1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
2 "http://www.w3.org/TR/html4/strict.dtd">
5 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
6 <link rel="stylesheet" href="llvm.css" type="text/css">
7 <title>LLVM 2.8 Release Notes</title>
11 <div class="doc_title">LLVM 2.8 Release Notes</div>
13 <img align=right src="http://llvm.org/img/DragonSmall.png"
14 width="136" height="136" alt="LLVM Dragon Logo">
17 <li><a href="#intro">Introduction</a></li>
18 <li><a href="#subproj">Sub-project Status Update</a></li>
19 <li><a href="#externalproj">External Projects Using LLVM 2.8</a></li>
20 <li><a href="#whatsnew">What's New in LLVM 2.8?</a></li>
21 <li><a href="GettingStarted.html">Installation Instructions</a></li>
22 <li><a href="#portability">Portability and Supported Platforms</a></li>
23 <li><a href="#knownproblems">Known Problems</a></li>
24 <li><a href="#additionalinfo">Additional Information</a></li>
27 <div class="doc_author">
28 <p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
31 <h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
34 <a href="http://llvm.org/releases/2.7/docs/ReleaseNotes.html">LLVM 2.7
35 Release Notes</a>.</h1>
37 <!-- *********************************************************************** -->
38 <div class="doc_section">
39 <a name="intro">Introduction</a>
41 <!-- *********************************************************************** -->
43 <div class="doc_text">
45 <p>This document contains the release notes for the LLVM Compiler
46 Infrastructure, release 2.8. Here we describe the status of LLVM, including
47 major improvements from the previous release and significant known problems.
48 All LLVM releases may be downloaded from the <a
49 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
51 <p>For more information about LLVM, including information about the latest
52 release, please check out the <a href="http://llvm.org/">main LLVM
53 web site</a>. If you have questions or comments, the <a
54 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
55 Mailing List</a> is a good place to send them.</p>
57 <p>Note that if you are reading this file from a Subversion checkout or the
58 main LLVM web page, this document applies to the <i>next</i> release, not the
59 current one. To see the release notes for a specific release, please see the
60 <a href="http://llvm.org/releases/">releases page</a>.</p>
67 include/llvm/Analysis/LiveValues.h => Dan
68 lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
69 llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
72 lib/Transforms/Utils/SSI.cpp -> ABCD depends on it.
76 <!-- Features that need text if they're finished for 2.8:
79 llvm.dbg.value: variable debug info for optimized code
80 loop dependence analysis
83 <!-- for announcement email:
85 Many new papers added to /pubs/
88 <!-- *********************************************************************** -->
89 <div class="doc_section">
90 <a name="subproj">Sub-project Status Update</a>
92 <!-- *********************************************************************** -->
94 <div class="doc_text">
96 The LLVM 2.8 distribution currently consists of code from the core LLVM
97 repository (which roughly includes the LLVM optimizers, code generators
98 and supporting tools), the Clang repository and the llvm-gcc repository. In
99 addition to this code, the LLVM Project includes other sub-projects that are in
100 development. Here we include updates on these subprojects.
106 <!--=========================================================================-->
107 <div class="doc_subsection">
108 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
111 <div class="doc_text">
113 <p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
114 C++, and Objective-C languages. Clang aims to provide a better user experience
115 through expressive diagnostics, a high level of conformance to language
116 standards, fast compilation, and low memory use. Like LLVM, Clang provides a
117 modular, library-based architecture that makes it suitable for creating or
118 integrating with other development tools. Clang is considered a
119 production-quality compiler for C and Objective-C on x86 (32- and 64-bit).</p>
121 <p>In the LLVM 2.8 time-frame, the Clang team has made many improvements:</p>
128 <!--=========================================================================-->
129 <div class="doc_subsection">
130 <a name="clangsa">Clang Static Analyzer</a>
133 <div class="doc_text">
135 <p>The <a href="http://clang-analyzer.llvm.org/">Clang Static Analyzer</a>
136 project is an effort to use static source code analysis techniques to
137 automatically find bugs in C and Objective-C programs (and hopefully <a
138 href="http://clang-analyzer.llvm.org/dev_cxx.html">C++ in the
139 future</a>!). The tool is very good at finding bugs that occur on specific
140 paths through code, such as on error conditions.</p>
142 <p>In the LLVM 2.8 time-frame,
147 <!--=========================================================================-->
148 <div class="doc_subsection">
149 <a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
152 <div class="doc_text">
154 The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
155 a JVM and a CLI Virtual Machine (Microsoft .NET is an
156 implementation of the CLI) using LLVM for static and just-in-time
159 <p>With the release of LLVM 2.8, ...</p>
164 <!--=========================================================================-->
165 <div class="doc_subsection">
166 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
169 <div class="doc_text">
171 The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
172 is a simple library that provides an implementation of the low-level
173 target-specific hooks required by code generation and other runtime components.
