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7 <title>LLVM 2.7 Release Notes</title>
11 <div class="doc_title">LLVM 2.7 Release Notes</div>
13 <img align=right src="http://llvm.org/img/DragonSmall.png"
14 width="136" height="136">
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 2.7</a></li>
20 <li><a href="#whatsnew">What's New in LLVM 2.7?</a></li>
21 <li><a href="GettingStarted.html">Installation Instructions</a></li>
22 <li><a href="#portability">Portability and Supported Platforms</a></li>
23 <li><a href="#knownproblems">Known Problems</a></li>
24 <li><a href="#additionalinfo">Additional Information</a></li>
27 <div class="doc_author">
28 <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 2.7
34 <a href="http://llvm.org/releases/2.6/docs/ReleaseNotes.html">LLVM 2.6
35 Release Notes</a>.</h1>
37 <!-- *********************************************************************** -->
38 <div class="doc_section">
39 <a name="intro">Introduction</a>
41 <!-- *********************************************************************** -->
43 <div class="doc_text">
45 <p>This document contains the release notes for the LLVM Compiler
46 Infrastructure, release 2.7. Here we describe the status of LLVM, including
47 major improvements from the previous release and significant known problems.
48 All LLVM releases may be downloaded from the <a
49 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
51 <p>For more information about LLVM, including information about the latest
52 release, please check out the <a href="http://llvm.org/">main LLVM
53 web site</a>. If you have questions or comments, the <a
54 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
55 Mailing List</a> is a good place to send them.</p>
57 <p>Note that if you are reading this file from a Subversion checkout or the
58 main LLVM web page, this document applies to the <i>next</i> release, not the
59 current one. To see the release notes for a specific release, please see the
60 <a href="http://llvm.org/releases/">releases page</a>.</p>
63 <p>FIXME: llvm.org moved to new server, mention new logo, Ted and Doug new code
71 include/llvm/Analysis/LiveValues.h => Dan
72 lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
73 llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
74 ABCD, SCCVN, GEPSplitterPass
76 lib/Transforms/Utils/SSI.cpp -> ABCD depends on it.
80 <!-- Features that need text if they're finished for 2.7:
83 variable debug info for optimized code
84 postalloc scheduler: anti dependence breaking, hazard recognizer?
86 loop dependence analysis
87 ELF Writer? How stable?
88 <li>PostRA scheduler improvements, ARM adoption (David Goodwin).</li>
91 <!-- for announcement email:
95 KLEE web page at klee.llvm.org
96 Many new papers added to /pubs/
100 <!-- *********************************************************************** -->
101 <div class="doc_section">
102 <a name="subproj">Sub-project Status Update</a>
104 <!-- *********************************************************************** -->
106 <div class="doc_text">
108 The LLVM 2.7 distribution currently consists of code from the core LLVM
109 repository (which roughly includes the LLVM optimizers, code generators
110 and supporting tools), the Clang repository and the llvm-gcc repository. In
111 addition to this code, the LLVM Project includes other sub-projects that are in
112 development. Here we include updates on these subprojects.
118 <!--=========================================================================-->
119 <div class="doc_subsection">
120 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
123 <div class="doc_text">
125 <p>The <a href="http://clang.llvm.org/">Clang project</a> is ...</p>
127 <p>In the LLVM 2.7 time-frame, the Clang team has made many improvements:</p>
131 include a link to cxx_compatibility.html
135 <!--=========================================================================-->
136 <div class="doc_subsection">
137 <a name="clangsa">Clang Static Analyzer</a>
140 <div class="doc_text">
142 <p>Previously announced in the 2.4, 2.5, and 2.6 LLVM releases, the Clang project also
143 includes an early stage static source code analysis tool for <a
144 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
145 in C and Objective-C programs. The tool performs checks to find
146 bugs that occur on a specific path within a program.</p>
148 <p>In the LLVM 2.7 time-frame, the analyzer core has sprouted legs and...</p>
152 <!--=========================================================================-->
153 <div class="doc_subsection">
154 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
157 <div class="doc_text">
159 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
160 a JVM and a CLI Virtual Machine (Microsoft .NET is an
161 implementation of the CLI) using LLVM for static and just-in-time
165 VMKit version ?? builds with LLVM 2.7 and you can find it on its
166 <a href="http://vmkit.llvm.org/releases/">web page</a>. The release includes
167 bug fixes, cleanup and new features. The major changes are:</p>
177 <!--=========================================================================-->
178 <div class="doc_subsection">
179 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
182 <div class="doc_text">
184 The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
185 is a simple library that provides an implementation of the low-level
186 target-specific hooks required by code generation and other runtime components.
