Augment example test with interpreter usage (#2098)

Augmented the example test with interpreter usage demo.

nit: Fixed the dependency of `MLIRParser` on `StablehloReferenceApi` as
API.cc uses `parseSourceFile`.

examples/c++/BUILD.bazel

@@ -19,11 +19,12 @@ package(
 )
 
 cc_binary(
-    name = "stablehlo-add",
+    name = "example-add",
     srcs = [
-        "stablehlo_add.cpp",
+        "ExampleAdd.cpp",
     ],
     deps = [
+        "//:reference_api",
         "//:stablehlo_ops",
         "@llvm-project//mlir:FuncDialect",
         "@llvm-project//mlir:IR",
@@ -32,11 +33,12 @@ cc_binary(
 )
 
 cc_test(
-    name = "stablehlo-add_test",
+    name = "example-add-test",
     srcs = [
-        "stablehlo_add.cpp",
+        "ExampleAdd.cpp",
     ],
     deps = [
+        "//:reference_api",
         "//:stablehlo_ops",
         "@llvm-project//mlir:FuncDialect",
         "@llvm-project//mlir:IR",

examples/c++/CMakeLists.txt

@@ -14,16 +14,16 @@
 
 # TODO(fzakaria): As we think about adding more tests we should consider
 # making this a function to be DRY.
-add_executable(stablehlo-add stablehlo_add.cpp)
-llvm_update_compile_flags(stablehlo-add)
-target_link_libraries(stablehlo-add PRIVATE StablehloOps)
+add_executable(example-add ExampleAdd.cpp)
+llvm_update_compile_flags(example-add)
+target_link_libraries(example-add PRIVATE StablehloOps StablehloReferenceApi)
 
-mlir_check_all_link_libraries(stablehlo-add)
-add_custom_target(stablehlo-add-test
-  COMMAND stablehlo-add
+mlir_check_all_link_libraries(example-add)
+add_custom_target(example-add-test
+  COMMAND example-add
   WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
-  COMMENT "Executing stablehlo-add to validate it works."
+  COMMENT "Executing example-add to validate it works."
   DEPENDS
-    stablehlo-add
+    example-add
 )
-add_dependencies(check-stablehlo-quick stablehlo-add-test)
+add_dependencies(check-stablehlo-quick example-add-test)

examples/c++/stablehlo_add.cpp → examples/c++/ExampleAdd.cpp

@@ -14,10 +14,12 @@ limitations under the License.
 ==============================================================================*/
 #include "mlir/Dialect/Func/IR/FuncOps.h"
 #include "mlir/Dialect/Quant/QuantOps.h"
+#include "mlir/IR/BuiltinAttributes.h"
 #include "mlir/IR/BuiltinOps.h"
 #include "mlir/IR/BuiltinTypes.h"
 #include "mlir/IR/Verifier.h"
 #include "stablehlo/dialect/StablehloOps.h"
+#include "stablehlo/reference/Api.h"
 
 int main() {
   mlir::MLIRContext context;
@@ -31,10 +33,11 @@ int main() {
   module->setName("test_module");
 
   /** create function **/
-  // create function argument and result types
-  mlir::Type arg0 =
+  // create function argument and result types.
+  auto tensorType =
       mlir::RankedTensorType::get({3, 4}, mlir::FloatType::getF32(&context));
-  auto func_type = mlir::FunctionType::get(&context, {arg0, arg0}, {arg0});
+  auto func_type =
+      mlir::FunctionType::get(&context, {tensorType, tensorType}, {tensorType});
 
   // create the function and map arguments.
   llvm::ArrayRef<mlir::NamedAttribute> attrs;
@@ -43,26 +46,34 @@ int main() {
   function.setVisibility(mlir::func::FuncOp::Visibility::Public);
   module->push_back(function);
 
