[Android] Add Java runtime API for registered ops and backends

extension/android/CMakeLists.txt

@@ -64,7 +64,7 @@ set(executorch_DIR ${CMAKE_CURRENT_BINARY_DIR}/../../lib/cmake/ExecuTorch)
 find_package(executorch CONFIG REQUIRED)
 target_link_options_shared_lib(executorch)
 
-add_library(executorch_jni SHARED jni/jni_layer.cpp jni/log.cpp)
+add_library(executorch_jni SHARED jni/jni_layer.cpp jni/log.cpp jni/jni_layer_runtime.cpp)
 
 set(link_libraries)
 list(

extension/android/executorch_android/src/androidTest/java/org/pytorch/executorch/RuntimeInstrumentationTest.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package org.pytorch.executorch;
+
+import static org.junit.Assert.assertNotNull;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import org.junit.runner.RunWith;
+import org.junit.Test;
+
+/** Unit tests for {@link ExecuTorchRuntime}. */
+@RunWith(AndroidJUnit4.class)
+public class RuntimeInstrumentationTest {
+
+    @Test
+    public void testRuntimeApi() {
+        String[] ops = ExecuTorchRuntime.getRegisteredOps();
+        String[] backends = ExecuTorchRuntime.getRegisteredBackends();
+
+        assertNotNull(ops);
+        assertNotNull(backends);
+
+        for (String op : ops) {
+            assertNotNull(op);
+        }
+
+        for (String backend : backends) {
+            assertNotNull(backend);
+        }
+    }
+}

extension/android/executorch_android/src/main/java/org/pytorch/executorch/ExecuTorchRuntime.java

@@ -8,6 +8,7 @@
 
 package org.pytorch.executorch;
 
+import com.facebook.jni.annotations.DoNotStrip;
 import com.facebook.soloader.nativeloader.NativeLoader;
 import com.facebook.soloader.nativeloader.SystemDelegate;
 
@@ -30,4 +31,12 @@ private ExecuTorchRuntime() {}
   public static ExecuTorchRuntime getRuntime() {
     return sInstance;
   }
+
+  /** Get all registered ops. */
+  @DoNotStrip
+  public static native String[] getRegisteredOps();
+
+  /** Get all registered backends. */
+  @DoNotStrip
+  public static native String[] getRegisteredBackends();
 }

extension/android/jni/BUCK

@@ -28,7 +28,7 @@ non_fbcode_target(_kind = executorch_generated_lib,
 
 non_fbcode_target(_kind = fb_android_cxx_library,
     name = "executorch_jni",
-    srcs = ["jni_layer.cpp", "log.cpp"],
+    srcs = ["jni_layer.cpp", "log.cpp", "jni_layer_runtime.cpp"],
     allow_jni_merging = False,
     compiler_flags = ET_JNI_COMPILER_FLAGS,
     soname = "libexecutorch.$(ext)",
@@ -49,7 +49,7 @@ non_fbcode_target(_kind = fb_android_cxx_library,
 
 non_fbcode_target(_kind = fb_android_cxx_library,
     name = "executorch_jni_full",
-    srcs = ["jni_layer.cpp", "log.cpp"],
+    srcs = ["jni_layer.cpp", "log.cpp", "jni_layer_runtime.cpp"],
     allow_jni_merging = False,
     compiler_flags = ET_JNI_COMPILER_FLAGS,
     soname = "libexecutorch.$(ext)",
@@ -74,6 +74,7 @@ non_fbcode_target(_kind = fb_android_cxx_library,
     srcs = [
         "jni_layer.cpp",
         "jni_layer_llama.cpp",
+        "jni_layer_runtime.cpp",
     ],
     allow_jni_merging = False,
     compiler_flags = ET_JNI_COMPILER_FLAGS + [
@@ -113,6 +114,10 @@ runtime.export_file(
     name = "jni_layer.cpp",
 )
 
