This document contains the release notes for the LLVM Compiler -Infrastructure, release 2.5. Here we describe the status of LLVM, including +Infrastructure, release 2.6. 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.
@@ -51,25 +51,37 @@ current one. To see the release notes for a specific release, please see the releases page.-The LLVM 2.5 distribution currently consists of code from the core LLVM -repository (which roughly includes the LLVM optimizers, code generators and -supporting tools) and the llvm-gcc repository. In addition to this code, the -LLVM Project includes other sub-projects that are in development. The two which -are the most actively developed are the Clang Project and -the VMKit Project. +The LLVM 2.6 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 Clang project is an effort to build -a set of new 'LLVM native' front-end technologies for the LLVM optimizer -and code generator. While Clang is not included in the LLVM 2.5 release, it -is continuing to make major strides forward in all areas. Its C and Objective-C -parsing and code generation support is now very solid. For example, it is -capable of successfully building many real applications for X86-32 and X86-64, -including the FreeBSD -kernel. C++ is also making incredible progress, and work -on templates has recently started.
- -While Clang is not yet production quality, it is progressing very nicely and -is quite usable for building many C and Objective-C applications. If you are -interested in fast compiles and good diagnostics, we encourage you to try it out -by building from mainline -and reporting any issues you hit to the fast compiles and +good diagnostics, we +encourage you to try it out. Clang currently compiles typical Objective-C code +3x faster than GCC and compiles C code about 30% faster than GCC at -O0 -g +(which is when the most pressure is on the frontend).
+ +In addition to supporting these languages, C++ support is also well under way, and mainline +Clang is able to parse the libstdc++ 4.2 headers and even codegen simple apps. +If you are interested in Clang C++ support or any other Clang feature, we +strongly encourage you to get involved on the Clang front-end mailing list.
-In the LLVM 2.5 time-frame, the Clang team has made many improvements:
+In the LLVM 2.6 time-frame, the Clang team has made many improvements:
Previously announced in the last LLVM release, the Clang project also +
Previously announced in the 2.4 and 2.5 LLVM releases, the Clang project also includes an early stage static source code analysis tool for automatically finding bugs -in C and Objective-C programs. The tool performs a growing set of checks to find +in C and Objective-C programs. The tool performs checks to find bugs that occur on a specific path within a program.
-In the LLVM 2.5 time-frame there have been many significant improvements to -the analyzer's core path simulation engine and machinery for generating -path-based bug reports to end-users. Particularly noteworthy improvements -include experimental support for full field-sensitivity and reasoning about heap -objects as well as an improved value-constraints subengine that does a much -better job of reasoning about inequality relationships (e.g., x > 2) -between variables and constants. +
In the LLVM 2.6 time-frame, the analyzer core has undergone several important +improvements and cleanups and now includes a new Checker interface that +is intended to eventually serve as a basis for domain-specific checks. Further, +in addition to generating HTML files for reporting analysis results, the +analyzer can now also emit bug reports in a structured XML format that is +intended to be easily readable by other programs.
-The set of checks performed by the static analyzer continue to expand, and +
The set of checks performed by the static analyzer continues to expand, and future plans for the tool include full source-level inter-procedural analysis and deeper checks such as buffer overrun detection. There are many opportunities to extend and enhance the static analyzer, and anyone interested in working on @@ -166,38 +173,191 @@ this project is encouraged to get involved!
The VMKit project is an implementation of -a JVM and a CLI Virtual Machines (Microsoft .NET is an -implementation of the CLI) using the Just-In-Time compiler of LLVM.
+a JVM and a CLI Virtual Machine (Microsoft .NET is an +implementation of the CLI) using LLVM for static and just-in-time +compilation. -Following LLVM 2.5, VMKit has its first release that you can find on its -webpage. The release includes +
+VMKit version 0.26 builds with LLVM 2.6 and you can find it on its +web page. The release includes bug fixes, cleanup and new features. The major changes are:
+The new LLVM compiler-rt project +is a simple library that provides an implementation of the low-level +target-specific hooks required by code generation and other runtime components. +For example, when compiling for a 32-bit target, converting a double to a 64-bit +unsigned integer is compiled into a runtime call to the "__fixunsdfdi" +function. The compiler-rt library provides highly optimized implementations of +this and other low-level routines (some are 3x faster than the equivalent +libgcc routines).
