clean the unused control flow input nodes from the graph (tensorflow#…

…2287)

BUG
* clean the unused control flow input nodes from the graph

* increase tfjs-converter cloudbuild disk size

* use high cpu cloud build type

tfjs-converter/cloudbuild.yml

@@ -61,3 +61,4 @@ substitutions:
 options:
   logStreamingOption: 'STREAM_ON'
   substitution_option: 'ALLOW_LOOSE'
+  machineType: 'N1_HIGHCPU_8'

tfjs-converter/python/tensorflowjs/converters/tf_saved_model_conversion_v2.py

@@ -23,6 +23,8 @@
 
 import numpy as np
 import tensorflow as tf
+from tensorflow.core.framework import graph_pb2
+from tensorflow.core.framework import node_def_pb2
 from tensorflow.core.protobuf import config_pb2
 from tensorflow.core.protobuf import device_properties_pb2
 from tensorflow.core.protobuf import meta_graph_pb2
@@ -166,6 +168,7 @@ def optimize_graph(graph, signature_def, output_graph,
   ]
 
   optimized_graph = _run_grappler(config, optimized_graph, graph, signature_def)
+  optimized_graph = _remove_unused_control_flow_inputs(optimized_graph)
 
   # Because TF break the Prelu op into 6 ops, for performance we are
   # fusing those ops into a single prelu
@@ -268,6 +271,17 @@ def write_artifacts(topology,
   with open(output_graph, 'wt') as f:
     json.dump(model_json, f)
 
+def _remove_unused_control_flow_inputs(input_graph_def):
+  result_graph_def = graph_pb2.GraphDef()
+  for node in input_graph_def.node:
+    if (node.op == 'Placeholder' and
+        node.name.startswith('unused_control_flow_input')):
+      continue
+    new_node = node_def_pb2.NodeDef()
+    new_node.CopyFrom(node)
+    result_graph_def.node.extend([new_node])
+
+  return result_graph_def
 
 def _check_signature_in_model(saved_model, signature_name):
   if signature_name not in saved_model.signatures: