def get_conjuncts(qvars, conjunction):
if conjunction.decl().kind() == z3.Z3_OP_AND:
return [
z3.substitute_vars(kid, *qvars) for kid in conjunction.children()
]
else:
return [z3.substitute_vars(conjunction, *qvars)]
def __init__(self,rule):
""" unpacks a rule of the kind
(I) z3.Forall(variables, head)
or
(II) z3.Forall(variables, z3.Implies(z3.And([tail,children]),head))
"""
self.rule = rule # original rule
self.variables = None # quantified variables
self.predicate = None # predicate declaration: name(pc,...)
self.tail = None # body predicate
self.children = None # other body elements
self.head = None # head predicate
# the rule is a z3 quantifier
if z3.is_quantifier(rule):
# quantified variables
self.variables = list()
for i in range(rule.num_vars()):
sort = self.var_sort(rule,i).kind()
if sort == z3.Z3_INT_SORT:
self.variables.append(z3.Int(self.var_name(rule,i)))
elif sort == z3.Z3_BOOL_SORT:
self.variables.append(z3.Bool(self.var_name(rule,i)))
else:
raise ValueError('unsopported sort:',sort)
# unpacks the rule body
head = rule.body()
if z3.is_app_of(head,z3.Z3_OP_IMPLIES):
# the rule is of kind (II)
body = head.arg(0) # z3.Implies body
if z3.is_app_of(body,z3.Z3_OP_AND):
# unpacks the other body elements
# (assumes single uninterpreted predicate in body)
self.children = list()
for c in body.children():
child = z3.substitute_vars(c,*self.variables)
# unpacks the body predicate
if z3.is_app_of(child,z3.Z3_OP_UNINTERPRETED) \
and self.tail is None:
self.tail = child # body predicate
else:
self.children.append(child)
else:
raise ValueError('unsupported implication body:',body)
head = head.arg(1) # z3.Implies head
if z3.is_app_of(head,z3.Z3_OP_UNINTERPRETED):
# the rule is of kind (I)
name = head.decl().name() # predicate name
parameters = list() # predicate parameters
arguments = list() # predicate arguments
for i in range(head.num_args()):
arg = head.arg(i)
parameters.append(arg.sort())
arguments.append(z3.substitute_vars(arg,*self.variables))
parameters.append(z3.BoolSort())
self.predicate = z3.Function(name,*parameters)
self.head = self.predicate(*arguments) # head predicate
else:
raise ValueError('unsupported rule body:',body)
def __init__(self, rule):
""" unpacks a rule of the kind
(I) z3.Forall(variables, head)
or
(II) z3.Forall(variables, z3.Implies(z3.And([tail,children]),head))
"""
self.rule = rule # original rule
self.variables = None # quantified variables
self.predicate = None # predicate declaration: name(pc,...)
self.tail = None # body predicate
self.children = None # other body elements
self.head = None # head predicate
# the rule is a z3 quantifier
if z3.is_quantifier(rule):
# quantified variables
self.variables = list()
for i in range(rule.num_vars()):
sort = self.var_sort(rule, i).kind()
if sort == z3.Z3_INT_SORT:
self.variables.append(z3.Int(self.var_name(rule, i)))
elif sort == z3.Z3_BOOL_SORT:
self.variables.append(z3.Bool(self.var_name(rule, i)))
else:
raise ValueError("unsopported sort:", sort)
# unpacks the rule body
head = rule.body()
if z3.is_app_of(head, z3.Z3_OP_IMPLIES):
# the rule is of kind (II)
body = head.arg(0) # z3.Implies body
if z3.is_app_of(body, z3.Z3_OP_AND):
# unpacks the other body elements
# (assumes single uninterpreted predicate in body)
self.children = list()
for c in body.children():
child = z3.substitute_vars(c, *self.variables)
# unpacks the body predicate
if z3.is_app_of(child, z3.Z3_OP_UNINTERPRETED) and self.tail is None:
self.tail = child # body predicate
else:
self.children.append(child)
else:
raise ValueError("unsupported implication body:", body)
head = head.arg(1) # z3.Implies head
if z3.is_app_of(head, z3.Z3_OP_UNINTERPRETED):
# the rule is of kind (I)
name = head.decl().name() # predicate name
parameters = list() # predicate parameters
arguments = list() # predicate arguments
for i in range(head.num_args()):
arg = head.arg(i)
parameters.append(arg.sort())
arguments.append(z3.substitute_vars(arg, *self.variables))
parameters.append(z3.BoolSort())
self.predicate = z3.Function(name, *parameters)
self.head = self.predicate(*arguments) # head predicate
else:
raise ValueError("unsupported rule body:", body)
def substitute_vars(t, *m):
"""Substitute the free variables in t with the expression in m."""
