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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="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
204 <div class="doc_text">
206 The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
207 gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
208 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (dragonegg.so)
209 that is loaded by gcc at runtime. It ...
215 <!--=========================================================================-->
216 <div class="doc_subsection">
217 <a name="mc">llvm-mc: Machine Code Toolkit</a>
220 <div class="doc_text">
222 The LLVM Machine Code (MC) Toolkit project is ...
228 <!-- *********************************************************************** -->
229 <div class="doc_section">
230 <a name="externalproj">External Open Source Projects Using LLVM 2.7</a>
232 <!-- *********************************************************************** -->
234 <div class="doc_text">
236 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
237 a lot of other language and tools projects. This section lists some of the
238 projects that have already been updated to work with LLVM 2.7.</p>
242 <!--=========================================================================-->
243 <div class="doc_subsection">
244 <a name="Rubinius">Rubinius</a>
247 <div class="doc_text">
250 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
251 for running Ruby code which strives to write as much of the core class
252 implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
253 uses LLVM to optimize and compile ruby code down to machine code. Techniques
254 such as type feedback, method inlining, and uncommon traps are all used to
255 remove dynamism from ruby execution and increase performance.</p>
257 <p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
258 a counter based JIT, type feedback and speculative method inlining.
264 <!--=========================================================================-->
265 <div class="doc_subsection">
266 <a name="macruby">MacRuby</a>
269 <div class="doc_text">
274 <a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
275 core Mac OS X technologies, such as the Objective-C common runtime and garbage
276 collector and the CoreFoundation framework. It is principally developed by
277 Apple and aims at enabling the creation of full-fledged Mac OS X applications.
281 MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
282 expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
288 <!--=========================================================================-->
289 <div class="doc_subsection">
290 <a name="pure">Pure</a>
293 <div class="doc_text">
295 <a href="http://pure-lang.googlecode.com/">Pure</a>
296 is an algebraic/functional programming language based on term rewriting.
297 Programs are collections of equations which are used to evaluate expressions in
298 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
299 lexical closures, a hygienic macro system (also based on term rewriting),
300 built-in list and matrix support (including list and matrix comprehensions) and
301 an easy-to-use C interface. The interpreter uses LLVM as a backend to
302 JIT-compile Pure programs to fast native code.</p>
304 <p>Pure versions 0.43 and later have been tested and are known to work with
305 LLVM 2.7 (and continue to work with older LLVM releases >= 2.5).</p>
310 <!--=========================================================================-->
311 <div class="doc_subsection">
312 <a name="ldc">LLVM D Compiler</a>
315 <div class="doc_text">
319 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
320 the D Programming Language using the LLVM optimizer and code generator.
321 The LDC project works great with the LLVM 2.6 release. General improvements in
323 cycle have included new inline asm constraint handling, better debug info
324 support, general bug fixes and better x86-64 support. This has allowed
325 some major improvements in LDC, getting it much closer to being as
326 fully featured as the original DMD compiler from DigitalMars.-->
330 <!--=========================================================================-->
331 <div class="doc_subsection">
332 <a name="RoadsendPHP">Roadsend PHP</a>
335 <div class="doc_text">
337 <a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
338 source implementation of the PHP programming
339 language that uses LLVM for its optimizer, JIT and static compiler. This is a
340 reimplementation of an earlier project that is now based on LLVM.
