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7 <title>LLVM 2.6 Release Notes</title>
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>
55 Many new papers added to /pubs/
56 Machine LICM, hoists things like constant pool loads, loads from readonly stubs, vector constant synthesization code, etc.
58 Regalloc improvements for commuting, various spiller peephole optimizations, cross-class coalescing.
59 Support for debug line numbers when optimization enabled
62 target-specific intrinsics (r63765)
63 <tt>llc -enable-value-prop</tt>, propagation of value info (sign/zero ext info) from one MBB to another
66 Preliminary support for addrspace 256 -> GS, 257 -> FS, known problems: CodeGenerator.html#x86_memory
68 Add support for the PowerPC 64-bit SVR4 ABI.
72 SRoA improvements for vector unions, memset, arbitrary weird bitfield accesses etc. It now produces "strange" sized integers.
74 Callgraph + SCCPassMgr??
75 X86: Support for softfloat modes, typically used by OS kernels.
78 MCInstPrinter did it make it in?
79 MCInst (X86 using it so far)
80 Rewrite of X86 GV selection logic: TargetOperand flags on ExternalSymbol, GV, etc operands.
81 Can parse and re-print out an darwin-x86 .s file.
82 TargetLoweringObjectFile, MCSectionKind
83 Verrrry early start of a macho writer.
85 ELF Writer? How stable?
87 LSR promotes int induction variables to 64-bit on 64-bit targets, major perf boost for numerical code.
88 LSR now analyzes pointer expressions (e.g. getelementptrs), not just integers.
89 Stack slot coloring for register spills (denser stack frames)
90 SelectionDAGS: New BuildVectorSDNode (r65296), and ISD::VECTOR_SHUFFLE (r69952 / PR2957)
91 New PrettyStackTrace, crashes of llvm tools should give some indication of what the compiler was doing at the time of the crash (e.g. running a pass), and print out command line arguments.
92 new linkage types linkonce_odr, weak_odr, linker_private, and available_externally.
93 Inliner reuse stack space when inlining arrays?
95 Regalloc hints for allocation stuff: Evan r73381/r73671. Finished/enabled?
97 no use of hash_set/hash_map, no more llvm::OStream
98 Use raw_ostream for everything, killed off llvm/Streams.h and DOUT
100 Mips now supports O32 Calling Convention
102 StringRef class, Twine class.
103 New BlackFin backend.
105 Shrink wrapping support in PEI, what is the state of it?
107 X86-64: better modeling of implicit zero extensions, eliminates a lot of redundant zexts
108 X86-64 TLS support for local exec and initial exec.
109 X86 - Better modeling of H registerts as subregs.
110 Getelementpr instruction now allows any integer type for array/pointer indexes.
112 include/llvm/Analysis/LiveValues.h => dead??
113 lib/Analysis/LoopVR.cpp ==> dead??
114 include/llvm/CodeGen/LazyLiveness.h ==> dead?
115 lib/Transforms/IPO/MergeFunctions.cpp ==> dead?
116 llvm/Analysis/PointerTracking.h ==> dead??
117 PRedSimplify -> Ask vmkit if it is still useful and for testcases.
119 ARM calling convention code is now tblgen generated instead of manual.
120 ARM: NEON support. neonfp for doing single precision fp with neon instead of VFP.
121 Tblgen now supports multiclass inheritance.
122 Unladen swallow as user?
123 Loop index split disabled by default?
125 New WeakVH and AssertingVH and CallbackVH classes.
126 New llvm/ADT/Triple class.
127 Removed the IA64 backend.
128 Profile info improvements by Andreas Neustifter.
129 PostRA scheduler improvements David Goodwin.
131 New MSP430 and SystemZ backends.
132 llvm-gcc now supports a new TCE target.
133 klee web page at klee.llvm.org
134 New llvm/System/Atomic.h, llvm/System/RWMutex.h for portable atomic ops, rw locks.
135 llvm_start_multithreaded: ProgrammersMAnual.html#threading
137 Tablegen now supports a number of new string and list operations like
138 !(subst), !(foreach), !car, !cdr, !null, !if, !cast.