# Redefining this here so that the clients of this class aren't forced to
# import any replacement-related functions directly from z3, thus making
# it a little easier to add other backends in the future.
#logger.info("Will substitute into {} arguments {} of sorts {}".format(t, m, map(lambda v : v.sort(), m)))
return z3.substitute_vars(t, *m)
def write_clause_smt2(forall, pref, writer):
if not (z3.is_quantifier(forall) and forall.is_forall()):
raise Exception("Illegal clause for write_clause_smt2: {}".format(
forall.decl()))
writer.write("{}(forall (".format(pref))
for idx in range(0, forall.num_vars()):
writer.write(" ({} {})".format(forall.var_name(idx),
forall.var_sort(idx).sexpr()))
writer.write(" ) \n".format(pref))
implication = forall.body()
subst = list(
reversed([
z3.Const(forall.var_name(n), forall.var_sort(n))
for n in range(0, forall.num_vars())
]))
implication = z3.substitute_vars(implication, *subst)
write_implication_smt2(implication, pref + ' ', None, writer)
writer.write("\n{})".format(pref))
def stripQuantifierBlock (expr) :
""" strips the outermost quantifier block in a given expression and returns
the pair (<list of consts replacing free vars>,
<body with consts substituted for de-bruijn variables>)
Example:
assume expr.is_forall ()
vars, body = strip_quantifier (expr)
qexpr = z3.ForAll (vars, body)
assert qexpr.eq (expr)
"""
if not z3.is_quantifier (expr) : return ([], expr)
global qb_counter
z3ctx = expr.ctx
consts = list ()
# outside-in order of variables; z3 numbers variables inside-out but
# substitutes outside-in
for i in reversed (range (expr.num_vars ())) :
#v_name = expr.var_name (i) + "!" + str(qb_counter)
v_name = expr.var_name (i)
qb_counter+=1
v_sort = expr.var_sort (i)
consts.append (z3.Const (v_name, z3_translate (v_sort, z3ctx)))
matrix = z3.substitute_vars (expr.body (), *consts)
return (consts, matrix)
def eval(self, term):
fn = self.get_fn(term.decl().name())
# lambdas seem to be broken at the moment
# this is a work around
body = fn.body()
body = z3.substitute_vars(body, *reversed(term.children()))
return body
def stripQuantifierBlock (expr) :
""" strips the outermost quantifier block in a given expression and returns
the pair (<list of consts replacing free vars>,
<body with consts substituted for de-bruijn variables>)
Example:
assume expr.is_forall ()
vars, body = strip_quantifier (expr)
qexpr = z3.ForAll (vars, body)
assert qexpr.eq (expr)
"""
if not z3.is_quantifier (expr) : return ([], expr)
global qb_counter
z3ctx = expr.ctx
consts = list ()
# outside-in order of variables; z3 numbers variables inside-out but
# substitutes outside-in
for i in reversed (range (expr.num_vars ())) :
v_name = expr.var_name (i) + "!" + str(qb_counter)
qb_counter+=1
v_sort = expr.var_sort (i)
consts.append (z3.Const (v_name, z3_translate (v_sort, z3ctx)))
matrix = z3.substitute_vars (expr.body (), *consts)
return (consts, matrix)
def fp_get_cover_delta(fp, pred, level=-1):
sub = []
for i in range(0, pred.num_args()):
sub.append(pred.arg(i))
lemma = fp.get_cover_delta(level, pred.decl())
if z3core.Z3_get_bool_value(fp.ctx.ctx, lemma.as_ast()) != z3.unsat:
lemma = z3.substitute_vars(lemma, *sub)
return lemma
def fp_get_cover_delta (fp, pred, level=-1):
sub = []
for i in range (0, pred.num_args ()):
sub.append (pred.arg (i))
lemma = fp.get_cover_delta (level, pred.decl ())
if z3core.Z3_get_bool_value (fp.ctx.ctx, lemma.as_ast ()) != z3.unsat:
lemma = z3.substitute_vars (lemma, *sub)
return lemma
def strip_qblock(expr):
if not z3.is_quantifier(expr): return ([], expr)
consts = list()
for i in reversed(range(expr.num_vars())):
v_name = expr.var_name(i)
v_sort = expr.var_sort(i)
consts.append(z3.Const(v_name, v_sort))
matrix = z3.substitute_vars(expr.body(), *consts)
return (consts, matrix)
def ground_quantifier(qexpr):
body = qexpr.body()
vars = list()
for i in reversed(range(qexpr.num_vars())):
vi_name = qexpr.var_name(i)
vi_sort = qexpr.var_sort(i)
vi = z3.Const(vi_name, vi_sort)
vars.append(vi)
body = z3.substitute_vars(body, *vars)
return (body, vars)
