equip the first partition with same example input as original graph (pytorch#14454)

Summary:

This diff equips the partitioned submodules example inputs.

More specific, if the submodule starts from and covers all original export program's input, its example inputs should be the same as original export program's. Otherwise, the example inputs should be None.

The example inputs is essential for aoti-driven backends for further compile.

Reviewed By: larryliu0820

Differential Revision: D82865677

Author: Gasoonjia

exir/backend/backend_api.py

@@ -720,6 +720,8 @@ def to_backend(
             fake_edge_program = copy.deepcopy(edge_program)
         partitioner_result = partitioner_instance(fake_edge_program)
         tagged_exported_program = partitioner_result.tagged_exported_program
+        tagged_exported_program.example_inputs = edge_program.example_inputs
+
         method_to_tagged_exported_program[method_name] = tagged_exported_program
 
         # Check that the partitioner did not modify the original graph

exir/backend/test/TARGETS

@@ -458,3 +458,21 @@ python_unittest(
         "//executorch/exir/backend/canonical_partitioners:group_partitioner_lib",
     ],
 )
+
+python_unittest(
+    name = "test_example_input_of_submodule",
+    srcs = [
+        "test_submodule_example_inputs.py",
+    ],
+    deps = [
+        "//caffe2:torch",
+        "//executorch/exir:lib",
+        "//executorch/exir:lowered_backend_module",
+        "//executorch/exir/backend:backend_details",
+        "//executorch/exir/backend:compile_spec_schema",
+        "//executorch/exir/backend:partitioner",
+        "//executorch/exir/backend/test/demos/rpc:executor_backend_preprocess",
+        "//executorch/exir/backend:utils",
+        "//executorch/exir/dialects:lib",
+    ],
+)