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7 <title>LLVM 2.7 Release Notes</title>
11 <div class="doc_title">LLVM 2.7 Release Notes</div>
14 <li><a href="#intro">Introduction</a></li>
15 <li><a href="#subproj">Sub-project Status Update</a></li>
16 <li><a href="#externalproj">External Projects Using LLVM 2.7</a></li>
17 <li><a href="#whatsnew">What's New in LLVM 2.7?</a></li>
18 <li><a href="GettingStarted.html">Installation Instructions</a></li>
19 <li><a href="#portability">Portability and Supported Platforms</a></li>
20 <li><a href="#knownproblems">Known Problems</a></li>
21 <li><a href="#additionalinfo">Additional Information</a></li>
24 <div class="doc_author">
25 <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
28 <h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.7
31 <a href="http://llvm.org/releases/2.6/docs/ReleaseNotes.html">LLVM 2.6
32 Release Notes</a>.</h1>
34 <!-- *********************************************************************** -->
35 <div class="doc_section">
36 <a name="intro">Introduction</a>
38 <!-- *********************************************************************** -->
40 <div class="doc_text">
42 <p>This document contains the release notes for the LLVM Compiler
43 Infrastructure, release 2.7. Here we describe the status of LLVM, including
44 major improvements from the previous release and significant known problems.
45 All LLVM releases may be downloaded from the <a
46 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
48 <p>For more information about LLVM, including information about the latest
49 release, please check out the <a href="http://llvm.org/">main LLVM
50 web site</a>. If you have questions or comments, the <a
51 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
52 List</a> is a good place to send them.</p>
54 <p>Note that if you are reading this file from a Subversion checkout or the
55 main LLVM web page, this document applies to the <i>next</i> release, not the
56 current one. To see the release notes for a specific release, please see the
57 <a href="http://llvm.org/releases/">releases page</a>.</p>
64 include/llvm/Analysis/LiveValues.h => Dan
65 lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
66 llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
67 ABCD, SCCVN, GEPSplitterPass
72 <!-- Features that need text if they're finished for 2.7:
75 variable debug info for optimized code
76 postalloc scheduler: anti dependence breaking, hazard recognizer?
78 loop dependence analysis
79 ELF Writer? How stable?
80 <li>PostRA scheduler improvements, ARM adoption (David Goodwin).</li>
81 2.7 supports the GDB 7.0 jit interfaces for debug info.
82 2.7 eliminates ADT/iterator.h
85 <!-- for announcement email:
89 KLEE web page at klee.llvm.org
90 Many new papers added to /pubs/
95 <!-- *********************************************************************** -->
96 <div class="doc_section">
97 <a name="subproj">Sub-project Status Update</a>
99 <!-- *********************************************************************** -->
101 <div class="doc_text">
103 The LLVM 2.7 distribution currently consists of code from the core LLVM
104 repository (which roughly includes the LLVM optimizers, code generators
105 and supporting tools), the Clang repository and the llvm-gcc repository. In
106 addition to this code, the LLVM Project includes other sub-projects that are in
107 development. Here we include updates on these subprojects.
113 <!--=========================================================================-->
114 <div class="doc_subsection">
115 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
118 <div class="doc_text">
120 <p>The <a href="http://clang.llvm.org/">Clang project</a> is ...</p>
122 <p>In the LLVM 2.7 time-frame, the Clang team has made many improvements:</p>
129 <!--=========================================================================-->
130 <div class="doc_subsection">
131 <a name="clangsa">Clang Static Analyzer</a>
134 <div class="doc_text">
136 <p>Previously announced in the 2.4, 2.5, and 2.6 LLVM releases, the Clang project also
137 includes an early stage static source code analysis tool for <a
138 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
139 in C and Objective-C programs. The tool performs checks to find
140 bugs that occur on a specific path within a program.</p>
142 <p>In the LLVM 2.7 time-frame, the analyzer core has ...</p>
146 <!--=========================================================================-->
147 <div class="doc_subsection">
148 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
151 <div class="doc_text">
153 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
154 a JVM and a CLI Virtual Machine (Microsoft .NET is an
155 implementation of the CLI) using LLVM for static and just-in-time
159 VMKit version ?? builds with LLVM 2.7 and you can find it on its
160 <a href="http://vmkit.llvm.org/releases/">web page</a>. The release includes
161 bug fixes, cleanup and new features. The major changes are:</p>
171 <!--=========================================================================-->
172 <div class="doc_subsection">
173 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
176 <div class="doc_text">
178 The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
179 is a simple library that provides an implementation of the low-level
180 target-specific hooks required by code generation and other runtime components.
