[DoubleGrad PR #1] Decoupled code generation logics for Dygraph...

[DoubleGrad PR #1] Decoupled code generation logics for Dygraph ForwardFunctions and GradNodes (#40937)

* [Refactor] refactored eager_gen.py PR #2

* [DoubleGrad PR #1] Decoupled code generation logics for Dygraph ForwardFunctions and GradNodes

* Fixed minor issue

paddle/fluid/eager/auto_code_generator/final_state_generator/python_c_gen.py

@@ -311,7 +311,7 @@ class PythonCSingleFunctionGenerator(FunctionGeneratorBase):
             dygraph_function_call_list[pos] = f"{name}"
         dygraph_function_call_str = ",".join(dygraph_function_call_list)
 
-        # Generate Python-C Function Definitions
+        # Generate Python-C Function Definitions 
         if is_forward_only:
             fwd_function_name = FUNCTION_NAME_TEMPLATE.format(
                 "paddle::experimental::", namespace, forward_api_name)
@@ -337,21 +337,21 @@ class PythonCSingleFunctionGenerator(FunctionGeneratorBase):
             forward_api_name_prefix, forward_api_name, namespace,
             forward_api_name, forward_api_name)
 
-        if len(inplace_map) > 0:
-            assert len(
-                inplace_map
-            ) == 1, f"size of inplace_map must be 1, but inplace_map of \"{forward_api_name}\" op got {len(inplace_map)}"
+        if inplace_map:
             inplaced_forward_api_name = GetInplacedFunctionName(
                 self.forward_api_name)
-            # Generate Python-C Function Definitions
             if is_forward_only:
-                fwd_function_name = FUNCTION_NAME_TEMPLATE.format(
+                inplaced_fwd_function_name = FUNCTION_NAME_TEMPLATE.format(
                     "paddle::experimental::", namespace,
                     inplaced_forward_api_name)
-            elif len(inplace_map) > 0:
-                fwd_function_name = FUNCTION_NAME_TEMPLATE.format(
+            else:
+                inplaced_fwd_function_name = FUNCTION_NAME_TEMPLATE.format(
                     "::", namespace,
                     GetForwardFunctionName(inplaced_forward_api_name))
+
+            assert len(
+                inplace_map
+            ) == 1, f"size of inplace_map must be 1, but inplace_map of \"{forward_api_name}\" op got {len(inplace_map)}"
             for inplace_input, inplace_output in inplace_map.items():
                 return_str = RETURN_INPLACE_PYOBJECT_TEMPLATE.format(
                     inplaced_forward_api_name, inplace_input,
@@ -361,7 +361,7 @@ class PythonCSingleFunctionGenerator(FunctionGeneratorBase):
             self.python_c_function_str += PYTHON_C_FUNCTION_TEMPLATE.format(
                 inplaced_forward_api_name, pythonc_record_event_str,
                 inplaced_forward_api_name, get_eager_tensor_str,
-                parse_attributes_str, fwd_function_name,
+                parse_attributes_str, inplaced_fwd_function_name,
                 dygraph_function_call_str, return_str)
 
             # Generate Python-C Function Registration