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7 <title>LLVM 2.4 Release Notes</title>
11 <div class="doc_title">LLVM 2.4 Release Notes</div>
14 <li><a href="#intro">Introduction</a></li>
15 <li><a href="#changes">Major Changes and Sub-project Status</a></li>
16 <li><a href="#whatsnew">What's New?</a></li>
17 <li><a href="GettingStarted.html">Installation Instructions</a></li>
18 <li><a href="#portability">Portability and Supported Platforms</a></li>
19 <li><a href="#knownproblems">Known Problems</a>
20 <li><a href="#additionalinfo">Additional Information</a></li>
23 <div class="doc_author">
24 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
27 <!-- Done through Week-of-Mon-20080324.txt -->
29 <!-- *********************************************************************** -->
30 <div class="doc_section">
31 <a name="intro">Introduction</a>
33 <!-- *********************************************************************** -->
35 <div class="doc_text">
37 <p>This document contains the release notes for the LLVM compiler
38 infrastructure, release 2.4. Here we describe the status of LLVM, including
39 major improvements from the previous release and any known problems. All LLVM
40 releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
41 releases web site</a>.</p>
43 <p>For more information about LLVM, including information about the latest
44 release, please check out the <a href="http://llvm.org/">main LLVM
45 web site</a>. If you have questions or comments, the <a
46 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
47 list</a> is a good place to send them.</p>
49 <p>Note that if you are reading this file from a Subversion checkout or the
50 main LLVM web page, this document applies to the <i>next</i> release, not the
51 current one. To see the release notes for a specific releases, please see the
52 <a href="http://llvm.org/releases/">releases page</a>.</p>
56 <!-- *********************************************************************** -->
57 <div class="doc_section">
58 <a name="changes">Major Changes and Sub-project Status</a>
60 <!-- *********************************************************************** -->
62 <div class="doc_text">
64 <p>This is the fifteenth public release of the LLVM Compiler Infrastructure.
65 It includes a large number of features and refinements from LLVM 2.3.</p>
69 <!-- Unfinished features in 2.4:
75 <!--=========================================================================-->
76 <div class="doc_subsection">
77 <a name="changes">Major Changes in LLVM 2.4</a>
80 <div class="doc_text">
84 <p>LLVM API Changes:</p>
91 <!--=========================================================================-->
92 <div class="doc_subsection">
93 <a name="otherprojects">Other LLVM Sub-Projects</a>
96 <div class="doc_text">
98 The core LLVM 2.4 distribution currently consists of code from the core LLVM
99 repository (which roughly contains the LLVM optimizer, code generators and
100 supporting tools) and the llvm-gcc repository. In addition to this code, the
101 LLVM Project includes other sub-projects that are in development. The two which
102 are the most actively developed are the <a href="#clang">Clang Project</a> and
103 <a href="#vmkit">vmkit Project</a>.
107 <!--=========================================================================-->
108 <div class="doc_subsubsection">
109 <a name="vmkit">vmkit</a>
112 <div class="doc_text">
114 The <a href="http://vmkit.llvm.org/">"vmkit" project</a> is an implementation of
115 a JVM and a CLI Virtual Machines (Microsoft .NET is an
116 implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
122 <!--=========================================================================-->
123 <div class="doc_subsubsection">
124 <a name="clang">Clang</a>
127 <div class="doc_text">
129 <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
130 a set of new 'LLVM native' front-end technologies for the LLVM optimizer
131 and code generator. Clang is continuing to make major strides forward in all
132 areas. Its C and Objective-C parsing support is very solid, and the code
133 generation support is far enough along to build many C applications. While not
134 yet production quality, it is progressing very nicely. In addition, C++
135 front-end work has started to make significant progress.</p>
137 <p>Codegen progress/state
141 <a href="http://clang.llvm.org/StaticAnalysis.html">static analysis tool</a>
147 <!-- *********************************************************************** -->
148 <div class="doc_section">
149 <a name="whatsnew">What's New?</a>
151 <!-- *********************************************************************** -->
153 <div class="doc_text">
155 <p>LLVM 2.4 includes a huge number of bug fixes, performance tweaks and minor
156 improvements. Some of the major improvements and new features are listed in
161 <!--=========================================================================-->
162 <div class="doc_subsection">
163 <a name="majorfeatures">Major New Features</a>
166 <div class="doc_text">
168 <p>LLVM 2.4 includes several major new capabilities:</p>
172 <p>MRVs got generalized to FCAs.</p>
175 <li><p>fast isel, -O0 compile times</p></li>
177 <li><p>Attrs changes?</p></li>
186 <!--=========================================================================-->
187 <div class="doc_subsection">
188 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
191 <div class="doc_text">
193 <p>LLVM 2.4 fully supports the llvm-gcc 4.2 front-end, and includes support
194 for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
205 <!--=========================================================================-->
206 <div class="doc_subsection">
207 <a name="coreimprovements">LLVM Core Improvements</a>
210 <div class="doc_text">
211 <p>New features include:
