fix constant tagging util function (#2816)

Summary:


Fix the constant nodes tagging util function
```
python3 -m examples.models.llama2.export_llama --coreml --use_kv_cache
```

Reviewed By: mcr229

Differential Revision: D55663281

Author: cccclai

exir/backend/utils.py

@@ -509,7 +509,7 @@ def tag_constant_data(edge_program: ExportedProgram) -> None:
     underlying data will be owned by multiple delegates.
     """
     for node in edge_program.graph.nodes:
-        # go through const/param/buffer nodes
+        # go through const/param/buffer nodes, if all users of const/param/buffer nodes are partitioned then partition
         is_attr = (
             node.op == "placeholder"
             and (
@@ -518,17 +518,20 @@ def tag_constant_data(edge_program: ExportedProgram) -> None:
                 or is_lifted_tensor_constant(edge_program, node)
             )
         ) or (node.op == "get_attr")
-        # if all users of const/param/buffer nodes are partitioned then partition
         if is_attr:
             user_tags = set()
             for user in node.users:
-                user_tags.add(user.meta.get("delegation_tag", None))
-            assert len(user_tags) <= 1, (
-                "Const/Param/Buffer users have multiple tags because one constant data can't "
-                "be owned by multiple backends. Consider duplicating the constant data so that "
-                "each user is unique"
-            )
-            if len(user_tags) == 1:
+                user_tag = user.meta.get("delegation_tag", None)
+                if user_tag is not None:
+                    user_tags.add(user_tag)
+            if len(user_tags) > 1:
+                logging.info(
+                    f"The data node is used across multiple partitions, including {user_tags}. "
+                    "If the data is too large and it's not prefered to copied, please tag the "
+                    "constant node like node.['no_copy'] = True and they won't be copied."
+                )
+            # tag the data node with the same tag as the last user
+            if len(user_tags) > 0:
                 node.meta["delegation_tag"] = user_tags.pop()