def check_twomult(self, target, pattern):
'Check 2*... pattern that could be in another form'
if isinstance(pattern.left, ast.Num) and pattern.left.n == 2:
operand = pattern.right
elif isinstance(pattern.right, ast.Num) and pattern.right.n == 2:
operand = pattern.left
else:
return False
# deal with case where wildcard operand and target are const values
if isinstance(target, ast.Num) and isinstance(operand, ast.Name):
conds = (operand.id in self.wildcards
and isinstance(self.wildcards[operand.id], ast.Num))
if conds:
eva = (self.wildcards[operand.id].n) * 2 % 2**(self.nbits)
if eva == target.n:
return True
else:
if target.n % 2 == 0:
self.wildcards[operand.id] = ast.Num(target.n / 2)
return True
return False
# get all wildcards in operand and check if they have value
getwild = asttools.GetIdentifiers()
getwild.visit(operand)
wilds = getwild.variables
for wil in wilds:
if wil not in self.wildcards:
return False
return self.check_eq_z3(target, pattern)
def __init__(self, root, nbits=0):
'Init different components of pattern matcher'
super(PatternMatcher, self).__init__()
# wildcards used in the pattern with their possible values
self.wildcards = {}
# wildcards <-> values that are known not to work
self.no_solution = []
# root node of expression
if isinstance(root, ast.Module):
self.root = root.body[0].value
elif isinstance(root, ast.Expression):
self.root = root.body
else:
self.root = root
if not nbits:
self.nbits = asttools.get_default_nbits(self.root)
else:
self.nbits = nbits
# identifiers for z3 evaluation
getid = asttools.GetIdentifiers()
getid.visit(self.root)
self.variables = getid.variables
self.functions = getid.functions
def test_xor36(self):
'Test that CSE of the xor36 function is equivalent to original'
# pylint: disable=exec-used
pwd = os.path.dirname(os.path.realpath(__file__))
input_file = open(os.path.join(pwd, 'xor36_flat'), 'r')
input_string = input_file.read()
input_ast = ast.parse(input_string)
coderef = compile(ast.Expression(input_ast.body[0].value), '<string>',
'eval')
jack = asttools.GetIdentifiers()
jack.visit(input_ast)
cse_string = cse.apply_cse(input_string)
# get all assignment in one ast
assigns = cse_string[:cse_string.rfind('\n')]
cse_assign_ast = ast.parse(assigns, mode='exec')
assign_code = compile(cse_assign_ast, '<string>', mode='exec')
# get final expression in one ast
result_string = cse_string.splitlines()[-1]
result_ast = ast.Expression(ast.parse(result_string).body[0].value)
result_code = compile(result_ast, '<string>', mode='eval')
for var in list(jack.variables):
exec("%s = z3.BitVec('%s', 8)" % (var, var))
exec(assign_code)
sol = z3.Solver()
sol.add(eval(coderef) != eval(result_code))
self.assertEqual(sol.check().r, -1)
def generic_test(self, tests):
'Generic test for GetIdentifiers class'
geti = asttools.GetIdentifiers()
for instring, varref, funref in tests:
geti.reset()
inast = ast.parse(instring)
geti.visit(inast)
self.assertEquals(geti.variables, varref)
self.assertEquals(geti.functions, funref)
def general_check(self, target, pattern):
'General check, very time-consuming, not used at the moment'
getwild = asttools.GetIdentifiers()
getwild.visit(pattern)
wilds = list(getwild.variables)
if all(wil in self.wildcards for wil in wilds):
eval_pattern = deepcopy(pattern)
eval_pattern = EvalPattern(self.wildcards).visit(eval_pattern)
return self.check_eq_z3(target, eval_pattern)
return False
def run(expr_ast, nbits):
'Apply sympy arithmetic simplifications to expression ast'
# variables for sympy symbols
getid = asttools.GetIdentifiers()
getid.visit(expr_ast)
variables = getid.variables
functions = getid.functions
original_type = type(expr_ast)
# copying to avoid wierd pointer behaviour
expr_ast = deepcopy(expr_ast)
# converting expr_ast into an ast.Expression
if not isinstance(expr_ast, ast.Expression):