181 For example, when compiling for a 32-bit target, converting a double to a 64-bit
182 unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
183 function. The compiler-rt library provides highly optimized implementations of
184 this and other low-level routines (some are 3x faster than the equivalent
185 libgcc routines).</p>
188 All of the code in the compiler-rt project is available under the standard LLVM
189 License, a "BSD-style" license.</p>
193 <!--=========================================================================-->
194 <div class="doc_subsection">
195 <a name="klee">KLEE: Symbolic Execution and Automatic Test Case Generator</a>
198 <div class="doc_text">
200 The new LLVM <a href="http://klee.llvm.org/">KLEE project</a> is a symbolic
201 execution framework for programs in LLVM bitcode form. KLEE tries to
202 symbolically evaluate "all" paths through the application and records state
203 transitions that lead to fault states. This allows it to construct testcases
204 that lead to faults and can even be used to verify algorithms. For more
205 details, please see the <a
206 href="http://llvm.org/pubs/2008-12-OSDI-KLEE.html">OSDI 2008 paper</a> about
211 <!--=========================================================================-->
212 <div class="doc_subsection">
213 <a name="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
216 <div class="doc_text">
218 The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
219 gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
220 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (dragonegg.so)
221 that is loaded by gcc at runtime. It ...
227 <!--=========================================================================-->
228 <div class="doc_subsection">
229 <a name="mc">llvm-mc: Machine Code Toolkit</a>
232 <div class="doc_text">
234 The LLVM Machine Code (MC) Toolkit project is ...
240 <!-- *********************************************************************** -->
241 <div class="doc_section">
242 <a name="externalproj">External Open Source Projects Using LLVM 2.7</a>
244 <!-- *********************************************************************** -->
246 <div class="doc_text">
248 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
249 a lot of other language and tools projects. This section lists some of the
250 projects that have already been updated to work with LLVM 2.7.</p>
254 <!--=========================================================================-->
255 <div class="doc_subsection">
256 <a name="Rubinius">Rubinius</a>
259 <div class="doc_text">
260 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
261 for running Ruby code which strives to write as much of the core class
262 implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
263 uses LLVM to optimize and compile ruby code down to machine code. Techniques
264 such as type feedback, method inlining, and uncommon traps are all used to
265 remove dynamism from ruby execution and increase performance.</p>
267 <p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
268 a counter based JIT, type feedback and speculative method inlining.
273 <!--=========================================================================-->
274 <div class="doc_subsection">
275 <a name="macruby">MacRuby</a>
278 <div class="doc_text">
281 <a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
282 core Mac OS X technologies, such as the Objective-C common runtime and garbage
283 collector and the CoreFoundation framework. It is principally developed by
284 Apple and aims at enabling the creation of full-fledged Mac OS X applications.
288 MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
289 expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
295 <!--=========================================================================-->
296 <div class="doc_subsection">
297 <a name="pure">Pure</a>
300 <div class="doc_text">
302 <a href="http://pure-lang.googlecode.com/">Pure</a>
303 is an algebraic/functional programming language based on term rewriting.
