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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 X86: Support for softfloat modes, typically used by OS kernels.
77 MCInstPrinter did it make it in?
78 MCInst (X86 using it so far)
79 Rewrite of X86 GV selection logic: TargetOperand flags on ExternalSymbol, GV, etc operands.
80 Can parse and re-print out an darwin-x86 .s file.
81 TargetLoweringObjectFile, MCSectionKind
82 Verrrry early start of a macho writer.
84 ELF Writer? How stable?
86 LSR promotes int induction variables to 64-bit on 64-bit targets, major perf boost for numerical code.
87 LSR now analyzes pointer expressions (e.g. getelementptrs), not just integers.
88 Stack slot coloring for register spills (denser stack frames)
89 SelectionDAGS: New BuildVectorSDNode (r65296), and ISD::VECTOR_SHUFFLE (r69952 / PR2957)
90 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.
91 new linkage types linkonce_odr, weak_odr, linker_private, and available_externally.
92 Inliner reuse stack space when inlining arrays?
94 Regalloc hints for allocation stuff: Evan r73381/r73671. Finished/enabled?
96 no use of hash_set/hash_map, no more llvm::OStream
97 Use raw_ostream for everything, killed off llvm/Streams.h and DOUT
99 Mips now supports O32 Calling Convention
101 StringRef class, Twine class.
102 New BlackFin backend.
104 Shrink wrapping support in PEI, what is the state of it?
106 X86-64: better modeling of implicit zero extensions, eliminates a lot of redundant zexts
107 X86-64 TLS support for local exec and initial exec.
108 X86 - Better modeling of H registerts as subregs.
109 Getelementpr instruction now allows any integer type for array/pointer indexes.
111 include/llvm/Analysis/LiveValues.h => dead??
112 lib/Analysis/LoopVR.cpp ==> dead??
113 include/llvm/CodeGen/LazyLiveness.h ==> dead?
114 lib/Transforms/IPO/MergeFunctions.cpp ==> dead?
115 llvm/Analysis/PointerTracking.h ==> dead??
116 PRedSimplify -> Ask vmkit if it is still useful and for testcases.
118 ARM calling convention code is now tblgen generated instead of manual.
119 ARM: NEON support. neonfp for doing single precision fp with neon instead of VFP.
120 Tblgen now supports multiclass inheritance.
121 Unladen swallow as user?
122 Loop index split disabled by default?
124 New WeakVH and AssertingVH and CallbackVH classes.
125 New llvm/ADT/Triple class.
126 Removed the IA64 backend.
127 Profile info improvements by Andreas Neustifter.
128 PostRA scheduler improvements David Goodwin.
130 New MSP430 and SystemZ backends.
131 llvm-gcc now supports a new TCE target.
132 klee web page at klee.llvm.org
133 New llvm/System/Atomic.h, llvm/System/RWMutex.h for portable atomic ops, rw locks.
134 llvm_start_multithreaded: ProgrammersMAnual.html#threading
136 Tablegen now supports a number of new string and list operations like
137 !(subst), !(foreach), !car, !cdr, !null, !if, !cast.
138 New fadd, fsub, fmul instructions and classes.
139 New MachineVerifier pass.
140 Enabled GVN Load PRE.
141 ARM AAPCS-VFP hard float ABI is supported.
143 LLVM build now builds all libraries as .a files instead of some
144 libraries as relinked .o files. This requires some APIs like
145 InitializeAllTargets.h. TargetRegistry!
147 ARM Thumb2 support: status?
148 CBE status: not part of the release criteria.
150 New SourceMgr, SMLoc classes for simple parsers with caret diagnostics and #include support, (used by
151 tablegen, llvm-mc, the .ll parser, FileCheck, etc)
152 FileCheck! + CHECK-NEXT
153 New compiler-rt project.
154 New Static Single Information (SSI) construction pass (not used by anything yet, experimental).
156 llvm_report_error() error handling API (llvm/Support/ErrorHandling.h)
158 x86: Vector icmp/fcmp now work with SSE codegen.
159 X86: all global variable reference logic is now in ClassifyGlobalReference.
160 JIT support for oprofile (r75279), configure with --with-oprofile. Now we get line # and function info for JIT'd functions.
163 New EngineBuilder class for creating JITs: r76276 Reid Kleckner <reid at kleckner.net>
165 -asm-verbose now prints location info (with -g) and loop nest info.
166 JIT now supports generating more than 16M of code.
168 removed the BigBlock register allocator, it had bitrotted.
169 Target intrinsics can now return multiple results.
172 Ada bindings for LLVM IR.
173 Many extensions to the C APIs.
175 <!-- Unfinished features in 2.6:
178 variable debug info for optimized code
179 postalloc scheduler: anti dependence breaking, hazard recognizer?
181 loop dependence analysis
184 <!-- for announcement email:
190 <!-- *********************************************************************** -->
191 <div class="doc_section">
192 <a name="subproj">Sub-project Status Update</a>
194 <!-- *********************************************************************** -->
196 <div class="doc_text">
198 The LLVM 2.6 distribution currently consists of code from the core LLVM
199 repository —which roughly includes the LLVM optimizers, code generators
200 and supporting tools — and the llvm-gcc repository. In addition to this
201 code, the LLVM Project includes other sub-projects that are in development. The
202 two which are the most actively developed are the <a href="#clang">Clang
203 Project</a> and the <a href="#vmkit">VMKit Project</a>.
209 <!--=========================================================================-->
210 <div class="doc_subsection">
211 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
214 <div class="doc_text">
216 <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
217 a set of new 'LLVM native' front-end technologies for the LLVM optimizer and
218 code generator. While Clang is not included in the LLVM 2.6 release, it is
219 continuing to make major strides forward in all areas. Its C and Objective-C
220 parsing and code generation support is now very solid. For example, it is
221 capable of successfully building many real-world applications for X86-32
223 including the <a href="http://wiki.freebsd.org/BuildingFreeBSDWithClang">FreeBSD
224 kernel</a> and <a href="http://gcc.gnu.org/gcc-4.2/">gcc 4.2</a>. C++ is also
225 making <a href="http://clang.llvm.org/cxx_status.html">incredible progress</a>,
226 and work on templates has recently started. If you are
227 interested in fast compiles and good diagnostics, we encourage you to try it out
228 by <a href="http://clang.llvm.org/get_started.html">building from mainline</a>
229 and reporting any issues you hit to the <a
230 href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
233 <p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
236 <li>Something wonderful!</li>
237 <li>AuroraUX / FreeBSD & OpenBSD Toolchain support.</li>
238 <li>Many many bugs are fixed and many features have been added.</li>
242 <!--=========================================================================-->
243 <div class="doc_subsection">
244 <a name="clangsa">Clang Static Analyzer</a>
247 <div class="doc_text">
249 <p>Previously announced in the 2.4 LLVM release, the Clang project also
250 includes an early stage static source code analysis tool for <a
251 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
252 in C and Objective-C programs. The tool performs a growing set of checks to find
253 bugs that occur on a specific path within a program.</p>
255 <p>In the LLVM 2.6 time-frame there have been many significant improvements to
258 <p>The set of checks performed by the static analyzer continues to expand, and
259 future plans for the tool include full source-level inter-procedural analysis
260 and deeper checks such as buffer overrun detection. There are many opportunities
261 to extend and enhance the static analyzer, and anyone interested in working on
262 this project is encouraged to get involved!</p>
266 <!--=========================================================================-->
267 <div class="doc_subsection">
268 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
271 <div class="doc_text">
273 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
274 a JVM and a CLI Virtual Machines (Microsoft .NET is an
275 implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
277 <p>Following LLVM 2.6, VMKit has its XYZ release that you can find on its
278 <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
279 bug fixes, cleanup and new features. The major changes are:</p>
283 <li>Something wonderful!</li>
288 <!-- *********************************************************************** -->
289 <div class="doc_section">
290 <a name="externalproj">External Projects Using LLVM 2.6</a>
292 <!-- *********************************************************************** -->
295 <!--=========================================================================-->
296 <div class="doc_subsection">
297 <a name="macruby">MacRuby</a>
300 <div class="doc_text">
303 <a href="http://macruby.org">MacRuby</a> is an implementation of Ruby on top of
304 core Mac OS X technologies, such as the Objective-C common runtime and garbage
305 collector, and the CoreFoundation framework. It is principally developed by
306 Apple and aims at enabling the creation of full-fledged Mac OS X applications.
310 MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby
311 expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception
317 <!--=========================================================================-->
318 <div class="doc_subsection">
319 <a name="pure">Pure</a>
322 <div class="doc_text">
324 <a href="http://pure-lang.googlecode.com/">Pure</a>
325 is an algebraic/functional programming language based on term rewriting.
326 Programs are collections of equations which are used to evaluate expressions in
327 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
328 lexical closures, a hygienic macro system (also based on term rewriting),
329 built-in list and matrix support (including list and matrix comprehensions) and
330 an easy-to-use C interface. The interpreter uses LLVM as a backend to
331 JIT-compile Pure programs to fast native code.</p>
333 <p>In addition to the usual algebraic data structures, Pure also has
334 MATLAB-style matrices in order to support numeric computations and signal
335 processing in an efficient way. Pure is mainly aimed at mathematical
336 applications right now, but it has been designed as a general purpose language.
337 The dynamic interpreter environment and the C interface make it possible to use
338 it as a kind of functional scripting language for many application areas.
343 <!--=========================================================================-->
344 <div class="doc_subsection">
345 <a name="ldc">LLVM D Compiler</a>
348 <div class="doc_text">
350 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
351 the D Programming Language using the LLVM optimizer and code generator.
352 The LDC project works great with the LLVM 2.6 release. General improvements in
354 cycle have included new inline asm constraint handling, better debug info
355 support, general bugfixes, and better x86-64 support. This has allowed
356 some major improvements in LDC, getting us much closer to being as
357 fully featured as the original DMD compiler from DigitalMars.
361 <!--=========================================================================-->
362 <div class="doc_subsection">
363 <a name="RoadsendPHP">Roadsend PHP</a>
366 <div class="doc_text">
367 <p><a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
368 source implementation of the PHP programming
369 language that uses LLVM for its optimizer, JIT, and static compiler. This is a
370 reimplementation of an earlier project that is now based on LLVM.</p>
373 <!--=========================================================================-->
374 <div class="doc_subsection">
375 <a name="Unladen Swallow">Unladen Swallow</a>
378 <div class="doc_text">
379 <p><a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
380 branch of <a href="http://python.org/">Python</a> intended to be fully
381 compatible and significantly faster. It uses LLVM's optimization passes and JIT
385 <!--=========================================================================-->
386 <div class="doc_subsection">
387 <a name="Rubinius">Rubinius</a>
390 <div class="doc_text">
391 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is a new virtual
392 machine for Ruby. It leverages LLVM to dynamically compile Ruby code down to
393 machine code using LLVM's JIT.</p>
397 <!-- *********************************************************************** -->
398 <div class="doc_section">
399 <a name="whatsnew">What's New in LLVM 2.6?</a>
401 <!-- *********************************************************************** -->
403 <div class="doc_text">
405 <p>This release includes a huge number of bug fixes, performance tweaks, and
406 minor improvements. Some of the major improvements and new features are listed
411 <!--=========================================================================-->
412 <div class="doc_subsection">
413 <a name="majorfeatures">Major New Features</a>