344 <!--=========================================================================-->
345 <div class="doc_subsection">
346 <a name="UnladenSwallow">Unladen Swallow</a>
349 <div class="doc_text">
351 <a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
352 branch of <a href="http://python.org/">Python</a> intended to be fully
353 compatible and significantly faster. It uses LLVM's optimization passes and JIT
358 <!--=========================================================================-->
359 <div class="doc_subsection">
360 <a name="llvm-lua">llvm-lua</a>
363 <div class="doc_text">
367 <a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
368 and static compiling support to the Lua VM. Lua bytecode is analyzed to
369 remove type checks, then LLVM is used to compile the bytecode down to machine
374 <!--=========================================================================-->
375 <div class="doc_subsection">
376 <a name="icedtea">IcedTea Java Virtual Machine Implementation</a>
379 <div class="doc_text">
383 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
384 harness to build OpenJDK using only free software build tools and to provide
385 replacements for the not-yet free parts of OpenJDK. One of the extensions that
386 IcedTea provides is a new JIT compiler named <a
387 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
388 to provide native code generation without introducing processor-dependent
395 <!-- *********************************************************************** -->
396 <div class="doc_section">
397 <a name="whatsnew">What's New in LLVM 2.7?</a>
399 <!-- *********************************************************************** -->
401 <div class="doc_text">
403 <p>This release includes a huge number of bug fixes, performance tweaks and
404 minor improvements. Some of the major improvements and new features are listed
410 <!--=========================================================================-->
411 <div class="doc_subsection">
412 <a name="majorfeatures">Major New Features</a>
415 <div class="doc_text">
417 <p>LLVM 2.7 includes several major new capabilities:</p>
423 Extensible metadata solid.
425 Debug info improvements: using metadata instead of llvm.dbg global variables.
426 This brings several enhancements including improved compile times.
428 New instruction selector.
429 GHC Haskell ABI/ calling conv support.
430 Pre-Alpha support for unions in IR.
431 New InlineHint and StackAlignment function attributes
432 Code generator MC'ized except for debug info and EH.
433 New SCEV AA pass: -scev-aa
434 Inliner reuses arrays allocas when inlining multiple callers to reduce stack usage.
435 MC encoding and disassembler apis.
436 Optimal Edge Profiling?
437 Instcombine is now a library, has its own IRBuilder to simplify itself.
438 New llvm/Support/Regex.h API. FileCheck now does regex's
439 Many subtle pointer invalidation bugs in Callgraph have been fixed and it now uses asserting value handles.
440 MC Disassembler (with blog post), MCInstPrinter. Many X86 backend and AsmPrinter simplifications
441 Various tools like llc and opt now read either .ll or .bc files as input.
442 Malloc and free instructions got removed.
443 compiler-rt support for ARM.
444 completely llvm-gcc NEON support.
445 Can transcode from GAS to intel syntax with "llvm-mc foo.s -output-asm-variant=1"
446 JIT debug information with GDB 7.0
447 New CodeGen Level CSE
448 CMake can now run tests, what other improvements?
449 ARM/Thumb using reg scavenging for stack object address materialization (PEI).
450 New SSAUpdater and MachineSSAUpdater classes for unstructured ssa updating,
451 changed jump threading, GVN, etc to use it which simplified them and speed
453 Combiner-AA improvements, why not on by default?
454 Pre-regalloc tail duplication
455 x86 sibcall optimization
456 New LSR with full strength reduction mode
457 The most awesome sext / zext optimization pass. ?
461 CondProp pass removed (functionality merged into jump threading).
462 AndersAA got removed (from 2.7 or mainline?)
463 PredSimplify, LoopVR, GVNPRE got removed.
464 LLVM command line tools now overwrite their output, before they would only do this with -f.
465 DOUT removed, use DEBUG(errs() instead.
466 Much stuff converted to use raw_ostream instead of std::ostream.
467 TargetAsmInfo renamed to MCAsmInfo
468 llvm/ADT/iterator.h gone.
473 <!--=========================================================================-->
474 <div class="doc_subsection">
475 <a name="coreimprovements">LLVM IR and Core Improvements</a>
478 <div class="doc_text">
479 <p>LLVM IR has several new features for better support of new targets and that
480 expose new optimization opportunities:</p>
488 <!--=========================================================================-->
489 <div class="doc_subsection">
490 <a name="optimizer">Optimizer Improvements</a>
493 <div class="doc_text">
495 <p>In addition to a large array of minor performance tweaks and bug fixes, this
496 release includes a few major enhancements and additions to the optimizers:</p>
504 <p>Also, -anders-aa was removed</p>
509 <!--=========================================================================-->
510 <div class="doc_subsection">
511 <a name="executionengine">Interpreter and JIT Improvements</a>
514 <div class="doc_text">
518 href="http://llvm.org/viewvc/llvm-project?view=rev&revision=85295">defaults
519 to compiling eagerly</a> to avoid a race condition in the lazy JIT.
