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7 <title>LLVM 2.5 Release Notes</title>
11 <div class="doc_title">LLVM 2.5 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="#whatsnew">What's New in LLVM?</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></li>
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 <!-- *********************************************************************** -->
28 <div class="doc_section">
29 <a name="intro">Introduction</a>
31 <!-- *********************************************************************** -->
33 <div class="doc_text">
35 <p>This document contains the release notes for the LLVM Compiler
36 Infrastructure, release 2.5. Here we describe the status of LLVM, including
37 major improvements from the previous release and significant known problems.
38 All LLVM releases may be downloaded from the <a
39 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
41 <p>For more information about LLVM, including information about the latest
42 release, please check out the <a href="http://llvm.org/">main LLVM
43 web site</a>. If you have questions or comments, the <a
44 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's Mailing
45 List</a> is a good place to send them.</p>
47 <p>Note that if you are reading this file from a Subversion checkout or the
48 main LLVM web page, this document applies to the <i>next</i> release, not the
49 current one. To see the release notes for a specific release, please see the
50 <a href="http://llvm.org/releases/">releases page</a>.</p>
54 <!-- Unfinished features in 2.5:
57 target-specific intrinsics
59 pre-alloc splitter, strong phi elim
60 llc -enable-value-prop, propagation of value info (sign/zero ext info) from
62 debug info for optimized code
66 <!-- for announcement email:
69 <!-- *********************************************************************** -->
70 <div class="doc_section">
71 <a name="subproj">Sub-project Status Update</a>
73 <!-- *********************************************************************** -->
75 <div class="doc_text">
77 The LLVM 2.5 distribution currently consists of code from the core LLVM
78 repository (which roughly includes the LLVM optimizers, code generators and
79 supporting tools) and the llvm-gcc repository. In addition to this code, the
80 LLVM Project includes other sub-projects that are in development. The two which
81 are the most actively developed are the <a href="#clang">Clang Project</a> and
82 the <a href="#vmkit">VMKit Project</a>.
88 <!--=========================================================================-->
89 <div class="doc_subsection">
90 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
93 <div class="doc_text">
95 <p>The <a href="http://clang.llvm.org/">Clang project</a> is an effort to build
96 a set of new 'LLVM native' front-end technologies for the LLVM optimizer
97 and code generator. While Clang is not included in the LLVM 2.5 release, it
98 is continuing to make major strides forward in all areas. Its C and Objective-C
99 parsing and code generation support is now very solid. For example, it is
100 capable of successfully building many real applications for X86-32 and X86-64,
101 including the FreeBSD kernel. C++ is also making <a
102 href="http://clang.llvm.org/cxx_status.html">incredible progress</a>, and work
103 on templates has recently started.</p>
105 <p>While Clang is not yet production quality, it is progressing very nicely and
106 is quite usable for building many C and Objective-C applications. If you are
107 interested in fast compiles and good diagnostics, we encourage you to try it out
108 by <a href="http://clang.llvm.org/get_started.html">building from mainline</a>
109 and reporting any issues you hit to the <a
110 href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">Clang front-end mailing
113 <p>In the LLVM 2.5 time-frame, the Clang team has made many improvements:</p>
116 <li>Clang now has a new driver, which is focused on providing a GCC-compatible
118 <li>The X86-64 ABI is now supported.</li>
119 <li>Precompiled header support is now implemented.</li>
120 <li>Objective-C support is significantly improved beyond LLVM 2.4, supporting
121 many features, such as Objective-C Garbage Collection.</li>
122 <li>Many many bugs are fixed.</li>
125 <!--=========================================================================-->
126 <div class="doc_subsection">
127 <a name="clangsa">Clang Static Analyzer</a>
130 <div class="doc_text">
132 <p>The Clang project also includes an early stage static source code analysis
133 tool for <a href="http://clang.llvm.org/StaticAnalysis.html">automatically
134 finding bugs</a> in C and Objective-C programs. The tool performs a growing set
135 of checks to find bugs that occur on a specific path within a program. Examples
136 of bugs the tool finds include logic errors such as null dereferences,
137 violations of various API rules, dead code, and potential memory leaks in
138 Objective-C programs. Since its inception, public feedback on the tool has been
139 extremely positive, and conservative estimates put the number of real bugs it
140 has found in industrial-quality software on the order of thousands.</p>
142 <p>The tool also provides a simple web GUI to inspect potential bugs found by
143 the tool. While still early in development, the GUI illustrates some of the key
