[all-commits] [llvm/llvm-project] 50b863: [X86] Improve optimizeCompareInstr for signed comp...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 50b8634a99b6f2f36a3fdbea7aa7892c9b881d64
      https://github.com/llvm/llvm-project/commit/50b8634a99b6f2f36a3fdbea7aa7892c9b881d64
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2021-03-31 (Wed, 31 Mar 2021)

  Changed paths:
    M llvm/lib/Target/X86/X86InstrInfo.cpp
    M llvm/test/CodeGen/X86/bmi.ll
    M llvm/test/CodeGen/X86/tbm_patterns.ll

  Log Message:
  -----------
  [X86] Improve optimizeCompareInstr for signed comparisons after BMI/TBM instructions

We previously couldn't optimize out a TEST if the branch/setcc/cmov
used the overflow flag. This patches allows the TEST to be removed
if the flag producing instruction is known to clear the OF flag.
Thats what the TEST instruction would have done so that should be
equivalent.

Need to add test cases. I'll try to get back to this if I have bandwidth.

Fixes PR48768.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D94856