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11 <div class="doc_title">LLVM 2.6 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 2.6</a></li>
17 <li><a href="#whatsnew">What's New in LLVM 2.6?</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 2.6. 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>
58 include/llvm/Analysis/LiveValues.h => Dan
59 lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
60 llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
64 <!-- Unfinished features in 2.6:
67 variable debug info for optimized code
68 postalloc scheduler: anti dependence breaking, hazard recognizer?
70 loop dependence analysis
71 ELF Writer? How stable?
72 <li>PostRA scheduler improvements, ARM adoption (David Goodwin).</li>
73 2.7 supports the GDB 7.0 jit interfaces for debug info.
74 2.7 eliminates ADT/iterator.h
77 <!-- for announcement email:
81 KLEE web page at klee.llvm.org
82 Many new papers added to /pubs/
87 <!-- *********************************************************************** -->
88 <div class="doc_section">
89 <a name="subproj">Sub-project Status Update</a>
91 <!-- *********************************************************************** -->
93 <div class="doc_text">
95 The LLVM 2.6 distribution currently consists of code from the core LLVM
96 repository (which roughly includes the LLVM optimizers, code generators
97 and supporting tools), the Clang repository and the llvm-gcc repository. In
98 addition to this code, the LLVM Project includes other sub-projects that are in
99 development. Here we include updates on these subprojects.
105 <!--=========================================================================-->
106 <div class="doc_subsection">
107 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
110 <div class="doc_text">
112 <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
113 a set of new 'LLVM native' front-end technologies for the C family of languages.
114 LLVM 2.6 is the first release to officially include Clang, and it provides a
115 production quality C and Objective-C compiler. If you are interested in <a
116 href="http://clang.llvm.org/performance.html">fast compiles</a> and
117 <a href="http://clang.llvm.org/diagnostics.html">good diagnostics</a>, we
118 encourage you to try it out. Clang currently compiles typical Objective-C code
119 3x faster than GCC and compiles C code about 30% faster than GCC at -O0 -g
120 (which is when the most pressure is on the frontend).</p>
122 <p>In addition to supporting these languages, C++ support is also <a
123 href="http://clang.llvm.org/cxx_status.html">well under way</a>, and mainline
124 Clang is able to parse the libstdc++ 4.2 headers and even codegen simple apps.
125 If you are interested in Clang C++ support or any other Clang feature, we
126 strongly encourage you to get involved on the <a
127 href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
130 <p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
133 <li>C and Objective-C support are now considered production quality.</li>
134 <li>AuroraUX, FreeBSD and OpenBSD are now supported.</li>
135 <li>Most of Objective-C 2.0 is now supported with the GNU runtime.</li>
136 <li>Many many bugs are fixed and lots of features have been added.</li>
140 <!--=========================================================================-->
141 <div class="doc_subsection">
142 <a name="clangsa">Clang Static Analyzer</a>
145 <div class="doc_text">
147 <p>Previously announced in the 2.4 and 2.5 LLVM releases, the Clang project also
148 includes an early stage static source code analysis tool for <a
149 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
150 in C and Objective-C programs. The tool performs checks to find
151 bugs that occur on a specific path within a program.</p>
153 <p>In the LLVM 2.6 time-frame, the analyzer core has undergone several important
154 improvements and cleanups and now includes a new <em>Checker</em> interface that
155 is intended to eventually serve as a basis for domain-specific checks. Further,
156 in addition to generating HTML files for reporting analysis results, the
157 analyzer can now also emit bug reports in a structured XML format that is
158 intended to be easily readable by other programs.</p>
160 <p>The set of checks performed by the static analyzer continues to expand, and
161 future plans for the tool include full source-level inter-procedural analysis
162 and deeper checks such as buffer overrun detection. There are many opportunities
163 to extend and enhance the static analyzer, and anyone interested in working on
164 this project is encouraged to get involved!</p>
168 <!--=========================================================================-->
169 <div class="doc_subsection">
170 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
173 <div class="doc_text">
175 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
176 a JVM and a CLI Virtual Machine (Microsoft .NET is an
177 implementation of the CLI) using LLVM for static and just-in-time
181 VMKit version 0.26 builds with LLVM 2.6 and you can find it on its
182 <a href="http://vmkit.llvm.org/releases/">web page</a>. The release includes
183 bug fixes, cleanup and new features. The major changes are:</p>
187 <li>A new llcj tool to generate shared libraries or executables of Java
189 <li>Cooperative garbage collection. </li>
190 <li>Fast subtype checking (paper from Click et al [JGI'02]). </li>
191 <li>Implementation of a two-word header for Java objects instead of the original
192 three-word header. </li>
193 <li>Better Java specification-compliance: division by zero checks, stack
194 overflow checks, finalization and references support. </li>
200 <!--=========================================================================-->
201 <div class="doc_subsection">
202 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
205 <div class="doc_text">
207 The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
208 is a simple library that provides an implementation of the low-level
209 target-specific hooks required by code generation and other runtime components.
