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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
50 the <a 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 web
54 site</a>. If you have questions or comments,
55 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM
56 Developer's 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 main
59 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 <p>The LLVM 3.0 distribution currently consists of code from the core LLVM
83 repository (which roughly includes the LLVM optimizers, code generators and
84 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
86 in development. Here we include updates on these subprojects.</p>
88 <!--=========================================================================-->
90 <a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
95 <p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
96 C++, and Objective-C languages. Clang aims to provide a better user
97 experience through expressive diagnostics, a high level of conformance to
98 language standards, fast compilation, and low memory use. Like LLVM, Clang
99 provides a modular, library-based architecture that makes it suitable for
100 creating or integrating with other development tools. Clang is considered a
101 production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
102 (32- and 64-bit), and for darwin/arm targets.</p>
104 <p>In the LLVM 3.0 time-frame, the Clang team has made many improvements:</p>
107 <li>Greatly improved support for building C++ applications, with greater
108 stability and better diagnostics.</li>
110 <li><a href="http://clang.llvm.org/cxx_status.html">Improved support</a> for
111 the <a href="http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50372">C++
112 2011</a> standard, including implementations of non-static data member
113 initializers, alias templates, delegating constructors, the range-based
114 for loop, and implicitly-generated move constructors and move assignment
115 operators, among others.</li>
117 <li>Implemented support for some features of the upcoming C1x standard,
118 including static assertions and generic selections.</li>
120 <li>Better detection of include and linking paths for system headers and
121 libraries, especially for Linux distributions.</li>
123 <li>Implemented support
124 for <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">Automatic
125 Reference Counting</a> for Objective-C.</li>
127 <li>Implemented a number of optimizations in <tt>libclang</tt>, the Clang C
128 interface, to improve the performance of code completion and the mapping
129 from source locations to abstract syntax tree nodes.</li>
133 <p>If Clang rejects your code but another compiler accepts it, please take a
134 look at the <a href="http://clang.llvm.org/compatibility.html">language
135 compatibility</a> guide to make sure this is not intentional or a known
140 <!--=========================================================================-->
142 <a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
146 <p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
147 <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
148 optimizers and code generators with LLVM's. Currently it requires a patched
149 version of gcc-4.5. The plugin can target the x86-32 and x86-64 processor
150 families and has been used successfully on the Darwin, FreeBSD and Linux
151 platforms. The Ada, C, C++ and Fortran languages work well. The plugin is
152 capable of compiling plenty of Obj-C, Obj-C++ and Java but it is not known
153 whether the compiled code actually works or not!</p>
155 <p>The 3.0 release has the following notable changes:</p>
165 <!--=========================================================================-->
167 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
172 <p>The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
173 is a simple library that provides an implementation of the low-level
174 target-specific hooks required by code generation and other runtime
175 components. For example, when compiling for a 32-bit target, converting a
176 double to a 64-bit unsigned integer is compiled into a runtime call to the
177 "__fixunsdfdi" function. The compiler-rt library provides highly optimized
178 implementations of this and other low-level routines (some are 3x faster than
179 the equivalent libgcc routines).</p>
181 <p>In the LLVM 3.0 timeframe,</p>
185 <!--=========================================================================-->
187 <a name="lldb">LLDB: Low Level Debugger</a>
192 <p>LLDB has advanced by leaps and bounds in the 3.0 timeframe. It is
193 dramatically more stable and useful, and includes both a
194 new <a href="http://lldb.llvm.org/tutorial.html">tutorial</a> and
195 a <a href="http://lldb.llvm.org/lldb-gdb.html">side-by-side comparison with
200 <!--=========================================================================-->
202 <a name="libc++">libc++: C++ Standard Library</a>
207 <p>Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
208 licensed</a> under the MIT and UIUC license, allowing it to be used more
214 <!--=========================================================================-->
216 <a name="LLBrowse">LLBrowse: IR Browser</a>
221 <p><a href="http://llvm.org/svn/llvm-project/llbrowse/trunk/doc/LLBrowse.html">
222 LLBrowse</a> is an interactive viewer for LLVM modules. It can load any LLVM
223 module and displays its contents as an expandable tree view, facilitating an
224 easy way to inspect types, functions, global variables, or metadata nodes. It
225 is fully cross-platform, being based on the popular wxWidgets GUI
230 <!--=========================================================================-->
232 <a name="vmkit">VMKit</a>
237 <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation
238 of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
239 just-in-time compilation. As of LLVM 3.0, VMKit now supports generational
240 garbage collectors. The garbage collectors are provided by the MMTk
241 framework, and VMKit can be configured to use one of the numerous implemented
242 collectors of MMTk.</p>
247 <!--=========================================================================-->
250 <a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
255 <a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
256 programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
257 through the application and records state transitions that lead to fault
258 states. This allows it to construct testcases that lead to faults and can even
259 be used to verify some algorithms.
