Android library update for benchmarking support

Test:
```
cd extension/android/benchmark
mkdir app/libs
cp <executorch.aar> app/libs/executorch.aar
./gradlew :app:installDebug

adb shell am start -n org.pytorch.minibench/org.pytorch.minibench.BenchmarkActivity --es model_path /data/local/tmp/model.pte
adb shell run-as org.pytorch.minibench cat files/benchmark_results.txt
```

build/build_android_llm_demo.sh

@@ -30,6 +30,7 @@ build_android_native_library() {
     -DEXECUTORCH_XNNPACK_SHARED_WORKSPACE=ON \
     -DEXECUTORCH_BUILD_EXTENSION_DATA_LOADER=ON \
     -DEXECUTORCH_BUILD_EXTENSION_MODULE=ON \
+    -DEXECUTORCH_BUILD_EXTENSION_RUNNER_UTIL=ON \
     -DEXECUTORCH_BUILD_KERNELS_OPTIMIZED=ON \
     -DEXECUTORCH_BUILD_KERNELS_QUANTIZED=ON \
     -DEXECUTORCH_BUILD_KERNELS_CUSTOM=ON \

extension/android/CMakeLists.txt

@@ -32,8 +32,15 @@ find_package(executorch CONFIG REQUIRED)
 target_link_options_shared_lib(executorch)
 
 set(link_libraries)
-list(APPEND link_libraries extension_data_loader extension_module extension_threadpool executorch
-     fbjni
+list(
+  APPEND
+  link_libraries
+  executorch
+  extension_data_loader
+  extension_module
+  extension_runner_util
+  extension_threadpool
+  fbjni
 )
 
 if(TARGET optimized_native_cpu_ops_lib)

extension/android/jni/jni_layer.cpp

@@ -18,6 +18,7 @@
 #include "jni_layer_constants.h"
 
 #include <executorch/extension/module/module.h>
+#include <executorch/extension/runner_util/inputs.h>
 #include <executorch/extension/runner_util/managed_tensor.h>
 #include <executorch/runtime/core/portable_type/tensor_impl.h>
 #include <executorch/runtime/platform/log.h>
@@ -56,7 +57,7 @@ void et_pal_emit_log_message(
 
 using namespace torch::executor;
 
-namespace executorch_jni {
+namespace executorch::extension {
 class TensorHybrid : public facebook::jni::HybridClass<TensorHybrid> {
  public:
   constexpr static const char* kJavaDescriptor =
@@ -352,19 +353,26 @@ class ExecuTorchJni : public facebook::jni::HybridClass<ExecuTorchJni> {
     return jresult;
   }
 
+  jint forward_ones() {
+    auto&& load_result = module_->load_method("forward");
+    auto&& buf = prepare_input_tensors(*(module_->methods_["forward"].method));
+    auto&& result = module_->methods_["forward"].method->execute();
+    return (jint)result;
+  }
+
   static void registerNatives() {
     registerHybrid({
         makeNativeMethod("initHybrid", ExecuTorchJni::initHybrid),
         makeNativeMethod("forward", ExecuTorchJni::forward),
         makeNativeMethod("execute", ExecuTorchJni::execute),
         makeNativeMethod("loadMethod", ExecuTorchJni::load_method),
+        makeNativeMethod("forwardOnes", ExecuTorchJni::forward_ones),
     });
   }
 };
-
-} // namespace executorch_jni
+} // namespace executorch::extension
 
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void*) {
   return facebook::jni::initialize(
-      vm, [] { executorch_jni::ExecuTorchJni::registerNatives(); });
+      vm, [] { executorch::extension::ExecuTorchJni::registerNatives(); });
 }

extension/android/jni/jni_layer_constants.h

@@ -10,7 +10,7 @@
 
 #include <executorch/runtime/core/portable_type/scalar_type.h>
 
-namespace executorch_jni {
+namespace executorch::extension {
 
 constexpr static int kTensorDTypeUInt8 = 0;
 constexpr static int kTensorDTypeInt8 = 1;
@@ -93,4 +93,4 @@ const std::unordered_map<int, ScalarType> java_dtype_to_scalar_type = {
     {kTensorDTypeBits16, ScalarType::Bits16},
 };
 
-} // namespace executorch_jni
+} // namespace executorch::extension

extension/android/src/main/java/org/pytorch/executorch/Module.java

@@ -79,6 +79,12 @@ public static Module load(final String modelPath) {
    * @return return value from the 'forward' method.
    */
   public EValue[] forward(EValue... inputs) {
+    if (inputs.length == 0) {
+      // forward default args (ones)
+      mNativePeer.forwardOnes();
+      // discard the return value
+      return null;
+    }
     return mNativePeer.forward(inputs);
   }
 

extension/android/src/main/java/org/pytorch/executorch/NativePeer.java

@@ -13,6 +13,7 @@
 import com.facebook.soloader.nativeloader.NativeLoader;
 import java.util.Map;
 
+/** Interface for the native peer object for entry points to the Module */
 class NativePeer {
   static {
     // Loads libexecutorch.so from jniLibs
@@ -29,16 +30,33 @@ private static native HybridData initHybrid(
     mHybridData = initHybrid(moduleAbsolutePath, extraFiles, loadMode);
   }
 
+  /** Clean up the native resources associated with this instance */
   public void resetNative() {
     mHybridData.resetNative();
   }
 
+  /** Run a "forward" call with the given inputs */
   @DoNotStrip
   public native EValue[] forward(EValue... inputs);
 
+  /**
+   * Run a "forward" call with the sample inputs (ones) to test a module
+   *
+   * @return the outputs of the forward call
+   * @apiNote This is experimental and test-only API
+   */
+  @DoNotStrip
+  public native int forwardOnes();
+
+  /** Run an arbitrary method on the module */
   @DoNotStrip
   public native EValue[] execute(String methodName, EValue... inputs);
 
+  /**
+   * Load a method on this module.
+   *
+   * @return the Error code if there was an error loading the method
+   */
   @DoNotStrip
   public native int loadMethod(String methodName);
 }

extension/module/module.h

@@ -358,6 +358,8 @@ class Module final {
   std::unique_ptr<::executorch::runtime::MemoryAllocator> temp_allocator_;
   std::unique_ptr<::executorch::runtime::EventTracer> event_tracer_;
   std::unordered_map<std::string, MethodHolder> methods_;
+
+  friend class ExecuTorchJni;
 };
 
 } // namespace extension