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11 <h1>LLVM 3.0 Release Notes</h1>
13 <img align=right src="http://llvm.org/img/DragonSmall.png"
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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 3.0</a></li>
20 <li><a href="#whatsnew">What's New in LLVM 3.0?</a></li>
21 <li><a href="GettingStarted.html">Installation Instructions</a></li>
22 <li><a href="#knownproblems">Known Problems</a></li>
23 <li><a href="#additionalinfo">Additional Information</a></li>
26 <div class="doc_author">
27 <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 3.0
34 <a href="http://llvm.org/releases/2.9/docs/ReleaseNotes.html">LLVM 2.9
35 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 3.0. Here we describe the status of LLVM, including
48 major improvements from the previous release and significant known problems.
49 All LLVM releases may be downloaded from the <a
50 href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
52 <p>For more information about LLVM, including information about the latest
53 release, please check out the <a href="http://llvm.org/">main LLVM
54 web site</a>. If you have questions or comments, the <a
55 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
56 Mailing List</a> is a good place to send them.</p>
58 <p>Note that if you are reading this file from a Subversion checkout or the
59 main LLVM web page, this document applies to the <i>next</i> release, not the
60 current one. To see the release notes for a specific release, please see the
61 <a href="http://llvm.org/releases/">releases page</a>.</p>
65 <!-- Features that need text if they're finished for 3.1:
69 loop dependence analysis
70 CorrelatedValuePropagation
71 lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
74 <!-- *********************************************************************** -->
76 <a name="subproj">Sub-project Status Update</a>
78 <!-- *********************************************************************** -->
82 The LLVM 3.0 distribution currently consists of code from the core LLVM
83 repository (which roughly includes the LLVM optimizers, code generators
84 and supporting tools), the Clang repository and the llvm-gcc repository. In
85 addition to this code, the LLVM Project includes other sub-projects that are in
86 development. Here we include updates on these subprojects.
89 <!--=========================================================================-->
91 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
96 <p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
97 C++, and Objective-C languages. Clang aims to provide a better user experience
98 through expressive diagnostics, a high level of conformance to language
99 standards, fast compilation, and low memory use. Like LLVM, Clang provides a
100 modular, library-based architecture that makes it suitable for creating or
101 integrating with other development tools. Clang is considered a
102 production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
103 (32- and 64-bit), and for darwin/arm targets.</p>
105 <p>In the LLVM 3.0 time-frame, the Clang team has made many improvements:</p>
108 <li>Greatly improved support for building C++ applications, with greater stability and better diagnostics.</li>
110 <li><a href="http://clang.llvm.org/cxx_status.html">Improved support</a> for the <a href="http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50372 ">C++ 2011</a> standard, including implementations of non-static data member initializers, alias templates, delegating constructors, the range-based for loop, and implicitly-generated move constructors and move assignment operators, among others.</li>
112 <li>Implemented support for some features of the upcoming C1x standard, including static assertions and generic selections.</li>
114 <li>Better detection of include and linking paths for system headers and libraries, especially for Linux distributions.</li>
116 <li>Implemented support for <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">Automatic Reference Counting</a> for Objective-C.</li>
118 <li>Implemented a number of optimizations in <tt>libclang</tt>, the Clang C interface, to improve the performance of code completion and the mapping from source locations to abstract syntax tree nodes.</li>
122 <p>If Clang rejects your code but another compiler accepts it, please take a
123 look at the <a href="http://clang.llvm.org/compatibility.html">language
124 compatibility</a> guide to make sure this is not intentional or a known issue.
129 <!--=========================================================================-->
131 <a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
136 <a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
137 <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
138 optimizers and code generators with LLVM's.
139 Currently it requires a patched version of gcc-4.5.
140 The plugin can target the x86-32 and x86-64 processor families and has been
141 used successfully on the Darwin, FreeBSD and Linux platforms.
142 The Ada, C, C++ and Fortran languages work well.
143 The plugin is capable of compiling plenty of Obj-C, Obj-C++ and Java but it is
144 not known whether the compiled code actually works or not!
148 The 3.0 release has the following notable changes:
157 <!--=========================================================================-->
159 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
164 The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
165 is a simple library that provides an implementation of the low-level
166 target-specific hooks required by code generation and other runtime components.
