LLVM 2.3 Release Notes

Introduction @@ -35,174 +32,175 @@

This document contains the release notes for the LLVM compiler -infrastructure, release 2.3. 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 2.4. 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.

+ + + +

- Major Changes and Sub-project Status + Sub-project Status Update

- -

This is the fourteenth public release of the LLVM Compiler Infrastructure. -It includes a large number of features and refinements from LLVM 2.2.

+The LLVM 2.4 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. +

-Major Changes in LLVM 2.3 +Clang: C/C++/Objective-C Frontend Toolkit

LLVM 2.3 no longer supports llvm-gcc 4.0, it has been replaced with - llvm-gcc 4.2.

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.

LLVM 2.3 no longer includes the llvm-upgrade tool. It was useful - for upgrading LLVM 1.9 files to LLVM 2.x syntax, but you can always use a - previous LLVM release to do this. One nice impact of this is that the LLVM - regression test suite no longer depends on llvm-upgrade, which makes it run - faster.

Clang, in conjunction with the ccc driver, is now usable as a +replacement for gcc for building some small- to medium-sized C applications. +Additionally, Clang now has code generation support for Objective-C on Mac OS X +platform. Major highlights include:

The llvm2cpp tool has been folded into llc, use - llc -march=cpp instead of llvm2cpp.

Clang/ccc pass almost all of the LLVM test suite on Mac OS X and Linux +on the 32-bit x86 architecture. This includes significant C +applications such as sqlite3, +lua, and +Clam AntiVirus.
Clang can build the majority of Objective-C examples shipped with the +Mac OS X Developer Tools.

LLVM API Changes:

Clang code generation still needs considerable testing and development, +however. Some areas under active development include:

Several core LLVM IR classes have migrated to use the - 'FOOCLASS::Create(...)' pattern instead of 'new - FOOCLASS(...)' (e.g. where FOOCLASS=BasicBlock). We hope to - standardize on FOOCLASS::Create for all IR classes in the future, - but not all of them have been moved over yet.
LLVM 2.3 renames the LLVMBuilder and LLVMFoldingBuilder classes to - IRBuilder. -
MRegisterInfo was renamed to - - TargetRegisterInfo.
The MappedFile class is gone, please use - - MemoryBuffer instead.
The '-enable-eh' flag to llc has been removed. Now code should - encode whether it is safe to omit unwind information for a function by - tagging the Function object with the 'nounwind' attribute.
The ConstantFP::get method that uses APFloat now takes one argument - instead of two. The type argument has been removed, and the type is - now inferred from the size of the given APFloat value.
Improved support for C and Objective-C features, for example + variable-length arrays, va_arg, exception handling (Obj-C), and garbage + collection (Obj-C).
ABI compatibility, especially for platforms other than 32-bit + x86.

-Other LLVM Sub-Projects +Clang Static Analyzer

-The core LLVM 2.3 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 new vmkit Project -and the Clang Project. -

- -

-vmkit -

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 "vmkit" project is a new addition to the LLVM family. It 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 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 JVM, called JnJVM, executes real-world applications such as Apache -projects (e.g. Felix and Tomcat) and the SpecJVM98 benchmark. It uses the GNU -Classpath project for the base classes. The CLI implementation, called N3, is -its in early stages but can execute simple applications and the "pnetmark" -benchmark. It uses the pnetlib project as its core library.

- -

The 'vmkit' VMs compare in performance with industrial and top open-source -VMs on scientific applications. Besides the JIT, the VMs use many features of -the LLVM framework, including the standard set of optimizations, atomic -operations, custom function provider and memory manager for JITed methods, and -specific virtual machine optimizations. vmkit is not an official part of LLVM -2.3 release. It is publicly available under the LLVM license and can be -downloaded from: -

- -

svn co http://llvm.org/svn/llvm-project/vmkit/trunk vmkit

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!

-Clang +

+VMKit: JVM/CLI Virtual Machine Implementation

+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 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.

Following LLVM 2.4, VMKit has its first release 0.24 that you can find on its +webpage. The release includes +bug fixes, cleanup and new features. The major changes are:

At this point, Clang is most useful if you are interested in source-to-source -transformations (such as refactoring) and other source-level tools for C and -Objective-C. Clang now also includes tools for turning C code into pretty HTML, -and includes a new static -analysis tool in development. This tool focuses on automatically finding -bugs in C and Objective-C code.

