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