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7 <title>LLVM 2.3 Release Notes</title>
11 <div class="doc_title">LLVM 2.3 Release Notes</div>
14 <li><a href="#intro">Introduction</a></li>
15 <li><a href="#whatsnew">What's New?</a></li>
16 <li><a href="GettingStarted.html">Installation Instructions</a></li>
17 <li><a href="#portability">Portability and Supported Platforms</a></li>
18 <li><a href="#knownproblems">Known Problems</a>
19 <li><a href="#additionalinfo">Additional Information</a></li>
22 <div class="doc_author">
23 <p>Written by the <a href="http://llvm.org">LLVM Team</a><p>
26 <!-- *********************************************************************** -->
27 <div class="doc_section">
28 <a name="intro">Introduction</a>
30 <!-- *********************************************************************** -->
32 <div class="doc_text">
34 <p>This document contains the release notes for the LLVM compiler
35 infrastructure, release 2.3. Here we describe the status of LLVM, including
36 major improvements from the previous release and any known problems. All LLVM
37 releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
38 releases web site</a>.</p>
40 <p>For more information about LLVM, including information about the latest
41 release, please check out the <a href="http://llvm.org/">main LLVM
42 web site</a>. If you have questions or comments, the <a
43 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM developer's mailing
44 list</a> is a good place to send them.</p>
46 <p>Note that if you are reading this file from a Subversion checkout or the
47 main LLVM web page, this document applies to the <i>next</i> release, not the
48 current one. To see the release notes for a specific releases, please see the
49 <a href="http://llvm.org/releases/">releases page</a>.</p>
53 <!-- *********************************************************************** -->
54 <div class="doc_section">
55 <a name="whatsnew">What's New?</a>
57 <!-- *********************************************************************** -->
59 <div class="doc_text">
61 <p>This is the fourteenth public release of the LLVM Compiler Infrastructure.
62 It includes a large number of features and refinements from LLVM 2.2.</p>
66 <!-- Unfinished features in 2.3:
67 Index Set Splitting not enabled by default
73 <!--=========================================================================-->
74 <div class="doc_subsection">
75 <a name="deprecation">Removed features in LLVM 2.3</a>
78 <div class="doc_text">
80 <p>LLVM 2.2 was the last LLVM release to support llvm-gcc 4.0 and llvm-upgrade.
81 llvm-gcc 4.0 has been replaced with llvm-gcc 4.2. llvm-upgrade was useful for
82 upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a previous
83 LLVM release to do this. One nice impact of this is that the LLVM regressionn
84 test suite no longer depends on llvm-upgrade, which makes it run faster.</p>
88 <!--=========================================================================-->
89 <div class="doc_subsection">
90 <a name="majorfeatures">Major New Features</a>
93 <div class="doc_text">
95 <p>LLVM 2.3 includes several major new capabilities:</p>
98 <li>Multiple Return Value Support</li>
101 <li><p>LLVM 2.3 includes a complete reimplementation of the "llvmc" tool. It is
102 designed to overcome several problems of the original llvmc and to provide a
103 superset of the features as the 'gcc' driver.</p>
105 <p>The main features of llvmc2 is:</p>
108 <li>Extended handling of command line options and smart rules for
109 dispatching them to different tools.</li>
110 <li>Flexible (and extensible) rules for defining different tools.</li>
111 <li>The different intermediate steps performed by tools are represented
112 as edged in the abstract graph.</li>
113 </l>The 'language' for driver behaviour definition is tablegen and thus
114 it's relatively easy to add new features.</li>
115 <li>The definition of driver is transformed into set of C++ classes, thus
116 no runtime interpretation is needed.</li>
129 <!--=========================================================================-->
130 <div class="doc_subsection">
131 <a name="frontends">llvm-gcc 4.2 Improvements and Clang</a>
134 <div class="doc_text">
136 <p>LLVM 2.3 fully supports llvm-gcc 4.2 front-end.</p>
138 <p>llvm-gcc 4.2 includes numerous fixes to better support the Objective-C
139 front-end. Objective-C now works very well on Mac OS/X.</p>
141 <p>llvm-gcc 4.2 includes many other fixes which improve conformance with the
142 relevant parts of the GCC testsuite.</p>
144 <p>The <a href="http://clang.llvm.org/">clang project</a> is an effort to build
145 a set of new 'llvm native' front-end technologies for the LLVM optimizer
146 and code generator. Currently, its C and Objective-C support is maturing
147 nicely, and it has advanced source-to-source analysis and transformation
148 capabilities. If you are interested in building source-level tools for C and
149 Objective-C (and eventually C++), you should take a look. However, note that
150 clang is not an official part of the LLVM 2.3 release. If you are interested in
151 this project, please see its <a href="http://clang.llvm.org/">web site</a>.</p>
156 <!--=========================================================================-->
157 <div class="doc_subsection">
158 <a name="coreimprovements">LLVM Core Improvements</a>
161 <div class="doc_text">
162 <p>New features include:
168 Atomic operation support, Alpha, X86, PowerPC. "__sync_syncronize"
175 <!--=========================================================================-->
176 <div class="doc_subsection">
177 <a name="codegen">Code Generator Improvements</a>
180 <div class="doc_text">
182 <p>We put a significant amount of work into the code generator infrastructure,
183 which allows us to implement more aggressive algorithms and make it run
187 <li>MemOperand in the code generator: describe me!.</li>
188 <li>i128 support and APInt through most of codegen.</li>
193 <!--=========================================================================-->
194 <div class="doc_subsection">
195 <a name="optimizer">Optimizer Improvements</a>
198 <div class="doc_text">
200 <p>In addition to a huge array of bug fixes and minor performance tweaks, the
