// where $dimensions must have size 1 and iota can have rank>=1.
// It usually used for matching rank 1 iota since the iotaOp will be folded to
// IotaOp + BroadCastInDimOp except for the case when result shape is rank 1.
bool MatchSingleIota(DenseIntElementsAttr dimensions, Value iota) {
  auto iota_op = dyn_cast_or_null<mhlo::IotaOp>(iota.getDefiningOp());
  if (!iota_op || dimensions.getNumElements() != 1) return false;