167 For example, when compiling for a 32-bit target, converting a double to a 64-bit
168 unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
169 function. The compiler-rt library provides highly optimized implementations of
170 this and other low-level routines (some are 3x faster than the equivalent
171 libgcc routines).</p>
173 <p>In the LLVM 3.0 timeframe,</p>
177 <!--=========================================================================-->
179 <a name="lldb">LLDB: Low Level Debugger</a>
184 <a href="http://lldb.llvm.org/">LLDB</a> is a brand new member of the LLVM
185 umbrella of projects. LLDB is a next generation, high-performance debugger. It
186 is built as a set of reusable components which highly leverage existing
187 libraries in the larger LLVM Project, such as the Clang expression parser, the
188 LLVM disassembler and the LLVM JIT.</p>
191 LLDB is has advanced by leaps and bounds in the 3.0 timeframe. It is
192 dramatically more stable and useful, and includes both a new <a
193 href="http://lldb.llvm.org/tutorial.html">tutorial</a> and a <a
194 href="http://lldb.llvm.org/lldb-gdb.html">side-by-side comparison with
199 <!--=========================================================================-->
201 <a name="libc++">libc++: C++ Standard Library</a>
206 <a href="http://libcxx.llvm.org/">libc++</a> is another new member of the LLVM
207 family. It is an implementation of the C++ standard library, written from the
208 ground up to specifically target the forthcoming C++'0X standard and focus on
209 delivering great performance.</p>
212 In the LLVM 3.0 timeframe,</p>
215 Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
216 licensed</a> under the MIT and UIUC license, allowing it to be used more
223 <!--=========================================================================-->
225 <a name="LLBrowse">LLBrowse: IR Browser</a>
230 <a href="http://llvm.org/svn/llvm-project/llbrowse/trunk/doc/LLBrowse.html">
231 LLBrowse</a> is an interactive viewer for LLVM modules. It can load any LLVM
232 module and displays its contents as an expandable tree view, facilitating an
233 easy way to inspect types, functions, global variables, or metadata nodes. It
234 is fully cross-platform, being based on the popular wxWidgets GUI toolkit.
238 <!--=========================================================================-->
240 <a name="vmkit">VMKit</a>
244 <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
245 of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
246 just-in-time compilation. As of LLVM 3.0, VMKit now supports generational
247 garbage collectors. The garbage collectors are provided by the MMTk framework,
248 and VMKit can be configured to use one of the numerous implemented collectors
254 <!--=========================================================================-->
257 <a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
262 <a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
263 programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
264 through the application and records state transitions that lead to fault
265 states. This allows it to construct testcases that lead to faults and can even
266 be used to verify some algorithms.
274 <!-- *********************************************************************** -->
276 <a name="externalproj">External Open Source Projects Using LLVM 3.0</a>
278 <!-- *********************************************************************** -->
282 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
283 a lot of other language and tools projects. This section lists some of the
284 projects that have already been updated to work with LLVM 3.0.</p>
286 <!--=========================================================================-->
287 <h3>AddressSanitizer</h3>
291 <p><a href="http://code.google.com/p/address-sanitizer/">AddressSanitizer</a>
292 uses compiler instrumentation and a specialized malloc library to find C/C++
293 bugs such as use-after-free and out-of-bound accesses to heap, stack, and
294 globals. The key feature of the tool is speed: the average slowdown
295 introduced by AddressSanitizer is less than 2x.</p>
299 <!--=========================================================================-->
304 <p><a href="http://www.clamav.net">Clam AntiVirus</a> is an open source (GPL)
305 anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail
308 <p>Since version 0.96 it
309 has <a href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode
310 signatures</a> that allow writing detections for complex malware.</p>
312 <p>It uses LLVM's JIT to speed up the execution of bytecode on X86, X86-64,
313 PPC32/64, falling back to its own interpreter otherwise. The git version was
314 updated to work with LLVM 3.0.</p>
318 <!--=========================================================================-->
319 <!-- FIXME: Comment out