520 Clients that still want the lazy JIT can switch it on by calling
521 <tt>ExecutionEngine::DisableLazyCompilation(false)</tt>.</li>
522 <li>It is now possible to create more than one JIT instance in the same process.
523 These JITs can generate machine code in parallel,
524 although <a href="http://llvm.org/docs/ProgrammersManual.html#jitthreading">you
525 still have to obey the other threading restrictions</a>.</li>
530 <!--=========================================================================-->
531 <div class="doc_subsection">
532 <a name="codegen">Target Independent Code Generator Improvements</a>
535 <div class="doc_text">
537 <p>We have put a significant amount of work into the code generator
538 infrastructure, which allows us to implement more aggressive algorithms and make
547 <!--=========================================================================-->
548 <div class="doc_subsection">
549 <a name="x86">X86-32 and X86-64 Target Improvements</a>
552 <div class="doc_text">
553 <p>New features of the X86 target include:
564 <!--=========================================================================-->
565 <div class="doc_subsection">
566 <a name="pic16">PIC16 Target Improvements</a>
569 <div class="doc_text">
570 <p>New features of the PIC16 target include:
577 <p>Things not yet supported:</p>
580 <li>Variable arguments.</li>
581 <li>Interrupts/programs.</li>
586 <!--=========================================================================-->
587 <div class="doc_subsection">
588 <a name="ARM">ARM Target Improvements</a>
591 <div class="doc_text">
592 <p>New features of the ARM target include:
603 <!--=========================================================================-->
604 <div class="doc_subsection">
605 <a name="OtherTarget">Other Target Specific Improvements</a>
608 <div class="doc_text">
609 <p>New features of other targets include:
618 <!--=========================================================================-->
619 <div class="doc_subsection">
620 <a name="newapis">New Useful APIs</a>
623 <div class="doc_text">
625 <p>This release includes a number of new APIs that are used internally, which
626 may also be useful for external clients.
636 <!--=========================================================================-->
637 <div class="doc_subsection">
638 <a name="otherimprovements">Other Improvements and New Features</a>
641 <div class="doc_text">
642 <p>Other miscellaneous features include:</p>
651 <!--=========================================================================-->
652 <div class="doc_subsection">
653 <a name="changes">Major Changes and Removed Features</a>
656 <div class="doc_text">
658 <p>If you're already an LLVM user or developer with out-of-tree changes based
659 on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading
660 from the previous release.</p>
663 <li>The LLVM interpreter now defaults to <em>not</em> using <tt>libffi</tt> even
664 if you have it installed. This makes it more likely that an LLVM built on one
665 system will work when copied to a similar system. To use <tt>libffi</tt>,
666 configure with <tt>--enable-libffi</tt>.
671 <p>In addition, many APIs have changed in this release. Some of the major LLVM
675 <li><tt>ModuleProvider</tt> has been <a
676 href="http://llvm.org/viewvc/llvm-project?view=rev&revision=94686">removed</a>
677 and its methods moved to <tt>Module</tt> and <tt>GlobalValue</tt>.
678 Most clients can remove uses of <tt>ExistingModuleProvider</tt>,
679 replace <tt>getBitcodeModuleProvider</tt> with
680 <tt>getLazyBitcodeModule</tt>, and pass their <tt>Module</tt> to
681 functions that used to accept <tt>ModuleProvider</tt>. Clients who
682 wrote their own <tt>ModuleProvider</tt>s will need to derive from
683 <tt>GVMaterializer</tt> instead and use
684 <tt>Module::setMaterializer</tt> to attach it to a
685 <tt>Module</tt>.</li>
687 <li><tt>GhostLinkage</tt> has given up the ghost.
688 <tt>GlobalValue</tt>s that have not yet been read from their backing
689 storage have the same linkage they will have after being read in.
