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11 <h1>LLVM 3.2 Release Notes</h1>
14 <img style="float:right" src="http://llvm.org/img/DragonSmall.png"
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19 <li><a href="#intro">Introduction</a></li>
20 <li><a href="#subproj">Sub-project Status Update</a></li>
21 <li><a href="#externalproj">External Projects Using LLVM 3.2</a></li>
22 <li><a href="#whatsnew">What's New in LLVM?</a></li>
23 <li><a href="GettingStarted.html">Installation Instructions</a></li>
24 <li><a href="#knownproblems">Known Problems</a></li>
25 <li><a href="#additionalinfo">Additional Information</a></li>
28 <div class="doc_author">
29 <p>Written by the <a href="http://llvm.org/">LLVM Team</a></p>
32 <h1 style="color:red">These are in-progress notes for the upcoming LLVM 3.2
35 <a href="http://llvm.org/releases/3.1/docs/ReleaseNotes.html">LLVM 3.1
36 Release Notes</a>.</h1>
38 <!-- *********************************************************************** -->
40 <a name="intro">Introduction</a>
42 <!-- *********************************************************************** -->
46 <p>This document contains the release notes for the LLVM Compiler
47 Infrastructure, release 3.2. Here we describe the status of LLVM, including
48 major improvements from the previous release, improvements in various
49 subprojects of LLVM, and some of the current users of the code. All LLVM
50 releases may be downloaded from the <a href="http://llvm.org/releases/">LLVM
51 releases web site</a>.</p>
53 <p>For more information about LLVM, including information about the latest
54 release, please check out the <a href="http://llvm.org/">main LLVM web
55 site</a>. If you have questions or comments,
56 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM
57 Developer's Mailing List</a> is a good place to send them.</p>
59 <p>Note that if you are reading this file from a Subversion checkout or the main
60 LLVM web page, this document applies to the <i>next</i> release, not the
61 current one. To see the release notes for a specific release, please see the
62 <a href="http://llvm.org/releases/">releases page</a>.</p>
67 <!-- *********************************************************************** -->
69 <a name="subproj">Sub-project Status Update</a>
71 <!-- *********************************************************************** -->
75 <p>The LLVM 3.2 distribution currently consists of code from the core LLVM
76 repository, which roughly includes the LLVM optimizers, code generators and
77 supporting tools, and the Clang repository. In addition to this code, the
78 LLVM Project includes other sub-projects that are in development. Here we
79 include updates on these subprojects.</p>
81 <!--=========================================================================-->
83 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
88 <p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
89 C++, and Objective-C languages. Clang aims to provide a better user
90 experience through expressive diagnostics, a high level of conformance to
91 language standards, fast compilation, and low memory use. Like LLVM, Clang
92 provides a modular, library-based architecture that makes it suitable for
93 creating or integrating with other development tools. Clang is considered a
94 production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
95 (32- and 64-bit), and for Darwin/ARM targets.</p>
97 <p>In the LLVM 3.2 time-frame, the Clang team has made many improvements.
98 Highlights include:</p>
103 <p>For more details about the changes to Clang since the 3.1 release, see the
104 <a href="http://clang.llvm.org/docs/ReleaseNotes.html">Clang release
107 <p>If Clang rejects your code but another compiler accepts it, please take a
108 look at the <a href="http://clang.llvm.org/compatibility.html">language
109 compatibility</a> guide to make sure this is not intentional or a known
114 <!--=========================================================================-->
116 <a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
121 <p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
122 <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
123 optimizers and code generators with LLVM's. It works with gcc-4.5 and gcc-4.6
124 (and partially with gcc-4.7), can target the x86-32/x86-64 and ARM processor
125 families, and has been successfully used on the Darwin, FreeBSD, KFreeBSD,
126 Linux and OpenBSD platforms. It fully supports Ada, C, C++ and Fortran. It
127 has partial support for Go, Java, Obj-C and Obj-C++.</p>
129 <p>The 3.2 release has the following notable changes:</p>
137 <!--=========================================================================-->
139 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
144 <p>The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
145 is a simple library that provides an implementation of the low-level
146 target-specific hooks required by code generation and other runtime
147 components. For example, when compiling for a 32-bit target, converting a
148 double to a 64-bit unsigned integer is compiled into a runtime call to the
149 <code>__fixunsdfdi</code> function. The compiler-rt library provides highly
