- Introduction
- Sub-project Status Update
- - What's New in LLVM?
+ - External Projects Using LLVM 2.6
+ - What's New in LLVM 2.6?
- Installation Instructions
- Portability and Supported Platforms
- Known Problems
@@ -33,9 +34,9 @@
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.
For more information about LLVM, including information about the latest
@@ -50,20 +51,37 @@ current one. To see the release notes for a specific release, please see the
releases page.
+
-
+
+
+
@@ -74,12 +92,11 @@ current one. To see the release notes for a specific release, please see the
-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.
@@ -93,33 +110,31 @@ the VMKit Project.
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:
-- Clang now has a new driver, which is focused on providing a GCC-compatible
- interface.
-- The X86-64 ABI is now supported.
-- Precompiled header support is now implemented.
-- Objective-C support is significantly improved beyond LLVM 2.4, supporting
- many features, such as Objective-C Garbage Collection.
-- Many many bugs are fixed.
+- C and Objective-C support are now considered production quality.
+- AuroraUX, FreeBSD and OpenBSD are now supported.
+- Most of Objective-C 2.0 is now supported with the GNU runtime.
+- Many many bugs are fixed and lots of features have been added.
+
@@ -129,28 +144,24 @@ list.
-
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 bugs that occur on a specific path within a program. Examples
-of bugs the tool finds include logic errors such as null dereferences,
-violations of various API rules, dead code, and potential memory leaks in
-Objective-C programs. Since its inception, public feedback on the tool has been
-extremely positive, and conservative estimates put the number of real bugs it
-has found in industrial-quality software on the order of thousands.
-
-
The tool also provides a simple web GUI to inspect potential bugs found by
-the tool. While still early in development, the GUI illustrates some of the key
-features of Clang: accurate source location information, which is used by the
-GUI to highlight specific code expressions that relate to a bug (including those
-that span multiple lines); and built-in knowledge of macros, which is used to
-perform inline expansion of macros within the GUI itself.
-
-
The set of checks performed by the static analyzer is gradually expanding,
-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!
+
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 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:
-- ?
+- A new llcj tool to generate shared libraries or executables of Java
+ files.
+- Cooperative garbage collection.
+- Fast subtype checking (paper from Click et al [JGI'02]).
+- Implementation of a two-word header for Java objects instead of the original
+ three-word header.
+- Better Java specification-compliance: division by zero checks, stack
+ overflow checks, finalization and references support.
+
+
+
+
+
+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.
+
+
+
-
This release includes a huge number of bug fixes, performance tweaks, and
+
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.
+
+
+
+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 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.
+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-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 2.5 includes several major new capabilities:
+
LLVM 2.6 includes several major new capabilities:
- Legalize Types
- New compiler-rt, KLEE
+ and machine code toolkit sub-projects.
+- Debug information now includes line numbers when optimizations are enabled.
+ This allows statistical sampling tools like OProfile and Shark to map
+ samples back to source lines.
+- LLVM now includes new experimental backends to support the MSP430, SystemZ
+ and BlackFin architectures.
+- LLVM supports a new Gold Linker Plugin which
+ enables support for transparent
+ link-time optimization on ELF targets when used with the Gold binutils
+ linker.
+- LLVM now supports doing optimization and code generation on multiple
+ threads. Please see the LLVM
+ Programmer's Manual for more information.
+- LLVM now has experimental support for embedded
+ metadata in LLVM IR, though the implementation is not guaranteed to be
+ final and the .bc file format may change in future releases. Debug info
+ does not yet use this format in LLVM 2.6.
+
-
+
+
LLVM IR has several new features for better support of new targets and that
+expose new optimization opportunities:
+
+- The add, sub and mul
+ instructions have been split into integer and floating point versions (like
+ divide and remainder), introducing new fadd, fsub,
+ and fmul instructions.
+- The add, sub and mul
+ instructions now support optional "nsw" and "nuw" bits which indicate that
+ the operation is guaranteed to not overflow (in the signed or
+ unsigned case, respectively). This gives the optimizer more information and
+ can be used for things like C signed integer values, which are undefined on
+ overflow.
+- The sdiv instruction now supports an
+ optional "exact" flag which indicates that the result of the division is
+ guaranteed to have a remainder of zero. This is useful for optimizing pointer
+ subtraction in C.
+- The getelementptr instruction now
+ supports arbitrary integer index values for array/pointer indices. This
+ allows for better code generation on 16-bit pointer targets like PIC16.
