Use unlifted export pass to tag delegated constants

docs/source/using-executorch-export.md

@@ -129,14 +129,16 @@ To generate a `model.pte`, `model.ptd` pair with the weights inside `model.ptd`,
 
 ```python
 from executorch.exir.passes.external_constants_pass import (
-    delegate_external_constants_pass,
+    delegate_external_constants_pass_unlifted,
 )
-partial_function = partial(
-    delegate_external_constants_pass,
-    ep=exported_program,
+# Tag the unlifted ep.module().
+tagged_module = exported_program.module()
+delegate_external_constants_pass_unlifted(
+    module=tagged_module,
     gen_tag_fn=lambda x: "model", # This is the filename the weights will be saved to. In this case, weights will be saved as "model.ptd"
 )
-
+# Re-export to get the EP.
+exported_program = export(tagged_module, inputs, dynamic_shapes=dynamic_shapes)
 executorch_program = to_edge_transform_and_lower(
     exported_program,
     transform_passes = [partial_function],

examples/models/llama/export_llama_lib.py

@@ -1079,7 +1079,7 @@ def _export_llama(llm_config: LlmConfig) -> LLMEdgeManager:  # noqa: C901
 
     if llm_config.backend.xnnpack.enabled:
         if llm_config.export.foundation_weights_file is not None:
-            gen_tag_fn: Callable[[torch.fx.Node], str] = lambda x: (
+            gen_tag_fn: Callable[[torch.fx.Node], Optional[str]] = lambda x: (
                 llm_config.export.foundation_weights_file
                 if "lora" not in x.name
                 else None
@@ -1089,8 +1089,11 @@ def _export_llama(llm_config: LlmConfig) -> LLMEdgeManager:  # noqa: C901
                 delegate_external_constants_pass_unlifted,
             )
 
+            assert (
+                builder_exported.pre_autograd_graph_module is not None
+            ), "pre_autograd_graph_module shouldn't be None here"
             delegate_external_constants_pass_unlifted(
-                gm=builder_exported.pre_autograd_graph_module,
+                module=builder_exported.pre_autograd_graph_module,
                 gen_tag_fn=gen_tag_fn,
             )
 

exir/passes/external_constants_pass.py

@@ -88,53 +88,22 @@ def external_mutable_weights_pass(
     return PassResult(gm, mutated)
 
 
-def delegate_external_constants_pass(
-    gm: GraphModule,
-    ep: ExportedProgram,
-    gen_tag_fn: Optional[Callable[[torch.fx.Node], str]] = None,
-) -> PassResult:
-    """
-    Tag external constants before to_backend.
-
-    Note: this pass must be run after run_decompositions(), as tags on
-    constants are removed then.
-
-    Args:
-        gm: GraphModule to tag.
-        ep: ExportedProgram, to distinguish if a node is a constant.
-        gen_tag_fn: node -> str callable indicating the tag for the node.
-    Returns:
-        PassResult: The resulting gm, and if it was mutated or not.
-    """
-    mutated = False
-    for module in gm.modules():
-        if not isinstance(module, torch.fx.GraphModule):
-            continue
-        for node in module.graph.nodes:
-            if node.op == "placeholder" and is_param_node(ep, node):
-                if gen_tag_fn is not None:
-                    node.meta.setdefault("custom", {})
-                    node.meta["custom"]["delegate_constant_tag"] = gen_tag_fn(node)
-                    mutated = True
-    return PassResult(gm, mutated)
-
-
 # Note: this pass must be run on an unlifted graph, e.g. ep.module(),
 # and not on a lifted graph, e.g. ep.graph_module.
 # This is using 'get_attr' to tag constants, which only appears in
 # unlifted graphs.
 def delegate_external_constants_pass_unlifted(
-    gm: GraphModule,
-    gen_tag_fn: Optional[Callable[[torch.fx.Node], str]] = None,
+    module: torch.nn.Module,
+    gen_tag_fn: Optional[Callable[[torch.fx.Node], Optional[str]]] = None,
 ) -> PassResult:
     mutated = False
-    for module in gm.modules():
-        if not isinstance(module, torch.fx.GraphModule):
+    for m in module.modules():
+        if not isinstance(m, torch.fx.GraphModule):
             continue
-        for node in module.graph.nodes:
+        for node in m.graph.nodes:
             if node.op == "get_attr":
                 if gen_tag_fn is not None:
                     node.meta.setdefault("custom", {})
                     node.meta["custom"]["delegate_constant_tag"] = gen_tag_fn(node)
                     mutated = True
-    return PassResult(gm, mutated)
+    return PassResult(module, mutated)

test/models/export_delegated_program.py

@@ -11,7 +11,6 @@
 import os
 import sys
 
-from functools import partial
 from typing import Dict, final, Optional, Sequence, Type
 
 import executorch.exir as exir
@@ -28,7 +27,7 @@
     ExecutorBackend,
 )
 from executorch.exir.passes.external_constants_pass import (
-    delegate_external_constants_pass,
+    delegate_external_constants_pass_unlifted,
 )
 from executorch.exir.program import ExecutorchProgramManager
 from torch import nn
@@ -173,17 +172,15 @@ def forward(self, *args, **kwargs):
             XnnpackPartitioner,
         )
 
-        transform_passes = []
         if external_constants:
-            partial_function = partial(
-                delegate_external_constants_pass,
-                ep=exported_program,
+            tagged_module = exported_program.module()
+            delegate_external_constants_pass_unlifted(
+                module=tagged_module,
                 gen_tag_fn=lambda x: module_class.__name__,
             )
-            transform_passes.append(partial_function)
+            exported_program = export(tagged_module, args=inputs, strict=True)
         executorch_program = to_edge_transform_and_lower(
             exported_program,
-            transform_passes=transform_passes,
             compile_config=edge_config,
             partitioner=[XnnpackPartitioner()],
         ).to_executorch(config=et_config)