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11 <h1>LLVM 3.0 Release Notes</h1>
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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, improvements in various
49 subprojects of LLVM, and some of the current users of the code.
50 All LLVM releases may be downloaded from
51 the <a href="http://llvm.org/releases/">LLVM 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 3.0 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
78 addition to this code, the LLVM Project includes other sub-projects that are
79 in development. Here we 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 3.0 time-frame, the Clang team has made many improvements:
99 <li>Greatly improved support for building C++ applications, with greater
100 stability and better diagnostics.</li>
102 <li><a href="http://clang.llvm.org/cxx_status.html">Improved support</a> for
103 the <a href="http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50372">C++
104 2011</a> standard (aka "C++'0x"), including implementations of non-static data member
105 initializers, alias templates, delegating constructors, range-based
106 for loops, and implicitly-generated move constructors and move assignment
107 operators, among others.</li>
109 <li>Implemented support for some features of the upcoming C1x standard,
110 including static assertions and generic selections.</li>
112 <li>Better detection of include and linking paths for system headers and
113 libraries, especially for Linux distributions.</li>
115 <li>Several improvements to Objective-C support, including:
118 <li><a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">
119 Automatic Reference Counting</a> (ARC) and an improved memory model
120 cleanly separating object and C memory.</li>
122 <li>A migration tool for moving manual retain/release code to ARC</li>
124 <li>Better support for data hiding, allowing instance variables to be
125 declared in implementation contexts or class extensions</li>
126 <li>Weak linking support for Objective-C classes</li>
127 <li>Improved static type checking by inferring the return type of methods
128 such as +alloc and -init.</li>
131 Some new Objective-C features require either the Mac OS X 10.7 / iOS 5
132 Objective-C runtime, or version 1.6 or later of the GNUstep Objective-C
133 runtime version.</li>
135 <li>Implemented a number of optimizations in <tt>libclang</tt>, the Clang C
136 interface, to improve the performance of code completion and the mapping
137 from source locations to abstract syntax tree nodes.</li>
139 For more details about the changes to Clang since the 2.9 release, see the
140 <a href="http://clang.llvm.org/docs/ReleaseNotes.html">Clang release notes</a>
144 <p>If Clang rejects your code but another compiler accepts it, please take a
145 look at the <a href="http://clang.llvm.org/compatibility.html">language
146 compatibility</a> guide to make sure this is not intentional or a known
151 <!--=========================================================================-->
153 <a name="dragonegg">DragonEgg: GCC front-ends, LLVM back-end</a>
157 <p><a href="http://dragonegg.llvm.org/">DragonEgg</a> is a
158 <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin</a> that replaces GCC's
159 optimizers and code generators with LLVM's. It works with gcc-4.5 or gcc-4.6,
160 targets the x86-32 and x86-64 processor families, and has been successfully
161 used on the Darwin, FreeBSD, KFreeBSD, Linux and OpenBSD platforms. It fully
162 supports Ada, C, C++ and Fortran. It has partial support for Go, Java, Obj-C
165 <p>The 3.0 release has the following notable changes:</p>
168 <li>GCC version 4.6 is now fully supported.</li>
170 <li>Patching and building GCC is no longer required: the plugin should work
171 with your system GCC (version 4.5 or 4.6; on Debian/Ubuntu systems the
172 gcc-4.5-plugin-dev or gcc-4.6-plugin-dev package is also needed).</li>
174 <li>The <tt>-fplugin-arg-dragonegg-enable-gcc-optzns</tt> option, which runs
175 GCC's optimizers as well as LLVM's, now works much better. This is the
176 option to use if you want ultimate performance! It is still experimental
177 though: it may cause the plugin to crash.</li>
179 <li>The type and constant conversion logic has been almost entirely rewritten,
180 fixing a multitude of obscure bugs.</li>
186 <!--=========================================================================-->
188 <a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
193 <p>The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
194 is a simple library that provides an implementation of the low-level
195 target-specific hooks required by code generation and other runtime
196 components. For example, when compiling for a 32-bit target, converting a
197 double to a 64-bit unsigned integer is compiled into a runtime call to the
198 "__fixunsdfdi" function. The compiler-rt library provides highly optimized
199 implementations of this and other low-level routines (some are 3x faster than
200 the equivalent libgcc routines).</p>
202 <p>In the LLVM 3.0 timeframe, the target specific ARM code has converted to
203 "unified" assembly syntax, and several new functions have been added to the
208 <!--=========================================================================-->
210 <a name="lldb">LLDB: Low Level Debugger</a>
215 <p>LLDB is a ground-up implementation of a command line debugger, as well as a
216 debugger API that can be used from other applications. LLDB makes use of the
217 Clang parser to provide high-fidelity expression parsing (particularly for
218 C++) and uses the LLVM JIT for target support.</p>
220 <p>LLDB has advanced by leaps and bounds in the 3.0 timeframe. It is
221 dramatically more stable and useful, and includes both a
222 new <a href="http://lldb.llvm.org/tutorial.html">tutorial</a> and
223 a <a href="http://lldb.llvm.org/lldb-gdb.html">side-by-side comparison with
228 <!--=========================================================================-->
230 <a name="libc++">libc++: C++ Standard Library</a>
235 <p>Like compiler_rt, libc++ is now <a href="DeveloperPolicy.html#license">dual
236 licensed</a> under the MIT and UIUC license, allowing it to be used more
239 <p>Libc++ has been ported to FreeBSD and imported into the base system. It is
240 planned to be the default STL implementation for FreeBSD 10.</p>
244 <!--=========================================================================-->
246 <a name="vmkit">VMKit</a>
251 <p>The <a href="http://vmkit.llvm.org/">VMKit project</a> is an
252 implementation of a Java Virtual Machine (Java VM or JVM) that uses LLVM for
253 static and just-in-time compilation.
