Merge remote-tracking branch 'upstream/3.4' into merge-3.4

modules/dnn/src/layers/const_layer.cpp

@@ -9,6 +9,7 @@
 #include "../op_inf_engine.hpp"
 #include "../op_cuda.hpp"
 #include "layers_common.hpp"
+#include "../ie_ngraph.hpp"
 
 #ifdef HAVE_OPENCL
 #include "opencl_kernels_dnn.hpp"
@@ -34,6 +35,7 @@ public:
     {
         return backendId == DNN_BACKEND_OPENCV ||
                backendId == DNN_BACKEND_INFERENCE_ENGINE_NN_BUILDER_2019 ||
+               backendId == DNN_BACKEND_INFERENCE_ENGINE_NGRAPH ||
                backendId == DNN_BACKEND_CUDA;
     }
 
@@ -82,6 +84,17 @@ public:
     }
 #endif  // HAVE_INF_ENGINE
 
+#ifdef HAVE_DNN_NGRAPH
+    virtual Ptr<BackendNode> initNgraph(const std::vector<Ptr<BackendWrapper> >& inputs,
+                                        const std::vector<Ptr<BackendNode> >& nodes) CV_OVERRIDE
+    {
+        auto node = std::make_shared<ngraph::op::Constant>(ngraph::element::f32,
+                                                           getShape<size_t>(blobs[0]),
+                                                           blobs[0].data);
+        return Ptr<BackendNode>(new InfEngineNgraphNode(node));
+    }
+#endif  // HAVE_INF_ENGINE
+
 #ifdef HAVE_CUDA
     Ptr<BackendNode> initCUDA(
         void *context_,