Support for generics in the .Net virtual machine.
Initial support for the Mono class libraries.
Support for MacOSX/x86, following LLVM's support for exceptions in +JIT on MacOSX/x86.
A new vmkit driver: a program to run java or .net applications. The driver +supports llvm command line arguments including the new "-fast" option.
A new memory allocation scheme in the JVM that makes unloading a +class loader very fast.
VMKit now follows the LLVM Makefile machinery.

- What's New? + What's New in LLVM?

LLVM 2.3 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. +

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.

@@ -213,52 +211,29 @@ this section.

LLVM 2.3 includes several major new capabilities:

LLVM 2.4 includes several major new capabilities:

The biggest change in LLVM 2.3 is Multiple Return Value (MRV) support. - MRVs allow LLVM IR to directly represent functions that return multiple - values without having to pass them "by reference" in the LLVM IR. This - allows a front-end to generate more efficient code, as MRVs are generally - returned in registers if a target supports them. See the LLVM IR Reference for more details.
- -
MRVs are fully supported in the LLVM IR, but are not yet fully supported in - on all targets. However, it is generally safe to return up to 2 values from - a function: most targets should be able to handle at least that. MRV - support is a critical requirement for X86-64 ABI support, as X86-64 requires - the ability to return multiple registers from functions, and we use MRVs to - accomplish this in a direct way.
LLVM 2.3 includes a complete reimplementation of the "llvmc" - tool. It is designed to overcome several problems with the original - llvmc and to provide a superset of the features of the - 'gcc' driver.
- -
The main features of llvmc2 are: -
- Extended handling of command line options and smart rules for - dispatching them to different tools.
- Flexible (and extensible) rules for defining different tools.
- The different intermediate steps performed by tools are represented - as edges in the abstract graph.
- The 'language' for driver behavior definition is tablegen and thus - it's relatively easy to add new features.
- The definition of driver is transformed into set of C++ classes, thus - no runtime interpretation is needed.
-
LLVM 2.3 includes a completely rewritten interface for Link Time Optimization. This interface - is written in C, which allows for easier integration with C code bases, and - incorporates improvements we learned about from the first incarnation of the - interface.
The Kaleidoscope tutorial now - includes a "port" of the tutorial that uses the Ocaml bindings to implement - the Kaleidoscope language.
The most visible end-user change in LLVM 2.4 is that it includes many +optimizations and changes to make -O0 compile times much faster. You should see +improvements in speed on the order of 30% (or more) than in LLVM 2.3. There are +many pieces to this change described in more detail below. The speedups and new +components can also be used for JIT compilers that want fast +compilation.
The biggest change to the LLVM IR is that Multiple Return Values (which +were introduced in LLVM 2.3) have been generalized to full support for "First +Class Aggregate" values in LLVM 2.4. This means that LLVM IR supports using +structs and arrays as values in a function. This capability is mostly useful +for front-end authors, who prefer to treat things like complex numbers, simple +tuples, dope vectors, etc., as Value*'s instead of as a tuple of Value*'s or as +memory values. Bitcode files from LLVM 2.3 will automatically migrate to the +general representation.
LLVM 2.4 also includes an initial port for the PIC16 microprocessor. This +target only has support for 8 bit registers, and a number of other crazy +constraints. While the port is still in early development stages, it shows some +interesting things you can do with LLVM.

@@ -272,20 +247,34 @@ this section.

LLVM 2.3 fully supports the llvm-gcc 4.2 front-end, and includes support -for the C, C++, Objective-C, Ada, and Fortran front-ends.

