Refactor optimizer/evaluator.py and visitor.py to not use _legacy_ir

[titaiwangms]

Optimizer relies on graph analysis to fold constant.

onnxscript/onnxscript/optimizer/evaluator.py

Line 52 in 2824bc8

class IRContext(Protocol):

We should either extend the current IR to analyze graph, or develop/keep IRContext, but detach it with StaticValueInfo in _legacy_ir folder.

Lack of: StaticValueInfo.symbolic_value

onnxscript/onnxscript/_legacy_ir/__init__.py

Lines 61 to 66 in 2824bc8

	@dataclasses.dataclass
	class StaticValueInfo:
	name: str
	value: ConcreteValue = NotConstant
	type: onnx.TypeProto | None = None
	symbolic_value: SymbolicValue | None = None

The usages:

onnxscript/onnxscript/optimizer/constant_folding.py

Lines 152 to 171 in 2824bc8

	def process_function_outputs(self, function: onnx.FunctionProto) -> bool:
	# Resolve copy for function subgraph output.
	# Avoid copy of function subgraph input, because it is illegal for a direct edge
	# from function input to function output.
	prohibited_value_set = set(function.input)
	updated = False
	for i, output_name in enumerate(function.output):
	output = self.lookup(output_name)
	if (
	output is not None
	and output.is_copy()
	and output.symbolic_value not in prohibited_value_set
	):
	old_value = self.lookup_or_create(output.name)
	assert isinstance(output.symbolic_value, str)
	new_value = self.lookup_or_create(output.symbolic_value)
	new_value.identity_merge_from(old_value)
	function.output[i] = output.symbolic_value
	updated = True
	return updated

cc @gramalingam @justinchuby

[titaiwangms]

Related #1324

[justinchuby]

• [IR] Support symbolic values? #1438

[titaiwangms]

• [IR] Support symbolic values? #1438

Related

[justinchuby]

Do we want to create something similar to the interpreter in fx as a simplified visitor for general use?

[titaiwangms]

Do we want to create something similar to the interpreter in fx as a simplified visitor for general use?

We can discuss offline if you have an idea.

For this issue, do you think IRContext is something that we can merge into IR after having symbolic_value? Looks like visitor.py also needs a huge refactor..