LLVM 2.8 Release Notes

X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=docs%2FReleaseNotes.html;h=2f83b9447d1d98613e3ac0451f8aef501a58bb0f;hb=2bf4b54a800c2dd44c0a5939fe629ea120bee2ad;hp=2573dc8821305b201f0d677dea7153f37c55bd18;hpb=eb6f5936a131e9a4cb1b7d67d02df09b95dd5ebc;p=oota-llvm.git diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html index 2573dc88213..2f83b9447d1 100644 --- a/docs/ReleaseNotes.html +++ b/docs/ReleaseNotes.html @@ -3,6 +3,7 @@ + LLVM 2.8 Release Notes @@ -67,7 +68,6 @@ current one. To see the release notes for a specific release, please see the 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. GEPSplitterPass --> @@ -82,79 +82,6 @@ Almost dead code. - -

@@ -192,10 +119,27 @@ production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86

In the LLVM 2.8 time-frame, the Clang team has made many improvements:

Surely these guys have done something
X86-64 abi improvements? Did they make it in?

Clang C++ is now feature-complete with respect to the ISO C++ 1998 and 2003 standards.
Added support for Objective-C++.
Clang now uses LLVM-MC to directly generate object code and to parse inline assembly (on Darwin).
Introduced many new warnings, including -Wmissing-field-initializers, -Wshadow, -Wno-protocol, -Wtautological-compare, -Wstrict-selector-match, -Wcast-align, -Wunused improvements, and greatly improved format-string checking.
Introduced the "libclang" library, a C interface to Clang intended to support IDE clients.
Added support for #pragma GCC visibility, #pragma align, and others.
Added support for SSE, AVX, ARM NEON, and AltiVec.
Improved support for many Microsoft extensions.
Implemented support for blocks in C++.
Implemented precompiled headers for C++.
Improved abstract syntax trees to retain more accurate source information.
Added driver support for handling LLVM IR and bitcode files directly.
Major improvements to compiler correctness for exception handling.
Improved generated code quality in some areas: +
- Good code generation for X86-32 and X86-64 ABI handling.
- Improved code generation for bit-fields, although important work remains.
+

@@ -218,48 +162,6 @@ production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86 - -

-VMKit: JVM/CLI Virtual Machine Implementation -

- -

-The VMKit project is an implementation of -a JVM and a CLI Virtual Machine (Microsoft .NET is an -implementation of the CLI) using LLVM for static and just-in-time -compilation.

- -

With the release of LLVM 2.8, ...

- -

- - - -

-compiler-rt: Compiler Runtime Library -

- -

-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. New in LLVM 2.8: - -Soft float support -

- -

DragonEgg: llvm-gcc ported to gcc-4.5 @@ -295,25 +197,67 @@ optimizers, rather than just a handful.

Fortran programs using common variables now link correctly.

GNU OMP constructs no longer crash the compiler.

+ +

+VMKit: JVM/CLI Virtual Machine Implementation +

+ +

+The VMKit project is an implementation of +a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and +just-in-time compilation. As of LLVM 2.8, VMKit now supports copying garbage +collectors, and can be configured to use MMTk's copy mark-sweep garbage +collector. In LLVM 2.8, the VMKit .NET VM is no longer being maintained. +

-LLDB: Low Level Debugger +compiler-rt: Compiler Runtime Library

-LLDB is

+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. New in LLVM 2.8, compiler_rt now supports +soft floating point (for targets that don't have a real floating point unit), +and includes an extensive testsuite for the "blocks" language feature and the +blocks runtime included in compiler_rt.

+ +

+ + +

+LLDB: Low Level Debugger +

+ +

+LLDB is a brand new member of the LLVM +umbrella of projects. LLDB is a next generation, high-performance debugger. It +is built as a set of reusable components which highly leverage existing +libraries in the larger LLVM Project, such as the Clang expression parser, the +LLVM disassembler and the LLVM JIT.

-2.8 status here. +LLDB is in early development and not included as part of the LLVM 2.8 release, +but is mature enough to support basic debugging scenarios on Mac OS X in C, +Objective-C and C++. We'd really like help extending and expanding LLDB to +support new platforms, new languages, new architectures, and new features.

@@ -325,15 +269,54 @@ optimizers, rather than just a handful.

-libc++ is

+libc++ is another new member of the LLVM +family. It is an implementation of the C++ standard library, written from the +ground up to specifically target the forthcoming C++'0X standard and focus on +delivering great performance.

+As of the LLVM 2.8 release, libc++ is virtually feature complete, but would +benefit from more testing and better integration with Clang++. It is also +looking forward to the C++ committee finalizing the C++'0x standard.

+ + + + +

+KLEE: A Symbolic Execution Virtual Machine +

+ +

-2.8 status here. +KLEE 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 some algorithms.

Although KLEE does not have any major new features as of 2.8, we have made +various minor improvements, particular to ease development:

Added support for LLVM 2.8. KLEE currently maintains compatibility with + LLVM 2.6, 2.7, and 2.8.
Added a buildbot for 2.6, 2.7, and trunk. A 2.8 buildbot will be coming + soon following release.
Fixed many C++ code issues to allow building with Clang++. Mostly + complete, except for the version of MiniSAT which is inside the KLEE STP + version.
Improved support for building with separate source and build + directories.
Added support for "long double" on x86.
Initial work on KLEE support for using 'lit' test runner instead of + DejaGNU.
Added configure support for using an external version of + STP.

@@ -383,8 +366,8 @@ recompilation of larger parts of the compiler chain.

language and compiler written on top of LLVM, intended for producing single-address-space managed code operating systems that run faster than the equivalent multiple-address-space C systems. -More in-depth blurb is available on the wiki.

+More in-depth blurb is available on the wiki.

@@ -395,14 +378,14 @@ href="http://www.quokforge.org/projects/horizon/wiki/Wiki">the wiki.

-Clam AntiVirus is an open source (GPL) +Clam AntiVirus is an open source (GPL) anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail gateways. Since version 0.96 it has bytecode signatures that allow writing detections for complex malware. It uses LLVM's JIT to speed up the execution of bytecode on -X86,X86-64,PPC32/64, falling back to its own interpreter otherwise. -The git version was updated to work with LLVM 2.8 +X86, X86-64, PPC32/64, falling back to its own interpreter otherwise. +The git version was updated to work with LLVM 2.8.

The

+ +

+FAUST Real-Time Audio Signal Processing Language +

+ +

+FAUST is a compiled language for real-time +audio signal processing. The name FAUST stands for Functional AUdio STream. Its +programming model combines two approaches: functional programming and block +diagram composition. In addition with the C, C++, JAVA output formats, the +Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7 and +2.8.

- -

- What's New in LLVM 2.8?

- + + +

+Jade Just-in-time Adaptive Decoder Engine +

Jade +(Just-in-time Adaptive Decoder Engine) is a generic video decoder engine using +LLVM for just-in-time compilation of video decoder configurations. Those +configurations are designed by MPEG Reconfigurable Video Coding (RVC) committee. +MPEG RVC standard is built on a stream-based dataflow representation of +decoders. It is composed of a standard library of coding tools written in +RVC-CAL language and a dataflow configuration — block diagram — +of a decoder.

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. -

Jade project is hosted as part of the Open +RVC-CAL Compiler and requires it to translate the RVC-CAL standard library +of video coding tools into an LLVM assembly code.

+ +

+ + +

+LLVM JIT for Neko VM +

+ +

Neko LLVM JIT +replaces the standard Neko JIT with an LLVM-based implementation. While not +fully complete, it is already providing a 1.5x speedup on 64-bit systems. +Neko LLVM JIT requires LLVM 2.8 or later.