416 <div class="doc_text">
418 <p>LLVM 2.6 includes several major new capabilities:</p>
421 <li>Something wonderful!</li>
422 <li>LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005 programming language.</li>
428 <!--=========================================================================-->
429 <div class="doc_subsection">
430 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
433 <div class="doc_text">
435 <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
436 front-ends and driver with the LLVM optimizer and code generator. It currently
437 includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
440 <li>Something wonderful!</li>
446 <!--=========================================================================-->
447 <div class="doc_subsection">
448 <a name="coreimprovements">LLVM IR and Core Improvements</a>
451 <div class="doc_text">
452 <p>LLVM IR has several new features that are used by our existing front-ends and
453 can be useful if you are writing a front-end for LLVM:</p>
456 <li>Something wonderful!</li>
461 <!--=========================================================================-->
462 <div class="doc_subsection">
463 <a name="optimizer">Optimizer Improvements</a>
466 <div class="doc_text">
468 <p>In addition to a large array of bug fixes and minor performance tweaks, this
469 release includes a few major enhancements and additions to the optimizers:</p>
473 <li>Something wonderful!</li>
479 <!--=========================================================================-->
480 <div class="doc_subsection">
481 <a name="codegen">Target Independent Code Generator Improvements</a>
484 <div class="doc_text">
486 <p>We have put a significant amount of work into the code generator
487 infrastructure, which allows us to implement more aggressive algorithms and make
492 <li>Something wonderful!</li>
496 <!--=========================================================================-->
497 <div class="doc_subsection">
498 <a name="x86">X86-32 and X86-64 Target Improvements</a>
501 <div class="doc_text">
502 <p>New features of the X86 target include:
507 <li>Something wonderful!</li>
512 <!--=========================================================================-->
513 <div class="doc_subsection">
514 <a name="pic16">PIC16 Target Improvements</a>
517 <div class="doc_text">
518 <p>New features of the PIC16 target include:
522 <li>Something wonderful!</li>
525 <p>Things not yet supported:</p>
528 <li>Floating point.</li>
529 <li>Passing/returning aggregate types to and from functions.</li>
530 <li>Variable arguments.</li>
531 <li>Indirect function calls.</li>
532 <li>Interrupts/programs.</li>
538 <!--=========================================================================-->
539 <div class="doc_subsection">
540 <a name="ARM">ARM Target Improvements</a>
543 <div class="doc_text">
544 <p>New features of the ARM target include:
549 <li>Preliminary support for processors, such as the Cortex-A8 and Cortex-A9,
550 that implement version v7-A of the ARM architecture. The ARM backend now
551 supports both the Thumb2 and Advanced SIMD (Neon) instruction sets. The
552 AAPCS-VFP "hard float" calling conventions are also supported with the
553 <tt>-float-abi=hard</tt> flag. These features are still somewhat experimental
554 and subject to change. The Neon intrinsics, in particular, may change in future
562 <!--=========================================================================-->
563 <div class="doc_subsection">
564 <a name="llvmc">Improvements in LLVMC</a>
567 <div class="doc_text">
568 <p>New features include:</p>
571 <li>Something wonderful!</li>
577 <!--=========================================================================-->
578 <div class="doc_subsection">
579 <a name="changes">Major Changes and Removed Features</a>
582 <div class="doc_text">
584 <p>If you're already an LLVM user or developer with out-of-tree changes based
585 on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading
586 from the previous release.</p>
