1 files changed, 41 insertions, 4 deletions

diff --git a/src/armnn/layers/ConcatLayer.cpp b/src/armnn/layers/ConcatLayer.cpp
index d9fffff57e..fac6a1f197 100644
--- a/src/armnn/layers/ConcatLayer.cpp
+++ b/src/armnn/layers/ConcatLayer.cpp
@@ -36,7 +36,7 @@ std::unique_ptr<IWorkload> ConcatLayer::CreateWorkload(const IWorkloadFactory& f
 }
 
 template<typename FactoryType>
-void ConcatLayer::CreateTensors(const FactoryType& factory)
+void ConcatLayer::CreateTensors(const TensorHandleFactoryRegistry& registry, const FactoryType& factory)
 {
     //If sub tensors are supported then the concat
     //just needs to make sure that the outputs of the prev layer
@@ -45,6 +45,12 @@ void ConcatLayer::CreateTensors(const FactoryType& factory)
 
     if (factory.SupportsSubTensors())
     {
+        // check if concat is along the x or y (2 innermost dimensions)
+        uint32_t concatAxis = m_Param.GetConcatAxis();
+        auto numberOfDimensions = m_Param.GetNumDimensions();
+        bool isConcatOnXorY = m_Param.GetNumDimensions() >= 3
+                                && ((concatAxis == numberOfDimensions - 1) || (concatAxis == numberOfDimensions - 2));
+
         ITensorHandleFactory::FactoryId factoryId = GetOutputSlot(0).GetTensorHandleFactoryId();
 
         std::queue<ConcatLayer*> m_ConcatLayers;
@@ -59,6 +65,35 @@ void ConcatLayer::CreateTensors(const FactoryType& factory)
 
             const unsigned int numInputSlots = currentLayer->GetNumInputSlots();
 
+            // if concat along x or y (2 innermost dimensions) and the previous layers do not require padding
+            bool canUseSubTensorOnXorY = true;
+            bool isTensorHandleFactory = std::is_same<armnn::ITensorHandleFactory, FactoryType>::value;
+            if (isTensorHandleFactory)
+            {
+                for (unsigned int i = 0; i < numInputSlots; ++i)
+                {
+                    OutputSlot* slot = currentLayer->GetInputSlot(i).GetConnectedOutputSlot();
+                    ITensorHandleFactory* handleFactory  = registry.GetFactory(factoryId);
+                    std::vector<Capability> capabilities =
+                        handleFactory->GetCapabilities(&(slot->GetOwningLayer()),
+                                                       currentLayer,
+                                                       CapabilityClass::PaddingRequired);
+                    if (isConcatOnXorY)
+                    {
+                        canUseSubTensorOnXorY = false;
+                        if (capabilities.empty())
+                        {
+                            canUseSubTensorOnXorY = true;
+                        }
+                    }
+
+                    if (!canUseSubTensorOnXorY)
+                    {
+                        break;
+                    }
+                }
+            }
+
             // First go through all the input slots and verify that we can sub-tensor all the inputs.
             std::vector<std::unique_ptr<ITensorHandle>> subTensors(0);
             subTensors.reserve(numInputSlots);
@@ -74,12 +109,14 @@ void ConcatLayer::CreateTensors(const FactoryType& factory)
                     // 2) the same TensorHandleFactory is used for input and Concat layer output
                     // 3) the input does not come from a Constant layer or input layer
                     // 4) the input is only read by this concat layer
+                    // 5) if concat along x or y (2 innermost dimensions) and the previous layers do not require padding
                     if (slot &&
                         parentInfo.IsTypeSpaceMatch(info) && //(1)
                         factoryId == slot->GetTensorHandleFactoryId() && //(2)
                         slot->GetOwningLayer().GetType() != LayerType::Constant && //(3)
                         slot->GetOwningLayer().GetType() != LayerType::Input && //(3)
-                        slot->GetNumConnections() == 1) //(4)
+                        slot->GetNumConnections() == 1 &&
+                        canUseSubTensorOnXorY) //(5)
                     {
                         return factory.CreateSubTensorHandle(*parentTensor,
                                                              info.GetShape(),
@@ -137,13 +174,13 @@ void ConcatLayer::CreateTensorHandles(const TensorHandleFactoryRegistry& registr
 
     if (factoryId == ITensorHandleFactory::LegacyFactoryId)
     {
-        CreateTensors(workloadFactory);
+        CreateTensors(registry, workloadFactory);
     }
     else
     {
         ITensorHandleFactory* handleFactory = registry.GetFactory(factoryId);
         ARMNN_ASSERT(handleFactory);
-        CreateTensors(*handleFactory);
+        CreateTensors(registry, *handleFactory);
     }
 }