[Reland] search model buffers for dtype as the last resort (#23319)

search model buffers for dtype as the last resort

src/transformers/modeling_utils.py

@@ -207,22 +207,29 @@ def get_parameter_dtype(parameter: Union[nn.Module, GenerationMixin, "ModuleUtil
         # if no floating dtype was found return whatever the first dtype is
         return last_dtype
 
-    else:
-        # For nn.DataParallel compatibility in PyTorch > 1.5
-        def find_tensor_attributes(module: nn.Module) -> List[Tuple[str, Tensor]]:
-            tuples = [(k, v) for k, v in module.__dict__.items() if torch.is_tensor(v)]
-            return tuples
-
-        gen = parameter._named_members(get_members_fn=find_tensor_attributes)
-        last_tuple = None
-        for tuple in gen:
-            last_tuple = tuple
-            if tuple[1].is_floating_point():
-                return tuple[1].dtype
-
+    # For nn.DataParallel compatibility in PyTorch > 1.5
+    def find_tensor_attributes(module: nn.Module) -> List[Tuple[str, Tensor]]:
+        tuples = [(k, v) for k, v in module.__dict__.items() if torch.is_tensor(v)]
+        return tuples
+
+    gen = parameter._named_members(get_members_fn=find_tensor_attributes)
+    last_tuple = None
+    for tuple in gen:
+        last_tuple = tuple
+        if tuple[1].is_floating_point():
+            return tuple[1].dtype
+
+    if last_tuple is not None:
         # fallback to the last dtype
         return last_tuple[1].dtype
 
+    # fallback to buffer dtype
+    for t in parameter.buffers():
+        last_dtype = t.dtype
+        if t.is_floating_point():
+            return t.dtype
+    return last_dtype
+
 
 def get_state_dict_float_dtype(state_dict):
     """