diff --git a/mie/ir/op.c b/mie/ir/op.c
index 7a3b239..9b13117 100644
--- a/mie/ir/op.c
+++ b/mie/ir/op.c
@@ -80,12 +80,24 @@ struct mie_register *mie_op_add_result(struct mie_op *op, const struct mie_type
 	return result;
 }
 
+static bool is_isolated(const struct mie_op *op)
+{
+	const struct mie_trait *isolated = mie_trait_table_get_unique(
+		&op->op_info->op_traits, "builtin", "isolated-from-above");
+	return isolated != NULL;
+}
+
 struct mie_region *mie_op_add_region(struct mie_op *op)
 {
+	bool isolated = is_isolated(op);
+
 	struct mie_region *region = mie_vector_emplace_back(op->op_regions, NULL);
-	region->r_names = mie_name_map_create(NULL);
 	region->r_parent = op;
 
+	if (isolated) {
+		region->r_names = mie_name_map_create(NULL);
+	}
+
 	return region;
 }