139 New fadd, fsub, fmul instructions and classes.
140 New MachineVerifier pass.
141 Enabled GVN Load PRE.
142 ARM AAPCS-VFP hard float ABI is supported.
144 LLVM build now builds all libraries as .a files instead of some
145 libraries as relinked .o files. This requires some APIs like
146 InitializeAllTargets.h. TargetRegistry!
148 ARM Thumb2 support: status?
149 CBE status: not part of the release criteria.
151 New SourceMgr, SMLoc classes for simple parsers with caret diagnostics and #include support, (used by
152 tablegen, llvm-mc, the .ll parser, FileCheck, etc)
153 FileCheck! + CHECK-NEXT
154 New compiler-rt project.
155 New Static Single Information (SSI) construction pass (not used by anything yet, experimental).
157 llvm_report_error() error handling API (llvm/Support/ErrorHandling.h)
159 x86: Vector icmp/fcmp now work with SSE codegen.
160 X86: all global variable reference logic is now in ClassifyGlobalReference.
161 JIT support for oprofile (r75279), configure with --with-oprofile. Now we get line # and function info for JIT'd functions.
164 New EngineBuilder class for creating JITs: r76276 Reid Kleckner <reid at kleckner.net>
166 -asm-verbose now prints location info (with -g) and loop nest info.
167 JIT now supports generating more than 16M of code.
169 removed the BigBlock register allocator, it had bitrotted.
170 Target intrinsics can now return multiple results.
173 Ada bindings for LLVM IR.
174 Many extensions to the C APIs.
176 <!-- Unfinished features in 2.6:
179 variable debug info for optimized code
180 postalloc scheduler: anti dependence breaking, hazard recognizer?
182 loop dependence analysis
185 <!-- for announcement email:
191 <!-- *********************************************************************** -->
192 <div class="doc_section">
193 <a name="subproj">Sub-project Status Update</a>
195 <!-- *********************************************************************** -->
197 <div class="doc_text">
199 The LLVM 2.6 distribution currently consists of code from the core LLVM
200 repository —which roughly includes the LLVM optimizers, code generators
201 and supporting tools — and the llvm-gcc repository. In addition to this
202 code, the LLVM Project includes other sub-projects that are in development. The
203 two which are the most actively developed are the <a href="#clang">Clang
204 Project</a> and the <a href="#vmkit">VMKit Project</a>.
210 <!--=========================================================================-->
211 <div class="doc_subsection">
212 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
215 <div class="doc_text">
217 <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
218 a set of new 'LLVM native' front-end technologies for the LLVM optimizer and
219 code generator. While Clang is not included in the LLVM 2.6 release, it is
220 continuing to make major strides forward in all areas. Its C and Objective-C
221 parsing and code generation support is now very solid. For example, it is
222 capable of successfully building many real-world applications for X86-32
224 including the <a href="http://wiki.freebsd.org/BuildingFreeBSDWithClang">FreeBSD
225 kernel</a> and <a href="http://gcc.gnu.org/gcc-4.2/">gcc 4.2</a>. C++ is also
226 making <a href="http://clang.llvm.org/cxx_status.html">incredible progress</a>,
227 and work on templates has recently started. If you are
228 interested in fast compiles and good diagnostics, we encourage you to try it out
229 by <a href="http://clang.llvm.org/get_started.html">building from mainline</a>
230 and reporting any issues you hit to the <a
231 href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
234 <p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
237 <li>Something wonderful!</li>
238 <li>AuroraUX / FreeBSD & OpenBSD Toolchain support.</li>
239 <li>Many many bugs are fixed and many features have been added.</li>
243 <!--=========================================================================-->
244 <div class="doc_subsection">
245 <a name="clangsa">Clang Static Analyzer</a>
248 <div class="doc_text">
250 <p>Previously announced in the 2.4 LLVM release, the Clang project also