144 features of Clang: accurate source location information, which is used by the
145 GUI to highlight specific code expressions that relate to a bug (including those
146 that span multiple lines); and built-in knowledge of macros, which is used to
147 perform inline expansion of macros within the GUI itself.</p>
149 <p>The set of checks performed by the static analyzer is gradually expanding,
150 and future plans for the tool include full source-level inter-procedural
151 analysis and deeper checks such as buffer overrun detection. There are many
152 opportunities to extend and enhance the static analyzer, and anyone interested
153 in working on this project is encouraged to get involved!</p>
157 <!--=========================================================================-->
158 <div class="doc_subsection">
159 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
162 <div class="doc_text">
164 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
165 a JVM and a CLI Virtual Machines (Microsoft .NET is an
166 implementation of the CLI) using the Just-In-Time compiler of LLVM.</p>
168 <p>Following LLVM 2.5, VMKit has its first release ? that you can find on its
169 <a href="http://vmkit.llvm.org/releases/">webpage</a>. The release includes
170 bug fixes, cleanup and new features. The major changes are:</p>
180 <!-- *********************************************************************** -->
181 <div class="doc_section">
182 <a name="whatsnew">What's New in LLVM?</a>
184 <!-- *********************************************************************** -->
186 <div class="doc_text">
188 <p>This release includes a huge number of bug fixes, performance tweaks, and
189 minor improvements. Some of the major improvements and new features are listed
194 <!--=========================================================================-->
195 <div class="doc_subsection">
196 <a name="majorfeatures">Major New Features</a>
199 <div class="doc_text">
201 <p>LLVM 2.5 includes several major new capabilities:</p>
204 <li><p> Legalize Types</p></li>
215 x86 backend FS/GS segment address spaces?
217 memdep is faster / more aggressive.
218 how to write a backend doc docs/WritingAnLLVMBackend.html
219 fastisel + exception handling
220 vector widening <3 x float> -> <4 x float>
221 arm port improvements? arm jit encoding stuff, constant island support?
222 JIT TLS support on x86
223 mem2reg now faster on code with huge basic blocks
224 stack protectors/stack canaries, -fstack-protector, controllable on a
225 per-function basis with attributes.
226 shufflevector is generalized to allow different shuffle mask width than its
228 loop optimizer improves floating point induction variables
229 llvm/Analysis/DebugInfo.h classes, llvm-gcc and clang and codegen use them.
230 asmprinters seperate from targets for jits
238 <!--=========================================================================-->
239 <div class="doc_subsection">
240 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
243 <div class="doc_text">
245 <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
246 front-ends and driver with the LLVM optimizer and code generator. It currently
247 includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
256 <!--=========================================================================-->
257 <div class="doc_subsection">
258 <a name="coreimprovements">LLVM Core Improvements</a>
261 <div class="doc_text">
262 <p>New features include:</p>
271 <!--=========================================================================-->
272 <div class="doc_subsection">
273 <a name="optimizer">Optimizer Improvements</a>
276 <div class="doc_text">
278 <p>In addition to a huge array of bug fixes and minor performance tweaks, this
279 release includes a few major enhancements and additions to the optimizers:</p>
289 <!--=========================================================================-->
290 <div class="doc_subsection">
291 <a name="codegen">Code Generator Improvements</a>
294 <div class="doc_text">
296 <p>We have put a significant amount of work into the code generator infrastructure,
297 which allows us to implement more aggressive algorithms and make it run
308 <!--=========================================================================-->
309 <div class="doc_subsection">
310 <a name="targetspecific">Target Specific Improvements</a>
313 <div class="doc_text">
314 <p>New target-specific features include:
324 <!--=========================================================================-->
325 <div class="doc_subsection">
326 <a name="otherimprovements">Other Improvements</a>
329 <div class="doc_text">
330 <p>New features include:
340 <!--=========================================================================-->
341 <div class="doc_subsection">
342 <a name="changes">Major Changes and Removed Features</a>
345 <div class="doc_text">
347 <p>If you're already an LLVM user or developer with out-of-tree changes based
348 on LLVM 2.4, this section lists some "gotchas" that you may run into upgrading
349 from the previous release.</p>
357 <p>In addition, many APIs have changed in this release. Some of the major LLVM
371 <!-- *********************************************************************** -->
372 <div class="doc_section">
373 <a name="portability">Portability and Supported Platforms</a>
