Support NoNeedBuffer for final state codegen (#39628)

* Support NoNeedBuffer for final state codegen

* Replaced pten with phi

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

@@ -127,6 +127,15 @@ def ReadBwdFile(filepath):
 ######################
 ###  Yaml Parsers  ###
 ######################
+def ParseNoNeedBuffer(string):
+    # string: "x, y"
+    no_need_buffer_set = set()
+    for name in string.split(","):
+        no_need_buffer_set.add(name.strip())
+
+    return no_need_buffer_set
+
+
 def ParseYamlArgs(string):
     # Example: const Tensor& x, const Tensor& y, bool transpose_x, bool transpose_y
 
@@ -397,7 +406,7 @@ def SlotNameMatching(backward_inputs_list, backward_returns_list,
 
 
 def GenerateNodeDeclaration(fwd_api_name, backward_fwd_input_map,
-                            backward_attrs_list):
+                            backward_attrs_list, no_need_buffer_set):
     # Inputs:
     # fwd_api_name = ""
     # backward_fwd_input_map   = { "name" : [type, is_fwd_input, orig_position] ...}
@@ -410,15 +419,20 @@ def GenerateNodeDeclaration(fwd_api_name, backward_fwd_input_map,
     set_tensor_wrapper_methods_str = ""
     tensor_wrapper_members_str = ""
     for tname, (ttype, is_fwd_input, _) in backward_fwd_input_map.items():
+        if tname in no_need_buffer_set:
+            no_need_buffer = "true"
+        else:
+            no_need_buffer = "false"
+
         tensor_wrapper_name = GetSavedName(tname)
         if IsPlainTensorType(ttype):
             SET_PLAIN_TENSOR_WRAPPER_TEMPLATE = """
    void SetTensorWrapper{}(const paddle::experimental::Tensor& {}, bool full_reserved) {{     
-     {} = egr::TensorWrapper({}, full_reserved);
+     {} = egr::TensorWrapper({}, full_reserved, {});
    }}
 """
             set_tensor_wrapper_methods_str += SET_PLAIN_TENSOR_WRAPPER_TEMPLATE.format(
-                tname, tname, tensor_wrapper_name, tname)
+                tname, tname, tensor_wrapper_name, tname, no_need_buffer)
 
             PLAIN_TENSOR_MEMBER_TEMPLATE = """
    egr::TensorWrapper {};
@@ -430,12 +444,12 @@ def GenerateNodeDeclaration(fwd_api_name, backward_fwd_input_map,
             SET_VECTOR_TENSOR_WRAPPER_TEMPLATE = """
    void SetTensorWrapper{}(const std::vector<paddle::experimental::Tensor>& {}, bool full_reserved) {{
      for(const auto& eager_tensor : {}) {{
-        {}.emplace_back( egr::TensorWrapper(eager_tensor, full_reserved) );
+        {}.emplace_back( egr::TensorWrapper(eager_tensor, full_reserved, {}) );
      }};
    }}
 """
             set_tensor_wrapper_methods_str += SET_VECTOR_TENSOR_WRAPPER_TEMPLATE.format(
-                tname, tname, tname, tensor_wrapper_name)
+                tname, tname, tname, tensor_wrapper_name, no_need_buffer)
 
             VECTOR_TENSOR_MEMBER_TEMPLATE = """
    std::vector<egr::TensorWrapper> {};
@@ -997,6 +1011,10 @@ if __name__ == "__main__":
         assert 'output' in fwd_api.keys()
         assert 'backward' in fwd_api.keys()
 
+        no_need_buffer_set = set()
+        if 'no_need_buffer' in fwd_api.keys():
+            no_need_buffer_set = ParseNoNeedBuffer(fwd_api['no_need_buffer'])
+
         fwd_api_name = fwd_api['api']
         fwd_args_str = fwd_api['args']
         fwd_returns_str = fwd_api['output']
@@ -1062,7 +1080,8 @@ if __name__ == "__main__":
 
         # Node Declaration Generation
         node_declaration_str += GenerateNodeDeclaration(
-            fwd_api_name, backward_fwd_input_map, backward_attrs_list)
+            fwd_api_name, backward_fwd_input_map, backward_attrs_list,
+            no_need_buffer_set)
         print("Generated Node Declaration: ", node_declaration_str)
 
         node_definition_str += GenerateNodeDefinition(

paddle/fluid/eager/tensor_wrapper.h

@@ -34,7 +34,8 @@ class TensorWrapper {
  public:
   TensorWrapper() = default;
   explicit TensorWrapper(const paddle::experimental::Tensor& tensor,
-                         bool full_reserved = false) {
+                         bool full_reserved = false,
+                         bool no_need_buffer = false) {
     /**
      * Normally, we should fully reserved all non-output or non-leaf fwd tensor
      * here. And for fwd output tensor, we should not reserve its autogradmeta,
@@ -48,7 +49,22 @@ class TensorWrapper {
     }
 
     // shallow copy tensor_impl here
+    if (no_need_buffer) {
+      if (phi::DenseTensor::classof(tensor.impl().get())) {
+        // Only Copy Meta
+        phi::DenseTensor* dense_tensor =
+            static_cast<phi::DenseTensor*>(tensor.impl().get());
+        auto tw_dense_tensor = std::make_shared<phi::DenseTensor>();
+        tw_dense_tensor->set_meta(dense_tensor->meta());
+        intermidiate_tensor_.set_impl(tw_dense_tensor);
+      } else {
+        PADDLE_THROW(paddle::platform::errors::Fatal(
+            "Unrecognized tensor type for no_need_buffer feature"));
+      }
+    } else {
       intermidiate_tensor_.set_impl(tensor.impl());
+    }
+
     intermidiate_tensor_.set_name(tensor.name() + "@Saved");
     PADDLE_ENFORCE_NOT_NULL(
         EagerUtils::unsafe_autograd_meta(tensor),