150 optimized implementations of this and other low-level routines (some are 3x
151 faster than the equivalent libgcc routines).</p>
153 <p>The 3.2 release has the following notable changes:</p>
161 <!--=========================================================================-->
163 <a name="lldb">LLDB: Low Level Debugger</a>
168 <p><a href="http://lldb.llvm.org">LLDB</a> is a ground-up implementation of a
169 command line debugger, as well as a debugger API that can be used from other
170 applications. LLDB makes use of the Clang parser to provide high-fidelity
171 expression parsing (particularly for C++) and uses the LLVM JIT for target
174 <p>The 3.2 release has the following notable changes:</p>
182 <!--=========================================================================-->
184 <a name="libc++">libc++: C++ Standard Library</a>
189 <p>Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
190 licensed</a> under the MIT and UIUC license, allowing it to be used more
193 <p>Within the LLVM 3.2 time-frame there were the following highlights:</p>
201 <!--=========================================================================-->
203 <a name="vmkit">VMKit</a>
208 <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
209 of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
210 just-in-time compilation.</p>
212 <p>The 3.2 release has the following notable changes:</p>
221 <!--=========================================================================-->
223 <a name="Polly">Polly: Polyhedral Optimizer</a>
228 <p><a href="http://polly.llvm.org/">Polly</a> is an <em>experimental</em>
229 optimizer for data locality and parallelism. It currently provides high-level
230 loop optimizations and automatic parallelisation (using the OpenMP run time).
231 Work in the area of automatic SIMD and accelerator code generation was
234 <p>Within the LLVM 3.2 time-frame there were the following highlights:</p>
244 <!-- *********************************************************************** -->
246 <a name="externalproj">External Open Source Projects Using LLVM 3.2</a>
248 <!-- *********************************************************************** -->
252 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
253 a lot of other language and tools projects. This section lists some of the
254 projects that have already been updated to work with LLVM 3.2.</p>
260 <p><a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide
261 the ease of development of a scripting language with the performance of a
262 compiled language. The language derives concepts from C++, Java and Python,
263 incorporating object-oriented programming, operator overloading and strong
272 <p><a href="http://faust.grame.fr/">FAUST</a> is a compiled language for
273 real-time audio signal processing. The name FAUST stands for Functional
274 AUdio STream. Its programming model combines two approaches: functional
275 programming and block diagram composition. In addition with the C, C++, Java,
276 JavaScript output formats, the Faust compiler can generate LLVM bitcode, and
277 works with LLVM 2.7-3.1.</p>
281 <h3>Glasgow Haskell Compiler (GHC)</h3>
285 <p><a href="http://www.haskell.org/ghc/">GHC</a> is an open source compiler and
286 programming suite for Haskell, a lazy functional programming language. It
287 includes an optimizing static compiler generating good code for a variety of
288 platforms, together with an interactive system for convenient, quick
291 <p>GHC 7.0 and onwards include an LLVM code generator, supporting LLVM 2.8 and
300 <p><a href="https://github.com/JuliaLang/julia">Julia</a> is a high-level,
301 high-performance dynamic language for technical computing. It provides a
302 sophisticated compiler, distributed parallel execution, numerical accuracy,
303 and an extensive mathematical function library. The compiler uses type
304 inference to generate fast code without any type declarations, and uses
305 LLVM's optimization passes and JIT compiler. The
306 <a href="http://julialang.org/"> Julia Language</a> is designed
307 around multiple dispatch, giving programs a large degree of flexibility. It
308 is ready for use on many kinds of problems.</p>
312 <h3>LLVM D Compiler</h3>
316 <p><a href="https://github.com/ldc-developers/ldc">LLVM D Compiler</a> (LDC) is
317 a compiler for the D programming Language. It is based on the DMD frontend
318 and uses LLVM as backend.</p>
322 <h3>Open Shading Language</h3>
326 <p><a href="https://github.com/imageworks/OpenShadingLanguage/">Open Shading
327 Language (OSL)</a> is a small but rich language for programmable shading in
328 advanced global illumination renderers and other applications, ideal for
329 describing materials, lights, displacement, and pattern generation. It uses
330 LLVM to JIT complex shader networks to x86 code at runtime.</p>
332 <p>OSL was developed by Sony Pictures Imageworks for use in its in-house
333 renderer used for feature film animation and visual effects, and is
334 distributed as open source software with the "New BSD" license.</p>
338 <h3>Portable OpenCL (pocl)</h3>
342 <p>In addition to producing an easily portable open source OpenCL
