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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>
130 <li>FIXME: C++! Include a link to cxx_compatibility.html</li>
132 <li>FIXME: Static Analyzer improvements?</li>
134 <li>CIndex API and Python bindings: Clang now includes a C API as part of the
135 CIndex library. Although we make make some changes to the API in the future, it
136 is intended to be stable and has been designed for use by external projects. See
138 doxygen <a href="http://clang.llvm.org/doxygen/group__CINDEX.html">CIndex</a>
139 documentation for more details. The CIndex API also includings an preliminary
140 set of Python bindings.</li>
142 <li>ARM Support: Clang now has ABI support for both the Darwin and Linux ARM
143 ABIs. Coupled with many improvements to the LLVM ARM backend, Clang is now
144 suitable for use as a a beta quality ARM compiler.</li>
148 <!--=========================================================================-->
149 <div class="doc_subsection">
150 <a name="clangsa">Clang Static Analyzer</a>
153 <div class="doc_text">
155 <p>Previously announced in the 2.4, 2.5, and 2.6 LLVM releases, the Clang project also
156 includes an early stage static source code analysis tool for <a
157 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
158 in C and Objective-C programs. The tool performs checks to find
159 bugs that occur on a specific path within a program.</p>
161 <p>In the LLVM 2.7 time-frame, the analyzer core has sprouted legs and...</p>
165 <!--=========================================================================-->
166 <div class="doc_subsection">
167 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
170 <div class="doc_text">
172 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
173 a JVM and a CLI Virtual Machine (Microsoft .NET is an
174 implementation of the CLI) using LLVM for static and just-in-time
178 VMKit version ?? builds with LLVM 2.7 and you can find it on its
179 <a href="http://vmkit.llvm.org/releases/">web page</a>. The release includes
180 bug fixes, cleanup and new features. The major changes are:</p>
190 <!--=========================================================================-->
191 <div class="doc_subsection">
192 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
195 <div class="doc_text">
197 The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
198 is a simple library that provides an implementation of the low-level
199 target-specific hooks required by code generation and other runtime components.
200 For example, when compiling for a 32-bit target, converting a double to a 64-bit
201 unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
202 function. The compiler-rt library provides highly optimized implementations of
203 this and other low-level routines (some are 3x faster than the equivalent
204 libgcc routines).</p>
207 All of the code in the compiler-rt project is available under the standard LLVM
208 License, a "BSD-style" license.</p>
212 <!--=========================================================================-->
213 <div class="doc_subsection">
214 <a name="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
217 <div class="doc_text">
219 The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
220 gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
221 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (dragonegg.so)
222 that is loaded by gcc at runtime. It ...
228 <!--=========================================================================-->
229 <div class="doc_subsection">
230 <a name="mc">llvm-mc: Machine Code Toolkit</a>
233 <div class="doc_text">
235 The LLVM Machine Code (MC) Toolkit project is ...
241 <!-- *********************************************************************** -->
242 <div class="doc_section">
243 <a name="externalproj">External Open Source Projects Using LLVM 2.7</a>
245 <!-- *********************************************************************** -->
247 <div class="doc_text">
249 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
250 a lot of other language and tools projects. This section lists some of the
251 projects that have already been updated to work with LLVM 2.7.</p>
255 <!--=========================================================================-->
256 <div class="doc_subsection">
257 <a name="Rubinius">Rubinius</a>
260 <div class="doc_text">
263 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
264 for running Ruby code which strives to write as much of the core class
265 implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
266 uses LLVM to optimize and compile ruby code down to machine code. Techniques
267 such as type feedback, method inlining, and uncommon traps are all used to
268 remove dynamism from ruby execution and increase performance.</p>
270 <p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
271 a counter based JIT, type feedback and speculative method inlining.
277 <!--=========================================================================-->
278 <div class="doc_subsection">
279 <a name="macruby">MacRuby</a>
282 <div class="doc_text">
287 <a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
288 core Mac OS X technologies, such as the Objective-C common runtime and garbage
289 collector and the CoreFoundation framework. It is principally developed by
290 Apple and aims at enabling the creation of full-fledged Mac OS X applications.
294 MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
295 expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
301 <!--=========================================================================-->
302 <div class="doc_subsection">
303 <a name="pure">Pure</a>
306 <div class="doc_text">
308 <a href="http://pure-lang.googlecode.com/">Pure</a>
309 is an algebraic/functional programming language based on term rewriting.
