This document contains the release notes for the LLVM Compiler
-Infrastructure, release 2.7. 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.
@@ -59,10 +59,6 @@ main LLVM web page, this document applies to the
next release, not the
current one. To see the release notes for a specific release, please see the
releases page.
-
-
FIXME: llvm.org moved to new server, mention new logo, Ted and Doug new code
- owners.
-
@@ -71,30 +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, SCCVN, GEPSplitterPass
+ ABCD, GEPSplitterPass
MSIL backend?
lib/Transforms/Utils/SSI.cpp -> ABCD depends on it.
-->
-
@@ -105,7 +93,7 @@ Almost dead code.
-The LLVM 2.7 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
@@ -122,26 +110,49 @@ development. Here we include updates on these subprojects.
-
The Clang project is ...
+
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:
-- FIXME: C++! Include a link to cxx_compatibility.html
-
-- FIXME: Static Analyzer improvements?
+
+- C++ Support: Clang is now capable of self-hosting! While still
+alpha-quality, Clang's C++ support has matured enough to build LLVM and Clang,
+and C++ is now enabled by default. See the Clang C++ compatibility
+page for common C++ migration issues.
+
+- Objective-C: Clang now includes experimental support for an updated
+Objective-C ABI on non-Darwin platforms. This includes support for non-fragile
+instance variables and accelerated proxies, as well as greater potential for
+future optimisations. The new ABI is used when compiling with the
+-fobjc-nonfragile-abi and -fgnu-runtime options. Code compiled with these
+options may be mixed with code compiled with GCC or clang using the old GNU ABI,
+but requires the libobjc2 runtime from the GNUstep project.
+
+- New warnings: Clang contains a number of new warnings, including
+control-flow warnings (unreachable code, missing return statements in a
+non-
void
function, etc.), sign-comparison warnings, and improved
+format-string warnings.
- CIndex API and Python bindings: Clang now includes a C API as part of the
-CIndex library. Although we make make some changes to the API in the future, it
+CIndex library. Although we may make some changes to the API in the future, it
is intended to be stable and has been designed for use by external projects. See
the Clang
doxygen CIndex
-documentation for more details. The CIndex API also includings an preliminary
+documentation for more details. The CIndex API also includes a preliminary
set of Python bindings.
- ARM Support: Clang now has ABI support for both the Darwin and Linux ARM
ABIs. Coupled with many improvements to the LLVM ARM backend, Clang is now
-suitable for use as a a beta quality ARM compiler.
+suitable for use as a beta quality ARM compiler.
+
@@ -152,13 +163,18 @@ suitable for use as a a beta quality ARM compiler.
-
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 sprouted legs and...
+
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.
+
@@ -215,7 +231,8 @@ libgcc routines).
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.
@@ -244,12 +261,11 @@ becomes llvm-gcc-4.5!
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.
+supported, and only on linux and darwin (darwin needs an additional gcc patch).
-DragonEgg has not yet been released. Once gcc-4.5 has been released, dragonegg
-will probably be released as part of the following LLVM release.
+DragonEgg is a new project which is seeing its first release with llvm-2.7.
@@ -262,9 +278,27 @@ will probably be released as part of the following LLVM release.
-The LLVM Machine Code (MC) Toolkit project is ...
+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.
+
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
+
+
@@ -281,53 +315,6 @@ The LLVM Machine Code (MC) Toolkit project is ...
projects that have already been updated to work with LLVM 2.7.
-
-
-
Roadsend PHP
@@ -400,17 +366,38 @@ compiler.
-Need update.
-
+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.
@@ -421,54 +408,69 @@ code.-->
-Need update.
-
+code.
+
+
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).
-
-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.
+
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.
+
+
-
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.
+
+
+
+
+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.
+
-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.
-
+
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.
+
@@ -489,68 +491,82 @@ in this section.
-
LLVM 2.7 includes several major new capabilities:
+
In addition to changes to the code, between LLVM 2.6 and 2.7, a number of
+organization changes have happened:
+
-- ...
+- LLVM has a new official logo!
+
+- Ted Kremenek and Doug Gregor have stepped forward as Code Owners of the
+ Clang static analyzer and the Clang frontend, respectively.
+
+- LLVM now has an official Blog at
+ http://blog.llvm.org. This is a great way
+ to learn about new LLVM-related features as they are implemented. Several
+ features in this release are already explained on the blog.
+
+- The LLVM web pages are now checked into the SVN server, in the "www",
+ "www-pubs" and "www-releases" SVN modules. Previously they were hidden in a
+ largely inaccessible old CVS server.
+
+- llvm.org is now hosted on a new (and much
+ faster) server. It is still graciously hosted at the University of Illinois
+ of Urbana Champaign.
+
+
+
+
-Extensible metadata solid.
-
-Debug info improvements: using metadata instead of llvm.dbg global variables.
-This brings several enhancements including improved compile times.
-
-New instruction selector.
-GHC Haskell ABI/ calling conv support.
-Pre-Alpha support for unions in IR.
-New InlineHint and StackAlignment function attributes
-Code generator MC'ized except for debug info and EH.
-New SCEV AA pass: -scev-aa
-Inliner reuses arrays allocas when inlining multiple callers to reduce stack usage.
-MC encoding and disassembler apis.
-Optimal Edge Profiling?
-Instcombine is now a library, has its own IRBuilder to simplify itself.