210 For example, when compiling for a 32-bit target, converting a double to a 64-bit
211 unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
212 function. The compiler-rt library provides highly optimized implementations of
213 this and other low-level routines (some are 3x faster than the equivalent
214 libgcc routines).</p>
217 All of the code in the compiler-rt project is available under the standard LLVM
218 License, a "BSD-style" license.</p>
222 <!--=========================================================================-->
223 <div class="doc_subsection">
224 <a name="klee">KLEE: Symbolic Execution and Automatic Test Case Generator</a>
227 <div class="doc_text">
229 The new LLVM <a href="http://klee.llvm.org/">KLEE project</a> is a symbolic
230 execution framework for programs in LLVM bitcode form. KLEE tries to
231 symbolically evaluate "all" paths through the application and records state
232 transitions that lead to fault states. This allows it to construct testcases
233 that lead to faults and can even be used to verify algorithms. For more
234 details, please see the <a
235 href="http://llvm.org/pubs/2008-12-OSDI-KLEE.html">OSDI 2008 paper</a> about
240 <!--=========================================================================-->
241 <div class="doc_subsection">
242 <a name="dragonegg">DragonEgg: GCC-4.5 as an LLVM frontend</a>
245 <div class="doc_text">
247 The goal of <a href="http://dragonegg.llvm.org/">DragonEgg</a> is to make
248 gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever.
249 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a shared library (llvm.so)
250 that is loaded by gcc at runtime. It uses the new gcc plugin architecture to
251 disable the GCC optimizers and code generators, and schedule the LLVM optimizers
252 and code generators (or direct output of LLVM IR) instead. Currently only Linux
253 and Darwin are supported, and only on x86-32 and x86-64. It should be easy to
254 add additional unix-like architectures and other processor families. In theory
255 it should be possible to use <a href="http://dragonegg.llvm.org/">DragonEgg</a>
256 with any language supported by gcc, however only C and Fortran work well for the
257 moment. Ada and C++ work to some extent, while Java, Obj-C and Obj-C++ are so
258 far entirely untested. Since gcc-4.5 has not yet been released, neither has
259 <a href="http://dragonegg.llvm.org/">DragonEgg</a>. To build
260 <a href="http://dragonegg.llvm.org/">DragonEgg</a> you will need to check out the
261 development versions of <a href="http://gcc.gnu.org/svn.html/"> gcc</a>,
262 <a href="http://llvm.org/docs/GettingStarted.html#checkout">llvm</a> and
263 <a href="http://dragonegg.llvm.org/">DragonEgg</a> from their respective
264 subversion repositories, and follow the instructions in the
265 <a href="http://dragonegg.llvm.org/">DragonEgg</a> README.
271 <!--=========================================================================-->
272 <div class="doc_subsection">
273 <a name="mc">llvm-mc: Machine Code Toolkit</a>
276 <div class="doc_text">
278 The LLVM Machine Code (MC) Toolkit project is a (very early) effort to build
279 better tools for dealing with machine code, object file formats, etc. The idea
280 is to be able to generate most of the target specific details of assemblers and
281 disassemblers from existing LLVM target .td files (with suitable enhancements),
282 and to build infrastructure for reading and writing common object file formats.
283 One of the first deliverables is to build a full assembler and integrate it into
284 the compiler, which is predicted to substantially reduce compile time in some
288 <p>In the LLVM 2.6 timeframe, the MC framework has grown to the point where it
289 can reliably parse and pretty print (with some encoding information) a
290 darwin/x86 .s file successfully, and has the very early phases of a Mach-O
291 assembler in progress. Beyond the MC framework itself, major refactoring of the
292 LLVM code generator has started. The idea is to make the code generator reason
293 about the code it is producing in a much more semantic way, rather than a
294 textual way. For example, the code generator now uses MCSection objects to
295 represent section assignments, instead of text strings that print to .section
298 <p>MC is an early and ongoing project that will hopefully continue to lead to
299 many improvements in the code generator and build infrastructure useful for many
306 <!-- *********************************************************************** -->
307 <div class="doc_section">
308 <a name="externalproj">External Projects Using LLVM 2.6</a>
310 <!-- *********************************************************************** -->
312 <div class="doc_text">
314 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
315 a lot of other language and tools projects. This section lists some of the
316 projects that have already been updated to work with LLVM 2.6.</p>
320 <!--=========================================================================-->
321 <div class="doc_subsection">
322 <a name="Rubinius">Rubinius</a>
325 <div class="doc_text">
326 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
327 for running Ruby code which strives to write as much of the core class
328 implementation in Ruby as possible. Combined with a bytecode interpreting VM, it
329 uses LLVM to optimize and compile ruby code down to machine code. Techniques
330 such as type feedback, method inlining, and uncommon traps are all used to
331 remove dynamism from ruby execution and increase performance.</p>
333 <p>Since LLVM 2.5, Rubinius has made several major leaps forward, implementing
334 a counter based JIT, type feedback and speculative method inlining.
339 <!--=========================================================================-->
340 <div class="doc_subsection">
341 <a name="macruby">MacRuby</a>
344 <div class="doc_text">
347 <a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
348 core Mac OS X technologies, such as the Objective-C common runtime and garbage
349 collector and the CoreFoundation framework. It is principally developed by
350 Apple and aims at enabling the creation of full-fledged Mac OS X applications.
354 MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
355 expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
361 <!--=========================================================================-->
362 <div class="doc_subsection">
363 <a name="pure">Pure</a>
366 <div class="doc_text">
368 <a href="http://pure-lang.googlecode.com/">Pure</a>
369 is an algebraic/functional programming language based on term rewriting.
370 Programs are collections of equations which are used to evaluate expressions in
371 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
372 lexical closures, a hygienic macro system (also based on term rewriting),
373 built-in list and matrix support (including list and matrix comprehensions) and
374 an easy-to-use C interface. The interpreter uses LLVM as a backend to
375 JIT-compile Pure programs to fast native code.</p>
377 <p>Pure versions 0.31 and later have been tested and are known to work with
378 LLVM 2.6 (and continue to work with older LLVM releases >= 2.3 as well).
383 <!--=========================================================================-->
384 <div class="doc_subsection">
385 <a name="ldc">LLVM D Compiler</a>
388 <div class="doc_text">
390 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
391 the D Programming Language using the LLVM optimizer and code generator.