320 <h3>Crack Programming Language</h3>
324 <a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide the
325 ease of development of a scripting language with the performance of a compiled
326 language. The language derives concepts from C++, Java and Python, incorporating
327 object-oriented programming, operator overloading and strong typing.</p>
331 <!--=========================================================================-->
332 <h3>Glasgow Haskell Compiler (GHC)</h3>
336 <p>GHC is an open source, state-of-the-art programming suite for Haskell, a
337 standard lazy functional programming language. It includes an optimizing
338 static compiler generating good code for a variety of platforms, together
339 with an interactive system for convenient, quick development.</p>
341 <p>GHC 7.0 and onwards include an LLVM code generator, supporting LLVM 2.8 and
342 later. Since LLVM 2.9, GHC now includes experimental support for the ARM
343 platform with LLVM 3.0.</p>
347 <!--=========================================================================-->
352 <p><a href="http://botwars.tk/gwscript/">gwXscript</a> is an object oriented,
353 aspect oriented programming language which can create both executables (ELF,
354 EXE) and shared libraries (DLL, SO, DYNLIB). The compiler is implemented in
355 its own language and translates scripts into LLVM-IR which can be optimized
356 and translated into native code by the LLVM framework. Source code in
357 gwScript contains definitions that expand the namespaces. So you can build
358 your project and simply 'plug out' features by removing a file. The remaining
359 project does not leave scars since you directly separate concerns by the
360 'template' feature of gwX. It is also possible to add new features to a
361 project by just adding files and without editing the original project. This
362 language is used for example to create games or content management systems
363 that should be extendable.</p>
365 <p>gwXscript is strongly typed and offers comfort with its native types string,
366 hash and array. You can easily write new libraries in gwXscript or native
367 code. gwXscript is type safe and users should not be able to crash your
368 program or execute malicious code except code that is eating CPU time.</p>
372 <!--=========================================================================-->
373 <h3>LanguageKit and Pragmatic Smalltalk</h3>
377 <p><a href="http://etoileos.com/etoile/features/languagekit/">LanguageKit</a> is
378 a framework for implementing dynamic languages sharing an object model with
379 Objective-C. It provides static and JIT compilation using LLVM along with
380 its own interpreter. Pragmatic Smalltalk is a dialect of Smalltalk, built on
381 top of LanguageKit, that interfaces directly with Objective-C, sharing the
382 same object representation and message sending behaviour. These projects are
383 developed as part of the Étoié desktop environment.</p>
387 <!--=========================================================================-->
392 <p>An open source, cross-platform implementation of C# and the CLR that is
393 binary compatible with Microsoft.NET. Has an optional, dynamically-loaded
394 LLVM code generation backend in Mini, the JIT compiler.</p>
396 <p>Note that we use a Git mirror of LLVM with some patches. See:
397 https://github.com/mono/llvm</p>
401 <!--=========================================================================-->
402 <h3>Portable OpenCL (pocl)</h3>
406 <p>Portable OpenCL is an open source implementation of the OpenCL standard which
407 can be easily adapted for new targets. One of the goals of the project is
408 improving performance portability of OpenCL programs, avoiding the need for
409 target-dependent manual optimizations. A "native" target is included, which
410 allows running OpenCL kernels on the host (CPU).</p>
414 <!--=========================================================================-->
418 <p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
419 algebraic/functional programming language based on term rewriting. Programs
420 are collections of equations which are used to evaluate expressions in a
421 symbolic fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
422 programs to fast native code. Pure offers dynamic typing, eager and lazy
423 evaluation, lexical closures, a hygienic macro system (also based on term
424 rewriting), built-in list and matrix support (including list and matrix
425 comprehensions) and an easy-to-use interface to C and other programming
426 languages (including the ability to load LLVM bitcode modules, and inline C,
427 C++, Fortran and Faust code in Pure programs if the corresponding LLVM-enabled
428 compilers are installed).</p>
430 <p>Pure version 0.48 has been tested and is known to work with LLVM 3.0
431 (and continues to work with older LLVM releases >= 2.5).</p>
