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11 <div class="doc_title">LLVM 2.5 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 2.5</a></li>
17 <li><a href="#whatsnew">What's New in LLVM?</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 <!-- *********************************************************************** -->
29 <div class="doc_section">
30 <a name="intro">Introduction</a>
32 <!-- *********************************************************************** -->
34 <div class="doc_text">
36 <p>This document contains the release notes for the LLVM Compiler
37 Infrastructure, release 2.5. Here we describe the status of LLVM, including
38 major improvements from the previous release and significant known problems.
39 All LLVM releases may be downloaded from the <a
40 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
42 <p>For more information about LLVM, including information about the latest
43 release, please check out the <a href="http://llvm.org/">main LLVM
44 web site</a>. If you have questions or comments, the <a
45 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
46 List</a> is a good place to send them.</p>
48 <p>Note that if you are reading this file from a Subversion checkout or the
49 main LLVM web page, this document applies to the <i>next</i> release, not the
50 current one. To see the release notes for a specific release, please see the
51 <a href="http://llvm.org/releases/">releases page</a>.</p>
55 <!-- Unfinished features in 2.5:
58 target-specific intrinsics
60 pre-alloc splitter, strong phi elim
61 llc -enable-value-prop, propagation of value info (sign/zero ext info) from
63 debug info for optimized code
65 postalloc scheduler: anti dependence breaking, hazard recognizer?
69 <!-- for announcement email:
72 <!-- *********************************************************************** -->
73 <div class="doc_section">
74 <a name="subproj">Sub-project Status Update</a>
76 <!-- *********************************************************************** -->
78 <div class="doc_text">
80 The LLVM 2.5 distribution currently consists of code from the core LLVM
81 repository (which roughly includes the LLVM optimizers, code generators and
82 supporting tools) and the llvm-gcc repository. In addition to this code, the
83 LLVM Project includes other sub-projects that are in development. The two which
84 are the most actively developed are the <a href="#clang">Clang Project</a> and
85 the <a href="#vmkit">VMKit Project</a>.
91 <!--=========================================================================-->
92 <div class="doc_subsection">
93 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
96 <div class="doc_text">
98 <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
99 a set of new 'LLVM native' front-end technologies for the LLVM optimizer
100 and code generator. While Clang is not included in the LLVM 2.5 release, it
101 is continuing to make major strides forward in all areas. Its C and Objective-C
102 parsing and code generation support is now very solid. For example, it is
103 capable of successfully building many real applications for X86-32 and X86-64,
104 including <a href="http://wiki.freebsd.org/BuildingFreeBSDWithClang">the FreeBSD
105 kernel</a>. C++ is also making <a
106 href="http://clang.llvm.org/cxx_status.html">incredible progress</a>, and work
107 on templates has recently started.</p>
109 <p>While Clang is not yet production quality, it is progressing very nicely and
110 is quite usable for building many C and Objective-C applications. If you are
111 interested in fast compiles and good diagnostics, we encourage you to try it out
112 by <a href="http://clang.llvm.org/get_started.html">building from mainline</a>
113 and reporting any issues you hit to the <a
114 href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
117 <p>In the LLVM 2.5 time-frame, the Clang team has made many improvements:</p>
120 <li>Clang now has a new driver, which is focused on providing a GCC-compatible
122 <li>The X86-64 ABI is now supported.</li>
123 <li>Precompiled header support is now implemented.</li>
124 <li>Objective-C support is significantly improved beyond LLVM 2.4, supporting
125 many features, such as Objective-C Garbage Collection.</li>
126 <li>Many many bugs are fixed.</li>
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 last LLVM release, 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 a growing set of checks to find
140 bugs that occur on a specific path within a program.</p>
142 <p>In the LLVM 2.5 time-frame there have been many significant improvements to
143 the analyzer's core path simulation engine and machinery for generating
144 path-based bug reports to end-users. Particularly noteworthy improvements
145 include experimental support for full field-sensitivity and reasoning about heap
146 objects as well as an improved value-constraints subengine that does a much
147 better job of reasoning about inequality relationships (e.g., <tt>x > 2</tt>)
148 between variables and constants.
