Fix float8_e4m3fn in modeling_utils (#32193)

* Fix float8_e4m3fn in modeling_utils

* style

* fix

* comment

src/transformers/modeling_utils.py

@@ -855,6 +855,8 @@ def _load_state_dict_into_meta_model(
     for old_key, new_key in zip(old_keys, new_keys):
         state_dict[new_key] = state_dict.pop(old_key)
 
+    is_torch_e4m3fn_available = hasattr(torch, "float8_e4m3fn")
+
     for param_name, param in state_dict.items():
         # First part of the test is always true as load_state_dict_keys always contains state_dict keys.
         if param_name not in loaded_state_dict_keys or param_name not in expected_keys:
@@ -866,9 +868,10 @@ def _load_state_dict_into_meta_model(
         module_name = param_name
         set_module_kwargs = {}
 
-        # We convert floating dtypes to the `dtype` passed. We want to keep the buffers/params
+        # We convert floating dtypes to the `dtype` passed except for float8_e4m3fn type. We also want to keep the buffers/params
         # in int/uint/bool and not cast them.
-        if dtype is not None and torch.is_floating_point(param) and param.dtype != torch.float8_e4m3fn:
+        is_param_float8_e4m3fn = is_torch_e4m3fn_available and param.dtype == torch.float8_e4m3fn
+        if dtype is not None and torch.is_floating_point(param) and not is_param_float8_e4m3fn:
             if (
                 keep_in_fp32_modules is not None
                 and any(