392 The LDC project works great with the LLVM 2.6 release. General improvements in
394 cycle have included new inline asm constraint handling, better debug info
395 support, general bug fixes and better x86-64 support. This has allowed
396 some major improvements in LDC, getting it much closer to being as
397 fully featured as the original DMD compiler from DigitalMars.
401 <!--=========================================================================-->
402 <div class="doc_subsection">
403 <a name="RoadsendPHP">Roadsend PHP</a>
406 <div class="doc_text">
408 <a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
409 source implementation of the PHP programming
410 language that uses LLVM for its optimizer, JIT and static compiler. This is a
411 reimplementation of an earlier project that is now based on LLVM.</p>
414 <!--=========================================================================-->
415 <div class="doc_subsection">
416 <a name="UnladenSwallow">Unladen Swallow</a>
419 <div class="doc_text">
421 <a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
422 branch of <a href="http://python.org/">Python</a> intended to be fully
423 compatible and significantly faster. It uses LLVM's optimization passes and JIT
427 <!--=========================================================================-->
428 <div class="doc_subsection">
429 <a name="llvm-lua">llvm-lua</a>
432 <div class="doc_text">
434 <a href="http://code.google.com/p/llvm-lua/">LLVM-Lua</a> uses LLVM to add JIT
435 and static compiling support to the Lua VM. Lua bytecode is analyzed to
436 remove type checks, then LLVM is used to compile the bytecode down to machine
442 <!-- *********************************************************************** -->
443 <div class="doc_section">
444 <a name="whatsnew">What's New in LLVM 2.6?</a>
446 <!-- *********************************************************************** -->
448 <div class="doc_text">
450 <p>This release includes a huge number of bug fixes, performance tweaks and
451 minor improvements. Some of the major improvements and new features are listed
457 <!--=========================================================================-->
458 <div class="doc_subsection">
459 <a name="majorfeatures">Major New Features</a>
462 <div class="doc_text">
464 <p>LLVM 2.6 includes several major new capabilities:</p>
467 <li>New <a href="#compiler-rt">compiler-rt</a>, <A href="#klee">KLEE</a>
468 and <a href="#mc">machine code toolkit</a> sub-projects.</li>
469 <li>Debug information now includes line numbers when optimizations are enabled.
470 This allows statistical sampling tools like OProfile and Shark to map
471 samples back to source lines.</li>
472 <li>LLVM now includes new experimental backends to support the MSP430, SystemZ
473 and BlackFin architectures.</li>
474 <li>LLVM supports a new <a href="GoldPlugin.html">Gold Linker Plugin</a> which
475 enables support for <a href="LinkTimeOptimization.html">transparent
476 link-time optimization</a> on ELF targets when used with the Gold binutils
478 <li>LLVM now supports doing optimization and code generation on multiple
479 threads. Please see the <a href="ProgrammersManual.html#threading">LLVM
480 Programmer's Manual</a> for more information.</li>
481 <li>LLVM now has experimental support for <a
482 href="http://nondot.org/~sabre/LLVMNotes/EmbeddedMetadata.txt">embedded
483 metadata</a> in LLVM IR, though the implementation is not guaranteed to be
484 final and the .bc file format may change in future releases. Debug info
485 does not yet use this format in LLVM 2.6.</li>
490 <!--=========================================================================-->
491 <div class="doc_subsection">
492 <a name="coreimprovements">LLVM IR and Core Improvements</a>
495 <div class="doc_text">
496 <p>LLVM IR has several new features for better support of new targets and that
497 expose new optimization opportunities:</p>
500 <li>The <a href="LangRef.html#i_add">add</a>, <a
501 href="LangRef.html#i_sub">sub</a> and <a href="LangRef.html#i_mul">mul</a>
502 instructions have been split into integer and floating point versions (like
503 divide and remainder), introducing new <a
504 href="LangRef.html#i_fadd">fadd</a>, <a href="LangRef.html#i_fsub">fsub</a>,
505 and <a href="LangRef.html#i_fmul">fmul</a> instructions.</li>
506 <li>The <a href="LangRef.html#i_add">add</a>, <a
507 href="LangRef.html#i_sub">sub</a> and <a href="LangRef.html#i_mul">mul</a>
508 instructions now support optional "nsw" and "nuw" bits which indicate that
509 the operation is guaranteed to not overflow (in the signed or
510 unsigned case, respectively). This gives the optimizer more information and
511 can be used for things like C signed integer values, which are undefined on
513 <li>The <a href="LangRef.html#i_sdiv">sdiv</a> instruction now supports an
514 optional "exact" flag which indicates that the result of the division is
515 guaranteed to have a remainder of zero. This is useful for optimizing pointer
516 subtraction in C.</li>
517 <li>The <a href="LangRef.html#i_getelementptr">getelementptr</a> instruction now
518 supports arbitrary integer index values for array/pointer indices. This
519 allows for better code generation on 16-bit pointer targets like PIC16.</li>
520 <li>The <a href="LangRef.html#i_getelementptr">getelementptr</a> instruction now
521 supports an "inbounds" optimization hint that tells the optimizer that the
522 pointer is guaranteed to be within its allocated object.</li>
523 <li>LLVM now support a series of new linkage types for global values which allow
524 for better optimization and new capabilities:
526 <li><a href="LangRef.html#linkage_linkonce">linkonce_odr</a> and