+ ++All of the code in the compiler-rt project is available under the standard LLVM +License, a "BSD-style" license.
+ ++The new LLVM KLEE project is a symbolic +execution framework for programs in LLVM bitcode form. KLEE tries to +symbolically evaluate "all" paths through the application and records state +transitions that lead to fault states. This allows it to construct testcases +that lead to faults and can even be used to verify algorithms. For more +details, please see the OSDI 2008 paper about +KLEE.
+ ++The goal of DragonEgg is to make +gcc-4.5 act like llvm-gcc without requiring any gcc modifications whatsoever. +DragonEgg is a shared library (dragonegg.so) +that is loaded by gcc at runtime. It uses the new gcc plugin architecture to +disable the GCC optimizers and code generators, and schedule the LLVM optimizers +and code generators (or direct output of LLVM IR) instead. Currently only Linux +and Darwin are supported, and only on x86-32 and x86-64. It should be easy to +add additional unix-like architectures and other processor families. In theory +it should be possible to use DragonEgg +with any language supported by gcc, however only C and Fortran work well for the +moment. Ada and C++ work to some extent, while Java, Obj-C and Obj-C++ are so +far entirely untested. Since gcc-4.5 has not yet been released, neither has +DragonEgg. To build +DragonEgg you will need to check out the +development versions of gcc, +llvm and +DragonEgg from their respective +subversion repositories, and follow the instructions in the +DragonEgg README. +
+ ++The LLVM Machine Code (MC) Toolkit project is a (very early) effort to build +better tools for dealing with machine code, object file formats, etc. The idea +is to be able to generate most of the target specific details of assemblers and +disassemblers from existing LLVM target .td files (with suitable enhancements), +and to build infrastructure for reading and writing common object file formats. +One of the first deliverables is to build a full assembler and integrate it into +the compiler, which is predicted to substantially reduce compile time in some +scenarios. +
+ +In the LLVM 2.6 timeframe, the MC framework has grown to the point where it +can reliably parse and pretty print (with some encoding information) a +darwin/x86 .s file successfully, and has the very early phases of a Mach-O +assembler in progress. Beyond the MC framework itself, major refactoring of the +LLVM code generator has started. The idea is to make the code generator reason +about the code it is producing in a much more semantic way, rather than a +textual way. For example, the code generator now uses MCSection objects to +represent section assignments, instead of text strings that print to .section +directives.
+ +MC is an early and ongoing project that will hopefully continue to lead to +many improvements in the code generator and build infrastructure useful for many +other situations. +
+ +An exciting aspect of LLVM is that it is used as an enabling technology for + a lot of other language and tools projects. This section lists some of the + projects that have already been updated to work with LLVM 2.6.
+Rubinius is an environment +for running Ruby code which strives to write as much of the core class +implementation in Ruby as possible. Combined with a bytecode interpreting VM, it +uses LLVM to optimize and compile ruby code down to machine code. Techniques +such as type feedback, method inlining, and uncommon traps are all used to +remove dynamism from ruby execution and increase performance.
+ +Since LLVM 2.5, Rubinius has made several major leaps forward, implementing +a counter based JIT, type feedback and speculative method inlining. +
+ ++MacRuby is an implementation of Ruby on top of +core Mac OS X technologies, such as the Objective-C common runtime and garbage +collector and the CoreFoundation framework. It is principally developed by +Apple and aims at enabling the creation of full-fledged Mac OS X applications. +
+ ++MacRuby uses LLVM for optimization passes, JIT and AOT compilation of Ruby +expressions. It also uses zero-cost DWARF exceptions to implement Ruby exception +handling.
