@@ -570,7 +615,6 @@ in this section.

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. @@ -629,7 +673,7 @@ release includes a few major enhancements and additions to the optimizers:

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 + 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 @@ -734,12 +778,11 @@ it run faster:

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.

The bottom-up pre-allocation scheduler is now register pressure aware, - allowing it to avoid overscheduling in high pressure situations while still - aggressively scheduling when registers are available.

A new instruction-level-parallelism pre-allocation scheduler is available, - which is also register pressure aware. This scheduler has shown substantial - wins on X86-64 and is on by default.

We have added two new bottom-up pre-allocation register pressure aware schedulers: +

The hybrid scheduler schedules aggressively to minimize schedule length when registers are available and avoid overscheduling in high pressure situations.
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 @@ -775,7 +818,7 @@ it run faster:

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 @@ -800,7 +843,7 @@ it run faster:
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 inscrutible of them, e.g.: + readable comments after the most inscrutable of them, e.g.:
```
   insertps $113, %xmm3, %xmm0 # xmm0 = zero,xmm0[1,2],xmm3[1]
@@ -836,8 +879,9 @@ it run faster:
     variables can be accessed via same base address) and potentially reducing
     register pressure.
```
The ARM has received many minor improvements and tweaks which lead to -substantially better performance in a wide range of different scenarios.
The ARM backend has received many minor improvements and tweaks which lead + to substantially better performance in a wide range of different scenarios. +
The ARM NEON intrinsics have been substantially reworked to reduce redundancy and improve code generation. Some of the major changes are: @@ -855,7 +899,7 @@ substantially better performance in a wide range of different scenarios.
The llvm.arm.neon.vabdl and llvm.arm.neon.vabal intrinsics (lengthening - vector absolute difference with and without accumlation) have been removed. + 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. @@ -948,7 +992,7 @@ API changes are:
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 accross releases. + UpgradeIntrinsicFunction/UpgradeIntrinsicCall to be portable across releases.
SetCurrentDebugLocation takes a DebugLoc now instead of a MDNode. @@ -967,9 +1011,20 @@ API changes are:
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 got renamed: + Some APIs were renamed:
- llvm_report_error -> report_fatal_error
- llvm_install_error_handler -> install_fatal_error_handler
+ Some public headers were renamed: +
- llvm/Assembly/AsmAnnotationWriter.h was renamed + to llvm/Assembly/AssemblyAnnotationWriter.h +

+ +

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.

+ +

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.

@@ -1013,7 +1114,7 @@ components, please contact us on the LLVMdev list.

The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PIC16, SystemZ +
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.

dragonegg

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.