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| """The optimizer tries to constant fold expressions and modify the AST | |
| in place so that it should be faster to evaluate. | |
| Because the AST does not contain all the scoping information and the | |
| compiler has to find that out, we cannot do all the optimizations we | |
| want. For example, loop unrolling doesn't work because unrolled loops | |
| would have a different scope. The solution would be a second syntax tree | |
| that stored the scoping rules. | |
| """ | |
| import typing as t | |
| from . import nodes | |
| from .visitor import NodeTransformer | |
| if t.TYPE_CHECKING: | |
| from .environment import Environment | |
| def optimize(node: nodes.Node, environment: "Environment") -> nodes.Node: | |
| """The context hint can be used to perform an static optimization | |
| based on the context given.""" | |
| optimizer = Optimizer(environment) | |
| return t.cast(nodes.Node, optimizer.visit(node)) | |
| class Optimizer(NodeTransformer): | |
| def __init__(self, environment: "t.Optional[Environment]") -> None: | |
| self.environment = environment | |
| def generic_visit( | |
| self, node: nodes.Node, *args: t.Any, **kwargs: t.Any | |
| ) -> nodes.Node: | |
| node = super().generic_visit(node, *args, **kwargs) | |
| # Do constant folding. Some other nodes besides Expr have | |
| # as_const, but folding them causes errors later on. | |
| if isinstance(node, nodes.Expr): | |
| try: | |
| return nodes.Const.from_untrusted( | |
| node.as_const(args[0] if args else None), | |
| lineno=node.lineno, | |
| environment=self.environment, | |
| ) | |
| except nodes.Impossible: | |
| pass | |
| return node | |