590 <li>Something horrible!</li>
595 <p>In addition, many APIs have changed in this release. Some of the major LLVM
599 <li>LLVM's global uniquing tables for <tt>Type</tt>s and <tt>Constant</tt>s have
600 been privatized into members of an <tt>LLVMContext</tt>. A number of APIs
601 now take an <tt>LLVMContext</tt> as a parameter. To smooth the transition
602 for clients that will only ever use a single context, the new
603 <tt>getGlobalContext()</tt> API can be used to access a default global
604 context which can be passed in any and all cases where a context is
606 <li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
607 <li>The <tt>Add</tt>, <tt>Sub</tt>, and <tt>Mul</tt> operators are no longer
608 overloaded for floating-point types. Floating-point addition, subtraction,
609 and multiplication are now represented with new operators <tt>FAdd</tt>,
610 <tt>FSub</tt>, and <tt>FMul</tt>. In the <tt>IRBuilder</tt> API,
611 <tt>CreateAdd</tt>, <tt>CreateSub</tt>, <tt>CreateMul</tt>, and
612 <tt>CreateNeg</tt> should only be used for integer arithmetic now;
613 <tt>CreateFAdd</tt>, <tt>CreateFSub</tt>, <tt>CreateFMul</tt>, and
614 <tt>CreateFNeg</tt> should now be used for floating-point arithmetic.</li>
615 <li>The DynamicLibrary class can no longer be constructed, its functionality has
616 moved to static member functions.</li>
617 <li><tt>raw_fd_ostream</tt>'s constructor for opening a given filename now
618 takes an extra <tt>Force</tt> argument. If <tt>Force</tt> is set to
619 <tt>false</tt>, an error will be reported if a file with the given name
620 already exists. If <tt>Force</tt> is set to <tt>true</tt>, the file will
621 be silently truncated (which is the behavior before this flag was
623 <li><tt>SCEVHandle</tt> no longer exists, because reference counting is no
624 longer done for <tt>SCEV*</tt> objects, instead <tt>const SCEV*</tt> should be
627 <li>Many APIs, notably <tt>llvm::Value</tt>, now use the <tt>StringRef</tt>
628 and <tt>Twine</tt> classes instead of passing <tt>const char*</tt>
629 or <tt>std::string</tt>, as described in
630 the <a href="ProgrammersManual.html#string_apis">Programmer's Manual</a>. Most
631 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:
633 <li><tt>getNameStr()</tt> is still available, and matches the old
634 behavior. Replacing <tt>getName()</tt> calls with this is an safe option,
635 although more efficient alternatives are now possible.</li>
637 <li>If you were just relying on <tt>getName()</tt> being able to be sent to
638 a <tt>std::ostream</tt>, consider migrating
639 to <tt>llvm::raw_ostream</tt>.</li>
641 <li>If you were using <tt>getName().c_str()</tt> to get a <tt>const
642 char*</tt> pointer to the name, you can use <tt>getName().data()</tt>.
643 Note that this string (as before), may not be the entire name if the
644 name containts embedded null characters.</li>
646 <li>If you were using operator plus on the result of <tt>getName()</tt> and
647 treating the result as an <tt>std::string</tt>, you can either
648 uses <tt>Twine::str</tt> to get the result as an <tt>std::string</tt>, or
649 could move to a <tt>Twine</tt> based design.</li>
651 <li><tt>isName()</tt> should be replaced with comparison
652 against <tt>getName()</tt> (this is now efficient).
656 <li>The registration interfaces for backend Targets has changed (what was
657 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:
659 <li><tt>TargetMachineRegistry</tt> has been renamed
660 to <tt>TargetRegistry</tt>.</li>
662 <li>Clients should move to using the <tt>TargetRegistry::lookupTarget()</tt>
663 function to find targets.</li>
667 <li>llvm-dis now fails if output file exists, instead of dumping to stdout.
668 FIXME: describe any other tool changes due to the raw_fd_ostream change. FIXME:
669 This is not an API change, maybe there should be a tool changes section?</li>
670 <li>temporarely due to Context API change passes should call doInitialization()
671 method of the pass they inherit from, otherwise Context is NULL.
