Fixed a bug where node insertion of the QuantActBaseHandler would fail at the end of a graph.

src/finn/transformation/qonnx/qonnx_activation_handlers.py

@@ -152,7 +152,8 @@ class QuantActBaseHandler(ABC):
         running_node_index += 1
 
         # Get the MultiThreshold node instance to work with
-        mt_inst = getCustomOp(graph.node[running_node_index - 1])
+        mt_node = graph.node[running_node_index - 1]
+        mt_inst = getCustomOp(mt_node)
 
         # Set scale and bias
         # If these values are scalar then they can be set as attributes
@@ -184,10 +185,7 @@ class QuantActBaseHandler(ABC):
             mt_inst.set_nodeattr("out_dtype", out_dtype)
 
             # Insertion parameters
-            in_tensor = n.output[0]
-            successor_node = model.find_direct_successors(n)
-            if successor_node is not None:
-                successor_node = successor_node[0]
+            up_stream_node = mt_node
 
             # Set bias
             zero_bias = False
@@ -218,19 +216,19 @@ class QuantActBaseHandler(ABC):
                     output_shape,
                 )
                 graph.value_info.append(act_add_tensor)
-                if successor_node is not None:
-                    successor_node.input[0] = act_add_tensor.name
 
                 add_node = helper.make_node(
                     "Add",
-                    [in_tensor, add_tensor.name],
-                    [act_add_tensor.name],
+                    [act_add_tensor.name, add_tensor.name],
+                    [n.output[0]],
                 )
                 graph.node.insert(running_node_index, add_node)
                 running_node_index += 1
+                add_node = graph.node[running_node_index - 1]
 
-                # Re-point the input node for the next node to insert
-                in_tensor = act_add_tensor.name
+                # Re-point the upstream node
+                up_stream_node.output[0] = act_add_tensor.name
+                up_stream_node = add_node
 
             # Set scale
             # Insert Mul node
@@ -260,16 +258,19 @@ class QuantActBaseHandler(ABC):
                     output_shape,
                 )
                 graph.value_info.append(act_mul_tensor)
-                if successor_node is not None:
-                    successor_node.input[0] = act_mul_tensor.name
 
                 mul_node = helper.make_node(
                     "Mul",
-                    [in_tensor, mul_tensor.name],
-                    [act_mul_tensor.name],
+                    [act_mul_tensor.name, mul_tensor.name],
+                    [n.output[0]],
                 )
                 graph.node.insert(running_node_index, mul_node)
                 running_node_index += 1
+                mul_node = graph.node[running_node_index - 1]
+
+                # Re-point the upstream node
+                up_stream_node.output[0] = act_mul_tensor.name
+                up_stream_node = mul_node
 
         # Remove activation node
         self._remove_activation_node()