[ `T5`] fix fp16 loading issue (#20878)

* fix fp16 loading issue

* add backward compatibility

* better refactor

* better readability

- remove `force_upcast_dtype` as it is used once
- use `inspect`
- add `TODO`

src/transformers/modeling_utils.py

@@ -609,6 +609,7 @@ def _load_state_dict_into_meta_model(
             param_name = param_name[len(start_prefix) :]
 
         module_name = param_name
+        set_module_kwargs = {}
 
         # We convert floating dtypes to the `dtype` passed. We want to keep the buffers/params
         # in int/uint/bool and not cast them.
@@ -619,6 +620,11 @@ def _load_state_dict_into_meta_model(
                 and dtype == torch.float16
             ):
                 param = param.to(torch.float32)
+
+                # For backward compatibility with older versions of `accelerate`
+                # TODO: @sgugger replace this check with version check at the next `accelerate` release
+                if "dtype" in list(inspect.signature(set_module_tensor_to_device).parameters):
+                    set_module_kwargs["dtype"] = torch.float32
             else:
                 param = param.to(dtype)
 
@@ -634,6 +640,8 @@ def _load_state_dict_into_meta_model(
             if old_param is not None:
                 param = param.to(old_param.dtype)
 
+        set_module_kwargs["value"] = param
+
         if device_map is None:
             param_device = "cpu"
         else:
@@ -651,7 +659,8 @@ def _load_state_dict_into_meta_model(
         elif param_device == "cpu" and state_dict_index is not None:
             state_dict_index = offload_weight(param, param_name, state_dict_folder, state_dict_index)
         elif not load_in_8bit:
-            set_module_tensor_to_device(model, param_name, param_device, value=param)
+            # For backward compatibility with older versions of `accelerate`
+            set_module_tensor_to_device(model, param_name, param_device, **set_module_kwargs)
         else:
             set_module_8bit_tensor_to_device(model, param_name, param_device, value=param)