251 includes an early stage static source code analysis tool for <a
252 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
253 in C and Objective-C programs. The tool performs a growing set of checks to find
254 bugs that occur on a specific path within a program.</p>
256 <p>In the LLVM 2.6 time-frame there have been many significant improvements to
259 <p>The set of checks performed by the static analyzer continues to expand, and
260 future plans for the tool include full source-level inter-procedural analysis
261 and deeper checks such as buffer overrun detection. There are many opportunities
262 to extend and enhance the static analyzer, and anyone interested in working on
263 this project is encouraged to get involved!</p>
267 <!--=========================================================================-->
268 <div class="doc_subsection">
269 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
272 <div class="doc_text">
274 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
275 a JVM and a CLI Virtual Machines (Microsoft .NET is an
276 implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
278 <p>Following LLVM 2.6, VMKit has its XYZ release that you can find on its
279 <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
280 bug fixes, cleanup and new features. The major changes are:</p>
284 <li>Something wonderful!</li>
289 <!-- *********************************************************************** -->
290 <div class="doc_section">
291 <a name="externalproj">External Projects Using LLVM 2.6</a>
293 <!-- *********************************************************************** -->
296 <!--=========================================================================-->
297 <div class="doc_subsection">
298 <a name="macruby">MacRuby</a>
301 <div class="doc_text">
304 <a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
305 core Mac OS X technologies, such as the Objective-C common runtime and garbage
306 collector, and the CoreFoundation framework. It is principally developed by
307 Apple and aims at enabling the creation of full-fledged Mac OS X applications.
311 MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
312 expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
318 <!--=========================================================================-->
319 <div class="doc_subsection">
320 <a name="pure">Pure</a>
323 <div class="doc_text">
325 <a href="http://pure-lang.googlecode.com/">Pure</a>
326 is an algebraic/functional programming language based on term rewriting.
327 Programs are collections of equations which are used to evaluate expressions in
328 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
329 lexical closures, a hygienic macro system (also based on term rewriting),
330 built-in list and matrix support (including list and matrix comprehensions) and
331 an easy-to-use C interface. The interpreter uses LLVM as a backend to
332 JIT-compile Pure programs to fast native code.</p>
334 <p>In addition to the usual algebraic data structures, Pure also has
335 MATLAB-style matrices in order to support numeric computations and signal
336 processing in an efficient way. Pure is mainly aimed at mathematical
337 applications right now, but it has been designed as a general purpose language.
338 The dynamic interpreter environment and the C interface make it possible to use
339 it as a kind of functional scripting language for many application areas.
344 <!--=========================================================================-->
345 <div class="doc_subsection">
346 <a name="ldc">LLVM D Compiler</a>
349 <div class="doc_text">
351 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
352 the D Programming Language using the LLVM optimizer and code generator.
353 The LDC project works great with the LLVM 2.6 release. General improvements in
355 cycle have included new inline asm constraint handling, better debug info
356 support, general bugfixes, and better x86-64 support. This has allowed
357 some major improvements in LDC, getting us much closer to being as
358 fully featured as the original DMD compiler from DigitalMars.
