Merge pull request opencv#19373 from l-bat:lb/tf_matmul_shared

Author: alalek

modules/dnn/src/tensorflow/tf_importer.cpp

@@ -1228,8 +1228,18 @@ void TFImporter::parseNode(const tensorflow::NodeDef& layer_)
 
             int kernel_blob_index = -1;
             const tensorflow::TensorProto& kernelTensor = getConstBlob(layer, value_id, -1, &kernel_blob_index);
-            blobFromTensor(kernelTensor, layerParams.blobs[0]);
-            releaseTensor(const_cast<tensorflow::TensorProto*>(&kernelTensor));
+            const String kernelTensorName = layer.input(kernel_blob_index);
+            std::map<String, Mat>::iterator sharedWeightsIt = sharedWeights.find(kernelTensorName);
+            if (sharedWeightsIt == sharedWeights.end())
+            {
+                blobFromTensor(kernelTensor, layerParams.blobs[0]);
+                releaseTensor(const_cast<tensorflow::TensorProto*>(&kernelTensor));
+                sharedWeights[kernelTensorName] = layerParams.blobs[0];
+            }
+            else
+            {
+                layerParams.blobs[0] = sharedWeightsIt->second;
+            }
 
             if (kernel_blob_index == 1) { // In this case output is computed by x*W formula - W should be transposed
                 Mat data = layerParams.blobs[0].t();