267 <!-- *********************************************************************** -->
269 <a name="externalproj">External Open Source Projects Using LLVM 3.0</a>
271 <!-- *********************************************************************** -->
275 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
276 a lot of other language and tools projects. This section lists some of the
277 projects that have already been updated to work with LLVM 3.0.</p>
279 <!--=========================================================================-->
280 <h3>AddressSanitizer</h3>
284 <p><a href="http://code.google.com/p/address-sanitizer/">AddressSanitizer</a>
285 uses compiler instrumentation and a specialized malloc library to find C/C++
286 bugs such as use-after-free and out-of-bound accesses to heap, stack, and
287 globals. The key feature of the tool is speed: the average slowdown
288 introduced by AddressSanitizer is less than 2x.</p>
292 <!--=========================================================================-->
297 <p><a href="http://www.clamav.net">Clam AntiVirus</a> is an open source (GPL)
298 anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail
301 <p>Since version 0.96 it
302 has <a href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode
303 signatures</a> that allow writing detections for complex malware.</p>
305 <p>It uses LLVM's JIT to speed up the execution of bytecode on X86, X86-64,
306 PPC32/64, falling back to its own interpreter otherwise. The git version was
307 updated to work with LLVM 3.0.</p>
311 <!--=========================================================================-->
316 <p><a href="https://bitbucket.org/dwilliamson/clreflect">clReflect</a> is a C++
317 parser that uses clang/LLVM to derive a light-weight reflection database
318 suitable for use in game development. It comes with a very simple runtime
319 library for loading and querying the database, requiring no external
320 dependencies (including CRT), and an additional utility library for object
321 management and serialisation.</p>
325 <!--=========================================================================-->
326 <h3>Cling C++ Interpreter</h3>
330 <p><a href="http://cern.ch/cling">Cling</a> is an interactive compiler interface
331 (aka C++ interpreter). It uses LLVM's JIT and clang; it currently supports
332 C++ and C. It has a prompt interface, runs source files, calls into shared
333 libraries, prints the value of expressions, even does runtime lookup of
334 identifiers (dynamic scopes). And it just behaves like one would expect from
339 <!--=========================================================================-->
340 <!-- FIXME: Comment out
341 <h3>Crack Programming Language</h3>
345 <a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide the
346 ease of development of a scripting language with the performance of a compiled
347 language. The language derives concepts from C++, Java and Python, incorporating
348 object-oriented programming, operator overloading and strong typing.</p>
352 <!--=========================================================================-->
353 <h3>Glasgow Haskell Compiler (GHC)</h3>
357 <p>GHC is an open source, state-of-the-art programming suite for Haskell, a
358 standard lazy functional programming language. It includes an optimizing
359 static compiler generating good code for a variety of platforms, together
360 with an interactive system for convenient, quick development.</p>
362 <p>GHC 7.0 and onwards include an LLVM code generator, supporting LLVM 2.8 and
363 later. Since LLVM 2.9, GHC now includes experimental support for the ARM
364 platform with LLVM 3.0.</p>
368 <!--=========================================================================-->
373 <p><a href="http://botwars.tk/gwscript/">gwXscript</a> is an object oriented,
374 aspect oriented programming language which can create both executables (ELF,
375 EXE) and shared libraries (DLL, SO, DYNLIB). The compiler is implemented in
376 its own language and translates scripts into LLVM-IR which can be optimized
377 and translated into native code by the LLVM framework. Source code in
378 gwScript contains definitions that expand the namespaces. So you can build
379 your project and simply 'plug out' features by removing a file. The remaining
380 project does not leave scars since you directly separate concerns by the
381 'template' feature of gwX. It is also possible to add new features to a
382 project by just adding files and without editing the original project. This
383 language is used for example to create games or content management systems
384 that should be extendable.</p>
386 <p>gwXscript is strongly typed and offers comfort with its native types string,
387 hash and array. You can easily write new libraries in gwXscript or native
388 code. gwXscript is type safe and users should not be able to crash your
389 program or execute malicious code except code that is eating CPU time.</p>
393 <!--=========================================================================-->
394 <h3>include-what-you-use</h3>
398 <p><a href="http://code.google.com/p/include-what-you-use">include-what-you-use</a>
399 is a tool to ensure that a file directly <code>#include</code>s
400 all <code>.h</code> files that provide a symbol that the file uses. It also
401 removes superfluous <code>#include</code>s from source files.</p>
