This document contains the release notes for the LLVM Compiler -Infrastructure, release 3.0. Here we describe the status of LLVM, including -major improvements from the previous release and significant known problems. -All LLVM releases may be downloaded from the LLVM releases web site.
+ Infrastructure, release 3.0. Here we describe the status of LLVM, including + major improvements from the previous release and significant known problems. + All LLVM releases may be downloaded from + the LLVM releases web site.For more information about LLVM, including information about the latest -release, please check out the main LLVM -web site. If you have questions or comments, the LLVM Developer's -Mailing List is a good place to send them.
+ release, please check out the main LLVM web + site. If you have questions or comments, + the LLVM + Developer's Mailing List is a good place to send them. -Note that if you are reading this file from a Subversion checkout or the -main LLVM web page, this document applies to the next release, not the -current one. To see the release notes for a specific release, please see the -releases page.
+Note that if you are reading this file from a Subversion checkout or the main + LLVM web page, this document applies to the next release, not the + current one. To see the release notes for a specific release, please see the + releases page.
-The LLVM 3.0 distribution currently consists of code from the core LLVM -repository (which roughly includes the LLVM optimizers, code generators -and supporting tools), the Clang repository and the llvm-gcc repository. In -addition to this code, the LLVM Project includes other sub-projects that are in -development. Here we include updates on these subprojects. -
+ +The LLVM 3.0 distribution currently consists of code from the core LLVM + repository (which roughly includes the LLVM optimizers, code generators and + supporting tools), the Clang repository and the llvm-gcc repository. In + addition to this code, the LLVM Project includes other sub-projects that are + in development. Here we include updates on these subprojects.
Clang is an LLVM front end for the C, -C++, and Objective-C languages. Clang aims to provide a better user experience -through expressive diagnostics, a high level of conformance to language -standards, fast compilation, and low memory use. Like LLVM, Clang provides a -modular, library-based architecture that makes it suitable for creating or -integrating with other development tools. Clang is considered a -production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86 -(32- and 64-bit), and for darwin/arm targets.
+ C++, and Objective-C languages. Clang aims to provide a better user + experience through expressive diagnostics, a high level of conformance to + language standards, fast compilation, and low memory use. Like LLVM, Clang + provides a modular, library-based architecture that makes it suitable for + creating or integrating with other development tools. Clang is considered a + production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86 + (32- and 64-bit), and for darwin/arm targets.In the LLVM 3.0 time-frame, the Clang team has made many improvements:
If Clang rejects your code but another compiler accepts it, please take a -look at the language -compatibility guide to make sure this is not intentional or a known issue. -
+ look at the language + compatibility guide to make sure this is not intentional or a known + issue.-DragonEgg is a -gcc plugin that replaces GCC's -optimizers and code generators with LLVM's. -Currently it requires a patched version of gcc-4.5. -The plugin can target the x86-32 and x86-64 processor families and has been -used successfully on the Darwin, FreeBSD and Linux platforms. -The Ada, C, C++ and Fortran languages work well. -The plugin is capable of compiling plenty of Obj-C, Obj-C++ and Java but it is -not known whether the compiled code actually works or not! -
+DragonEgg is a + gcc plugin that replaces GCC's + optimizers and code generators with LLVM's. It works with gcc-4.5 or gcc-4.6, + targets the x86-32 and x86-64 processor families, and has been successfully + used on the Darwin, FreeBSD, KFreeBSD, Linux and OpenBSD platforms. It fully + supports Ada, C, C++ and Fortran. It has partial support for Go, Java, Obj-C + and Obj-C++.
+ +The 3.0 release has the following notable changes:
+ +-The 3.0 release has the following notable changes:
The VMKit project is an implementation - of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and - just-in-time compilation. As of LLVM 3.0, VMKit now supports generational - garbage collectors. The garbage collectors are provided by the MMTk framework, - and VMKit can be configured to use one of the numerous implemented collectors - of MMTk. -
+ of a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and + just-in-time compilation. As of LLVM 3.0, VMKit now supports generational + garbage collectors. The garbage collectors are provided by the MMTk + framework, and VMKit can be configured to use one of the numerous implemented + collectors of MMTk. +AddressSanitizer + uses compiler instrumentation and a specialized malloc library to find C/C++ + bugs such as use-after-free and out-of-bound accesses to heap, stack, and + globals. The key feature of the tool is speed: the average slowdown + introduced by AddressSanitizer is less than 2x.