343 implementation, another major goal of <a href="http://pocl.sourceforge.net/">
344 pocl</a> is improving performance portability of OpenCL programs with
345 compiler optimizations, reducing the need for target-dependent manual
346 optimizations. An important part of pocl is a set of LLVM passes used to
347 statically parallelize multiple work-items with the kernel compiler, even in
348 the presence of work-group barriers. This enables static parallelization of
349 the fine-grained static concurrency in the work groups in multiple ways
350 (SIMD, VLIW, superscalar,...).</p>
358 <p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
359 algebraic/functional programming language based on term rewriting. Programs
360 are collections of equations which are used to evaluate expressions in a
361 symbolic fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
362 programs to fast native code. Pure offers dynamic typing, eager and lazy
363 evaluation, lexical closures, a hygienic macro system (also based on term
364 rewriting), built-in list and matrix support (including list and matrix
365 comprehensions) and an easy-to-use interface to C and other programming
366 languages (including the ability to load LLVM bitcode modules, and inline C,
367 C++, Fortran and Faust code in Pure programs if the corresponding
368 LLVM-enabled compilers are installed).</p>
370 <p>Pure version 0.54 has been tested and is known to work with LLVM 3.1 (and
371 continues to work with older LLVM releases >= 2.5).</p>
375 <h3>TTA-based Co-design Environment (TCE)</h3>
379 <p><a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing
380 application-specific processors (ASP) based on the Transport triggered
381 architecture (TTA). The toolset provides a complete co-design flow from C/C++
382 programs down to synthesizable VHDL/Verilog and parallel program binaries.
383 Processor customization points include the register files, function units,
384 supported operations, and the interconnection network.</p>
386 <p>TCE uses Clang and LLVM for C/C++ language support, target independent
387 optimizations and also for parts of code generation. It generates new
388 LLVM-based code generators "on the fly" for the designed TTA processors and
389 loads them in to the compiler backend as runtime libraries to avoid
390 per-target recompilation of larger parts of the compiler chain.</p>
396 <!-- *********************************************************************** -->
398 <a name="whatsnew">What's New in LLVM 3.2?</a>
400 <!-- *********************************************************************** -->
404 <p>This release includes a huge number of bug fixes, performance tweaks and
405 minor improvements. Some of the major improvements and new features are
406 listed in this section.</p>
408 <!--=========================================================================-->
410 <a name="majorfeatures">Major New Features</a>
415 <!-- Features that need text if they're finished for 3.2:
419 loop dependence analysis
420 CorrelatedValuePropagation
421 lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.2.
422 Integrated assembler on by default for arm/thumb?
427 Analysis/RegionInfo.h + Dom Frontiers
428 SparseBitVector: used in LiveVar.
429 llvm/lib/Archive - replace with lib object?
432 <p>LLVM 3.2 includes several major changes and big features:</p>
441 <!--=========================================================================-->
443 <a name="coreimprovements">LLVM IR and Core Improvements</a>
448 <p>LLVM IR has several new features for better support of new targets and that
449 expose new optimization opportunities:</p>
452 <li>Thread local variables may have a specified TLS model. See the
453 <a href="LangRef.html#globalvars">Language Reference Manual</a>.</li>
459 <!--=========================================================================-->
461 <a name="optimizer">Optimizer Improvements</a>
466 <p>In addition to many minor performance tweaks and bug fixes, this release
467 includes a few major enhancements and additions to the optimizers:</p>
475 <!--=========================================================================-->
477 <a name="mc">MC Level Improvements</a>
482 <p>The LLVM Machine Code (aka MC) subsystem was created to solve a number of
483 problems in the realm of assembly, disassembly, object file format handling,
484 and a number of other related areas that CPU instruction-set level tools work
485 in. For more information, please see the
486 <a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
487 to the LLVM MC Project Blog Post</a>.</p>
495 <!--=========================================================================-->
497 <a name="codegen">Target Independent Code Generator Improvements</a>
502 <p>We have put a significant amount of work into the code generator
503 infrastructure, which allows us to implement more aggressive algorithms and
504 make it run faster:</p>
510 <p> We added new TableGen infrastructure to support bundling for
511 Very Long Instruction Word (VLIW) architectures. TableGen can now
512 automatically generate a deterministic finite automaton from a VLIW
