auto func_op = cast<mlir::func::FuncOp>(SymbolTable::lookupSymbolIn(
        op->getParentOfType<mlir::ModuleOp>(), func));
    auto func_ty = func_op.getFunctionType();
    SmallVector<Type> elementTypes{llvm::map_range(
        func_ty.getResults(),
        [](Type ty) { return mlir::cast<ShapedType>(ty).getElementType(); })};

    // Create the mhlo.reduce op.
    auto reduce_op = rewriter.create<mhlo::ReduceOp>(