// returns the result.
template <typename ReductionOp>
LogicalResult MatchBinaryReduceFunction(mlir::Region& function) {
  Block& body = function.front();
  if (body.getNumArguments() != 2) return failure();

  mhlo::ReturnOp return_op = dyn_cast<mhlo::ReturnOp>(body.back());
  if (!return_op) return failure();
  if (return_op.getNumOperands() != 1) return failure();

  ReductionOp reduce_op = dyn_cast_or_null<ReductionOp>(