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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 <!-- Unfinished features in 2.5:
58 target-specific intrinsics
60 pre-alloc splitter, strong phi elim
61 <tt>llc -enable-value-prop</tt>, propagation of value info
62 (sign/zero ext info) from one MBB to another
63 debug info for optimized code
65 postalloc scheduler: anti dependence breaking, hazard recognizer?
67 initial support for debug line numbers when optimization enabled, not useful in
68 2.5 but will be for 2.6.
72 <!-- for announcement email:
75 <!-- *********************************************************************** -->
76 <div class="doc_section">
77 <a name="subproj">Sub-project Status Update</a>
79 <!-- *********************************************************************** -->
81 <div class="doc_text">
83 The LLVM 2.6 distribution currently consists of code from the core LLVM
84 repository —which roughly includes the LLVM optimizers, code generators
85 and supporting tools — and the llvm-gcc repository. In addition to this
86 code, the LLVM Project includes other sub-projects that are in development. The
87 two which are the most actively developed are the <a href="#clang">Clang
88 Project</a> and the <a href="#vmkit">VMKit Project</a>.
94 <!--=========================================================================-->
95 <div class="doc_subsection">
96 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
99 <div class="doc_text">
101 <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
102 a set of new 'LLVM native' front-end technologies for the LLVM optimizer and
103 code generator. While Clang is not included in the LLVM 2.6 release, it is
104 continuing to make major strides forward in all areas. Its C and Objective-C
105 parsing and code generation support is now very solid. For example, it is
106 capable of successfully building many real-world applications for X86-32
108 including the <a href="http://wiki.freebsd.org/BuildingFreeBSDWithClang">FreeBSD
109 kernel</a> and <a href="http://gcc.gnu.org/gcc-4.2/">gcc 4.2</a>. C++ is also
110 making <a href="http://clang.llvm.org/cxx_status.html">incredible progress</a>,
111 and work on templates has recently started. If you are
112 interested in fast compiles and good diagnostics, we encourage you to try it out
113 by <a href="http://clang.llvm.org/get_started.html">building from mainline</a>
114 and reporting any issues you hit to the <a
115 href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
118 <p>In the LLVM 2.6 time-frame, the Clang team has made many improvements:</p>
121 <li>Something wonderful!</li>
122 <li>Many many bugs are fixed and many features have been added.</li>
126 <!--=========================================================================-->
127 <div class="doc_subsection">
128 <a name="clangsa">Clang Static Analyzer</a>
131 <div class="doc_text">
133 <p>Previously announced in the 2.4 LLVM release, the Clang project also
134 includes an early stage static source code analysis tool for <a
135 href="http://clang.llvm.org/StaticAnalysis.html">automatically finding bugs</a>
136 in C and Objective-C programs. The tool performs a growing set of checks to find
137 bugs that occur on a specific path within a program.</p>
139 <p>In the LLVM 2.6 time-frame there have been many significant improvements to
142 <p>The set of checks performed by the static analyzer continues to expand, and
143 future plans for the tool include full source-level inter-procedural analysis
144 and deeper checks such as buffer overrun detection. There are many opportunities
145 to extend and enhance the static analyzer, and anyone interested in working on
146 this project is encouraged to get involved!</p>
150 <!--=========================================================================-->
151 <div class="doc_subsection">
152 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
155 <div class="doc_text">
157 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
158 a JVM and a CLI Virtual Machines (Microsoft .NET is an
159 implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
161 <p>Following LLVM 2.6, VMKit has its XYZ release that you can find on its
162 <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
163 bug fixes, cleanup and new features. The major changes are:</p>
167 <li>Something wonderful!</li>
172 <!-- *********************************************************************** -->
173 <div class="doc_section">
174 <a name="externalproj">External Projects Using LLVM 2.6</a>
176 <!-- *********************************************************************** -->
178 <!--=========================================================================-->
179 <div class="doc_subsection">
180 <a name="pure">Pure</a>
183 <div class="doc_text">
185 <a href="http://pure-lang.googlecode.com/">Pure</a>
186 is an algebraic/functional programming language based on term rewriting.
187 Programs are collections of equations which are used to evaluate expressions in
188 a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
189 lexical closures, a hygienic macro system (also based on term rewriting),
190 built-in list and matrix support (including list and matrix comprehensions) and
191 an easy-to-use C interface. The interpreter uses LLVM as a backend to
192 JIT-compile Pure programs to fast native code.</p>
194 <p>In addition to the usual algebraic data structures, Pure also has
195 MATLAB-style matrices in order to support numeric computations and signal
196 processing in an efficient way. Pure is mainly aimed at mathematical
197 applications right now, but it has been designed as a general purpose language.