304 Programs are collections of equations which are used to evaluate expressions in
305 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
306 lexical closures, a hygienic macro system (also based on term rewriting),
307 built-in list and matrix support (including list and matrix comprehensions) and
308 an easy-to-use C interface. The interpreter uses LLVM as a backend to
309 JIT-compile Pure programs to fast native code.</p>
311 <p>Pure versions ??? and later have been tested and are known to work with
312 LLVM 2.7 (and continue to work with older LLVM releases >= 2.3 as well).
317 <!--=========================================================================-->
318 <div class="doc_subsection">
319 <a name="ldc">LLVM D Compiler</a>
322 <div class="doc_text">
324 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
325 the D Programming Language using the LLVM optimizer and code generator.
326 The LDC project works great with the LLVM 2.6 release. General improvements in
328 cycle have included new inline asm constraint handling, better debug info
329 support, general bug fixes and better x86-64 support. This has allowed
330 some major improvements in LDC, getting it much closer to being as
331 fully featured as the original DMD compiler from DigitalMars.
335 <!--=========================================================================-->
336 <div class="doc_subsection">
337 <a name="RoadsendPHP">Roadsend PHP</a>
340 <div class="doc_text">
342 <a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
343 source implementation of the PHP programming
344 language that uses LLVM for its optimizer, JIT and static compiler. This is a
345 reimplementation of an earlier project that is now based on LLVM.</p>
348 <!--=========================================================================-->
349 <div class="doc_subsection">
350 <a name="UnladenSwallow">Unladen Swallow</a>
353 <div class="doc_text">
355 <a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
356 branch of <a href="http://python.org/">Python</a> intended to be fully
357 compatible and significantly faster. It uses LLVM's optimization passes and JIT
361 <!--=========================================================================-->
362 <div class="doc_subsection">
363 <a name="llvm-lua">llvm-lua</a>
366 <div class="doc_text">
368 <a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
369 and static compiling support to the Lua VM. Lua bytecode is analyzed to
370 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">
381 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
382 harness to build OpenJDK using only free software build tools and to provide
383 replacements for the not-yet free parts of OpenJDK. One of the extensions that
384 IcedTea provides is a new JIT compiler named <a
385 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
386 to provide native code generation without introducing processor-dependent
393 <!-- *********************************************************************** -->
394 <div class="doc_section">
395 <a name="whatsnew">What's New in LLVM 2.7?</a>
397 <!-- *********************************************************************** -->
399 <div class="doc_text">
401 <p>This release includes a huge number of bug fixes, performance tweaks and
402 minor improvements. Some of the major improvements and new features are listed
408 <!--=========================================================================-->
409 <div class="doc_subsection">
410 <a name="majorfeatures">Major New Features</a>
413 <div class="doc_text">
415 <p>LLVM 2.7 includes several major new capabilities:</p>
423 <!--=========================================================================-->
424 <div class="doc_subsection">
425 <a name="coreimprovements">LLVM IR and Core Improvements</a>
428 <div class="doc_text">
429 <p>LLVM IR has several new features for better support of new targets and that
430 expose new optimization opportunities:</p>
438 <!--=========================================================================-->
439 <div class="doc_subsection">
440 <a name="optimizer">Optimizer Improvements</a>
443 <div class="doc_text">
445 <p>In addition to a large array of minor performance tweaks and bug fixes, this
446 release includes a few major enhancements and additions to the optimizers:</p>
457 <!--=========================================================================-->
458 <div class="doc_subsection">
459 <a name="executionengine">Interpreter and JIT Improvements</a>
462 <div class="doc_text">
466 href="http://llvm.org/viewvc/llvm-project?view=rev&revision=85295">defaults
467 to compiling eagerly</a> to avoid a race condition in the lazy JIT.
468 Clients that still want the lazy JIT can switch it on by calling
469 <tt>ExecutionEngine::DisableLazyCompilation(false)</tt>.</li>
470 <li>It is now possible to create more than one JIT instance in the same process.