527 <a href="LangRef.html#linkage_weak">weak_odr</a> have the same linkage
528 semantics as the non-"odr" linkage types. The difference is that these
529 linkage types indicate that all definitions of the specified function
530 are guaranteed to have the same semantics. This allows inlining
531 templates functions in C++ but not inlining weak functions in C,
532 which previously both got the same linkage type.</li>
533 <li><a href="LangRef.html#linkage_available_externally">available_externally
534 </a> is a new linkage type that gives the optimizer visibility into the
535 definition of a function (allowing inlining and side effect analysis)
536 but that does not cause code to be generated. This allows better
537 optimization of "GNU inline" functions, extern templates, etc.</li>
538 <li><a href="LangRef.html#linkage_linker_private">linker_private</a> is a
539 new linkage type (which is only useful on Mac OS X) that is used for
540 some metadata generation and other obscure things.</li>
542 <li>Finally, target-specific intrinsics can now return multiple values, which
543 is useful for modeling target operations with multiple results.</li>
548 <!--=========================================================================-->
549 <div class="doc_subsection">
550 <a name="optimizer">Optimizer Improvements</a>
553 <div class="doc_text">
555 <p>In addition to a large array of minor performance tweaks and bug fixes, this
556 release includes a few major enhancements and additions to the optimizers:</p>
560 <li>The <a href="Passes.html#scalarrepl">Scalar Replacement of Aggregates</a>
561 pass has many improvements that allow it to better promote vector unions,
562 variables which are memset, and much more strange code that can happen to
563 do bitfield accesses to register operations. An interesting change is that
564 it now produces "unusual" integer sizes (like i1704) in some cases and lets
565 other optimizers clean things up.</li>
566 <li>The <a href="Passes.html#loop-reduce">Loop Strength Reduction</a> pass now
567 promotes small integer induction variables to 64-bit on 64-bit targets,
568 which provides a major performance boost for much numerical code. It also
569 promotes shorts to int on 32-bit hosts, etc. LSR now also analyzes pointer
570 expressions (e.g. getelementptrs), as well as integers.</li>
571 <li>The <a href="Passes.html#gvn">GVN</a> pass now eliminates partial
572 redundancies of loads in simple cases.</li>
573 <li>The <a href="Passes.html#inline">Inliner</a> now reuses stack space when
574 inlining similar arrays from multiple callees into one caller.</li>
575 <li>LLVM includes a new experimental Static Single Information (SSI)
576 construction pass.</li>
583 <!--=========================================================================-->
584 <div class="doc_subsection">
585 <a name="executionengine">Interpreter and JIT Improvements</a>
588 <div class="doc_text">
591 <li>LLVM has a new "EngineBuilder" class which makes it more obvious how to
592 set up and configure an ExecutionEngine (a JIT or interpreter).</li>
593 <li>The JIT now supports generating more than 16M of code.</li>
594 <li>When configured with <tt>--with-oprofile</tt>, the JIT can now inform
595 OProfile about JIT'd code, allowing OProfile to get line number and function
596 name information for JIT'd functions.</li>
597 <li>When "libffi" is available, the LLVM interpreter now uses it, which supports
598 calling almost arbitrary external (natively compiled) functions.</li>
599 <li>Clients of the JIT can now register a 'JITEventListener' object to receive
600 callbacks when the JIT emits or frees machine code. The OProfile support
601 uses this mechanism.</li>
606 <!--=========================================================================-->
607 <div class="doc_subsection">
608 <a name="codegen">Target Independent Code Generator Improvements</a>
611 <div class="doc_text">
613 <p>We have put a significant amount of work into the code generator
614 infrastructure, which allows us to implement more aggressive algorithms and make
619 <li>The <tt>llc -asm-verbose</tt> option (exposed from llvm-gcc as <tt>-dA</tt>
620 and clang as <tt>-fverbose-asm</tt> or <tt>-dA</tt>) now adds a lot of
621 useful information in comments to
622 the generated .s file. This information includes location information (if
623 built with <tt>-g</tt>) and loop nest information.</li>
624 <li>The code generator now supports a new MachineVerifier pass which is useful
625 for finding bugs in targets and codegen passes.</li>
626 <li>The Machine LICM is now enabled by default. It hoists instructions out of
627 loops (such as constant pool loads, loads from read-only stubs, vector
628 constant synthesization code, etc.) and is currently configured to only do
629 so when the hoisted operation can be rematerialized.</li>
630 <li>The Machine Sinking pass is now enabled by default. This pass moves
631 side-effect free operations down the CFG so that they are executed on fewer
632 paths through a function.</li>
633 <li>The code generator now performs "stack slot coloring" of register spills,
634 which allows spill slots to be reused. This leads to smaller stack frames
635 in cases where there are lots of register spills.</li>
636 <li>The register allocator has many improvements to take better advantage of
637 commutable operations, various spiller peephole optimizations, and can now
638 coalesce cross-register-class copies.</li>
639 <li>Tblgen now supports multiclass inheritance and a number of new string and
640 list operations like <tt>!(subst)</tt>, <tt>!(foreach)</tt>, <tt>!car</tt>,
641 <tt>!cdr</tt>, <tt>!null</tt>, <tt>!if</tt>, <tt>!cast</tt>.