LLVM fully supports the llvm-gcc 4.2 front-end, which marries the GCC +front-ends and driver with the LLVM optimizer and code generator. It currently +includes support for the C, C++, Objective-C, Ada, and Fortran front-ends.

llvm-gcc 4.2 includes numerous fixes to better support the Objective-C -front-end. Objective-C now works very well on Mac OS/X.
Fortran EQUIVALENCEs are now supported by the gfortran -front-end.
llvm-gcc 4.2 includes many other fixes which improve conformance with the -relevant parts of the GCC testsuite.
LLVM 2.4 supports the full set of atomic __sync_* builtins. LLVM +2.3 only supported those used by OpenMP, but 2.4 supports them all. Note that +while llvm-gcc supports all of these builtins, not all targets do. X86 support +them all in both 32-bit and 64-bit mode and PowerPC supports them all except for +the 64-bit operations when in 32-bit mode.
llvm-gcc now supports an -flimited-precision option, which tells +the compiler that it is okay to use low-precision approximations of certain libm +functions (like exp, log, etc). This allows you to get high +performance if you only need (say) 12-bits of precision.
llvm-gcc now supports a C language extension known as "Blocks". +This feature is similar to nested functions and closures, but does not +require stack trampolines (with most ABIs), and supports returning closures +from functions that define them. Note that actually using Blocks +requires a small runtime that is not included with llvm-gcc.
llvm-gcc now supports a new -flto option. On systems that support +transparent Link Time Optimization (currently Darwin systems with Xcode 3.1 and +later) this allows the use of LTO with other optimization levels like -Os. +Previously, LTO could only be used with -O4, which implied optimizations in +-O3 that can increase code size.

@@ -297,23 +286,49 @@ relevant parts of the GCC testsuite.

New features include: -

New features include:

LLVM IR now directly represents "common" linkage, instead of representing it -as a form of weak linkage.
A major change to the Use class landed, which shrank it by 25%. Since +this is a pervasive part of the LLVM, it ended up reducing the memory use of +LLVM IR in general by 15% for most programs.
LLVM IR now has support for atomic operations, and this functionality can be -accessed through the llvm-gcc "__sync_synchronize", -"__sync_val_compare_and_swap", and related builtins. Support for -atomics are available in the Alpha, X86, X86-64, and PowerPC backends.
Values with no names are now pretty printed by llvm-dis more +nicely. They now print as "%3 = add i32 %A, 4" instead of +"add i32 %A, 4 ; <i32>:3", which makes it much easier to read. +
The C and Ocaml bindings have extended to cover pass managers, several -transformation passes, iteration over the LLVM IR, target data, and parameter -attribute lists.
LLVM 2.4 includes some changes for better vector support. First, the shift +operations (shl, ashr, and lshr) now all support +vectors and do an element-by-element shift (shifts of the whole vector can be +accomplished by bitcasting the vector to <1 x i128>, for example). Second, +there is initial support in development for vector comparisons with the +fcmp/icmp +instructions. These instructions compare two vectors and return a vector of +i1's for each result. Note that there is very little codegen support +available for any of these IR features though.
A new DebugInfoBuilder class is available, which makes it much +easier for front-ends to create debug info descriptors, similar to the way that +IRBuilder makes it easier to create LLVM IR.
The IRBuilder class is now parameterized by a class responsible +for constant folding. The default ConstantFolder class does target independent +constant folding. The NoFolder class does no constant folding at all, which is +useful when learning how LLVM works. The TargetFolder class folds the most, +doing target dependent constant folding.
LLVM now supports "function attributes", which allow us to separate return +value attributes from function attributes. LLVM now supports attributes on a +function itself, a return value, and its parameters. New supported function +attributes include noinline/alwaysinline and the opt-size flag, +which says the function should be optimized for code size.
LLVM IR now directly represents "common" linkage, instead of + representing it as a form of weak linkage.

- +

@@ -323,66 +338,45 @@ attribute lists.

In addition to a huge array of bug fixes and minor performance tweaks, the -LLVM 2.3 optimizers support a few major enhancements:

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:

Loop index set splitting on by default. -This transformation hoists conditions from loop bodies and reduces a loop's -iteration space to improve performance. For example,
+
The Global Value Numbering (GVN) pass now does local Partial Redundancy +Elimination (PRE) to eliminate some partially redundant expressions in cases +where doing so won't grow code size.

-for (i = LB; i < UB; ++i)
-  if (i <= NV)
-    LOOP_BODY
-

LLVM 2.4 includes a new loop deletion pass (which removes output-free +provably-finite loops) and a rewritten Aggressive Dead Code Elimination (ADCE) +pass that no longer uses control dependence information. These changes speed up +the optimizer and also prevent it from deleting output-free infinite +loops.

is transformed into:

The new AddReadAttrs pass works out which functions are read-only or +read-none (these correspond to 'pure' and 'const' in GCC) and marks them +with the appropriate attribute.

