polish custom api content for performence (#32209)

python/paddle/utils/cpp_extension/extension_utils.py

@@ -793,19 +793,26 @@ def _custom_api_content(op_name):
     params_str, ins_str, attrs_str, outs_str = _get_api_inputs_str(op_name)
 
     API_TEMPLATE = textwrap.dedent("""
+        from paddle.fluid.core import VarBase
+        from paddle.fluid.framework import in_dygraph_mode, _dygraph_tracer
         from paddle.fluid.layer_helper import LayerHelper
 
         def {op_name}({inputs}):
-            helper = LayerHelper("{op_name}", **locals())
-
             # prepare inputs and outputs
             ins = {ins}
             attrs = {attrs}
             outs = {{}}
             out_names = {out_names}
+
+            # The output variable's dtype use default value 'float32',
+            # and the actual dtype of output variable will be inferred in runtime.
+            if in_dygraph_mode():
+                for out_name in out_names:
+                    outs[out_name] = VarBase()
+                _dygraph_tracer().trace_op(type="{op_name}", inputs=ins, outputs=outs, attrs=attrs)
+            else:
+                helper = LayerHelper("{op_name}", **locals())
                 for out_name in out_names:
-                # Set 'float32' temporarily, and the actual dtype of output variable will be inferred
-                # in runtime.
                     outs[out_name] = helper.create_variable(dtype='float32')
 
                 helper.append_op(type="{op_name}", inputs=ins, outputs=outs, attrs=attrs)