201 LLVM 2.3 optimizers support a few major enhancements:</p>
205 <li>Loop index set splitting on by default: describe me.</li>
206 <li>LLVM includes a new memcpy optimization pass which optimizes out dead
207 memcpy calls and unneeded copies of aggregates.</li>
213 <!--=========================================================================-->
214 <div class="doc_subsection">
215 <a name="targetspecific">Target Specific Improvements</a>
218 <div class="doc_text">
219 <p>New target-specific features include:
223 <li>llvm-gcc's X86-64 ABI conformance is far improved, particularly in the
224 area of passing and returning structures by value. llvm-gcc Compiled code
225 now interoperates very well on X86-64 systems with other compilers.</li>
227 <li>The LLVM X86 backend now supports the support SSE 4.1 instruction set, and
228 the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins.</li>
230 <li>The X86 backend now does a number of optimizations that aim to avoid
231 converting numbers back and forth from SSE registers to the X87 floating
234 <li>The X86 backend supports stack realignment, which is particularly useful for
235 vector code on OS's without 16-byte aligned stacks.</li>
237 <li>The X86 backend now supports the "sseregparm" options in GCC, which allow
238 functions to be tagged as passing floating point values in SSE
241 <li>Trampolines (taking the address of a nested function) now work on
249 <!--=========================================================================-->
250 <div class="doc_subsection">
251 <a name="otherimprovements">Other Improvements</a>
254 <div class="doc_text">
255 <p>New features include:
259 <li>LLVM now builds with GCC 4.3.</li>
264 <!-- *********************************************************************** -->
265 <div class="doc_section">
266 <a name="portability">Portability and Supported Platforms</a>
268 <!-- *********************************************************************** -->
270 <div class="doc_text">
272 <p>LLVM is known to work on the following platforms:</p>
275 <li>Intel and AMD machines running Red Hat Linux, Fedora Core and FreeBSD
276 (and probably other unix-like systems).</li>
277 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and
279 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
280 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
281 support is available for native builds with Visual C++).</li>
282 <li>Sun UltraSPARC workstations running Solaris 8.</li>
283 <li>Alpha-based machines running Debian GNU/Linux.</li>
284 <li>Itanium-based machines running Linux and HP-UX.</li>
287 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
288 to the machine and operating system on which it is built. However, minor
289 porting may be required to get LLVM to work on new platforms. We welcome your
290 portability patches and reports of successful builds or error messages.</p>
294 <!-- *********************************************************************** -->
295 <div class="doc_section">
296 <a name="knownproblems">Known Problems</a>
298 <!-- *********************************************************************** -->
300 <div class="doc_text">
302 <p>This section contains all known problems with the LLVM system, listed by
303 component. As new problems are discovered, they will be added to these
304 sections. If you run into a problem, please check the <a
305 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
306 there isn't already one.</p>
310 <!-- ======================================================================= -->
311 <div class="doc_subsection">
312 <a name="experimental">Experimental features included with this release</a>
315 <div class="doc_text">
317 <p>The following components of this LLVM release are either untested, known to
318 be broken or unreliable, or are in early development. These components should
319 not be relied on, and bugs should not be filed against them, but they may be
320 useful to some people. In particular, if you would like to work on one of these
321 components, please contact us on the <a
322 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
325 <li>The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.</li>
326 <li>The LLC "<tt>-filetype=asm</tt>" (the default) is the only supported
327 value for this option.</li>
332 <!-- ======================================================================= -->
333 <div class="doc_subsection">
334 <a name="x86-be">Known problems with the X86 back-end</a>
337 <div class="doc_text">
340 <li>The X86 backend does not yet support <a href="http://llvm.org/PR879">inline
341 assembly that uses the X86 floating point stack</a>.</li>
342 <li>The X86 backend generates inefficient floating point code when configured to
343 generate code for systems that don't have SSE2.</li>
348 <!-- ======================================================================= -->
349 <div class="doc_subsection">
350 <a name="ppc-be">Known problems with the PowerPC back-end</a>
353 <div class="doc_text">
356 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
357 compilation, and lacks support for debug information.</li>
362 <!-- ======================================================================= -->
363 <div class="doc_subsection">
364 <a name="arm-be">Known problems with the ARM back-end</a>
367 <div class="doc_text">
370 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
371 processors, thumb programs can crash or produce wrong
372 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
373 <li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
375 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly execute
376 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
381 <!-- ======================================================================= -->
382 <div class="doc_subsection">
383 <a name="sparc-be">Known problems with the SPARC back-end</a>
386 <div class="doc_text">
389 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
390 support the 64-bit SPARC ABI (-m64).</li>
395 <!-- ======================================================================= -->
396 <div class="doc_subsection">
397 <a name="alpha-be">Known problems with the Alpha back-end</a>
400 <div class="doc_text">
