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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>
174 <li>Ahead of Time compiler: compiles .class files to llvm .bc. VMKit uses this
175 functionality to native compile the standard classes (eg java.lang.String).
176 Users can compile AOT .class files into dynamic libraries and run them with the
179 <li>New exception model: the dwarf exception model is very slow for
180 exception-intensive applications, so the JVM has had a new implementation of
181 exceptions which check at each function call if an exception happened. There is
182 a low performance penalty on applications without exceptions, but it is a big
183 gain for exception-intensive applications. For example the jack benchmark in
184 Spec JVM98 is 6x faster (performance gain of 83%).</li>
186 <li>New support for OSX/X64, Linux/X64 (with the Boehm GC), Linux/ppc32.</li>
192 <!-- *********************************************************************** -->
193 <div class="doc_section">
194 <a name="whatsnew">What's New in LLVM?</a>
196 <!-- *********************************************************************** -->
198 <div class="doc_text">
200 <p>This release includes a huge number of bug fixes, performance tweaks, and
201 minor improvements. Some of the major improvements and new features are listed
206 <!--=========================================================================-->
207 <div class="doc_subsection">
208 <a name="majorfeatures">Major New Features</a>
211 <div class="doc_text">
213 <p>LLVM 2.5 includes several major new capabilities:</p>
216 <li><p>The code generator now supports arbitrary precision integers.
217 Types like <tt>i33</tt> have long been valid in the LLVM IR, but previously
218 could only be used with the interpreter.
219 Now IR using such types can be compiled to native code on all targets.
220 All operations are supported if the integer is not bigger than twice the
221 target machine word size.
222 Simple operations like loads, stores and shifts by a constant amount are
223 supported for integers of any size.
229 Pure project: http://code.google.com/p/pure-lang/
235 .ll parser rewrite, caret diags, better errors, less fragile (less likely to
236 crash on strange things). No longer depends on flex/bison.
237 GCC inliner off, llvm handles always-inline.
239 x86 backend GS segment -> addr space 256 (r62980)
241 memdep (used by GVN and memcpyopt) is faster / more aggressive.
242 how to write a backend doc docs/WritingAnLLVMBackend.html
243 fastisel + exception handling
244 vector widening <3 x float> -> <4 x float>
245 arm port improvements? arm jit encoding stuff, constant island support?
246 JIT TLS support on x86-32.
247 mem2reg now faster on code with huge basic blocks
248 stack protectors/stack canaries, -fstack-protector, controllable on a
249 per-function basis with attributes.
250 shufflevector is generalized to allow different shuffle mask width than its
252 loop optimizer improves floating point induction variables
253 llvm/Analysis/DebugInfo.h classes, llvm-gcc and clang and codegen use them.
254 DebugInfoBuilder gone.
255 asmprinters seperate from targets for jits
256 PBQP register allocator now supports register coalescing.
257 JIT supports exceptions on linux/x86-64.
258 integer overflow intrinsics for [us](add/sub/mul). Supported on all targets,
259 but only generates efficient code on x86.
260 X86 backend now supports -disable-mmx.
261 noalias attribute on return value indicates that function returns new memory
263 postalloc scheduler: anti dependence breaking, hazard recognizer?
264 llvmc2 renamed to llvmc
265 Jump threading more powerful: it is iterative, handles threading based on values
266 with fully redundant and partially redundant loads.
268 ARM debug info support?
269 unit test framework based on Google Test.
271 vector shift support + X86 backend.
272 x86 JIT now detects core i7 and atom, autoconfiguring itself appropriately.
273 SROA is more aggressive about promoting unions.
274 non-zero __builtin_return_address values on X86.
275 x86-64 now uses red zone (unless -mno-red-zone option is specified).
278 llvm-gcc defaults to -fno-math-errno on all x86 targets.
280 initial support for debug line numbers when optimization enabled, not useful in
281 2.5 but will be for 2.6.
289 <!--=========================================================================-->
290 <div class="doc_subsection">
291 <a name="llvm-gcc">llvm-gcc 4.2 Improvements</a>
294 <div class="doc_text">
296 <p>LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC
297 front-ends and driver with the LLVM optimizer and code generator. It currently
298 includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.</p>
307 <!--=========================================================================-->
308 <div class="doc_subsection">
309 <a name="coreimprovements">LLVM Core Improvements</a>
312 <div class="doc_text">
313 <p>New features include:</p>
322 <!--=========================================================================-->
323 <div class="doc_subsection">
324 <a name="optimizer">Optimizer Improvements</a>
327 <div class="doc_text">
329 <p>In addition to a huge array of bug fixes and minor performance tweaks, this
330 release includes a few major enhancements and additions to the optimizers:</p>
340 <!--=========================================================================-->
341 <div class="doc_subsection">
342 <a name="codegen">Code Generator Improvements</a>
345 <div class="doc_text">
347 <p>We have put a significant amount of work into the code generator infrastructure,
348 which allows us to implement more aggressive algorithms and make it run
352 <li>The type legalization logic has been completely rewritten, and is now
353 more powerful (it supports arbitrary precision integer types for example)
354 and hopefully more correct.