+ +

+ + +

+Crack Scripting Language +

+ +

+Crack aims to provide +the ease of development of a scripting language with the performance of a +compiled language. The language derives concepts from C++, Java and Python, +incorporating object-oriented programming, operator overloading and strong +typing. Crack 0.2 works with LLVM 2.7, and the forthcoming Crack 0.2.1 release +builds on LLVM 2.8.

+ +

+ + +

+Dresden TM Compiler (DTMC) +

+ +

+DTMC provides support for +Transactional Memory, which is an easy-to-use and efficient way to synchronize +accesses to shared memory. Transactions can contain normal C/C++ code (e.g., +__transaction { list.remove(x); x.refCount--; }) and will be executed +virtually atomically and isolated from other transactions.

-LLVM Community Changes +Kai Programming Language

+Kai (Japanese ä¼ for +meeting/gathering) is an experimental interpreter that provides a highly +extensible runtime environment and explicit control over the compilation +process. Programs are defined using nested symbolic expressions, which are all +parsed into first-class values with minimal intrinsic semantics. Kai can +generate optimised code at run-time (using LLVM) in order to exploit the nature +of the underlying hardware and to integrate with external software libraries. +It is a unique exploration into world of dynamic code compilation, and the +interaction between high level and low level semantics.

+ +

+ + +

+OSL: Open Shading Language +

In addition to changes to the code, between LLVM 2.7 and 2.8, a number of -organization changes have happened: +

+OSL is a shading +language designed for use in physically based renderers and in particular +production rendering. By using LLVM instead of the interpreter, it was able to +meet its performance goals (>= C-code) while retaining the benefits of +runtime specialization and a portable high-level language. +

+ +

+ + + + +

+ What's New in LLVM 2.8? +

+ + +

+ +

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.

libc++ and lldb are new
Debugging optimized code support.

@@ -526,11 +610,16 @@ organization changes have happened:

LLVM 2.8 includes several major new capabilities:

atomic lowering pass.
RegionInfo pass: opt -regions analyze" or "opt -view-regions". -
ARMGlobalMerge:
llvm-diff
As mentioned above, libc++ and LLDB are major new additions to the LLVM collective.
LLVM 2.8 now has pretty decent support for debugging optimized code. You + should be able to reliably get debug info for function arguments, assuming + that the value is actually available where you have stopped.
A new 'llvm-diff' tool is available that does a semantic diff of .ll + files.
The MC subproject has made major progress in this release. + Direct .o file writing support for darwin/x86[-64] is now reliable and + support for other targets and object file formats are in progress.

@@ -545,56 +634,19 @@ organization changes have happened: expose new optimization opportunities:

LLVM 2.8 changes the internal order of operands in InvokeInst - and CallInst. - To be portable across releases, resort to CallSite and the - high-level accessors, such as getCalledValue and setUnwindDest. -
- You can no longer pass use_iterators directly to cast<> (and similar), because - these routines tend to perform costly dereference operations more than once. You - have to dereference the iterators yourself and pass them in. -
- llvm.memcpy.*, llvm.memset.*, llvm.memmove.* (and possibly other?) intrinsics - take an extra parameter now (i1 isVolatile), totaling 5 parameters. - If you were creating these intrinsic calls and prototypes yourself (as opposed - to using Intrinsic::getDeclaration), you can use UpgradeIntrinsicFunction/UpgradeIntrinsicCall - to be portable accross releases. - Note that you cannot use Intrinsic::getDeclaration() in a backwards compatible - way (needs 2/3 types now, in 2.7 it needed just 1). -
- SetCurrentDebugLocation takes a DebugLoc now instead of a MDNode. - Change your code to use - SetCurrentDebugLocation(DebugLoc::getFromDILocation(...)). -
- VISIBILITY_HIDDEN is gone. -
- The RegisterPass and RegisterAnalysisGroup templates are - considered deprecated, but continue to function in LLVM 2.8. Clients are - strongly advised to use the upcoming INITIALIZE_PASS() and - INITIALIZE_AG_PASS() macros instead. -
- SMDiagnostic takes different parameters now. //FIXME: how to upgrade? -
- The constructor for the Triple class no longer tries to understand odd triple - specifications. Frontends should ensure that they only pass valid triples to - LLVM. The Triple::normalize utility method has been added to help front-ends - deal with funky triples. -
- Some APIs got renamed: -
- llvm_report_error -> report_fatal_error
- llvm_install_error_handler -> install_fatal_error_handler
- llvm::DwarfExceptionHandling -> llvm::JITExceptionHandling
+
The memcpy, memmove, and memset + intrinsics now take address space qualified pointers and a bit to indicate + whether the transfer is "volatile" or not.
Per-instruction debug info metadata is much faster and uses less memory by + using the new DebugLoc class.
LLVM IR now has a more formalized concept of "trap values", which allow the optimizer + to optimize more aggressively in the presence of undefined behavior, while + still producing predictable results.
LLVM IR now supports two new linkage + types (linker_private_weak and linker_private_weak_def_auto) which map + onto some obscure MachO concepts.