+runtime.export_file(
+    name = "jni_layer_runtime.cpp",
+)
+
 runtime.cxx_library(
     name = "jni_headers",
     exported_headers = [

extension/android/jni/jni_layer.cpp

@@ -491,9 +491,11 @@ extern void register_natives_for_llm();
 // No op if we don't build LLM
 void register_natives_for_llm() {}
 #endif
+extern void register_natives_for_runtime();
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void*) {
   return facebook::jni::initialize(vm, [] {
     executorch::extension::ExecuTorchJni::registerNatives();
     register_natives_for_llm();
+    register_natives_for_runtime();
   });
 }

extension/android/jni/jni_layer_runtime.cpp

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <fbjni/fbjni.h>
+#include <jni.h>
+
+#include <executorch/runtime/backend/interface.h>
+#include <executorch/runtime/kernel/operator_registry.h>
+
+namespace executorch_jni {
+namespace runtime = ::executorch::ET_RUNTIME_NAMESPACE;
+
+class AndroidRuntimeJni : public facebook::jni::JavaClass<AndroidRuntimeJni> {
+ public:
+  constexpr static const char* kJavaDescriptor =
+      "Lorg/pytorch/executorch/ExecuTorchRuntime;";
+
+  static void registerNatives() {
+    javaClassStatic()->registerNatives({
+        makeNativeMethod(
+            "getRegisteredOps", AndroidRuntimeJni::getRegisteredOps),
+        makeNativeMethod(
+            "getRegisteredBackends", AndroidRuntimeJni::getRegisteredBackends),
+    });
+  }
+
+  // Returns a string array of all registered ops
+  static facebook::jni::local_ref<facebook::jni::JArrayClass<jstring>>
+  getRegisteredOps(facebook::jni::alias_ref<jclass>) {
+    auto kernels = runtime::get_registered_kernels();
+    auto result = facebook::jni::JArrayClass<jstring>::newArray(kernels.size());
+
+    for (size_t i = 0; i < kernels.size(); ++i) {
+      auto op = facebook::jni::make_jstring(kernels[i].name_);
+      result->setElement(i, op.get());
+    }
+
+    return result;
+  }
+
+  // Returns a string array of all registered backends
+  static facebook::jni::local_ref<facebook::jni::JArrayClass<jstring>>
+  getRegisteredBackends(facebook::jni::alias_ref<jclass>) {
+    int num_backends = runtime::get_num_registered_backends();
+    auto result = facebook::jni::JArrayClass<jstring>::newArray(num_backends);
+
+    for (int i = 0; i < num_backends; ++i) {
+      auto name_result = runtime::get_backend_name(i);
+      const char* name = "";
+
+      if (name_result.ok()) {
+        name = *name_result;
+      }
+
+      auto backend_str = facebook::jni::make_jstring(name);
+      result->setElement(i, backend_str.get());
+    }
+
+    return result;
+  }
+};
+
+} // namespace executorch_jni
+
+void register_natives_for_runtime() {
+  executorch_jni::AndroidRuntimeJni::registerNatives();
+}

extension/android/jni/selective_jni.buck.bzl

@@ -4,10 +4,12 @@ load("@fbsource//xplat/executorch/backends/xnnpack/third-party:third_party_libs.
 load("@fbsource//xplat/executorch/extension/android/jni:build_defs.bzl", "ET_JNI_COMPILER_FLAGS")
 
 def selective_jni_target(name, deps, srcs = [], soname = "libexecutorch.$(ext)"):
-    non_fbcode_target(_kind = fb_android_cxx_library,
+    non_fbcode_target(
+        _kind = fb_android_cxx_library,
         name = name,
         srcs = [
             "//xplat/executorch/extension/android/jni:jni_layer.cpp",
+            "//xplat/executorch/extension/android/jni:jni_layer_runtime.cpp",
         ] + srcs,
         allow_jni_merging = False,
         compiler_flags = ET_JNI_COMPILER_FLAGS,