471 These JITs can generate machine code in parallel,
472 although <a href="http://llvm.org/docs/ProgrammersManual.html#jitthreading">you
473 still have to obey the other threading restrictions</a>.</li>
478 <!--=========================================================================-->
479 <div class="doc_subsection">
480 <a name="codegen">Target Independent Code Generator Improvements</a>
483 <div class="doc_text">
485 <p>We have put a significant amount of work into the code generator
486 infrastructure, which allows us to implement more aggressive algorithms and make
495 <!--=========================================================================-->
496 <div class="doc_subsection">
497 <a name="x86">X86-32 and X86-64 Target Improvements</a>
500 <div class="doc_text">
501 <p>New features of the X86 target include:
512 <!--=========================================================================-->
513 <div class="doc_subsection">
514 <a name="pic16">PIC16 Target Improvements</a>
517 <div class="doc_text">
518 <p>New features of the PIC16 target include:
525 <p>Things not yet supported:</p>
528 <li>Variable arguments.</li>
529 <li>Interrupts/programs.</li>
534 <!--=========================================================================-->
535 <div class="doc_subsection">
536 <a name="ARM">ARM Target Improvements</a>
539 <div class="doc_text">
540 <p>New features of the ARM target include:
551 <!--=========================================================================-->
552 <div class="doc_subsection">
553 <a name="OtherTarget">Other Target Specific Improvements</a>
556 <div class="doc_text">
557 <p>New features of other targets include:
566 <!--=========================================================================-->
567 <div class="doc_subsection">
568 <a name="newapis">New Useful APIs</a>
571 <div class="doc_text">
573 <p>This release includes a number of new APIs that are used internally, which
574 may also be useful for external clients.
584 <!--=========================================================================-->
585 <div class="doc_subsection">
586 <a name="otherimprovements">Other Improvements and New Features</a>
589 <div class="doc_text">
590 <p>Other miscellaneous features include:</p>
599 <!--=========================================================================-->
600 <div class="doc_subsection">
601 <a name="changes">Major Changes and Removed Features</a>
604 <div class="doc_text">
606 <p>If you're already an LLVM user or developer with out-of-tree changes based
607 on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading
608 from the previous release.</p>
611 <li>The LLVM interpreter now defaults to <em>not</em> using <tt>libffi</tt> even
612 if you have it installed. This makes it more likely that an LLVM built on one
613 system will work when copied to a similar system. To use <tt>libffi</tt>,
614 configure with <tt>--enable-libffi</tt>.
619 <p>In addition, many APIs have changed in this release. Some of the major LLVM
623 <li><tt>ModuleProvider</tt> has been <a
624 href="http://llvm.org/viewvc/llvm-project?view=rev&revision=94686">removed</a>
625 and its methods moved to <tt>Module</tt> and <tt>GlobalValue</tt>.
626 Most clients can remove uses of <tt>ExistingModuleProvider</tt>,
627 replace <tt>getBitcodeModuleProvider</tt> with
628 <tt>getLazyBitcodeModule</tt>, and pass their <tt>Module</tt> to
629 functions that used to accept <tt>ModuleProvider</tt>. Clients who
630 wrote their own <tt>ModuleProvider</tt>s will need to derive from
631 <tt>GVMaterializer</tt> instead and use
632 <tt>Module::setMaterializer</tt> to attach it to a
633 <tt>Module</tt>.</li>
635 <li><tt>GhostLinkage</tt> has given up the ghost.
636 <tt>GlobalValue</tt>s that have not yet been read from their backing
637 storage have the same linkage they will have after being read in.