513 target's schedule description which can be queried to determine
514 legal groupings of instructions in a bundle.</p>
516 <p> We have added a new target independent VLIW packetizer based on the
517 DFA infrastructure to group machine instructions into bundles.</p>
522 <a name="blockplacement">Basic Block Placement</a>
527 <p>A probability based block placement and code layout algorithm was added to
528 LLVM's code generator. This layout pass supports probabilities derived from
529 static heuristics as well as source code annotations such as
530 <code>__builtin_expect</code>.</p>
534 <!--=========================================================================-->
536 <a name="x86">X86-32 and X86-64 Target Improvements</a>
541 <p>New features and major changes in the X86 target include:</p>
549 <!--=========================================================================-->
551 <a name="ARM">ARM Target Improvements</a>
556 <p>New features of the ARM target include:</p>
562 <!--_________________________________________________________________________-->
565 <a name="armintegratedassembler">ARM Integrated Assembler</a>
570 <p>The ARM target now includes a full featured macro assembler, including
571 direct-to-object module support for clang. The assembler is currently enabled
572 by default for Darwin only pending testing and any additional necessary
573 platform specific support for Linux.</p>
575 <p>Full support is included for Thumb1, Thumb2 and ARM modes, along with
576 subtarget and CPU specific extensions for VFP2, VFP3 and NEON.</p>
578 <p>The assembler is Unified Syntax only (see ARM Architecural Reference Manual
579 for details). While there is some, and growing, support for pre-unfied
580 (divided) syntax, there are still significant gaps in that support.</p>
586 <!--=========================================================================-->
588 <a name="MIPS">MIPS Target Improvements</a>
593 <p>New features and major changes in the MIPS target include:</p>
601 <!--=========================================================================-->
603 <a name="OtherTS">Other Target Specific Improvements</a>
614 <!--=========================================================================-->
616 <a name="changes">Major Changes and Removed Features</a>
621 <p>If you're already an LLVM user or developer with out-of-tree changes based on
622 LLVM 3.2, this section lists some "gotchas" that you may run into upgrading
623 from the previous release.</p>
631 <!--=========================================================================-->
633 <a name="api_changes">Internal API Changes</a>
638 <p>In addition, many APIs have changed in this release. Some of the major
639 LLVM API changes are:</p>
647 <!--=========================================================================-->
649 <a name="tools_changes">Tools Changes</a>
654 <p>In addition, some tools have changed in this release. Some of the changes
664 <!--=========================================================================-->
666 <a name="python">Python Bindings</a>
671 <p>Officially supported Python bindings have been added! Feature support is far
672 from complete. The current bindings support interfaces to:</p>
682 <!-- *********************************************************************** -->
684 <a name="knownproblems">Known Problems</a>
686 <!-- *********************************************************************** -->
690 <p>LLVM is generally a production quality compiler, and is used by a broad range
691 of applications and shipping in many products. That said, not every
692 subsystem is as mature as the aggregate, particularly the more obscure
693 targets. If you run into a problem, please check
694 the <a href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
695 there isn't already one or ask on
696 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
699 <p>Known problem areas include:</p>
702 <li>The CellSPU, MSP430, PTX and XCore backends are experimental.</li>
704 <li>The integrated assembler, disassembler, and JIT is not supported by
705 several targets. If an integrated assembler is not supported, then a
706 system assembler is required. For more details, see the <a
707 href="CodeGenerator.html#targetfeatures">Target Features Matrix</a>.
713 <!-- *********************************************************************** -->
715 <a name="additionalinfo">Additional Information</a>
717 <!-- *********************************************************************** -->
721 <p>A wide variety of additional information is available on
722 the <a href="http://llvm.org/">LLVM web page</a>, in particular in
723 the <a href="http://llvm.org/docs/">documentation</a> section. The web page
724 also contains versions of the API documentation which is up-to-date with the
725 Subversion version of the source code. You can access versions of these
726 documents specific to this release by going into the "<tt>llvm/doc/</tt>"
727 directory in the LLVM tree.</p>
729 <p>If you have any questions or comments about LLVM, please feel free to contact
730 us via the <a href="http://llvm.org/docs/#maillist"> mailing lists</a>.</p>
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