174 For example, when compiling for a 32-bit target, converting a double to a 64-bit
175 unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
176 function. The compiler-rt library provides highly optimized implementations of
177 this and other low-level routines (some are 3x faster than the equivalent
178 libgcc routines).</p>
181 All of the code in the compiler-rt project is available under the standard LLVM
182 License, a "BSD-style" license. New in LLVM 2.8:
189 <!--=========================================================================-->
190 <div class="doc_subsection">
191 <a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a>
194 <div class="doc_text">
196 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
197 gcc-4.5. Unlike llvm-gcc, which makes many intrusive changes to the underlying
198 gcc-4.2 code, dragonegg in theory does not require any gcc-4.5 modifications
199 whatsoever (currently one small patch is needed). This is thanks to the new
200 <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>, which
201 makes it possible to modify the behaviour of gcc at runtime by loading a plugin,
202 which is nothing more than a dynamic library which conforms to the gcc plugin
203 interface. DragonEgg is a gcc plugin that causes the LLVM optimizers to be run
204 instead of the gcc optimizers, and the LLVM code generators instead of the gcc
205 code generators, just like llvm-gcc. To use it, you add
206 "-fplugin=path/dragonegg.so" to the gcc-4.5 command line, and gcc-4.5 magically
207 becomes llvm-gcc-4.5!
211 DragonEgg is still a work in progress. Currently C works very well, while C++,
212 Ada and Fortran work fairly well. All other languages either don't work at all,
213 or only work poorly. For the moment only the x86-32 and x86-64 targets are
214 supported, and only on linux and darwin (darwin needs an additional gcc patch).
224 <!--=========================================================================-->
225 <div class="doc_subsection">
226 <a name="mc">llvm-mc: Machine Code Toolkit</a>
229 <div class="doc_text">
231 The LLVM Machine Code (aka MC) sub-project of LLVM was created to solve a number
232 of problems in the realm of assembly, disassembly, object file format handling,
233 and a number of other related areas that CPU instruction-set level tools work
234 in. It is a sub-project of LLVM which provides it with a number of advantages
235 over other compilers that do not have tightly integrated assembly-level tools.
236 For a gentle introduction, please see the <a
237 href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
238 LLVM MC Project Blog Post</a>.
241 <p>2.8 status here</p>
245 <!-- *********************************************************************** -->
246 <div class="doc_section">
247 <a name="externalproj">External Open Source Projects Using LLVM 2.8</a>
249 <!-- *********************************************************************** -->
251 <div class="doc_text">
253 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
254 a lot of other language and tools projects. This section lists some of the
255 projects that have already been updated to work with LLVM 2.8.</p>
259 <!-- *********************************************************************** -->
260 <div class="doc_section">
261 <a name="whatsnew">What's New in LLVM 2.8?</a>
263 <!-- *********************************************************************** -->
265 <div class="doc_text">
267 <p>This release includes a huge number of bug fixes, performance tweaks and
268 minor improvements. Some of the major improvements and new features are listed
274 <!--=========================================================================-->
275 <div class="doc_subsection">
276 <a name="orgchanges">LLVM Community Changes</a>
279 <div class="doc_text">
281 <p>In addition to changes to the code, between LLVM 2.7 and 2.8, a number of
282 organization changes have happened:
289 <!--=========================================================================-->
290 <div class="doc_subsection">
291 <a name="majorfeatures">Major New Features</a>
294 <div class="doc_text">
296 <p>LLVM 2.8 includes several major new capabilities:</p>
304 <!--=========================================================================-->
305 <div class="doc_subsection">
306 <a name="coreimprovements">LLVM IR and Core Improvements</a>
309 <div class="doc_text">
310 <p>LLVM IR has several new features for better support of new targets and that
311 expose new optimization opportunities:</p>
315 <li>LLVM 2.8 changes the internal order of operands in <a
316 href="http://llvm.org/doxygen/classllvm_1_1InvokeInst.html"><tt>InvokeInst</tt></a>
317 and <a href="http://llvm.org/doxygen/classllvm_1_1CallInst.html"><tt>CallInst</tt></a>.
318 To be portable across releases, resort to <tt>CallSite</tt> and the
319 high-level accessors, such as <tt>getCalledValue</tt> and <tt>setUnwindDest</tt>.
322 You can no longer pass use_iterators directly to cast<> (and similar), because
323 these routines tend to perform costly dereference operations more than once. You
324 have to dereference the iterators yourself and pass them in.