255 <p>In the LLVM 3.0 time-frame, VMKit has had significant improvements on both
256 runtime and startup performance:</p>
259 <li>Precompilation: by compiling ahead of time a small subset of Java's core
260 library, the startup performance have been highly optimized to the point that
261 running a 'Hello World' program takes less than 30 milliseconds.</li>
263 <li>Customization: by customizing virtual methods for individual classes,
264 the VM can statically determine the target of a virtual call, and decide to
267 <li>Inlining: the VM does more inlining than it did before, by allowing more
268 bytecode instructions to be inlined, and thanks to customization. It also
269 inlines GC barriers, and object allocations.</li>
271 <li>New exception model: the generated code for a method that does not do
272 any try/catch is not penalized anymore by the eventuality of calling a
273 method that throws an exception. Instead, the method that throws the
274 exception jumps directly to the method that could catch it.</li>
280 <!--=========================================================================-->
282 <a name="LLBrowse">LLBrowse: IR Browser</a>
287 <p><a href="http://llvm.org/svn/llvm-project/llbrowse/trunk/doc/LLBrowse.html">
288 LLBrowse</a> is an interactive viewer for LLVM modules. It can load any LLVM
289 module and displays its contents as an expandable tree view, facilitating an
290 easy way to inspect types, functions, global variables, or metadata nodes. It
291 is fully cross-platform, being based on the popular wxWidgets GUI
297 <!--=========================================================================-->
300 <a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
305 <a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
306 programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
307 through the application and records state transitions that lead to fault
308 states. This allows it to construct testcases that lead to faults and can even
309 be used to verify some algorithms.
317 <!-- *********************************************************************** -->
319 <a name="externalproj">External Open Source Projects Using LLVM 3.0</a>
321 <!-- *********************************************************************** -->
325 <p>An exciting aspect of LLVM is that it is used as an enabling technology for
326 a lot of other language and tools projects. This section lists some of the
327 projects that have already been updated to work with LLVM 3.0.</p>
329 <!--=========================================================================-->
330 <h3>AddressSanitizer</h3>
334 <p><a href="http://code.google.com/p/address-sanitizer/">AddressSanitizer</a>
335 uses compiler instrumentation and a specialized malloc library to find C/C++
336 bugs such as use-after-free and out-of-bound accesses to heap, stack, and
337 globals. The key feature of the tool is speed: the average slowdown
338 introduced by AddressSanitizer is less than 2x.</p>
342 <!--=========================================================================-->
347 <p><a href="http://www.clamav.net">Clam AntiVirus</a> is an open source (GPL)
348 anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail
351 <p>Since version 0.96 it
352 has <a href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode
353 signatures</a> that allow writing detections for complex malware.
354 It uses LLVM's JIT to speed up the execution of bytecode on X86, X86-64,
355 PPC32/64, falling back to its own interpreter otherwise. The git version was
356 updated to work with LLVM 3.0.</p>
360 <!--=========================================================================-->
361 <h3>clang_complete for VIM</h3>
365 <p><a href="https://github.com/Rip-Rip/clang_complete">clang_complete</a> is a
366 VIM plugin, that provides accurate C/C++ autocompletion using the clang front
367 end. The development version of clang complete, can directly use libclang
368 which can maintain a cache to speed up auto completion.</p>
372 <!--=========================================================================-->
377 <p><a href="https://bitbucket.org/dwilliamson/clreflect">clReflect</a> is a C++
378 parser that uses clang/LLVM to derive a light-weight reflection database
379 suitable for use in game development. It comes with a very simple runtime
380 library for loading and querying the database, requiring no external
381 dependencies (including CRT), and an additional utility library for object
382 management and serialisation.</p>
386 <!--=========================================================================-->
387 <h3>Cling C++ Interpreter</h3>
391 <p><a href="http://cern.ch/cling">Cling</a> is an interactive compiler interface
392 (aka C++ interpreter). It supports C++ and C, and uses LLVM's JIT and the
393 Clang parser. It has a prompt interface, runs source files, calls into shared
394 libraries, prints the value of expressions, even does runtime lookup of
395 identifiers (dynamic scopes). And it just behaves like one would expect from
400 <!--=========================================================================-->
401 <h3>Crack Programming Language</h3>
405 <p><a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide
406 the ease of development of a scripting language with the performance of a
407 compiled language. The language derives concepts from C++, Java and Python,
408 incorporating object-oriented programming, operator overloading and strong
413 <!--=========================================================================-->
418 <p><a href="http://eerolanguage.org/">Eero</a> is a fully
419 header-and-binary-compatible dialect of Objective-C 2.0, implemented with a
420 patched version of the Clang/LLVM compiler. It features a streamlined syntax,
421 Python-like indentation, and new operators, for improved readability and
422 reduced code clutter. It also has new features such as limited forms of
423 operator overloading and namespaces, and strict (type-and-operator-safe)
424 enumerations. It is inspired by languages such as Smalltalk, Python, and
429 <!--=========================================================================-->
430 <h3>FAUST Real-Time Audio Signal Processing Language</h3>
434 <p><a href="http://faust.grame.fr/">FAUST</a> is a compiled language for
435 real-time audio signal processing. The name FAUST stands for Functional
436 AUdio STream. Its programming model combines two approaches: functional
437 programming and block diagram composition. In addition with the C, C++, Java
438 output formats, the Faust compiler can now generate LLVM bitcode, and works
444 <!--=========================================================================-->
445 <h3>Glasgow Haskell Compiler (GHC)</h3>
449 <p>GHC is an open source, state-of-the-art programming suite for Haskell, a
450 standard lazy functional programming language. It includes an optimizing
451 static compiler generating good code for a variety of platforms, together
452 with an interactive system for convenient, quick development.</p>
454 <p>GHC 7.0 and onwards include an LLVM code generator, supporting LLVM 2.8 and
455 later. Since LLVM 2.9, GHC now includes experimental support for the ARM
456 platform with LLVM 3.0.</p>
460 <!--=========================================================================-->
465 <p><a href="http://botwars.tk/gwscript/">gwXscript</a> is an object oriented,
466 aspect oriented programming language which can create both executables (ELF,
467 EXE) and shared libraries (DLL, SO, DYNLIB). The compiler is implemented in
468 its own language and translates scripts into LLVM-IR which can be optimized
469 and translated into native code by the LLVM framework. Source code in
470 gwScript contains definitions that expand the namespaces. So you can build