405 <!--=========================================================================-->
406 <h3>LanguageKit and Pragmatic Smalltalk</h3>
410 <p><a href="http://etoileos.com/etoile/features/languagekit/">LanguageKit</a> is
411 a framework for implementing dynamic languages sharing an object model with
412 Objective-C. It provides static and JIT compilation using LLVM along with
413 its own interpreter. Pragmatic Smalltalk is a dialect of Smalltalk, built on
414 top of LanguageKit, that interfaces directly with Objective-C, sharing the
415 same object representation and message sending behaviour. These projects are
416 developed as part of the Étoié desktop environment.</p>
420 <!--=========================================================================-->
425 <p>An open source, cross-platform implementation of C# and the CLR that is
426 binary compatible with Microsoft.NET. Has an optional, dynamically-loaded
427 LLVM code generation backend in Mini, the JIT compiler.</p>
429 <p>Note that we use a Git mirror of LLVM with some patches. See:
430 https://github.com/mono/llvm</p>
434 <!--=========================================================================-->
435 <h3>Portable OpenCL (pocl)</h3>
439 <p>Portable OpenCL is an open source implementation of the OpenCL standard which
440 can be easily adapted for new targets. One of the goals of the project is
441 improving performance portability of OpenCL programs, avoiding the need for
442 target-dependent manual optimizations. A "native" target is included, which
443 allows running OpenCL kernels on the host (CPU).</p>
447 <!--=========================================================================-->
451 <p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
452 algebraic/functional programming language based on term rewriting. Programs
453 are collections of equations which are used to evaluate expressions in a
454 symbolic fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
455 programs to fast native code. Pure offers dynamic typing, eager and lazy
456 evaluation, lexical closures, a hygienic macro system (also based on term
457 rewriting), built-in list and matrix support (including list and matrix
458 comprehensions) and an easy-to-use interface to C and other programming
459 languages (including the ability to load LLVM bitcode modules, and inline C,
460 C++, Fortran and Faust code in Pure programs if the corresponding LLVM-enabled
461 compilers are installed).</p>
463 <p>Pure version 0.48 has been tested and is known to work with LLVM 3.0
464 (and continues to work with older LLVM releases >= 2.5).</p>
468 <!--=========================================================================-->
469 <h3>Renderscript</h3>
473 <p><a href="http://developer.android.com/guide/topics/renderscript/index.html">Renderscript</a>
474 is Android's advanced 3D graphics rendering and compute API. It provides a
475 portable C99-based language with extensions to facilitate common use cases
476 for enhancing graphics and thread level parallelism. The Renderscript
477 compiler frontend is based on Clang/LLVM. It emits a portable bitcode format
478 for the actual compiled script code, as well as reflects a Java interface for
479 developers to control the execution of the compiled bitcode. Executable
480 machine code is then generated from this bitcode by an LLVM backend on the
481 device. Renderscript is thus able to provide a mechanism by which Android
482 developers can improve performance of their applications while retaining
487 <!--=========================================================================-->
492 <p><a href="http://safecode.cs.illinois.edu">SAFECode</a> is a memory safe C/C++
493 compiler built using LLVM. It takes standard, unannotated C/C++ code,
494 analyzes the code to ensure that memory accesses and array indexing
495 operations are safe, and instruments the code with run-time checks when
496 safety cannot be proven statically. SAFECode can be used as a debugging aid
497 (like Valgrind) to find and repair memory safety bugs. It can also be used
498 to protect code from security attacks at run-time.</p>
502 <!--=========================================================================-->
503 <h3>The Stupid D Compiler (SDC)</h3>
507 <p><a href="https://github.com/bhelyer/SDC">The Stupid D Compiler</a> is a
508 project seeking to write a self-hosting compiler for the D programming
509 language without using the frontend of the reference compiler (DMD).</p>
513 <!--=========================================================================-->
514 <h3>TTA-based Co-design Environment (TCE)</h3>
518 <p>TCE is a toolset for designing application-specific processors (ASP) based on
519 the Transport triggered architecture (TTA). The toolset provides a complete
520 co-design flow from C/C++ programs down to synthesizable VHDL and parallel
521 program binaries. Processor customization points include the register files,
522 function units, supported operations, and the interconnection network.</p>
524 <p>TCE uses Clang and LLVM for C/C++ language support, target independent
525 optimizations and also for parts of code generation. It generates new
526 LLVM-based code generators "on the fly" for the designed TTA processors and
527 loads them in to the compiler backend as runtime libraries to avoid
528 per-target recompilation of larger parts of the compiler chain.</p>