362 <!--=========================================================================-->
363 <div class="doc_subsection">
364 <a name="RoadsendPHP">Roadsend PHP</a>
367 <div class="doc_text">
368 <p><a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
369 source implementation of the PHP programming
370 language that uses LLVM for its optimizer, JIT, and static compiler. This is a
371 reimplementation of an earlier project that is now based on LLVM.</p>
374 <!--=========================================================================-->
375 <div class="doc_subsection">
376 <a name="Unladen Swallow">Unladen Swallow</a>
379 <div class="doc_text">
380 <p><a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
381 branch of <a href="http://python.org/">Python</a> intended to be fully
382 compatible and significantly faster. It uses LLVM's optimization passes and JIT
386 <!--=========================================================================-->
387 <div class="doc_subsection">
388 <a name="Rubinius">Rubinius</a>
391 <div class="doc_text">
392 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is a new virtual
393 machine for Ruby. It leverages LLVM to dynamically compile Ruby code down to
394 machine code using LLVM's JIT.</p>
398 <!-- *********************************************************************** -->
399 <div class="doc_section">
400 <a name="whatsnew">What's New in LLVM 2.6?</a>
402 <!-- *********************************************************************** -->
404 <div class="doc_text">
406 <p>This release includes a huge number of bug fixes, performance tweaks, and
407 minor improvements. Some of the major improvements and new features are listed
412 <!--=========================================================================-->
413 <div class="doc_subsection">
414 <a name="majorfeatures">Major New Features</a>
417 <div class="doc_text">
419 <p>LLVM 2.6 includes several major new capabilities:</p>
422 <li>Something wonderful!</li>
423 <li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005 programming language.</li>
429 <!--=========================================================================-->
430 <div class="doc_subsection">
431 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
434 <div class="doc_text">
436 <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
437 front-ends and driver with the LLVM optimizer and code generator. It currently
438 includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
441 <li>Something wonderful!</li>
447 <!--=========================================================================-->
448 <div class="doc_subsection">
449 <a name="coreimprovements">LLVM IR and Core Improvements</a>
452 <div class="doc_text">
453 <p>LLVM IR has several new features that are used by our existing front-ends and
454 can be useful if you are writing a front-end for LLVM:</p>
457 <li>Something wonderful!</li>
462 <!--=========================================================================-->
463 <div class="doc_subsection">
464 <a name="optimizer">Optimizer Improvements</a>
467 <div class="doc_text">
469 <p>In addition to a large array of bug fixes and minor performance tweaks, this
470 release includes a few major enhancements and additions to the optimizers:</p>
474 <li>Something wonderful!</li>
480 <!--=========================================================================-->
481 <div class="doc_subsection">
482 <a name="codegen">Target Independent Code Generator Improvements</a>
485 <div class="doc_text">
487 <p>We have put a significant amount of work into the code generator
488 infrastructure, which allows us to implement more aggressive algorithms and make
493 <li>Something wonderful!</li>
497 <!--=========================================================================-->
498 <div class="doc_subsection">
499 <a name="x86">X86-32 and X86-64 Target Improvements</a>
502 <div class="doc_text">
503 <p>New features of the X86 target include:
508 <li>Something wonderful!</li>
513 <!--=========================================================================-->
514 <div class="doc_subsection">
515 <a name="pic16">PIC16 Target Improvements</a>
518 <div class="doc_text">
519 <p>New features of the PIC16 target include:
523 <li>Something wonderful!</li>
526 <p>Things not yet supported:</p>
529 <li>Floating point.</li>
530 <li>Passing/returning aggregate types to and from functions.</li>
531 <li>Variable arguments.</li>
532 <li>Indirect function calls.</li>
533 <li>Interrupts/programs.</li>
539 <!--=========================================================================-->
540 <div class="doc_subsection">
541 <a name="ARM">ARM Target Improvements</a>
544 <div class="doc_text">
545 <p>New features of the ARM target include:
550 <li>Preliminary support for processors, such as the Cortex-A8 and Cortex-A9,
551 that implement version v7-A of the ARM architecture. The ARM backend now
552 supports both the Thumb2 and Advanced SIMD (Neon) instruction sets. The
553 AAPCS-VFP "hard float" calling conventions are also supported with the