435 <!--=========================================================================-->
436 <h3>Renderscript</h3>
440 <p><a href="http://developer.android.com/guide/topics/renderscript/index.html">Renderscript</a>
441 is Android's advanced 3D graphics rendering and compute API. It provides a
442 portable C99-based language with extensions to facilitate common use cases
443 for enhancing graphics and thread level parallelism. The Renderscript
444 compiler frontend is based on Clang/LLVM. It emits a portable bitcode format
445 for the actual compiled script code, as well as reflects a Java interface for
446 developers to control the execution of the compiled bitcode. Executable
447 machine code is then generated from this bitcode by an LLVM backend on the
448 device. Renderscript is thus able to provide a mechanism by which Android
449 developers can improve performance of their applications while retaining
454 <!--=========================================================================-->
459 <p><a href="http://safecode.cs.illinois.edu">SAFECode</a> is a memory safe C/C++
460 compiler built using LLVM. It takes standard, unannotated C/C++ code,
461 analyzes the code to ensure that memory accesses and array indexing
462 operations are safe, and instruments the code with run-time checks when
463 safety cannot be proven statically. SAFECode can be used as a debugging aid
464 (like Valgrind) to find and repair memory safety bugs. It can also be used
465 to protect code from security attacks at run-time.</p>
469 <!--=========================================================================-->
470 <h3>The Stupid D Compiler (SDC)</h3>
474 <p><a href="https://github.com/bhelyer/SDC">The Stupid D Compiler</a> is a
475 project seeking to write a self-hosting compiler for the D programming
476 language without using the frontend of the reference compiler (DMD).</p>
480 <!--=========================================================================-->
481 <h3>TTA-based Co-design Environment (TCE)</h3>
485 <p>TCE is a toolset for designing application-specific processors (ASP) based on
486 the Transport triggered architecture (TTA). The toolset provides a complete
487 co-design flow from C/C++ programs down to synthesizable VHDL and parallel
488 program binaries. Processor customization points include the register files,
489 function units, supported operations, and the interconnection network.</p>
491 <p>TCE uses Clang and LLVM for C/C++ language support, target independent
492 optimizations and also for parts of code generation. It generates new
493 LLVM-based code generators <i>on the fly</i> for the designed TTA processors
494 and loads them in to the compiler backend as runtime libraries to avoid
495 per-target recompilation of larger parts of the compiler chain.</p>
499 <!--=========================================================================-->
500 <h3>Tart Programming Language</h3>
504 <p><a href="http://code.google.com/p/tart/">Tart</a> is a general-purpose,
505 strongly typed programming language designed for application
506 developers. Strongly inspired by Python and C#, Tart focuses on practical
507 solutions for the professional software developer, while avoiding the clutter
508 and boilerplate of legacy languages like Java and C++. Although Tart is still
509 in development, the current implementation supports many features expected of
510 a modern programming language, such as garbage collection, powerful
511 bidirectional type inference, a greatly simplified syntax for template
512 metaprogramming, closures and function literals, reflection, operator
513 overloading, explicit mutability and immutability, and much more. Tart is
514 flexible enough to accommodate a broad range of programming styles and
515 philosophies, while maintaining a strong commitment to simplicity, minimalism
516 and elegance in design.</p>
520 <!--=========================================================================-->
521 <h3>ThreadSanitizer</h3>
525 <p><a href="http://code.google.com/p/data-race-test/">ThreadSanitizer</a> is a
526 data race detector for (mostly) C and C++ code, available for Linux, Mac OS
527 and Windows. On different systems, we use binary instrumentation frameworks
528 (Valgrind, Pin and DynamoRio) as frontends that generate the program events
529 for the race detection algorithm. On Linux, there's an option of using
530 LLVM-based compile-time instrumentation.</p>
534 <!--=========================================================================-->
535 <h3>The ZooLib C++ Cross-Platform Application Framework</h3>
539 <p><a href="http://www.zoolib.org/">ZooLib</a> is Open Source under the MIT
540 License. It provides GUI, filesystem access, TCP networking, thread-safe
541 memory management, threading and locking for Mac OS X, Classic Mac OS,
542 Microsoft Windows, POSIX operating systems with X11, BeOS, Haiku, Apple's iOS
543 and Research in Motion's BlackBerry.</p>
545 <p>My current work is to use CLang's static analyzer to improve ZooLib's code
546 quality. I also plan to set up LLVM compiles of the demo programs and test
547 programs using CLang and LLVM on all the platforms that CLang, LLVM and
548 ZooLib all support.</p>
552 <!--=========================================================================-->
557 <p><a href="http://gitorious.org/pinavm/pages/Home">PinaVM</a> is an open
558 source, <a href="http://www.systemc.org/">SystemC</a> front-end. Unlike many
559 other front-ends, PinaVM actually executes the elaboration of the
560 program analyzed using LLVM's JIT infrastructure. It later enriches the
561 bitcode with SystemC-specific information.</p>
566 <!--=========================================================================-->
568 <h3 id="icedtea">IcedTea Java Virtual Machine Implementation</h3>
572 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
573 harness to build OpenJDK using only free software build tools and to provide
574 replacements for the not-yet free parts of OpenJDK. One of the extensions that
575 IcedTea provides is a new JIT compiler named <a
576 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
577 to provide native code generation without introducing processor-dependent
581 <p> OpenJDK 7 b112, IcedTea6 1.9 and IcedTea7 1.13 and later have been tested
582 and are known to work with LLVM 3.0 (and continue to work with older LLVM
583 releases >= 2.6 as well).</p>
587 <!--=========================================================================-->
589 <h3>Polly - Polyhedral optimizations for LLVM</h3>
592 <p>Polly is a project that aims to provide advanced memory access optimizations
593 to better take advantage of SIMD units, cache hierarchies, multiple cores or
594 even vector accelerators for LLVM. Built around an abstract mathematical
595 description based on Z-polyhedra, it provides the infrastructure to develop
596 advanced optimizations in LLVM and to connect complex external optimizers. In
597 its first year of existence Polly already provides an exact value-based
598 dependency analysis as well as basic SIMD and OpenMP code generation support.
599 Furthermore, Polly can use PoCC(Pluto) an advanced optimizer for data-locality
604 <!--=========================================================================-->
609 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
610 for running Ruby code which strives to write as much of the implementation in
611 Ruby as possible. Combined with a bytecode interpreting VM, it uses LLVM to
612 optimize and compile ruby code down to machine code. Techniques such as type
613 feedback, method inlining, and deoptimization are all used to remove dynamism
614 from ruby execution and increase performance.</p>
618 <!--=========================================================================-->
621 <a name="FAUST">FAUST Real-Time Audio Signal Processing Language</a>
626 <a href="http://faust.grame.fr">FAUST</a> is a compiled language for real-time
627 audio signal processing. The name FAUST stands for Functional AUdio STream. Its
628 programming model combines two approaches: functional programming and block
629 diagram composition. In addition with the C, C++, JAVA output formats, the
630 Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7-3.0.</p>
637 <!-- *********************************************************************** -->
639 <a name="whatsnew">What's New in LLVM 3.0?</a>
641 <!-- *********************************************************************** -->
645 <p>This release includes a huge number of bug fixes, performance tweaks and
646 minor improvements. Some of the major improvements and new features are listed
650 <!--=========================================================================-->
652 <a name="majorfeatures">Major New Features</a>
657 <p>LLVM 3.0 includes several major new capabilities:</p>
669 <!--=========================================================================-->
671 <a name="coreimprovements">LLVM IR and Core Improvements</a>
675 <p>LLVM IR has several new features for better support of new targets and that
676 expose new optimization opportunities:</p>
686 <!--=========================================================================-->
688 <a name="optimizer">Optimizer Improvements</a>
693 <p>In addition to a large array of minor performance tweaks and bug fixes, this
694 release includes a few major enhancements and additions to the optimizers:</p>
706 <!--=========================================================================-->
708 <a name="mc">MC Level Improvements</a>
713 The LLVM Machine Code (aka MC) subsystem was created to solve a number
714 of problems in the realm of assembly, disassembly, object file format handling,
715 and a number of other related areas that CPU instruction-set level tools work
