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