471 your project and simply 'plug out' features by removing a file. The remaining
472 project does not leave scars since you directly separate concerns by the
473 'template' feature of gwX. It is also possible to add new features to a
474 project by just adding files and without editing the original project. This
475 language is used for example to create games or content management systems
476 that should be extendable.</p>
478 <p>gwXscript is strongly typed and offers comfort with its native types string,
479 hash and array. You can easily write new libraries in gwXscript or native
480 code. gwXscript is type safe and users should not be able to crash your
481 program or execute malicious code except code that is eating CPU time.</p>
485 <!--=========================================================================-->
486 <h3>include-what-you-use</h3>
490 <p><a href="http://code.google.com/p/include-what-you-use">include-what-you-use</a>
491 is a tool to ensure that a file directly <code>#include</code>s
492 all <code>.h</code> files that provide a symbol that the file uses. It also
493 removes superfluous <code>#include</code>s from source files.</p>
497 <!--=========================================================================-->
498 <h3>ispc: The Intel SPMD Program Compiler</h3>
502 <p><a href="http://ispc.github.com">ispc</a> is a compiler for "single program,
503 multiple data" (SPMD) programs. It compiles a C-based SPMD programming
504 language to run on the SIMD units of CPUs; it often delivers 5-6x speedups on
505 a single core of a CPU with an 8-wide SIMD unit compared to serial code,
506 while still providing a clean and easy-to-understand programming model. For
507 an introduction to the language and its performance,
508 see <a href="http://ispc.github.com/example.html">the walkthrough</a> of a short
509 example program. ispc is licensed under the BSD license.</p>
513 <!--=========================================================================-->
514 <h3>The Julia Programming Language</h3>
518 <p><a href="http://github.com/JuliaLang/julia">Julia</a> is a high-level,
519 high-performance dynamic language for technical
520 computing. It provides a sophisticated compiler, distributed parallel
521 execution, numerical accuracy, and an extensive mathematical function
522 library. The compiler uses type inference to generate fast code
523 without any type declarations, and uses LLVM's optimization passes and
524 JIT compiler. The language is designed around multiple dispatch,
525 giving programs a large degree of flexibility. It is ready for use on many
526 kinds of problems.</p>
529 <!--=========================================================================-->
530 <h3>LanguageKit and Pragmatic Smalltalk</h3>
534 <p><a href="http://etoileos.com/etoile/features/languagekit/">LanguageKit</a> is
535 a framework for implementing dynamic languages sharing an object model with
536 Objective-C. It provides static and JIT compilation using LLVM along with
537 its own interpreter. Pragmatic Smalltalk is a dialect of Smalltalk, built on
538 top of LanguageKit, that interfaces directly with Objective-C, sharing the
539 same object representation and message sending behaviour. These projects are
540 developed as part of the Étoilé desktop environment.</p>
544 <!--=========================================================================-->
549 <p><a href="http://lua-av.mat.ucsb.edu/blog/">LuaAV</a> is a real-time
550 audiovisual scripting environment based around the Lua language and a
551 collection of libraries for sound, graphics, and other media protocols. LuaAV
552 uses LLVM and Clang to JIT compile efficient user-defined audio synthesis
553 routines specified in a declarative syntax.</p>
557 <!--=========================================================================-->
562 <p>An open source, cross-platform implementation of C# and the CLR that is
563 binary compatible with Microsoft.NET. Has an optional, dynamically-loaded
564 LLVM code generation backend in Mini, the JIT compiler.</p>
566 <p>Note that we use a Git mirror of LLVM <a
567 href="https://github.com/mono/llvm">with some patches</a>.</p>
571 <!--=========================================================================-->
576 <p><a href="http://polly.grosser.es">Polly</a> is an advanced data-locality
577 optimizer and automatic parallelizer. It uses an advanced, mathematical
578 model to calculate detailed data dependency information which it uses to
579 optimize the loop structure of a program. Polly can speed up sequential code
580 by improving memory locality and consequently the cache use. Furthermore,
581 Polly is able to expose different kind of parallelism which it exploits by
582 introducing (basic) OpenMP and SIMD code. A mid-term goal of Polly is to
583 automatically create optimized GPU code.</p>
587 <!--=========================================================================-->
588 <h3>Portable OpenCL (pocl)</h3>
592 <p>Portable OpenCL is an open source implementation of the OpenCL standard which
593 can be easily adapted for new targets. One of the goals of the project is
594 improving performance portability of OpenCL programs, avoiding the need for
595 target-dependent manual optimizations. A "native" target is included, which
596 allows running OpenCL kernels on the host (CPU).</p>
600 <!--=========================================================================-->
604 <p><a href="http://pure-lang.googlecode.com/">Pure</a> is an
605 algebraic/functional programming language based on term rewriting. Programs
606 are collections of equations which are used to evaluate expressions in a
607 symbolic fashion. The interpreter uses LLVM as a backend to JIT-compile Pure
608 programs to fast native code. Pure offers dynamic typing, eager and lazy
609 evaluation, lexical closures, a hygienic macro system (also based on term
610 rewriting), built-in list and matrix support (including list and matrix
611 comprehensions) and an easy-to-use interface to C and other programming
612 languages (including the ability to load LLVM bitcode modules, and inline C,
613 C++, Fortran and Faust code in Pure programs if the corresponding LLVM-enabled
614 compilers are installed).</p>
616 <p>Pure version 0.48 has been tested and is known to work with LLVM 3.0
617 (and continues to work with older LLVM releases >= 2.5).</p>
621 <!--=========================================================================-->
622 <h3>Renderscript</h3>
626 <p><a href="http://developer.android.com/guide/topics/renderscript/index.html">Renderscript</a>
627 is Android's advanced 3D graphics rendering and compute API. It provides a
628 portable C99-based language with extensions to facilitate common use cases
629 for enhancing graphics and thread level parallelism. The Renderscript
630 compiler frontend is based on Clang/LLVM. It emits a portable bitcode format
631 for the actual compiled script code, as well as reflects a Java interface for
632 developers to control the execution of the compiled bitcode. Executable
633 machine code is then generated from this bitcode by an LLVM backend on the
634 device. Renderscript is thus able to provide a mechanism by which Android
635 developers can improve performance of their applications while retaining
640 <!--=========================================================================-->
645 <p><a href="http://safecode.cs.illinois.edu">SAFECode</a> is a memory safe C/C++
646 compiler built using LLVM. It takes standard, unannotated C/C++ code,
647 analyzes the code to ensure that memory accesses and array indexing
648 operations are safe, and instruments the code with run-time checks when
649 safety cannot be proven statically. SAFECode can be used as a debugging aid
650 (like Valgrind) to find and repair memory safety bugs. It can also be used