690 Clients must replace calls to
691 <tt>GlobalValue::hasNotBeenReadFromBitcode</tt> with
692 <tt>GlobalValue::isMaterializable</tt>.</li>
694 <li>FIXME: Debug info has been totally redone. Add pointers to new APIs. Substantial caveats about compatibility of .ll and .bc files.</li>
696 <li>The <tt>llvm/Support/DataTypes.h</tt> header has moved
697 to <tt>llvm/System/DataTypes.h</tt>.</li>
699 <li>The <tt>isInteger</tt>, <tt>isIntOrIntVector</tt>, <tt>isFloatingPoint</tt>,
700 <tt>isFPOrFPVector</tt> and <tt>isFPOrFPVector</tt> methods have been renamed
701 <tt>isIntegerTy</tt>, <tt>isIntOrIntVectorTy</tt>, <tt>isFloatingPointTy</tt>,
702 <tt>isFPOrFPVectorTy</tt> and <tt>isFPOrFPVectorTy</tt> respectively.</li>
709 <!-- *********************************************************************** -->
710 <div class="doc_section">
711 <a name="portability">Portability and Supported Platforms</a>
713 <!-- *********************************************************************** -->
715 <div class="doc_text">
717 <p>LLVM is known to work on the following platforms:</p>
720 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
721 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
723 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
724 and 64-bit modes.</li>
725 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
726 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
727 support is available for native builds with Visual C++).</li>
728 <li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</li>
729 <li>Alpha-based machines running Debian GNU/Linux.</li>
732 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
733 to the machine and operating system on which it is built. However, minor
734 porting may be required to get LLVM to work on new platforms. We welcome your
735 portability patches and reports of successful builds or error messages.</p>
739 <!-- *********************************************************************** -->
740 <div class="doc_section">
741 <a name="knownproblems">Known Problems</a>
743 <!-- *********************************************************************** -->
745 <div class="doc_text">
747 <p>This section contains significant known problems with the LLVM system,
748 listed by component. If you run into a problem, please check the <a
749 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
750 there isn't already one.</p>
753 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
754 using the stock GCC 3.x.x series 'out the box',
755 See: <a href="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
756 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
757 for x86/x86-64 has been made available from the third party AuroraUX Project
758 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
763 <!-- ======================================================================= -->
764 <div class="doc_subsection">
765 <a name="experimental">Experimental features included with this release</a>
768 <div class="doc_text">
770 <p>The following components of this LLVM release are either untested, known to
771 be broken or unreliable, or are in early development. These components should
772 not be relied on, and bugs should not be filed against them, but they may be
773 useful to some people. In particular, if you would like to work on one of these
774 components, please contact us on the <a
775 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
778 <li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430, SystemZ and MicroBlaze
779 backends are experimental.</li>
780 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
781 supported value for this option. The MachO writer is experimental, and
782 works much better in mainline SVN.</li>
787 <!-- ======================================================================= -->
788 <div class="doc_subsection">
789 <a name="x86-be">Known problems with the X86 back-end</a>
792 <div class="doc_text">
795 <li>The X86 backend does not yet support
796 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
797 floating point stack</a>. It supports the 'f' and 't' constraints, but not
799 <li>The X86 backend generates inefficient floating point code when configured
800 to generate code for systems that don't have SSE2.</li>
801 <li>Win64 code generation wasn't widely tested. Everything should work, but we
802 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
803 runtime currently due
804 to <a href="http://llvm.org/PR2255">several</a>
805 <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
807 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
808 <li>The X86-64 backend does not yet support the LLVM IR instruction
809 <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
810 argument constructs on X86-64 by lowering them manually.</li>
815 <!-- ======================================================================= -->
816 <div class="doc_subsection">
817 <a name="ppc-be">Known problems with the PowerPC back-end</a>
820 <div class="doc_text">
823 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
824 compilation, and lacks support for debug information.</li>
829 <!-- ======================================================================= -->
830 <div class="doc_subsection">
831 <a name="arm-be">Known problems with the ARM back-end</a>
834 <div class="doc_text">
837 <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
838 and not well tested. Some features may not work at all, and the code quality
839 may be poor in some cases.</li>
840 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
841 processors, thumb programs can crash or produce wrong
842 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
843 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
849 <!-- ======================================================================= -->
850 <div class="doc_subsection">
851 <a name="sparc-be">Known problems with the SPARC back-end</a>