532 <!--=========================================================================-->
533 <h3>Tart Programming Language</h3>
537 <p><a href="http://code.google.com/p/tart/">Tart</a> is a general-purpose,
538 strongly typed programming language designed for application
539 developers. Strongly inspired by Python and C#, Tart focuses on practical
540 solutions for the professional software developer, while avoiding the clutter
541 and boilerplate of legacy languages like Java and C++. Although Tart is still
542 in development, the current implementation supports many features expected of
543 a modern programming language, such as garbage collection, powerful
544 bidirectional type inference, a greatly simplified syntax for template
545 metaprogramming, closures and function literals, reflection, operator
546 overloading, explicit mutability and immutability, and much more. Tart is
547 flexible enough to accommodate a broad range of programming styles and
548 philosophies, while maintaining a strong commitment to simplicity, minimalism
549 and elegance in design.</p>
553 <!--=========================================================================-->
554 <h3>ThreadSanitizer</h3>
558 <p><a href="http://code.google.com/p/data-race-test/">ThreadSanitizer</a> is a
559 data race detector for (mostly) C and C++ code, available for Linux, Mac OS
560 and Windows. On different systems, we use binary instrumentation frameworks
561 (Valgrind and Pin) as frontends that generate the program events for the race
562 detection algorithm. On Linux, there's an option of using LLVM-based
563 compile-time instrumentation.</p>
567 <!--=========================================================================-->
568 <h3>The ZooLib C++ Cross-Platform Application Framework</h3>
572 <p><a href="http://www.zoolib.org/">ZooLib</a> is Open Source under the MIT
573 License. It provides GUI, filesystem access, TCP networking, thread-safe
574 memory management, threading and locking for Mac OS X, Classic Mac OS,
575 Microsoft Windows, POSIX operating systems with X11, BeOS, Haiku, Apple's iOS
576 and Research in Motion's BlackBerry.</p>
578 <p>My current work is to use CLang's static analyzer to improve ZooLib's code
579 quality. I also plan to set up LLVM compiles of the demo programs and test
580 programs using CLang and LLVM on all the platforms that CLang, LLVM and
581 ZooLib all support.</p>
585 <!--=========================================================================-->
590 <p><a href="http://gitorious.org/pinavm/pages/Home">PinaVM</a> is an open
591 source, <a href="http://www.systemc.org/">SystemC</a> front-end. Unlike many
592 other front-ends, PinaVM actually executes the elaboration of the
593 program analyzed using LLVM's JIT infrastructure. It later enriches the
594 bitcode with SystemC-specific information.</p>
599 <!--=========================================================================-->
601 <h3 id="icedtea">IcedTea Java Virtual Machine Implementation</h3>
605 <a href="http://icedtea.classpath.org/wiki/Main_Page">IcedTea</a> provides a
606 harness to build OpenJDK using only free software build tools and to provide
607 replacements for the not-yet free parts of OpenJDK. One of the extensions that
608 IcedTea provides is a new JIT compiler named <a
609 href="http://icedtea.classpath.org/wiki/ZeroSharkFaq">Shark</a> which uses LLVM
610 to provide native code generation without introducing processor-dependent
614 <p> OpenJDK 7 b112, IcedTea6 1.9 and IcedTea7 1.13 and later have been tested
615 and are known to work with LLVM 3.0 (and continue to work with older LLVM
616 releases >= 2.6 as well).</p>
620 <!--=========================================================================-->
622 <h3>Polly - Polyhedral optimizations for LLVM</h3>
625 <p>Polly is a project that aims to provide advanced memory access optimizations
626 to better take advantage of SIMD units, cache hierarchies, multiple cores or
627 even vector accelerators for LLVM. Built around an abstract mathematical
628 description based on Z-polyhedra, it provides the infrastructure to develop
629 advanced optimizations in LLVM and to connect complex external optimizers. In
630 its first year of existence Polly already provides an exact value-based
631 dependency analysis as well as basic SIMD and OpenMP code generation support.
632 Furthermore, Polly can use PoCC(Pluto) an advanced optimizer for data-locality
637 <!--=========================================================================-->
642 <p><a href="http://github.com/evanphx/rubinius">Rubinius</a> is an environment
643 for running Ruby code which strives to write as much of the implementation in
644 Ruby as possible. Combined with a bytecode interpreting VM, it uses LLVM to
645 optimize and compile ruby code down to machine code. Techniques such as type
646 feedback, method inlining, and deoptimization are all used to remove dynamism
647 from ruby execution and increase performance.</p>
651 <!--=========================================================================-->
654 <a name="FAUST">FAUST Real-Time Audio Signal Processing Language</a>
659 <a href="http://faust.grame.fr">FAUST</a> is a compiled language for real-time
660 audio signal processing. The name FAUST stands for Functional AUdio STream. Its
661 programming model combines two approaches: functional programming and block
