let backends set info on the lowered_backend.meta from preprocess

exir/backend/backend_api.py

@@ -126,6 +126,10 @@ def to_backend(
             lowered_module.meta = {
                 "debug_handle_map": preprocess_result.debug_handle_map
             }
+            if preprocess_result._delegate_info_meta is not None:
+                lowered_module.meta["_delegate_info_meta"] = (
+                    preprocess_result._delegate_info_meta
+                )
             return lowered_module
     raise NotImplementedError(f"Backend {backend_id} was not found.")
 
@@ -610,6 +614,11 @@ def lower_all_submodules_to_backend(
             lowered_module.meta = {
                 "debug_handle_map": preprocess_result.debug_handle_map,
             }
+            if preprocess_result._delegate_info_meta is not None:
+                assert lowered_module.meta is not None
+                lowered_module.meta["_delegate_info_meta"] = (
+                    preprocess_result._delegate_info_meta
+                )
             is_submodule = call_submodule_node.meta["is_submodule"]
             toplevel_input_specs_to_delete = call_submodule_node.meta[
                 "toplevel_input_specs_to_delete"

exir/backend/backend_details.py

@@ -7,7 +7,7 @@
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
 
-from typing import Dict, List, Optional, Tuple, Union
+from typing import Any, Dict, List, Optional, Tuple, Union
 
 from executorch.exir._serialize._named_data_store import NamedDataStoreOutput
 
@@ -32,6 +32,11 @@ class PreprocessResult:
     # but retrieveable by delegates via the NamedDataMap at runtime.
     data_store_output: Optional[NamedDataStoreOutput] = None
 
+    # Optional delegate-specific information that will be added to the
+    # lowered_module.meta field in the graph, but not directly serialized
+    # into the PTE file.
+    _delegate_info_meta: Optional[Any] = None
+
 
 """
 How to create a backend (for example, BackendWithCompilerDemo):

exir/backend/test/backend_with_compiler_demo.py

@@ -138,4 +138,5 @@ def preprocess(
                 encoding="utf8",
             ),
             debug_handle_map=debug_handle_map,
+            _delegate_info_meta="test",
         )

exir/backend/test/test_backends_lifted.py

@@ -1264,3 +1264,63 @@ def forward(self, x: List[torch.Tensor]):
 
         gm = to_edge(export(ComposedM(), inputs, strict=True))
         gm.exported_program().module()(*inputs)
+
+    def test_delegate_info_full_delegate(self):
+        """
+        Test that _delegate_info_meta from BackendWithCompilerDemo ends up in the call_delegate node metadata
+        when using full delegation (to_backend directly).
+        """
+
+        class SinModule(torch.nn.Module):
+            def __init__(self):
+                super().__init__()
+
+            def forward(self, x):
+                return torch.sin(x)
+
+        sin_module = SinModule()
+        model_inputs = (torch.ones(1),)
+        edgeir_m = to_edge(export(sin_module, model_inputs, strict=True))
+        max_value = model_inputs[0].shape[0]
+        compile_specs = [CompileSpec("max_value", bytes([max_value]))]
+        lowered_sin_module = to_backend(
+            "BackendWithCompilerDemo", edgeir_m.exported_program(), compile_specs
+        )
+
+        # Check that the lowered module has _delegate_info_meta in its meta
+        self.assertIn("_delegate_info_meta", lowered_sin_module.meta.keys())
+        self.assertEqual(lowered_sin_module.meta["_delegate_info_meta"], "test")
+
+    def test_delegate_info_partitioner(self):
+        """
+        Test that _delegate_info_meta from BackendWithCompilerDemo ends up in the call_delegate node metadata
+        when using partitioner-based delegation.
+        """
+
+        class SinModule(torch.nn.Module):
+            def __init__(self):
+                super().__init__()
+
+            def forward(self, x):
+                return torch.sin(x)
+
+        sin_module = SinModule()
+        model_inputs = (torch.ones(1),)
+        max_value = model_inputs[0].shape[0]
+
+        partitioner = AllNodePartitioner(
+            "BackendWithCompilerDemo", [CompileSpec("max_value", bytes([max_value]))]
+        )
+
+        edgeir_m = to_edge(export(sin_module, model_inputs, strict=True))
+        lowered_m = edgeir_m.to_backend(partitioner)
+
+        # Check that the lowered submodule has _delegate_info_meta in its meta
+        lowered_submodules = get_lowered_submodules(
+            lowered_m.exported_program().graph_module
+        )
+        self.assertEqual(len(lowered_submodules), 1)
+
+        lowered_module = lowered_submodules[0][1]
+        self.assertIn("_delegate_info_meta", lowered_module.meta)
+        self.assertEqual(lowered_module.meta["_delegate_info_meta"], "test")

exir/emit/_emitter.py

@@ -1030,7 +1030,7 @@ def _add_delegate_map(
         code, module hierarchy etc.
         """
         delegate_map = {}
-        if hasattr(lowered_module, "meta"):
+        if lowered_module.meta is not None:
             delegate_map = lowered_module.meta.get("debug_handle_map", {})
 
         self.instr_id_to_delegate_debug_id_map[delegate_instruction_id] = {

exir/lowered_backend_module.py

@@ -66,6 +66,7 @@ class LoweredBackendModule(torch.nn.Module):
     _named_data_store_output: Optional[
         NamedDataStoreOutput
     ]  # Named Data serialized by the backend
+    meta: Optional[Dict[str, Any]]  # Metadata for the lowered module
 
     def __init__(
         self,
@@ -81,6 +82,7 @@ def __init__(
         self._processed_bytes = processed_bytes
         self._compile_specs = compile_specs
         self._named_data_store_output = named_data_store_output
+        self.meta = None
 
     # pyre-ignore
     def __deepcopy__(self, memo: Optional[Dict[int, Any]]) -> "LoweredBackendModule":
@@ -109,7 +111,6 @@ def __deepcopy__(self, memo: Optional[Dict[int, Any]]) -> "LoweredBackendModule"
             compile_specs=copy.deepcopy(self._compile_specs, memo),
             named_data_store_output=self._named_data_store_output,
         )
-        # pyre-fixme[16]: `LoweredBackendModule` has no attribute `meta`.
         res.meta = copy.copy(getattr(self, "meta", {}))
         return res