404 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
405 appropriate nops inserted to ensure restartability.</li>
410 <!-- ======================================================================= -->
411 <div class="doc_subsection">
412 <a name="ia64-be">Known problems with the IA64 back-end</a>
415 <div class="doc_text">
419 <li>C++ programs are likely to fail on IA64, as calls to <tt>setjmp</tt> are
420 made where the argument is not 16-byte aligned, as required on IA64. (Strictly
421 speaking this is not a bug in the IA64 back-end; it will also be encountered
422 when building C++ programs using the C back-end.)</li>
424 <li>The C++ front-end does not use <a href="http://llvm.org/PR406">IA64
425 ABI compliant layout of v-tables</a>. In particular, it just stores function
426 pointers instead of function descriptors in the vtable. This bug prevents
427 mixing C++ code compiled with LLVM with C++ objects compiled by other C++
430 <li>There are a few ABI violations which will lead to problems when mixing LLVM
431 output with code built with other compilers, particularly for floating-point
434 <li>Defining vararg functions is not supported (but calling them is ok).</li>
436 <li>The Itanium backend has bitrotted somewhat.</li>
441 <!-- ======================================================================= -->
442 <div class="doc_subsection">
443 <a name="c-be">Known problems with the C back-end</a>
446 <div class="doc_text">
449 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
450 inline assembly code</a>.</li>
451 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
452 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
453 C++ code compiled with LLC or native compilers.</li>
454 <li>The C backend does not support all exception handling constructs.</li>
460 <!-- ======================================================================= -->
461 <div class="doc_subsection">
462 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
465 <!-- _______________________________________________________________________ -->
466 <div class="doc_subsubsection">Bugs</div>
468 <div class="doc_text">
470 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
471 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
472 llvmdev mailing list if you are interested.</p>
474 <p>The only major language feature of GCC not supported by llvm-gcc is
475 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
476 are only supported on some targets. For example, trampolines are only
477 supported on some targets, which are used when you take the address of a
480 <p>If you run into GCC extensions which are not supported, please let us know.
485 <!-- ======================================================================= -->
486 <div class="doc_subsection">
487 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
490 <div class="doc_text">
492 <p>The C++ front-end is considered to be fully
493 tested and works for a number of non-trivial programs, including LLVM
494 itself, Qt, Mozilla, etc.</p>
497 <li>Exception handling works well on the X86 and PowerPC targets, including
498 x86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is
499 supported on x86-64 linux, but that is disabled by default in this release.</li>
505 <!-- ======================================================================= -->
506 <div class="doc_subsection">
507 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
510 <div class="doc_text">
511 The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
512 technology and problems should be expected.
514 <li>The Ada front-end currently only builds on x86-32. This is mainly due
515 to lack of trampoline support (pointers to nested functions) on other platforms,
516 however it <a href="http://llvm.org/PR2006">also fails to build on x86-64</a>
517 which does support trampolines.</li>
518 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
519 Workaround: configure with --disable-bootstrap.</li>
520 <li>The c380004 and <a href="http://llvm.org/PR2010">c393010</a> ACATS tests
521 fail (c380004 also fails with gcc-4.2 mainline).</li>
522 <li>Many gcc specific Ada tests continue to crash the compiler.</li>
523 <li>The -E binder option (exception backtraces)
524 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
525 crashing if an exception is raised. Workaround: do not use -E.</li>
526 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
527 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
528 or use representation clauses that result in a field of a non-discrete type
529 starting or finishing in the middle of a byte.</li>
530 <li>The lli interpreter <a href="http://llvm.org/PR2009">considers 'main'
531 as generated by the Ada binder to be invalid</a>.
532 Workaround: hand edit the file to use pointers for argv and envp rather than
534 <li>The -fstack-check option <a href="http://llvm.org/PR2008">is ignored</a>.</li>
538 <!-- ======================================================================= -->
539 <div class="doc_subsection">
540 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
543 <div class="doc_text">
546 <li>The llvm-gcc 4.2 gfortran front-end supports a broad range of Fortran code, but does
547 <a href="http://llvm.org/PR1971">not support EQUIVALENCE yet</a>.</li>
553 <!-- *********************************************************************** -->
554 <div class="doc_section">
555 <a name="additionalinfo">Additional Information</a>
557 <!-- *********************************************************************** -->
559 <div class="doc_text">
561 <p>A wide variety of additional information is available on the <a
562 href="http://llvm.org">LLVM web page</a>, in particular in the <a
563 href="http://llvm.org/docs/">documentation</a> section. The web page also
564 contains versions of the API documentation which is up-to-date with the
565 Subversion version of the source code.
566 You can access versions of these documents specific to this release by going
567 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
569 <p>If you have any questions or comments about LLVM, please feel free to contact
570 us via the <a href="http://llvm.org/docs/#maillist"> mailing
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