MLBEDSW-7458: Fused activation not passed through correctly

- Fixed a problem where the fused activation got lost
when the op was passed through to the CPU
- The fix is to always make sure the attribute is not removed

Change-Id: I612cfa8f6f0a0465459080762094fe61e7ddc1c3
Signed-off-by: Johan Alfven <johan.alfven@arm.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/ethosu/vela/tflite_reader.py b/ethosu/vela/tflite_reader.py
index 18b61e75..061f3626 100644
--- a/ethosu/vela/tflite_reader.py
+++ b/ethosu/vela/tflite_reader.py
@@ -209,7 +209,12 @@ class TFLiteSubgraph:
                 # The original value is cached above in channel_multiplier
                 op.attrs["depth_multiplier"] = op.weights.shape[2] // op.ifm.shape[-1]
 
-            faf = op.attrs.pop("fused_activation_function", None)
+            # The fused_activation_function attribute needs to be retained so that the
+            # tflite_writer can correctly pass through operators that run on the CPU.
+            # This is because the operator activation attribute is later converted to an
+            # NpuActivation which treats None and ReLU the same, thereby making it difficult
+            # for the tflite_writer to recover the original activation function.
+            faf = op.attrs.get("fused_activation_function", None)
             if faf is not None:
                 op.activation = create_activation_function(faf)
             if custom_code is not None: