Only remove cast pairs with fp32 input types.

onnxconverter_common/float16.py

@@ -6,14 +6,14 @@
 import itertools
 import uuid
 import warnings
+from typing import Optional
+
 import numpy as np
 import onnx
 import packaging.version as pv
-import warnings
 from onnx import helper, numpy_helper
 from onnx import onnx_pb as onnx_proto
 
-
 FLOAT32 = 1
 FLOAT16 = 10
 
@@ -522,10 +522,31 @@ def remove_unnecessary_cast_node(graph_proto: onnx_proto.GraphProto):
         if upstream_node.op_type == 'Constant':
             cast_node_list.remove(cast_node)
 
-    # 4. find the cast(to16) node which downstream is Cast(to32)
+    # 4. find (cast_to_fp16, cast_to_fp32) pairs where --fp32--> cast_to_fp16 --fp16--> cast_to_fp32.
     remove_candidate = []
+
+    name_to_value_info = {
+        value_info.name: value_info for value_info in itertools.chain(graph_proto.value_info, graph_proto.input)
+    }
+
+    def get_type(name: str) -> Optional[int]:
+        if name in name_to_value_info:
+            return name_to_value_info[name].type
+        else:
+            # `name` has no value info.
+            return None
+
     for cast_node_name, downstream_node in cast_node_downstream_dict.items():
         cast_node = name_to_node_dict[cast_node_name]
+        if len(cast_node.input) != 1:
+            raise RuntimeError(
+                f"Cast node {cast_node_name} should have only one input, but has {len(cast_node.input)}."
+            )
+
+        input_type = get_type(cast_node.input[0])
+        if input_type != onnx_proto.TensorProto.FLOAT:
+            continue
+
         if isinstance(downstream_node, list):
             for dn in downstream_node:
                 if dn.op_type == 'Cast' and \
@@ -542,7 +563,8 @@ def remove_unnecessary_cast_node(graph_proto: onnx_proto.GraphProto):
                 cast_node in cast_node_list:
                 remove_candidate.append((cast_node, downstream_node))
 
-    # 5. change the connection of "upstream->cast16->cast32->downstream" to "upstream->downstream"
+    # 5. change "upstream --fp32--> cast_to_fp16 --fp16--> cast_to_fp32 --fp32--> downstream" to
+    # "upstream --fp32--> downstream".
     for cast_node_pair in remove_candidate:
         first_cast_node = cast_node_pair[0]
         second_cast_node = cast_node_pair[1]