+- The getelementptr instruction now
+ supports an "inbounds" optimization hint that tells the optimizer that the
+ pointer is guaranteed to be within its allocated object.
+- LLVM now support a series of new linkage types for global values which allow
+ for better optimization and new capabilities:
+
+ - linkonce_odr and
+ weak_odr have the same linkage
+ semantics as the non-"odr" linkage types. The difference is that these
+ linkage types indicate that all definitions of the specified function
+ are guaranteed to have the same semantics. This allows inlining
+ templates functions in C++ but not inlining weak functions in C,
+ which previously both got the same linkage type.
+ - available_externally
+ is a new linkage type that gives the optimizer visibility into the
+ definition of a function (allowing inlining and side effect analysis)
+ but that does not cause code to be generated. This allows better
+ optimization of "GNU inline" functions, extern templates, etc.
+ - linker_private is a
+ new linkage type (which is only useful on Mac OS X) that is used for
+ some metadata generation and other obscure things.
+
+- Finally, target-specific intrinsics can now return multiple values, which
+ is useful for modeling target operations with multiple results.
-
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.
+
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:
-- ?
+
+- The Scalar Replacement of Aggregates
+ pass has many improvements that allow it to better promote vector unions,
+ variables which are memset, and much more strange code that can happen to
+ do bitfield accesses to register operations. An interesting change is that
+ it now produces "unusual" integer sizes (like i1704) in some cases and lets
+ other optimizers clean things up.
+- The Loop Strength Reduction pass now
+ promotes small integer induction variables to 64-bit on 64-bit targets,
+ which provides a major performance boost for much numerical code. It also
+ promotes shorts to int on 32-bit hosts, etc. LSR now also analyzes pointer
+ expressions (e.g. getelementptrs), as well as integers.
+- The GVN pass now eliminates partial
+ redundancies of loads in simple cases.
+- The Inliner now reuses stack space when
+ inlining similar arrays from multiple callees into one caller.
+- LLVM includes a new experimental Static Single Information (SSI)
+ construction pass.
+
-
New features include:
-- ?
-
+- LLVM has a new "EngineBuilder" class which makes it more obvious how to
+ set up and configure an ExecutionEngine (a JIT or interpreter).
+- The JIT now supports generating more than 16M of code.
+- When configured with --with-oprofile, the JIT can now inform
+ OProfile about JIT'd code, allowing OProfile to get line number and function
+ name information for JIT'd functions.
+- When "libffi" is available, the LLVM interpreter now uses it, which supports
+ calling almost arbitrary external (natively compiled) functions.
+- Clients of the JIT can now register a 'JITEventListener' object to receive
+ callbacks when the JIT emits or frees machine code. The OProfile support
+ uses this mechanism.
-
In addition to a huge array of bug fixes and minor performance tweaks, this
-release includes a few major enhancements and additions to the optimizers:
+
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:
-- ?
+- The llc -asm-verbose option (exposed from llvm-gcc as -dA
+ and clang as -fverbose-asm or -dA) now adds a lot of
+ useful information in comments to
+ the generated .s file. This information includes location information (if
+ built with -g) and loop nest information.
+- The code generator now supports a new MachineVerifier pass which is useful
+ for finding bugs in targets and codegen passes.
+- The Machine LICM is now enabled by default. It hoists instructions out of
+ loops (such as constant pool loads, loads from read-only stubs, vector
+ constant synthesization code, etc.) and is currently configured to only do
+ so when the hoisted operation can be rematerialized.
+- The Machine Sinking pass is now enabled by default. This pass moves
+ side-effect free operations down the CFG so that they are executed on fewer
+ paths through a function.
+- The code generator now performs "stack slot coloring" of register spills,
+ which allows spill slots to be reused. This leads to smaller stack frames
+ in cases where there are lots of register spills.
+- The register allocator has many improvements to take better advantage of
+ commutable operations, various spiller peephole optimizations, and can now
+ coalesce cross-register-class copies.
+- Tblgen now supports multiclass inheritance and a number of new string and
+ list operations like !(subst), !(foreach), !car,
+ !cdr, !null, !if, !cast.
+ These make the .td files more expressive and allow more aggressive factoring
+ of duplication across instruction patterns.
+- Target-specific intrinsics can now be added without having to hack VMCore to
+ add them. This makes it easier to maintain out-of-tree targets.
+- The instruction selector is better at propagating information about values
+ (such as whether they are sign/zero extended etc.) across basic block
+ boundaries.
