| 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768 |
- # -*- coding: utf-8 -*-
- """
- jinja2.optimizer
- ~~~~~~~~~~~~~~~~
- The jinja optimizer is currently trying to constant fold a few expressions
- and modify the AST in place so that it should be easier to evaluate it.
- 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 scoping.
- The solution would be a second syntax tree that has the scoping rules stored.
- :copyright: (c) 2010 by the Jinja Team.
- :license: BSD.
- """
- from jinja2 import nodes
- from jinja2.visitor import NodeTransformer
- def optimize(node, environment):
- """The context hint can be used to perform an static optimization
- based on the context given."""
- optimizer = Optimizer(environment)
- return optimizer.visit(node)
- class Optimizer(NodeTransformer):
- def __init__(self, environment):
- self.environment = environment
- def visit_If(self, node):
- """Eliminate dead code."""
- # do not optimize ifs that have a block inside so that it doesn't
- # break super().
- if node.find(nodes.Block) is not None:
- return self.generic_visit(node)
- try:
- val = self.visit(node.test).as_const()
- except nodes.Impossible:
- return self.generic_visit(node)
- if val:
- body = node.body
- else:
- body = node.else_
- result = []
- for node in body:
- result.extend(self.visit_list(node))
- return result
- def fold(self, node):
- """Do constant folding."""
- node = self.generic_visit(node)
- try:
- return nodes.Const.from_untrusted(node.as_const(),
- lineno=node.lineno,
- environment=self.environment)
- except nodes.Impossible:
- return node
- visit_Add = visit_Sub = visit_Mul = visit_Div = visit_FloorDiv = \
- visit_Pow = visit_Mod = visit_And = visit_Or = visit_Pos = visit_Neg = \
- visit_Not = visit_Compare = visit_Getitem = visit_Getattr = visit_Call = \
- visit_Filter = visit_Test = visit_CondExpr = fold
- del fold
|