150 <p>The set of checks performed by the static analyzer continue to expand, and
151 future plans for the tool include full source-level inter-procedural analysis
152 and deeper checks such as buffer overrun detection. There are many opportunities
153 to extend and enhance the static analyzer, and anyone interested in working on
154 this project is encouraged to get involved!</p>
158 <!--=========================================================================-->
159 <div class="doc_subsection">
160 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
163 <div class="doc_text">
165 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
166 a JVM and a CLI Virtual Machines (Microsoft .NET is an
167 implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
169 <p>Following LLVM 2.5, VMKit has its first release ? that you can find on its
170 <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
171 bug fixes, cleanup and new features. The major changes are:</p>
175 <li>Ahead of Time compiler: compiles .class files to llvm .bc. VMKit uses this
176 functionality to native compile the standard classes (eg java.lang.String).
177 Users can compile AOT .class files into dynamic libraries and run them with the
180 <li>New exception model: the dwarf exception model is very slow for
181 exception-intensive applications, so the JVM has had a new implementation of
182 exceptions which check at each function call if an exception happened. There is
183 a low performance penalty on applications without exceptions, but it is a big
184 gain for exception-intensive applications. For example the jack benchmark in
185 Spec JVM98 is 6x faster (performance gain of 83%).</li>
187 <li>New support for OSX/X64, Linux/X64 (with the Boehm GC), Linux/ppc32.</li>
192 <!-- *********************************************************************** -->
193 <div class="doc_section">
194 <a name="externalproj">External Projects Using LLVM 2.5</a>
196 <!-- *********************************************************************** -->
198 <!--=========================================================================-->
199 <div class="doc_subsection">
200 <a name="pure">Pure</a>
203 <div class="doc_text">
205 http://pure-lang.googlecode.com/
209 Pure is an algebraic/functional programming language based on term rewriting.
210 Programs are collections of equations which are used to evaluate expressions in
211 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
212 lexical closures, a hygienic macro system (also based on term rewriting),
213 built-in list and matrix support (including list and matrix comprehensions) and
214 an easy-to-use C interface. The interpreter uses LLVM as a backend to
215 JIT-compile Pure programs to fast native code.</p>
217 <p>In addition to the usual algebraic data structures, Pure also has
218 MATLAB-style matrices in order to support numeric computations and signal
219 processing in an efficient way. Pure is mainly aimed at mathematical
220 applications right now, but it has been designed as a general purpose language.
221 The dynamic interpreter environment and the C interface make it possible to use
222 it as a kind of functional scripting language for many application areas.
227 <!--=========================================================================-->
228 <div class="doc_subsection">
229 <a name="ldc">LLVM D Compiler</a>
232 <div class="doc_text">
234 http://www.dsource.org/projects/ldc
238 I'd like to inform that the LDC project (LLVM D
239 Compiler) is working with release 2.5 of LLVM. In fact we've required
240 2.5 in our trunk since the release was branched.
241 The improvements in 2.5 have fixed a lot of problems with LDC, more
242 specifically the new inline asm constraints, better debug info
243 support, general bugfixes :) and better x86-64 support have allowed
244 some major improvements in LDC, getting us much closer to being as
245 fully featured as the original DMD compiler from DigitalMars.
