[WebNN EP] Update argMax/argMin to adapt to latest spec

WebNN spec recently changes the definition of argMax/argMin:
- Remove selectLastIndex option, let backends decide the selected the index.
- Move axes option to axis input

js/web/docs/webnn-operators.md

@@ -13,8 +13,8 @@ operators and the supported opset domain/versions in **WebNN EP** by ONNX Runtim
 |:------:|:------:|:------:|:-:|:-:|:------|
 | Abs | ai.onnx(7-12, 13+) | abs | ✓ | ✓ | |
 | Add | ai.onnx(7-12, 13, 14+) | add | ✓ | ✓ | |
-| ArgMax | ai.onnx(7-10, 11, 12, 13+) | argMax | ✓ | ✓ | WebNN CPU backend only supports 'select_last_index' value is 0 |
-| ArgMin | ai.onnx(7-10, 11, 12, 13+) | argMin | ✓ | ✓ | WebNN CPU backend only supports 'select_last_index' value is 0 |
+| ArgMax | ai.onnx(7-10, 11, 12, 13+) | argMax | ✓ | ✓ | |
+| ArgMin | ai.onnx(7-10, 11, 12, 13+) | argMin | ✓ | ✓ | |
 | AveragePool | ai.onnx(7-9, 10, 11, 12-18, 19+) | averagePool2d | ✓ | ✓ | Only supports 4-D input, 2-D 'kernel_shape', 'count_include_pad' value is 0 |
 | BatchNormalization | ai.onnx(7-8, 9-13, 14, 15+) | batchNormalization | ✓ | ✓ | Only supports 'training_mode' value is 0, one output |
 | Cast | ai.onnx(7-8, 9-12, 13-18, 19-20, 21+) | cast | ✓ | ✓ | WebNN CPU backend doesn't support casting to uint64 data type |

onnxruntime/core/providers/webnn/builders/impl/argmax_min_op_builder.cc

@@ -40,28 +40,20 @@ Status ArgMaxMinOpBuilder::AddToModelBuilderImpl(ModelBuilder& model_builder,
   NodeAttrHelper helper(node);
   int64_t axis = helper.Get("axis", 0);
   const auto keep_dims = helper.Get("keepdims", 1);
-  const auto select_last_index = helper.Get("select_last_index", 0);
 
   axis = HandleNegativeAxis(axis, input_rank);
-  emscripten::val axes = emscripten::val::array();
-  axes.call<void>("push", static_cast<uint32_t>(axis));
 
   emscripten::val options = emscripten::val::object();
-  options.set("axes", axes);
   options.set("keepDimensions", keep_dims == 1);
-  options.set("selectLastIndex", select_last_index == 1);
-  // TODO: use WebNN's opSupportLimits API to check the backend's supported output data types.
-  // If the backend doesn't support int64 output, we should use default int32 output data type
-  // then do a type casting (int32 -> int64) for the output. Refer to the CoreML EP for how to
-  // support int64 output.
+  // TODO(Honry): check whether int64 output data type is supported by WebNN opSupportLimits() API.
   options.set("outputDataType", "int64");
   emscripten::val output = emscripten::val::object();
 
   const auto& op_type = node.OpType();
   if (op_type == "ArgMax") {
-    output = model_builder.GetBuilder().call<emscripten::val>("argMax", input, options);
+    output = model_builder.GetBuilder().call<emscripten::val>("argMax", input, narrow<uint32_t>(axis), options);
   } else if (op_type == "ArgMin") {
-    output = model_builder.GetBuilder().call<emscripten::val>("argMin", input, options);
+    output = model_builder.GetBuilder().call<emscripten::val>("argMin", input, narrow<uint32_t>(axis), options);
   } else {
     return ORT_MAKE_STATUS(ONNXRUNTIME, INVALID_ARGUMENT, "ArgMaxMinOpBuilder, unknown op: ", op_type);
   }
@@ -81,15 +73,6 @@ bool ArgMaxMinOpBuilder::IsOpSupportedImpl(const InitializedTensorSet& /* initia
   if (!GetShape(*input_defs[0], input_shape, logger))
     return false;
 
-  // WebNN CPU backend only supports select_last_index = 0.
-  if (device_type == WebnnDeviceType::CPU) {
-    NodeAttrHelper helper(node);
-    const auto select_last_index = helper.Get("select_last_index", 0);
-    if (select_last_index) {
-      LOGS(logger, VERBOSE) << "ArgMax/ArgMin with select_last_index = 1 is not supported on WebNN CPU backend.";
-      return false;
-    }
-  }
   return true;
 }