724 <p>For more information, please see the <a
725 href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
726 LLVM MC Project Blog Post</a>.
731 <!--=========================================================================-->
733 <a name="codegen">Target Independent Code Generator Improvements</a>
738 <p>We have put a significant amount of work into the code generator
739 infrastructure, which allows us to implement more aggressive algorithms and make
749 <!--=========================================================================-->
751 <a name="x86">X86-32 and X86-64 Target Improvements</a>
755 <p>New features and major changes in the X86 target include:
759 <li>The CRC32 intrinsics have been renamed. The intrinsics were previously
760 @llvm.x86.sse42.crc32.[8|16|32] and @llvm.x86.sse42.crc64.[8|64]. They have
761 been renamed to @llvm.x86.sse42.crc32.32.[8|16|32] and
762 @llvm.x86.sse42.crc32.64.[8|64].</li>
768 <!--=========================================================================-->
770 <a name="ARM">ARM Target Improvements</a>
774 <p>New features of the ARM target include:
784 <!--=========================================================================-->
786 <a name="OtherTS">Other Target Specific Improvements</a>
797 <!--=========================================================================-->
799 <a name="changes">Major Changes and Removed Features</a>
804 <p>If you're already an LLVM user or developer with out-of-tree changes based on
805 LLVM 2.9, this section lists some "gotchas" that you may run into upgrading
806 from the previous release.</p>
809 <li>The <code>LLVMC</code> front end code was removed while separating
810 out language independence.</li>
811 <li>The <code>LowerSetJmp</code> pass wasn't used effectively by any
812 target and has been removed.</li>
813 <li>The old <code>TailDup</code> pass was not used in the standard pipeline
814 and was unable to update ssa form, so it has been removed.
815 <li>The syntax of volatile loads and stores in IR has been changed to
816 "<code>load volatile</code>"/"<code>store volatile</code>". The old
817 syntax ("<code>volatile load</code>"/"<code>volatile store</code>")
818 is still accepted, but is now considered deprecated.</li>
819 <li>The old atomic intrinscs (<code>llvm.memory.barrier</code> and
820 <code>llvm.atomic.*</code>) are now gone. Please use the new atomic
821 instructions, described in the <a href="Atomics.html">atomics guide</a>.
824 <h4>Windows (32-bit)</h4>
827 <li>On Win32(MinGW32 and MSVC), Windows 2000 will not be supported.
828 Windows XP or higher is required.</li>
834 <!--=========================================================================-->
836 <a name="api_changes">Internal API Changes</a>
841 <p>In addition, many APIs have changed in this release. Some of the major
842 LLVM API changes are:</p>
845 <li>The biggest and most pervasive change is that llvm::Type's are no longer
846 returned or accepted as 'const' values. Instead, just pass around non-const
849 <li><code>PHINode::reserveOperandSpace</code> has been removed. Instead, you
850 must specify how many operands to reserve space for when you create the
851 PHINode, by passing an extra argument into <code>PHINode::Create</code>.</li>
853 <li>PHINodes no longer store their incoming BasicBlocks as operands. Instead,
854 the list of incoming BasicBlocks is stored separately, and can be accessed
855 with new functions <code>PHINode::block_begin</code>
856 and <code>PHINode::block_end</code>.</li>
858 <li>Various functions now take an <code>ArrayRef</code> instead of either a pair
859 of pointers (or iterators) to the beginning and end of a range, or a pointer
860 and a length. Others now return an <code>ArrayRef</code> instead of a
861 reference to a <code>SmallVector</code> or <code>std::vector</code>. These
864 <!-- Please keep this list sorted. -->
865 <li><code>CallInst::Create</code></li>
866 <li><code>ComputeLinearIndex</code> (in <code>llvm/CodeGen/Analysis.h</code>)</li>
867 <li><code>ConstantArray::get</code></li>
868 <li><code>ConstantExpr::getExtractElement</code></li>
869 <li><code>ConstantExpr::getGetElementPtr</code></li>
870 <li><code>ConstantExpr::getInBoundsGetElementPtr</code></li>
871 <li><code>ConstantExpr::getIndices</code></li>
872 <li><code>ConstantExpr::getInsertElement</code></li>
873 <li><code>ConstantExpr::getWithOperands</code></li>
874 <li><code>ConstantFoldCall</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
875 <li><code>ConstantFoldInstOperands</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
876 <li><code>ConstantVector::get</code></li>
877 <li><code>DIBuilder::createComplexVariable</code></li>
878 <li><code>DIBuilder::getOrCreateArray</code></li>
879 <li><code>ExtractValueInst::Create</code></li>
880 <li><code>ExtractValueInst::getIndexedType</code></li>
881 <li><code>ExtractValueInst::getIndices</code></li>
882 <li><code>FindInsertedValue</code> (in <code>llvm/Analysis/ValueTracking.h</code>)</li>