@@ -610,25 +662,38 @@ expose new optimization opportunities:

release includes a few major enhancements and additions to the optimizers:

As mentioned above, the optimizer now has support for updating debug + information as it goes. A key aspect of this is the new llvm.dbg.value + intrinsic. This intrinsic represents debug info for variables that are + promoted to SSA values (typically by mem2reg or the -scalarrepl passes).
The JumpThreading pass is now much more aggressive about implied value + relations, allowing it to thread conditions like "a == 4" when a is known to + be 13 in one of the predecessors of a block. It does this in conjunction + with the new LazyValueInfo analysis pass.
The new RegionInfo analysis pass identifies single-entry single-exit regions + in the CFG. You can play with it with the "opt -regions -analyze" or + "opt -view-regions" commands.
The loop optimizer has significantly improved strength reduction and analysis + capabilities. Notably it is able to build on the trap value and signed + integer overflow information to optimize <= and >= loops.
The CallGraphSCCPassManager now has some basic support for iterating within + an SCC when a optimizer devirtualizes a function call. This allows inlining + through indirect call sites that are devirtualized by store-load forwarding + and other optimizations.
The new -loweratomic pass is available + to lower atomic instructions into their non-atomic form. This can be useful + to optimize generic code that expects to run in a single-threaded + environment.

- - - - -

-Interpreter and JIT Improvements -

- -

@@ -639,26 +704,41 @@ release includes a few major enhancements and additions to the optimizers:

-FIXME: Rewrite. - -The LLVM Machine Code (aka MC) sub-project of LLVM was created to solve a number +The LLVM Machine Code (aka MC) subsystem 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 + +

The MC subproject has made great leaps in LLVM 2.8. For example, support for + directly writing .o files from LLC (and clang) now works reliably for + darwin/x86[-64] (including inline assembly support) and the integrated + assembler is turned on by default in Clang for these targets. This provides + improved compile times among other things.

+ +

The entire compiler has converted over to using the MCStreamer assembler API + instead of writing out a .s file textually.
The "assembler parser" is far more mature than in 2.7, supporting a full + complement of directives, now supports assembler macros, etc.
The "assembler backend" has been completed, including support for relaxation + relocation processing and all the other things that an assembler does.
The MachO file format support is now fully functional and works.
The MC disassembler now fully supports ARM and Thumb. ARM assembler support + is still in early development though.
The X86 MC assembler now supports the X86 AES and AVX instruction set.
Work on ELF and COFF object files and ARM target support is well underway, + but isn't useful yet in LLVM 2.8. Please contact the llvmdev mailing list + if you're interested in this.

+ +

For more information, please see the Intro to the LLVM MC Project Blog Post.