642 These make the .td files more expressive and allow more aggressive factoring
643 of duplication across instruction patterns.</li>
644 <li>Target-specific intrinsics can now be added without having to hack VMCore to
645 add them. This makes it easier to maintain out-of-tree targets.</li>
646 <li>The instruction selector is better at propagating information about values
647 (such as whether they are sign/zero extended etc.) across basic block
649 <li>The SelectionDAG datastructure has new nodes for representing buildvector
650 and <a href="http://llvm.org/PR2957">vector shuffle</a> operations. This
651 makes operations and pattern matching more efficient and easier to get
653 <li>The Prolog/Epilog Insertion Pass now has experimental support for performing
654 the "shrink wrapping" optimization, which moves spills and reloads around in
655 the CFG to avoid doing saves on paths that don't need them.</li>
656 <li>LLVM includes new experimental support for writing ELF .o files directly
657 from the compiler. It works well for many simple C testcases, but doesn't
658 support exception handling, debug info, inline assembly, etc.</li>
659 <li>Targets can now specify register allocation hints through
660 <tt>MachineRegisterInfo::setRegAllocationHint</tt>. A regalloc hint consists
661 of hint type and physical register number. A hint type of zero specifies a
662 register allocation preference. Other hint type values are target specific
663 which are resolved by <tt>TargetRegisterInfo::ResolveRegAllocHint</tt>. An
664 example is the ARM target which uses register hints to request that the
665 register allocator provide an even / odd register pair to two virtual
670 <!--=========================================================================-->
671 <div class="doc_subsection">
672 <a name="x86">X86-32 and X86-64 Target Improvements</a>
675 <div class="doc_text">
676 <p>New features of the X86 target include:
681 <li>SSE 4.2 builtins are now supported.</li>
682 <li>GCC-compatible soft float modes are now supported, which are typically used
684 <li>X86-64 now models implicit zero extensions better, which allows the code
685 generator to remove a lot of redundant zexts. It also models the 8-bit "H"
686 registers as subregs, which allows them to be used in some tricky
688 <li>X86-64 now supports the "local exec" and "initial exec" thread local storage
690 <li>The vector forms of the <a href="LangRef.html#i_icmp">icmp</a> and <a
691 href="LangRef.html#i_fcmp">fcmp</a> instructions now select to efficient
693 <li>Support for the win64 calling conventions have improved. The primary
694 missing feature is support for varargs function definitions. It seems to
695 work well for many win64 JIT purposes.</li>
696 <li>The X86 backend has preliminary support for <a
697 href="CodeGenerator.html#x86_memory">mapping address spaces to segment
698 register references</a>. This allows you to write GS or FS relative memory
699 accesses directly in LLVM IR for cases where you know exactly what you're
700 doing (such as in an OS kernel). There are some known problems with this
701 support, but it works in simple cases.</li>
702 <li>The X86 code generator has been refactored to move all global variable
703 reference logic to one place
704 (<tt>X86Subtarget::ClassifyGlobalReference</tt>) which
705 makes it easier to reason about.</li>
711 <!--=========================================================================-->
712 <div class="doc_subsection">
713 <a name="pic16">PIC16 Target Improvements</a>
716 <div class="doc_text">
717 <p>New features of the PIC16 target include:
721 <li>Support for floating-point, indirect function calls, and
722 passing/returning aggregate types to functions.
723 <li>The code generator is able to generate debug info into output COFF files.
724 <li>Support for placing an object into a specific section or at a specific
725 address in memory.</li>
728 <p>Things not yet supported:</p>
731 <li>Variable arguments.</li>
732 <li>Interrupts/programs.</li>
737 <!--=========================================================================-->
738 <div class="doc_subsection">
739 <a name="ARM">ARM Target Improvements</a>
742 <div class="doc_text">
743 <p>New features of the ARM target include:
748 <li>Preliminary support for processors, such as the Cortex-A8 and Cortex-A9,
749 that implement version v7-A of the ARM architecture. The ARM backend now
750 supports both the Thumb2 and Advanced SIMD (Neon) instruction sets.</li>
752 <li>The AAPCS-VFP "hard float" calling conventions are also supported with the
753 <tt>-float-abi=hard</tt> flag.</li>
755 <li>The ARM calling convention code is now tblgen generated instead of resorting
759 <p>These features are still somewhat experimental
760 and subject to change. The Neon intrinsics, in particular, may change in future
761 releases of LLVM. ARMv7 support has progressed a lot on top of tree since 2.6
767 <!--=========================================================================-->
768 <div class="doc_subsection">
769 <a name="OtherTarget">Other Target Specific Improvements</a>
772 <div class="doc_text">
773 <p>New features of other targets include:
777 <li>Mips now supports O32 Calling Convention.</li>
778 <li>Many improvements to the 32-bit PowerPC SVR4 ABI (used on powerpc-linux)
779 support, lots of bugs fixed.</li>
780 <li>Added support for the 64-bit PowerPC SVR4 ABI (used on powerpc64-linux).
781 Needs more testing.</li>
786 <!--=========================================================================-->
787 <div class="doc_subsection">
788 <a name="newapis">New Useful APIs</a>
791 <div class="doc_text">
793 <p>This release includes a number of new APIs that are used internally, which
794 may also be useful for external clients.
798 <li>New <a href="http://llvm.org/doxygen/PrettyStackTrace_8h-source.html">
799 <tt>PrettyStackTrace</tt> class</a> allows crashes of llvm tools (and applications
800 that integrate them) to provide more detailed indication of what the
801 compiler was doing at the time of the crash (e.g. running a pass).
802 At the top level for each LLVM tool, it includes the command line arguments.
804 <li>New <a href="http://llvm.org/doxygen/StringRef_8h-source.html">StringRef</a>
805 and <a href="http://llvm.org/doxygen/Twine_8h-source.html">Twine</a> classes
806 make operations on character ranges and
807 string concatenation to be more efficient. <tt>StringRef</tt> is just a <tt>const
808 char*</tt> with a length, <tt>Twine</tt> is a light-weight rope.</li>
809 <li>LLVM has new <tt>WeakVH</tt>, <tt>AssertingVH</tt> and <tt>CallbackVH</tt>
810 classes, which make it easier to write LLVM IR transformations. <tt>WeakVH</tt>
811 is automatically drops to null when the referenced <tt>Value</tt> is deleted,
812 and is updated across a <tt>replaceAllUsesWith</tt> operation.