220 <!--=========================================================================-->
221 <div class="doc_subsection">
222 <a name="optimizer">Optimizer Improvements</a>
225 <div class="doc_text">
227 <p>In addition to a huge array of bug fixes and minor performance tweaks, the
228 LLVM 2.4 optimizers support a few major enhancements:</p>
238 <!--=========================================================================-->
239 <div class="doc_subsection">
240 <a name="codegen">Code Generator Improvements</a>
243 <div class="doc_text">
245 <p>We put a significant amount of work into the code generator infrastructure,
246 which allows us to implement more aggressive algorithms and make it run
250 <li>Selection dag speedups</li>
258 <!--=========================================================================-->
259 <div class="doc_subsection">
260 <a name="x86specific">X86/X86-64 Specific Improvements</a>
263 <div class="doc_text">
264 <p>New target-specific features include:
268 <li>Exception handling is supported by default on x86-64 linux platform.</li>
275 <!--=========================================================================-->
276 <div class="doc_subsection">
277 <a name="targetspecific">Other Target Specific Improvements</a>
280 <div class="doc_text">
281 <p>New target-specific features include:
292 <!--=========================================================================-->
293 <div class="doc_subsection">
294 <a name="otherimprovements">Other Improvements</a>
297 <div class="doc_text">
298 <p>New features include:
307 <!-- *********************************************************************** -->
308 <div class="doc_section">
309 <a name="portability">Portability and Supported Platforms</a>
311 <!-- *********************************************************************** -->
313 <div class="doc_text">
315 <p>LLVM is known to work on the following platforms:</p>
318 <li>Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD
319 (and probably other unix-like systems).</li>
320 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
322 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
323 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
324 support is available for native builds with Visual C++).</li>
325 <li>Sun UltraSPARC workstations running Solaris 10.</li>
326 <li>Alpha-based machines running Debian GNU/Linux.</li>
327 <li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
330 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
331 to the machine and operating system on which it is built. However, minor
332 porting may be required to get LLVM to work on new platforms. We welcome your
333 portability patches and reports of successful builds or error messages.</p>
337 <!-- *********************************************************************** -->
338 <div class="doc_section">
339 <a name="knownproblems">Known Problems</a>
341 <!-- *********************************************************************** -->
343 <div class="doc_text">
345 <p>This section contains all known problems with the LLVM system, listed by
346 component. As new problems are discovered, they will be added to these
347 sections. If you run into a problem, please check the <a
348 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
349 there isn't already one.</p>
353 <!-- ======================================================================= -->
354 <div class="doc_subsection">
355 <a name="experimental">Experimental features included with this release</a>
358 <div class="doc_text">
360 <p>The following components of this LLVM release are either untested, known to
361 be broken or unreliable, or are in early development. These components should
362 not be relied on, and bugs should not be filed against them, but they may be
363 useful to some people. In particular, if you would like to work on one of these
364 components, please contact us on the <a
365 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
368 <li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
369 <li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
370 value for this option.</li>
375 <!-- ======================================================================= -->
376 <div class="doc_subsection">
377 <a name="x86-be">Known problems with the X86 back-end</a>
380 <div class="doc_text">
383 <li>The X86 backend does not yet support
384 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
385 floating point stack</a>. It supports the 'f' and 't' constraints, but not
387 <li>The X86 backend generates inefficient floating point code when configured
388 to generate code for systems that don't have SSE2.</li>
389 <li>Win64 code generation wasn't widely tested. Everything should work, but we
390 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
392 to <a href="http://llvm.org/PR2255">several</a>
393 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
394 'u' inline assembly constraint and X87 floating point inline assembly.</li>
395 <li>The X86-64 backend does not yet support the LLVM IR instruction
396 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
397 argument constructs on X86-64 by lowering them manually.</li>
402 <!-- ======================================================================= -->
403 <div class="doc_subsection">
404 <a name="ppc-be">Known problems with the PowerPC back-end</a>
407 <div class="doc_text">
410 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
411 compilation, and lacks support for debug information.</li>
416 <!-- ======================================================================= -->
417 <div class="doc_subsection">
418 <a name="arm-be">Known problems with the ARM back-end</a>
421 <div class="doc_text">
424 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
425 processors, thumb programs can crash or produce wrong