-New llvm/Support/Regex.h API. FileCheck now does regex's
-Many subtle pointer invalidation bugs in Callgraph have been fixed and it now uses asserting value handles.
-MC Disassembler (with blog post), MCInstPrinter. Many X86 backend and AsmPrinter simplifications
-Various tools like llc and opt now read either .ll or .bc files as input.
-Malloc and free instructions got removed, along with LowerAllocations pass.
-compiler-rt support for ARM.
-completely llvm-gcc NEON support.
-Can transcode from GAS to intel syntax with "llvm-mc foo.s -output-asm-variant=1"
-JIT debug information with GDB 7.0
-New CodeGen Level CSE
-CMake can now run tests, what other improvements?
-ARM/Thumb using reg scavenging for stack object address materialization (PEI).
-New SSAUpdater and MachineSSAUpdater classes for unstructured ssa updating,
- changed jump threading, GVN, etc to use it which simplified them and speed
- them up.
-Combiner-AA improvements, why not on by default?
-Pre-regalloc tail duplication
-x86 sibcall optimization
-New LSR with full strength reduction mode
-The most awesome sext / zext optimization pass. ?
-
-The ARM backend now has good support for ARMv4 backend (tested on StrongARM
- hardware), previously only supported ARMv4T and newer.
-
-
-
-Defaults to RTTI off, packagers should build with make REQUIRE_RTTI=1.
-CondProp pass removed (functionality merged into jump threading).
-AndersAA got removed (from 2.7 or mainline?)
-PredSimplify, LoopVR, GVNPRE got removed.
-LLVM command line tools now overwrite their output, before they would only do this with -f.
-DOUT removed, use DEBUG(errs() instead.
-Much stuff converted to use raw_ostream instead of std::ostream.
-TargetAsmInfo renamed to MCAsmInfo
-llvm/ADT/iterator.h gone.
+
+
LLVM 2.7 includes several major new capabilities:
+
+
+- 2.7 includes initial support for the MicroBlaze target.
+ MicroBlaze is a soft processor core designed for Xilinx FPGAs.
+
+- 2.7 includes a new LLVM IR "extensible metadata" feature. This feature
+ supports many different use cases, including allowing front-end authors to
+ encode source level information into LLVM IR, which is consumed by later
+ language-specific passes. This is a great way to do high-level optimizations
+ like devirtualization, type-based alias analysis, etc. See the
+ Extensible Metadata Blog Post for more information.
+
+- 2.7 encodes debug information
+in a completely new way, built on extensible metadata. The new implementation
+is much more memory efficient and paves the way for improvements to optimized
+code debugging experience.
+
+- 2.7 now directly supports taking the address of a label and doing an
+ indirect branch through a pointer. This is particularly useful for
+ interpreter loops, and is used to implement the GCC "address of label"
+ extension. For more information, see the
+Address of Label and Indirect Branches in LLVM IR Blog Post.
+
+
- 2.7 is the first release to start supporting APIs for assembling and
+ disassembling target machine code. These APIs are useful for a variety of
+ low level clients, and are surfaced in the new "enhanced disassembly" API.
+ For more information see the The X86
+ Disassembler Blog Post for more information.
+
+- 2.7 includes major parts of the work required by the new MC Project,
+ see the MC update above for more information.
+
+
@@ -564,7 +580,30 @@ llvm/ADT/iterator.h gone.
expose new optimization opportunities:
-- ...
+- LLVM IR now supports a 16-bit "half float" data type through two new intrinsics and APFloat support.
+- LLVM IR supports two new function
+ attributes: inlinehint and alignstack(n). The former is a hint to the
+ optimizer that a function was declared 'inline' and thus the inliner should
+ weight it higher when considering inlining it. The later
+ indicates to the code generator that the function diverges from the platform
+ ABI on stack alignment.
+- The new llvm.objectsize intrinsic
+ allows the optimizer to infer the sizes of memory objects in some cases.
+ This intrinsic is used to implement the GCC __builtin_object_size
+ extension.
+- LLVM IR now supports marking load and store instructions with "non-temporal" hints (building on the new
+ metadata feature). This hint encourages the code
+ generator to generate non-temporal accesses when possible, which are useful
+ for code that is carefully managing cache behavior. Currently, only the
+ X86 backend provides target support for this feature.
+
+- LLVM 2.7 has pre-alpha support for unions in LLVM IR.
+ Unfortunately, this support is not really usable in 2.7, so if you're
+ interested in pushing it forward, please help contribute to LLVM mainline.
+
@@ -581,12 +620,51 @@ release includes a few major enhancements and additions to the optimizers:
-
New features of the PIC16 target include:
-
-
-
-
-
Things not yet supported:
-
-
-- Variable arguments.
-- Interrupts/programs.
@@ -678,25 +783,31 @@ it run faster:
-
New features of other targets include:
-
+
Atomic builtins are now supported for ARMv6 and ARMv7 (__sync_synchronize,
+ __sync_fetch_and_add, etc.).
-
+
@@ -711,7 +822,34 @@ it run faster:
In addition, many APIs have changed in this release. Some of the major LLVM
API changes are:
-- 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).
@@ -1005,9 +1144,6 @@ appropriate nops inserted to ensure restartability.
supported on some targets (these are used when you take the address of a
nested function).
-If you run into GCC extensions which are not supported, please let us know.
-
-