[WebNN EP] Support WebNN async API with Asyncify

js/web/lib/build-def.d.ts

@@ -21,10 +21,6 @@ interface BuildDefinitions {
   /**
    * defines whether to disable the whole WebNN backend in the build.
    */
-  readonly DISABLE_WEBNN: boolean;
-  /**
-   * defines whether to disable the whole WebAssembly backend in the build.
-   */
   readonly DISABLE_WASM: boolean;
   /**
    * defines whether to disable proxy feature in WebAssembly backend in the build.

js/web/lib/index.ts

@@ -23,12 +23,10 @@ if (!BUILD_DEFS.DISABLE_WASM) {
                                                     require('./backend-wasm-training').wasmBackend;
   if (!BUILD_DEFS.DISABLE_WEBGPU) {
     registerBackend('webgpu', wasmBackend, 5);
+    registerBackend('webnn', wasmBackend, 5);
   }
   registerBackend('cpu', wasmBackend, 10);
   registerBackend('wasm', wasmBackend, 10);
-  if (!BUILD_DEFS.DISABLE_WEBNN) {
-    registerBackend('webnn', wasmBackend, 9);
-  }
 }
 
 Object.defineProperty(env.versions, 'web', {value: version, enumerable: true});

js/web/lib/wasm/binding/ort-wasm.d.ts

@@ -31,7 +31,7 @@ export interface OrtWasmModule extends EmscriptenModule {
 
   _OrtGetLastError(errorCodeOffset: number, errorMessageOffset: number): void;
 
-  _OrtCreateSession(dataOffset: number, dataLength: number, sessionOptionsHandle: number): number;
+  _OrtCreateSession(dataOffset: number, dataLength: number, sessionOptionsHandle: number): Promise<number>;
   _OrtReleaseSession(sessionHandle: number): void;
   _OrtGetInputOutputCount(sessionHandle: number, inputCountOffset: number, outputCountOffset: number): number;
   _OrtGetInputName(sessionHandle: number, index: number): number;

js/web/lib/wasm/wasm-core-impl.ts

@@ -84,7 +84,7 @@ export const initRuntime = async(env: Env): Promise<void> => {
  * @param epName
  */
 export const initEp = async(env: Env, epName: string): Promise<void> => {
-  if (!BUILD_DEFS.DISABLE_WEBGPU && epName === 'webgpu') {
+  if (!BUILD_DEFS.DISABLE_WEBGPU && (epName === 'webgpu' || epName === 'webnn')) {
     // perform WebGPU availability check
     if (typeof navigator === 'undefined' || !navigator.gpu) {
       throw new Error('WebGPU is not supported in current environment');
@@ -228,7 +228,7 @@ export const createSession = async(
       await Promise.all(loadingPromises);
     }
 
-    sessionHandle = wasm._OrtCreateSession(modelDataOffset, modelDataLength, sessionOptionsHandle);
+    sessionHandle = await wasm._OrtCreateSession(modelDataOffset, modelDataLength, sessionOptionsHandle);
     if (sessionHandle === 0) {
       checkLastError('Can\'t create a session.');
     }

