add layer type index member

src/layer.cpp

@@ -223,7 +223,9 @@ Layer* create_layer(int index)
     if (!layer_creator)
         return 0;
 
-    return layer_creator();
+    Layer* layer = layer_creator();
+    layer->typeindex = index;
+    return layer;
 }
 
 } // namespace ncnn

src/layer.h

@@ -139,6 +139,8 @@ public:
 #endif // NCNN_VULKAN
 
 public:
+    // layer type index
+    int typeindex;
 #if NCNN_STRING
     // layer type name
     std::string type;