198 The dynamic interpreter environment and the C interface make it possible to use
199 it as a kind of functional scripting language for many application areas.
204 <!--=========================================================================-->
205 <div class="doc_subsection">
206 <a name="ldc">LLVM D Compiler</a>
209 <div class="doc_text">
211 <a href="http://www.dsource.org/projects/ldc">LDC</a> is an implementation of
212 the D Programming Language using the LLVM optimizer and code generator.
213 The LDC project works great with the LLVM 2.6 release. General improvements in
215 cycle have included new inline asm constraint handling, better debug info
216 support, general bugfixes, and better x86-64 support. This has allowed
217 some major improvements in LDC, getting us much closer to being as
218 fully featured as the original DMD compiler from DigitalMars.
222 <!--=========================================================================-->
223 <div class="doc_subsection">
224 <a name="RoadsendPHP">Roadsend PHP</a>
227 <div class="doc_text">
228 <p><a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
229 source implementation of the PHP programming
230 language that uses LLVM for its optimizer, JIT, and static compiler. This is a
231 reimplementation of an earlier project that is now based on LLVM.</p>
234 <!--=========================================================================-->
235 <div class="doc_subsection">
236 <a name="Unladen Swallow">Unladen Swallow</a>
239 <div class="doc_text">
240 <p><a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
241 branch of <a href="http://python.org/">Python</a> intended to be fully
242 compatible and significantly faster. It uses LLVM's optimization passes and JIT
246 <!--=========================================================================-->
247 <div class="doc_subsection">
248 <a name="Rubinius">Rubinius</a>
251 <div class="doc_text">
252 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is a new virtual
253 machine for Ruby. It leverages LLVM to dynamically compile Ruby code down to
254 machine code using LLVM's JIT.</p>
258 <!-- *********************************************************************** -->
259 <div class="doc_section">
260 <a name="whatsnew">What's New in LLVM 2.6?</a>
262 <!-- *********************************************************************** -->
264 <div class="doc_text">
266 <p>This release includes a huge number of bug fixes, performance tweaks, and
267 minor improvements. Some of the major improvements and new features are listed
272 <!--=========================================================================-->
273 <div class="doc_subsection">
274 <a name="majorfeatures">Major New Features</a>
277 <div class="doc_text">
279 <p>LLVM 2.6 includes several major new capabilities:</p>
282 <li>Something wonderful!</li>
288 <!--=========================================================================-->
289 <div class="doc_subsection">
290 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
293 <div class="doc_text">
295 <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
296 front-ends and driver with the LLVM optimizer and code generator. It currently
297 includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
300 <li>Something wonderful!</li>
306 <!--=========================================================================-->
307 <div class="doc_subsection">
308 <a name="coreimprovements">LLVM IR and Core Improvements</a>
311 <div class="doc_text">
312 <p>LLVM IR has several new features that are used by our existing front-ends and
313 can be useful if you are writing a front-end for LLVM:</p>
316 <li>Something wonderful!</li>
321 <!--=========================================================================-->
322 <div class="doc_subsection">
323 <a name="optimizer">Optimizer Improvements</a>
326 <div class="doc_text">
328 <p>In addition to a large array of bug fixes and minor performance tweaks, this
329 release includes a few major enhancements and additions to the optimizers:</p>
333 <li>Something wonderful!</li>
339 <!--=========================================================================-->
340 <div class="doc_subsection">
341 <a name="codegen">Target Independent Code Generator Improvements</a>
344 <div class="doc_text">
346 <p>We have put a significant amount of work into the code generator
347 infrastructure, which allows us to implement more aggressive algorithms and make
352 <li>Something wonderful!</li>
356 <!--=========================================================================-->
357 <div class="doc_subsection">
358 <a name="x86">X86-32 and X86-64 Target Improvements</a>
361 <div class="doc_text">
362 <p>New features of the X86 target include:
367 <li>Something wonderful!</li>
372 <!--=========================================================================-->
373 <div class="doc_subsection">
374 <a name="pic16">PIC16 Target Improvements</a>
377 <div class="doc_text">
378 <p>New features of the PIC16 target include:
382 <li>Something wonderful!</li>
385 <p>Things not yet supported:</p>
388 <li>Floating point.</li>
389 <li>Passing/returning aggregate types to and from functions.</li>
390 <li>Variable arguments.</li>
391 <li>Indirect function calls.</li>
392 <li>Interrupts/programs.</li>
399 <!--=========================================================================-->
400 <div class="doc_subsection">
401 <a name="llvmc">Improvements in LLVMC</a>
404 <div class="doc_text">
405 <p>New features include:</p>
408 <li>Something wonderful!</li>
414 <!--=========================================================================-->
415 <div class="doc_subsection">
416 <a name="changes">Major Changes and Removed Features</a>
419 <div class="doc_text">