651 to protect code from security attacks at run-time.</p>
655 <!--=========================================================================-->
656 <h3>The Stupid D Compiler (SDC)</h3>
660 <p><a href="https://github.com/bhelyer/SDC">The Stupid D Compiler</a> is a
661 project seeking to write a self-hosting compiler for the D programming
662 language without using the frontend of the reference compiler (DMD).</p>
666 <!--=========================================================================-->
667 <h3>TTA-based Co-design Environment (TCE)</h3>
671 <p>TCE is a toolset for designing application-specific processors (ASP) based on
672 the Transport triggered architecture (TTA). The toolset provides a complete
673 co-design flow from C/C++ programs down to synthesizable VHDL and parallel
674 program binaries. Processor customization points include the register files,
675 function units, supported operations, and the interconnection network.</p>
677 <p>TCE uses Clang and LLVM for C/C++ language support, target independent
678 optimizations and also for parts of code generation. It generates new
679 LLVM-based code generators "on the fly" for the designed TTA processors and
680 loads them in to the compiler backend as runtime libraries to avoid
681 per-target recompilation of larger parts of the compiler chain.</p>
685 <!--=========================================================================-->
686 <h3>Tart Programming Language</h3>
690 <p><a href="http://code.google.com/p/tart/">Tart</a> is a general-purpose,
691 strongly typed programming language designed for application
692 developers. Strongly inspired by Python and C#, Tart focuses on practical
693 solutions for the professional software developer, while avoiding the clutter
694 and boilerplate of legacy languages like Java and C++. Although Tart is still
695 in development, the current implementation supports many features expected of
696 a modern programming language, such as garbage collection, powerful
697 bidirectional type inference, a greatly simplified syntax for template
698 metaprogramming, closures and function literals, reflection, operator
699 overloading, explicit mutability and immutability, and much more. Tart is
700 flexible enough to accommodate a broad range of programming styles and
701 philosophies, while maintaining a strong commitment to simplicity, minimalism
702 and elegance in design.</p>
706 <!--=========================================================================-->
707 <h3>ThreadSanitizer</h3>
711 <p><a href="http://code.google.com/p/data-race-test/">ThreadSanitizer</a> is a
712 data race detector for (mostly) C and C++ code, available for Linux, Mac OS
713 and Windows. On different systems, we use binary instrumentation frameworks
714 (Valgrind and Pin) as frontends that generate the program events for the race
715 detection algorithm. On Linux, there's an option of using LLVM-based
716 compile-time instrumentation.</p>
722 <!-- *********************************************************************** -->
724 <a name="whatsnew">What's New in LLVM 3.0?</a>
726 <!-- *********************************************************************** -->
730 <p>This release includes a huge number of bug fixes, performance tweaks and
731 minor improvements. Some of the major improvements and new features are
732 listed in this section.</p>
734 <!--=========================================================================-->
736 <a name="majorfeatures">Major New Features</a>
741 <!-- Features that need text if they're finished for 3.1:
745 loop dependence analysis
746 CorrelatedValuePropagation
747 lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.1.
748 Integrated assembler on by default for arm/thumb?
753 Analysis/RegionInfo.h + Dom Frontiers
754 SparseBitVector: used in LiveVar.
755 llvm/lib/Archive - replace with lib object?
758 <p>LLVM 3.0 includes several major changes and big features:</p>
761 <li>llvm-gcc is no longer supported, and not included in the release. We
762 recommend switching to <a
763 href="http://clang.llvm.org/">Clang</a> or <a
764 href="http://dragonegg.llvm.org/">DragonEgg</a>.</li>
766 <li>The linear scan register allocator has been replaced with a new "greedy"
767 register allocator, enabling live range splitting and many other
768 optimizations that lead to better code quality. Please see its <a
769 href="http://blog.llvm.org/2011/09/greedy-register-allocation-in-llvm-30.html">blog post</a> or its talk at the <a
770 href="http://llvm.org/devmtg/2011-11/">Developer Meeting</a>
771 for more information.</li>
772 <li>LLVM IR now includes full support for <a href="Atomics.html">atomics
773 memory operations</a> intended to support the C++'11 and C'1x memory models.
774 This includes <a href="LangRef.html#memoryops">atomic load and store,
775 compare and exchange, and read/modify/write instructions</a> as well as a
776 full set of <a href="LangRef.html#ordering">memory ordering constraints</a>.
777 Please see the <a href="Atomics.html">Atomics Guide</a> for more
780 <li>The LLVM IR exception handling representation has been redesigned and
781 reimplemented, making it more elegant, fixing a huge number of bugs, and
782 enabling inlining and other optimizations. Please see its <a href=
783 "http://blog.llvm.org/2011/11/llvm-30-exception-handling-redesign.html">blog
784 post</a> and the <a href="ExceptionHandling.html">Exception Handling
785 documentation</a> for more information.</li>
786 <li>The LLVM IR Type system has been redesigned and reimplemented, making it
787 faster and solving some long-standing problems.
789 href="http://blog.llvm.org/2011/11/llvm-30-type-system-rewrite.html">blog
790 post</a> for more information.</li>
792 <li>The MIPS backend has made major leaps in this release, going from an
793 experimental target to being virtually production quality and supporting a
794 wide variety of MIPS subtargets. See the <a href="#MIPS">MIPS section</a>
795 below for more information.</li>
797 <li>The optimizer and code generator now supports gprof and gcov-style coverage
798 and profiling information, and includes a new llvm-cov tool (but also works
799 with gcov). Clang exposes coverage and profiling through GCC-compatible
800 command line options.</li>
806 <!--=========================================================================-->
808 <a name="coreimprovements">LLVM IR and Core Improvements</a>
813 <p>LLVM IR has several new features for better support of new targets and that
814 expose new optimization opportunities:</p>
817 <li><a href="Atomics.html">Atomic memory accesses and memory ordering</a> are
818 now directly expressible in the IR.</li>
819 <li>A new <a href="LangRef.html#int_fma">llvm.fma intrinsic</a> directly
820 represents floating point multiply accumulate operations without an
821 intermediate rounding stage.</li>
822 <li>A new llvm.expect intrinsic (XXX not documented in langref) allows a
823 frontend to express expected control flow (and the __builtin_expect builtin
825 <li>The <a href="LangRef.html#int_prefetch">llvm.prefetch intrinsic</a> now
826 takes a 4th argument that specifies whether the prefetch happens from the
827 icache or dcache.</li>
828 <li>The new <a href="LangRef.html#uwtable">uwtable function attribute</a>
829 allows a frontend to control emission of unwind tables.</li>
830 <li>The new <a href="LangRef.html#fnattrs">nonlazybind function
831 attribute</a> allow optimization of Global Offset Table (GOT) accesses.</li>
832 <li>The new <a href="LangRef.html#returns_twice">returns_twice attribute</a>
833 allows better modeling of functions like setjmp.</li>
834 <li>The <a href="LangRef.html#datalayout">target datalayout</a> string can now
835 encode the natural alignment of the target's stack for better optimization.