2.8 status here. Basic correctness, some obscure missing instructions on - mainline, on by default in clang. - Entire compiler backend converted to use mcstreamer. -

Target Independent Code Generator Improvements @@ -671,7 +751,58 @@ infrastructure, which allows us to implement more aggressive algorithms and make it run faster:

MachO writer works.
The clang/gcc -momit-leaf-frame-pointer argument is now supported.
The clang/gcc -ffunction-sections and -fdata-sections arguments are now + supported on ELF targets (like GCC).
The MachineCSE pass is now tuned and on by default. It eliminates common + subexpressions that are exposed when lowering to machine instructions.
The "local" register allocator was replaced by a new "fast" register + allocator. This new allocator (which is often used at -O0) is substantially + faster and produces better code than the old local register allocator.
A new LLC "-regalloc=default" option is available, which automatically + chooses a register allocator based on the -O optimization level.
The common code generator code was modified to promote illegal argument and + return value vectors to wider ones when possible instead of scalarizing + them. For example, <3 x float> will now pass in one SSE register + instead of 3 on X86. This generates substantially better code since the + rest of the code generator was already expecting this.
The code generator uses a new "COPY" machine instruction. This speeds up + the code generator and eliminates the need for targets to implement the + isMoveInstr hook. Also, the copyRegToReg hook was renamed to copyPhysReg + and simplified.
The code generator now has a "LocalStackSlotPass", which optimizes stack + slot access for targets (like ARM) that have limited stack displacement + addressing.
A new "PeepholeOptimizer" is available, which eliminates sign and zero + extends, and optimizes away compare instructions when the condition result + is available from a previous instruction.
Atomic operations now get legalized into simpler atomic operations if not + natively supported, easing the implementation burden on targets.
We have added two new bottom-up pre-allocation register pressure aware schedulers: +
1. The hybrid scheduler schedules aggressively to minimize schedule length when registers are available and avoid overscheduling in high pressure situations.
2. The instruction-level-parallelism scheduler schedules for maximum ILP when registers are available and avoid overscheduling in high pressure situations.
The tblgen type inference algorithm was rewritten to be more consistent and + diagnose more target bugs. If you have an out-of-tree backend, you may + find that it finds bugs in your target description. This support also + allows limited support for writing patterns for instructions that return + multiple results (e.g. a virtual register and a flag result). The + 'parallel' modifier in tblgen was removed, you should use the new support + for multiple results instead.
A new (experimental) "-rendermf" pass is available which renders a + MachineFunction into HTML, showing live ranges and other useful + details.
The new SubRegIndex tablegen class allows subregisters to be indexed + symbolically instead of numerically. If your target uses subregisters you + will need to adapt to use SubRegIndex when you upgrade to 2.8.
The -fast-isel instruction selection path (used at -O0 on X86) was rewritten + to work bottom-up on basic blocks instead of top down. This makes it + slightly faster (because the MachineDCE pass is not needed any longer) and + allows it to generate better code in some cases.

@@ -681,14 +812,46 @@ it run faster:

New features of the X86 target include: +

New features and major changes in the X86 target include:

The X86 backend now supports holding X87 floating point stack values in registers across basic blocks, dramatically improving performance of code - that uses long double, and when targetting CPUs that don't support SSE.
The X86 backend now uses a SSEDomainFix pass to optimize SSE operations. On + Nehalem ("Core i7") and newer CPUs there is a 2 cycle latency penalty on + using a register in a different domain than where it was defined. This pass + optimizes away these stalls.
The X86 backend now promotes 16-bit integer operations to 32-bits when + possible. This avoids 0x66 prefixes, which are slow on some + microarchitectures and bloat the code on all of them.
The X86 backend now supports the Microsoft "thiscall" calling convention, + and a calling convention to support + ghc.
The X86 backend supports a new "llvm.x86.int" intrinsic, which maps onto + the X86 "int $42" and "int3" instructions.
At the IR level, the <2 x float> datatype is now promoted and passed + around as a <4 x float> instead of being passed and returned as an MMX + vector. If you have a frontend that uses this, please pass and return a + <2 x i32> instead (using bitcasts).
When printing .s files in verbose assembly mode (the default for clang -S), + the X86 backend now decodes X86 shuffle instructions and prints human + readable comments after the most inscrutable of them, e.g.: + +
```
+  insertps $113, %xmm3, %xmm0 # xmm0 = zero,xmm0[1,2],xmm3[1]
+  unpcklps %xmm1, %xmm0       # xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1]
+  pshufd   $1, %xmm1, %xmm1   # xmm1 = xmm1[1,0,0,0]
+
```
+