554 <tt>-float-abi=hard</tt> flag. These features are still somewhat experimental
555 and subject to change. The Neon intrinsics, in particular, may change in future
563 <!--=========================================================================-->
564 <div class="doc_subsection">
565 <a name="llvmc">Improvements in LLVMC</a>
568 <div class="doc_text">
569 <p>New features include:</p>
572 <li>Something wonderful!</li>
578 <!--=========================================================================-->
579 <div class="doc_subsection">
580 <a name="changes">Major Changes and Removed Features</a>
583 <div class="doc_text">
585 <p>If you're already an LLVM user or developer with out-of-tree changes based
586 on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading
587 from the previous release.</p>
591 <li>Something horrible!</li>
596 <p>In addition, many APIs have changed in this release. Some of the major LLVM
600 <li>LLVM's global uniquing tables for <tt>Type</tt>s and <tt>Constant</tt>s have
601 been privatized into members of an <tt>LLVMContext</tt>. A number of APIs
602 now take an <tt>LLVMContext</tt> as a parameter. To smooth the transition
603 for clients that will only ever use a single context, the new
604 <tt>getGlobalContext()</tt> API can be used to access a default global
605 context which can be passed in any and all cases where a context is
607 <li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
608 <li>The <tt>Add</tt>, <tt>Sub</tt>, and <tt>Mul</tt> operators are no longer
609 overloaded for floating-point types. Floating-point addition, subtraction,
610 and multiplication are now represented with new operators <tt>FAdd</tt>,
611 <tt>FSub</tt>, and <tt>FMul</tt>. In the <tt>IRBuilder</tt> API,
612 <tt>CreateAdd</tt>, <tt>CreateSub</tt>, <tt>CreateMul</tt>, and
613 <tt>CreateNeg</tt> should only be used for integer arithmetic now;
614 <tt>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt>, and
615 <tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
616 <li>The DynamicLibrary class can no longer be constructed, its functionality has
617 moved to static member functions.</li>
618 <li><tt>raw_fd_ostream</tt>'s constructor for opening a given filename now
619 takes an extra <tt>Force</tt> argument. If <tt>Force</tt> is set to
620 <tt>false</tt>, an error will be reported if a file with the given name
621 already exists. If <tt>Force</tt> is set to <tt>true</tt>, the file will
622 be silently truncated (which is the behavior before this flag was
624 <li><tt>SCEVHandle</tt> no longer exists, because reference counting is no
625 longer done for <tt>SCEV*</tt> objects, instead <tt>const SCEV*</tt> should be
628 <li>Many APIs, notably <tt>llvm::Value</tt>, now use the <tt>StringRef</tt>
629 and <tt>Twine</tt> classes instead of passing <tt>const char*</tt>
630 or <tt>std::string</tt>, as described in
631 the <a href="ProgrammersManual.html#string_apis">Programmer's Manual</a>. Most
632 clients should be unaffected by this transition, unless they are used to <tt>Value::getName()</tt> returning a string. Here are some tips on updating to 2.6:
634 <li><tt>getNameStr()</tt> is still available, and matches the old
635 behavior. Replacing <tt>getName()</tt> calls with this is an safe option,
636 although more efficient alternatives are now possible.</li>
638 <li>If you were just relying on <tt>getName()</tt> being able to be sent to
639 a <tt>std::ostream</tt>, consider migrating
640 to <tt>llvm::raw_ostream</tt>.</li>
642 <li>If you were using <tt>getName().c_str()</tt> to get a <tt>const
643 char*</tt> pointer to the name, you can use <tt>getName().data()</tt>.
644 Note that this string (as before), may not be the entire name if the
645 name containts embedded null characters.</li>
647 <li>If you were using operator plus on the result of <tt>getName()</tt> and
648 treating the result as an <tt>std::string</tt>, you can either
649 uses <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
650 could move to a <tt>Twine</tt> based design.</li>
652 <li><tt>isName()</tt> should be replaced with comparison
653 against <tt>getName()</tt> (this is now efficient).
657 <li>The registration interfaces for backend Targets has changed (what was
658 previously TargetMachineRegistry). For backend authors, see the <a href="WritingAnLLVMBackend.html#TargetRegistration">Writing An LLVM Backend</a> guide. For clients, the notable API changes are:
660 <li><tt>TargetMachineRegistry</tt> has been renamed
661 to <tt>TargetRegistry</tt>.</li>
663 <li>Clients should move to using the <tt>TargetRegistry::lookupTarget()</tt>
664 function to find targets.</li>
668 <li>llvm-dis now fails if output file exists, instead of dumping to stdout.
669 FIXME: describe any other tool changes due to the raw_fd_ostream change. FIXME:
670 This is not an API change, maybe there should be a tool changes section?</li>
671 <li>temporarely due to Context API change passes should call doInitialization()
672 method of the pass they inherit from, otherwise Context is NULL.
