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''' Simplify expressions based on range information when possible'''
from pythran.analyses import RangeValues
from pythran.passmanager import Transformation
import gast as ast
from math import isinf
from copy import deepcopy
class RangeBasedSimplify(Transformation):
'''
Simplify expressions based on range analysis
>>> import gast as ast
>>> from pythran import passmanager, backend
>>> node = ast.parse("def any():\\n for x in builtins.range(10): y=x%8")
>>> pm = passmanager.PassManager("test")
>>> _, node = pm.apply(RangeBasedSimplify, node)
>>> print(pm.dump(backend.Python, node))
def any():
for x in builtins.range(10):
y = (x if (x < 8) else (x - 8))
>>> node = ast.parse("def any(): x = 1 or 2; return 3 == x")
>>> pm = passmanager.PassManager("test")
>>> _, node = pm.apply(RangeBasedSimplify, node)
>>> print(pm.dump(backend.Python, node))
def any():
x = (1 or 2)
return 0
>>> node = ast.parse("def a(i): x = 1,1,2; return x[2], x[0 if i else 1]")
>>> pm = passmanager.PassManager("test")
>>> _, node = pm.apply(RangeBasedSimplify, node)
>>> print(pm.dump(backend.Python, node))
def a(i):
x = (1, 1, 2)
return (2, 1)
'''
def __init__(self):
Transformation.__init__(self, RangeValues)
def visit_OMPDirective(self, node):
return node
def visit_BinOp(self, node):
node = self.generic_visit(node)
if not isinstance(node.op, ast.Mod):
return node
right_range = self.range_values[node.right]
left_range = self.range_values[node.left]
if right_range.low < 0 or isinf(right_range.high):
return node
if left_range.low < -right_range.low:
return node
if left_range.high > right_range.high * 2:
return node
cleft0, cleft1 = deepcopy(node.left), deepcopy(node.left)
cright = deepcopy(node.right)
self.update = True
return ast.IfExp(ast.Compare(node.left, [ast.Lt()], [node.right]),
cleft0,
ast.BinOp(cleft1, ast.Sub(), cright))
def visit_range(self, node):
range_value = self.range_values[node]
if isinf(range_value.high):
return self.generic_visit(node)
elif range_value.low == range_value.high:
self.update = True
return ast.Constant(range_value.low, None)
else:
return self.generic_visit(node)
visit_Compare = visit_range
def visit_Name(self, node):
if isinstance(node.ctx, ast.Load):
return self.visit_range(node)
return self.generic_visit(node)
visit_Subscript = visit_Name
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