js/web/script/build.ts

@@ -44,7 +44,6 @@ const SOURCE_ROOT_FOLDER = path.join(__dirname, '../..');  // <ORT_ROOT>/js/
 const DEFAULT_DEFINE = {
   'BUILD_DEFS.DISABLE_WEBGL': 'false',
   'BUILD_DEFS.DISABLE_WEBGPU': 'false',
-  'BUILD_DEFS.DISABLE_WEBNN': 'false',
   'BUILD_DEFS.DISABLE_WASM': 'false',
   'BUILD_DEFS.DISABLE_WASM_PROXY': 'false',
   'BUILD_DEFS.DISABLE_WASM_THREAD': 'false',
@@ -364,7 +363,6 @@ async function main() {
         ...DEFAULT_DEFINE,
         'BUILD_DEFS.DISABLE_WEBGPU': 'true',
         'BUILD_DEFS.DISABLE_WEBGL': 'true',
-        'BUILD_DEFS.DISABLE_WEBNN': 'true',
         'BUILD_DEFS.DISABLE_WASM_PROXY': 'true',
         'BUILD_DEFS.DISABLE_WASM_THREAD': 'true',
       },
@@ -397,7 +395,7 @@ async function main() {
     // ort.webgpu[.min].js
     await addAllWebBuildTasks({
       outputBundleName: 'ort.webgpu',
-      define: {...DEFAULT_DEFINE, 'BUILD_DEFS.DISABLE_WEBGL': 'true', 'BUILD_DEFS.DISABLE_WEBNN': 'true'},
+      define: {...DEFAULT_DEFINE, 'BUILD_DEFS.DISABLE_WEBGL': 'true'},
     });
     // ort.wasm[.min].js
     await addAllWebBuildTasks({
@@ -411,7 +409,6 @@ async function main() {
         ...DEFAULT_DEFINE,
         'BUILD_DEFS.DISABLE_WEBGPU': 'true',
         'BUILD_DEFS.DISABLE_WASM': 'true',
-        'BUILD_DEFS.DISABLE_WEBNN': 'true',
       },
     });
     // ort.wasm-core[.min].js
@@ -421,7 +418,6 @@ async function main() {
         ...DEFAULT_DEFINE,
         'BUILD_DEFS.DISABLE_WEBGPU': 'true',
         'BUILD_DEFS.DISABLE_WEBGL': 'true',
-        'BUILD_DEFS.DISABLE_WEBNN': 'true',
         'BUILD_DEFS.DISABLE_WASM_PROXY': 'true',
         'BUILD_DEFS.DISABLE_WASM_THREAD': 'true',
       },
@@ -434,7 +430,6 @@ async function main() {
         'BUILD_DEFS.DISABLE_TRAINING': 'false',
         'BUILD_DEFS.DISABLE_WEBGPU': 'true',
         'BUILD_DEFS.DISABLE_WEBGL': 'true',
-        'BUILD_DEFS.DISABLE_WEBNN': 'true',
       },
     });
   }

js/web/script/test-runner-cli-args.ts

@@ -396,10 +396,6 @@ export function parseTestRunnerCliArgs(cmdlineArgs: string[]): TestRunnerCliArgs
 
   const globalEnvFlags = parseGlobalEnvFlags(args);
 
-  if (backend.includes('webnn') && !globalEnvFlags.wasm!.proxy) {
-    throw new Error('Backend webnn requires flag "wasm-enable-proxy" to be set to true.');
-  }
-
   // Options:
   // --log-verbose=<...>
   // --log-info=<...>

onnxruntime/core/providers/webnn/builders/model.cc

@@ -70,22 +70,13 @@ Status Model::Predict(const InlinedHashMap<std::string, OnnxTensorData>& inputs,
                                "The input of graph has unsupported type, name: ",
                                name, " type: ", tensor.tensor_info.data_type);
     }
-#ifdef ENABLE_WEBASSEMBLY_THREADS
-    // Copy the inputs from Wasm SharedArrayBuffer to the pre-allocated ArrayBuffers.
+    // Copy the inputs from Wasm ArrayBuffer to the WebNN inputs ArrayBuffer.
+    // As Wasm ArrayBuffer is not detachable.
     wnn_inputs_[name].call<void>("set", view);
-#else
-    wnn_inputs_.set(name, view);
-#endif
   }
 
-#ifdef ENABLE_WEBASSEMBLY_THREADS
-  // This vector uses for recording output buffers from WebNN graph compution when WebAssembly
-  // multi-threads is enabled, since WebNN API only accepts non-shared ArrayBufferView,
-  // https://www.w3.org/TR/webnn/#typedefdef-mlnamedarraybufferviews
-  // and at this time the 'view' defined by Emscripten is shared ArrayBufferView, the memory
-  // address is different from the non-shared one, additional memory copy is required here.
   InlinedHashMap<std::string, emscripten::val> output_views;
-#endif
+
   for (const auto& output : outputs) {
     const std::string& name = output.first;
     const struct OnnxTensorData tensor = output.second;
@@ -131,21 +122,23 @@ Status Model::Predict(const InlinedHashMap<std::string, OnnxTensorData>& inputs,
                                name, " type: ", tensor.tensor_info.data_type);
     }
 
-#ifdef ENABLE_WEBASSEMBLY_THREADS
     output_views.insert({name, view});
-#else
-    wnn_outputs_.set(name, view);
-#endif
   }
-  wnn_context_.call<emscripten::val>("computeSync", wnn_graph_, wnn_inputs_, wnn_outputs_);
-#ifdef ENABLE_WEBASSEMBLY_THREADS
-  // Copy the outputs from pre-allocated ArrayBuffers back to the Wasm SharedArrayBuffer.
+  emscripten::val results = wnn_context_.call<emscripten::val>(
+                                            "compute", wnn_graph_, wnn_inputs_, wnn_outputs_)
+                                .await();
+
+  // Copy the outputs from pre-allocated ArrayBuffers back to the Wasm ArrayBuffer.
   for (const auto& output : outputs) {
     const std::string& name = output.first;
     emscripten::val view = output_views.at(name);
-    view.call<void>("set", wnn_outputs_[name]);
+    view.call<void>("set", results["outputs"][name]);
   }
-#endif
+  // WebNN compute() method would return the input and output buffers via the promise
+  // resolution. Reuse the buffers to avoid additional allocation.
+  wnn_inputs_ = results["inputs"];
+  wnn_outputs_ = results["outputs"];
+
   return Status::OK();
 }
 

onnxruntime/core/providers/webnn/builders/model_builder.cc

@@ -386,7 +386,8 @@ Status ModelBuilder::Compile(std::unique_ptr<Model>& model) {
   for (auto& name : output_names_) {
     named_operands.set(name, wnn_operands_.at(name));
   }
-  emscripten::val wnn_graph = wnn_builder_.call<emscripten::val>("buildSync", named_operands);
+
+  emscripten::val wnn_graph = wnn_builder_.call<emscripten::val>("build", named_operands).await();
   if (!wnn_graph.as<bool>()) {
     return ORT_MAKE_STATUS(ONNXRUNTIME, FAIL, "Failed to build WebNN graph.");
   }
@@ -395,13 +396,10 @@ Status ModelBuilder::Compile(std::unique_ptr<Model>& model) {
   model->SetOutputs(std::move(output_names_));
   model->SetScalarOutputs(std::move(scalar_outputs_));
   model->SetInputOutputInfo(std::move(input_output_info_));
-#ifdef ENABLE_WEBASSEMBLY_THREADS
-  // Pre-allocate the input and output tensors for the WebNN graph
-  // when WebAssembly multi-threads is enabled since WebNN API only
-  // accepts non-shared ArrayBufferView.
-  // https://www.w3.org/TR/webnn/#typedefdef-mlnamedarraybufferviews
+  // Wasm heap is not transferrable, we have to pre-allocate the MLNamedArrayBufferViews
+  // for inputs and outputs because they will be transferred after compute() done.
+  // https://webmachinelearning.github.io/webnn/#api-mlcontext-async-execution
   model->AllocateInputOutputBuffers();
-#endif
   return Status::OK();
 }
 

onnxruntime/core/providers/webnn/webnn_execution_provider.cc

@@ -42,7 +42,8 @@ WebNNExecutionProvider::WebNNExecutionProvider(const std::string& webnn_device_f
   if (webnn_power_flags.compare("default") != 0) {
     context_options.set("powerPreference", emscripten::val(webnn_power_flags));
   }
-  wnn_context_ = ml.call<emscripten::val>("createContextSync", context_options);
+
+  wnn_context_ = ml.call<emscripten::val>("createContext", context_options).await();
   if (!wnn_context_.as<bool>()) {
     ORT_THROW("Failed to create WebNN context.");
   }

onnxruntime/wasm/js_internal_api.js

@@ -160,6 +160,10 @@ Module['jsepInit'] = (backend, alloc, free, copy, copyAsync, createKernel, relea
   };
 
   // replace the original functions with asyncified versions
+  Module['_OrtCreateSession'] = jsepWrapAsync(
+      Module['_OrtCreateSession'],
+      () => Module['_OrtCreateSession'],
+      v => Module['_OrtCreateSession'] = v);
   Module['_OrtRun'] = runAsync(jsepWrapAsync(
       Module['_OrtRun'],
       () => Module['_OrtRun'],