[PATCH] D141079: [DAGCombine] Fold constants across (extract_vector_elt (bitcast (splat_vector)))

[Luke Lau via Phabricator via llvm-commits]

luke added a comment.

In D141079#4034345 <https://reviews.llvm.org/D141079#4034345>, @RKSimon wrote:

> How come SelectionDAG::computeKnownBits isn't handling this?

I presume because it doesn't handle scalable vectors so far:

  case ISD::EXTRACT_SUBVECTOR: {
    // Offset the demanded elts by the subvector index.
    SDValue Src = Op.getOperand(0);
    // Bail until we can represent demanded elements for scalable vectors.
    if (Op.getValueType().isScalableVector() || Src.getValueType().isScalableVector())
      break;


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