[all-commits] [llvm/llvm-project] d97189: [ARM] Revert WhileLoopStartLR to DoLoopStart

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d97189600e26553fa4fcdc73bd66b22c0ea420dd
      https://github.com/llvm/llvm-project/commit/d97189600e26553fa4fcdc73bd66b22c0ea420dd
  Author: David Green <david.green at arm.com>
  Date:   2021-03-25 (Thu, 25 Mar 2021)

  Changed paths:
    M llvm/lib/Target/ARM/MVETPAndVPTOptimisationsPass.cpp
    M llvm/lib/Target/ARM/MVETailPredUtils.h
    M llvm/test/CodeGen/Thumb2/LowOverheadLoops/while-loops.ll

  Log Message:
  -----------
  [ARM] Revert WhileLoopStartLR to DoLoopStart

If a WhileLoopStartLR is reverted due to calls in the preheader, we may
still be able to instead create a DoLoopStart, preserving the low
overhead loop. This adds code for that, only reverting the
WhileLoopStartR to a Br/Cmp, leaving the rest of the low overhead loop
in place.

Differential Revision: https://reviews.llvm.org/D98413