426 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
427 <li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
429 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
431 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
436 <!-- ======================================================================= -->
437 <div class="doc_subsection">
438 <a name="sparc-be">Known problems with the SPARC back-end</a>
441 <div class="doc_text">
444 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
445 support the 64-bit SPARC ABI (-m64).</li>
450 <!-- ======================================================================= -->
451 <div class="doc_subsection">
452 <a name="alpha-be">Known problems with the Alpha back-end</a>
455 <div class="doc_text">
459 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
460 appropriate nops inserted to ensure restartability.</li>
465 <!-- ======================================================================= -->
466 <div class="doc_subsection">
467 <a name="ia64-be">Known problems with the IA64 back-end</a>
470 <div class="doc_text">
473 <li>The Itanium backend is highly experimental, and has a number of known
474 issues. We are looking for a maintainer for the Itanium backend. If you
475 are interested, please contact the llvmdev mailing list.</li>
480 <!-- ======================================================================= -->
481 <div class="doc_subsection">
482 <a name="c-be">Known problems with the C back-end</a>
485 <div class="doc_text">
488 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
489 inline assembly code</a>.</li>
490 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
491 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
492 C++ code compiled with llc or native compilers.</li>
493 <li>The C backend does not support all exception handling constructs.</li>
499 <!-- ======================================================================= -->
500 <div class="doc_subsection">
501 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
504 <div class="doc_text">
506 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
507 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
508 llvmdev mailing list if you are interested.</p>
510 <p>The only major language feature of GCC not supported by llvm-gcc is
511 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
512 are only supported on some targets. For example, trampolines are only
513 supported on some targets (these are used when you take the address of a
514 nested function).</p>
516 <p>If you run into GCC extensions which are not supported, please let us know.
521 <!-- ======================================================================= -->
522 <div class="doc_subsection">
523 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
526 <div class="doc_text">
528 <p>The C++ front-end is considered to be fully
529 tested and works for a number of non-trivial programs, including LLVM
530 itself, Qt, Mozilla, etc.</p>
533 <li>Exception handling works well on the X86 and PowerPC targets. Currently
534 only linux and darwin targets are supported (both 32 and 64 bit).</li>
540 <!-- ======================================================================= -->
541 <div class="doc_subsection">
542 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
545 <div class="doc_text">
546 The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
547 technology and problems should be expected.
549 <li>The Ada front-end currently only builds on X86-32. This is mainly due
550 to lack of trampoline support (pointers to nested functions) on other platforms,
551 however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
552 which does support trampolines.</li>
553 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
554 Workaround: configure with --disable-bootstrap.</li>
555 <li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
556 fail (c380004 also fails with gcc-4.2 mainline). When built at -O3, the
557 <a href="http://llvm.org/PR2421">cxg2021</a> ACATS test also fails.</li>
558 <li>Some gcc specific Ada tests continue to crash the compiler. The testsuite
559 reports most tests as having failed even though they pass.</li>
560 <li>The -E binder option (exception backtraces)
561 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
562 crashing if an exception is raised. Workaround: do not use -E.</li>
563 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
564 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
565 or use representation clauses that result in a field of a non-discrete type
566 starting or finishing in the middle of a byte.</li>
567 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
568 'main' as generated by the Ada binder to be invalid</a>.
569 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
570 <tt>envp</tt> rather than integers.</li>
571 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
576 <!-- *********************************************************************** -->
577 <div class="doc_section">
578 <a name="additionalinfo">Additional Information</a>
580 <!-- *********************************************************************** -->
582 <div class="doc_text">
584 <p>A wide variety of additional information is available on the <a
585 href="http://llvm.org">LLVM web page</a>, in particular in the <a
586 href="http://llvm.org/docs/">documentation</a> section. The web page also
587 contains versions of the API documentation which is up-to-date with the
588 Subversion version of the source code.
589 You can access versions of these documents specific to this release by going
590 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
592 <p>If you have any questions or comments about LLVM, please feel free to contact
593 us via the <a href="http://llvm.org/docs/#maillist"> mailing
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