662 diagram composition. In addition with the C, C++, JAVA output formats, the
663 Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7-3.0.</p>
670 <!-- *********************************************************************** -->
672 <a name="whatsnew">What's New in LLVM 3.0?</a>
674 <!-- *********************************************************************** -->
678 <p>This release includes a huge number of bug fixes, performance tweaks and
679 minor improvements. Some of the major improvements and new features are
680 listed in this section.</p>
682 <!--=========================================================================-->
684 <a name="majorfeatures">Major New Features</a>
689 <p>LLVM 3.0 includes several major new capabilities:</p>
701 <!--=========================================================================-->
703 <a name="coreimprovements">LLVM IR and Core Improvements</a>
708 <p>LLVM IR has several new features for better support of new targets and that
709 expose new optimization opportunities:</p>
711 <p>One of the biggest changes is that 3.0 has a new exception handling
712 system. The old system used LLVM intrinsics to convey the exception handling
713 information to the code generator. It worked in most cases, but not
714 all. Inlining was especially difficult to get right. Also, the intrinsics
715 could be moved away from the <code>invoke</code> instruction, making it hard
716 to recover that information.</p>
718 <p>The new EH system makes exception handling a first-class member of the IR. It
719 adds two new instructions:</p>
722 <li><a href="LangRef.html#i_landingpad"><code>landingpad</code></a> —
723 this instruction defines a landing pad basic block. It contains all of the
724 information that's needed by the code generator. It's also required to be
725 the first non-PHI instruction in the landing pad. In addition, a landing
726 pad may be jumped to only by the unwind edge of an <code>invoke</code>
729 <li><a href="LangRef.html#i_resume"><code>resume</code></a> — this
730 instruction causes the current exception to resume traveling up the
731 stack. It replaces the <code>@llvm.eh.resume</code> intrinsic.</li>
734 <p>Converting from the old EH API to the new EH API is rather simple, because a
735 lot of complexity has been removed. The two intrinsics,
736 <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code> have been
737 superceded by the <code>landingpad</code> instruction. Instead of generating
738 a call to <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code>:
740 <div class="doc_code">
742 Function *ExcIntr = Intrinsic::getDeclaration(TheModule,
743 Intrinsic::eh_exception);
744 Function *SlctrIntr = Intrinsic::getDeclaration(TheModule,
745 Intrinsic::eh_selector);
747 // The exception pointer.
748 Value *ExnPtr = Builder.CreateCall(ExcIntr, "exc_ptr");
750 std::vector<Value*> Args;
751 Args.push_back(ExnPtr);
752 Args.push_back(Builder.CreateBitCast(Personality,
753 Type::getInt8PtrTy(Context)));
755 <i>// Add selector clauses to Args.</i>
757 // The selector call.
758 Builder.CreateCall(SlctrIntr, Args, "exc_sel");
762 <p>You should instead generate a <code>landingpad</code> instruction, that
763 returns an exception object and selector value:</p>
765 <div class="doc_code">
767 LandingPadInst *LPadInst =
768 Builder.CreateLandingPad(StructType::get(Int8PtrTy, Int32Ty, NULL),
771 Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
772 Builder.CreateStore(LPadExn, getExceptionSlot());
774 Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
775 Builder.CreateStore(LPadSel, getEHSelectorSlot());
779 <p>It's now trivial to add the individual clauses to the <code>landingpad</code>
782 <div class="doc_code">
784 <i><b>// Adding a catch clause</b></i>
785 Constant *TypeInfo = getTypeInfo();
786 LPadInst->addClause(TypeInfo);
788 <i><b>// Adding a C++ catch-all</b></i>
789 LPadInst->addClause(Constant::getNullValue(Builder.getInt8PtrTy()));
791 <i><b>// Adding a cleanup</b></i>
792 LPadInst->setCleanup(true);
794 <i><b>// Adding a filter clause</b></i>
795 std::vector<Constant*> TypeInfos;
796 Constant *TypeInfo = getFilterTypeInfo();
797 TypeInfos.push_back(Builder.CreateBitCast(TypeInfo, Builder.getInt8PtrTy()));
799 ArrayType *FilterTy = ArrayType::get(Int8PtrTy, TypeInfos.size());
800 LPadInst->addClause(ConstantArray::get(FilterTy, TypeInfos));
804 <p>Converting from using the <code>@llvm.eh.resume</code> intrinsic to
805 the <code>resume</code> instruction is trivial. It takes the exception
806 pointer and exception selector values returned by
807 the <code>landingpad</code> instruction:</p>
809 <div class="doc_code">
811 Type *UnwindDataTy = StructType::get(Builder.getInt8PtrTy(),
812 Builder.getInt32Ty(), NULL);
813 Value *UnwindData = UndefValue::get(UnwindDataTy);
814 Value *ExcPtr = Builder.CreateLoad(getExceptionObjSlot());
815 Value *ExcSel = Builder.CreateLoad(getExceptionSelSlot());
816 UnwindData = Builder.CreateInsertValue(UnwindData, ExcPtr, 0, "exc_ptr");
817 UnwindData = Builder.CreateInsertValue(UnwindData, ExcSel, 1, "exc_sel");
818 Builder.CreateResume(UnwindData);
824 <!--=========================================================================-->
826 <a name="optimizer">Optimizer Improvements</a>
831 <p>In addition to a large array of minor performance tweaks and bug fixes, this