840 <!--=========================================================================-->
842 <a name="optimizer">Optimizer Improvements</a>
847 <p>In addition to many minor performance tweaks and bug fixes, this
848 release includes a few major enhancements and additions to the
852 <li>The pass manager now has an extension API that allows front-ends and plugins
853 to insert their own optimizations in the well-known places in the standard
854 pass optimization pipeline.</li>
856 <li>Information about <a href="BranchWeightMetadata.html">branch probability</a>
857 and basic block frequency is now available within LLVM, based on a
858 combination of static branch prediction heuristics and
859 <code>__builtin_expect</code> calls. That information is currently used for
860 register spill placement and if-conversion, with additional optimizations
861 planned for future releases. The same framework is intended for eventual
862 use with profile-guided optimization.</li>
864 <li>The "-indvars" induction variable simplification pass only modifies
865 induction variables when profitable. Sign and zero extension
866 elimination, linear function test replacement, loop unrolling, and
867 other simplifications that require induction variable analysis have
868 been generalized so they no longer require loops to be rewritten into
869 canonical form prior to optimization. This new design
870 preserves more IR level information, avoids undoing earlier loop
871 optimizations (particularly hand-optimized loops), and no longer
872 requires the code generator to reconstruct loops into an optimal form -
873 an intractable problem.</li>
875 <li>LLVM now includes a pass to optimize retain/release calls for the
876 <a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">Automatic
877 Reference Counting</a> (ARC) Objective-C language feature (in
878 lib/Transforms/Scalar/ObjCARC.cpp). It is a decent example of implementing
879 a source-language-specific optimization in LLVM.</li>
885 <!--=========================================================================-->
887 <a name="mc">MC Level Improvements</a>
892 <p>The LLVM Machine Code (aka MC) subsystem was created to solve a number of
893 problems in the realm of assembly, disassembly, object file format handling,
894 and a number of other related areas that CPU instruction-set level tools work
895 in. For more information, please see
896 the <a href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro
897 to the LLVM MC Project Blog Post</a>.</p>
900 <li>The MC layer has undergone significant refactoring to eliminate layering
901 violations that caused it to pull in the LLVM compiler backend code.</li>
902 <li>The ELF object file writers are much more full featured.</li>
903 <li>The integrated assembler now supports #line directives.</li>
904 <li>An early implementation of a JIT built on top of the MC framework (known
905 as MC-JIT) has been implemented and will eventually replace the old JIT.
906 It emits object files direct to memory and uses a runtime dynamic linker to
907 resolve references and drive lazy compilation. The MC-JIT enables much
908 greater code reuse between the JIT and the static compiler and provides
909 better integration with the platform ABI as a result.
911 <li>The assembly printer now makes uses of assemblers instruction aliases
912 (InstAliases) to print simplified mneumonics when possible.</li>
913 <li>TableGen can now autogenerate MC expansion logic for pseudo
914 instructions that expand to multiple MC instructions (through the
915 PseudoInstExpansion class).</li>
916 <li>A new llvm-dwarfdump tool provides a start of a drop-in
917 replacement for the corresponding tool that use LLVM libraries. As part of
918 this, LLVM has the beginnings of a dwarf parsing library.</li>
919 <li>llvm-objdump has more output including, symbol by symbol disassembly,
920 inline relocations, section headers, symbol tables, and section contents.
921 Support for archive files has also been added.</li>
922 <li>llvm-nm has gained support for archives of binary files.</li>
923 <li>llvm-size has been added. This tool prints out section sizes.</li>
928 <!--=========================================================================-->
930 <a name="codegen">Target Independent Code Generator Improvements</a>
935 <p>We have put a significant amount of work into the code generator
936 infrastructure, which allows us to implement more aggressive algorithms and
937 make it run faster:</p>
940 <li>LLVM can now produce code that works with libgcc
941 to <a href="SegmentedStacks.html">dynamically allocate stack
942 segments</a>, as opposed to allocating a worst-case chunk of
943 virtual memory for each thread.</li>
944 <li>LLVM generates substantially better code for indirect gotos due to a new
945 tail duplication pass, which can be a substantial performance win for
946 interpreter loops that use them.</li>
947 <li>Exception handling and debug frame information is now emitted with CFI
948 directives. This lets the assembler produce more compact info as it knows
949 the final offsets, yielding <a href="http://blog.mozilla.com/respindola/2011/05/12/cfi-directives/">much smaller executables</a> for some C++ applications.
950 If the system assembler doesn't support it, MC exands the directives when
951 the integrated assembler is not used.
954 <li>The code generator now supports vector "select" operations on vector
955 comparisons, turning them into various optimized code sequences (e.g.
956 using the SSE4/AVX "blend" instructions).</li>
957 <li>The SSE execution domain fix pass and the ARM NEON move fix pass have been
958 merged to a target independent execution dependency fix pass. This pass is
959 used to select alternative equivalent opcodes in a way that minimizes
960 execution domain crossings. Closely connected instructions are moved to
961 the same execution domain when possible. Targets can override the
962 <code>getExecutionDomain</code> and <code>setExecutionDomain</code> hooks
963 to use the pass.</li>
967 <!--=========================================================================-->
969 <a name="x86">X86-32 and X86-64 Target Improvements</a>
974 <p>New features and major changes in the X86 target include:</p>
977 <li>The X86 backend, assembler and disassembler now have full support for AVX 1.