249 <!--=========================================================================-->
250 <div class="doc_subsection">
251 <a name="RoadsendPHP">Roadsend PHP</a>
254 <div class="doc_text">
255 <p>http://code.roadsend.com/rphp</p>
257 <p>Roadsend PHP is using LLVM for code generation. This is an open source
263 <!-- *********************************************************************** -->
264 <div class="doc_section">
265 <a name="whatsnew">What's New in LLVM?</a>
267 <!-- *********************************************************************** -->
269 <div class="doc_text">
271 <p>This release includes a huge number of bug fixes, performance tweaks, and
272 minor improvements. Some of the major improvements and new features are listed
277 <!--=========================================================================-->
278 <div class="doc_subsection">
279 <a name="majorfeatures">Major New Features</a>
282 <div class="doc_text">
284 <p>LLVM 2.5 includes several major new capabilities:</p>
287 <li><p>The code generator now supports arbitrary precision integers.
288 Types like <tt>i33</tt> have long been valid in the LLVM IR, but previously
289 could only be used with the interpreter.
290 Now IR using such types can be compiled to native code on all targets.
291 All operations are supported if the integer is not bigger than twice the
292 target machine word size.
293 Simple operations like loads, stores and shifts by a constant amount are
294 supported for integers of any size.
300 Pure project: http://code.google.com/p/pure-lang/
306 .ll parser rewrite, caret diags, better errors, less fragile (less likely to
307 crash on strange things). No longer depends on flex/bison.
308 GCC inliner off, llvm handles always-inline.
310 x86 backend GS segment -> addr space 256 (r62980)
312 addreadattrs pass renamed to functionattrs; now calculates nocapture
313 memdep (used by GVN and memcpyopt) is faster / more aggressive.
314 how to write a backend doc docs/WritingAnLLVMBackend.html
315 fastisel + exception handling
316 vector widening <3 x float> -> <4 x float>
317 arm port improvements? arm jit encoding stuff, constant island support?
318 JIT TLS support on x86-32 but not x86-64.
319 mem2reg now faster on code with huge basic blocks
320 stack protectors/stack canaries, -fstack-protector, controllable on a
321 per-function basis with attributes.
322 shufflevector is generalized to allow different shuffle mask width than its
324 loop optimizer improves floating point induction variables
325 llvm/Analysis/DebugInfo.h classes, llvm-gcc and clang and codegen use them.
326 DebugInfoBuilder gone.
327 asmprinters seperate from targets for jits
328 PBQP register allocator now supports register coalescing.
329 JIT supports exceptions on linux/x86-64 and linux/x86-64.
330 integer overflow intrinsics for [us](add/sub/mul). Supported on all targets,
331 but only generates efficient code on x86.
332 X86 backend now supports -disable-mmx.
333 noalias attribute on return value indicates that function returns new memory
335 llvmc2 renamed to llvmc
336 Jump threading more powerful: it is iterative, handles threading based on values
337 with fully redundant and partially redundant loads.
339 ARM debug info support?
340 unit test framework based on Google Test.
342 vector shift support + X86 backend.
343 x86 JIT now detects core i7 and atom, autoconfiguring itself appropriately.
344 SROA is more aggressive about promoting unions.
345 non-zero __builtin_return_address values on X86.
346 x86-64 now uses red zone (unless -mno-red-zone option is specified).
349 llvm-gcc defaults to -fno-math-errno on all x86 targets.
351 initial support for debug line numbers when optimization enabled, not useful in
352 2.5 but will be for 2.6.
360 <!--=========================================================================-->
361 <div class="doc_subsection">
362 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
365 <div class="doc_text">
367 <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
368 front-ends and driver with the LLVM optimizer and code generator. It currently
369 includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
378 <!--=========================================================================-->
379 <div class="doc_subsection">
380 <a name="coreimprovements">LLVM Core Improvements</a>
383 <div class="doc_text">
384 <p>New features include:</p>
393 <!--=========================================================================-->
394 <div class="doc_subsection">
395 <a name="optimizer">Optimizer Improvements</a>
398 <div class="doc_text">
400 <p>In addition to a huge array of bug fixes and minor performance tweaks, this
401 release includes a few major enhancements and additions to the optimizers:</p>
411 <!--=========================================================================-->
412 <div class="doc_subsection">
413 <a name="codegen">Code Generator Improvements</a>
416 <div class="doc_text">
418 <p>We have put a significant amount of work into the code generator infrastructure,
419 which allows us to implement more aggressive algorithms and make it run
423 <li>The type legalization logic has been completely rewritten, and is now
424 more powerful (it supports arbitrary precision integer types for example)
425 and hopefully more correct.