638 Clients must replace calls to
639 <tt>GlobalValue::hasNotBeenReadFromBitcode</tt> with
640 <tt>GlobalValue::isMaterializable</tt>.</li>
642 <li>FIXME: Debug info has been totally redone. Add pointers to new APIs. Substantial caveats about compatibility of .ll and .bc files.</li>
644 <li>The <tt>llvm/Support/DataTypes.h</tt> header has moved
645 to <tt>llvm/System/DataTypes.h</tt>.</li>
653 <!-- *********************************************************************** -->
654 <div class="doc_section">
655 <a name="portability">Portability and Supported Platforms</a>
657 <!-- *********************************************************************** -->
659 <div class="doc_text">
661 <p>LLVM is known to work on the following platforms:</p>
664 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
665 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
667 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
668 and 64-bit modes.</li>
669 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
670 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
671 support is available for native builds with Visual C++).</li>
672 <li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</li>
673 <li>Alpha-based machines running Debian GNU/Linux.</li>
676 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
677 to the machine and operating system on which it is built. However, minor
678 porting may be required to get LLVM to work on new platforms. We welcome your
679 portability patches and reports of successful builds or error messages.</p>
683 <!-- *********************************************************************** -->
684 <div class="doc_section">
685 <a name="knownproblems">Known Problems</a>
687 <!-- *********************************************************************** -->
689 <div class="doc_text">
691 <p>This section contains significant known problems with the LLVM system,
692 listed by component. If you run into a problem, please check the <a
693 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
694 there isn't already one.</p>
697 <li>The llvm-gcc bootstrap will fail with some versions of binutils (e.g. 2.15)
698 with a message of "<tt><a href="http://llvm.org/PR5004">Error: can not do 8
699 byte pc-relative relocation</a></tt>" when building C++ code. We intend to
700 fix this on mainline, but a workaround is to upgrade to binutils 2.17 or
703 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
704 using the stock GCC 3.x.x series 'out the box',
705 See: <a href="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
706 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
707 for x86/x86-64 has been made available from the third party AuroraUX Project
708 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
713 <!-- ======================================================================= -->
714 <div class="doc_subsection">
715 <a name="experimental">Experimental features included with this release</a>
718 <div class="doc_text">
720 <p>The following components of this LLVM release are either untested, known to
721 be broken or unreliable, or are in early development. These components should
722 not be relied on, and bugs should not be filed against them, but they may be
723 useful to some people. In particular, if you would like to work on one of these
724 components, please contact us on the <a
725 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
728 <li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430 and SystemZ backends are
730 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
731 supported value for this option. The ELF writer is experimental.</li>
732 <li>The implementation of Andersen's Alias Analysis has many known bugs.</li>
737 <!-- ======================================================================= -->
738 <div class="doc_subsection">
739 <a name="x86-be">Known problems with the X86 back-end</a>
742 <div class="doc_text">
745 <li>The X86 backend does not yet support
746 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
747 floating point stack</a>. It supports the 'f' and 't' constraints, but not
749 <li>The X86 backend generates inefficient floating point code when configured
750 to generate code for systems that don't have SSE2.</li>
751 <li>Win64 code generation wasn't widely tested. Everything should work, but we
752 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
753 runtime currently due
754 to <a href="http://llvm.org/PR2255">several</a>
755 <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
757 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
758 <li>The X86-64 backend does not yet support the LLVM IR instruction
759 <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
760 argument constructs on X86-64 by lowering them manually.</li>
765 <!-- ======================================================================= -->
766 <div class="doc_subsection">
767 <a name="ppc-be">Known problems with the PowerPC back-end</a>
770 <div class="doc_text">
773 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
774 compilation, and lacks support for debug information.</li>
779 <!-- ======================================================================= -->
780 <div class="doc_subsection">
781 <a name="arm-be">Known problems with the ARM back-end</a>
784 <div class="doc_text">
787 <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
788 and not well tested. Some features may not work at all, and the code quality
789 may be poor in some cases.</li>
790 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
791 processors, thumb programs can crash or produce wrong
792 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
793 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
799 <!-- ======================================================================= -->
800 <div class="doc_subsection">
801 <a name="sparc-be">Known problems with the SPARC back-end</a>
804 <div class="doc_text">
807 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
808 support the 64-bit SPARC ABI (-m64).</li>
813 <!-- ======================================================================= -->
814 <div class="doc_subsection">
815 <a name="mips-be">Known problems with the MIPS back-end</a>
818 <div class="doc_text">
821 <li>64-bit MIPS targets are not supported yet.</li>
826 <!-- ======================================================================= -->
827 <div class="doc_subsection">
828 <a name="alpha-be">Known problems with the Alpha back-end</a>
831 <div class="doc_text">
835 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
836 appropriate nops inserted to ensure restartability.</li>
841 <!-- ======================================================================= -->
842 <div class="doc_subsection">
843 <a name="c-be">Known problems with the C back-end</a>
846 <div class="doc_text">
849 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
850 inline assembly code</a>.</li>
851 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
852 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
853 C++ code compiled with <tt>llc</tt> or native compilers.</li>
854 <li>The C backend does not support all exception handling constructs.</li>
855 <li>The C backend does not support arbitrary precision integers.</li>
861 <!-- ======================================================================= -->
862 <div class="doc_subsection">
863 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
866 <div class="doc_text">
868 <p>The only major language feature of GCC not supported by llvm-gcc is
869 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
870 are only supported on some targets. For example, trampolines are only
871 supported on some targets (these are used when you take the address of a
872 nested function).</p>
874 <p>If you run into GCC extensions which are not supported, please let us know.
