From 3883b2776cec33f16f0ea9a2d795de2b7c766df7 Mon Sep 17 00:00:00 2001
From: Cathal Corbett <cathal.corbett@arm.com>
Date: Fri, 22 Jul 2022 16:03:36 +0100
Subject: GitHub #667: Neon fold padding into average pool 2D quantization bug
 fix.

  * Originated from a GitHub issue: https://github.com/ARM-software/armnn/issues/667
  * Initially, Arm NN supports the pool 2D operation because there is no padding
    on the pool2d. Neon failure occurs when padding is followed by average pool 2D
    due to folding optimization.
  * Here we prevent the folding optimization from happening for the above special case
    and add it in as a backend specific optimization.

Signed-off-by: Cathal Corbett <cathal.corbett@arm.com>
Change-Id: Ia0fd90c3a6b4b9d29c81106f154617d2e893e26b
---
 src/backends/reference/RefBackend.cpp | 59 ++++++++++++++++++++++++++++++++---
 1 file changed, 55 insertions(+), 4 deletions(-)

(limited to 'src/backends/reference/RefBackend.cpp')

diff --git a/src/backends/reference/RefBackend.cpp b/src/backends/reference/RefBackend.cpp
index a33a7756a0..8c8879c8be 100644
--- a/src/backends/reference/RefBackend.cpp
+++ b/src/backends/reference/RefBackend.cpp
@@ -14,6 +14,7 @@
 #include <armnn/backends/IMemoryManager.hpp>
 #include <armnn/utility/PolymorphicDowncast.hpp>
 #include <backendsCommon/DefaultAllocator.hpp>
+#include <backendsCommon/SubgraphUtils.hpp>
 
 #include <Optimizer.hpp>
 
@@ -70,11 +71,61 @@ IBackendInternal::ILayerSupportSharedPtr RefBackend::GetLayerSupport() const
     return layerSupport;
 }
 
-OptimizationViews RefBackend::OptimizeSubgraphView(const SubgraphView& subgraph) const
+OptimizationViews RefBackend::OptimizeSubgraphView(const SubgraphView& subgraph,
+                                                   const ModelOptions& modelOptions) const
 {
-    OptimizationViews optimizationViews;
-
-    optimizationViews.AddUntouchedSubgraph(SubgraphView(subgraph));
+    OptimizationViews optimizationViews(modelOptions);
+
+    auto it = subgraph.endIConnectable();
+    std::map<LayerGuid, Layer*> untouched;
+
+    while (it != subgraph.beginIConnectable())
+    {
+        --it;
+        Layer& base = *(PolymorphicDowncast<Layer*>(*it));
+        untouched.insert({base.GetGuid(), &base});
+    }
+
+    it = subgraph.endIConnectable();
+    while (it != subgraph.beginIConnectable())
+    {
+        --it;
+        Layer& base = *(PolymorphicDowncast<Layer*>(*it));
+
+        // Special case to fuse padding into average pooling 2d for quantized datatype.
+        // Required to be done as a backend specific optimization as Neon does not support this special case.
+        if (base.GetType() == LayerType::Pooling2d)
+        {
+            Pooling2dLayer* baseLayer = PolymorphicDowncast<Pooling2dLayer*>(&base);
+            Pooling2dDescriptor poolingDescriptor = baseLayer->GetParameters();
+
+            if (baseLayer->GetInputSlot(0).GetConnectedOutputSlot()->GetOwningLayer().GetType() == LayerType::Pad)
+            {
+                PadLayer* padLayer = PolymorphicDowncast<PadLayer*>(
+                    &baseLayer->GetInputSlot(0).GetConnectedOutputSlot()->GetOwningLayer());
+                if (padLayer->GetOutputSlot(0).GetNumConnections() == 1 &&
+                    optimizations::pad_fold::TryFoldPadIntoLayer2d(padLayer->GetParameters(),
+                                                                   poolingDescriptor,
+                                                                   padLayer->GetOutputSlot().GetTensorInfo(),
+                                                                   true))
+                {
+                    FoldPadIntoAveragePool2d<Pooling2dLayer>(optimizationViews, baseLayer,
+                                                             poolingDescriptor, padLayer);
+                    untouched.erase(baseLayer->GetGuid());
+                    untouched.erase(padLayer->GetGuid());
+                }
+            }
+        }
+    }
+
+    if (optimizationViews.GetSubstitutions().empty())
+    {
+        optimizationViews.AddUntouchedSubgraph(SubgraphView(subgraph));
+    }
+    else
+    {
+        ReportUntouchedLayers(optimizationViews, untouched);
+    }
 
     return optimizationViews;
 }
-- 
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