883 <li><code>gep_type_begin</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
884 <li><code>gep_type_end</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
885 <li><code>GetElementPtrInst::Create</code></li>
886 <li><code>GetElementPtrInst::CreateInBounds</code></li>
887 <li><code>GetElementPtrInst::getIndexedType</code></li>
888 <li><code>InsertValueInst::Create</code></li>
889 <li><code>InsertValueInst::getIndices</code></li>
890 <li><code>InvokeInst::Create</code></li>
891 <li><code>IRBuilder::CreateCall</code></li>
892 <li><code>IRBuilder::CreateExtractValue</code></li>
893 <li><code>IRBuilder::CreateGEP</code></li>
894 <li><code>IRBuilder::CreateInBoundsGEP</code></li>
895 <li><code>IRBuilder::CreateInsertValue</code></li>
896 <li><code>IRBuilder::CreateInvoke</code></li>
897 <li><code>MDNode::get</code></li>
898 <li><code>MDNode::getIfExists</code></li>
899 <li><code>MDNode::getTemporary</code></li>
900 <li><code>MDNode::getWhenValsUnresolved</code></li>
901 <li><code>SimplifyGEPInst</code> (in <code>llvm/Analysis/InstructionSimplify.h</code>)</li>
902 <li><code>TargetData::getIndexedOffset</code></li>
905 <li>All forms of <code>StringMap::getOrCreateValue</code> have been remove
906 except for the one which takes a <code>StringRef</code>.</li>
908 <li>The <code>LLVMBuildUnwind</code> function from the C API was removed. The
909 LLVM <code>unwind</code> instruction has been deprecated for a long time and
910 isn't used by the current front-ends. So this was removed during the
911 exception handling rewrite.</li>
913 <li>The <code>LLVMAddLowerSetJmpPass</code> function from the C API was removed
914 because the <code>LowerSetJmp</code> pass was removed.</li>
916 <li>The <code>DIBuilder</code> interface used by front ends to encode debugging
917 information in the LLVM IR now expects clients to use <code>DIBuilder::finalize()</code>
918 at the end of translation unit to complete debugging information encoding.</li>
920 <li>The way the type system works has been rewritten: <code>PATypeHolder</code>
921 and <code>OpaqueType</code> are gone, and all APIs deal with <code>Type*</code>
922 instead of <code>const Type*</code>.
923 If you need to create recursive structures, then create a named structure,
924 and use <code>setBody()</code> when all its elements are built.
925 Type merging and refining is gone too: named structures are not
926 merged with other structures, even if their layout is identical.
927 (of course anonymous structures are still uniqued by layout).
930 <li>TargetSelect.h moved to Support/ from Target/</li>
932 <li>UpgradeIntrinsicCall no longer upgrades pre-2.9 intrinsic calls
933 (for example <code>llvm.memset.i32</code>).</li>
935 <li>It is mandatory to initialize all out-of-tree passes too and their dependencies now with
936 <code>INITIALIZE_PASS{BEGIN,END,}</code> and <code>INITIALIZE_{PASS,AG}_DEPENDENCY</code>.</li>
938 <li>The interface for MemDepResult in MemoryDependenceAnalysis has been enhanced
939 with new return types Unknown and NonFuncLocal, in addition to the existing
940 types Clobber, Def, and NonLocal.</li>
947 <!-- *********************************************************************** -->
949 <a name="knownproblems">Known Problems</a>
951 <!-- *********************************************************************** -->
955 <p>This section contains significant known problems with the LLVM system,
956 listed by component. If you run into a problem, please check the <a
957 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
958 there isn't already one.</p>
960 <!-- ======================================================================= -->
962 <a name="experimental">Experimental features included with this release</a>
967 <p>The following components of this LLVM release are either untested, known to
968 be broken or unreliable, or are in early development. These components should
969 not be relied on, and bugs should not be filed against them, but they may be
970 useful to some people. In particular, if you would like to work on one of these
971 components, please contact us on the <a
972 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
975 <li>The Alpha, CellSPU, MicroBlaze, MSP430, MIPS, PTX,
976 and XCore backends are experimental.</li>
977 <li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets
978 other than darwin and ELF X86 systems.</li>
984 <!-- ======================================================================= -->
986 <a name="x86-be">Known problems with the X86 back-end</a>
992 <li>The X86 backend does not yet support
993 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
994 floating point stack</a>. It supports the 'f' and 't' constraints, but not
996 <li>The X86-64 backend does not yet support the LLVM IR instruction
997 <tt>va_arg</tt>. Currently, front-ends support variadic
998 argument constructs on X86-64 by lowering them manually.</li>
999 <li>Windows x64 (aka Win64) code generator has a few issues.