310 Programs are collections of equations which are used to evaluate expressions in
311 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
312 lexical closures, a hygienic macro system (also based on term rewriting),
313 built-in list and matrix support (including list and matrix comprehensions) and
314 an easy-to-use C interface. The interpreter uses LLVM as a backend to
315 JIT-compile Pure programs to fast native code.</p>
317 <p>Pure versions 0.43 and later have been tested and are known to work with
318 LLVM 2.7 (and continue to work with older LLVM releases >= 2.5).</p>
323 <!--=========================================================================-->
324 <div class="doc_subsection">
325 <a name="ldc">LLVM D Compiler</a>
328 <div class="doc_text">
332 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
333 the D Programming Language using the LLVM optimizer and code generator.
334 The LDC project works great with the LLVM 2.6 release. General improvements in
336 cycle have included new inline asm constraint handling, better debug info
337 support, general bug fixes and better x86-64 support. This has allowed
338 some major improvements in LDC, getting it much closer to being as
339 fully featured as the original DMD compiler from DigitalMars.-->
343 <!--=========================================================================-->
344 <div class="doc_subsection">
345 <a name="RoadsendPHP">Roadsend PHP</a>
348 <div class="doc_text">
350 <a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
351 source implementation of the PHP programming
352 language that uses LLVM for its optimizer, JIT and static compiler. This is a
353 reimplementation of an earlier project that is now based on LLVM.
357 <!--=========================================================================-->
358 <div class="doc_subsection">
359 <a name="UnladenSwallow">Unladen Swallow</a>
362 <div class="doc_text">
364 <a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
365 branch of <a href="http://python.org/">Python</a> intended to be fully
366 compatible and significantly faster. It uses LLVM's optimization passes and JIT
371 <!--=========================================================================-->
372 <div class="doc_subsection">
373 <a name="llvm-lua">llvm-lua</a>
376 <div class="doc_text">
380 <a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
381 and static compiling support to the Lua VM. Lua bytecode is analyzed to
382 remove type checks, then LLVM is used to compile the bytecode down to machine
387 <!--=========================================================================-->
388 <div class="doc_subsection">
389 <a name="icedtea">IcedTea Java Virtual Machine Implementation</a>
392 <div class="doc_text">
396 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
397 harness to build OpenJDK using only free software build tools and to provide
398 replacements for the not-yet free parts of OpenJDK. One of the extensions that
399 IcedTea provides is a new JIT compiler named <a
400 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
401 to provide native code generation without introducing processor-dependent
408 <!-- *********************************************************************** -->
409 <div class="doc_section">
410 <a name="whatsnew">What's New in LLVM 2.7?</a>
412 <!-- *********************************************************************** -->
414 <div class="doc_text">
416 <p>This release includes a huge number of bug fixes, performance tweaks and
417 minor improvements. Some of the major improvements and new features are listed
423 <!--=========================================================================-->
424 <div class="doc_subsection">
425 <a name="majorfeatures">Major New Features</a>
428 <div class="doc_text">
430 <p>LLVM 2.7 includes several major new capabilities:</p>
436 Extensible metadata solid.
438 Debug info improvements: using metadata instead of llvm.dbg global variables.
439 This brings several enhancements including improved compile times.
441 New instruction selector.
442 GHC Haskell ABI/ calling conv support.
443 Pre-Alpha support for unions in IR.
444 New InlineHint and StackAlignment function attributes
445 Code generator MC'ized except for debug info and EH.
446 New SCEV AA pass: -scev-aa
447 Inliner reuses arrays allocas when inlining multiple callers to reduce stack usage.
448 MC encoding and disassembler apis.
449 Optimal Edge Profiling?
450 Instcombine is now a library, has its own IRBuilder to simplify itself.
451 New llvm/Support/Regex.h API. FileCheck now does regex's
452 Many subtle pointer invalidation bugs in Callgraph have been fixed and it now uses asserting value handles.
453 MC Disassembler (with blog post), MCInstPrinter. Many X86 backend and AsmPrinter simplifications
454 Various tools like llc and opt now read either .ll or .bc files as input.
455 Malloc and free instructions got removed.
456 compiler-rt support for ARM.
457 completely llvm-gcc NEON support.