@@ -703,115 +866,224 @@ it run faster:

- All of the NEON load and store intrinsics (llvm.arm.neon.vld* and - llvm.arm.neon.vst*) take an extra parameter to specify the alignment in bytes - of the memory being accessed. -
- The llvm.arm.neon.vaba intrinsic (vector absolute difference and - accumulate) has been removed. This operation is now represented using - the llvm.arm.neon.vabd intrinsic (vector absolute difference) followed by a - vector add. -
- The llvm.arm.neon.vabdl and llvm.arm.neon.vabal intrinsics (lengthening - vector absolute difference with and without accumlation) have been removed. - They are represented using the llvm.arm.neon.vabd intrinsic (vector absolute - difference) followed by a vector zero-extend operation, and for vabal, - a vector add. +
The ARM backend now optimizes tail calls into jumps.
Scheduling is improved through the new list-hybrid scheduler as well + as through better modeling of structural hazards.
Half float instructions are now + supported.
NEON support has been improved to model instructions which operate onto + multiple consecutive registers more aggressively. This avoids lots of + extraneous register copies.
The ARM backend now uses a new "ARMGlobalMerge" pass, which merges several + global variables into one, saving extra address computation (all the global + variables can be accessed via same base address) and potentially reducing + register pressure.
The ARM backend has received many minor improvements and tweaks which lead + to substantially better performance in a wide range of different scenarios.
- The llvm.arm.neon.vmovn intrinsic has been removed. Calls of this intrinsic - are now replaced by vector truncate operations. -
- The llvm.arm.neon.vmovls and llvm.arm.neon.vmovlu intrinsics have been - removed. They are now represented as vector sign-extend (vmovls) and - zero-extend (vmovlu) operations. -
- The llvm.arm.neon.vaddl*, llvm.arm.neon.vaddw*, llvm.arm.neon.vsubl*, and - llvm.arm.neon.vsubw* intrinsics (lengthening vector add and subtract) have - been removed. They are replaced by vector add and vector subtract operations - where one (vaddw, vsubw) or both (vaddl, vsubl) of the operands are either - sign-extended or zero-extended. -
- The llvm.arm.neon.vmulls, llvm.arm.neon.vmullu, llvm.arm.neon.vmlal*, and - llvm.arm.neon.vmlsl* intrinsics (lengthening vector multiply with and without - accumulation and subtraction) have been removed. These operations are now - represented as vector multiplications where the operands are either - sign-extended or zero-extended, followed by a vector add for vmlal or a - vector subtract for vmlsl. Note that the polynomial vector multiply - intrinsic, llvm.arm.neon.vmullp, remains unchanged. + +
The ARM NEON intrinsics have been substantially reworked to reduce + redundancy and improve code generation. Some of the major changes are: +
1. + All of the NEON load and store intrinsics (llvm.arm.neon.vld* and + llvm.arm.neon.vst*) take an extra parameter to specify the alignment in bytes + of the memory being accessed. +
2. + The llvm.arm.neon.vaba intrinsic (vector absolute difference and + accumulate) has been removed. This operation is now represented using + the llvm.arm.neon.vabd intrinsic (vector absolute difference) followed by a + vector add. +
3. + The llvm.arm.neon.vabdl and llvm.arm.neon.vabal intrinsics (lengthening + vector absolute difference with and without accumulation) have been removed. + They are represented using the llvm.arm.neon.vabd intrinsic (vector absolute + difference) followed by a vector zero-extend operation, and for vabal, + a vector add. +
4. + The llvm.arm.neon.vmovn intrinsic has been removed. Calls of this intrinsic + are now replaced by vector truncate operations. +
5. + The llvm.arm.neon.vmovls and llvm.arm.neon.vmovlu intrinsics have been + removed. They are now represented as vector sign-extend (vmovls) and + zero-extend (vmovlu) operations. +
6. + The llvm.arm.neon.vaddl*, llvm.arm.neon.vaddw*, llvm.arm.neon.vsubl*, and + llvm.arm.neon.vsubw* intrinsics (lengthening vector add and subtract) have + been removed. They are replaced by vector add and vector subtract operations + where one (vaddw, vsubw) or both (vaddl, vsubl) of the operands are either + sign-extended or zero-extended. +
7. + The llvm.arm.neon.vmulls, llvm.arm.neon.vmullu, llvm.arm.neon.vmlal*, and + llvm.arm.neon.vmlsl* intrinsics (lengthening vector multiply with and without + accumulation and subtraction) have been removed. These operations are now + represented as vector multiplications where the operands are either + sign-extended or zero-extended, followed by a vector add for vmlal or a + vector subtract for vmlsl. Note that the polynomial vector multiply + intrinsic, llvm.arm.neon.vmullp, remains unchanged. +