813 <tt>AssertingVH</tt> aborts the program if the
814 referenced value is destroyed while it is being referenced. <tt>CallbackVH</tt>
815 is a customizable class for handling value references. See <a
816 href="http://llvm.org/doxygen/ValueHandle_8h-source.html">ValueHandle.h</a>
817 for more information.</li>
818 <li>The new '<a href="http://llvm.org/doxygen/Triple_8h-source.html">Triple
819 </a>' class centralizes a lot of logic that reasons about target
821 <li>The new '<a href="http://llvm.org/doxygen/ErrorHandling_8h-source.html">
822 llvm_report_error()</a>' set of APIs allows tools to embed the LLVM
823 optimizer and backend and recover from previously unrecoverable errors.</li>
824 <li>LLVM has new abstractions for <a
825 href="http://llvm.org/doxygen/Atomic_8h-source.html">atomic operations</a>
826 and <a href="http://llvm.org/doxygen/RWMutex_8h-source.html">reader/writer
828 <li>LLVM has new <a href="http://llvm.org/doxygen/SourceMgr_8h-source.html">
829 <tt>SourceMgr</tt> and <tt>SMLoc</tt> classes</a> which implement caret
830 diagnostics and basic include stack processing for simple parsers. It is
831 used by tablegen, llvm-mc, the .ll parser and FileCheck.</li>
837 <!--=========================================================================-->
838 <div class="doc_subsection">
839 <a name="otherimprovements">Other Improvements and New Features</a>
842 <div class="doc_text">
843 <p>Other miscellaneous features include:</p>
846 <li>LLVM now includes a new internal '<a
847 href="http://llvm.org/cmds/FileCheck.html">FileCheck</a>' tool which allows
848 writing much more accurate regression tests that run faster. Please see the
849 <a href="TestingGuide.html#FileCheck">FileCheck section of the Testing
850 Guide</a> for more information.</li>
851 <li>LLVM profile information support has been significantly improved to produce
852 correct use counts, and has support for edge profiling with reduced runtime
853 overhead. Combined, the generated profile information is both more correct and
854 imposes about half as much overhead (2.6. from 12% to 6% overhead on SPEC
856 <li>The C bindings (in the llvm/include/llvm-c directory) include many newly
858 <li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005
859 programming language.</li>
861 <li>The LLVMC driver has several new features:
863 <li>Dynamic plugins now work on Windows.</li>
864 <li>New option property: init. Makes possible to provide default values for
865 options defined in plugins (interface to <tt>cl::init</tt>).</li>
866 <li>New example: Skeleton, shows how to create a standalone LLVMC-based
868 <li>New example: mcc16, a driver for the PIC16 toolchain.</li>
877 <!--=========================================================================-->
878 <div class="doc_subsection">
879 <a name="changes">Major Changes and Removed Features</a>
882 <div class="doc_text">
884 <p>If you're already an LLVM user or developer with out-of-tree changes based
885 on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading
886 from the previous release.</p>
889 <li>The Itanium (IA64) backend has been removed. It was not actively supported
890 and had bitrotted.</li>
891 <li>The BigBlock register allocator has been removed, it had also bitrotted.</li>
892 <li>The C Backend (<tt>-march=c</tt>) is no longer considered part of the LLVM release
893 criteria. We still want it to work, but no one is maintaining it and it lacks
894 support for arbitrary precision integers and other important IR features.</li>
896 <li>All LLVM tools now default to overwriting their output file, behaving more
897 like standard unix tools. Previously, this only happened with the '<tt>-f</tt>'
899 <li>LLVM build now builds all libraries as .a files instead of some
900 libraries as relinked .o files. This requires some APIs like
901 InitializeAllTargets.h.
906 <p>In addition, many APIs have changed in this release. Some of the major LLVM
910 <li>All uses of <tt>hash_set</tt> and <tt>hash_map</tt> have been removed from
911 the LLVM tree and the wrapper headers have been removed.</li>
912 <li>The llvm/Streams.h and <tt>DOUT</tt> member of Debug.h have been removed. The
913 <tt>llvm::Ostream</tt> class has been completely removed and replaced with
914 uses of <tt>raw_ostream</tt>.</li>
915 <li>LLVM's global uniquing tables for <tt>Type</tt>s and <tt>Constant</tt>s have
916 been privatized into members of an <tt>LLVMContext</tt>. A number of APIs
917 now take an <tt>LLVMContext</tt> as a parameter. To smooth the transition
918 for clients that will only ever use a single context, the new
919 <tt>getGlobalContext()</tt> API can be used to access a default global
920 context which can be passed in any and all cases where a context is
922 <li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
923 <li>The <tt>Add</tt>, <tt>Sub</tt> and <tt>Mul</tt> operators are no longer
924 overloaded for floating-point types. Floating-point addition, subtraction
925 and multiplication are now represented with new operators <tt>FAdd</tt>,
926 <tt>FSub</tt> and <tt>FMul</tt>. In the <tt>IRBuilder</tt> API,
927 <tt>CreateAdd</tt>, <tt>CreateSub</tt>, <tt>CreateMul</tt> and
928 <tt>CreateNeg</tt> should only be used for integer arithmetic now;
929 <tt>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt> and
930 <tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
931 <li>The <tt>DynamicLibrary</tt> class can no longer be constructed, its functionality has
932 moved to static member functions.</li>
933 <li><tt>raw_fd_ostream</tt>'s constructor for opening a given filename now
934 takes an extra <tt>Force</tt> argument. If <tt>Force</tt> is set to
935 <tt>false</tt>, an error will be reported if a file with the given name
936 already exists. If <tt>Force</tt> is set to <tt>true</tt>, the file will
937 be silently truncated (which is the behavior before this flag was
939 <li><tt>SCEVHandle</tt> no longer exists, because reference counting is no
940 longer done for <tt>SCEV*</tt> objects, instead <tt>const SCEV*</tt>
943 <li>Many APIs, notably <tt>llvm::Value</tt>, now use the <tt>StringRef</tt>
944 and <tt>Twine</tt> classes instead of passing <tt>const char*</tt>
945 or <tt>std::string</tt>, as described in
946 the <a href="ProgrammersManual.html#string_apis">Programmer's Manual</a>. Most
947 clients should be unaffected by this transition, unless they are used to
948 <tt>Value::getName()</tt> returning a string. Here are some tips on updating to
951 <li><tt>getNameStr()</tt> is still available, and matches the old
952 behavior. Replacing <tt>getName()</tt> calls with this is an safe option,
953 although more efficient alternatives are now possible.</li>
955 <li>If you were just relying on <tt>getName()</tt> being able to be sent to
956 a <tt>std::ostream</tt>, consider migrating
957 to <tt>llvm::raw_ostream</tt>.</li>
959 <li>If you were using <tt>getName().c_str()</tt> to get a <tt>const
960 char*</tt> pointer to the name, you can use <tt>getName().data()</tt>.
