code></li>
683 <li><code>IRBuilder::CreateInvoke</code></li>
684 <li><code>MDNode::get</code></li>
685 <li><code>MDNode::getIfExists</code></li>
686 <li><code>MDNode::getTemporary</code></li>
687 <li><code>MDNode::getWhenValsUnresolved</code></li>
688 <li><code>SimplifyGEPInst</code> (in <code>llvm/Analysis/InstructionSimplify.h</code>)</li>
689 <li><code>TargetData::getIndexedOffset</code></li>
692 <li>All forms of <code>StringMap::getOrCreateValue</code> have been remove
693 except for the one which takes a <code>StringRef</code>.</li>
695 <li>The <code>LLVMBuildUnwind</code> function from the C API was removed. The
696 LLVM <code>unwind</code> instruction has been deprecated for a long time and
697 isn't used by the current front-ends. So this was removed during the
698 exception handling rewrite.</li>
700 <li>The <code>LLVMAddLowerSetJmpPass</code> function from the C API was removed
701 because the <code>LowerSetJmp</code> pass was removed.</li>
703 <li>The <code>DIBuilder</code> interface used by front ends to encode debugging
704 information in the LLVM IR now expects clients to use <code>DIBuilder::finalize()</code>
705 at the end of translation unit to complete debugging information encoding.</li>
707 <li>The way the type system works has been rewritten: <code>PATypeHolder</code>
708 and <code>OpaqueType</code> are gone, and all APIs deal with <code>Type*</code>
709 instead of <code>const Type*</code>.
710 If you need to create recursive structures, then create a named structure,
711 and use <code>setBody()</code> when all its elements are built.
712 Type merging and refining is gone too: named structures are not
713 merged with other structures, even if their layout is identical.
714 (of course anonymous structures are still uniqued by layout).
717 <li>TargetSelect.h moved to Support/ from Target/</li>
719 <li>UpgradeIntrinsicCall no longer upgrades pre-2.9 intrinsic calls
720 (for example <code>llvm.memset.i32</code>).</li>
722 <li>It is mandatory to initialize all out-of-tree passes too and their dependencies now with
723 <code>INITIALIZE_PASS{BEGIN,END,}</code> and <code>INITIALIZE_{PASS,AG}_DEPENDENCY</code>.</li>
725 <li>The interface for MemDepResult in MemoryDependenceAnalysis has been enhanced
726 with new return types Unknown and NonFuncLocal, in addition to the existing
727 types Clobber, Def, and NonLocal.</li>
734 <!-- *********************************************************************** -->
736 <a name="knownproblems">Known Problems</a>
738 <!-- *********************************************************************** -->
742 <p>This section contains significant known problems with the LLVM system,
743 listed by component. If you run into a problem, please check the <a
744 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
745 there isn't already one.</p>
747 <!-- ======================================================================= -->
749 <a name="experimental">Experimental features included with this release</a>
754 <p>The following components of this LLVM release are either untested, known to
755 be broken or unreliable, or are in early development. These components should
756 not be relied on, and bugs should not be filed against them, but they may be
757 useful to some people. In particular, if you would like to work on one of these
758 components, please contact us on the <a
759 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
762 <li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ
763 and XCore backends are experimental.</li>
764 <li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets
765 other than darwin and ELF X86 systems.</li>
771 <!-- ======================================================================= -->
773 <a name="x86-be">Known problems with the X86 back-end</a>
779 <li>The X86 backend does not yet support
780 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
781 floating point stack</a>. It supports the 'f' and 't' constraints, but not
783 <li>The X86-64 backend does not yet support the LLVM IR instruction
784 <tt>va_arg</tt>. Currently, front-ends support variadic
785 argument constructs on X86-64 by lowering them manually.</li>
786 <li>Windows x64 (aka Win64) code generator has a few issues.
788 <li>llvm-gcc cannot build the mingw-w64 runtime currently
789 due to lack of support for the 'u' inline assembly
790 constraint and for X87 floating point inline assembly.</li>
791 <li>On mingw-w64, you will see unresolved symbol <tt>__chkstk</tt>
792 due to <a href="http://llvm.org/bugs/show_bug.cgi?id=8919">Bug 8919</a>.
793 It is fixed in <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110321/118499.html">r128206</a>.</li>
794 <li>Miss-aligned MOVDQA might crash your program. It is due to
795 <a href="http://llvm.org/bugs/show_bug.cgi?id=9483">Bug 9483</a>,
796 lack of handling aligned internal globals.</li>
804 <!-- ======================================================================= -->
806 <a name="ppc-be">Known problems with the PowerPC back-end</a>
812 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
813 compilation, and lacks support for debug information.</li>
818 <!-- ======================================================================= -->
820 <a name="arm-be">Known problems with the ARM back-end</a>
826 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
827 processors, thumb programs can crash or produce wrong
828 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
829 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
835 <!-- ======================================================================= -->
837 <a name="sparc-be">Known problems with the SPARC back-end</a>
843 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
844 support the 64-bit SPARC ABI (-m64).</li>
849 <!-- ======================================================================= -->
851 <a name="mips-be">Known problems with the MIPS back-end</a>
857 <li>64-bit MIPS targets are not supported yet.</li>
862 <!-- ======================================================================= -->
864 <a name="alpha-be">Known problems with the Alpha back-end</a>
871 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
872 appropriate nops inserted to ensure restartability.</li>
877 <!-- ======================================================================= -->
879 <a name="c-be">Known problems with the C back-end</a>
884 <p>The C backend has numerous problems and is not being actively maintained.
885 Depending on it for anything serious is not advised.</p>
888 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
889 inline assembly code</a>.</li>
890 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
891 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
892 C++ code compiled with <tt>llc</tt> or native compilers.</li>
893 <li>The C backend does not support all exception handling constructs.</li>
894 <li>The C backend does not support arbitrary precision integers.</li>
900 <!-- ======================================================================= -->
902 <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
907 <p><b>LLVM 3.0 will be the last release of llvm-gcc.</b></p>
909 <p>llvm-gcc is generally very stable for the C family of languages. The only
910 major language feature of GCC not supported by llvm-gcc is the
911 <tt>__builtin_apply</tt> family of builtins. However, some extensions
912 are only supported on some targets. For example, trampolines are only
913 supported on some targets (these are used when you take the address of a
914 nested function).</p>
916 <p>Fortran support generally works, but there are still several unresolved bugs
917 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
918 tools/gfortran component for details. Note that llvm-gcc is missing major
919 Fortran performance work in the frontend and library that went into GCC after
920 4.2. If you are interested in Fortran, we recommend that you consider using
921 <a href="#dragonegg">dragonegg</a> instead.</p>
923 <p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
924 actively maintained. If you are interested in Ada, we recommend that you
925 consider using <a href="#dragonegg">dragonegg</a> instead.</p>
930 <!-- *********************************************************************** -->
932 <a name="additionalinfo">Additional Information</a>
934 <!-- *********************************************************************** -->
938 <p>A wide variety of additional information is available on the <a
939 href="http://llvm.org/">LLVM web page</a>, in particular in the <a
940 href="http://llvm.org/docs/">documentation</a> section. The web page also
941 contains versions of the API documentation which is up-to-date with the
942 Subversion version of the source code.
943 You can access versions of these documents specific to this release by going
944 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
946 <p>If you have any questions or comments about LLVM, please feel free to contact
947 us via the <a href="http://llvm.org/docs/#maillist"> mailing
952 <!-- *********************************************************************** -->
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