+- The SelectionDAG datastructure has new nodes for representing buildvector
+ and vector shuffle operations. This
+ makes operations and pattern matching more efficient and easier to get
+ right.
+- The Prolog/Epilog Insertion Pass now has experimental support for performing
+ the "shrink wrapping" optimization, which moves spills and reloads around in
+ the CFG to avoid doing saves on paths that don't need them.
+- LLVM includes new experimental support for writing ELF .o files directly
+ from the compiler. It works well for many simple C testcases, but doesn't
+ support exception handling, debug info, inline assembly, etc.
+- Targets can now specify register allocation hints through
+ MachineRegisterInfo::setRegAllocationHint. A regalloc hint consists
+ of hint type and physical register number. A hint type of zero specifies a
+ register allocation preference. Other hint type values are target specific
+ which are resolved by TargetRegisterInfo::ResolveRegAllocHint. An
+ example is the ARM target which uses register hints to request that the
+ register allocator provide an even / odd register pair to two virtual
+ registers.
+
+
+
New features of the X86 target include:
+
+
+
+
+- SSE 4.2 builtins are now supported.
+- GCC-compatible soft float modes are now supported, which are typically used
+ by OS kernels.
+- X86-64 now models implicit zero extensions better, which allows the code
+ generator to remove a lot of redundant zexts. It also models the 8-bit "H"
+ registers as subregs, which allows them to be used in some tricky
+ situations.
+- X86-64 now supports the "local exec" and "initial exec" thread local storage
+ model.
+- The vector forms of the icmp and fcmp instructions now select to efficient
+ SSE operations.
+- Support for the win64 calling conventions have improved. The primary
+ missing feature is support for varargs function definitions. It seems to
+ work well for many win64 JIT purposes.
+- The X86 backend has preliminary support for mapping address spaces to segment
+ register references. This allows you to write GS or FS relative memory
+ accesses directly in LLVM IR for cases where you know exactly what you're
+ doing (such as in an OS kernel). There are some known problems with this
+ support, but it works in simple cases.
+- The X86 code generator has been refactored to move all global variable
+ reference logic to one place
+ (X86Subtarget::ClassifyGlobalReference) which
+ makes it easier to reason about.
@@ -288,55 +727,170 @@ release includes a few major enhancements and additions to the optimizers:
-
-
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:
+
New features of the PIC16 target include:
+
-- ?
+- Support for floating-point, indirect function calls, and
+ passing/returning aggregate types to functions.
+
- The code generator is able to generate debug info into output COFF files.
+
- Support for placing an object into a specific section or at a specific
+ address in memory.
+
+
Things not yet supported:
+
+
+- Variable arguments.
+- Interrupts/programs.
-
-
New target-specific features include:
+
New features of the ARM target include:
-- ?
+
+- Preliminary support for processors, such as the Cortex-A8 and Cortex-A9,
+that implement version v7-A of the ARM architecture. The ARM backend now
+supports both the Thumb2 and Advanced SIMD (Neon) instruction sets.
+
+- The AAPCS-VFP "hard float" calling conventions are also supported with the
+-float-abi=hard flag.
+
+- The ARM calling convention code is now tblgen generated instead of resorting
+ to C++ code.
+
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:
+
+
+
+- Mips now supports O32 Calling Convention.
+- Many improvements to the 32-bit PowerPC SVR4 ABI (used on powerpc-linux)
+ support, lots of bugs fixed.
+- Added support for the 64-bit PowerPC SVR4 ABI (used on powerpc64-linux).
+ Needs more testing.
+
+
+
-
New features include:
+
+
This release includes a number of new APIs that are used internally, which
+ may also be useful for external clients.
-- ?
+- New
+ PrettyStackTrace class allows crashes of llvm tools (and applications
+ that integrate them) to provide more detailed indication of what the
+ compiler was doing at the time of the crash (e.g. running a pass).
+ At the top level for each LLVM tool, it includes the command line arguments.
+
+- New StringRef
+ and Twine classes
+ make operations on character ranges and
+ string concatenation to be more efficient. StringRef is just a const
+ char* with a length, Twine is a light-weight rope.
+- LLVM has new WeakVH, AssertingVH and CallbackVH
+ classes, which make it easier to write LLVM IR transformations. WeakVH
+ is automatically drops to null when the referenced Value is deleted,
+ and is updated across a replaceAllUsesWith operation.
