[pass] Update DCE passes (#2257)

- Remove the `remove_initialized_inputs` option in dce because the
contract of the pass it that it does not modify model signature. Fixed
bugs where initializers are removed. Instead, users can use
#2253 to remove the
initialized inputs first.
- Additionally updated RemoveUnusedOpsetsPass to always retain the
default opset.

---------

Co-authored-by: Copilot <[email protected]>

Author: justinchuby

onnxscript/ir/passes/common/unused_removal.py

@@ -93,29 +93,20 @@ def _remove_unused_nodes_in_graph_like(function_or_graph: ir.Function | ir.Graph
 
 
 class RemoveUnusedNodesPass(ir.passes.InPlacePass):
-    """Pass for removing unused nodes and initializers.
+    """Pass for removing unused nodes and initializers (dead code elimination).
 
-    Attributes:
-        remove_initialized_inputs: When an unused initializer is simultaneously a graph input,
-            remove that input as well. Note that this will change the model input signature.
+    This pass does not modify the model signature (inputs and outputs). It ensures
+    that unused nodes and initializers are removed while preserving the original
+    contract of the model.
     """
 
-    def __init__(self, remove_initialized_inputs: bool = False):
-        super().__init__()
-        self.remove_initialized_inputs = remove_initialized_inputs
-
     def call(self, model: ir.Model) -> ir.passes.PassResult:
         count = _remove_unused_nodes_in_graph_like(model.graph)
         graph_outputs = frozenset(model.graph.outputs)
+        graph_inputs = frozenset(model.graph.inputs)
         initializers = model.graph.initializers
-        if self.remove_initialized_inputs:
-            graph_inputs = model.graph.inputs
-            for i, inp in reversed(list(enumerate(graph_inputs))):
-                if inp.name in initializers and not (inp in graph_outputs or inp.uses()):
-                    del graph_inputs[i]
-                    count += 1
         for init in list(initializers.values()):
-            if not (init in graph_outputs or init.uses()):
+            if not (init.uses() or init in graph_outputs or init in graph_inputs):
                 assert init.name is not None
                 del initializers[init.name]
                 count += 1
@@ -193,13 +184,13 @@ def _process_graph_like(
 
     def call(self, model: ir.Model) -> ir.passes.PassResult:
         # Record domains of all functions
-        used_domains = set()
+        used_domains = {""}  # By default always retain the onnx (default) domain
         for function in model.functions.values():
             used_domains.add(function.domain)
         modified = self._process_graph_like(model.graph, used_domains=used_domains)
 
         if self.process_functions:
             for function in model.functions.values():
-                modified |= self._process_graph_like(function, used_domains=set())
+                modified |= self._process_graph_like(function, used_domains={""})
 
         return ir.passes.PassResult(model, modified=modified)

onnxscript/ir/passes/common/unused_removal_test.py

@@ -13,15 +13,13 @@
 class RemoveUnusedTest(unittest.TestCase):
     using_ir: bool
 
-    def remove_unused_nodes(
-        self, model: onnx.ModelProto, remove_initialized_inputs: bool = False
-    ):
+    def remove_unused_nodes(self, model: onnx.ModelProto):
         if self.using_ir:
             model_ir = ir.serde.deserialize_model(model)
-            onnxscript.optimizer.remove_unused_nodes(model_ir, remove_initialized_inputs)
+            onnxscript.optimizer.remove_unused_nodes(model_ir)
             model = ir.serde.serialize_model(model_ir)
             return model
-        onnxscript.optimizer.remove_unused_nodes(model, remove_initialized_inputs)
+        onnxscript.optimizer.remove_unused_nodes(model)
         return model
 
     def test_remove_unused_nodes(self):
@@ -56,24 +54,7 @@ def test_remove_unused_initializers(self):
         self.assertEqual(model.graph.node[0].op_type, "Mul")
         self.assertEqual(len(model.graph.initializer), 0)
 
-    def test_unused_initialized_inputs_are_removed_when_requested(self):
-        # https://github.com/microsoft/onnxscript/issues/2211
-        model = onnx.parser.parse_model(
-            """
-            <ir_version: 10, opset_import: [ "" : 17]>
-            agraph (float[N] x, float[N] two) => (float[N] z)
-            <float two = {2.0,2.0}> {
-                four = Add(two, two)
-                z = Mul(x, x)
-            }
-        """
-        )
-        model = self.remove_unused_nodes(model, remove_initialized_inputs=True)
-        self.assertEqual(len(model.graph.node), 1)
-        self.assertEqual(model.graph.node[0].op_type, "Mul")
-        self.assertEqual(len(model.graph.input), 1)
-
-    def test_unused_initialized_inputs_are_kept_by_default(self):
+    def test_unused_initialized_inputs_are_kept(self):
         model = onnx.parser.parse_model(
             """
             <ir_version: 10, opset_import: [ "" : 17]>
@@ -88,9 +69,9 @@ def test_unused_initialized_inputs_are_kept_by_default(self):
         self.assertEqual(len(model.graph.node), 1)
         self.assertEqual(model.graph.node[0].op_type, "Mul")
         self.assertEqual(len(model.graph.input), 2)
+        self.assertEqual(len(model.graph.initializer), 1)
 
-    @parameterized.parameterized.expand([True, False])
-    def test_unused_inputs_are_not_removed(self, remove_initialized_inputs: bool):
+    def test_unused_inputs_are_not_removed(self):
         # preserve inputs as part of interface
         model = onnx.parser.parse_model(
             """
@@ -102,9 +83,7 @@ def test_unused_inputs_are_not_removed(self, remove_initialized_inputs: bool):
             }
         """
         )
-        model = self.remove_unused_nodes(
-            model, remove_initialized_inputs=remove_initialized_inputs
-        )
+        model = self.remove_unused_nodes(model)
         self.assertEqual(len(model.graph.node), 1)
         self.assertEqual(model.graph.node[0].op_type, "Mul")
         self.assertEqual(len(model.graph.input), 2)

onnxscript/optimizer/__init__.py

@@ -112,19 +112,15 @@ def fold_constants(
         return result
 
 
-def remove_unused_nodes(
-    model: ir.Model | onnx.ModelProto, remove_initialized_inputs: bool = False
-) -> None:
+def remove_unused_nodes(model: ir.Model | onnx.ModelProto) -> None:
     """Removes unused nodes from a model inplace."""
     if isinstance(model, ir.Model):
-        onnxscript.ir.passes.common.unused_removal.RemoveUnusedNodesPass(
-            remove_initialized_inputs=remove_initialized_inputs
-        )(model)
+        onnxscript.ir.passes.common.unused_removal.RemoveUnusedNodesPass()(model)
     else:
         model_ir = ir.serde.deserialize_model(model)
-        model_ir = onnxscript.ir.passes.common.unused_removal.RemoveUnusedNodesPass(
-            remove_initialized_inputs=remove_initialized_inputs
-        )(model_ir).model
+        model_ir = onnxscript.ir.passes.common.unused_removal.RemoveUnusedNodesPass()(
+            model_ir
+        ).model
         new_proto = ir.serde.serialize_model(model_ir)
         model.Clear()
         model.CopyFrom(new_proto)