+ +In addition to the usual algebraic data structures, Pure also has -MATLAB-style matrices in order to support numeric computations and signal -processing in an efficient way. Pure is mainly aimed at mathematical -applications right now, but it has been designed as a general purpose language. -The dynamic interpreter environment and the C interface make it possible to use -it as a kind of functional scripting language for many application areas. +
Pure versions 0.31 and later have been tested and are known to work with +LLVM 2.6 (and continue to work with older LLVM releases >= 2.3 as well).
LDC is an implementation of the D Programming Language using the LLVM optimizer and code generator. -LDC project works great with the LLVM 2.5 release. General improvmenets in this +The LDC project works great with the LLVM 2.6 release. General improvements in +this cycle have included new inline asm constraint handling, better debug info -support, general bugfixes, and better x86-64 support. This has allowed -some major improvements in LDC, getting us much closer to being as +support, general bug fixes and better x86-64 support. This has allowed +some major improvements in LDC, getting it much closer to being as fully featured as the original DMD compiler from DigitalMars.
Roadsend PHP (rphp) is an open -source compiler for the PHP programming language that uses LLVM for its -optimizer, JIT, and static compiler. This is a reimplementation of an earlier -project that is now based on the LLVM.
++Roadsend PHP (rphp) is an open +source implementation of the PHP programming +language that uses LLVM for its optimizer, JIT and static compiler. This is a +reimplementation of an earlier project that is now based on LLVM.
This release includes a huge number of bug fixes, performance tweaks, and -minor improvements. Some of the major improvements and new features are listed -in this section. -
++Unladen Swallow is a +branch of Python intended to be fully +compatible and significantly faster. It uses LLVM's optimization passes and JIT +compiler.
+LLVM-Lua uses LLVM to add JIT +and static compiling support to the Lua VM. Lua bytecode is analyzed to +remove type checks, then LLVM is used to compile the bytecode down to machine +code.
+LLVM 2.5 includes several major new capabilities:
+ + -+IcedTea provides a +harness to build OpenJDK using only free software build tools and to provide +replacements for the not-yet free parts of OpenJDK. One of the extensions that +IcedTea provides is a new JIT compiler named Shark which uses LLVM +to provide native code generation without introducing processor-dependent +code. +
+This release includes a huge number of bug fixes, performance tweaks and +minor improvements. Some of the major improvements and new features are listed +in this section. +
LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC -front-ends and driver with the LLVM optimizer and code generator. It currently -includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.
+LLVM 2.6 includes several major new capabilities:
LLVM IR has several new features that are used by our existing front-ends and -can be useful if you are writing a front-end for LLVM:
+LLVM IR has several new features for better support of new targets and that +expose new optimization opportunities:
In addition to a huge array of bug fixes and minor performance tweaks, this +
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:
Things not yet supported:
New features include:
+New features of the ARM target include: +
These features are still somewhat experimental +and subject to change. The Neon intrinsics, in particular, may change in future +releases of LLVM. ARMv7 support has progressed a lot on top of tree since 2.6 +branched.
-New features of other targets include: +
+New features include: + +
This release includes a number of new APIs that are used internally, which + may also be useful for external clients.
Other miscellaneous features include:
+ +If you're already an LLVM user or developer with out-of-tree changes based -on LLVM 2.4, this section lists some "gotchas" that you may run into upgrading +on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading from the previous release.
The core LLVM infrastructure uses GNU autoconf to adapt itself @@ -673,6 +1049,21 @@ 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.
+llvm-gcc does not currently support Link-Time -Optimization on most platforms "out-of-the-box". Please inquire on the -LLVMdev mailing list if you are interested.
-The only major language feature of GCC not supported by llvm-gcc is the __builtin_apply family of builtins. However, some extensions are only supported on some targets. For example, trampolines are only @@ -884,10 +1258,8 @@ itself, Qt, Mozilla, etc.
The Llvm.Linkage module is broken, and has incorrect values. Only +Llvm.Linkage.External, Llvm.Linkage.Available_externally, and +Llvm.Linkage.Link_once will be correct. If you need any of the other linkage +modes, you'll have to write an external C library in order to expose the +functionality. This has been fixed in the trunk.
+