This document contains the release notes for the LLVM compiler -infrastructure, release 2.4. Here we describe the status of LLVM, including -major improvements from the previous release and any known problems. All LLVM -releases may be downloaded from the LLVM -releases web site.
+This document contains the release notes for the LLVM Compiler +Infrastructure, release 2.7. 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.
+href="http://mail.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 +
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 releases, please see the +current one. To see the release notes for a specific release, please see the releases page.
+The LLVM 2.7 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. +
+ +This is the fifteenth public release of the LLVM Compiler Infrastructure. -It includes a large number of features and refinements from LLVM 2.3.
+ + - - - +The Clang project is ...
+ +In the LLVM 2.7 time-frame, the Clang team has made many improvements:
+ +-
+
- ... +
The LLVM IR generated by llvm-gcc now doesn't name instructions. Use the - instnamer pass if you want them.
+Previously announced in the 2.4, 2.5, and 2.6 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 2.7 time-frame, the analyzer core has ...
++The VMKit project is an implementation of +a JVM and a CLI Virtual Machine (Microsoft .NET is an +implementation of the CLI) using LLVM for static and just-in-time +compilation.
-LLVM API Changes:
++VMKit version ?? builds with LLVM 2.7 and you can find it on its +web page. The release includes +bug fixes, cleanup and new features. The major changes are:
-
-
- .... -
- ... Attributes changes ... - -
- The DbgStopPointInst methods getDirectory and -getFileName now return Value* instead of strings. These can be -converted to strings using llvm::GetConstantStringInfo defined via -"llvm/Analysis/ValueTracking.h". +
- ... -
- API change: BinaryOperator::create -> Create (CmpInst, CastInst too) -
- Various header files like "llvm/ADT/iterator" were given a .h suffix. - Change your code to #include "llvm/ADT/iterator.h" instead.
-The core LLVM 2.4 distribution currently consists of code from the core LLVM -repository (which roughly contains the LLVM optimizer, 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 -vmkit Project. -
+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 "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.
- -...
+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 ... +
-The Clang project is an effort to build -a set of new 'LLVM native' front-end technologies for the LLVM optimizer -and code generator. Clang is continuing to make major strides forward in all -areas. Its C and Objective-C parsing support is very solid, and the code -generation support is far enough along to build many C applications. While not -yet production quality, it is progressing very nicely. In addition, C++ -front-end work has started to make significant progress.
+Codegen progress/state -
+ + + +-static analysis tool +The LLVM Machine Code (MC) Toolkit project is ...
-LLVM 2.4 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. +
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 2.7.
+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.
+LLVM 2.4 includes several major new capabilities:
++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. +
--
-
-
-
MRVs got generalized to FCAs. getresult is gone, ret with multiple values - is gone.
-
+ -O0 compile times overall much faster
-
-Attrs changes?
+
+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.
-Initial PIC16 port
Support the rest of the atomic __sync builtins
+Pure +is an algebraic/functional programming language based on term rewriting. +Programs are collections of equations which are used to evaluate expressions in +a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation, +lexical closures, a hygienic macro system (also based on term rewriting), +built-in list and matrix support (including list and matrix comprehensions) and +an easy-to-use C interface. The interpreter uses LLVM as a backend to + JIT-compile Pure programs to fast native code.
+ +Pure versions ??? and later have been tested and are known to work with +LLVM 2.7 (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. +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. +
+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.
++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 2.4 fully supports the llvm-gcc 4.2 front-end, and includes support -for the C, C++, Objective-C, Ada, and Fortran front-ends.
+ ++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.
++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 2.7 includes several major new capabilities:
+- ... -
New features include: -
+LLVM IR has several new features for better support of new targets and that +expose new optimization opportunities:
-
-
- use diet patch landed: saved 15% IR memory footprint -
- LLVM IR now directly represents "common" linkage, instead of - representing it as a form of weak linkage. -
- DebugInfoBuilder
- ...
In addition to a huge array of bug fixes and minor performance tweaks, the -LLVM 2.4 optimizers support a few major enhancements:
+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:
-
-
- GVN now does local PRE? - -
- Matthijs' Dead argument elimination rewrite +
- ... -
- Old-ADCE used control dependence and deleted output-free infinite loops. -Added a new Loop deletion pass (for deleting output free provably-finite loops) -and rewrote ADCE to be simpler faster, and not need control dependence. +
-
+
- The JIT now defaults +to compiling eagerly to avoid a race condition in the lazy JIT. +Clients that still want the lazy JIT can switch it on by calling +ExecutionEngine::DisableLazyCompilation(false). +
- It is now possible to create more than one JIT instance in the same process. +These JITs can generate machine code in parallel, +although you +still have to obey the other threading restrictions.
We put a significant amount of work into the code generator infrastructure, -which allows us to implement more aggressive algorithms and make it run -faster:
+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:
-
-
- 2-addr pass can now remat trivial insts to avoid a copy. -
- spiller to commute instructions in order to fold a reload -
- Stack slot coloring? -
- Live intervals renumbering? Is this useful to external people? -
- 'is as cheap as a move' instruction flag -
- Improvements to selection dag viewing -
- fast isel -
- Selection dag speedups -
- asmwriter + raw_ostream -> fastah -
- ... +
- ...
New features of the X86 target include: +
+ +-
+
+
- ... + +
New target-specific features include: +
New features of the PIC16 target include:
-
-
- Exception handling is supported by default on Linux/x86-64. -
- Position Independent Code (PIC) is now support on Linux/x86-64.
- ... +
Things not yet supported:
+-
+
- Variable arguments. +
- Interrupts/programs.
New target-specific features include: +
New features of the ARM target include:
-
-
- .... + +
- ...
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.
-
-
- raw_ostream + formatting
- ...
Other miscellaneous features include:
+ +-
+
- ... +
If you're already an LLVM user or developer with out-of-tree changes based +on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading +from the previous release.
+ +-
+
- The LLVM interpreter now defaults to not using libffi even +if you have it installed. This makes it more likely that an LLVM built on one +system will work when copied to a similar system. To use libffi, +configure with --enable-libffi. + +
In addition, many APIs have changed in this release. Some of the major LLVM +API changes are:
+ +-
+
- ModuleProvider has been removed +and its methods moved to Module and GlobalValue. +Most clients can remove uses of ExistingModuleProvider, +replace getBitcodeModuleProvider with +getLazyBitcodeModule, and pass their Module to +functions that used to accept ModuleProvider. Clients who +wrote their own ModuleProviders will need to derive from +GVMaterializer instead and use +Module::setMaterializer to attach it to a +Module. + +
- GhostLinkage has given up the ghost. +GlobalValues that have not yet been read from their backing +storage have the same linkage they will have after being read in. +Clients must replace calls to +GlobalValue::hasNotBeenReadFromBitcode with +GlobalValue::isMaterializable. + +
- FIXME: Debug info has been totally redone. Add pointers to new APIs. Substantial caveats about compatibility of .ll and .bc files. + +
- The llvm/Support/DataTypes.h header has moved +to llvm/System/DataTypes.h. + +
- The isInteger, isIntOrIntVector, isFloatingPoint, +isFPOrFPVector and isFPOrFPVector methods have been renamed +isIntegerTy, isIntOrIntVectorTy, isFloatingPointTy, +isFPOrFPVectorTy and isFPOrFPVectorTy respectively. +
LLVM is known to work on the following platforms:
-
-
- Intel and AMD machines (IA32) running Red Hat Linux, Fedora Core and FreeBSD - (and probably other unix-like systems). -
- PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit and - 64-bit modes. +
- Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat + Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like + systems). +
- PowerPC and X86-based Mac OS X systems, running 10.3 and above in 32-bit + and 64-bit modes.
- Intel and AMD machines running on Win32 using MinGW libraries (native).
- Intel and AMD machines running on Win32 with the Cygwin libraries (limited support is available for native builds with Visual C++). -
- Sun UltraSPARC workstations running Solaris 10. +
- Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.
- Alpha-based machines running Debian GNU/Linux. -
- Itanium-based (IA64) machines running Linux and HP-UX.
The core LLVM infrastructure uses GNU autoconf to adapt itself @@ -398,12 +693,26 @@ portability patches and reports of successful builds or error messages.