187 For example, when compiling for a 32-bit target, converting a double to a 64-bit
188 unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
189 function. The compiler-rt library provides highly optimized implementations of
190 this and other low-level routines (some are 3x faster than the equivalent
191 libgcc routines).</p>
194 All of the code in the compiler-rt project is available under the standard LLVM
195 License, a "BSD-style" license.</p>
199 <!--=========================================================================-->
200 <div class="doc_subsection">
201 <a name="klee">KLEE: Symbolic Execution and Automatic Test Case Generator</a>
204 <div class="doc_text">
206 The new LLVM <a href="http://klee.llvm.org/">KLEE project</a> is a symbolic
207 execution framework for programs in LLVM bitcode form. KLEE tries to
208 symbolically evaluate "all" paths through the application and records state
209 transitions that lead to fault states. This allows it to construct testcases
210 that lead to faults and can even be used to verify algorithms. For more
211 details, please see the <a
212 href="http://llvm.org/pubs/2008-12-OSDI-KLEE.html">OSDI 2008 paper</a> about
217 <!--=========================================================================-->
218 <div class="doc_subsection">
219 <a name="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
222 <div class="doc_text">
224 The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
225 gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
226 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (dragonegg.so)
227 that is loaded by gcc at runtime. It ...
233 <!--=========================================================================-->
234 <div class="doc_subsection">
235 <a name="mc">llvm-mc: Machine Code Toolkit</a>
238 <div class="doc_text">
240 The LLVM Machine Code (MC) Toolkit project is ...
246 <!-- *********************************************************************** -->
247 <div class="doc_section">
248 <a name="externalproj">External Open Source Projects Using LLVM 2.7</a>
250 <!-- *********************************************************************** -->
252 <div class="doc_text">
254 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
255 a lot of other language and tools projects. This section lists some of the
256 projects that have already been updated to work with LLVM 2.7.</p>
260 <!--=========================================================================-->
261 <div class="doc_subsection">
262 <a name="Rubinius">Rubinius</a>
265 <div class="doc_text">
268 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
269 for running Ruby code which strives to write as much of the core class
270 implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
271 uses LLVM to optimize and compile ruby code down to machine code. Techniques
272 such as type feedback, method inlining, and uncommon traps are all used to
273 remove dynamism from ruby execution and increase performance.</p>
275 <p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
276 a counter based JIT, type feedback and speculative method inlining.
282 <!--=========================================================================-->
283 <div class="doc_subsection">
284 <a name="macruby">MacRuby</a>
287 <div class="doc_text">
292 <a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
293 core Mac OS X technologies, such as the Objective-C common runtime and garbage
294 collector and the CoreFoundation framework. It is principally developed by
295 Apple and aims at enabling the creation of full-fledged Mac OS X applications.
299 MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
300 expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
306 <!--=========================================================================-->
307 <div class="doc_subsection">
308 <a name="pure">Pure</a>
311 <div class="doc_text">
315 <a href="http://pure-lang.googlecode.com/">Pure</a>
316 is an algebraic/functional programming language based on term rewriting.
317 Programs are collections of equations which are used to evaluate expressions in
318 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
319 lexical closures, a hygienic macro system (also based on term rewriting),
320 built-in list and matrix support (including list and matrix comprehensions) and
321 an easy-to-use C interface. The interpreter uses LLVM as a backend to
322 JIT-compile Pure programs to fast native code.</p>
324 <p>Pure versions ??? and later have been tested and are known to work with
325 LLVM 2.7 (and continue to work with older LLVM releases >= 2.3 as well).
330 <!--=========================================================================-->
331 <div class="doc_subsection">
332 <a name="ldc">LLVM D Compiler</a>
335 <div class="doc_text">
339 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
340 the D Programming Language using the LLVM optimizer and code generator.