+ +Clam AntiVirus is an open source (GPL) + anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail + gateways.
+ +Since version 0.96 it + has bytecode + signatures that allow writing detections for complex malware.
+ +It uses LLVM's JIT to speed up the execution of bytecode on X86, X86-64, + PPC32/64, falling back to its own interpreter otherwise. The git version was + updated to work with LLVM 3.0.
+ +clReflect is a C++ + parser that uses clang/LLVM to derive a light-weight reflection database + suitable for use in game development. It comes with a very simple runtime + library for loading and querying the database, requiring no external + dependencies (including CRT), and an additional utility library for object + management and serialisation.
+ +-Crack aims to provide the -ease of development of a scripting language with the performance of a compiled -language. The language derives concepts from C++, Java and Python, incorporating -object-oriented programming, operator overloading and strong typing.
+ +Crack aims to provide + the ease of development of a scripting language with the performance of a + compiled language. The language derives concepts from C++, Java and Python, + incorporating object-oriented programming, operator overloading and strong + typing.
+ +Eero is a fully + header-and-binary-compatible dialect of Objective-C 2.0, implemented with a + patched version of the Clang/LLVM compiler. It features a streamlined syntax, + Python-like indentation, and new operators, for improved readability and + reduced code clutter. It also has new features such as limited forms of + operator overloading and namespaces, and strict (type-and-operator-safe) + enumerations. It is inspired by languages such as Smalltalk, Python, and + Ruby.
+GHC is an open source, state-of-the-art programming suite for Haskell, a + standard lazy functional programming language. It includes an optimizing + static compiler generating good code for a variety of platforms, together + with an interactive system for convenient, quick development.
+ +GHC 7.0 and onwards include an LLVM code generator, supporting LLVM 2.8 and + later. Since LLVM 2.9, GHC now includes experimental support for the ARM + platform with LLVM 3.0.
+ +gwXscript is an object oriented, - aspect orientied programing language which can create both, executables (ELF, + aspect oriented programming language which can create both executables (ELF, EXE) and shared libraries (DLL, SO, DYNLIB). The compiler is implemented in its own language and translates scripts into LLVM-IR which can be optimized and translated into native code by the LLVM framework. Source code in @@ -322,6 +419,76 @@ object-oriented programming, operator overloading and strong typing.
include-what-you-use
+ is a tool to ensure that a file directly #includes
+ all .h files that provide a symbol that the file uses. It also
+ removes superfluous #includes from source files.
ispc is a compiler for "single program, + multiple data" (SPMD) programs. It compiles a C-based SPMD programming + language to run on the SIMD units of CPUs; it often delivers 5-6x speedups on + a single core of a CPU with an 8-wide SIMD unit compared to serial code, + while still providing a clean and easy-to-understand programming model. For + an introduction to the language and its performance, + see the walkthrough of a short + example program. ispc is licensed under the BSD license.
+ +LanguageKit is + a framework for implementing dynamic languages sharing an object model with + Objective-C. It provides static and JIT compilation using LLVM along with + its own interpreter. Pragmatic Smalltalk is a dialect of Smalltalk, built on + top of LanguageKit, that interfaces directly with Objective-C, sharing the + same object representation and message sending behaviour. These projects are + developed as part of the Étoié desktop environment.
+ +LuaAV is a real-time + audiovisual scripting environment based around the Lua language and a + collection of libraries for sound, graphics, and other media protocols. LuaAV + uses LLVM and Clang to JIT compile efficient user-defined audio synthesis + routines specified in a declarative syntax.
+ +An open source, cross-platform implementation of C# and the CLR that is + binary compatible with Microsoft.NET. Has an optional, dynamically-loaded + LLVM code generation backend in Mini, the JIT compiler.
