Capture rewrite rule name as metadata (#2675)

Capture rewrite rule name as metadata to simplify debugging issues from
rewrites. This is just a basic version.

TODO / Extensions:
* Sometimes we apply a sequence of rewrite-rules one after another, to
perform complex fusions. This currently records only the last rule
applied.
* This can be solved when we merge metadata from original nodes into new
nodes. (See #2375 )
* May be useful standardize on a single ONNX metadata key for "source"
info (that can be used by torchlib/other exporters/rewriter/optimizer
etc.)

---------

Signed-off-by: Ganesan Ramalingam <grama@microsoft.com>

Author: gramalingam

onnxscript/rewriter/__init__.py

@@ -16,6 +16,7 @@
     "RewriterContext",
     "MatchingTracer",
     "MatchStatus",
+    "RULE_NAME_TAG",
 ]
 
 import onnx
@@ -25,6 +26,7 @@
 from onnxscript.rewriter import pattern
 from onnxscript.rewriter._basics import MatchContext, MatchingTracer, MatchResult, MatchStatus
 from onnxscript.rewriter._rewrite_rule import (
+    RULE_NAME_TAG,
     RewriterContext,
     RewriteRule,
     RewriteRuleClassBase,

onnxscript/rewriter/_rewrite_rule.py

@@ -25,6 +25,11 @@
 
 RewriterContext = _tape.Builder
 
+# TODO(rama): Standardize metadata property keys. May be worth standardizing at ONNX level for
+# source/producer metadata.
+
+RULE_NAME_TAG = "pkg.onnxscript.rewriter.rule_name"
+
 
 @dataclasses.dataclass
 class ReplacementSubgraph:
@@ -719,6 +724,13 @@ def _apply_to_graph_or_function(
                     _ir_utils.display_nodes(delta.new_nodes)
                     print("++++End Replacement Nodes++++")
 
+                # Capture rewrite rule name as metadata.
+                # TODO(rama): This is just a basic version. We may wish to compose "source" metadata
+                # from multiple rules in future.
+                if rule.name:
+                    for n in delta.new_nodes:
+                        n.metadata_props[RULE_NAME_TAG] = rule.name
+
                 convenience.replace_nodes_and_values(
                     graph_or_function,
                     node,

onnxscript/rewriter/pattern_test.py

@@ -10,6 +10,7 @@
 import onnx.parser
 
 import onnxscript.optimizer
+import onnxscript.rewriter
 from onnxscript import FLOAT, ir, script
 from onnxscript import opset17 as op
 from onnxscript.rewriter import pattern
@@ -936,6 +937,44 @@ def add_pattern(op, x, y):
         match_result = rule_pattern.match(model, model.graph, add_nodes[2])
         self.assertFalse(bool(match_result))
 
+    def test_rule_name_metadata(self):
+        """Test that RewriteRule carries name metadata."""
+
+        class ReciprocalMulRule(pattern.RewriteRuleClassBase):
+            def __init__(self, name: str | None = None):
+                super().__init__(name)
+
+            def pattern(self, op, x, y):
+                return (1 / x) * y
+
+            def rewrite(self, op, x, y):
+                return op.Div(y, x)
+
+        @script()
+        def test_script(x: FLOAT[1024], y: FLOAT[1024]) -> FLOAT[1024]:
+            return op.Mul(op.Div(op.Constant(value_float=1.0), x), y)
+
+        rule = ReciprocalMulRule.rule(name="ReciprocalMulToDiv")
+        model_proto = test_script.to_model_proto()
+        model = ir.serde.deserialize_model(model_proto)
+        count = rule.apply_to_model(model)
+        self.assertEqual(count, 1)
+        for node in model.graph:
+            if node.op_type == "Div":
+                tag = onnxscript.rewriter.RULE_NAME_TAG
+                self.assertEqual(node.metadata_props.get(tag), "ReciprocalMulToDiv")
+
+        # By default, the rule name is the class name (if not provided)
+        rule = ReciprocalMulRule.rule()
+        model_proto = test_script.to_model_proto()
+        model = ir.serde.deserialize_model(model_proto)
+        count = rule.apply_to_model(model)
+        self.assertEqual(count, 1)
+        for node in model.graph:
+            if node.op_type == "Div":
+                tag = onnxscript.rewriter.RULE_NAME_TAG
+                self.assertEqual(node.metadata_props.get(tag), "ReciprocalMulRule")
+
 
 class PatternBuilderTest(unittest.TestCase):
     def test_pattern_builder_context(self):