341 The LDC project works great with the LLVM 2.6 release. General improvements in
343 cycle have included new inline asm constraint handling, better debug info
344 support, general bug fixes and better x86-64 support. This has allowed
345 some major improvements in LDC, getting it much closer to being as
346 fully featured as the original DMD compiler from DigitalMars.-->
350 <!--=========================================================================-->
351 <div class="doc_subsection">
352 <a name="RoadsendPHP">Roadsend PHP</a>
355 <div class="doc_text">
359 <a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
360 source implementation of the PHP programming
361 language that uses LLVM for its optimizer, JIT and static compiler. This is a
362 reimplementation of an earlier project that is now based on LLVM.
366 <!--=========================================================================-->
367 <div class="doc_subsection">
368 <a name="UnladenSwallow">Unladen Swallow</a>
371 <div class="doc_text">
375 <a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
376 branch of <a href="http://python.org/">Python</a> intended to be fully
377 compatible and significantly faster. It uses LLVM's optimization passes and JIT
382 <!--=========================================================================-->
383 <div class="doc_subsection">
384 <a name="llvm-lua">llvm-lua</a>
387 <div class="doc_text">
391 <a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
392 and static compiling support to the Lua VM. Lua bytecode is analyzed to
393 remove type checks, then LLVM is used to compile the bytecode down to machine
398 <!--=========================================================================-->
399 <div class="doc_subsection">
400 <a name="icedtea">IcedTea Java Virtual Machine Implementation</a>
403 <div class="doc_text">
407 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
408 harness to build OpenJDK using only free software build tools and to provide
409 replacements for the not-yet free parts of OpenJDK. One of the extensions that
410 IcedTea provides is a new JIT compiler named <a
411 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
412 to provide native code generation without introducing processor-dependent
419 <!-- *********************************************************************** -->
420 <div class="doc_section">
421 <a name="whatsnew">What's New in LLVM 2.7?</a>
423 <!-- *********************************************************************** -->
425 <div class="doc_text">
427 <p>This release includes a huge number of bug fixes, performance tweaks and
428 minor improvements. Some of the major improvements and new features are listed
434 <!--=========================================================================-->
435 <div class="doc_subsection">
436 <a name="majorfeatures">Major New Features</a>
439 <div class="doc_text">
441 <p>LLVM 2.7 includes several major new capabilities:</p>
447 Extensible metadata solid.
449 Debug info improvements: using metadata instead of llvm.dbg global variables.
450 This brings several enhancements including improved compile times.
452 New instruction selector.
453 GHC Haskell ABI/ calling conv support.
454 Pre-Alpha support for unions in IR.
455 New InlineHint and StackAlignment function attributes
456 Code generator MC'ized except for debug info and EH.
457 New SCEV AA pass: -scev-aa
458 Inliner reuses arrays allocas when inlining multiple callers to reduce stack usage.
459 MC encoding and disassembler apis.
460 Optimal Edge Profiling?
461 Instcombine is now a library, has its own IRBuilder to simplify itself.
462 New llvm/Support/Regex.h API. FileCheck now does regex's
463 Many subtle pointer invalidation bugs in Callgraph have been fixed and it now uses asserting value handles.
464 MC Disassembler (with blog post), MCInstPrinter. Many X86 backend and AsmPrinter simplifications
465 Various tools like llc and opt now read either .ll or .bc files as input.
466 Malloc and free instructions got removed.
467 compiler-rt support for ARM.
468 completely llvm-gcc NEON support.
469 Can transcode from GAS to intel syntax with "llvm-mc foo.s -output-asm-variant=1"
470 JIT debug information with GDB 7.0
471 New CodeGen Level LICM And CSE (did it make 2.7?)
472 CMake can now run tests, what other improvements?
473 ARM/Thumb register scavenging improvements?
474 New SSAUpdater and MachineSSAUpdater classes for unstructured ssa updating,
475 changed jump threading, GVN, etc to use it which simplified them and speed
478 CondProp pass removed (functionality merged into jump threading).
479 AndersAA got removed (from 2.7 or mainline?)
480 PredSimplify, LoopVR, GVNPRE got removed.
481 LLVM command line tools now overwrite their output, before they would only do this with -f.
482 DOUT removed, use DEBUG(errs() instead.
483 Much stuff converted to use raw_ostream instead of std::ostream.
484 TargetAsmInfo renamed to MCAsmInfo
485 llvm/ADT/iterator.h gone.