426 The type legalizer converts operations on types that are not natively
427 supported by the target machine into equivalent code sequences that only use
428 natively supported types.
429 The old type legalizer is still available and will be used if
430 <tt>-disable-legalize-types</tt> is passed to <tt>llc</tt>.
439 <!--=========================================================================-->
440 <div class="doc_subsection">
441 <a name="pic16">PIC16 Target Improvements</a>
444 <div class="doc_text">
445 <p>New features of the PIC16 target include:
449 <li>Both direct and indirect load/stores work now.</li>
450 <li>Logical, bitwise and conditional operations now work for integer data
452 <li>Function calls involving basic types work now.</li>
453 <li>Support for integer arrays.</li>
454 <li>Compiler can now emit libcalls for operations not support by m/c insns.</li>
455 <li>Support for both data and rom address spaces.</li>
459 <p>Things not yet supported:</p>
462 <li>Floating point.</li>
463 <li>Passing/returning aggregate types to/from functions.</li>
464 <li>Variable arguments.</li>
465 <li>Indirect function calls.</li>
466 <li>Interrupts/prgrams.</li>
474 <!--=========================================================================-->
475 <div class="doc_subsection">
476 <a name="othertargetspecific">Other Target Specific Improvements</a>
479 <div class="doc_text">
480 <p>New target-specific features include:
489 <!--=========================================================================-->
490 <div class="doc_subsection">
491 <a name="llvmc">Improvements in LLVMC</a>
494 <div class="doc_text">
495 <p>New features include:</p>
498 <li>Beginning with LLVM 2.5, llvmc2 is known as just 'llvmc'. The
499 old llvmc driver was removed.</li>
501 <li>The Clang plugin was substantially improved and is now enabled
502 by default. The command 'llvmc --clang' can be now used as a
503 synonym to 'ccc'.</li>
505 <li>There is now a '--check-graph' option which is supposed to
506 catch common errors like multiple default edges, mismatched
507 output/input language names and cycles. In general, these
508 checks can't be done at compile-time because of the need to
509 support plugins.</li>
511 <li>Plugins are now more flexible and can refer to compilation
512 graph nodes and options defined in other plugins. To manage
513 dependencies, a priority-sorting mechanism was introduced. This
514 change affects the '.td' file syntax; see the documentation for
517 <li>Hooks can now be provided with arguments. The syntax
518 is "$CALL(MyHook, 'Arg1', 'Arg2', 'Arg #3')".</li>
520 <li>A new option type: multi-valued option, for options that take
521 more than one argument (for example, "-foo a b c").</li>
523 <li>New option properties: 'one_or_more', 'zero_or_more', 'hidden'
524 and 'really_hidden'.</li>
526 <li>The 'case' expression gained an 'error' action and an 'empty'
527 test (equivalent to '(not (not_empty ...))').</li>
529 <li>Documentation now looks more consistent to the rest of the LLVM
530 docs. There is also a man page now.</li>
537 <!--=========================================================================-->
538 <div class="doc_subsection">
539 <a name="otherimprovements">Other Improvements</a>
542 <div class="doc_text">
543 <p>New features include:
553 <!--=========================================================================-->
554 <div class="doc_subsection">
555 <a name="changes">Major Changes and Removed Features</a>
558 <div class="doc_text">
560 <p>If you're already an LLVM user or developer with out-of-tree changes based
561 on LLVM 2.4, this section lists some "gotchas" that you may run into upgrading
562 from the previous release.</p>
570 <p>In addition, many APIs have changed in this release. Some of the major LLVM
584 <!-- *********************************************************************** -->
585 <div class="doc_section">
586 <a name="portability">Portability and Supported Platforms</a>
588 <!-- *********************************************************************** -->
590 <div class="doc_text">
592 <p>LLVM is known to work on the following platforms:</p>
595 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
596 Linux, Fedora Core and FreeBSD (and probably other unix-like systems).</li>
597 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
598 and 64-bit modes.</li>
599 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
600 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
601 support is available for native builds with Visual C++).</li>
602 <li>Sun UltraSPARC workstations running Solaris 10.</li>
603 <li>Alpha-based machines running Debian GNU/Linux.</li>
604 <li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
607 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
608 to the machine and operating system on which it is built. However, minor
609 porting may be required to get LLVM to work on new platforms. We welcome your