355 The type legalizer converts operations on types that are not natively
356 supported by the target machine into equivalent code sequences that only use
357 natively supported types.
358 The old type legalizer is still available and will be used if
359 <tt>-disable-legalize-types</tt> is passed to <tt>llc</tt>.
368 <!--=========================================================================-->
369 <div class="doc_subsection">
370 <a name="targetspecific">Target Specific Improvements</a>
373 <div class="doc_text">
374 <p>New target-specific features include:
384 <!--=========================================================================-->
385 <div class="doc_subsection">
386 <a name="otherimprovements">Other Improvements</a>
389 <div class="doc_text">
390 <p>New features include:
400 <!--=========================================================================-->
401 <div class="doc_subsection">
402 <a name="changes">Major Changes and Removed Features</a>
405 <div class="doc_text">
407 <p>If you're already an LLVM user or developer with out-of-tree changes based
408 on LLVM 2.4, this section lists some "gotchas" that you may run into upgrading
409 from the previous release.</p>
417 <p>In addition, many APIs have changed in this release. Some of the major LLVM
431 <!-- *********************************************************************** -->
432 <div class="doc_section">
433 <a name="portability">Portability and Supported Platforms</a>
435 <!-- *********************************************************************** -->
437 <div class="doc_text">
439 <p>LLVM is known to work on the following platforms:</p>
442 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
443 Linux, Fedora Core and FreeBSD (and probably other unix-like systems).</li>
444 <li>PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit
445 and 64-bit modes.</li>
446 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
447 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
448 support is available for native builds with Visual C++).</li>
449 <li>Sun UltraSPARC workstations running Solaris 10.</li>
450 <li>Alpha-based machines running Debian GNU/Linux.</li>
451 <li>Itanium-based (IA64) machines running Linux and HP-UX.</li>
454 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
455 to the machine and operating system on which it is built. However, minor
456 porting may be required to get LLVM to work on new platforms. We welcome your
457 portability patches and reports of successful builds or error messages.</p>
461 <!-- *********************************************************************** -->
462 <div class="doc_section">
463 <a name="knownproblems">Known Problems</a>
465 <!-- *********************************************************************** -->
467 <div class="doc_text">
469 <p>This section contains significant known problems with the LLVM system,
470 listed by component. If you run into a problem, please check the <a
471 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
472 there isn't already one.</p>
476 <!-- ======================================================================= -->
477 <div class="doc_subsection">
478 <a name="experimental">Experimental features included with this release</a>
481 <div class="doc_text">
483 <p>The following components of this LLVM release are either untested, known to
484 be broken or unreliable, or are in early development. These components should
485 not be relied on, and bugs should not be filed against them, but they may be
486 useful to some people. In particular, if you would like to work on one of these
487 components, please contact us on the <a
488 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
491 <li>The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 backends are experimental.</li>
492 <li>The llc "<tt>-filetype=asm</tt>" (the default) is the only supported
493 value for this option.</li>
498 <!-- ======================================================================= -->
499 <div class="doc_subsection">
500 <a name="x86-be">Known problems with the X86 back-end</a>
503 <div class="doc_text">
506 <li>The X86 backend does not yet support
507 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
508 floating point stack</a>. It supports the 'f' and 't' constraints, but not
510 <li>The X86 backend generates inefficient floating point code when configured
511 to generate code for systems that don't have SSE2.</li>
512 <li>Win64 code generation wasn't widely tested. Everything should work, but we
513 expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
515 to <a href="http://llvm.org/PR2255">several</a>
516 <a href="http://llvm.org/PR2257">bugs</a> due to lack of support for the
517 'u' inline assembly constraint and X87 floating point inline assembly.</li>
518 <li>The X86-64 backend does not yet support the LLVM IR instruction
519 <tt>va_arg</tt>. Currently, the llvm-gcc front-end supports variadic
520 argument constructs on X86-64 by lowering them manually.</li>
525 <!-- ======================================================================= -->
526 <div class="doc_subsection">
527 <a name="ppc-be">Known problems with the PowerPC back-end</a>
530 <div class="doc_text">
533 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
534 compilation, and lacks support for debug information.</li>
539 <!-- ======================================================================= -->
540 <div class="doc_subsection">
541 <a name="arm-be">Known problems with the ARM back-end</a>
544 <div class="doc_text">
547 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
548 processors, thumb programs can crash or produce wrong
549 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
550 <li>Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested.