331 <!--=========================================================================-->
332 <div class="doc_subsection">
333 <a name="optimizer">Optimizer Improvements</a>
336 <div class="doc_text">
338 <p>In addition to a large array of minor performance tweaks and bug fixes, this
339 release includes a few major enhancements and additions to the optimizers:</p>
350 <!--=========================================================================-->
351 <div class="doc_subsection">
352 <a name="executionengine">Interpreter and JIT Improvements</a>
355 <div class="doc_text">
364 <!--=========================================================================-->
365 <div class="doc_subsection">
366 <a name="codegen">Target Independent Code Generator Improvements</a>
369 <div class="doc_text">
371 <p>We have put a significant amount of work into the code generator
372 infrastructure, which allows us to implement more aggressive algorithms and make
376 <li>MachO writer works.</li>
380 <!--=========================================================================-->
381 <div class="doc_subsection">
382 <a name="x86">X86-32 and X86-64 Target Improvements</a>
385 <div class="doc_text">
386 <p>New features of the X86 target include:
390 <li>The X86 backend now supports holding X87 floating point stack values
391 in registers across basic blocks, dramatically improving performance of code
392 that uses long double, and when targetting CPUs that don't support SSE.</li>
398 <!--=========================================================================-->
399 <div class="doc_subsection">
400 <a name="ARM">ARM Target Improvements</a>
403 <div class="doc_text">
404 <p>New features of the ARM target include:
416 <!--=========================================================================-->
417 <div class="doc_subsection">
418 <a name="newapis">New Useful APIs</a>
421 <div class="doc_text">
423 <p>This release includes a number of new APIs that are used internally, which
424 may also be useful for external clients.
434 <!--=========================================================================-->
435 <div class="doc_subsection">
436 <a name="otherimprovements">Other Improvements and New Features</a>
439 <div class="doc_text">
440 <p>Other miscellaneous features include:</p>
449 <!--=========================================================================-->
450 <div class="doc_subsection">
451 <a name="changes">Major Changes and Removed Features</a>
454 <div class="doc_text">
456 <p>If you're already an LLVM user or developer with out-of-tree changes based
457 on LLVM 2.7, this section lists some "gotchas" that you may run into upgrading
458 from the previous release.</p>
465 <p>In addition, many APIs have changed in this release. Some of the major LLVM
475 <!-- *********************************************************************** -->
476 <div class="doc_section">
477 <a name="portability">Portability and Supported Platforms</a>
479 <!-- *********************************************************************** -->
481 <div class="doc_text">
483 <p>LLVM is known to work on the following platforms:</p>
486 <li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
487 Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
489 <li>PowerPC and X86-based Mac OS X systems, running 10.4 and above in 32-bit
490 and 64-bit modes.</li>
491 <li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
492 <li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
493 support is available for native builds with Visual C++).</li>
494 <li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</li>
495 <li>Alpha-based machines running Debian GNU/Linux.</li>
498 <p>The core LLVM infrastructure uses GNU autoconf to adapt itself
499 to the machine and operating system on which it is built. However, minor
500 porting may be required to get LLVM to work on new platforms. We welcome your
501 portability patches and reports of successful builds or error messages.</p>
505 <!-- *********************************************************************** -->
506 <div class="doc_section">
507 <a name="knownproblems">Known Problems</a>
509 <!-- *********************************************************************** -->
511 <div class="doc_text">
513 <p>This section contains significant known problems with the LLVM system,
514 listed by component. If you run into a problem, please check the <a
515 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
516 there isn't already one.</p>
519 <li>LLVM will not correctly compile on Solaris and/or OpenSolaris
520 using the stock GCC 3.x.x series 'out the box',
521 See: <a href="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
522 However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
523 for x86/x86-64 has been made available from the third party AuroraUX Project
524 that has been meticulously tested for bootstrapping LLVM & Clang.</li>
529 <!-- ======================================================================= -->
530 <div class="doc_subsection">
531 <a name="experimental">Experimental features included with this release</a>
534 <div class="doc_text">
536 <p>The following components of this LLVM release are either untested, known to
537 be broken or unreliable, or are in early development. These components should
538 not be relied on, and bugs should not be filed against them, but they may be
539 useful to some people. In particular, if you would like to work on one of these
540 components, please contact us on the <a
541 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
544 <li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430, SystemZ and MicroBlaze
545 backends are experimental.</li>
546 <li><tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
547 supported value for this option. XXX Update me</li>
552 <!-- ======================================================================= -->
553 <div class="doc_subsection">
554 <a name="x86-be">Known problems with the X86 back-end</a>
557 <div class="doc_text">
560 <li>The X86 backend does not yet support
561 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
562 floating point stack</a>. It supports the 'f' and 't' constraints, but not
564 <li>Win64 code generation wasn't widely tested. Everything should work, but we
565 expect small issues to happen. Also, llvm-gcc cannot build the mingw64
566 runtime currently due to lack of support for the 'u' inline assembly
567 constraint and for X87 floating point inline assembly.</li>
568 <li>The X86-64 backend does not yet support the LLVM IR instruction
569 <tt>va_arg</tt>. Currently, front-ends support variadic
