PYTHON 74
Optimizer.py Guest on 16th April 2021 11:28:59 AM
  1. # -*- coding: utf-8 -*-
  2. """The optimizer tries to constant fold expressions and modify the AST
  3. in place so that it should be faster to evaluate.
  4.  
  5. Because the AST does not contain all the scoping information and the
  6. compiler has to find that out, we cannot do all the optimizations we
  7. want. For example, loop unrolling doesn't work because unrolled loops
  8. would have a different scope. The solution would be a second syntax tree
  9. that stored the scoping rules.
  10. """
  11. from . import nodes
  12. from .visitor import NodeTransformer
  13.  
  14.  
  15. def optimize(node, environment):
  16.     """The context hint can be used to perform an static optimization
  17.    based on the context given."""
  18.     optimizer = Optimizer(environment)
  19.     return optimizer.visit(node)
  20.  
  21.  
  22. class Optimizer(NodeTransformer):
  23.     def __init__(self, environment):
  24.         self.environment = environment
  25.  
  26.     def generic_visit(self, node, *args, **kwargs):
  27.         node = super(Optimizer, self).generic_visit(node, *args, **kwargs)
  28.  
  29.         # Do constant folding. Some other nodes besides Expr have
  30.         # as_const, but folding them causes errors later on.
  31.         if isinstance(node, nodes.Expr):
  32.             try:
  33.                 return nodes.Const.from_untrusted(
  34.                     node.as_const(args[0] if args else None),
  35.                     lineno=node.lineno,
  36.                     environment=self.environment,
  37.                 )
  38.             except nodes.Impossible:
  39.                 pass
  40.  
  41.         return node

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