832 release includes a few major enhancements and additions to the
845 <!--=========================================================================-->
847 <a name="mc">MC Level Improvements</a>
852 <p>The LLVM Machine Code (aka MC) subsystem was created to solve a number of
853 problems in the realm of assembly, disassembly, object file format handling,
854 and a number of other related areas that CPU instruction-set level tools work
863 <p>For more information, please see
864 the <a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
865 to the LLVM MC Project Blog Post</a>.</p>
869 <!--=========================================================================-->
871 <a name="codegen">Target Independent Code Generator Improvements</a>
876 <p>We have put a significant amount of work into the code generator
877 infrastructure, which allows us to implement more aggressive algorithms and
878 make it run faster:</p>
887 <!--=========================================================================-->
889 <a name="x86">X86-32 and X86-64 Target Improvements</a>
894 <p>New features and major changes in the X86 target include:</p>
898 <li>The CRC32 intrinsics have been renamed. The intrinsics were previously
899 <code>@llvm.x86.sse42.crc32.[8|16|32]</code>
900 and <code>@llvm.x86.sse42.crc64.[8|64]</code>. They have been renamed to
901 <code>@llvm.x86.sse42.crc32.32.[8|16|32]</code> and
902 <code>@llvm.x86.sse42.crc32.64.[8|64]</code>.</li>
908 <!--=========================================================================-->
910 <a name="ARM">ARM Target Improvements</a>
915 <p>New features of the ARM target include:</p>
924 <!--=========================================================================-->
926 <a name="OtherTS">Other Target Specific Improvements</a>
929 <p>PPC32/ELF va_arg was implemented.</p>
930 <p>PPC32 initial support for .o file writing was implemented.</p>
942 <!--=========================================================================-->
944 <a name="changes">Major Changes and Removed Features</a>
949 <p>If you're already an LLVM user or developer with out-of-tree changes based on
950 LLVM 2.9, this section lists some "gotchas" that you may run into upgrading
951 from the previous release.</p>
954 <li>The <code>LLVMC</code> front end code was removed while separating
955 out language independence.</li>
956 <li>The <code>LowerSetJmp</code> pass wasn't used effectively by any
957 target and has been removed.</li>
958 <li>The old <code>TailDup</code> pass was not used in the standard pipeline
959 and was unable to update ssa form, so it has been removed.
960 <li>The syntax of volatile loads and stores in IR has been changed to
961 "<code>load volatile</code>"/"<code>store volatile</code>". The old
962 syntax ("<code>volatile load</code>"/"<code>volatile store</code>")
963 is still accepted, but is now considered deprecated.</li>
964 <li>The old atomic intrinscs (<code>llvm.memory.barrier</code> and
965 <code>llvm.atomic.*</code>) are now gone. Please use the new atomic
966 instructions, described in the <a href="Atomics.html">atomics guide</a>.
969 <h4>Windows (32-bit)</h4>
973 <li>On Win32(MinGW32 and MSVC), Windows 2000 will not be supported.
974 Windows XP or higher is required.</li>
981 <!--=========================================================================-->
983 <a name="api_changes">Internal API Changes</a>
988 <p>In addition, many APIs have changed in this release. Some of the major
989 LLVM API changes are:</p>
992 <li>The biggest and most pervasive change is that llvm::Type's are no longer
993 returned or accepted as 'const' values. Instead, just pass around
994 non-const Type's.</li>
996 <li><code>PHINode::reserveOperandSpace</code> has been removed. Instead, you
997 must specify how many operands to reserve space for when you create the
998 PHINode, by passing an extra argument
999 into <code>PHINode::Create</code>.</li>
1001 <li>PHINodes no longer store their incoming BasicBlocks as operands. Instead,
1002 the list of incoming BasicBlocks is stored separately, and can be accessed
1003 with new functions <code>PHINode::block_begin</code>
1004 and <code>PHINode::block_end</code>.</li>
1006 <li>Various functions now take an <code>ArrayRef</code> instead of either a
1007 pair of pointers (or iterators) to the beginning and end of a range, or a
1008 pointer and a length. Others now return an <code>ArrayRef</code> instead
1009 of a reference to a <code>SmallVector</code>
1010 or <code>std::vector</code>. These include:
1012 <!-- Please keep this list sorted. -->
1013 <li><code>CallInst::Create</code></li>
1014 <li><code>ComputeLinearIndex</code> (in <code>llvm/CodeGen/Analysis.h</code>)</li>
1015 <li><code>ConstantArray::get</code></li>
1016 <li><code>ConstantExpr::getExtractElement</code></li>
1017 <li><code>ConstantExpr::getGetElementPtr</code></li>
1018 <li><code>ConstantExpr::getInBoundsGetElementPtr</code></li>
1019 <li><code>ConstantExpr::getIndices</code></li>
1020 <li><code>ConstantExpr::getInsertElement</code></li>
1021 <li><code>ConstantExpr::getWithOperands</code></li>
1022 <li><code>ConstantFoldCall</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
1023 <li><code>ConstantFoldInstOperands</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
1024 <li><code>ConstantVector::get</code></li>
1025 <li><code>DIBuilder::createComplexVariable</code></li>