458 Can transcode from GAS to intel syntax with "llvm-mc foo.s -output-asm-variant=1"
459 JIT debug information with GDB 7.0
460 New CodeGen Level CSE
461 CMake can now run tests, what other improvements?
462 ARM/Thumb using reg scavenging for stack object address materialization (PEI).
463 New SSAUpdater and MachineSSAUpdater classes for unstructured ssa updating,
464 changed jump threading, GVN, etc to use it which simplified them and speed
466 Combiner-AA improvements, why not on by default?
467 Pre-regalloc tail duplication
468 x86 sibcall optimization
469 New LSR with full strength reduction mode
470 The most awesome sext / zext optimization pass. ?
474 CondProp pass removed (functionality merged into jump threading).
475 AndersAA got removed (from 2.7 or mainline?)
476 PredSimplify, LoopVR, GVNPRE got removed.
477 LLVM command line tools now overwrite their output, before they would only do this with -f.
478 DOUT removed, use DEBUG(errs() instead.
479 Much stuff converted to use raw_ostream instead of std::ostream.
480 TargetAsmInfo renamed to MCAsmInfo
481 llvm/ADT/iterator.h gone.
486 <!--=========================================================================-->
487 <div class="doc_subsection">
488 <a name="coreimprovements">LLVM IR and Core Improvements</a>
491 <div class="doc_text">
492 <p>LLVM IR has several new features for better support of new targets and that
493 expose new optimization opportunities:</p>
501 <!--=========================================================================-->
502 <div class="doc_subsection">
503 <a name="optimizer">Optimizer Improvements</a>
506 <div class="doc_text">
508 <p>In addition to a large array of minor performance tweaks and bug fixes, this
509 release includes a few major enhancements and additions to the optimizers:</p>
517 <p>Also, -anders-aa was removed</p>
522 <!--=========================================================================-->
523 <div class="doc_subsection">
524 <a name="executionengine">Interpreter and JIT Improvements</a>
527 <div class="doc_text">
531 href="http://llvm.org/viewvc/llvm-project?view=rev&revision=85295">defaults
532 to compiling eagerly</a> to avoid a race condition in the lazy JIT.
533 Clients that still want the lazy JIT can switch it on by calling
534 <tt>ExecutionEngine::DisableLazyCompilation(false)</tt>.</li>
535 <li>It is now possible to create more than one JIT instance in the same process.
536 These JITs can generate machine code in parallel,
537 although <a href="http://llvm.org/docs/ProgrammersManual.html#jitthreading">you
538 still have to obey the other threading restrictions</a>.</li>
543 <!--=========================================================================-->
544 <div class="doc_subsection">
545 <a name="codegen">Target Independent Code Generator Improvements</a>
548 <div class="doc_text">
550 <p>We have put a significant amount of work into the code generator
551 infrastructure, which allows us to implement more aggressive algorithms and make
560 <!--=========================================================================-->
561 <div class="doc_subsection">
562 <a name="x86">X86-32 and X86-64 Target Improvements</a>
565 <div class="doc_text">
566 <p>New features of the X86 target include:
577 <!--=========================================================================-->
578 <div class="doc_subsection">
579 <a name="pic16">PIC16 Target Improvements</a>
582 <div class="doc_text">
583 <p>New features of the PIC16 target include:
590 <p>Things not yet supported:</p>
593 <li>Variable arguments.</li>
594 <li>Interrupts/programs.</li>
599 <!--=========================================================================-->
600 <div class="doc_subsection">
601 <a name="ARM">ARM Target Improvements</a>
604 <div class="doc_text">
605 <p>New features of the ARM target include:
616 <!--=========================================================================-->
617 <div class="doc_subsection">
618 <a name="OtherTarget">Other Target Specific Improvements</a>
621 <div class="doc_text">
622 <p>New features of other targets include:
631 <!--=========================================================================-->
632 <div class="doc_subsection">
633 <a name="newapis">New Useful APIs</a>
636 <div class="doc_text">
638 <p>This release includes a number of new APIs that are used internally, which
639 may also be useful for external clients.
649 <!--=========================================================================-->
650 <div class="doc_subsection">
651 <a name="otherimprovements">Other Improvements and New Features</a>
654 <div class="doc_text">
655 <p>Other miscellaneous features include:</p>
664 <!--=========================================================================-->
665 <div class="doc_subsection">
666 <a name="changes">Major Changes and Removed Features</a>
669 <div class="doc_text">
671 <p>If you're already an LLVM user or developer with out-of-tree changes based
672 on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading
673 from the previous release.</p>
676 <li>The LLVM interpreter now defaults to <em>not</em> using <tt>libffi</tt> even
677 if you have it installed. This makes it more likely that an LLVM built on one
678 system will work when copied to a similar system. To use <tt>libffi</tt>,
679 configure with <tt>--enable-libffi</tt>.
684 <p>In addition, many APIs have changed in this release. Some of the major LLVM
688 <li><tt>ModuleProvider</tt> has been <a
689 href="http://llvm.org/viewvc/llvm-project?view=rev&revision=94686">removed</a>
690 and its methods moved to <tt>Module</tt> and <tt>GlobalValue</tt>.