570 argument constructs on X86-64 by lowering them manually.</li>
575 <!-- ======================================================================= -->
576 <div class="doc_subsection">
577 <a name="ppc-be">Known problems with the PowerPC back-end</a>
580 <div class="doc_text">
583 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
584 compilation, and lacks support for debug information.</li>
589 <!-- ======================================================================= -->
590 <div class="doc_subsection">
591 <a name="arm-be">Known problems with the ARM back-end</a>
594 <div class="doc_text">
597 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
598 processors, thumb programs can crash or produce wrong
599 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
600 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
606 <!-- ======================================================================= -->
607 <div class="doc_subsection">
608 <a name="sparc-be">Known problems with the SPARC back-end</a>
611 <div class="doc_text">
614 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
615 support the 64-bit SPARC ABI (-m64).</li>
620 <!-- ======================================================================= -->
621 <div class="doc_subsection">
622 <a name="mips-be">Known problems with the MIPS back-end</a>
625 <div class="doc_text">
628 <li>64-bit MIPS targets are not supported yet.</li>
633 <!-- ======================================================================= -->
634 <div class="doc_subsection">
635 <a name="alpha-be">Known problems with the Alpha back-end</a>
638 <div class="doc_text">
642 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
643 appropriate nops inserted to ensure restartability.</li>
648 <!-- ======================================================================= -->
649 <div class="doc_subsection">
650 <a name="c-be">Known problems with the C back-end</a>
653 <div class="doc_text">
656 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
657 inline assembly code</a>.</li>
658 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
659 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
660 C++ code compiled with <tt>llc</tt> or native compilers.</li>
661 <li>The C backend does not support all exception handling constructs.</li>
662 <li>The C backend does not support arbitrary precision integers.</li>
668 <!-- ======================================================================= -->
669 <div class="doc_subsection">
670 <a name="c-fe">Known problems with the llvm-gcc C and C++ front-end</a>
673 <div class="doc_text">
675 <p>The only major language feature of GCC not supported by llvm-gcc is
676 the <tt>__builtin_apply</tt> family of builtins. However, some extensions
677 are only supported on some targets. For example, trampolines are only
678 supported on some targets (these are used when you take the address of a
679 nested function).</p>
683 <!-- ======================================================================= -->
684 <div class="doc_subsection">
685 <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
688 <div class="doc_text">
690 <li>Fortran support generally works, but there are still several unresolved bugs
691 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
692 tools/gfortran component for details.</li>
696 <!-- ======================================================================= -->
697 <div class="doc_subsection">
698 <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
701 <div class="doc_text">
702 The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
703 technology, and problems should be expected.
705 <li>The Ada front-end currently only builds on X86-32. This is mainly due
706 to lack of trampoline support (pointers to nested functions) on other platforms.
707 However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
708 which does support trampolines.</li>
709 <li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
710 This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
711 exception handling, which is used internally by the compiler.
712 Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
713 <li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
714 and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
715 (c380004 also fails with gcc-4.2 mainline).
716 If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
717 causes the compiler to go into an infinite loop, using up all system memory.</li>
718 <li>Some GCC specific Ada tests continue to crash the compiler.</li>
719 <li>The <tt>-E</tt> binder option (exception backtraces)
720 <a href="http://llvm.org/PR1982">does not work</a> and will result in programs
721 crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
722 <li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
723 or finish at a non-byte offset</a> in a record. Workaround: do not pack records
724 or use representation clauses that result in a field of a non-discrete type
725 starting or finishing in the middle of a byte.</li>
726 <li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
727 'main' as generated by the Ada binder to be invalid</a>.
728 Workaround: hand edit the file to use pointers for <tt>argv</tt> and
729 <tt>envp</tt> rather than integers.</li>
730 <li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
735 <!-- *********************************************************************** -->
736 <div class="doc_section">
737 <a name="additionalinfo">Additional Information</a>
739 <!-- *********************************************************************** -->
741 <div class="doc_text">
743 <p>A wide variety of additional information is available on the <a
744 href="http://llvm.org">LLVM web page</a>, in particular in the <a
745 href="http://llvm.org/docs/">documentation</a> section. The web page also
746 contains versions of the API documentation which is up-to-date with the
747 Subversion version of the source code.
748 You can access versions of these documents specific to this release by going
749 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
751 <p>If you have any questions or comments about LLVM, please feel free to contact
752 us via the <a href="http://llvm.org/docs/#maillist"> mailing
757 <!-- *********************************************************************** -->
761 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
762 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
763 <a href="http://validator.w3.org/check/referer"><img
764 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
766 <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
767 Last modified: $Date$