+ AssertingVH aborts the program if the
+ referenced value is destroyed while it is being referenced. CallbackVH
+ is a customizable class for handling value references. See ValueHandle.h
+ for more information.
+- The new 'Triple
+ ' class centralizes a lot of logic that reasons about target
+ triples.
+- The new '
+ llvm_report_error()' set of APIs allows tools to embed the LLVM
+ optimizer and backend and recover from previously unrecoverable errors.
+- LLVM has new abstractions for atomic operations
+ and reader/writer
+ locks.
+- LLVM has new
+ SourceMgr and SMLoc classes which implement caret
+ diagnostics and basic include stack processing for simple parsers. It is
+ used by tablegen, llvm-mc, the .ll parser and FileCheck.
+
+
+
+
+
+
+
+
+
+
Other miscellaneous features include:
+
+
+- LLVM now includes a new internal 'FileCheck' tool which allows
+ writing much more accurate regression tests that run faster. Please see the
+ FileCheck section of the Testing
+ Guide for more information.
+- LLVM profile information support has been significantly improved to produce
+correct use counts, and has support for edge profiling with reduced runtime
+overhead. Combined, the generated profile information is both more correct and
+imposes about half as much overhead (2.6. from 12% to 6% overhead on SPEC
+CPU2000).
+- The C bindings (in the llvm/include/llvm-c directory) include many newly
+ supported APIs.
+- LLVM 2.6 includes a brand new experimental LLVM bindings to the Ada2005
+ programming language.
+
+- The LLVMC driver has several new features:
+
+ - Dynamic plugins now work on Windows.
+ - New option property: init. Makes possible to provide default values for
+ options defined in plugins (interface to cl::init).
+ - New example: Skeleton, shows how to create a standalone LLVMC-based
+ driver.
+ - New example: mcc16, a driver for the PIC16 toolchain.
+
+
+
Major Changes and Removed Features
@@ -345,12 +899,24 @@ faster:
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 Itanium (IA64) backend has been removed. It was not actively supported
+ and had bitrotted.
+- The BigBlock register allocator has been removed, it had also bitrotted.
+- The C Backend (-march=c) is no longer considered part of the LLVM release
+criteria. We still want it to work, but no one is maintaining it and it lacks
+support for arbitrary precision integers and other important IR features.
+
+- All LLVM tools now default to overwriting their output file, behaving more
+ like standard unix tools. Previously, this only happened with the '-f'
+ option.
+- LLVM build now builds all libraries as .a files instead of some
+ libraries as relinked .o files. This requires some APIs like
+ InitializeAllTargets.h.
+
@@ -358,10 +924,82 @@ from the previous release.
API changes are:
+
- All uses of hash_set and hash_map have been removed from
+ the LLVM tree and the wrapper headers have been removed.
+
- The llvm/Streams.h and DOUT member of Debug.h have been removed. The
+ llvm::Ostream class has been completely removed and replaced with
+ uses of raw_ostream.
+
- LLVM's global uniquing tables for Types and Constants have
+ been privatized into members of an LLVMContext. A number of APIs
+ now take an LLVMContext as a parameter. To smooth the transition
+ for clients that will only ever use a single context, the new
+ getGlobalContext() API can be used to access a default global
+ context which can be passed in any and all cases where a context is
+ required.
+
- The getABITypeSize methods are now called getAllocSize.
+
- The Add, Sub and Mul operators are no longer
+ overloaded for floating-point types. Floating-point addition, subtraction
+ and multiplication are now represented with new operators FAdd,
+ FSub and FMul. In the IRBuilder API,
+ CreateAdd, CreateSub, CreateMul and
+ CreateNeg should only be used for integer arithmetic now;
+ CreateFAdd, CreateFSub, CreateFMul and
+ CreateFNeg should now be used for floating-point arithmetic.
+
- The DynamicLibrary class can no longer be constructed, its functionality has
+ moved to static member functions.
+
- raw_fd_ostream's constructor for opening a given filename now
+ takes an extra Force argument. If Force is set to
+ false, an error will be reported if a file with the given name
+ already exists. If Force is set to true, the file will
+ be silently truncated (which is the behavior before this flag was
+ added).
+
- SCEVHandle no longer exists, because reference counting is no
+ longer done for SCEV* objects, instead const SCEV*
+ should be used.