490 <!--=========================================================================-->
491 <div class="doc_subsection">
492 <a name="coreimprovements">LLVM IR and Core Improvements</a>
495 <div class="doc_text">
496 <p>LLVM IR has several new features for better support of new targets and that
497 expose new optimization opportunities:</p>
505 <!--=========================================================================-->
506 <div class="doc_subsection">
507 <a name="optimizer">Optimizer Improvements</a>
510 <div class="doc_text">
512 <p>In addition to a large array of minor performance tweaks and bug fixes, this
513 release includes a few major enhancements and additions to the optimizers:</p>
521 <p>Also, -anders-aa was removed</p>
526 <!--=========================================================================-->
527 <div class="doc_subsection">
528 <a name="executionengine">Interpreter and JIT Improvements</a>
531 <div class="doc_text">
535 href="http://llvm.org/viewvc/llvm-project?view=rev&revision=85295">defaults
536 to compiling eagerly</a> to avoid a race condition in the lazy JIT.
537 Clients that still want the lazy JIT can switch it on by calling
538 <tt>ExecutionEngine::DisableLazyCompilation(false)</tt>.</li>
539 <li>It is now possible to create more than one JIT instance in the same process.
540 These JITs can generate machine code in parallel,
541 although <a href="http://llvm.org/docs/ProgrammersManual.html#jitthreading">you
542 still have to obey the other threading restrictions</a>.</li>
547 <!--=========================================================================-->
548 <div class="doc_subsection">
549 <a name="codegen">Target Independent Code Generator Improvements</a>
552 <div class="doc_text">
554 <p>We have put a significant amount of work into the code generator
555 infrastructure, which allows us to implement more aggressive algorithms and make
564 <!--=========================================================================-->
565 <div class="doc_subsection">
566 <a name="x86">X86-32 and X86-64 Target Improvements</a>
569 <div class="doc_text">
570 <p>New features of the X86 target include:
581 <!--=========================================================================-->
582 <div class="doc_subsection">
583 <a name="pic16">PIC16 Target Improvements</a>
586 <div class="doc_text">
587 <p>New features of the PIC16 target include:
594 <p>Things not yet supported:</p>
597 <li>Variable arguments.</li>
598 <li>Interrupts/programs.</li>
603 <!--=========================================================================-->
604 <div class="doc_subsection">
605 <a name="ARM">ARM Target Improvements</a>
608 <div class="doc_text">
609 <p>New features of the ARM target include:
620 <!--=========================================================================-->
621 <div class="doc_subsection">
622 <a name="OtherTarget">Other Target Specific Improvements</a>
625 <div class="doc_text">
626 <p>New features of other targets include:
635 <!--=========================================================================-->
636 <div class="doc_subsection">
637 <a name="newapis">New Useful APIs</a>
640 <div class="doc_text">
642 <p>This release includes a number of new APIs that are used internally, which
643 may also be useful for external clients.
653 <!--=========================================================================-->
654 <div class="doc_subsection">
655 <a name="otherimprovements">Other Improvements and New Features</a>
658 <div class="doc_text">
659 <p>Other miscellaneous features include:</p>
668 <!--=========================================================================-->
669 <div class="doc_subsection">
670 <a name="changes">Major Changes and Removed Features</a>
673 <div class="doc_text">
675 <p>If you're already an LLVM user or developer with out-of-tree changes based
676 on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading
677 from the previous release.</p>
680 <li>The LLVM interpreter now defaults to <em>not</em> using <tt>libffi</tt> even
681 if you have it installed. This makes it more likely that an LLVM built on one
682 system will work when copied to a similar system. To use <tt>libffi</tt>,
683 configure with <tt>--enable-libffi</tt>.
688 <p>In addition, many APIs have changed in this release. Some of the major LLVM
692 <li><tt>ModuleProvider</tt> has been <a
693 href="http://llvm.org/viewvc/llvm-project?view=rev&revision=94686">removed</a>
694 and its methods moved to <tt>Module</tt> and <tt>GlobalValue</tt>.
695 Most clients can remove uses of <tt>ExistingModuleProvider</tt>,
696 replace <tt>getBitcodeModuleProvider</tt> with
697 <tt>getLazyBitcodeModule</tt>, and pass their <tt>Module</tt> to
698 functions that used to accept <tt>ModuleProvider</tt>. Clients who
699 wrote their own <tt>ModuleProvider</tt>s will need to derive from
700 <tt>GVMaterializer</tt> instead and use
701 <tt>Module::setMaterializer</tt> to attach it to a
702 <tt>Module</tt>.</li>
704 <li><tt>GhostLinkage</tt> has given up the ghost.
