[PATCH] When canonicalizing gep indices, prefer zext when possible (SelectionDAGBuilder)

[hfinkel at anl.gov]

Part of the issue is that this canonicalization already exists in DAGCombine (at the end of DAGCombiner::visitSIGN_EXTEND):

  // fold (sext x) -> (zext x) if the sign bit is known zero.
  if ((!LegalOperations || TLI.isOperationLegal(ISD::ZERO_EXTEND, VT)) &&
      DAG.SignBitIsZero(N0))
    return DAG.getNode(ISD::ZERO_EXTEND, SDLoc(N), VT, N0);

As a result, I'm not sure this is needed.


http://reviews.llvm.org/D7626

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