Supported intermediate outputs for eager final state codegen (#39767)

* Supported intermediate outputs for eager final state codegen

* Added validation check for intermediate tensors

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

@@ -127,6 +127,26 @@ def ReadBwdFile(filepath):
 ######################
 ###  Yaml Parsers  ###
 ######################
+def IntermediateValidationCheck(intermediate_outputs, forward_returns_list):
+    # intermediate_outputs : [name0, name1, ...]
+    # forward_returns_list : [[ret_name, type, orig_pos], ...]
+    """
+    Check whether intermediate_outputs are positioned
+    at the very end of forward_returns_list
+    """
+
+    intermediate_positions = range(
+        len(forward_returns_list) - len(intermediate_outputs),
+        len(forward_returns_list))
+    for ret_name, _, pos in forward_returns_list:
+        if ret_name in intermediate_outputs:
+            assert pos in intermediate_positions
+
+
+def ParseIntermediate(string):
+    return [v.strip() for v in string.split(",")]
+
+
 def ParseNoNeedBuffer(string):
     # string: "x, y"
     no_need_buffer_set = set()
@@ -742,11 +762,11 @@ def GenerateNodeCreationCodes(fwd_api_name, bwd_api_name,
     return node_creation_str
 
 
-def GenerateForwardDefinition(fwd_api_name, bwd_api_name,
-                              forward_inputs_position_map,
-                              forward_outputs_position_map, forward_attrs_list,
-                              backward_fwd_input_map, backward_grad_input_map,
-                              backward_grad_output_map, backward_attrs_list):
+def GenerateForwardDefinition(
+        fwd_api_name, bwd_api_name, forward_inputs_position_map,
+        forward_outputs_position_map, forward_attrs_list,
+        backward_fwd_input_map, backward_grad_input_map,
+        backward_grad_output_map, backward_attrs_list, intermediate_outputs):
     # fwd_api_name = ""
     # forward_inputs_position_map = { "name" : [type, fwd_position] }
     # forward_outputs_position_map = { "name" : [type, fwd_position] }
@@ -790,13 +810,20 @@ def GenerateForwardDefinition(fwd_api_name, bwd_api_name,
     inputs_call_args_str = ", ".join(inputs_call_list)
 
     # Forward Full Logic
-    forward_call_str = f"auto api_result = paddle::experimental::{fwd_api_name}({inputs_call_args_str});"
+    if len(intermediate_outputs) == 0:
+        function_name = fwd_api_name
+    else:
+        function_name = fwd_api_name + "_intermediate"
+    forward_call_str = f"auto api_result = paddle::experimental::{function_name}({inputs_call_args_str});"
 
     # Get return type list & outputs
-    num_outputs = len(forward_outputs_position_map.keys())
+    num_outputs = len(forward_outputs_position_map.keys()) - len(
+        intermediate_outputs)
     returns_type_list = ["" for i in range(num_outputs)]
     returns_list = ["" for i in range(num_outputs)]
     for name, (rtype, pos) in forward_outputs_position_map.items():
+        if name in intermediate_outputs:
+            continue
         if num_outputs == 1:
             returns_list[0] = f"api_result"
         else:
@@ -1037,6 +1064,12 @@ if __name__ == "__main__":
         print("Prased Forward Attrs List: ", forward_attrs_list)
         print("Parsed Forward Returns List: ", forward_returns_list)
 
+        intermediate_outputs = []
+        if 'intermediate' in fwd_api.keys():
+            intermediate_outputs = ParseIntermediate(fwd_api['intermediate'])
+
+        IntermediateValidationCheck(intermediate_outputs, forward_returns_list)
+
         # Collect Original Forward Inputs/Outputs and then perform validation checks
         orig_forward_inputs_list, orig_forward_attrs_list, orig_forward_returns_list = ParseYamlForward(
             fwd_args_str, fwd_returns_str)
@@ -1095,7 +1128,7 @@ if __name__ == "__main__":
             fwd_api_name, bwd_api_name, forward_inputs_position_map,
             forward_outputs_position_map, forward_attrs_list,
             backward_fwd_input_map, backward_grad_input_map,
-            backward_grad_output_map, backward_attrs_list)
+            backward_grad_output_map, backward_attrs_list, intermediate_outputs)
         print("Generated Forward Definition: ", forward_definition_str)
         print("Generated Forward Declaration: ", forward_declaration_str)
         forward_definition_str += definition_declaration_pair[0]