610 portability patches and reports of successful builds or error messages.</p>
614 <!-- *********************************************************************** -->
615 <div class="doc_section">
616 <a name="knownproblems">Known Problems</a>
618 <!-- *********************************************************************** -->
620 <div class="doc_text">
622 <p>This section contains significant known problems with the LLVM system,
623 listed by component. If you run into a problem, please check the <a
624 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
625 there isn't already one.</p>
629 <!-- ======================================================================= -->
630 <div class="doc_subsection">
631 <a name="experimental">Experimental features included with this release</a>
634 <div class="doc_text">
636 <p>The following components of this LLVM release are either untested, known to
637 be broken or unreliable, or are in early development. These components should
638 not be relied on, and bugs should not be filed against them, but they may be
639 useful to some people. In particular, if you would like to work on one of these
640 components, please contact us on the <a
641 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
644 <li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
645 <li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
646 value for this option.</li>
651 <!-- ======================================================================= -->
652 <div class="doc_subsection">
653 <a name="x86-be">Known problems with the X86 back-end</a>
656 <div class="doc_text">
659 <li>The X86 backend does not yet support
660 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
661 floating point stack</a>. It supports the 'f' and 't' constraints, but not
663 <li>The X86 backend generates inefficient floating point code when configured
664 to generate code for systems that don't have SSE2.</li>
665 <li>Win64 code generation wasn't widely tested. Everything should work, but we
666 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
668 to <a href="http://llvm.org/PR2255">several</a>
669 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
670 'u' inline assembly constraint and X87 floating point inline assembly.</li>
671 <li>The X86-64 backend does not yet support the LLVM IR instruction
672 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
673 argument constructs on X86-64 by lowering them manually.</li>
678 <!-- ======================================================================= -->
679 <div class="doc_subsection">
680 <a name="ppc-be">Known problems with the PowerPC back-end</a>
683 <div class="doc_text">
686 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
687 compilation, and lacks support for debug information.</li>
692 <!-- ======================================================================= -->
693 <div class="doc_subsection">
694 <a name="arm-be">Known problems with the ARM back-end</a>
697 <div class="doc_text">
700 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
701 processors, thumb programs can crash or produce wrong
702 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
703 <li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
705 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
707 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
712 <!-- ======================================================================= -->
713 <div class="doc_subsection">
714 <a name="sparc-be">Known problems with the SPARC back-end</a>
717 <div class="doc_text">
720 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
721 support the 64-bit SPARC ABI (-m64).</li>
726 <!-- ======================================================================= -->
727 <div class="doc_subsection">
728 <a name="mips-be">Known problems with the MIPS back-end</a>
731 <div class="doc_text">
734 <li>The O32 ABI is not fully supported.</li>
735 <li>64-bit MIPS targets are not supported yet.</li>
740 <!-- ======================================================================= -->
741 <div class="doc_subsection">
742 <a name="alpha-be">Known problems with the Alpha back-end</a>
745 <div class="doc_text">
749 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
750 appropriate nops inserted to ensure restartability.</li>
755 <!-- ======================================================================= -->
756 <div class="doc_subsection">
757 <a name="ia64-be">Known problems with the IA64 back-end</a>
760 <div class="doc_text">
763 <li>The Itanium backend is highly experimental, and has a number of known
764 issues. We are looking for a maintainer for the Itanium backend. If you
765 are interested, please contact the LLVMdev mailing list.</li>
770 <!-- ======================================================================= -->
771 <div class="doc_subsection">
772 <a name="c-be">Known problems with the C back-end</a>
775 <div class="doc_text">
778 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
779 inline assembly code</a>.</li>
