Written by the LLVM Team
+This document contains the release notes for the LLVM Compiler -Infrastructure, release 2.6. Here we describe the status of LLVM, including +Infrastructure, release 2.8. 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.
@@ -42,8 +51,8 @@ href="http://llvm.org/releases/">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.
+href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">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 @@ -58,30 +67,22 @@ Almost dead code. include/llvm/Analysis/LiveValues.h => Dan lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8. llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8. + ABCD, GEPSplitterPass + MSIL backend? + lib/Transforms/Utils/SSI.cpp -> ABCD depends on it. --> - @@ -92,7 +93,7 @@ Almost dead code.
-The LLVM 2.6 distribution currently consists of code from the core LLVM +The LLVM 2.8 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 @@ -109,31 +110,49 @@ 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 C family of languages. -LLVM 2.6 is the first release to officially include Clang, and it provides a -production quality C and Objective-C compiler. If you are interested in 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 2.6 time-frame, the Clang team has made many improvements:
+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 and Objective-C on x86 (32- and 64-bit).
+ +In the LLVM 2.7 time-frame, the Clang team has made many improvements:
void function, etc.), sign-comparison warnings, and improved
+format-string warnings.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 checks to find -bugs that occur on a specific path within a program.
- -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 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 -this project is encouraged to get involved!
+The Clang Static Analyzer + project is an effort to use static source code analysis techniques to + automatically find bugs in C and Objective-C programs (and hopefully C++ in the + future!). The tool is very good at finding bugs that occur on specific + paths through code, such as on error conditions.
+ +In the LLVM 2.7 time-frame, the analyzer core has made several major and + minor improvements, including better support for tracking the fields of + structures, initial support (not enabled by default yet) for doing + interprocedural (cross-function) analysis, and new checks have been added. +
-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:
+With the release of LLVM 2.7, VMKit has shifted to a great framework for writing +virtual machines. VMKit now offers precise and efficient garbage collection with +multi-threading support, thanks to the MMTk memory management toolkit, as well +as just in time and ahead of time compilation with LLVM. The major changes in +VMKit 0.27 are:All of the code in the compiler-rt project is available under the standard LLVM -License, a "BSD-style" license.
+License, a "BSD-style" license. New in LLVM 2.7: compiler_rt now +supports ARM targets.-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.
- -+DragonEgg is still a work in progress. Currently C works very well, while C++, +Ada and Fortran work fairly well. All other languages either don't work at all, +or only work poorly. For the moment only the x86-32 and x86-64 targets are +supported, and only on linux and darwin (darwin needs an additional gcc patch). +
--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. +DragonEgg is a new project which is seeing its first release with llvm-2.7.
-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. +The LLVM Machine Code (aka MC) sub-project of LLVM was created to solve a number +of problems in the realm of assembly, disassembly, object file format handling, +and a number of other related areas that CPU instruction-set level tools work +in. It is a sub-project of LLVM which provides it with a number of advantages +over other compilers that do not have tightly integrated assembly-level tools. +For a gentle introduction, please see the Intro to the +LLVM MC Project Blog Post.
-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. -
+2.7 includes major parts of the work required by the new MC Project. A few + targets have been refactored to support it, and work is underway to support a + native assembler in LLVM. This work is not complete in LLVM 2.7, but it has + made substantially more progress on LLVM mainline.
+ +One minor example of what MC can do is to transcode an AT&T syntax + X86 .s file into intel syntax. You can do this with something like:
++ llvm-mc foo.s -output-asm-variant=1 -o foo-intel.s +
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. -
- + projects that have already been updated to work with LLVM 2.7.-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.
- -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). -
-Pure versions 0.43 and later have been tested and are known to work with +LLVM 2.7 (and continue to work with older LLVM releases >= 2.5).
--LDC is an implementation of -the D Programming Language using the LLVM optimizer and code generator. -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 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. -
-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.
+TCE is a toolset for designing +application-specific processors (ASP) based on the Transport triggered +architecture (TTA). The toolset provides a complete co-design flow from C/C++ +programs down to synthesizable VHDL and parallel program binaries. Processor +customization points include the register files, function units, supported +operations, and the interconnection network. + +TCE uses llvm-gcc/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 per-target +recompilation of larger parts of the compiler chain.
+ ++SAFECode is a memory safe C +compiler built using LLVM. It takes standard, unannotated C code, analyzes the +code to ensure that memory accesses and array indexing operations are safe, and +instruments the code with run-time checks when safety cannot be proven +statically. +
Icedtea6 1.8 and later have been tested and are known to work with +LLVM 2.7 (and continue to work with older LLVM releases >= 2.6 as well). +
+ ++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-Lua 1.2.0 have been tested and is known to work with LLVM 2.7. +
++MacRuby is an implementation of Ruby based on +core Mac OS technologies, sponsored by Apple Inc. It uses LLVM at runtime for +optimization passes, JIT compilation and exception handling. It also allows +static (ahead-of-time) compilation of Ruby code straight to machine code. +
+The upcoming MacRuby 0.6 release works with LLVM 2.7. +
++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.
+ +In addition to the existing C and native code generators, GHC now +supports an LLVM +code generator. GHC supports LLVM 2.7.
+ +In addition to changes to the code, between LLVM 2.6 and 2.7, a number of +organization changes have happened: +
+ +LLVM 2.6 includes several major new capabilities:
+LLVM 2.7 includes several major new capabilities:
New features of the PIC16 target include: -
- -Things not yet supported:
- -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: -
- -Other miscellaneous features include:
If you're already an LLVM user or developer with out-of-tree changes based -on LLVM 2.5, this section lists some "gotchas" that you may run into upgrading +on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading from the previous release.
In addition, many APIs have changed in this release. Some of the major LLVM API changes are:
If you run into GCC extensions which are not supported, please let us know. -
- -The C++ front-end is considered to be fully -tested and works for a number of non-trivial programs, including LLVM -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.
-