-NUB = min(NV+1, UB)
-for (i = LB; i < NUB; ++i)
-  LOOP_BODY
-

LLVM 2.4 now includes a new SparsePropagation framework, which makes it +trivial to build lattice-based dataflow solvers that operate over LLVM IR. Using +this interface means that you just define objects to represent your lattice +values and the transfer functions that operate on them. It handles the +mechanics of worklist processing, liveness tracking, handling PHI nodes, +etc.
LLVM now includes a new memcpy optimization pass which removes -dead memcpy calls, unneeded copies of aggregates, and performs -return slot optimization. The LLVM optimizer now notices long sequences of -consecutive stores and merges them into memcpy's where profitable.
Alignment detection for vector memory references and for memcpy and -memset is now more aggressive.
The Aggressive Dead Code Elimination (ADCE) optimization has been rewritten -to make it both faster and safer in the presence of code containing infinite -loops. Some of its prior functionality has been factored out into the loop -deletion pass, which is safe for infinite loops. The new ADCE pass is -no longer based on control dependence, making it run faster.
The 'SimplifyLibCalls' pass, which optimizes calls to libc and libm - functions for C-based languages, has been rewritten to be a FunctionPass - instead a ModulePass. This allows it to be run more often and to be - included at -O1 in llvm-gcc. It was also extended to include more - optimizations and several corner case bugs were fixed.
LLVM now includes a simple 'Jump Threading' pass, which attempts to simplify - conditional branches using information about predecessor blocks, simplifying - the control flow graph. This pass is pretty basic at this point, but - catches some important cases and provides a foundation to build on.
Several corner case bugs which could lead to deleting volatile memory - accesses have been fixed.
The Loop Strength Reduction and induction variable optimization passes have +several improvements to avoid inserting MAX expressions, to optimize simple +floating point induction variables and to analyze trip counts of more +loops.
Various helper functions (ComputeMaskedBits, ComputeNumSignBits, etc) were +pulled out of the Instruction Combining pass and put into a new +ValueTracking.h header, where they can be reused by other passes.
The tail duplication pass has been removed from the standard optimizer +sequence used by llvm-gcc. This pass still exists, but the benefits it once +provided are now achieved by other passes.
Several optimizations have been sped up, leading to faster code generation - with the same code quality.

@@ -394,50 +388,47 @@ no longer based on control dependence, making it run faster.

We put a significant amount of work into the code generator infrastructure, +

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 code generator now has support for carrying information about memory - references throughout the entire code generation process, via the - - MachineMemOperand class. In the future this will be used to improve - both pre-pass and post-pass scheduling, and to improve compiler-debugging - output.
The target-independent code generator infrastructure now uses LLVM's - APInt - class to handle integer values, which allows it to support integer types - larger than 64 bits (for example i128). Note that support for such types is - also dependent on target-specific support. Use of APInt is also a step - toward support for non-power-of-2 integer sizes.
LLVM 2.3 includes several compile time speedups for code with large basic - blocks, particularly in the instruction selection phase, register - allocation, scheduling, and tail merging/jump threading.
The target-independent code generator supports (and the X86 backend + currently implements) a new interface for "fast" instruction selection. This + interface is optimized to produce code as quickly as possible, sacrificing + code quality to do it. This is used by default at -O0 or when using + "llc -fast" on X86. It is straight-forward to add support for + other targets if faster -O0 compilation is desired.
In addition to the new 'fast' instruction selection path, many existing + pieces of the code generator have been optimized in significant ways. + SelectionDAG's are now pool allocated and use better algorithms in many + places, the ".s" file printers now use raw_ostream to emit text much faster, + etc. The end result of these improvements is that the compiler also takes + substantially less time to generate code that is just as good (and often + better) than before.
Each target has been split to separate the ".s" file printing logic from the + rest of the target. This enables JIT compilers that don't link in the + (somewhat large) code and data tables used for printing a ".s" file.
The code generator now includes a "stack slot coloring" pass, which packs + together individual spilled values into common stack slots. This reduces + the size of stack frames with many spills, which tends to increase L1 cache + effectiveness.
Various pieces of the register allocator (e.g. the coalescer and two-address + operation elimination pass) now know how to rematerialize trivial operations + to avoid copies and include several other optimizations.
The graphs produced by + the llc -view-*-dags options are now significantly prettier and + easier to read.
LLVM 2.4 includes a new register allocator based on Partitioned Boolean + Quadratic Programming (PBQP). This register allocator is still in + development, but is very simple and clean.
LLVM 2.3 includes several improvements which make llc's - --view-sunit-dags visualization of scheduling dependency graphs - easier to understand.
The code generator allows targets to write patterns that generate subreg - references directly in .td files now.
memcpy lowering in the backend is more aggressive, particularly for - memcpy calls introduced by the code generator when handling - pass-by-value structure argument copies.
Inline assembly with multiple register results now returns those results - directly in the appropriate registers, rather than going through memory. - Inline assembly that uses constraints like "ir" with immediates now use the - 'i' form when possible instead of always loading the value in a register. - This saves an instruction and reduces register use.
Added support for PIC/GOT style tail calls on X86/32 and initial - support for tail calls on PowerPC 32 (it may also work on PowerPC 64 but is - not thoroughly tested).