854 <div class="doc_text">
857 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
858 support the 64-bit SPARC ABI (-m64).</li>
863 <!-- ======================================================================= -->
864 <div class="doc_subsection">
865 <a name="mips-be">Known problems with the MIPS back-end</a>
868 <div class="doc_text">
871 <li>64-bit MIPS targets are not supported yet.</li>
876 <!-- ======================================================================= -->
877 <div class="doc_subsection">
878 <a name="alpha-be">Known problems with the Alpha back-end</a>
881 <div class="doc_text">
885 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
886 appropriate nops inserted to ensure restartability.</li>
891 <!-- ======================================================================= -->
892 <div class="doc_subsection">
893 <a name="c-be">Known problems with the C back-end</a>
896 <div class="doc_text">
899 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
900 inline assembly code</a>.</li>
901 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
902 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
903 C++ code compiled with <tt>llc</tt> or native compilers.</li>
904 <li>The C backend does not support all exception handling constructs.</li>
905 <li>The C backend does not support arbitrary precision integers.</li>
911 <!-- ======================================================================= -->
912 <div class="doc_subsection">
913 <a name="c-fe">Known problems with the llvm-gcc C and C++ front-end</a>
916 <div class="doc_text">
918 <p>The only major language feature of GCC not supported by llvm-gcc is
919 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
920 are only supported on some targets. For example, trampolines are only
921 supported on some targets (these are used when you take the address of a
922 nested function).</p>
924 <p>If you run into GCC extensions which are not supported, please let us know.
929 <!-- ======================================================================= -->
930 <div class="doc_subsection">
931 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
934 <div class="doc_text">
936 <li>Fortran support generally works, but there are still several unresolved bugs
937 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
938 tools/gfortran component for details.</li>
942 <!-- ======================================================================= -->
943 <div class="doc_subsection">
944 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
947 <div class="doc_text">
948 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
949 technology, and problems should be expected.
951 <li>The Ada front-end currently only builds on X86-32. This is mainly due
952 to lack of trampoline support (pointers to nested functions) on other platforms.
953 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
954 which does support trampolines.</li>
955 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
956 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
957 exception handling, which is used internally by the compiler.
958 Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
959 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
960 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
961 (c380004 also fails with gcc-4.2 mainline).
962 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
963 causes the compiler to go into an infinite loop, using up all system memory.</li>
964 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
965 <li>The <tt>-E</tt> binder option (exception backtraces)
966 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
967 crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
968 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
969 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
970 or use representation clauses that result in a field of a non-discrete type
971 starting or finishing in the middle of a byte.</li>
972 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
973 'main' as generated by the Ada binder to be invalid</a>.
974 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
975 <tt>envp</tt> rather than integers.</li>
976 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
981 <!-- ======================================================================= -->
982 <div class="doc_subsection">
983 <a name="ocaml-bindings">Known problems with the O'Caml bindings</a>
986 <div class="doc_text">
988 <p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
989 <tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
990 <tt>Llvm.Linkage.Link_once</tt> will be correct. If you need any of the other linkage
991 modes, you'll have to write an external C library in order to expose the
992 functionality. This has been fixed in the trunk.</p>
995 <!-- *********************************************************************** -->
996 <div class="doc_section">
997 <a name="additionalinfo">Additional Information</a>
999 <!-- *********************************************************************** -->
1001 <div class="doc_text">
1003 <p>A wide variety of additional information is available on the <a
1004 href="http://llvm.org">LLVM web page</a>, in particular in the <a
1005 href="http://llvm.org/docs/">documentation</a> section. The web page also
1006 contains versions of the API documentation which is up-to-date with the
1007 Subversion version of the source code.
1008 You can access versions of these documents specific to this release by going
1009 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
1011 <p>If you have any questions or comments about LLVM, please feel free to contact
1012 us via the <a href="http://llvm.org/docs/#maillist"> mailing
1017 <!-- *********************************************************************** -->
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