978 To enable it pass <code>-mavx</code> to the compiler. AVX2 implementation is
979 underway on mainline.</li>
980 <li>The integrated assembler and disassembler now support a broad range of new
981 instructions including Atom, Ivy Bridge, <a
982 href="http://en.wikipedia.org/wiki/SSE4a">SSE4a/BMI</a> instructions, <a
983 href="http://en.wikipedia.org/wiki/RdRand">rdrand</a> and many others.</li>
984 <li>The X86 backend now fully supports the <a href="http://llvm.org/PR879">X87
985 floating point stack inline assembly constraints</a>.</li>
986 <li>The integrated assembler now supports the <tt>.code32</tt> and
987 <tt>.code64</tt> directives to switch between 32-bit and 64-bit
989 <li>The X86 backend now synthesizes horizontal add/sub instructions from generic
990 vector code when the appropriate instructions are enabled.</li>
991 <li>The X86-64 backend generates smaller and faster code at -O0 due to
992 improvements in fast instruction selection.</li>
993 <li><a href="http://code.google.com/p/nativeclient/">Native Client</a>
994 subtarget support has been added.</li>
996 <li>The CRC32 intrinsics have been renamed. The intrinsics were previously
997 <code>@llvm.x86.sse42.crc32.[8|16|32]</code>
998 and <code>@llvm.x86.sse42.crc64.[8|64]</code>. They have been renamed to
999 <code>@llvm.x86.sse42.crc32.32.[8|16|32]</code> and
1000 <code>@llvm.x86.sse42.crc32.64.[8|64]</code>.</li>
1005 <!--=========================================================================-->
1007 <a name="ARM">ARM Target Improvements</a>
1012 <p>New features of the ARM target include:</p>
1015 <li>The ARM backend generates much faster code for Cortex-A9 chips.</li>
1016 <li>The ARM backend has improved support for Cortex-M series processors.</li>
1017 <li>The ARM inline assembly constraints have been implemented and are now fully
1019 <li>NEON code produced by Clang often runs much faster due to improvements in
1020 the Scalar Replacement of Aggregates pass.</li>
1021 <li>The old ARM disassembler is replaced with a new one based on autogenerated
1022 encoding information from ARM .td files.</li>
1023 <li>The integrated assembler has made major leaps forward, but is still beta quality in LLVM 3.0.</li>
1028 <!--=========================================================================-->
1030 <a name="MIPS">MIPS Target Improvements</a>
1035 <p>This release has seen major new work on just about every aspect of the MIPS
1036 backend. Some of the major new features include:</p>
1039 <li>Most MIPS32r1 and r2 instructions are now supported.</li>
1040 <li>LE/BE MIPS32r1/r2 has been tested extensively.</li>
1041 <li>O32 ABI has been fully tested.</li>
1042 <li>MIPS backend has migrated to using the MC infrastructure for assembly printing. Initial support for direct object code emission has been implemented too.</li>
1043 <li>Delay slot filler has been updated. Now it tries to fill delay slots with useful instructions instead of always filling them with NOPs.</li>
1044 <li>Support for old-style JIT is complete.</li>
1045 <li>Support for old architectures (MIPS1 and MIPS2) has been removed.</li>
1046 <li>Initial support for MIPS64 has been added.</li>
1050 <!--=========================================================================-->
1052 <a name="PTX">PTX Target Improvements</a>
1058 The PTX back-end is still experimental, but is fairly usable for compute kernels
1059 in LLVM 3.0. Most scalar arithmetic is implemented, as well as intrinsics to
1060 access the special PTX registers and sync instructions. The major missing
1061 pieces are texture/sampler support and some vector operations.</p>
1063 <p>That said, the backend is already being used for domain-specific languages
1064 and can be used by Clang to
1065 <a href="http://clang.llvm.org/docs/ReleaseNotes.html#opencl">compile OpenCL
1066 C code</a> into PTX.</p>
1070 <!--=========================================================================-->
1072 <a name="OtherTS">Other Target Specific Improvements</a>
1078 <li>Many PowerPC improvements have been implemented for ELF targets, including
1079 support for varargs and initial support for direct .o file emission.</li>
1081 <li>MicroBlaze scheduling itineraries were added that model the
1082 3-stage and the 5-stage pipeline architectures. The 3-stage
1083 pipeline model can be selected with <code>-mcpu=mblaze3</code>
1084 and the 5-stage pipeline model can be selected with
1085 <code>-mcpu=mblaze5</code>.</li>
1091 <!--=========================================================================-->
1093 <a name="changes">Major Changes and Removed Features</a>
1098 <p>If you're already an LLVM user or developer with out-of-tree changes based on
1099 LLVM 2.9, this section lists some "gotchas" that you may run into upgrading
1100 from the previous release.</p>
1103 <li>LLVM 3.0 removes support for reading LLVM 2.8 and earlier files, and LLVM
1104 3.1 will eliminate support for reading LLVM 2.9 files. Going forward, we
1105 aim for all future versions of LLVM to read bitcode files and .ll files
1106 produced by LLVM 3.0.</li>
1107 <li>Tablegen has been split into a library, allowing the clang tblgen pieces
1108 to now live in the clang tree. The llvm version has been renamed to
1109 llvm-tblgen instead of tblgen.</li>
1110 <li>The <code>LLVMC</code> meta compiler driver was removed.</li>
1111 <li>The unused PostOrder Dominator Frontiers and LowerSetJmp passes were removed.</li>
1114 <li>The old <code>TailDup</code> pass was not used in the standard pipeline
1115 and was unable to update ssa form, so it has been removed.
1116 <li>The syntax of volatile loads and stores in IR has been changed to
1117 "<code>load volatile</code>"/"<code>store volatile</code>". The old
1118 syntax ("<code>volatile load</code>"/"<code>volatile store</code>")
1119 is still accepted, but is now considered deprecated and will be removed in
1121 <li>llvm-gcc's frontend tests have been removed from llvm/test/Frontend*, sunk
1122 into the clang and dragonegg testsuites.</li>
1123 <li>The old atomic intrinsics (<code>llvm.memory.barrier</code> and
1124 <code>llvm.atomic.*</code>) are now gone. Please use the new atomic
1125 instructions, described in the <a href="Atomics.html">atomics guide</a>.
1126 <li>LLVM's configure script doesn't depend on llvm-gcc anymore, eliminating a
1127 strange circular dependence between projects.</li>
1130 <h4>Windows (32-bit)</h4>
1134 <li>On Win32(MinGW32 and MSVC), Windows 2000 will not be supported.