+
+
- Many APIs, notably llvm::Value, now use the StringRef
+and Twine classes instead of passing const char*
+or std::string, as described in
+the Programmer's Manual. Most
+clients should be unaffected by this transition, unless they are used to
+Value::getName() returning a string. Here are some tips on updating to
+2.6:
+
+ - getNameStr() is still available, and matches the old
+ behavior. Replacing getName() calls with this is an safe option,
+ although more efficient alternatives are now possible.
+
+ - If you were just relying on getName() being able to be sent to
+ a std::ostream, consider migrating
+ to llvm::raw_ostream.
+
+ - If you were using getName().c_str() to get a const
+ char* pointer to the name, you can use getName().data().
+ Note that this string (as before), may not be the entire name if the
+ name contains embedded null characters.
+
+ - If you were using operator + on the result of getName() and
+ treating the result as an std::string, you can either
+ use Twine::str to get the result as an std::string, or
+ could move to a Twine based design.
+
+ - isName() should be replaced with comparison
+ against getName() (this is now efficient).
+
+
-
- ?
+
- The registration interfaces for backend Targets has changed (what was
+previously TargetMachineRegistry). For backend authors, see the Writing An LLVM Backend
+guide. For clients, the notable API changes are:
+
+ - TargetMachineRegistry has been renamed
+ to TargetRegistry.
+
+ - Clients should move to using the TargetRegistry::lookupTarget()
+ function to find targets.
+
+
@@ -379,16 +1017,16 @@ API changes are:
LLVM is known to work on the following platforms:
-- Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) 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
@@ -406,11 +1044,26 @@ portability patches and reports of successful builds or error messages.
-
This section contains significant known problems with the LLVM system,
+
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 for 2.6 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.
+
+
@@ -428,9 +1081,11 @@ components, please contact us on the
LLVMdev list.
-- The MSIL, IA64, Alpha, SPU, MIPS, and PIC16 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.
@@ -450,13 +1105,14 @@ href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list.
- The X86 backend generates inefficient floating point code when configured
to generate code for systems that don't have SSE2.
- Win64 code generation wasn't widely tested. Everything should work, but we
- expect small issues to happen. Also, llvm-gcc cannot build mingw64 runtime
- currently due
+ expect small issues to happen. Also, llvm-gcc cannot build the mingw64
+ runtime currently due
to several
- bugs due to lack of support for the
- 'u' inline assembly constraint and X87 floating point inline assembly.
+
bugs and due to lack of support for
+ the
+ 'u' inline assembly constraint and for X87 floating point inline assembly.
- The X86-64 backend does not yet support the LLVM IR instruction
- va_arg. Currently, the llvm-gcc front-end supports variadic
+ va_arg. Currently, the llvm-gcc and front-ends support variadic
argument constructs on X86-64 by lowering them manually.
@@ -484,14 +1140,14 @@ compilation, and lacks support for debug information.
+- 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.
@@ -504,7 +1160,7 @@ 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).
@@ -518,7 +1174,6 @@ programs compiled with LLVM. Please use more recent versions of QEMU.
-- The O32 ABI is not fully supported.
- 64-bit MIPS targets are not supported yet.
@@ -539,21 +1194,6 @@ appropriate nops inserted to ensure restartability.
-
-
-
-
-
-
-- 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.
-
-
-
-
Known problems with the C back-end
@@ -566,8 +1206,9 @@ appropriate nops inserted to ensure restartability.
inline assembly code.
- The C backend violates the ABI of common
C++ programs, preventing intermixing between C++ compiled by the CBE and
- C++ code compiled with llc or native compilers.
+ C++ code compiled with
llc or native compilers.
- The C backend does not support all exception handling constructs.
+
- The C backend does not support arbitrary precision integers.
@@ -580,10 +1221,6 @@ appropriate nops inserted to ensure restartability.
-
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
@@ -621,10 +1258,8 @@ itself, Qt, Mozilla, etc.
- Fortran support generally works, but there are still several unresolved bugs
- in Bugzilla. Please see the tools/gfortran component for details.
-
-- The Fortran front-end currently does not build on Darwin (without tweaks)
- due to unresolved dependencies on the C front-end.
+ in Bugzilla. Please see the
+ tools/gfortran component for details.
@@ -634,22 +1269,26 @@ itself, Qt, Mozilla, etc.
-The llvm-gcc 4.2 Ada compiler works fairly well, however this is not a mature
-technology and problems should be expected.
+The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
+technology, and problems should be expected.
- 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.
+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).
-- Some gcc specific Ada tests continue to crash the compiler.
-- The -E binder option (exception backtraces)
+(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
@@ -663,6 +1302,20 @@ 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.
+
+