375 <!-- *********************************************************************** -->
377 <div class="doc_text">
379 <p>LLVM is known to work on the following platforms:</p>
382 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
383 Linux, Fedora Core and FreeBSD (and probably other unix-like systems).</li>
384 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
385 and 64-bit modes.</li>
386 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
387 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
388 support is available for native builds with Visual C++).</li>
389 <li>Sun UltraSPARC workstations running Solaris 10.</li>
390 <li>Alpha-based machines running Debian GNU/Linux.</li>
391 <li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
394 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
395 to the machine and operating system on which it is built. However, minor
396 porting may be required to get LLVM to work on new platforms. We welcome your
397 portability patches and reports of successful builds or error messages.</p>
401 <!-- *********************************************************************** -->
402 <div class="doc_section">
403 <a name="knownproblems">Known Problems</a>
405 <!-- *********************************************************************** -->
407 <div class="doc_text">
409 <p>This section contains significant known problems with the LLVM system,
410 listed by component. If you run into a problem, please check the <a
411 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
412 there isn't already one.</p>
416 <!-- ======================================================================= -->
417 <div class="doc_subsection">
418 <a name="experimental">Experimental features included with this release</a>
421 <div class="doc_text">
423 <p>The following components of this LLVM release are either untested, known to
424 be broken or unreliable, or are in early development. These components should
425 not be relied on, and bugs should not be filed against them, but they may be
426 useful to some people. In particular, if you would like to work on one of these
427 components, please contact us on the <a
428 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
431 <li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
432 <li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
433 value for this option.</li>
438 <!-- ======================================================================= -->
439 <div class="doc_subsection">
440 <a name="x86-be">Known problems with the X86 back-end</a>
443 <div class="doc_text">
446 <li>The X86 backend does not yet support
447 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
448 floating point stack</a>. It supports the 'f' and 't' constraints, but not
450 <li>The X86 backend generates inefficient floating point code when configured
451 to generate code for systems that don't have SSE2.</li>
452 <li>Win64 code generation wasn't widely tested. Everything should work, but we
453 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
455 to <a href="http://llvm.org/PR2255">several</a>
456 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
457 'u' inline assembly constraint and X87 floating point inline assembly.</li>
458 <li>The X86-64 backend does not yet support the LLVM IR instruction
459 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
460 argument constructs on X86-64 by lowering them manually.</li>
465 <!-- ======================================================================= -->
466 <div class="doc_subsection">
467 <a name="ppc-be">Known problems with the PowerPC back-end</a>
470 <div class="doc_text">
473 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
474 compilation, and lacks support for debug information.</li>
479 <!-- ======================================================================= -->
480 <div class="doc_subsection">
481 <a name="arm-be">Known problems with the ARM back-end</a>
484 <div class="doc_text">
487 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
488 processors, thumb programs can crash or produce wrong
489 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
490 <li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
492 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
494 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
499 <!-- ======================================================================= -->
500 <div class="doc_subsection">
501 <a name="sparc-be">Known problems with the SPARC back-end</a>
504 <div class="doc_text">
507 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
508 support the 64-bit SPARC ABI (-m64).</li>
513 <!-- ======================================================================= -->
514 <div class="doc_subsection">
515 <a name="mips-be">Known problems with the MIPS back-end</a>
518 <div class="doc_text">
521 <li>The O32 ABI is not fully supported.</li>
522 <li>64-bit MIPS targets are not supported yet.</li>
527 <!-- ======================================================================= -->
528 <div class="doc_subsection">
529 <a name="alpha-be">Known problems with the Alpha back-end</a>
532 <div class="doc_text">
536 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
537 appropriate nops inserted to ensure restartability.</li>
542 <!-- ======================================================================= -->