1135 Windows XP or higher is required.</li>
1142 <!--=========================================================================-->
1144 <a name="api_changes">Internal API Changes</a>
1149 <p>In addition, many APIs have changed in this release. Some of the major
1150 LLVM API changes are:</p>
1153 <li>The biggest and most pervasive change is that the type system has been
1154 rewritten: <code>PATypeHolder</code> and <code>OpaqueType</code> are gone,
1155 and all APIs deal with <code>Type*</code> instead of <code>const
1156 Type*</code>. If you need to create recursive structures, then create a
1157 named structure, and use <code>setBody()</code> when all its elements are
1158 built. Type merging and refining is gone too: named structures are not
1159 merged with other structures, even if their layout is identical. (of
1160 course anonymous structures are still uniqued by layout).</li>
1162 <li><code>PHINode::reserveOperandSpace</code> has been removed. Instead, you
1163 must specify how many operands to reserve space for when you create the
1164 PHINode, by passing an extra argument
1165 into <code>PHINode::Create</code>.</li>
1167 <li>PHINodes no longer store their incoming BasicBlocks as operands. Instead,
1168 the list of incoming BasicBlocks is stored separately, and can be accessed
1169 with new functions <code>PHINode::block_begin</code>
1170 and <code>PHINode::block_end</code>.</li>
1172 <li>Various functions now take an <code>ArrayRef</code> instead of either a
1173 pair of pointers (or iterators) to the beginning and end of a range, or a
1174 pointer and a length. Others now return an <code>ArrayRef</code> instead
1175 of a reference to a <code>SmallVector</code>
1176 or <code>std::vector</code>. These include:
1178 <!-- Please keep this list sorted. -->
1179 <li><code>CallInst::Create</code></li>
1180 <li><code>ComputeLinearIndex</code> (in <code>llvm/CodeGen/Analysis.h</code>)</li>
1181 <li><code>ConstantArray::get</code></li>
1182 <li><code>ConstantExpr::getExtractElement</code></li>
1183 <li><code>ConstantExpr::getGetElementPtr</code></li>
1184 <li><code>ConstantExpr::getInBoundsGetElementPtr</code></li>
1185 <li><code>ConstantExpr::getIndices</code></li>
1186 <li><code>ConstantExpr::getInsertElement</code></li>
1187 <li><code>ConstantExpr::getWithOperands</code></li>
1188 <li><code>ConstantFoldCall</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
1189 <li><code>ConstantFoldInstOperands</code> (in <code>llvm/Analysis/ConstantFolding.h</code>)</li>
1190 <li><code>ConstantVector::get</code></li>
1191 <li><code>DIBuilder::createComplexVariable</code></li>
1192 <li><code>DIBuilder::getOrCreateArray</code></li>
1193 <li><code>ExtractValueInst::Create</code></li>
1194 <li><code>ExtractValueInst::getIndexedType</code></li>
1195 <li><code>ExtractValueInst::getIndices</code></li>
1196 <li><code>FindInsertedValue</code> (in <code>llvm/Analysis/ValueTracking.h</code>)</li>
1197 <li><code>gep_type_begin</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
1198 <li><code>gep_type_end</code> (in <code>llvm/Support/GetElementPtrTypeIterator.h</code>)</li>
1199 <li><code>GetElementPtrInst::Create</code></li>
1200 <li><code>GetElementPtrInst::CreateInBounds</code></li>
1201 <li><code>GetElementPtrInst::getIndexedType</code></li>
1202 <li><code>InsertValueInst::Create</code></li>
1203 <li><code>InsertValueInst::getIndices</code></li>
1204 <li><code>InvokeInst::Create</code></li>
1205 <li><code>IRBuilder::CreateCall</code></li>
1206 <li><code>IRBuilder::CreateExtractValue</code></li>
1207 <li><code>IRBuilder::CreateGEP</code></li>
1208 <li><code>IRBuilder::CreateInBoundsGEP</code></li>
1209 <li><code>IRBuilder::CreateInsertValue</code></li>
1210 <li><code>IRBuilder::CreateInvoke</code></li>
1211 <li><code>MDNode::get</code></li>
1212 <li><code>MDNode::getIfExists</code></li>
1213 <li><code>MDNode::getTemporary</code></li>
1214 <li><code>MDNode::getWhenValsUnresolved</code></li>
1215 <li><code>SimplifyGEPInst</code> (in <code>llvm/Analysis/InstructionSimplify.h</code>)</li>
1216 <li><code>TargetData::getIndexedOffset</code></li>
1219 <li>All forms of <code>StringMap::getOrCreateValue</code> have been remove
1220 except for the one which takes a <code>StringRef</code>.</li>
1222 <li>The <code>LLVMBuildUnwind</code> function from the C API was removed. The
1223 LLVM <code>unwind</code> instruction has been deprecated for a long time
1224 and isn't used by the current front-ends. So this was removed during the
1225 exception handling rewrite.</li>
1227 <li>The <code>LLVMAddLowerSetJmpPass</code> function from the C API was
1228 removed because the <code>LowerSetJmp</code> pass was removed.</li>
1230 <li>The <code>DIBuilder</code> interface used by front ends to encode
1231 debugging information in the LLVM IR now expects clients to
1232 use <code>DIBuilder::finalize()</code> at the end of translation unit to
1233 complete debugging information encoding.</li>
1235 <li>TargetSelect.h moved to Support/ from Target/</li>
1237 <li>UpgradeIntrinsicCall no longer upgrades pre-2.9 intrinsic calls (for
1238 example <code>llvm.memset.i32</code>).</li>
1240 <li>It is mandatory to initialize all out-of-tree passes too and their dependencies now with
1241 <code>INITIALIZE_PASS{BEGIN,END,}</code>
1242 and <code>INITIALIZE_{PASS,AG}_DEPENDENCY</code>.</li>
1244 <li>The interface for MemDepResult in MemoryDependenceAnalysis has been
1245 enhanced with new return types Unknown and NonFuncLocal, in addition to
1246 the existing types Clobber, Def, and NonLocal.</li>
1253 <!-- *********************************************************************** -->
1255 <a name="knownproblems">Known Problems</a>
1257 <!-- *********************************************************************** -->
1261 <p>LLVM is generally a production quality compiler, and is used by a broad range
1262 of applications and shipping in many products. That said, not every
1263 subsystem is as mature as the aggregate, particularly the more obscure
1264 targets. If you run into a problem, please check the <a
1265 href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
1266 there isn't already one or ask on the <a
1267 href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev
1270 <p>Known problem areas include:</p>
1273 <li>The Alpha, Blackfin, CellSPU, MSP430, PTX, SystemZ and
1274 XCore backends are experimental, and the Alpha, Blackfin and SystemZ
1275 targets have already been removed from mainline.</li>
1277 <li>The integrated assembler, disassembler, and JIT is not supported by
1278 several targets. If an integrated assembler is not supported, then a
1279 system assembler is required. For more details, see the <a
1280 href="CodeGenerator.html#targetfeatures">Target Features Matrix</a>.