879 <!-- ======================================================================= -->
880 <div class="doc_subsection">
881 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
884 <div class="doc_text">
886 <p>The C++ front-end is considered to be fully
887 tested and works for a number of non-trivial programs, including LLVM
888 itself, Qt, Mozilla, etc.</p>
891 <li>Exception handling works well on the X86 and PowerPC targets. Currently
892 only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
897 <!-- ======================================================================= -->
898 <div class="doc_subsection">
899 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
902 <div class="doc_text">
904 <li>Fortran support generally works, but there are still several unresolved bugs
905 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
906 tools/gfortran component for details.</li>
910 <!-- ======================================================================= -->
911 <div class="doc_subsection">
912 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
915 <div class="doc_text">
916 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
917 technology, and problems should be expected.
919 <li>The Ada front-end currently only builds on X86-32. This is mainly due
920 to lack of trampoline support (pointers to nested functions) on other platforms.
921 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
922 which does support trampolines.</li>
923 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
924 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
925 exception handling, which is used internally by the compiler.
926 Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
927 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
928 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
929 (c380004 also fails with gcc-4.2 mainline).
930 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
931 causes the compiler to go into an infinite loop, using up all system memory.</li>
932 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
933 <li>The <tt>-E</tt> binder option (exception backtraces)
934 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
935 crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
936 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
937 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
938 or use representation clauses that result in a field of a non-discrete type
939 starting or finishing in the middle of a byte.</li>
940 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
941 'main' as generated by the Ada binder to be invalid</a>.
942 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
943 <tt>envp</tt> rather than integers.</li>
944 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
949 <!-- ======================================================================= -->
950 <div class="doc_subsection">
951 <a name="ocaml-bindings">Known problems with the O'Caml bindings</a>
954 <div class="doc_text">
956 <p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
957 <tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
958 <tt>Llvm.Linkage.Link_once</tt> will be correct. If you need any of the other linkage
959 modes, you'll have to write an external C library in order to expose the
960 functionality. This has been fixed in the trunk.</p>
963 <!-- *********************************************************************** -->
964 <div class="doc_section">
965 <a name="additionalinfo">Additional Information</a>
967 <!-- *********************************************************************** -->
969 <div class="doc_text">
971 <p>A wide variety of additional information is available on the <a
972 href="http://llvm.org">LLVM web page</a>, in particular in the <a
973 href="http://llvm.org/docs/">documentation</a> section. The web page also
974 contains versions of the API documentation which is up-to-date with the
975 Subversion version of the source code.
976 You can access versions of these documents specific to this release by going
977 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
979 <p>If you have any questions or comments about LLVM, please feel free to contact
980 us via the <a href="http://llvm.org/docs/#maillist"> mailing
985 <!-- *********************************************************************** -->
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