[LITE][DOC] add profiler info in develop guide for add_operation.md. test=develop (#3711)

docs/develop_guides/add_operation.md

@@ -27,6 +27,28 @@
         bool AttachImpl(const cpp::OpDesc &opdesc, lite::Scope *scope) override;
         void AttachKernel(KernelBase *kernel) override { kernel->SetParam(param_); }
         std::string DebugString() const override { return "argmax"; }
+
+    #ifdef LITE_WITH_PROFILE
+        void GetOpRuntimeInfo(paddle::lite::profile::OpCharacter *ch) {
+            auto input_dims = param_.X->dims();
+            auto output_dims = param_.Out->dims();
+            ch->input_shape = ch->DimToStr(input_dims);
+            ch->output_shape = ch->DimToStr(output_dims);
+            ch->remark = "axis" + std::to_string(param_.Axis);
+
+            auto axis = param_.Axis;
+            if (axis < 0) {
+                axis += input_dims.size();
+            }
+            int max_num = 1;
+            for (int64_t i = axis + 1; i < input_dims.size(); i++)
+                max_num *= input_dims[i];
+            float gops = 1.0f;
+            for (int i = 1; i <= max_num; i++) gops *= i;
+            ch->macs = gops * output_dims.production();
+        }
+    #endif
+
     private:
         mutable ArgmaxParam param_;
     };