552 <li>There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly
554 programs compiled with LLVM. Please use more recent versions of QEMU.</li>
559 <!-- ======================================================================= -->
560 <div class="doc_subsection">
561 <a name="sparc-be">Known problems with the SPARC back-end</a>
564 <div class="doc_text">
567 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
568 support the 64-bit SPARC ABI (-m64).</li>
573 <!-- ======================================================================= -->
574 <div class="doc_subsection">
575 <a name="mips-be">Known problems with the MIPS back-end</a>
578 <div class="doc_text">
581 <li>The O32 ABI is not fully supported.</li>
582 <li>64-bit MIPS targets are not supported yet.</li>
587 <!-- ======================================================================= -->
588 <div class="doc_subsection">
589 <a name="alpha-be">Known problems with the Alpha back-end</a>
592 <div class="doc_text">
596 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
597 appropriate nops inserted to ensure restartability.</li>
602 <!-- ======================================================================= -->
603 <div class="doc_subsection">
604 <a name="ia64-be">Known problems with the IA64 back-end</a>
607 <div class="doc_text">
610 <li>The Itanium backend is highly experimental, and has a number of known
611 issues. We are looking for a maintainer for the Itanium backend. If you
612 are interested, please contact the LLVMdev mailing list.</li>
617 <!-- ======================================================================= -->
618 <div class="doc_subsection">
619 <a name="c-be">Known problems with the C back-end</a>
622 <div class="doc_text">
625 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
626 inline assembly code</a>.</li>
627 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
628 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
629 C++ code compiled with llc or native compilers.</li>
630 <li>The C backend does not support all exception handling constructs.</li>
631 <li>The C backend does not support arbitrary precision integers.</li>
637 <!-- ======================================================================= -->
638 <div class="doc_subsection">
639 <a name="c-fe">Known problems with the llvm-gcc C front-end</a>
642 <div class="doc_text">
644 <p>llvm-gcc does not currently support <a href="http://llvm.org/PR869">Link-Time
645 Optimization</a> on most platforms "out-of-the-box". Please inquire on the
646 LLVMdev mailing list if you are interested.</p>
648 <p>The only major language feature of GCC not supported by llvm-gcc is
649 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
650 are only supported on some targets. For example, trampolines are only
651 supported on some targets (these are used when you take the address of a
652 nested function).</p>
654 <p>If you run into GCC extensions which are not supported, please let us know.
659 <!-- ======================================================================= -->
660 <div class="doc_subsection">
661 <a name="c++-fe">Known problems with the llvm-gcc C++ front-end</a>
664 <div class="doc_text">
666 <p>The C++ front-end is considered to be fully
667 tested and works for a number of non-trivial programs, including LLVM
668 itself, Qt, Mozilla, etc.</p>
671 <li>Exception handling works well on the X86 and PowerPC targets. Currently
672 only Linux and Darwin targets are supported (both 32 and 64 bit).</li>
677 <!-- ======================================================================= -->
678 <div class="doc_subsection">
679 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
682 <div class="doc_text">
684 <li>Fortran support generally works, but there are still several unresolved bugs
685 in Bugzilla. Please see the tools/gfortran component for details.</li>
687 <li>The Fortran front-end currently does not build on Darwin (without tweaks)
688 due to unresolved dependencies on the C front-end.</li>
692 <!-- ======================================================================= -->
693 <div class="doc_subsection">
694 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
697 <div class="doc_text">
698 The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
699 technology and problems should be expected.
701 <li>The Ada front-end currently only builds on X86-32. This is mainly due
702 to lack of trampoline support (pointers to nested functions) on other platforms,
703 however it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
704 which does support trampolines.</li>
705 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
706 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
707 exception handling, which is used internally by the compiler.
708 Workaround: configure with --disable-bootstrap.</li>
709 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
710 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
711 (c380004 also fails with gcc-4.2 mainline).
712 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
713 causes the compiler to go into an infinite loop, using up all system memory.</li>
714 <li>Some gcc specific Ada tests continue to crash the compiler.</li>
715 <li>The -E binder option (exception backtraces)
716 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
717 crashing if an exception is raised. Workaround: do not use -E.</li>
718 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
719 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
720 or use representation clauses that result in a field of a non-discrete type
721 starting or finishing in the middle of a byte.</li>
722 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
723 'main' as generated by the Ada binder to be invalid</a>.
724 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
725 <tt>envp</tt> rather than integers.</li>
726 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
731 <!-- *********************************************************************** -->
732 <div class="doc_section">
733 <a name="additionalinfo">Additional Information</a>
735 <!-- *********************************************************************** -->
737 <div class="doc_text">
739 <p>A wide variety of additional information is available on the <a
740 href="http://llvm.org">LLVM web page</a>, in particular in the <a
741 href="http://llvm.org/docs/">documentation</a> section. The web page also
742 contains versions of the API documentation which is up-to-date with the
743 Subversion version of the source code.
744 You can access versions of these documents specific to this release by going
745 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
747 <p>If you have any questions or comments about LLVM, please feel free to contact
748 us via the <a href="http://llvm.org/docs/#maillist"> mailing
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