[all-commits] [llvm/llvm-project] ca5247: [DAGCombiner] Don't skip no overflow check on UMUL...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ca5247bb1770a1dfa56b78303d99f1cc9a0a06ee
      https://github.com/llvm/llvm-project/commit/ca5247bb1770a1dfa56b78303d99f1cc9a0a06ee
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2021-02-28 (Sun, 28 Feb 2021)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/AArch64/vec_umulo.ll
    M llvm/test/CodeGen/X86/vec_umulo.ll

  Log Message:
  -----------
  [DAGCombiner] Don't skip no overflow check on UMULO if the first computeKnownBits call doesn't return any 0 bits.

Even if the first computeKnownBits call doesn't have any zero
bits it is possible the other operand has bitwidth-1 leading zero.
In that case overflow is still impossible. So always call computeKnownBits
for both operands.