672 FIXME: remove this entry when this is no longer needed.<li>
679 <!-- *********************************************************************** -->
680 <div class="doc_section">
681 <a name="portability">Portability and Supported Platforms</a>
683 <!-- *********************************************************************** -->
685 <div class="doc_text">
687 <p>LLVM is known to work on the following platforms:</p>
690 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
691 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like systems).</li>
692 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
693 and 64-bit modes.</li>
694 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
695 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
696 support is available for native builds with Visual C++).</li>
697 <li>Sun UltraSPARC workstations running Solaris 10.</li>
698 <li>Alpha-based machines running Debian GNU/Linux.</li>
701 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
702 to the machine and operating system on which it is built. However, minor
703 porting may be required to get LLVM to work on new platforms. We welcome your
704 portability patches and reports of successful builds or error messages.</p>
708 <!-- *********************************************************************** -->
709 <div class="doc_section">
710 <a name="knownproblems">Known Problems</a>
712 <!-- *********************************************************************** -->
714 <div class="doc_text">
716 <p>This section contains significant known problems with the LLVM system,
717 listed by component. If you run into a problem, please check the <a
718 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
719 there isn't already one.</p>
722 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
723 using the stock GCC 3.x.x series 'out the box',
724 See: <a href="#brokengcc">Broken versions of GCC and other tools</a>.
725 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
726 for x86/x64 has been made available from the third party AuroraUX Project
727 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
732 <!-- ======================================================================= -->
733 <div class="doc_subsection">
734 <a name="experimental">Experimental features included with this release</a>
737 <div class="doc_text">
739 <p>The following components of this LLVM release are either untested, known to
740 be broken or unreliable, or are in early development. These components should
741 not be relied on, and bugs should not be filed against them, but they may be
742 useful to some people. In particular, if you would like to work on one of these
743 components, please contact us on the <a
744 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
747 <li>The MSIL, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
748 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
749 supported value for this option.</li>
754 <!-- ======================================================================= -->
755 <div class="doc_subsection">
756 <a name="x86-be">Known problems with the X86 back-end</a>
759 <div class="doc_text">
762 <li>The X86 backend does not yet support
763 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
764 floating point stack</a>. It supports the 'f' and 't' constraints, but not
766 <li>The X86 backend generates inefficient floating point code when configured
767 to generate code for systems that don't have SSE2.</li>
768 <li>Win64 code generation wasn't widely tested. Everything should work, but we
769 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
770 runtime currently due
771 to <a href="http://llvm.org/PR2255">several</a>
772 <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
774 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
775 <li>The X86-64 backend does not yet support the LLVM IR instruction
776 <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
777 argument constructs on X86-64 by lowering them manually.</li>
782 <!-- ======================================================================= -->
783 <div class="doc_subsection">
784 <a name="ppc-be">Known problems with the PowerPC back-end</a>
787 <div class="doc_text">
790 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
791 compilation, and lacks support for debug information.</li>
796 <!-- ======================================================================= -->
797 <div class="doc_subsection">
798 <a name="arm-be">Known problems with the ARM back-end</a>
801 <div class="doc_text">
804 <li>Support for the Advanced SIMD (Neon) instruction set is still incomplete
805 and not well tested. Some features may not work at all, and the code quality
806 may be poor in some cases.</li>
807 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
808 processors, thumb programs can crash or produce wrong
809 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
810 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
812 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
814 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
819 <!-- ======================================================================= -->
820 <div class="doc_subsection">
821 <a name="sparc-be">Known problems with the SPARC back-end</a>
824 <div class="doc_text">
827 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
828 support the 64-bit SPARC ABI (-m64).</li>
833 <!-- ======================================================================= -->
834 <div class="doc_subsection">
835 <a name="mips-be">Known problems with the MIPS back-end</a>
838 <div class="doc_text">
841 <li>The O32 ABI is not fully supported.</li>
842 <li>64-bit MIPS targets are not supported yet.</li>
847 <!-- ======================================================================= -->
848 <div class="doc_subsection">
849 <a name="alpha-be">Known problems with the Alpha back-end</a>
852 <div class="doc_text">
856 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
857 appropriate nops inserted to ensure restartability.</li>
862 <!-- ======================================================================= -->
863 <div class="doc_subsection">
864 <a name="c-be">Known problems with the C back-end</a>
867 <div class="doc_text">
870 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
871 inline assembly code</a>.</li>
872 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
873 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
874 C++ code compiled with <tt>llc</tt> or native compilers.</li>
875 <li>The C backend does not support all exception handling constructs.</li>
876 <li>The C backend does not support arbitrary precision integers.</li>
882 <!-- ======================================================================= -->
883 <div class="doc_subsection">
884 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
887 <div class="doc_text">
889 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
890 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
891 LLVMdev mailing list if you are interested.</p>
893 <p>The only major language feature of GCC not supported by llvm-gcc is
894 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
895 are only supported on some targets. For example, trampolines are only
896 supported on some targets (these are used when you take the address of a
897 nested function).</p>
899 <p>If you run into GCC extensions which are not supported, please let us know.