691 Most clients can remove uses of <tt>ExistingModuleProvider</tt>,
692 replace <tt>getBitcodeModuleProvider</tt> with
693 <tt>getLazyBitcodeModule</tt>, and pass their <tt>Module</tt> to
694 functions that used to accept <tt>ModuleProvider</tt>. Clients who
695 wrote their own <tt>ModuleProvider</tt>s will need to derive from
696 <tt>GVMaterializer</tt> instead and use
697 <tt>Module::setMaterializer</tt> to attach it to a
698 <tt>Module</tt>.</li>
700 <li><tt>GhostLinkage</tt> has given up the ghost.
701 <tt>GlobalValue</tt>s that have not yet been read from their backing
702 storage have the same linkage they will have after being read in.
703 Clients must replace calls to
704 <tt>GlobalValue::hasNotBeenReadFromBitcode</tt> with
705 <tt>GlobalValue::isMaterializable</tt>.</li>
707 <li>FIXME: Debug info has been totally redone. Add pointers to new APIs. Substantial caveats about compatibility of .ll and .bc files.</li>
709 <li>The <tt>llvm/Support/DataTypes.h</tt> header has moved
710 to <tt>llvm/System/DataTypes.h</tt>.</li>
712 <li>The <tt>isInteger</tt>, <tt>isIntOrIntVector</tt>, <tt>isFloatingPoint</tt>,
713 <tt>isFPOrFPVector</tt> and <tt>isFPOrFPVector</tt> methods have been renamed
714 <tt>isIntegerTy</tt>, <tt>isIntOrIntVectorTy</tt>, <tt>isFloatingPointTy</tt>,
715 <tt>isFPOrFPVectorTy</tt> and <tt>isFPOrFPVectorTy</tt> respectively.</li>
722 <!-- *********************************************************************** -->
723 <div class="doc_section">
724 <a name="portability">Portability and Supported Platforms</a>
726 <!-- *********************************************************************** -->
728 <div class="doc_text">
730 <p>LLVM is known to work on the following platforms:</p>
733 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
734 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
736 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
737 and 64-bit modes.</li>
738 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
739 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
740 support is available for native builds with Visual C++).</li>
741 <li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</li>
742 <li>Alpha-based machines running Debian GNU/Linux.</li>
745 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
746 to the machine and operating system on which it is built. However, minor
747 porting may be required to get LLVM to work on new platforms. We welcome your
748 portability patches and reports of successful builds or error messages.</p>
752 <!-- *********************************************************************** -->
753 <div class="doc_section">
754 <a name="knownproblems">Known Problems</a>
756 <!-- *********************************************************************** -->
758 <div class="doc_text">
760 <p>This section contains significant known problems with the LLVM system,
761 listed by component. If you run into a problem, please check the <a
762 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
763 there isn't already one.</p>
766 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
767 using the stock GCC 3.x.x series 'out the box',
768 See: <a href="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
769 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
770 for x86/x86-64 has been made available from the third party AuroraUX Project
771 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
776 <!-- ======================================================================= -->
777 <div class="doc_subsection">
778 <a name="experimental">Experimental features included with this release</a>
781 <div class="doc_text">
783 <p>The following components of this LLVM release are either untested, known to
784 be broken or unreliable, or are in early development. These components should
785 not be relied on, and bugs should not be filed against them, but they may be
786 useful to some people. In particular, if you would like to work on one of these
787 components, please contact us on the <a
788 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
791 <li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430, SystemZ and MicroBlaze
792 backends are experimental.</li>
793 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
794 supported value for this option. The MachO writer is experimental, and
795 works much better in mainline SVN.</li>
800 <!-- ======================================================================= -->
801 <div class="doc_subsection">
802 <a name="x86-be">Known problems with the X86 back-end</a>
805 <div class="doc_text">
808 <li>The X86 backend does not yet support
809 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
810 floating point stack</a>. It supports the 'f' and 't' constraints, but not
812 <li>The X86 backend generates inefficient floating point code when configured
813 to generate code for systems that don't have SSE2.</li>
814 <li>Win64 code generation wasn't widely tested. Everything should work, but we
815 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
816 runtime currently due
817 to <a href="http://llvm.org/PR2255">several</a>
818 <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
820 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
821 <li>The X86-64 backend does not yet support the LLVM IR instruction
822 <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
823 argument constructs on X86-64 by lowering them manually.</li>
828 <!-- ======================================================================= -->
829 <div class="doc_subsection">
830 <a name="ppc-be">Known problems with the PowerPC back-end</a>
833 <div class="doc_text">
836 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
837 compilation, and lacks support for debug information.</li>
842 <!-- ======================================================================= -->
843 <div class="doc_subsection">
844 <a name="arm-be">Known problems with the ARM back-end</a>
847 <div class="doc_text">
850 <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
851 and not well tested. Some features may not work at all, and the code quality
852 may be poor in some cases.</li>
853 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
