Fix 'get_real_value' on placeholder nodes (#127698)

Summary:
X-link: pytorch/pytorch#127698
Approved by: https://github.com/jansel
ghstack dependencies: #127695, #127696

Reviewed By: clee2000

Differential Revision: D58443884

fbshipit-source-id: 739dc15e745abc83691ee3bae3e29d8fd3bfa44a

userbenchmark/dynamo/dynamobench/_dynamo/utils.py

@@ -1941,6 +1941,9 @@ def get_real_value(node, tracer):
         lambda n: get_real_value(n, tracer),
     )
 
+    if op == "placeholder" and "grapharg" in node.meta:
+        return node.meta["grapharg"].example
+
     if op == "call_module":
         nn_module = tracer.output_graph.nn_modules[node.target]
         if not is_lazy_module(nn_module):