705 <tt>GlobalValue</tt>s that have not yet been read from their backing
706 storage have the same linkage they will have after being read in.
707 Clients must replace calls to
708 <tt>GlobalValue::hasNotBeenReadFromBitcode</tt> with
709 <tt>GlobalValue::isMaterializable</tt>.</li>
711 <li>FIXME: Debug info has been totally redone. Add pointers to new APIs. Substantial caveats about compatibility of .ll and .bc files.</li>
713 <li>The <tt>llvm/Support/DataTypes.h</tt> header has moved
714 to <tt>llvm/System/DataTypes.h</tt>.</li>
716 <li>The <tt>isInteger</tt>, <tt>isIntOrIntVector</tt>, <tt>isFloatingPoint</tt>,
717 <tt>isFPOrFPVector</tt> and <tt>isFPOrFPVector</tt> methods have been renamed
718 <tt>isIntegerTy</tt>, <tt>isIntOrIntVectorTy</tt>, <tt>isFloatingPointTy</tt>,
719 <tt>isFPOrFPVectorTy</tt> and <tt>isFPOrFPVectorTy</tt> respectively.</li>
726 <!-- *********************************************************************** -->
727 <div class="doc_section">
728 <a name="portability">Portability and Supported Platforms</a>
730 <!-- *********************************************************************** -->
732 <div class="doc_text">
734 <p>LLVM is known to work on the following platforms:</p>
737 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
738 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
740 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
741 and 64-bit modes.</li>
742 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
743 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
744 support is available for native builds with Visual C++).</li>
745 <li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</li>
746 <li>Alpha-based machines running Debian GNU/Linux.</li>
749 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
750 to the machine and operating system on which it is built. However, minor
751 porting may be required to get LLVM to work on new platforms. We welcome your
752 portability patches and reports of successful builds or error messages.</p>
756 <!-- *********************************************************************** -->
757 <div class="doc_section">
758 <a name="knownproblems">Known Problems</a>
760 <!-- *********************************************************************** -->
762 <div class="doc_text">
764 <p>This section contains significant known problems with the LLVM system,
765 listed by component. If you run into a problem, please check the <a
766 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
767 there isn't already one.</p>
770 <li>The llvm-gcc bootstrap will fail with some versions of binutils (e.g. 2.15)
771 with a message of "<tt><a href="http://llvm.org/PR5004">Error: can not do 8
772 byte pc-relative relocation</a></tt>" when building C++ code. We intend to
773 fix this on mainline, but a workaround is to upgrade to binutils 2.17 or
776 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
777 using the stock GCC 3.x.x series 'out the box',
778 See: <a href="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
779 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
780 for x86/x86-64 has been made available from the third party AuroraUX Project
781 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
786 <!-- ======================================================================= -->
787 <div class="doc_subsection">
788 <a name="experimental">Experimental features included with this release</a>
791 <div class="doc_text">
793 <p>The following components of this LLVM release are either untested, known to
794 be broken or unreliable, or are in early development. These components should
795 not be relied on, and bugs should not be filed against them, but they may be
796 useful to some people. In particular, if you would like to work on one of these
797 components, please contact us on the <a
798 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
801 <li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430 and SystemZ backends are
803 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
804 supported value for this option. The MachO writer is experimental, and
805 works much better in mainline SVN.</li>
810 <!-- ======================================================================= -->
811 <div class="doc_subsection">
812 <a name="x86-be">Known problems with the X86 back-end</a>
815 <div class="doc_text">
818 <li>The X86 backend does not yet support
819 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
820 floating point stack</a>. It supports the 'f' and 't' constraints, but not
822 <li>The X86 backend generates inefficient floating point code when configured
823 to generate code for systems that don't have SSE2.</li>
824 <li>Win64 code generation wasn't widely tested. Everything should work, but we
825 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
826 runtime currently due
827 to <a href="http://llvm.org/PR2255">several</a>
828 <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
830 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
831 <li>The X86-64 backend does not yet support the LLVM IR instruction
832 <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
833 argument constructs on X86-64 by lowering them manually.</li>
838 <!-- ======================================================================= -->
839 <div class="doc_subsection">
840 <a name="ppc-be">Known problems with the PowerPC back-end</a>
843 <div class="doc_text">
846 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
847 compilation, and lacks support for debug information.</li>
852 <!-- ======================================================================= -->
853 <div class="doc_subsection">
854 <a name="arm-be">Known problems with the ARM back-end</a>
857 <div class="doc_text">
860 <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
861 and not well tested. Some features may not work at all, and the code quality
862 may be poor in some cases.</li>
863 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
864 processors, thumb programs can crash or produce wrong
865 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