673 FIXME: remove this entry when this is no longer needed.<li>
680 <!-- *********************************************************************** -->
681 <div class="doc_section">
682 <a name="portability">Portability and Supported Platforms</a>
684 <!-- *********************************************************************** -->
686 <div class="doc_text">
688 <p>LLVM is known to work on the following platforms:</p>
691 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
692 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like systems).</li>
693 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
694 and 64-bit modes.</li>
695 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
696 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
697 support is available for native builds with Visual C++).</li>
698 <li>Sun UltraSPARC workstations running Solaris 10.</li>
699 <li>Alpha-based machines running Debian GNU/Linux.</li>
702 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
703 to the machine and operating system on which it is built. However, minor
704 porting may be required to get LLVM to work on new platforms. We welcome your
705 portability patches and reports of successful builds or error messages.</p>
709 <!-- *********************************************************************** -->
710 <div class="doc_section">
711 <a name="knownproblems">Known Problems</a>
713 <!-- *********************************************************************** -->
715 <div class="doc_text">
717 <p>This section contains significant known problems with the LLVM system,
718 listed by component. If you run into a problem, please check the <a
719 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
720 there isn't already one.</p>
723 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
724 using the stock GCC 3.x.x series 'out the box',
725 See: <a href="#brokengcc">Broken versions of GCC and other tools</a>.
726 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
727 for x86/x64 has been made available from the third party AuroraUX Project
728 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
733 <!-- ======================================================================= -->
734 <div class="doc_subsection">
735 <a name="experimental">Experimental features included with this release</a>
738 <div class="doc_text">
740 <p>The following components of this LLVM release are either untested, known to
741 be broken or unreliable, or are in early development. These components should
742 not be relied on, and bugs should not be filed against them, but they may be
743 useful to some people. In particular, if you would like to work on one of these
744 components, please contact us on the <a
745 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
748 <li>The MSIL, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
749 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
750 supported value for this option.</li>
755 <!-- ======================================================================= -->
756 <div class="doc_subsection">
757 <a name="x86-be">Known problems with the X86 back-end</a>
760 <div class="doc_text">
763 <li>The X86 backend does not yet support
764 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
765 floating point stack</a>. It supports the 'f' and 't' constraints, but not
767 <li>The X86 backend generates inefficient floating point code when configured
768 to generate code for systems that don't have SSE2.</li>
769 <li>Win64 code generation wasn't widely tested. Everything should work, but we
770 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
771 runtime currently due
772 to <a href="http://llvm.org/PR2255">several</a>
773 <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
775 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
776 <li>The X86-64 backend does not yet support the LLVM IR instruction
777 <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
778 argument constructs on X86-64 by lowering them manually.</li>
783 <!-- ======================================================================= -->
784 <div class="doc_subsection">
785 <a name="ppc-be">Known problems with the PowerPC back-end</a>
788 <div class="doc_text">
791 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
792 compilation, and lacks support for debug information.</li>
797 <!-- ======================================================================= -->
798 <div class="doc_subsection">
799 <a name="arm-be">Known problems with the ARM back-end</a>
802 <div class="doc_text">
805 <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
806 and not well tested. Some features may not work at all, and the code quality
807 may be poor in some cases.</li>
808 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
809 processors, thumb programs can crash or produce wrong
810 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
811 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
813 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
815 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
820 <!-- ======================================================================= -->
821 <div class="doc_subsection">
822 <a name="sparc-be">Known problems with the SPARC back-end</a>
825 <div class="doc_text">
828 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
829 support the 64-bit SPARC ABI (-m64).</li>
834 <!-- ======================================================================= -->
835 <div class="doc_subsection">
836 <a name="mips-be">Known problems with the MIPS back-end</a>
839 <div class="doc_text">
842 <li>The O32 ABI is not fully supported.</li>
843 <li>64-bit MIPS targets are not supported yet.</li>
848 <!-- ======================================================================= -->
849 <div class="doc_subsection">
850 <a name="alpha-be">Known problems with the Alpha back-end</a>
853 <div class="doc_text">
857 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
858 appropriate nops inserted to ensure restartability.</li>
863 <!-- ======================================================================= -->
864 <div class="doc_subsection">
865 <a name="c-be">Known problems with the C back-end</a>
868 <div class="doc_text">
871 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
872 inline assembly code</a>.</li>
873 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
874 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
875 C++ code compiled with <tt>llc</tt> or native compilers.</li>
876 <li>The C backend does not support all exception handling constructs.</li>
877 <li>The C backend does not support arbitrary precision integers.</li>
883 <!-- ======================================================================= -->
884 <div class="doc_subsection">
885 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
888 <div class="doc_text">
890 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
891 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
892 LLVMdev mailing list if you are interested.</p>
894 <p>The only major language feature of GCC not supported by llvm-gcc is
895 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
896 are only supported on some targets. For example, trampolines are only
897 supported on some targets (these are used when you take the address of a
898 nested function).</p>
900 <p>If you run into GCC extensions which are not supported, please let us know.