This section contains all known problems with the LLVM system, listed by -component. As new problems are discovered, they will be added to these -sections. If you run into a problem, please check the 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 llvm-gcc bootstrap will fail with some versions of binutils (e.g. 2.15) + with a message of "Error: can not do 8 + byte pc-relative relocation" when building C++ code. We intend to + fix this on mainline, but a workaround is to upgrade to binutils 2.17 or + later. + +
- LLVM will not correctly compile on Solaris and/or OpenSolaris +using the stock GCC 3.x.x series 'out the box', +See: Broken versions of GCC and other tools. +However, A Modern GCC Build +for x86/x86-64 has been made available from the third party AuroraUX Project +that has been meticulously tested for bootstrapping LLVM & Clang. +
-
-
- The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental. -
- The llc "-filetype=asm" (the default) is the only supported - value for this option. +
- The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430 and SystemZ backends are + experimental. +
- The llc "-filetype=asm" (the default) is the only + supported value for this option. The ELF writer is experimental. +
- The implementation of Andersen's Alias Analysis has many known bugs.
-
+
- Support for the Advanced SIMD (Neon) instruction set is still incomplete +and not well tested. Some features may not work at all, and the code quality +may be poor in some cases.
- Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6 processors, thumb programs can crash or produce wrong results (PR1388). -
- Compilation for ARM Linux OABI (old ABI) is supported, but not fully tested. +
- Compilation for ARM Linux OABI (old ABI) is supported but not fully tested. -
- There is a bug in QEMU-ARM (<= 0.9.0) which causes it to incorrectly - execute -programs compiled with LLVM. Please use more recent versions of QEMU.
-
-
- The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not +
- The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not support the 64-bit SPARC ABI (-m64).
-
-
-
- On 21164s, some rare FP arithmetic sequences which may trap do not have the -appropriate nops inserted to ensure restartability. - +
- 64-bit MIPS targets are not supported yet.
-
-
- The Itanium backend is highly experimental, and has a number of known - issues. We are looking for a maintainer for the Itanium backend. If you - are interested, please contact the llvmdev mailing list. -
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 @@ -587,11 +894,23 @@ itself, Qt, Mozilla, etc.
- Exception handling works well on the X86 and PowerPC targets. Currently - only linux and darwin targets are supported (both 32 and 64 bit). + only Linux and Darwin targets are supported (both 32 and 64 bit).
-
+
- Fortran support generally works, but there are still several unresolved bugs + in Bugzilla. Please see the + tools/gfortran component for details. +
- The Ada front-end currently only builds on X86-32. This is mainly due -to lack of trampoline support (pointers to nested functions) on other platforms, -however it also fails to build on X86-64 +to lack of trampoline support (pointers to nested functions) on other platforms. +However, it also fails to build on X86-64 which does support trampolines.
- The Ada front-end fails to bootstrap. -Workaround: configure with --disable-bootstrap. -
- The c380004 and c393010 ACATS tests -fail (c380004 also fails with gcc-4.2 mainline). When built at -O3, the -cxg2021 ACATS test also fails. -
- Some gcc specific Ada tests continue to crash the compiler. The testsuite -reports most tests as having failed even though they pass. -
- The -E binder option (exception backtraces) +This is due to lack of LLVM support for setjmp/longjmp style +exception handling, which is used internally by the compiler. +Workaround: configure with --disable-bootstrap. +
- The c380004, c393010 +and cxg2021 ACATS tests fail +(c380004 also fails with gcc-4.2 mainline). +If the compiler is built with checks disabled then c393010 +causes the compiler to go into an infinite loop, using up all system memory. +
- Some GCC specific Ada tests continue to crash the compiler. +
- The -E binder option (exception backtraces) does not work and will result in programs -crashing if an exception is raised. Workaround: do not use -E. +crashing if an exception is raised. Workaround: do not use -E.
- Only discrete types are allowed to start or finish at a non-byte offset in a record. Workaround: do not pack records or use representation clauses that result in a field of a non-discrete type @@ -629,6 +951,20 @@ ignored.
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.
+
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