@@ -445,7 +436,7 @@ faster:

-X86/X86-64 Specific Improvements +Target Specific Improvements

@@ -453,90 +444,131 @@ faster:

llvm-gcc's X86-64 ABI conformance is far improved, particularly in the - area of passing and returning structures by value. llvm-gcc compiled code - now interoperates very well on X86-64 systems with other compilers.
Support for Win64 was added. This includes code generation itself, JIT - support, and necessary changes to llvm-gcc.
The LLVM X86 backend now supports the support SSE 4.1 instruction set, and - the llvm-gcc 4.2 front-end supports the SSE 4.1 compiler builtins. Various - generic vector operations (insert/extract/shuffle) are much more efficient - when SSE 4.1 is enabled. The JIT automatically takes advantage of these - instructions, but llvm-gcc must be explicitly told to use them, e.g. with - -march=penryn.
The X86 backend now does a number of optimizations that aim to avoid - converting numbers back and forth from SSE registers to the X87 floating - point stack. This is important because most X86 ABIs require return values - to be on the X87 Floating Point stack, but most CPUs prefer computation in - the SSE units.
The X86 backend supports stack realignment, which is particularly useful for - vector code on OS's without 16-byte aligned stacks, such as Linux and - Windows.
The X86 backend now supports the "sseregparm" options in GCC, which allow - functions to be tagged as passing floating point values in SSE - registers.
Exception handling is supported by default on Linux/x86-64.
Position Independent Code (PIC) is now supported on Linux/x86-64.
@llvm.frameaddress now supports getting the frame address of stack frames + > 0 on x86/x86-64.
MIPS has improved a lot since last release, the most important changes + are: Little endian support, floating point support, allegrex core and + intrinsics support. O32 ABI is improved but isn't complete. The EABI + was implemented and is fully supported. We also have support for small + sections and gp_rel relocation for its access, a threshold in bytes can be + specified through command line.
The PowerPC backend now supports trampolines.

Trampolines (taking the address of a nested function) now work on - Linux/X86-64.

__builtin_prefetch is now compiled into the appropriate prefetch - instructions instead of being ignored.

128-bit integers are now supported on X86-64 targets. This can be used - through __attribute__((TImode)) in llvm-gcc.

+ +

+Other Improvements +

The register allocator can now rematerialize PIC-base computations, which is - an important optimization for register use.

New features include: +

The "t" and "f" inline assembly constraints for the X87 floating point stack - now work. However, the "u" constraint is still not fully supported.

llvmc2 (the generic compiler driver) gained plugin + support. It is now easier to experiment with llvmc2 and + build your own tools based on it.
LLVM 2.4 includes a number of new generic algorithms and data structures, + including a scoped hash table, 'immutable' data structures, a simple + free-list manager, and a raw_ostream class. + The raw_ostream class and + format allow for efficient file output, and various pieces of LLVM + have switched over to use it. The eventual goal is to eliminate + use of std::ostream in favor of it.
LLVM 2.4 includes an optional build system based on CMake. It + still is in its early stages but can be useful for Visual C++ + users who can not use the Visual Studio IDE.