543 <div class="doc_subsection">
544 <a name="ia64-be">Known problems with the IA64 back-end</a>
547 <div class="doc_text">
550 <li>The Itanium backend is highly experimental, and has a number of known
551 issues. We are looking for a maintainer for the Itanium backend. If you
552 are interested, please contact the LLVMdev mailing list.</li>
557 <!-- ======================================================================= -->
558 <div class="doc_subsection">
559 <a name="c-be">Known problems with the C back-end</a>
562 <div class="doc_text">
565 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
566 inline assembly code</a>.</li>
567 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
568 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
569 C++ code compiled with llc or native compilers.</li>
570 <li>The C backend does not support all exception handling constructs.</li>
576 <!-- ======================================================================= -->
577 <div class="doc_subsection">
578 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
581 <div class="doc_text">
583 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
584 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
585 LLVMdev mailing list if you are interested.</p>
587 <p>The only major language feature of GCC not supported by llvm-gcc is
588 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
589 are only supported on some targets. For example, trampolines are only
590 supported on some targets (these are used when you take the address of a
591 nested function).</p>
593 <p>If you run into GCC extensions which are not supported, please let us know.
598 <!-- ======================================================================= -->
599 <div class="doc_subsection">
600 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
603 <div class="doc_text">
605 <p>The C++ front-end is considered to be fully
606 tested and works for a number of non-trivial programs, including LLVM
607 itself, Qt, Mozilla, etc.</p>
610 <li>Exception handling works well on the X86 and PowerPC targets. Currently
611 only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
616 <!-- ======================================================================= -->
617 <div class="doc_subsection">
618 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
621 <div class="doc_text">
623 <li>Fortran support generally works, but there are still several unresolved bugs
624 in Bugzilla. Please see the tools/gfortran component for details.</li>
626 <li>The Fortran front-end currently does not build on Darwin (without tweaks)
627 due to unresolved dependencies on the C front-end.</li>
631 <!-- ======================================================================= -->
632 <div class="doc_subsection">
633 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
636 <div class="doc_text">
637 The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
638 technology and problems should be expected.
640 <li>The Ada front-end currently only builds on X86-32. This is mainly due
641 to lack of trampoline support (pointers to nested functions) on other platforms,
642 however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
643 which does support trampolines.</li>
644 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
645 Workaround: configure with --disable-bootstrap.</li>
646 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
647 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
648 (c380004 also fails with gcc-4.2 mainline).</li>
649 <li>Some gcc specific Ada tests continue to crash the compiler.</li>
650 <li>The -E binder option (exception backtraces)
651 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
652 crashing if an exception is raised. Workaround: do not use -E.</li>
653 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
654 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
655 or use representation clauses that result in a field of a non-discrete type
656 starting or finishing in the middle of a byte.</li>
657 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
658 'main' as generated by the Ada binder to be invalid</a>.
659 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
660 <tt>envp</tt> rather than integers.</li>
661 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
666 <!-- *********************************************************************** -->
667 <div class="doc_section">
668 <a name="additionalinfo">Additional Information</a>
670 <!-- *********************************************************************** -->
672 <div class="doc_text">
674 <p>A wide variety of additional information is available on the <a
675 href="http://llvm.org">LLVM web page</a>, in particular in the <a
676 href="http://llvm.org/docs/">documentation</a> section. The web page also
677 contains versions of the API documentation which is up-to-date with the
678 Subversion version of the source code.
679 You can access versions of these documents specific to this release by going
680 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
682 <p>If you have any questions or comments about LLVM, please feel free to contact
683 us via the <a href="http://llvm.org/docs/#maillist"> mailing
688 <!-- *********************************************************************** -->
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