dnn/Vulkan: Refine error handle mechanism

Fallback to OPENCV backend and CPU target if catch exception from
vkcom backend.
Signed-off-by: Wu Zhiwen <zhiwen.wu@intel.com>

modules/dnn/src/dnn.cpp

@@ -1412,9 +1412,18 @@ struct Net::Impl
             }
 
             ld.skip = false;
+
+            try
+            {
                 ld.backendNodes[DNN_BACKEND_VKCOM] =
                     layer->initVkCom(ld.inputBlobsWrappers);
             }
+            catch (const cv::Exception& e)
+            {
+                CV_LOG_ERROR(NULL, "initVkCom failed, fallback to CPU implementation. " << e.what());
+                ld.backendNodes[DNN_BACKEND_VKCOM] = Ptr<BackendNode>();
+            }
+        }
 #endif
     }
 
@@ -2317,9 +2326,18 @@ struct Net::Impl
                     forwardInfEngine(node);
                 }
                 else if (preferableBackend == DNN_BACKEND_VKCOM)
+                {
+                    try
                     {
                         forwardVkCom(ld.outputBlobsWrappers, node);
                     }
+                    catch (const cv::Exception& e)
+                    {
+                        CV_LOG_ERROR(NULL, "forwardVkCom failed, fallback to CPU implementation. " << e.what());
+                        it->second = Ptr<BackendNode>();
+                        forwardLayer(ld);
+                    }
+                }
                 else
                 {
                     CV_Error(Error::StsNotImplemented, "Unknown backend identifier");

modules/dnn/src/vkcom/src/common.hpp

@@ -42,7 +42,8 @@ enum ShapeIdx
 { \
         if (f != VK_SUCCESS) \
         { \
-            CV_LOG_WARNING(NULL, "Vulkan check failed"); \
+            CV_LOG_ERROR(NULL, "Vulkan check failed, result = " << f); \
+            CV_Error(Error::StsError, "Vulkan check failed"); \
         } \
 }