[mlir] Add res() method to linalg::ContractionOpInterface (#76539)

In addition to `lhs()` and `rhs()` to return left and right operands,
add `res()` to return the result value.

Author: Jerry Wu

mlir/include/mlir/Dialect/Linalg/IR/LinalgInterfaces.td

@@ -54,6 +54,14 @@ def LinalgContractionOpInterface : OpInterface<"ContractionOpInterface"> {
       return $_op.getOperation()->getOperand(1);
     }]>,
     InterfaceMethod<
+    /*desc=*/"Returns the result value.",
+    /*retTy=*/"OpResult",
+    /*methodName=*/"res",
+    /*args=*/(ins),
+    /*methodBody=*/[{
+      return $_op.getOperation()->getResult(0);
+    }]>,
+    InterfaceMethod<
     /*desc=*/[{
       Returns whether the given op has indexing maps that correspond to a
       row-major matmul operation.

mlir/unittests/Dialect/CMakeLists.txt

@@ -8,6 +8,7 @@ target_link_libraries(MLIRDialectTests
 
 add_subdirectory(ArmSME)
 add_subdirectory(Index)
+add_subdirectory(Linalg)
 add_subdirectory(LLVMIR)
 add_subdirectory(MemRef)
 add_subdirectory(SCF)

mlir/unittests/Dialect/Linalg/CMakeLists.txt

@@ -0,0 +1,8 @@
+add_mlir_unittest(MLIRLinalgTests
+  LinalgInterfacesTest.cpp
+)
+target_link_libraries(MLIRLinalgTests
+  PRIVATE
+  MLIRLinalgDialect
+  )
+

mlir/unittests/Dialect/Linalg/LinalgInterfacesTest.cpp

@@ -0,0 +1,43 @@
+//===- LinalgInterfacesTest.cpp - LinalgInterfaces unit tests ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/Linalg/IR/Linalg.h"
+#include "mlir/Dialect/Tensor/IR/Tensor.h"
+
+#include "gtest/gtest.h"
+
+using namespace mlir;
+
+class LinalgInterfacesTest : public ::testing::Test {
+protected:
+  LinalgInterfacesTest() {
+    context.getOrLoadDialect<mlir::linalg::LinalgDialect>();
+  }
+
+  mlir::MLIRContext context;
+};
+
+TEST_F(LinalgInterfacesTest, ContractionOpOperandResultAccessor) {
+  OpBuilder b(&context);
+  SmallVector<int64_t> lhsShape = {1, 2};
+  SmallVector<int64_t> rhsShape = {2, 4};
+  SmallVector<int64_t> resShape = {1, 4};
+  auto lhs = b.create<tensor::EmptyOp>(UnknownLoc::get(&context), lhsShape,
+                                       b.getF32Type());
+  auto rhs = b.create<tensor::EmptyOp>(UnknownLoc::get(&context), rhsShape,
+                                       b.getF32Type());
+  auto out = b.create<tensor::EmptyOp>(UnknownLoc::get(&context), resShape,
+                                       b.getF32Type());
+  Operation *op = b.create<linalg::MatmulOp>(
+      UnknownLoc::get(&context), ValueRange{lhs, rhs}, ValueRange{out});
+  auto contractOp = llvm::cast<linalg::ContractionOpInterface>(op);
+
+  EXPECT_EQ(contractOp.lhs(), op->getOperand(0));
+  EXPECT_EQ(contractOp.rhs(), op->getOperand(1));
+  EXPECT_EQ(contractOp.res(), op->getResult(0));
+}