Use same constant in runtime for unset debug handle

In the runtime we have a contant number for unset debug handle. This diff bring that to python env for usage.

Differential Revision: [D78132322](https://our.internmc.facebook.com/intern/diff/D78132322/)

[ghstack-poisoned]

Author: Gasoonjia

devtools/inspector/_inspector_utils.py

@@ -37,6 +37,7 @@
 
 from executorch.exir.debug_handle_utils import (
     DEBUG_HANDLE_KEY,
+    UNSET_DEBUG_HANDLE,
     get_greatest_ancestor_node_identifier,
 )
 
@@ -914,7 +915,7 @@ def propagate_back_debug_handle(
     where op1_0 is from op1, op3_0 and op3_1 are from op3, op2 is removed by to_edge pipeline (e.g. RemoveNoopPass).
 
     Then debug handle of op1 should be same as op1_0, and debug handle of op3 should be same as op3_0 and op3_1.
-    The debug handle of op2 will be a non-existing debug handle in edge dialect program for further skipping.
+    The debug handle of op2 will be UNSET_DEBUG_HANDLE for further skipping.
 
     Return: True if:
         a. every debug handle in the edge dialect program has a corresponding node in the exported program
@@ -935,11 +936,6 @@ def propagate_back_debug_handle(
     # number of nodes in the exported program that have matched entry in export_graph_node_id_to_debug_handle
     n_matched_node = 0
 
-    # debug handle for the node in the exported program but not in the edge dialect program
-    debug_handle_for_removed_node = (
-        max(export_graph_node_id_to_debug_handle.values()) + 1
-    )
-
     def _find_n_match_node(node: torch.fx.Node) -> None:
         nonlocal n_matched_node
         if node.name in ("output", "placeholder"):
@@ -955,7 +951,7 @@ def _equip_debug_handle(node: torch.fx.Node) -> None:
         if node_id in export_graph_node_id_to_debug_handle:
             node.meta[DEBUG_HANDLE_KEY] = export_graph_node_id_to_debug_handle[node_id]
         else:
-            node.meta[DEBUG_HANDLE_KEY] = debug_handle_for_removed_node
+            node.meta[DEBUG_HANDLE_KEY] = UNSET_DEBUG_HANDLE
 
     bfs_trace_with_node_process(exported_program.graph_module, _find_n_match_node)
 

devtools/inspector/tests/inspector_utils_test.py

@@ -47,7 +47,7 @@
 )
 from executorch.devtools.inspector.numerical_comparator import L1Comparator
 from executorch.exir import to_edge
-from executorch.exir.debug_handle_utils import DEBUG_HANDLE_KEY
+from executorch.exir.debug_handle_utils import DEBUG_HANDLE_KEY, UNSET_DEBUG_HANDLE
 from torch.export import export
 
 
@@ -682,19 +682,20 @@ def forward(self, x: torch.Tensor) -> torch.Tensor:
             )
         )
 
-        # only two add ops in the exported program will keep in edge dialect program, so the debug handles for removed op will be three
-        debug_handle_for_removed_node = 3
+        n_removed_nodes = 0
 
         for node in exported_program.graph.nodes:
             if node.name == "add":
                 self.assertEqual(node.meta[DEBUG_HANDLE_KEY], 1)
             elif node.name == "add_1":
                 self.assertEqual(node.meta[DEBUG_HANDLE_KEY], 2)
             elif node.op not in ("placeholder", "output"):
+                n_removed_nodes += 1
                 self.assertEqual(
-                    node.meta[DEBUG_HANDLE_KEY], debug_handle_for_removed_node
+                    node.meta[DEBUG_HANDLE_KEY], UNSET_DEBUG_HANDLE
                 )
 
+        self.assertEqual(n_removed_nodes, 2)
 
 def gen_mock_operator_graph_with_expected_map() -> (
     Tuple[OperatorGraph, Dict[int, OperatorNode]]

exir/debug_handle_utils.py

@@ -9,6 +9,7 @@
 FROM_NODE_KEY = "from_node"
 DEBUG_HANDLE_KEY = "debug_handle"
 
+UNSET_DEBUG_HANDLE = 0
 
 def get_greatest_ancestor_node_identifier(node: Node) -> str:
     """Get the identifier of the greatest ancestor node of the given node.