1026 <li><code>DIBuilder::getOrCreateArray</code></li>
1027 <li><code>ExtractValueInst::Create</code></li>
1028 <li><code>ExtractValueInst::getIndexedType</code></li>
1029 <li><code>ExtractValueInst::getIndices</code></li>
1030 <li><code>FindInsertedValue</code> (in <code>llvm/Analysis/ValueTracking.h</code>)</li>
1031 <li><code>gep_type_begin</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
1032 <li><code>gep_type_end</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
1033 <li><code>GetElementPtrInst::Create</code></li>
1034 <li><code>GetElementPtrInst::CreateInBounds</code></li>
1035 <li><code>GetElementPtrInst::getIndexedType</code></li>
1036 <li><code>InsertValueInst::Create</code></li>
1037 <li><code>InsertValueInst::getIndices</code></li>
1038 <li><code>InvokeInst::Create</code></li>
1039 <li><code>IRBuilder::CreateCall</code></li>
1040 <li><code>IRBuilder::CreateExtractValue</code></li>
1041 <li><code>IRBuilder::CreateGEP</code></li>
1042 <li><code>IRBuilder::CreateInBoundsGEP</code></li>
1043 <li><code>IRBuilder::CreateInsertValue</code></li>
1044 <li><code>IRBuilder::CreateInvoke</code></li>
1045 <li><code>MDNode::get</code></li>
1046 <li><code>MDNode::getIfExists</code></li>
1047 <li><code>MDNode::getTemporary</code></li>
1048 <li><code>MDNode::getWhenValsUnresolved</code></li>
1049 <li><code>SimplifyGEPInst</code> (in <code>llvm/Analysis/InstructionSimplify.h</code>)</li>
1050 <li><code>TargetData::getIndexedOffset</code></li>
1053 <li>All forms of <code>StringMap::getOrCreateValue</code> have been remove
1054 except for the one which takes a <code>StringRef</code>.</li>
1056 <li>The <code>LLVMBuildUnwind</code> function from the C API was removed. The
1057 LLVM <code>unwind</code> instruction has been deprecated for a long time
1058 and isn't used by the current front-ends. So this was removed during the
1059 exception handling rewrite.</li>
1061 <li>The <code>LLVMAddLowerSetJmpPass</code> function from the C API was
1062 removed because the <code>LowerSetJmp</code> pass was removed.</li>
1064 <li>The <code>DIBuilder</code> interface used by front ends to encode
1065 debugging information in the LLVM IR now expects clients to
1066 use <code>DIBuilder::finalize()</code> at the end of translation unit to
1067 complete debugging information encoding.</li>
1069 <li>The way the type system works has been
1070 rewritten: <code>PATypeHolder</code> and <code>OpaqueType</code> are gone,
1071 and all APIs deal with <code>Type*</code> instead of <code>const
1072 Type*</code>. If you need to create recursive structures, then create a
1073 named structure, and use <code>setBody()</code> when all its elements are
1074 built. Type merging and refining is gone too: named structures are not
1075 merged with other structures, even if their layout is identical. (of
1076 course anonymous structures are still uniqued by layout).</li>
1078 <li>TargetSelect.h moved to Support/ from Target/</li>
1080 <li>UpgradeIntrinsicCall no longer upgrades pre-2.9 intrinsic calls (for
1081 example <code>llvm.memset.i32</code>).</li>
1083 <li>It is mandatory to initialize all out-of-tree passes too and their dependencies now with
1084 <code>INITIALIZE_PASS{BEGIN,END,}</code>
1085 and <code>INITIALIZE_{PASS,AG}_DEPENDENCY</code>.</li>
1087 <li>The interface for MemDepResult in MemoryDependenceAnalysis has been
1088 enhanced with new return types Unknown and NonFuncLocal, in addition to
1089 the existing types Clobber, Def, and NonLocal.</li>
1096 <!-- *********************************************************************** -->
1098 <a name="knownproblems">Known Problems</a>
1100 <!-- *********************************************************************** -->
1104 <p>This section contains significant known problems with the LLVM system, listed
1105 by component. If you run into a problem, please check
1106 the <a href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
1107 there isn't already one.</p>
1109 <!-- ======================================================================= -->
1111 <a name="experimental">Experimental features included with this release</a>
1116 <p>The following components of this LLVM release are either untested, known to
1117 be broken or unreliable, or are in early development. These components
1118 should not be relied on, and bugs should not be filed against them, but they
1119 may be useful to some people. In particular, if you would like to work on
1120 one of these components, please contact us on
1121 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
1125 <li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ and
1126 XCore backends are experimental.</li>
1128 <li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets other
1129 than darwin and ELF X86 systems.</li>
1134 <!-- ======================================================================= -->
1136 <a name="x86-be">Known problems with the X86 back-end</a>
1142 <li>The X86 backend does not yet support
1143 all <a href="http://llvm.org/PR879">inline assembly that uses the X86
1144 floating point stack</a>. It supports the 'f' and 't' constraints, but
1147 <li>The X86-64 backend does not yet support the LLVM IR instruction
1148 <tt>va_arg</tt>. Currently, front-ends support variadic argument
1149 constructs on X86-64 by lowering them manually.</li>
1151 <li>Windows x64 (aka Win64) code generator has a few issues.
