add test_mode in trt/activation_op

paddle/fluid/inference/tensorrt/convert/activation_op.cc

@@ -23,7 +23,7 @@ class ReluOpConverter : public OpConverter {
  public:
   ReluOpConverter() {}
   void operator()(const framework::proto::OpDesc& op,
-                  const framework::Scope& scope) override {
+                  const framework::Scope& scope, bool test_mode) override {
     // Here the two nullptr looks strange, that's because the
     // framework::OpDesc's constructor is strange.
     framework::OpDesc op_desc(op, nullptr);
@@ -34,7 +34,12 @@ class ReluOpConverter : public OpConverter {
     nvinfer1::IActivationLayer* layer = TRT_ENGINE_ADD_LAYER(
         engine_, Activation, *const_cast<nvinfer1::ITensor*>(input_tensor),
         nvinfer1::ActivationType::kRELU);
-    engine_->DeclareOutput(layer, 0, op_desc.Output("Out")[0]);
+    auto output_name = op_desc.Output("Out")[0];
+    engine_->SetITensor(output_name, layer->getOutput(0));
+    if (test_mode) {  // the test framework can not determine which is the
+                      // output, so place the declaration inside.
+      engine_->DeclareOutput(output_name);
+    }
   }
 };