+ +Note that we use a Git mirror of LLVM with some patches. See: + https://github.com/mono/llvm
+ +Renderscript + is Android's advanced 3D graphics rendering and compute API. It provides a + portable C99-based language with extensions to facilitate common use cases + for enhancing graphics and thread level parallelism. The Renderscript + compiler frontend is based on Clang/LLVM. It emits a portable bitcode format + for the actual compiled script code, as well as reflects a Java interface for + developers to control the execution of the compiled bitcode. Executable + machine code is then generated from this bitcode by an LLVM backend on the + device. Renderscript is thus able to provide a mechanism by which Android + developers can improve performance of their applications while retaining + portability.
+ +The Stupid D Compiler is a + project seeking to write a self-hosting compiler for the D programming + language without using the frontend of the reference compiler (DMD).
+ +TCE uses Clang and LLVM for C/C++ language support, target independent optimizations and also for parts of code generation. It generates new - LLVM-based code generators on the fly for the designed TTA processors - and loads them in to the compiler backend as runtime libraries to avoid + LLVM-based code generators "on the fly" for the designed TTA processors and + loads them in to the compiler backend as runtime libraries to avoid per-target recompilation of larger parts of the compiler chain.
- +ThreadSanitizer is a + data race detector for (mostly) C and C++ code, available for Linux, Mac OS + and Windows. On different systems, we use binary instrumentation frameworks + (Valgrind and Pin) as frontends that generate the program events for the race + detection algorithm. On Linux, there's an option of using LLVM-based + compile-time instrumentation.
+ +ZooLib is Open Source under the MIT + License. It provides GUI, filesystem access, TCP networking, thread-safe + memory management, threading and locking for Mac OS X, Classic Mac OS, + Microsoft Windows, POSIX operating systems with X11, BeOS, Haiku, Apple's iOS + and Research in Motion's BlackBerry.
+ +My current work is to use CLang's static analyzer to improve ZooLib's code + quality. I also plan to set up LLVM compiles of the demo programs and test + programs using CLang and LLVM on all the platforms that CLang, LLVM and + ZooLib all support.
+ +LLVM IR has several new features for better support of new targets and that -expose new optimization opportunities:
+ expose new optimization opportunities: + +One of the biggest changes is that 3.0 has a new exception handling
+ system. The old system used LLVM intrinsics to convey the exception handling
+ information to the code generator. It worked in most cases, but not
+ all. Inlining was especially difficult to get right. Also, the intrinsics
+ could be moved away from the invoke instruction, making it hard
+ to recover that information.
The new EH system makes exception handling a first-class member of the IR. It + adds two new instructions:
landingpad —
+ this instruction defines a landing pad basic block. It contains all of the
+ information that's needed by the code generator. It's also required to be
+ the first non-PHI instruction in the landing pad. In addition, a landing
+ pad may be jumped to only by the unwind edge of an invoke
+ instruction.resume — this
+ instruction causes the current exception to resume traveling up the
+ stack. It replaces the @llvm.eh.resume intrinsic.Converting from the old EH API to the new EH API is rather simple, because a
+ lot of complexity has been removed. The two intrinsics,
+ @llvm.eh.exception and @llvm.eh.selector have been
+ superceded by the landingpad instruction. Instead of generating
+ a call to @llvm.eh.exception and @llvm.eh.selector:
+
+
+Function *ExcIntr = Intrinsic::getDeclaration(TheModule, + Intrinsic::eh_exception); +Function *SlctrIntr = Intrinsic::getDeclaration(TheModule, + Intrinsic::eh_selector); + +// The exception pointer. +Value *ExnPtr = Builder.CreateCall(ExcIntr, "exc_ptr"); + +std::vector<Value*> Args; +Args.push_back(ExnPtr); +Args.push_back(Builder.CreateBitCast(Personality, + Type::getInt8PtrTy(Context))); + +// Add selector clauses to Args. + +// The selector call. +Builder.CreateCall(SlctrIntr, Args, "exc_sel"); ++
You should instead generate a landingpad instruction, that
+ returns an exception object and selector value:
+LandingPadInst *LPadInst = + Builder.CreateLandingPad(StructType::get(Int8PtrTy, Int32Ty, NULL), + Personality, 0); + +Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0); +Builder.CreateStore(LPadExn, getExceptionSlot()); + +Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1); +Builder.CreateStore(LPadSel, getEHSelectorSlot()); ++
It's now trivial to add the individual clauses to the landingpad
+ instruction.