1153 <li>llvm-gcc cannot build the mingw-w64 runtime currently due to lack of
1154 support for the 'u' inline assembly constraint and for X87 floating
1155 point inline assembly.</li>
1157 <li>On mingw-w64, you will see unresolved symbol <tt>__chkstk</tt> due
1158 to <a href="http://llvm.org/bugs/show_bug.cgi?id=8919">Bug 8919</a>.
1160 in <a href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20110321/118499.html">r128206</a>.</li>
1162 <li>Miss-aligned MOVDQA might crash your program. It is due to
1163 <a href="http://llvm.org/bugs/show_bug.cgi?id=9483">Bug 9483</a>, lack
1164 of handling aligned internal globals.</li>
1172 <!-- ======================================================================= -->
1174 <a name="ppc-be">Known problems with the PowerPC back-end</a>
1180 <li>The PPC32/ELF support lacks PIC support.</li>
1185 <!-- ======================================================================= -->
1187 <a name="arm-be">Known problems with the ARM back-end</a>
1193 <li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
1194 processors, thumb programs can crash or produce wrong results
1195 (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
1197 <li>Compilation for ARM Linux OABI (old ABI) is supported but not fully
1203 <!-- ======================================================================= -->
1205 <a name="sparc-be">Known problems with the SPARC back-end</a>
1211 <li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
1212 support the 64-bit SPARC ABI (-m64).</li>
1217 <!-- ======================================================================= -->
1219 <a name="mips-be">Known problems with the MIPS back-end</a>
1225 <li>64-bit MIPS targets are not supported yet.</li>
1230 <!-- ======================================================================= -->
1232 <a name="alpha-be">Known problems with the Alpha back-end</a>
1238 <li>On 21164s, some rare FP arithmetic sequences which may trap do not have
1239 the appropriate nops inserted to ensure restartability.</li>
1244 <!-- ======================================================================= -->
1246 <a name="c-be">Known problems with the C back-end</a>
1251 <p>The C backend has numerous problems and is not being actively maintained.
1252 Depending on it for anything serious is not advised.</p>
1255 <li><a href="http://llvm.org/PR802">The C backend has only basic support for
1256 inline assembly code</a>.</li>
1258 <li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
1259 C++ programs</a>, preventing intermixing between C++ compiled by the CBE
1260 and C++ code compiled with <tt>llc</tt> or native compilers.</li>
1262 <li>The C backend does not support all exception handling constructs.</li>
1264 <li>The C backend does not support arbitrary precision integers.</li>
1270 <!-- ======================================================================= -->
1272 <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
1277 <p><b>LLVM 2.9 was the last release of llvm-gcc.</b></p>
1279 <p>llvm-gcc is generally very stable for the C family of languages. The only
1280 major language feature of GCC not supported by llvm-gcc is the
1281 <tt>__builtin_apply</tt> family of builtins. However, some extensions
1282 are only supported on some targets. For example, trampolines are only
1283 supported on some targets (these are used when you take the address of a
1284 nested function).</p>
1286 <p>Fortran support generally works, but there are still several unresolved bugs
1287 in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
1288 tools/gfortran component for details. Note that llvm-gcc is missing major
1289 Fortran performance work in the frontend and library that went into GCC after
1290 4.2. If you are interested in Fortran, we recommend that you consider using
1291 <a href="#dragonegg">dragonegg</a> instead.</p>
1293 <p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
1294 actively maintained. If you are interested in Ada, we recommend that you
1295 consider using <a href="#dragonegg">dragonegg</a> instead.</p>
1301 <!-- *********************************************************************** -->
1303 <a name="additionalinfo">Additional Information</a>
1305 <!-- *********************************************************************** -->
1309 <p>A wide variety of additional information is available on
1310 the <a href="http://llvm.org/">LLVM web page</a>, in particular in
1311 the <a href="http://llvm.org/docs/">documentation</a> section. The web page
1312 also contains versions of the API documentation which is up-to-date with the
1313 Subversion version of the source code. You can access versions of these
1314 documents specific to this release by going into the "<tt>llvm/doc/</tt>"
1315 directory in the LLVM tree.</p>
1317 <p>If you have any questions or comments about LLVM, please feel free to contact
1318 us via the <a href="http://llvm.org/docs/#maillist"> mailing lists</a>.</p>
1322 <!-- *********************************************************************** -->
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