905 <!-- ======================================================================= -->
906 <div class="doc_subsection">
907 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
910 <div class="doc_text">
912 <p>The C++ front-end is considered to be fully
913 tested and works for a number of non-trivial programs, including LLVM
914 itself, Qt, Mozilla, etc.</p>
917 <li>Exception handling works well on the X86 and PowerPC targets. Currently
918 only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
923 <!-- ======================================================================= -->
924 <div class="doc_subsection">
925 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
928 <div class="doc_text">
930 <li>Fortran support generally works, but there are still several unresolved bugs
931 in Bugzilla. Please see the tools/gfortran component for details.</li>
935 <!-- ======================================================================= -->
936 <div class="doc_subsection">
937 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
940 <div class="doc_text">
941 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
942 technology, and problems should be expected.
944 <li>The Ada front-end currently only builds on X86-32. This is mainly due
945 to lack of trampoline support (pointers to nested functions) on other platforms.
946 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
947 which does support trampolines.</li>
948 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
949 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
950 exception handling, which is used internally by the compiler.
951 Workaround: configure with --disable-bootstrap.</li>
952 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
953 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
954 (c380004 also fails with gcc-4.2 mainline).
955 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
956 causes the compiler to go into an infinite loop, using up all system memory.</li>
957 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
958 <li>The -E binder option (exception backtraces)
959 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
960 crashing if an exception is raised. Workaround: do not use -E.</li>
961 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
962 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
963 or use representation clauses that result in a field of a non-discrete type
964 starting or finishing in the middle of a byte.</li>
965 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
966 'main' as generated by the Ada binder to be invalid</a>.
967 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
968 <tt>envp</tt> rather than integers.</li>
969 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
974 <!-- ======================================================================= -->
975 <div class="doc_subsection">
976 <a name="ocaml-bindingse">Known problems with the O'Caml bindings</a>
979 <div class="doc_text">
981 <p>The Llvm.Linkage module is broken, and has incorrect values. Only
982 Llvm.Linkage.External, Llvm.Linkage.Available_externally, and
983 Llvm.Linkage.Link_once will be correct. If you need any of the other linkage
984 modes, you'll have to write an external C library in order to expose the
985 functionality. This has been fixed in the trunk.</p>
988 <!-- *********************************************************************** -->
989 <div class="doc_section">
990 <a name="additionalinfo">Additional Information</a>
992 <!-- *********************************************************************** -->
994 <div class="doc_text">
996 <p>A wide variety of additional information is available on the <a
997 href="http://llvm.org">LLVM web page</a>, in particular in the <a
998 href="http://llvm.org/docs/">documentation</a> section. The web page also
999 contains versions of the API documentation which is up-to-date with the
1000 Subversion version of the source code.
1001 You can access versions of these documents specific to this release by going
1002 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
1004 <p>If you have any questions or comments about LLVM, please feel free to contact
1005 us via the <a href="http://llvm.org/docs/#maillist"> mailing
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