1283 <li>The C backend has numerous problems and is not being actively maintained.
1284 Depending on it for anything serious is not advised.</li>
1291 <!-- *********************************************************************** -->
1293 <a name="additionalinfo">Additional Information</a>
1295 <!-- *********************************************************************** -->
1299 <p>A wide variety of additional information is available on
1300 the <a href="http://llvm.org/">LLVM web page</a>, in particular in
1301 the <a href="http://llvm.org/docs/">documentation</a> section. The web page
1302 also contains versions of the API documentation which is up-to-date with the
1303 Subversion version of the source code. You can access versions of these
1304 documents specific to this release by going into the "<tt>llvm/doc/</tt>"
1305 directory in the LLVM tree.</p>
1307 <p>If you have any questions or comments about LLVM, please feel free to contact
1308 us via the <a href="http://llvm.org/docs/#maillist"> mailing lists</a>.</p>
1312 <!--=========================================================================-->
1314 <!-- EH details: to be moved to a blog post:
1319 <p>One of the biggest changes is that 3.0 has a new exception handling
1320 system. The old system used LLVM intrinsics to convey the exception handling
1321 information to the code generator. It worked in most cases, but not
1322 all. Inlining was especially difficult to get right. Also, the intrinsics
1323 could be moved away from the <code>invoke</code> instruction, making it hard
1324 to recover that information.</p>
1326 <p>The new EH system makes exception handling a first-class member of the IR. It
1327 adds two new instructions:</p>
1330 <li><a href="LangRef.html#i_landingpad"><code>landingpad</code></a> —
1331 this instruction defines a landing pad basic block. It contains all of the
1332 information that's needed by the code generator. It's also required to be
1333 the first non-PHI instruction in the landing pad. In addition, a landing
1334 pad may be jumped to only by the unwind edge of an <code>invoke</code>
1337 <li><a href="LangRef.html#i_resume"><code>resume</code></a> — this
1338 instruction causes the current exception to resume traveling up the
1339 stack. It replaces the <code>@llvm.eh.resume</code> intrinsic.</li>
1342 <p>Converting from the old EH API to the new EH API is rather simple, because a
1343 lot of complexity has been removed. The two intrinsics,
1344 <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code> have been
1345 superseded by the <code>landingpad</code> instruction. Instead of generating
1346 a call to <code>@llvm.eh.exception</code> and <code>@llvm.eh.selector</code>:
1348 <div class="doc_code">
1350 Function *ExcIntr = Intrinsic::getDeclaration(TheModule,
1351 Intrinsic::eh_exception);
1352 Function *SlctrIntr = Intrinsic::getDeclaration(TheModule,
1353 Intrinsic::eh_selector);
1355 // The exception pointer.
1356 Value *ExnPtr = Builder.CreateCall(ExcIntr, "exc_ptr");
1358 std::vector<Value*> Args;
1359 Args.push_back(ExnPtr);
1360 Args.push_back(Builder.CreateBitCast(Personality,
1361 Type::getInt8PtrTy(Context)));
1363 <i>// Add selector clauses to Args.</i>
1365 // The selector call.
1366 Builder.CreateCall(SlctrIntr, Args, "exc_sel");
1370 <p>You should instead generate a <code>landingpad</code> instruction, that
1371 returns an exception object and selector value:</p>
1373 <div class="doc_code">
1375 LandingPadInst *LPadInst =
1376 Builder.CreateLandingPad(StructType::get(Int8PtrTy, Int32Ty, NULL),
1379 Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
1380 Builder.CreateStore(LPadExn, getExceptionSlot());
1382 Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
1383 Builder.CreateStore(LPadSel, getEHSelectorSlot());
1387 <p>It's now trivial to add the individual clauses to the <code>landingpad</code>
1390 <div class="doc_code">
1392 <i><b>// Adding a catch clause</b></i>
1393 Constant *TypeInfo = getTypeInfo();
1394 LPadInst->addClause(TypeInfo);
1396 <i><b>// Adding a C++ catch-all</b></i>
1397 LPadInst->addClause(Constant::getNullValue(Builder.getInt8PtrTy()));
1399 <i><b>// Adding a cleanup</b></i>
1400 LPadInst->setCleanup(true);
1402 <i><b>// Adding a filter clause</b></i>
1403 std::vector<Constant*> TypeInfos;
1404 Constant *TypeInfo = getFilterTypeInfo();
1405 TypeInfos.push_back(Builder.CreateBitCast(TypeInfo, Builder.getInt8PtrTy()));
1407 ArrayType *FilterTy = ArrayType::get(Int8PtrTy, TypeInfos.size());
1408 LPadInst->addClause(ConstantArray::get(FilterTy, TypeInfos));
1412 <p>Converting from using the <code>@llvm.eh.resume</code> intrinsic to
1413 the <code>resume</code> instruction is trivial. It takes the exception
1414 pointer and exception selector values returned by
1415 the <code>landingpad</code> instruction:</p>
1417 <div class="doc_code">
1419 Type *UnwindDataTy = StructType::get(Builder.getInt8PtrTy(),
1420 Builder.getInt32Ty(), NULL);
1421 Value *UnwindData = UndefValue::get(UnwindDataTy);
1422 Value *ExcPtr = Builder.CreateLoad(getExceptionObjSlot());
1423 Value *ExcSel = Builder.CreateLoad(getExceptionSelSlot());
1424 UnwindData = Builder.CreateInsertValue(UnwindData, ExcPtr, 0, "exc_ptr");
1425 UnwindData = Builder.CreateInsertValue(UnwindData, ExcSel, 1, "exc_sel");
1426 Builder.CreateResume(UnwindData);
1436 <!-- *********************************************************************** -->
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