+// Adding a catch clause +Constant *TypeInfo = getTypeInfo(); +LPadInst->addClause(TypeInfo); + +// Adding a C++ catch-all +LPadInst->addClause(Constant::getNullValue(Builder.getInt8PtrTy())); + +// Adding a cleanup +LPadInst->setCleanup(true); + +// Adding a filter clause +std::vector<Constant*> TypeInfos; +Constant *TypeInfo = getFilterTypeInfo(); +TypeInfos.push_back(Builder.CreateBitCast(TypeInfo, Builder.getInt8PtrTy())); + +ArrayType *FilterTy = ArrayType::get(Int8PtrTy, TypeInfos.size()); +LPadInst->addClause(ConstantArray::get(FilterTy, TypeInfos)); ++
Converting from using the @llvm.eh.resume intrinsic to
+ the resume instruction is trivial. It takes the exception
+ pointer and exception selector values returned by
+ the landingpad instruction:
+Type *UnwindDataTy = StructType::get(Builder.getInt8PtrTy(), + Builder.getInt32Ty(), NULL); +Value *UnwindData = UndefValue::get(UnwindDataTy); +Value *ExcPtr = Builder.CreateLoad(getExceptionObjSlot()); +Value *ExcSel = Builder.CreateLoad(getExceptionSelSlot()); +UnwindData = Builder.CreateInsertValue(UnwindData, ExcPtr, 0, "exc_ptr"); +UnwindData = Builder.CreateInsertValue(UnwindData, ExcSel, 1, "exc_sel"); +Builder.CreateResume(UnwindData); ++
The induction variable simplification pass in 3.0 only modifies + induction variables when profitable. Sign and zero extension + elimination, linear function test replacement, loop unrolling, and + other simplifications that require induction variable analysis have + been generalized so they no longer require loops to be rewritten in a + typically suboptimal form prior to optimization. This new design + preserves more IR level information, avoids undoing earlier loop + optimizations (particularly hand-optimized loops), and no longer + strongly depends on the code generator rewriting loops a second time + in a now optimal form--an intractable problem.
+ +The original behavior can be restored with -mllvm -enable-iv-rewrite; + however, support for this mode will be short lived. As such, bug + reports should be filed for any significant performance regressions + when moving from -mllvm -enable-iv-rewrite to the 3.0 default mode.
In addition to a large array of minor performance tweaks and bug fixes, this -release includes a few major enhancements and additions to the optimizers:
+ release includes a few major enhancements and additions to the + optimizers:For more information, please see the Intro to the -LLVM MC Project Blog Post. -
+For more information, please see + the Intro + to the LLVM MC Project Blog Post.
We have put a significant amount of work into the code generator -infrastructure, which allows us to implement more aggressive algorithms and make -it run faster:
+ infrastructure, which allows us to implement more aggressive algorithms and + make it run faster:load volatile"/"store volatile". The old
syntax ("volatile load"/"volatile store")
is still accepted, but is now considered deprecated.
+ llvm.memory.barrier and
+ llvm.atomic.*) are now gone. Please use the new atomic
+ instructions, described in the atomics guide.
PHINode::reserveOperandSpace has been removed. Instead, you
- must specify how many operands to reserve space for when you create the
- PHINode, by passing an extra argument into PHINode::Create.PHINode::block_begin
- and PHINode::block_end.ArrayRef instead of either a pair
- of pointers (or iterators) to the beginning and end of a range, or a pointer
- and a length. Others now return an ArrayRef instead of a
- reference to a SmallVector or std::vector. These
- include:
+ PHINode::reserveOperandSpace has been removed. Instead, you
+ must specify how many operands to reserve space for when you create the
+ PHINode, by passing an extra argument
+ into PHINode::Create.PHINode::block_begin
+ and PHINode::block_end.ArrayRef instead of either a
+ pair of pointers (or iterators) to the beginning and end of a range, or a
+ pointer and a length. Others now return an ArrayRef instead
+ of a reference to a SmallVector
+ or std::vector. These include:
CallInst::CreateTargetData::getIndexedOffsetStringMap::getOrCreateValue have been remove
- except for the one which takes a StringRef.LLVMBuildUnwind function from the C API was removed. The
- LLVM unwind instruction has been deprecated for a long time and
- isn't used by the current front-ends. So this was removed during the
- exception handling rewrite.LLVMAddLowerSetJmpPass function from the C API was removed
- because the LowerSetJmp pass was removed.DIBuilder interface used by front ends to encode debugging
- information in the LLVM IR now expects clients to use DIBuilder::finalize()
- at the end of translation unit to complete debugging information encoding.PATypeHolder
-and OpaqueType are gone, and all APIs deal with Type*
-instead of const Type*.