904 <!-- ======================================================================= -->
905 <div class="doc_subsection">
906 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
909 <div class="doc_text">
911 <p>The C++ front-end is considered to be fully
912 tested and works for a number of non-trivial programs, including LLVM
913 itself, Qt, Mozilla, etc.</p>
916 <li>Exception handling works well on the X86 and PowerPC targets. Currently
917 only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
922 <!-- ======================================================================= -->
923 <div class="doc_subsection">
924 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
927 <div class="doc_text">
929 <li>Fortran support generally works, but there are still several unresolved bugs
930 in Bugzilla. Please see the tools/gfortran component for details.</li>
934 <!-- ======================================================================= -->
935 <div class="doc_subsection">
936 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
939 <div class="doc_text">
940 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
941 technology, and problems should be expected.
943 <li>The Ada front-end currently only builds on X86-32. This is mainly due
944 to lack of trampoline support (pointers to nested functions) on other platforms.
945 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
946 which does support trampolines.</li>
947 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
948 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
949 exception handling, which is used internally by the compiler.
950 Workaround: configure with --disable-bootstrap.</li>
951 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
952 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
953 (c380004 also fails with gcc-4.2 mainline).
954 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
955 causes the compiler to go into an infinite loop, using up all system memory.</li>
956 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
957 <li>The -E binder option (exception backtraces)
958 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
959 crashing if an exception is raised. Workaround: do not use -E.</li>
960 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
961 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
962 or use representation clauses that result in a field of a non-discrete type
963 starting or finishing in the middle of a byte.</li>
964 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
965 'main' as generated by the Ada binder to be invalid</a>.
966 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
967 <tt>envp</tt> rather than integers.</li>
968 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
973 <!-- ======================================================================= -->
974 <div class="doc_subsection">
975 <a name="ocaml-bindingse">Known problems with the O'Caml bindings</a>
978 <div class="doc_text">
980 <p>The Llvm.Linkage module is broken, and has incorrect values. Only
981 Llvm.Linkage.External, Llvm.Linkage.Available_externally, and
982 Llvm.Linkage.Link_once will be correct. If you need any of the other linkage
983 modes, you'll have to write an external C library in order to expose the
984 functionality. This has been fixed in the trunk.</p>
987 <!-- *********************************************************************** -->
988 <div class="doc_section">
989 <a name="additionalinfo">Additional Information</a>
991 <!-- *********************************************************************** -->
993 <div class="doc_text">
995 <p>A wide variety of additional information is available on the <a
996 href="http://llvm.org">LLVM web page</a>, in particular in the <a
997 href="http://llvm.org/docs/">documentation</a> section. The web page also
998 contains versions of the API documentation which is up-to-date with the
999 Subversion version of the source code.
1000 You can access versions of these documents specific to this release by going
1001 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
1003 <p>If you have any questions or comments about LLVM, please feel free to contact
1004 us via the <a href="http://llvm.org/docs/#maillist"> mailing
1009 <!-- *********************************************************************** -->
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