780 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
781 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
782 C++ code compiled with llc or native compilers.</li>
783 <li>The C backend does not support all exception handling constructs.</li>
784 <li>The C backend does not support arbitrary precision integers.</li>
790 <!-- ======================================================================= -->
791 <div class="doc_subsection">
792 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
795 <div class="doc_text">
797 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
798 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
799 LLVMdev mailing list if you are interested.</p>
801 <p>The only major language feature of GCC not supported by llvm-gcc is
802 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
803 are only supported on some targets. For example, trampolines are only
804 supported on some targets (these are used when you take the address of a
805 nested function).</p>
807 <p>If you run into GCC extensions which are not supported, please let us know.
812 <!-- ======================================================================= -->
813 <div class="doc_subsection">
814 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
817 <div class="doc_text">
819 <p>The C++ front-end is considered to be fully
820 tested and works for a number of non-trivial programs, including LLVM
821 itself, Qt, Mozilla, etc.</p>
824 <li>Exception handling works well on the X86 and PowerPC targets. Currently
825 only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
830 <!-- ======================================================================= -->
831 <div class="doc_subsection">
832 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
835 <div class="doc_text">
837 <li>Fortran support generally works, but there are still several unresolved bugs
838 in Bugzilla. Please see the tools/gfortran component for details.</li>
840 <li>The Fortran front-end currently does not build on Darwin (without tweaks)
841 due to unresolved dependencies on the C front-end.</li>
845 <!-- ======================================================================= -->
846 <div class="doc_subsection">
847 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
850 <div class="doc_text">
851 The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
852 technology and problems should be expected.
854 <li>The Ada front-end currently only builds on X86-32. This is mainly due
855 to lack of trampoline support (pointers to nested functions) on other platforms,
856 however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
857 which does support trampolines.</li>
858 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
859 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
860 exception handling, which is used internally by the compiler.
861 Workaround: configure with --disable-bootstrap.</li>
862 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
863 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
864 (c380004 also fails with gcc-4.2 mainline).
865 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
866 causes the compiler to go into an infinite loop, using up all system memory.</li>
867 <li>Some gcc specific Ada tests continue to crash the compiler.</li>
868 <li>The -E binder option (exception backtraces)
869 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
870 crashing if an exception is raised. Workaround: do not use -E.</li>
871 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
872 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
873 or use representation clauses that result in a field of a non-discrete type
874 starting or finishing in the middle of a byte.</li>
875 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
876 'main' as generated by the Ada binder to be invalid</a>.
877 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
878 <tt>envp</tt> rather than integers.</li>
879 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
884 <!-- *********************************************************************** -->
885 <div class="doc_section">
886 <a name="additionalinfo">Additional Information</a>
888 <!-- *********************************************************************** -->
890 <div class="doc_text">
892 <p>A wide variety of additional information is available on the <a
893 href="http://llvm.org">LLVM web page</a>, in particular in the <a
894 href="http://llvm.org/docs/">documentation</a> section. The web page also
895 contains versions of the API documentation which is up-to-date with the
896 Subversion version of the source code.
897 You can access versions of these documents specific to this release by going
898 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
900 <p>If you have any questions or comments about LLVM, please feel free to contact
901 us via the <a href="http://llvm.org/docs/#maillist"> mailing
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