-New Useful APIs +Major Changes and Removed Features

This release includes a number of new APIs that are used internally, which - may also be useful for external clients. -

If you're already an LLVM user or developer with out-of-tree changes based +on LLVM 2.7, this section lists some "gotchas" that you may run into upgrading +from the previous release.

The build configuration machinery changed the output directory names. It + wasn't clear to many people that a "Release-Asserts" build was a release build + without asserts. To make this more clear, "Release" does not include + assertions and "Release+Asserts" does (likewise, "Debug" and + "Debug+Asserts").
The MSIL Backend was removed, it was unsupported and broken.
The ABCD, SSI, and SCCVN passes were removed. These were not fully + functional and their behavior has been or will be subsumed by the + LazyValueInfo pass.
The LLVM IR 'Union' feature was removed. While this is a desirable feature + for LLVM IR to support, the existing implementation was half baked and + barely useful. We'd really like anyone interested to resurrect the work and + finish it for a future release.
If you're used to reading .ll files, you'll probably notice that .ll file + dumps don't produce #uses comments anymore. To get them, run a .bc file + through "llvm-dis --show-annotations".
Target triples are now stored in a normalized form, and all inputs from + humans are expected to be normalized by Triple::normalize before being + stored in a module triple or passed to another library.

- - -

-Other Improvements and New Features -

- -

Other miscellaneous features include:

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

LLVM 2.8 changes the internal order of operands in InvokeInst + and CallInst. + To be portable across releases, please use the CallSite class and the + high-level accessors, such as getCalledValue and + setUnwindDest. +
+ You can no longer pass use_iterators directly to cast<> (and similar), + because these routines tend to perform costly dereference operations more + than once. You have to dereference the iterators yourself and pass them in. +
+ llvm.memcpy.*, llvm.memset.*, llvm.memmove.* intrinsics take an extra + parameter now ("i1 isVolatile"), totaling 5 parameters, and the pointer + operands are now address-space qualified. + If you were creating these intrinsic calls and prototypes yourself (as opposed + to using Intrinsic::getDeclaration), you can use + UpgradeIntrinsicFunction/UpgradeIntrinsicCall to be portable across releases. +
+ SetCurrentDebugLocation takes a DebugLoc now instead of a MDNode. + Change your code to use + SetCurrentDebugLocation(DebugLoc::getFromDILocation(...)). +
+ The RegisterPass and RegisterAnalysisGroup templates are + considered deprecated, but continue to function in LLVM 2.8. Clients are + strongly advised to use the upcoming INITIALIZE_PASS() and + INITIALIZE_AG_PASS() macros instead. +
+ The constructor for the Triple class no longer tries to understand odd triple + specifications. Frontends should ensure that they only pass valid triples to + LLVM. The Triple::normalize utility method has been added to help front-ends + deal with funky triples. +
+ The signature of the GCMetadataPrinter::finishAssembly virtual + function changed: the raw_ostream and MCAsmInfo arguments + were dropped. GC plugins which compute stack maps must be updated to avoid + having the old definition overload the new signature. +
+ The signature of MemoryBuffer::getMemBuffer changed. Unfortunately + calls intended for the old version still compile, but will not work correctly, + leading to a confusing error about an invalid header in the bitcode. +
+ Some APIs were renamed: +
- llvm_report_error -> report_fatal_error
- llvm_install_error_handler -> install_fatal_error_handler
- llvm::DwarfExceptionHandling -> llvm::JITExceptionHandling
- VISIBILITY_HIDDEN -> LLVM_LIBRARY_VISIBILITY
+
+ Some public headers were renamed: +
- llvm/Assembly/AsmAnnotationWriter.h was renamed + to llvm/Assembly/AssemblyAnnotationWriter.h +

