IVGCVSW-6978: RedirectMembersToConstantInputs does not work with Fp32NetworkToBf16Converter

 * Fuse FP32ToBF16Layers with Constant Layer so Conv2d/FullyConnected
   can have their weights redirected.
 * If BF16 Unsupported in Conv2d || FullyConnected revert fused
   Constant Layer to FP32

Change-Id: If523c708a822659d64597d9ae39cca1c2f84b76f
Signed-off-by: Francis Murtagh <francis.murtagh@arm.com>

1 files changed, 49 insertions, 1 deletions

diff --git a/src/armnn/NetworkUtils.cpp b/src/armnn/NetworkUtils.cpp
index 7597798fa4..5ff0e6c4e1 100644
--- a/src/armnn/NetworkUtils.cpp
+++ b/src/armnn/NetworkUtils.cpp
@@ -1,10 +1,12 @@
 //
-// Copyright © 2017 Arm Ltd. All rights reserved.
+// Copyright © 2022 Arm Ltd and Contributors. All rights reserved.
 // SPDX-License-Identifier: MIT
 //
 
 #include "NetworkUtils.hpp"
 
+#include <armnnUtils/FloatingPointConverter.hpp>
+#include <BFloat16.hpp>
 #include "SubgraphViewSelector.hpp"
 
 #include <armnn/Exceptions.hpp>
@@ -272,4 +274,50 @@ std::vector<DebugLayer*> InsertDebugLayerAfter(Graph& graph, Layer& layer)
     return debugLayers;
 }
 
+bool RevertConstantWeightsToFP32(Layer* layer)
+{
+    if (layer->GetType() == LayerType::Convolution2d || layer->GetType() == LayerType::FullyConnected)
+    {
+        // Revert Weights on Constant Layer to FP32 so they can be accessed by Conv2d or FullyConnected
+        // This prevents a conversion layer being added in during backend assignment which blocks
+        // the RedirectMembersToConstantInputs backward compatibility workaround/optimization.
+        auto constantLayerInfo = layer->GetInputSlot(1).GetConnection()->GetTensorInfo();
+
+        if (constantLayerInfo.IsConstant() && constantLayerInfo.GetDataType() == DataType::BFloat16)
+        {
+            std::vector<float> newValues(constantLayerInfo.GetNumElements());
+
+            auto weightLayer = PolymorphicDowncast<ConstantLayer*>(
+                    &layer->GetInputSlot(1).GetConnection()->GetOwningIConnectableLayer());
+            armnnUtils::FloatingPointConverter::ConvertBFloat16ToFloat32(
+                    weightLayer->m_LayerOutput->GetConstTensor<BFloat16>(),
+                    constantLayerInfo.GetNumElements(),
+                    newValues.data());
+
+            TensorInfo newInfo(constantLayerInfo.GetShape(), DataType::Float32);
+            newInfo.SetConstant(true);
+            ConstTensor newInput(newInfo, newValues);
+            weightLayer->m_LayerOutput.reset(new ScopedTensorHandle(newInput));
+            weightLayer->GetOutputSlot(0).SetTensorInfo(newInfo);
+
+            // Connect Conv2d/FullyConnected to InputLayer directly leaving out
+            // the ConversionLayer to be cleaned up later
+            auto& conversionLayer = layer->GetInputSlot(0).GetConnection()->GetOwningIConnectableLayer();
+            auto actualInputOutputSlot = conversionLayer.GetInputSlot(0).GetConnection();
+
+            auto& conversionLayerOutputSlot =
+                    layer->GetInputSlot(0).GetConnection()->GetOwningIConnectableLayer().GetOutputSlot(0);
+            auto& conversionLayerInputSlot =
+                    layer->GetInputSlot(0).GetConnection()->GetOwningIConnectableLayer().GetInputSlot(0);
+            actualInputOutputSlot->Disconnect(conversionLayerInputSlot);
+            conversionLayerOutputSlot.Disconnect(layer->GetInputSlot(0));
+
+            actualInputOutputSlot->Connect(layer->GetInputSlot(0));
+
+            return true;
+        }
+    }
+    return false;
+}
+
 } // namespace armnn