1001 <li>llvm-gcc cannot build the mingw-w64 runtime currently
1002 due to lack of support for the 'u' inline assembly
1003 constraint and for X87 floating point inline assembly.</li>
1004 <li>On mingw-w64, you will see unresolved symbol <tt>__chkstk</tt>
1005 due to <a href="http://llvm.org/bugs/show_bug.cgi?id=8919">Bug 8919</a>.
1006 It is fixed in <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110321/118499.html">r128206</a>.</li>
1007 <li>Miss-aligned MOVDQA might crash your program. It is due to
1008 <a href="http://llvm.org/bugs/show_bug.cgi?id=9483">Bug 9483</a>,
1009 lack of handling aligned internal globals.</li>
1017 <!-- ======================================================================= -->
1019 <a name="ppc-be">Known problems with the PowerPC back-end</a>
1025 <li>The Linux PPC32/ABI support needs testing for the interpreter and static
1026 compilation, and lacks support for debug information.</li>
1031 <!-- ======================================================================= -->
1033 <a name="arm-be">Known problems with the ARM back-end</a>
1039 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
1040 processors, thumb programs can crash or produce wrong
1041 results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
1042 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
1048 <!-- ======================================================================= -->
1050 <a name="sparc-be">Known problems with the SPARC back-end</a>
1056 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
1057 support the 64-bit SPARC ABI (-m64).</li>
1062 <!-- ======================================================================= -->
1064 <a name="mips-be">Known problems with the MIPS back-end</a>
1070 <li>64-bit MIPS targets are not supported yet.</li>
1075 <!-- ======================================================================= -->
1077 <a name="alpha-be">Known problems with the Alpha back-end</a>
1084 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
1085 appropriate nops inserted to ensure restartability.</li>
1090 <!-- ======================================================================= -->
1092 <a name="c-be">Known problems with the C back-end</a>
1097 <p>The C backend has numerous problems and is not being actively maintained.
1098 Depending on it for anything serious is not advised.</p>
1101 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
1102 inline assembly code</a>.</li>
1103 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
1104 C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
1105 C++ code compiled with <tt>llc</tt> or native compilers.</li>
1106 <li>The C backend does not support all exception handling constructs.</li>
1107 <li>The C backend does not support arbitrary precision integers.</li>
1113 <!-- ======================================================================= -->
1115 <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
1120 <p><b>LLVM 3.0 will be the last release of llvm-gcc.</b></p>
1122 <p>llvm-gcc is generally very stable for the C family of languages. The only
1123 major language feature of GCC not supported by llvm-gcc is the
1124 <tt>__builtin_apply</tt> family of builtins. However, some extensions
1125 are only supported on some targets. For example, trampolines are only
1126 supported on some targets (these are used when you take the address of a
1127 nested function).</p>
1129 <p>Fortran support generally works, but there are still several unresolved bugs
1130 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
1131 tools/gfortran component for details. Note that llvm-gcc is missing major
1132 Fortran performance work in the frontend and library that went into GCC after
1133 4.2. If you are interested in Fortran, we recommend that you consider using
1134 <a href="#dragonegg">dragonegg</a> instead.</p>
1136 <p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
1137 actively maintained. If you are interested in Ada, we recommend that you
1138 consider using <a href="#dragonegg">dragonegg</a> instead.</p>
1143 <!-- *********************************************************************** -->
1145 <a name="additionalinfo">Additional Information</a>
1147 <!-- *********************************************************************** -->
1151 <p>A wide variety of additional information is available on the <a
1152 href="http://llvm.org/">LLVM web page</a>, in particular in the <a
1153 href="http://llvm.org/docs/">documentation</a> section. The web page also
1154 contains versions of the API documentation which is up-to-date with the
1155 Subversion version of the source code.
1156 You can access versions of these documents specific to this release by going
1157 into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
1159 <p>If you have any questions or comments about LLVM, please feel free to contact
1160 us via the <a href="http://llvm.org/docs/#maillist"> mailing
1165 <!-- *********************************************************************** -->
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