[PATCH] D71007: [ARM][LowOverheadLoops] Remove dead loop update instructions

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer updated this revision to Diff 233035.
SjoerdMeijer added a comment.

> I'm not sure this is doing what you want.. wouldn't the vctp likely be a use before def..?

Thanks for catching that one too. This was a off-by one error in that function, I wasn't considering the first instruction in the block. The check is now done in a loop, finding defs until we reached the beginning of the block, but ignoring it if is a VCTP instruction.

> We should also be checking that the Def isn't defining cpsr, and if it is, that the def is dead.

Yep, cheers, and tests have been added too.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71007/new/

https://reviews.llvm.org/D71007

Files:
  llvm/include/llvm/CodeGen/MachineLoopUtils.h
  llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
  llvm/lib/CodeGen/MachineLoopUtils.cpp
  llvm/lib/CodeGen/ReachingDefAnalysis.cpp
  llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
  llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-remove-loop-update.mir
  llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-remove-loop-update2.mir
  llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-remove-loop-update3.mir
  llvm/test/CodeGen/Thumb2/LowOverheadLoops/fast-fp-loops.ll
  llvm/test/CodeGen/Thumb2/LowOverheadLoops/mve-tail-data-types.ll
  llvm/test/CodeGen/Thumb2/LowOverheadLoops/vector-arith-codegen.ll

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