SuccessChanges

Summary

  1. [lldb] Skip the flakey part of TestStopHookScripted on Linux (details)
  2. [libc++] Simplify how we re-export symbols from libc++abi (details)
  3. [lldb] Add missing import for LLDB test decorators to TestStopHookScripted (details)
  4. [NFC][ARM] LowOverheadLoop DEBUG statements (details)
  5. [LoopFlatten] Add a loop-flattening pass (details)
Commit b272250221595b14c32db6721a0ae4e5f17ea4d2 by Raphael Isemann
[lldb] Skip the flakey part of TestStopHookScripted on Linux

This test seems to randomly fail on Linux machines. It's only one part of the
test failing randomly, so let's just skip it instead of reverting the whole
patch (again).
The file was modifiedlldb/test/API/commands/target/stop-hooks/TestStopHookScripted.py (diff)
Commit 4f13b999297140486b2faa1b5d8d7c768fb40dfb by Louis Dionne
[libc++] Simplify how we re-export symbols from libc++abi

Instead of managing two copies of the symbol lists, reuse the same list
in libc++abi and libc++.

Differential Revision: https://reviews.llvm.org/D88623
The file was removedlibcxx/lib/libc++abi-exceptions.exp
The file was removedlibcxx/lib/libc++abi-exceptions.sjlj.exp
The file was modifiedlibcxx/src/CMakeLists.txt (diff)
The file was modifiedlibcxx/lib/abi/CHANGELOG.TXT (diff)
The file was removedlibcxx/lib/libc++abi-new-delete.exp
The file was modifiedlibcxx/lib/abi/x86_64-apple-darwin.v1.abilist (diff)
The file was modifiedlibcxxabi/src/CMakeLists.txt (diff)
Commit cccb7cf1a52f38182f56d947bd609027726c778b by Raphael Isemann
[lldb] Add missing import for LLDB test decorators to TestStopHookScripted

This test wasn't using decorators before and was missing the import, so my
previous commit broke the test.
The file was modifiedlldb/test/API/commands/target/stop-hooks/TestStopHookScripted.py (diff)
Commit 7e02bc81c6dad90b0f98f74152f4b0991087d78d by sam.parker
[NFC][ARM] LowOverheadLoop DEBUG statements
The file was modifiedllvm/lib/Target/ARM/ARMLowOverheadLoops.cpp (diff)
Commit d53b4bee0ccd408cfe6e592540858046244e74ce by sjoerd.meijer
[LoopFlatten] Add a loop-flattening pass

This is a simple pass that flattens nested loops.  The intention is to optimise
loop nests like this, which together access an array linearly:

  for (int i = 0; i < N; ++i)
    for (int j = 0; j < M; ++j)
      f(A[i*M+j]);

into one loop:

  for (int i = 0; i < (N*M); ++i)
    f(A[i]);

It can also flatten loops where the induction variables are not used in the
loop. This can help with codesize and runtime, especially on simple cpus
without advanced branch prediction.

This is only worth flattening if the induction variables are only used in an
expression like i*M+j. If they had any other uses, we would have to insert a
div/mod to reconstruct the original values, so this wouldn't be profitable.

This partially fixes PR40581 as this pass triggers on one of the two cases. I
will follow up on this to learn LoopFlatten a few more (small) tricks. Please
note that LoopFlatten is not yet enabled by default.

Patch by Oliver Stannard, with minor tweaks from Dave Green and myself.

Differential Revision: https://reviews.llvm.org/D42365
The file was modifiedllvm/include/llvm/InitializePasses.h (diff)
The file was addedllvm/include/llvm/Transforms/Scalar/LoopFlatten.h
The file was modifiedllvm/lib/Transforms/Scalar/CMakeLists.txt (diff)
The file was addedllvm/test/Transforms/LoopFlatten/loop-flatten-negative.ll
The file was modifiedllvm/lib/Transforms/Scalar/Scalar.cpp (diff)
The file was modifiedllvm/lib/Passes/PassRegistry.def (diff)
The file was modifiedllvm/lib/Passes/PassBuilder.cpp (diff)
The file was addedllvm/test/Transforms/LoopFlatten/pr40581.ll
The file was modifiedllvm/include/llvm/LinkAllPasses.h (diff)
The file was modifiedllvm/lib/Transforms/IPO/PassManagerBuilder.cpp (diff)
The file was modifiedllvm/include/llvm/Transforms/Scalar.h (diff)
The file was addedllvm/lib/Transforms/Scalar/LoopFlatten.cpp
The file was addedllvm/test/Transforms/LoopFlatten/loop-flatten.ll