961 Note that this string (as before), may not be the entire name if the
962 name contains embedded null characters.</li>
964 <li>If you were using <tt>operator +</tt> on the result of <tt>getName()</tt> and
965 treating the result as an <tt>std::string</tt>, you can either
966 use <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
967 could move to a <tt>Twine</tt> based design.</li>
969 <li><tt>isName()</tt> should be replaced with comparison
970 against <tt>getName()</tt> (this is now efficient).
974 <li>The registration interfaces for backend Targets has changed (what was
975 previously <tt>TargetMachineRegistry</tt>). For backend authors, see the <a
976 href="WritingAnLLVMBackend.html#TargetRegistration">Writing An LLVM Backend</a>
977 guide. For clients, the notable API changes are:
979 <li><tt>TargetMachineRegistry</tt> has been renamed
980 to <tt>TargetRegistry</tt>.</li>
982 <li>Clients should move to using the <tt>TargetRegistry::lookupTarget()</tt>
983 function to find targets.</li>
992 <!-- *********************************************************************** -->
993 <div class="doc_section">
994 <a name="portability">Portability and Supported Platforms</a>
996 <!-- *********************************************************************** -->
998 <div class="doc_text">
1000 <p>LLVM is known to work on the following platforms:</p>
1003 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
1004 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
1006 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
1007 and 64-bit modes.</li>
1008 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
1009 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
1010 support is available for native builds with Visual C++).</li>
1011 <li>Sun UltraSPARC workstations running Solaris 10.</li>
1012 <li>Alpha-based machines running Debian GNU/Linux.</li>
1015 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
1016 to the machine and operating system on which it is built. However, minor
1017 porting may be required to get LLVM to work on new platforms. We welcome your
1018 portability patches and reports of successful builds or error messages.</p>
1022 <!-- *********************************************************************** -->
1023 <div class="doc_section">
1024 <a name="knownproblems">Known Problems</a>
1026 <!-- *********************************************************************** -->
1028 <div class="doc_text">
1030 <p>This section contains significant known problems with the LLVM system,
1031 listed by component. If you run into a problem, please check the <a
1032 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
1033 there isn't already one.</p>
1036 <li>The llvm-gcc bootstrap will fail with some versions of binutils (e.g. 2.15)