-  // create function block with add operations
+  // create function block with add operations.
   mlir::Block* block = function.addEntryBlock();
   llvm::SmallVector<mlir::Value, 4> arguments(block->args_begin(),
                                               block->args_end());
   mlir::OpBuilder block_builder = mlir::OpBuilder::atBlockEnd(block);
   mlir::Location loc = block_builder.getUnknownLoc();
 
   llvm::SmallVector<mlir::NamedAttribute, 10> attributes;
-  block_builder.create<mlir::stablehlo::AddOp>(loc, arguments, attributes)
-      .getOperation();
-
   mlir::Operation* op =
-      block_builder
-          .create<mlir::stablehlo::AddOp>(loc, arg0, arguments, attributes)
+      block_builder.create<mlir::stablehlo::AddOp>(loc, arguments, attributes)
           .getOperation();
   block_builder.create<mlir::func::ReturnOp>(loc, op->getResult(0));
 
-  // verify the module and dump
+  /** verify and dump the module **/
   assert(mlir::succeeded(mlir::verify(module.get())));
-  module->dump();
 
-  return 0;
+  /* interpret the function "main" with concrete inputs **/
+  auto getConstValue = [&](double val) {
+    return mlir::DenseElementsAttr::get(
+        tensorType,
+        block_builder.getFloatAttr(tensorType.getElementType(), val));
+  };
+
+  auto inputValue1 = getConstValue(10.0);
+  auto inputValue2 = getConstValue(20.0);
+  auto expectedValue = getConstValue(30.0);
+
+  mlir::stablehlo::InterpreterConfiguration config;
+  auto results = evalModule(*module, {inputValue1, inputValue2}, config);
+  return failed(results) || (*results)[0] != expectedValue;
 }

examples/c++/README.md

@@ -5,5 +5,41 @@ for how to use StableHLO.
 
 Note: If you have a great example to highlight, we welcome contributions!
 
-* [stablehlo_add](./stablehlo_add.cpp): A simple example that demonstrates
-how to use the StableHLO library to add two numbers.
+* [example-add](./ExampleAdd.cpp): A simple example that demonstrates how to
+  * Use the StableHLO library to add two numbers.
+  * Interpret a StableHLO program using concrete inputs.
+
+```c++
+  // Assume 'module' is an MLIR module with function "main" containing StableHLO
+  // operations.
+  llvm::outs() << "Program:\n " << module << "\n";
+
+  // Create concrete inputs to be used for interpreting "main".
+  auto inputValue1 = mlir::DenseElementsAttr::get(
+      tensorType, block_builder.getFloatAttr(tensorType.getElementType(),
+                                         static_cast<double>(10)));
+  auto inputValue2 = mlir::DenseElementsAttr::get(
+      tensorType, block_builder.getFloatAttr(tensorType.getElementType(),
+                                       static_cast<double>(20)));
+  llvm::outs() << "Inputs: " << inputValue1 << ", " << inputValue2 << "\n";
+
+
+  mlir::stablehlo::InterpreterConfiguration config;
+  auto results = evalModule(module, {inputValue1, inputValue2}, config);
+  llvm::outs() << "Output: " << (*results)[0];
+```
+
+Output:
+
+```mlir
+Program:
+module @test_module {
+  func.func @main(%arg0: tensor<3x4xf32>, %arg1: tensor<3x4xf32>) -> tensor<3x4xf32> {
+    %0 = stablehlo.add %arg0, %arg1 : tensor<3x4xf32>
+    %1 = stablehlo.add %arg0, %arg1 : tensor<3x4xf32>
+    return %1 : tensor<3x4xf32>
+  }
+}
+Inputs: dense<1.000000e+01> : tensor<3x4xf32>, dense<2.000000e+01> : tensor<3x4xf32>
+Output: dense<3.000000e+01> : tensor<3x4xf32>
+```

stablehlo/reference/CMakeLists.txt

@@ -18,6 +18,7 @@ add_mlir_library(StablehloReferenceApi
 
   LINK_LIBS PUBLIC
   MLIRIR
+  MLIRParser
   MLIRSupport
   InterpreterOps
   StablehloReferenceConfiguration