-If you need to create recursive structures, then create a named structure,
-and use setBody() when all its elements are built.
-Type merging and refining is gone too: named structures are not
-merged with other structures, even if their layout is identical.
-(of course anonymous structures are still uniqued by layout).
-StringMap::getOrCreateValue have been remove
+ except for the one which takes a StringRef.LLVMBuildUnwind function from the C API was removed. The
+ LLVM unwind instruction has been deprecated for a long time
+ and isn't used by the current front-ends. So this was removed during the
+ exception handling rewrite.LLVMAddLowerSetJmpPass function from the C API was
+ removed because the LowerSetJmp pass was removed.DIBuilder interface used by front ends to encode
+ debugging information in the LLVM IR now expects clients to
+ use DIBuilder::finalize() at the end of translation unit to
+ complete debugging information encoding.llvm.memset.i32).PATypeHolder and OpaqueType are gone,
+ and all APIs deal with Type* instead of const
+ Type*. If you need to create recursive structures, then create a
+ named structure, and use setBody() when all its elements are
+ built. Type merging and refining is gone too: named structures are not
+ merged with other structures, even if their layout is identical. (of
+ course anonymous structures are still uniqued by layout).INITIALIZE_PASS{BEGIN,END,} and INITIALIZE_{PASS,AG}_DEPENDENCY.llvm.memset.i32).INITIALIZE_PASS{BEGIN,END,}
+ and INITIALIZE_{PASS,AG}_DEPENDENCY.This section contains significant known problems with the LLVM system, -listed by component. If you run into a problem, please check the LLVM bug database and submit a bug if -there isn't already one.
+This section contains significant known problems with the LLVM system, listed + by component. If you run into a problem, please check + the LLVM bug database and submit a bug if + there isn't already one.
The following components of this LLVM release are either untested, known to -be broken or unreliable, or are in early development. These components should -not be relied on, and bugs should not be filed against them, but they may be -useful to some people. In particular, if you would like to work on one of these -components, please contact us on the LLVMdev list.
+ be broken or unreliable, or are in early development. These components + should not be relied on, and bugs should not be filed against them, but they + may be useful to some people. In particular, if you would like to work on + one of these components, please contact us on + the LLVMdev + list.The C backend has numerous problems and is not being actively maintained. -Depending on it for anything serious is not advised.
+ Depending on it for anything serious is not advised.LLVM 3.0 will be the last release of llvm-gcc.
+LLVM 2.9 was the last release of llvm-gcc.
llvm-gcc is generally very stable for the C family of languages. The only major language feature of GCC not supported by llvm-gcc is the @@ -1009,8 +1372,9 @@ Depending on it for anything serious is not advised.
dragonegg instead.The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being -actively maintained. If you are interested in Ada, we recommend that you -consider using dragonegg instead.
+ actively maintained. If you are interested in Ada, we recommend that you + consider using dragonegg instead. +A wide variety of additional information is available on the LLVM web page, in particular in the documentation section. The web page also -contains versions of the API documentation which is up-to-date with the -Subversion version of the source code. -You can access versions of these documents specific to this release by going -into the "llvm/doc/" directory in the LLVM tree.
+A wide variety of additional information is available on + the LLVM web page, in particular in + the documentation section. The web page + also contains versions of the API documentation which is up-to-date with the + Subversion version of the source code. You can access versions of these + documents specific to this release by going into the "llvm/doc/" + directory in the LLVM tree.
If you have any questions or comments about LLVM, please feel free to contact -us via the mailing -lists.
+ us via the mailing lists.