866 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
872 <!-- ======================================================================= -->
873 <div class="doc_subsection">
874 <a name="sparc-be">Known problems with the SPARC back-end</a>
877 <div class="doc_text">
880 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
881 support the 64-bit SPARC ABI (-m64).</li>
886 <!-- ======================================================================= -->
887 <div class="doc_subsection">
888 <a name="mips-be">Known problems with the MIPS back-end</a>
891 <div class="doc_text">
894 <li>64-bit MIPS targets are not supported yet.</li>
899 <!-- ======================================================================= -->
900 <div class="doc_subsection">
901 <a name="alpha-be">Known problems with the Alpha back-end</a>
904 <div class="doc_text">
908 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
909 appropriate nops inserted to ensure restartability.</li>
914 <!-- ======================================================================= -->
915 <div class="doc_subsection">
916 <a name="c-be">Known problems with the C back-end</a>
919 <div class="doc_text">
922 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
923 inline assembly code</a>.</li>
924 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
925 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
926 C++ code compiled with <tt>llc</tt> or native compilers.</li>
927 <li>The C backend does not support all exception handling constructs.</li>
928 <li>The C backend does not support arbitrary precision integers.</li>
934 <!-- ======================================================================= -->
935 <div class="doc_subsection">
936 <a name="c-fe">Known problems with the llvm-gcc C and C++ front-end</a>
939 <div class="doc_text">
941 <p>The only major language feature of GCC not supported by llvm-gcc is
942 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
943 are only supported on some targets. For example, trampolines are only
944 supported on some targets (these are used when you take the address of a
945 nested function).</p>
947 <p>If you run into GCC extensions which are not supported, please let us know.
952 <!-- ======================================================================= -->
953 <div class="doc_subsection">
954 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
957 <div class="doc_text">
959 <li>Fortran support generally works, but there are still several unresolved bugs
960 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
961 tools/gfortran component for details.</li>
965 <!-- ======================================================================= -->
966 <div class="doc_subsection">
967 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
970 <div class="doc_text">
971 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
972 technology, and problems should be expected.
974 <li>The Ada front-end currently only builds on X86-32. This is mainly due
975 to lack of trampoline support (pointers to nested functions) on other platforms.
976 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
977 which does support trampolines.</li>
978 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
979 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
980 exception handling, which is used internally by the compiler.
981 Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
982 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
983 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
984 (c380004 also fails with gcc-4.2 mainline).
985 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
986 causes the compiler to go into an infinite loop, using up all system memory.</li>
987 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
988 <li>The <tt>-E</tt> binder option (exception backtraces)
989 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
990 crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
991 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
992 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
993 or use representation clauses that result in a field of a non-discrete type
994 starting or finishing in the middle of a byte.</li>
995 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
996 'main' as generated by the Ada binder to be invalid</a>.
997 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
998 <tt>envp</tt> rather than integers.</li>
999 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
1004 <!-- ======================================================================= -->
1005 <div class="doc_subsection">
1006 <a name="ocaml-bindings">Known problems with the O'Caml bindings</a>
1009 <div class="doc_text">
1011 <p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
1012 <tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
1013 <tt>Llvm.Linkage.Link_once</tt> will be correct. If you need any of the other linkage
1014 modes, you'll have to write an external C library in order to expose the
1015 functionality. This has been fixed in the trunk.</p>
1018 <!-- *********************************************************************** -->
1019 <div class="doc_section">
1020 <a name="additionalinfo">Additional Information</a>
1022 <!-- *********************************************************************** -->
1024 <div class="doc_text">
1026 <p>A wide variety of additional information is available on the <a
1027 href="http://llvm.org">LLVM web page</a>, in particular in the <a
1028 href="http://llvm.org/docs/">documentation</a> section. The web page also
1029 contains versions of the API documentation which is up-to-date with the
1030 Subversion version of the source code.
1031 You can access versions of these documents specific to this release by going
1032 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
1034 <p>If you have any questions or comments about LLVM, please feel free to contact
1035 us via the <a href="http://llvm.org/docs/#maillist"> mailing
1040 <!-- *********************************************************************** -->
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