if isinstance(expr_ast, ast.Module):
expr_ast = ast.Expression(expr_ast.body[0].value)
elif isinstance(expr_ast, ast.Expr):
expr_ast = ast.Expression(expr_ast.value)
else:
expr_ast = ast.Expression(expr_ast)
for var in variables:
exec("%s = sympy.Symbol('%s')" % (var, var))
for fun in {"mxor", "mor", "mand", "mnot", "mrshift", "mlshift"}:
exec("%s = sympy.Function('%s')" % (fun, fun))
for fun in functions:
exec("%s = sympy.Function('%s')" % (fun, fun))
expr_ast = asttools.ReplaceBitwiseOp().visit(expr_ast)
ast.fix_missing_locations(expr_ast)
code = compile(expr_ast, '<test>', mode='eval')
eval_expr = eval(code)
try:
expr_ast = ast.parse(str(eval_expr))
except SyntaxError as ex:
print ex
exit(1)
expr_ast = asttools.ReplaceBitwiseFunctions().visit(expr_ast)
# sympy does not consider the number of bits
expr_ast = asttools.GetConstMod(nbits).visit(expr_ast)
# return original type
if original_type == ast.Expression:
expr_ast = ast.Expression(expr_ast.body[0].value)
elif original_type == ast.Expr:
expr_ast = expr_ast.body[0]
elif original_type == ast.Module:
return expr_ast
else:
expr_ast = expr_ast.body[0].value
return expr_ast
def check_eq_z3(self, target, pattern):
'Check equivalence with z3'
# pylint: disable=exec-used
getid = asttools.GetIdentifiers()
getid.visit(target)
if getid.functions:
# not checking exprs with functions for now, because Z3
# does not seem to support function declaration with
# arbitrary number of arguments
return False
for var in self.variables:
exec("%s = z3.BitVec('%s', %d)" % (var, var, self.nbits))
target_ast = deepcopy(target)
target_ast = asttools.Unleveling().visit(target_ast)
ast.fix_missing_locations(target_ast)
code1 = compile(ast.Expression(target_ast), '<string>', mode='eval')
eval_pattern = deepcopy(pattern)
EvalPattern(self.wildcards).visit(eval_pattern)
eval_pattern = asttools.Unleveling().visit(eval_pattern)
ast.fix_missing_locations(eval_pattern)
getid.reset()
getid.visit(eval_pattern)
if getid.functions:
# same reason as before, not using Z3 if there are
# functions
return False
gvar = asttools.GetIdentifiers()
gvar.visit(eval_pattern)
if any(var.isupper() for var in gvar.variables):
# do not check if all patterns have not been replaced
return False
code2 = compile(ast.Expression(eval_pattern), '<string>', mode='eval')
sol = z3.Solver()
if isinstance(eval(code1), int) and eval(code1) == 0:
# cases where target == 0 are too permissive
return False
sol.add(eval(code1) != eval(code2))
return sol.check().r == -1
def get_model(self, target, pattern):
'When target is constant and wildcards have no value yet'
# pylint: disable=exec-used
if target.n == 0:
# zero is too permissive
return False
getwild = asttools.GetIdentifiers()
getwild.visit(pattern)
if getwild.functions:
# not getting model for expr with functions
return False
wilds = getwild.variables
# let's reduce the model to one wildcard for now
# otherwise it adds a lot of checks...
if len(wilds) > 1:
return False
wil = wilds.pop()
if wil in self.wildcards:
if not isinstance(self.wildcards[wil], ast.Num):
return False
folded = deepcopy(pattern)
folded = Unflattening().visit(folded)
EvalPattern(self.wildcards).visit(folded)
folded = asttools.ConstFolding(folded, self.nbits).visit(folded)
return folded.n == target.n
else:
exec("%s = z3.BitVec('%s', %d)" % (wil, wil, self.nbits))
eval_pattern = deepcopy(pattern)
eval_pattern = Unflattening().visit(eval_pattern)
ast.fix_missing_locations(eval_pattern)
code = compile(ast.Expression(eval_pattern), '<string>', mode='eval')
sol = z3.Solver()
sol.add(target.n == eval(code))
if sol.check().r == 1:
model = sol.model()
for inst in model.decls():
self.wildcards[str(inst)] = ast.Num(int(model[inst].as_long()))
return True
return False
