[PATCH] D54646: DAG combiner: fold (select, C, X, undef) -> X

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

I think this was to utilize dmask turning into undef:

  if (!DMask && !BaseOpcode->Store) {
    // Eliminate no-op loads. Stores with dmask == 0 are *not* no-op: they
    // store the channels' default values.
    SDValue Undef = DAG.getUNDEF(Op.getValueType());
    if (isa<MemSDNode>(Op))
      return DAG.getMergeValues({Undef, Op.getOperand(0)}, DL);
    return Undef;

Any way that makes a non-obvious in the IR undef should work


https://reviews.llvm.org/D54646