1037 with a message of "<tt><a href="http://llvm.org/PR5004">Error: can not do 8
1038 byte pc-relative relocation</a></tt>" when building C++ code. We intend to
1039 fix this on mainline, but a workaround for 2.6 is to upgrade to binutils
1042 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
1043 using the stock GCC 3.x.x series 'out the box',
1044 See: <a href="#brokengcc">Broken versions of GCC and other tools</a>.
1045 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
1046 for x86/x86-64 has been made available from the third party AuroraUX Project
1047 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
1052 <!-- ======================================================================= -->
1053 <div class="doc_subsection">
1054 <a name="experimental">Experimental features included with this release</a>
1057 <div class="doc_text">
1059 <p>The following components of this LLVM release are either untested, known to
1060 be broken or unreliable, or are in early development. These components should
1061 not be relied on, and bugs should not be filed against them, but they may be
1062 useful to some people. In particular, if you would like to work on one of these
1063 components, please contact us on the <a
1064 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
1067 <li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430 and SystemZ backends are
1069 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
1070 supported value for this option. The ELF writer is experimental.</li>
1071 <li>The implementation of Andersen's Alias Analysis has many known bugs.</li>
1076 <!-- ======================================================================= -->
1077 <div class="doc_subsection">
1078 <a name="x86-be">Known problems with the X86 back-end</a>
1081 <div class="doc_text">
1084 <li>The X86 backend does not yet support
1085 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
1086 floating point stack</a>. It supports the 'f' and 't' constraints, but not
1088 <li>The X86 backend generates inefficient floating point code when configured
1089 to generate code for systems that don't have SSE2.</li>
1090 <li>Win64 code generation wasn't widely tested. Everything should work, but we
1091 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
1092 runtime currently due
1093 to <a href="http://llvm.org/PR2255">several</a>
1094 <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
1096 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
1097 <li>The X86-64 backend does not yet support the LLVM IR instruction
1098 <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
1099 argument constructs on X86-64 by lowering them manually.</li>
1104 <!-- ======================================================================= -->
1105 <div class="doc_subsection">
1106 <a name="ppc-be">Known problems with the PowerPC back-end</a>
1109 <div class="doc_text">
1112 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
1113 compilation, and lacks support for debug information.</li>
1118 <!-- ======================================================================= -->
1119 <div class="doc_subsection">
1120 <a name="arm-be">Known problems with the ARM back-end</a>
1123 <div class="doc_text">
1126 <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
1127 and not well tested. Some features may not work at all, and the code quality
1128 may be poor in some cases.</li>
1129 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
1130 processors, thumb programs can crash or produce wrong
1131 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
1132 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
1138 <!-- ======================================================================= -->
1139 <div class="doc_subsection">
1140 <a name="sparc-be">Known problems with the SPARC back-end</a>
1143 <div class="doc_text">
1146 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
1147 support the 64-bit SPARC ABI (-m64).</li>
1152 <!-- ======================================================================= -->
1153 <div class="doc_subsection">
1154 <a name="mips-be">Known problems with the MIPS back-end</a>
1157 <div class="doc_text">
1160 <li>64-bit MIPS targets are not supported yet.</li>
1165 <!-- ======================================================================= -->
1166 <div class="doc_subsection">
1167 <a name="alpha-be">Known problems with the Alpha back-end</a>
1170 <div class="doc_text">
1174 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
1175 appropriate nops inserted to ensure restartability.</li>
1180 <!-- ======================================================================= -->
1181 <div class="doc_subsection">
1182 <a name="c-be">Known problems with the C back-end</a>
1185 <div class="doc_text">
1188 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
1189 inline assembly code</a>.</li>
1190 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
1191 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
1192 C++ code compiled with <tt>llc</tt> or native compilers.</li>
1193 <li>The C backend does not support all exception handling constructs.</li>
1194 <li>The C backend does not support arbitrary precision integers.</li>
1200 <!-- ======================================================================= -->
1201 <div class="doc_subsection">
1202 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
1205 <div class="doc_text">
1207 <p>The only major language feature of GCC not supported by llvm-gcc is
1208 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
1209 are only supported on some targets. For example, trampolines are only
1210 supported on some targets (these are used when you take the address of a
1211 nested function).</p>
1213 <p>If you run into GCC extensions which are not supported, please let us know.
1218 <!-- ======================================================================= -->
1219 <div class="doc_subsection">
1220 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
1223 <div class="doc_text">
1225 <p>The C++ front-end is considered to be fully
1226 tested and works for a number of non-trivial programs, including LLVM
1227 itself, Qt, Mozilla, etc.</p>
1230 <li>Exception handling works well on the X86 and PowerPC targets. Currently
1231 only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
1236 <!-- ======================================================================= -->
1237 <div class="doc_subsection">
1238 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
1241 <div class="doc_text">
1243 <li>Fortran support generally works, but there are still several unresolved bugs
1244 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
1245 tools/gfortran component for details.</li>
1249 <!-- ======================================================================= -->
1250 <div class="doc_subsection">
1251 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
1254 <div class="doc_text">
1255 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
1256 technology, and problems should be expected.
1258 <li>The Ada front-end currently only builds on X86-32. This is mainly due
1259 to lack of trampoline support (pointers to nested functions) on other platforms.
1260 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
1261 which does support trampolines.</li>
1262 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
1263 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
1264 exception handling, which is used internally by the compiler.
1265 Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
1266 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
1267 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
1268 (c380004 also fails with gcc-4.2 mainline).
1269 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
1270 causes the compiler to go into an infinite loop, using up all system memory.</li>
1271 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
1272 <li>The <tt>-E</tt> binder option (exception backtraces)
1273 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
1274 crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
1275 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
1276 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
1277 or use representation clauses that result in a field of a non-discrete type
1278 starting or finishing in the middle of a byte.</li>
1279 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
1280 'main' as generated by the Ada binder to be invalid</a>.
1281 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
1282 <tt>envp</tt> rather than integers.</li>
1283 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
1288 <!-- ======================================================================= -->
1289 <div class="doc_subsection">
1290 <a name="ocaml-bindings">Known problems with the O'Caml bindings</a>
1293 <div class="doc_text">
1295 <p>The <tt>Llvm.Linkage</tt> module is broken, and has incorrect values. Only
1296 <tt>Llvm.Linkage.External</tt>, <tt>Llvm.Linkage.Available_externally</tt>, and
1297 <tt>Llvm.Linkage.Link_once</tt> will be correct. If you need any of the other linkage
1298 modes, you'll have to write an external C library in order to expose the
1299 functionality. This has been fixed in the trunk.</p>
1302 <!-- *********************************************************************** -->
1303 <div class="doc_section">
1304 <a name="additionalinfo">Additional Information</a>
1306 <!-- *********************************************************************** -->
1308 <div class="doc_text">
1310 <p>A wide variety of additional information is available on the <a
1311 href="http://llvm.org">LLVM web page</a>, in particular in the <a
1312 href="http://llvm.org/docs/">documentation</a> section. The web page also
1313 contains versions of the API documentation which is up-to-date with the
1314 Subversion version of the source code.
1315 You can access versions of these documents specific to this release by going
1316 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
1318 <p>If you have any questions or comments about LLVM, please feel free to contact
1319 us via the <a href="http://llvm.org/docs/#maillist"> mailing
1324 <!-- *********************************************************************** -->
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