854 processors, thumb programs can crash or produce wrong
855 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
856 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
862 <!-- ======================================================================= -->
863 <div class="doc_subsection">
864 <a name="sparc-be">Known problems with the SPARC back-end</a>
867 <div class="doc_text">
870 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
871 support the 64-bit SPARC ABI (-m64).</li>
876 <!-- ======================================================================= -->
877 <div class="doc_subsection">
878 <a name="mips-be">Known problems with the MIPS back-end</a>
881 <div class="doc_text">
884 <li>64-bit MIPS targets are not supported yet.</li>
889 <!-- ======================================================================= -->
890 <div class="doc_subsection">
891 <a name="alpha-be">Known problems with the Alpha back-end</a>
894 <div class="doc_text">
898 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
899 appropriate nops inserted to ensure restartability.</li>
904 <!-- ======================================================================= -->
905 <div class="doc_subsection">
906 <a name="c-be">Known problems with the C back-end</a>
909 <div class="doc_text">
912 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
913 inline assembly code</a>.</li>
914 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
915 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
916 C++ code compiled with <tt>llc</tt> or native compilers.</li>
917 <li>The C backend does not support all exception handling constructs.</li>
918 <li>The C backend does not support arbitrary precision integers.</li>
924 <!-- ======================================================================= -->
925 <div class="doc_subsection">
926 <a name="c-fe">Known problems with the llvm-gcc C and C++ front-end</a>
929 <div class="doc_text">
931 <p>The only major language feature of GCC not supported by llvm-gcc is
932 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
933 are only supported on some targets. For example, trampolines are only
934 supported on some targets (these are used when you take the address of a
935 nested function).</p>
937 <p>If you run into GCC extensions which are not supported, please let us know.
942 <!-- ======================================================================= -->
943 <div class="doc_subsection">
944 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
947 <div class="doc_text">
949 <li>Fortran support generally works, but there are still several unresolved bugs
950 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
951 tools/gfortran component for details.</li>
955 <!-- ======================================================================= -->
956 <div class="doc_subsection">
957 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
960 <div class="doc_text">
961 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
962 technology, and problems should be expected.
964 <li>The Ada front-end currently only builds on X86-32. This is mainly due
965 to lack of trampoline support (pointers to nested functions) on other platforms.
966 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
967 which does support trampolines.</li>
968 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
969 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
970 exception handling, which is used internally by the compiler.
971 Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
972 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
973 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
974 (c380004 also fails with gcc-4.2 mainline).
975 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
976 causes the compiler to go into an infinite loop, using up all system memory.</li>
977 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
978 <li>The <tt>-E</tt> binder option (exception backtraces)
979 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
980 crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
981 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
982 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
983 or use representation clauses that result in a field of a non-discrete type
984 starting or finishing in the middle of a byte.</li>
985 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
986 'main' as generated by the Ada binder to be invalid</a>.
987 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
988 <tt>envp</tt> rather than integers.</li>
989 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
994 <!-- ======================================================================= -->
995 <div class="doc_subsection">
996 <a name="ocaml-bindings">Known problems with the O'Caml bindings</a>
999 <div class="doc_text">
1001 <p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
1002 <tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
1003 <tt>Llvm.Linkage.Link_once</tt> will be correct. If you need any of the other linkage
1004 modes, you'll have to write an external C library in order to expose the
1005 functionality. This has been fixed in the trunk.</p>
1008 <!-- *********************************************************************** -->
1009 <div class="doc_section">
1010 <a name="additionalinfo">Additional Information</a>
1012 <!-- *********************************************************************** -->
1014 <div class="doc_text">
1016 <p>A wide variety of additional information is available on the <a
1017 href="http://llvm.org">LLVM web page</a>, in particular in the <a
1018 href="http://llvm.org/docs/">documentation</a> section. The web page also
1019 contains versions of the API documentation which is up-to-date with the
1020 Subversion version of the source code.
1021 You can access versions of these documents specific to this release by going
1022 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
1024 <p>If you have any questions or comments about LLVM, please feel free to contact
1025 us via the <a href="http://llvm.org/docs/#maillist"> mailing
1030 <!-- *********************************************************************** -->
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