-Major Changes and Removed Features +Development Infrastructure Changes

If you're already an LLVM user or developer with out-of-tree changes based -on LLVM 2.7, this section lists some "gotchas" that you may run into upgrading -from the previous release.

This section lists changes to the LLVM development infrastructure. This +mostly impacts users who actively work on LLVM or follow development on +mainline, but may also impact users who leverage the LLVM build infrastructure +or are interested in LLVM qualification.

.ll file doesn't produce #uses comments anymore, to get them, run a .bc file - through "llvm-dis --show-annotations".
MSIL Backend removed.
ABCD and SSI passes removed.
'Union' LLVM IR feature removed.
The default for make check is now to use + the lit testing tool, which is + part of LLVM itself. You can use lit directly as well, or use + the llvm-lit tool which is created as part of a Makefile or CMake + build (and knows how to find the appropriate tools). See the lit + documentation and the blog + post, and PR5217 + for more information.
The LLVM test-suite infrastructure has a new "simple" test format + (make TEST=simple). The new format is intended to require only a + compiler and not a full set of LLVM tools. This makes it useful for testing + released compilers, for running the test suite with other compilers (for + performance comparisons), and makes sure that we are testing the compiler as + users would see it. The new format is also designed to work using reference + outputs instead of comparison to a baseline compiler, which makes it run much + faster and makes it less system dependent.
Significant progress has been made on a new interface to running the + LLVM test-suite (aka the LLVM "nightly tests") using + the LNT infrastructure. The LNT + interface to the test-suite brings significantly improved reporting + capabilities for monitoring the correctness and generated code quality + produced by LLVM over time.

- -

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

- -

Known Problems @@ -842,10 +1114,10 @@ components, please contact us on the LLVMdev list.

The Alpha, SPU, MIPS, PIC16, Blackfin, MSP430, SystemZ and MicroBlaze - backends are experimental.
llc "-filetype=asm" (the default) is the only - supported value for this option. XXX Update me
The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, SystemZ + and XCore backends are experimental.
llc "-filetype=obj" is experimental on all targets + other than darwin-i386 and darwin-x86_64.

@@ -990,37 +1262,9 @@ Depending on it for anything serious is not advised.

4.2. If you are interested in Fortran, we recommend that you consider using dragonegg instead.

The llvm-gcc 4.2 Ada compiler has basic functionality. However, this is not a -mature technology, and problems should be expected. For example:

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 -which does support trampolines.
The Ada front-end fails to 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). -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.
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 -starting or finishing in the middle of a byte.
The lli interpreter considers -'main' as generated by the Ada binder to be invalid. -Workaround: hand edit the file to use pointers for argv and -envp rather than integers.
The -fstack-check option is -ignored.

The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being +actively maintained. If you are interested in Ada, we recommend that you +consider using dragonegg instead.