[Stitch] fix ext interface ordering for multi-I/O

src/finn/transformation/fpgadataflow/create_stitched_ip.py

@@ -223,8 +223,8 @@ class CreateStitchedIP(Transformation):
                 behavior. It is strongly recommended to insert FIFOs prior to
                 calling CreateStitchedIP."""
             )
-        # ensure that all nodes are fpgadataflow, and that IPs are generated
         for node in model.graph.node:
+            # ensure that all nodes are fpgadataflow, and that IPs are generated
             assert is_fpgadataflow_node(
                 node
             ), "All nodes must be FINN fpgadataflow nodes."
@@ -236,9 +236,7 @@ class CreateStitchedIP(Transformation):
             self.connect_clk_rst(node)
             self.connect_axi(node)
             for i in range(len(node.input)):
-                if is_external_input(model, node, i):
-                    self.connect_s_axis_external(node, idx=i)
-                else:
+                if not is_external_input(model, node, i):
                     producer = model.find_producer(node.input[i])
                     if producer is None:
                         continue
@@ -254,8 +252,25 @@ class CreateStitchedIP(Transformation):
                         "[get_bd_intf_pins %s/%s]"
                         % (producer.name, src_intf_name, node.name, dst_intf_name)
                     )
+
+        # process external inputs and outputs in top-level graph input order
+        for input in model.graph.input:
+            inp_name = input.name
+            inp_cons = model.find_consumers(inp_name)
+            assert inp_cons is not None, "No consumer for input " + inp_name
+            assert len(inp_cons) == 1, "Multiple consumers for input " + inp_name
+            node = inp_cons[0]
+            node_inst = getCustomOp(node)
+            for i in range(len(node.input)):
+                if node.input[i] == inp_name:
+                    self.connect_s_axis_external(node, idx=i)
+        for output in model.graph.output:
+            out_name = output.name
+            node = model.find_producer(out_name)
+            assert node is not None, "No producer for output " + out_name
+            node_inst = getCustomOp(node)
             for i in range(len(node.output)):
-                if is_external_output(model, node, i):
+                if node.output[i] == out_name:
                     self.connect_m_axis_external(node, idx=i)
 
         # create a temporary folder for the project