421 <p>If you're already an LLVM user or developer with out-of-tree changes based
422 on LLVM 2.4, this section lists some "gotchas" that you may run into upgrading
423 from the previous release.</p>
427 <li>Something horrible!</li>
432 <p>In addition, many APIs have changed in this release. Some of the major LLVM
436 <li>The <tt>getABITypeSize</tt> methods are now called <tt>getAllocSize</tt>.</li>
443 <!-- *********************************************************************** -->
444 <div class="doc_section">
445 <a name="portability">Portability and Supported Platforms</a>
447 <!-- *********************************************************************** -->
449 <div class="doc_text">
451 <p>LLVM is known to work on the following platforms:</p>
454 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
455 Linux, Fedora Core and FreeBSD (and probably other unix-like systems).</li>
456 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
457 and 64-bit modes.</li>
458 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
459 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
460 support is available for native builds with Visual C++).</li>
461 <li>Sun UltraSPARC workstations running Solaris 10.</li>
462 <li>Alpha-based machines running Debian GNU/Linux.</li>
463 <li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
466 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
467 to the machine and operating system on which it is built. However, minor
468 porting may be required to get LLVM to work on new platforms. We welcome your
469 portability patches and reports of successful builds or error messages.</p>
473 <!-- *********************************************************************** -->
474 <div class="doc_section">
475 <a name="knownproblems">Known Problems</a>
477 <!-- *********************************************************************** -->
479 <div class="doc_text">
481 <p>This section contains significant known problems with the LLVM system,
482 listed by component. If you run into a problem, please check the <a
483 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
484 there isn't already one.</p>
488 <!-- ======================================================================= -->
489 <div class="doc_subsection">
490 <a name="experimental">Experimental features included with this release</a>
493 <div class="doc_text">
495 <p>The following components of this LLVM release are either untested, known to
496 be broken or unreliable, or are in early development. These components should
497 not be relied on, and bugs should not be filed against them, but they may be
498 useful to some people. In particular, if you would like to work on one of these
499 components, please contact us on the <a
500 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
503 <li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
504 <li>The <tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
505 supported value for this option.</li>
510 <!-- ======================================================================= -->
511 <div class="doc_subsection">
512 <a name="x86-be">Known problems with the X86 back-end</a>
515 <div class="doc_text">
518 <li>The X86 backend does not yet support
519 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
520 floating point stack</a>. It supports the 'f' and 't' constraints, but not
522 <li>The X86 backend generates inefficient floating point code when configured
523 to generate code for systems that don't have SSE2.</li>
524 <li>Win64 code generation wasn't widely tested. Everything should work, but we
525 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
526 runtime currently due
527 to <a href="http://llvm.org/PR2255">several</a>
528 <a href="http://llvm.org/PR2257">bugs</a> and due to lack of support for
530 'u' inline assembly constraint and for X87 floating point inline assembly.</li>
531 <li>The X86-64 backend does not yet support the LLVM IR instruction
532 <tt>va_arg</tt>. Currently, the llvm-gcc and front-ends support variadic
533 argument constructs on X86-64 by lowering them manually.</li>
538 <!-- ======================================================================= -->
539 <div class="doc_subsection">
540 <a name="ppc-be">Known problems with the PowerPC back-end</a>
543 <div class="doc_text">
546 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
547 compilation, and lacks support for debug information.</li>
552 <!-- ======================================================================= -->
553 <div class="doc_subsection">
554 <a name="arm-be">Known problems with the ARM back-end</a>
557 <div class="doc_text">
560 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
561 processors, thumb programs can crash or produce wrong
562 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
563 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
565 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
567 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
572 <!-- ======================================================================= -->
573 <div class="doc_subsection">
574 <a name="sparc-be">Known problems with the SPARC back-end</a>
577 <div class="doc_text">
580 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
581 support the 64-bit SPARC ABI (-m64).</li>
586 <!-- ======================================================================= -->
587 <div class="doc_subsection">
588 <a name="mips-be">Known problems with the MIPS back-end</a>
591 <div class="doc_text">
594 <li>The O32 ABI is not fully supported.</li>
595 <li>64-bit MIPS targets are not supported yet.</li>
600 <!-- ======================================================================= -->
601 <div class="doc_subsection">
602 <a name="alpha-be">Known problems with the Alpha back-end</a>
605 <div class="doc_text">
609 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
610 appropriate nops inserted to ensure restartability.</li>
615 <!-- ======================================================================= -->
616 <div class="doc_subsection">
617 <a name="ia64-be">Known problems with the IA64 back-end</a>
620 <div class="doc_text">
623 <li>The Itanium backend is highly experimental and has a number of known
624 issues. We are looking for a maintainer for the Itanium backend. If you
625 are interested, please contact the LLVMdev mailing list.</li>
630 <!-- ======================================================================= -->
631 <div class="doc_subsection">
632 <a name="c-be">Known problems with the C back-end</a>
635 <div class="doc_text">
638 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
639 inline assembly code</a>.</li>
640 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
641 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
642 C++ code compiled with <tt>llc</tt> or native compilers.</li>
643 <li>The C backend does not support all exception handling constructs.</li>
644 <li>The C backend does not support arbitrary precision integers.</li>
650 <!-- ======================================================================= -->
651 <div class="doc_subsection">
652 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
655 <div class="doc_text">
657 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
658 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
659 LLVMdev mailing list if you are interested.</p>
661 <p>The only major language feature of GCC not supported by llvm-gcc is
662 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
663 are only supported on some targets. For example, trampolines are only
664 supported on some targets (these are used when you take the address of a
665 nested function).</p>
667 <p>If you run into GCC extensions which are not supported, please let us know.
672 <!-- ======================================================================= -->
673 <div class="doc_subsection">
674 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
677 <div class="doc_text">
679 <p>The C++ front-end is considered to be fully
680 tested and works for a number of non-trivial programs, including LLVM
681 itself, Qt, Mozilla, etc.</p>
684 <li>Exception handling works well on the X86 and PowerPC targets. Currently
685 only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
690 <!-- ======================================================================= -->
691 <div class="doc_subsection">
692 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
695 <div class="doc_text">
697 <li>Fortran support generally works, but there are still several unresolved bugs
698 in Bugzilla. Please see the tools/gfortran component for details.</li>
702 <!-- ======================================================================= -->
703 <div class="doc_subsection">
704 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
707 <div class="doc_text">
708 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
709 technology, and problems should be expected.
711 <li>The Ada front-end currently only builds on X86-32. This is mainly due
712 to lack of trampoline support (pointers to nested functions) on other platforms.
713 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
714 which does support trampolines.</li>
715 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
716 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
717 exception handling, which is used internally by the compiler.
718 Workaround: configure with --disable-bootstrap.</li>
719 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
720 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
721 (c380004 also fails with gcc-4.2 mainline).
722 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
723 causes the compiler to go into an infinite loop, using up all system memory.</li>
724 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
725 <li>The -E binder option (exception backtraces)
726 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
727 crashing if an exception is raised. Workaround: do not use -E.</li>
728 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
729 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
730 or use representation clauses that result in a field of a non-discrete type
731 starting or finishing in the middle of a byte.</li>
732 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
733 'main' as generated by the Ada binder to be invalid</a>.
734 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
735 <tt>envp</tt> rather than integers.</li>
736 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
741 <!-- *********************************************************************** -->
742 <div class="doc_section">
743 <a name="additionalinfo">Additional Information</a>
745 <!-- *********************************************************************** -->
747 <div class="doc_text">
749 <p>A wide variety of additional information is available on the <a
750 href="http://llvm.org">LLVM web page</a>, in particular in the <a
751 href="http://llvm.org/docs/">documentation</a> section. The web page also
752 contains versions of the API documentation which is up-to-date with the
753 Subversion version of the source code.
754 You can access versions of these documents specific to this release by going
755 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
757 <p>If you have any questions or comments about LLVM, please feel free to contact
758 us via the <a href="http://llvm.org/docs/#maillist"> mailing
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