- +

-Other Target Specific Improvements +Major Changes and Removed Features

New target-specific features include: -

+ +

If you're already an LLVM user or developer with out-of-tree changes based +on LLVM 2.3, this section lists some "gotchas" that you may run into upgrading +from the previous release.

The LLVM C backend now supports vector code.
The Cell SPU backend includes a number of improvements. It generates better - code and its stability/completeness is improving.

- -

The LLVM IR generated by llvm-gcc no longer names all instructions. This + makes it run faster, but may be more confusing to some people. If you + prefer to have names, the 'opt -instnamer' pass will add names to + all instructions.

The LoadVN and GCSE passes have been removed from the tree. They are + obsolete and have been replaced with the GVN and MemoryDependence passes. +

+ - -

-Other Improvements -

New features include: -

In addition, many APIs have changed in this release. Some of the major LLVM +API changes are:

LLVM now builds with GCC 4.3.
Bugpoint now supports running custom scripts (with the -run-custom - option) to determine how to execute the command and whether it is making - forward process.
Now, function attributes and return value attributes are managed +separately. Interface exported by ParameterAttributes.h header is now +exported by Attributes.h header. The new attributes interface changes are: +
- getParamAttrs method is now replaced by +getParamAttributes, getRetAttributes and +getFnAttributes methods.
- Return value attributes are stored at index 0. Function attributes are +stored at index ~0U. Parameter attributes are stored at index that matches +parameter number.
- ParamAttr namespace is now renamed as Attribute.
- The name of the class that manages reference count of opaque +attributes is changed from PAListPtr to AttrListPtr.
- ParamAttrsWithIndex is now renamed as AttributeWithIndex. +
- +
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".
The APIs to create various instructions have changed from lower case + "create" methods to upper case "Create" methods (e.g. + BinaryOperator::create). LLVM 2.4 includes both cases, but the + lower case ones are removed in mainline (2.5 and later), please migrate.
Various header files like "llvm/ADT/iterator" were given a ".h" suffix. + Change your code to #include "llvm/ADT/iterator.h" instead.
The getresult instruction has been removed and replaced with the + extractvalue instruction. This is part of support for first class + aggregates.
In the code generator, many MachineOperand predicates were renamed to be + shorter (e.g. isFrameIndex() -> isFI()), + SDOperand was renamed to SDValue (and the "Val" + member was changed to be the getNode() accessor), and the + MVT::ValueType enum has been replaced with an "MVT" + struct. The getSignExtended and getValue methods in the + ConstantSDNode class were renamed to getSExtValue and + getZExtValue respectively, to be more consistent with + the ConstantInt class.

+ +

Portability and Supported Platforms @@ -548,10 +580,10 @@ faster:

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 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 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++).

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.

@@ -598,7 +629,7 @@ components, please contact us on the LLVMdev list.

The MSIL, IA64, Alpha, SPU, and MIPS backends are experimental.
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.

@@ -625,8 +656,6 @@ href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list.

to several bugs due to lack of support for the 'u' inline assembly constraint and X87 floating point inline assembly. -

The X86-64 backend does not yet support position-independent code (PIC) - generation on Linux targets.

The X86-64 backend does not yet support the LLVM IR instruction va_arg. Currently, the llvm-gcc front-end supports variadic argument constructs on X86-64 by lowering them manually.

@@ -682,6 +711,20 @@ programs compiled with LLVM. Please use more recent versions of QEMU.

+ Known problems with the MIPS back-end +

+ +

The O32 ABI is not fully supported.
64-bit MIPS targets are not supported yet.

+ +

Known problems with the Alpha back-end @@ -707,7 +750,7 @@ 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.

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 @@ -765,13 +808,26 @@ tested and works for a number of non-trivial programs, including LLVM itself, Qt, Mozilla, etc.

Exception handling works well on the X86 and PowerPC targets, including -X86-64 darwin. This works when linking to a libstdc++ compiled by GCC. It is -supported on X86-64 linux, but that is disabled by default in this release.
Exception handling works well on the X86 and PowerPC targets. Currently + only Linux and Darwin targets are supported (both 32 and 64 bit).

+ +

+ Known problems with the llvm-gcc Fortran front-end +

+ +

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.

@@ -788,11 +844,10 @@ 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 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) does not work and will result in programs crashing if an exception is raised. Workaround: do not use -E.

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