IVGCVSW-3836 Add support for Int32 per-axis scales

* Added ScaledInt32PerAxisDecoder implementation
* Added new case for Signed32 in MakeDecoder that returns a
  ScaledInt32PerAxisDecoder if the tensor info has multiple
  quantization scales

Signed-off-by: Aron Virginas-Tar <Aron.Virginas-Tar@arm.com>
Change-Id: I8b3c11091644da993044d2a0fe2aba6b06b5af56

2 files changed, 71 insertions, 8 deletions

diff --git a/src/backends/reference/workloads/BaseIterator.hpp b/src/backends/reference/workloads/BaseIterator.hpp
index 9fe3f15f9b..50475312a5 100644
--- a/src/backends/reference/workloads/BaseIterator.hpp
+++ b/src/backends/reference/workloads/BaseIterator.hpp
@@ -451,4 +451,25 @@ private:
     std::vector<float> m_Scale;
 };
 
-} //namespace armnn
\ No newline at end of file
+class ScaledInt32PerAxisDecoder : public PerAxisIterator<const int32_t, Decoder<float>>
+{
+public:
+    ScaledInt32PerAxisDecoder(const int32_t* data, const std::vector<float>& scales, unsigned int axisFactor)
+        : PerAxisIterator(data, axisFactor), m_Scales(scales) {}
+
+    float Get() const override
+    {
+        return armnn::Dequantize(*m_Iterator, m_Scales[m_AxisIndex], 0);
+    }
+
+    // Get scale of the current value
+    float GetScale() const
+    {
+        return m_Scales[m_AxisIndex];
+    }
+
+private:
+    std::vector<float> m_Scales;
+};
+
+} // namespace armnn
diff --git a/src/backends/reference/workloads/Decoders.hpp b/src/backends/reference/workloads/Decoders.hpp
index dd2b28a50f..dcd498cb63 100644
--- a/src/backends/reference/workloads/Decoders.hpp
+++ b/src/backends/reference/workloads/Decoders.hpp
@@ -14,6 +14,54 @@
 namespace armnn
 {
 
+namespace
+{
+
+inline std::unique_ptr<Decoder<float>> MakeSigned32PerAxisDecoder(const TensorInfo& info, const void* data)
+{
+    auto params = armnnUtils::GetPerAxisParams(info);
+    return std::make_unique<ScaledInt32PerAxisDecoder>(
+        static_cast<const int32_t*>(data),
+        params.second,
+        params.first);
+}
+
+inline std::unique_ptr<Decoder<float>> MakeSigned32Decoder(const TensorInfo& info, const void* data)
+{
+    if(info.HasMultipleQuantizationScales())
+    {
+        // NOTE: If we have multiple quantization scales, we create a ScaledInt32PerAxisDecoder.
+        // This will be used to decode per-axis quantized convolution biases.
+        return MakeSigned32PerAxisDecoder(info, data);
+    }
+    else
+    {
+        if (info.GetQuantizationDim().has_value())
+        {
+            // NOTE: Even though we only have a single quantization scale, if the quantization
+            // dimension is set, the tensor has per-axis quantization and we need to create a
+            // ScaledInt32PerAxisDecoder
+            return MakeSigned32PerAxisDecoder(info, data);
+        }
+
+        const float scale = info.GetQuantizationScale();
+        if (scale == 0.f)
+        {
+            // NOTE:: If no quantization scale is set, we create an Int32Decoder, which simply
+            // casts the int value to float. This will be used for any INT32 data other than
+            // convolution biases.
+            return std::make_unique<Int32Decoder>(static_cast<const int32_t*>(data));
+        }
+
+        // NOTE: If we only have a single (non-zero) quantization scale and no quantization
+        // dimension is specified, we need to create a ScaledInt32Decoder. This will be used
+        // to decode per-tensor quantized convolution biases.
+        return std::make_unique<ScaledInt32Decoder>(static_cast<const int32_t*>(data), scale);
+    }
+}
+
+} // anonymous namespace
+
 template<typename T>
 inline std::unique_ptr<Decoder<T>> MakeDecoder(const TensorInfo& info, const void* data = nullptr);
 
@@ -54,13 +102,7 @@ inline std::unique_ptr<Decoder<float>> MakeDecoder(const TensorInfo& info, const
         }
         case DataType::Signed32:
         {
-            const float scale = info.GetQuantizationScale();
-            if (scale == 0.f)
-            {
-                return std::make_unique<Int32Decoder>(static_cast<const int32_t*>(data));
-            }
-            // NOTE: ScaledInt32Decoder is used for quantized convolution biases
-            return std::make_unique<ScaledInt32Decoder>(static_cast<const int32_t*>(data), scale);
+            return MakeSigned32Decoder(info, data);
         }
         default:
         {