def extract_implies(clause):
qvars, implies = fix_quantifier(clause)
implies = z3.substitute_vars(implies, *list(reversed(qvars)))
kids = implies.children()
tail = get_conjuncts(qvars, kids[0])
head = kids[1]
return {
'qvars': qvars,
'tail': tail,
'head': head,
}
def lemma_to_string(lemma, pred):
"""
convert a lemma returned by get_cover_delta into a string that parse_smt2_string can parse
"""
const_list = [z3.Const(pred.name()+"_"+str(j), pred.domain(j)) for j in range(pred.arity())]
lhs = pred(*const_list)
rhs = z3.substitute_vars(lemma, *(const_list))
imp = z3.Implies(lhs, rhs)
forall = z3.ForAll(list(reversed(const_list)), imp)
lemma_str = "(assert %s)"%forall.sexpr()
print("\toriginal lemma:", lemma)
print("\tforall lemma:", forall.body().arg(1))
assert lemma == forall.body().arg(1)
return lemma_str
def extract_implies(clause):
clause = fix_quantifier(clause)
qvars = [
z3.Const(clause.var_name(n), clause.var_sort(n))
for n in range(0, clause.num_vars())
]
implies = fix_implies(clause.body())
kids = implies.children()
body = get_conjuncts(qvars, kids[0])
head = z3.substitute_vars(kids[1], *qvars)
return {
'qvars': qvars,
'body': body,
'head': head,
}
def write_clauses_datalog(declarations, clauses, writer):
reserved_exit_point = 'reserved_exit_point'
writer.write('(declare-rel {} ())\n\n'.format(reserved_exit_point))
for decl in declarations:
symbol = quote_symbol_if_needed(decl.name())
writer.write('(declare-rel {} ('.format(symbol))
for n in range(0, decl.arity()):
writer.write((" {}".format(decl.domain(n))))
writer.write(' ))\n')
known_vars = set([])
implications = []
writer.write('\n')
for clause in clauses:
if not (z3.is_quantifier(clause) and clause.is_forall()):
raise Exception("Illegal clause for write_clause_smt2: {}".format(
clause.decl()))
for idx in range(0, clause.num_vars()):
if (clause.var_name(idx), clause.var_sort(idx)) not in known_vars:
known_vars.add((clause.var_name(idx), clause.var_sort(idx)))
writer.write("(declare-var {} {})\n".format(
clause.var_name(idx),
clause.var_sort(idx).sexpr()))
implication = clause.body()
subst = list(
reversed([
z3.Const(clause.var_name(n), clause.var_sort(n))
for n in range(0, clause.num_vars())
]))
implications.append(z3.substitute_vars(implication, *subst))
writer.write('\n')
for implication in implications:
writer.write('(rule\n')
write_implication_smt2(implication, ' ', reserved_exit_point, writer)
writer.write('\n)\n')
writer.write('\n\n(query {})\n\n'.format(reserved_exit_point))
def negated_body(formula):
"""Given a z3.QuantiferRef formula with z3.Int variables,
return negation of the body.
Returns:
A z3.BoolRef which is the negation of the formula body.
"""
assert z3.is_quantifier(formula), ('Formula is not a quantifier:\n',
formula)
var_names = [formula.var_name(i) for i in range(formula.num_vars())]
vs = [z3.Int(n) for n in var_names]
# Here simply doing z3.Not(formula.body()) doesn't work. formula.body()
# returns an expression without any bounded variable, i.e., it refers
# variables using indices in the order they appear instead of its names,
# Var(0), Var(1), Var(2). Thus, we have to re-bind the variables using
# substitute_vars. It is also necessary to reverse the list of variables.
# See https://github.com/Z3Prover/z3/issues/402 for more details.
return z3.Not(z3.substitute_vars(formula.body(), *reversed(vs)))
def termination(self,entry,header,kind,pieces,loop,exit):
""" instruments the rules in fp with a ranking function
in order to extract a NON-TERMINATING execution
such that rank is negative within the loop
"""
def mx(rankings):
""" builds a MAX combination of a list of ranking functions """
if len(rankings) <= 1:
return rankings[0]
else:
r = mx(rankings[1:])
return z3.If(rankings[0] < r,r,rankings[0])
# new z3.Fixedpoint object
fp = z3.Fixedpoint()
fp.set(engine='spacer')
fp.set('xform.inline_eager', False)
fp.set('xform.slice', False)
fp.set('xform.inline_linear', False)
fp.set('pdr.utvpi', False)
# fp.set('timeout',1000)
# variable declarations
for x in self.variables:
fp.declare_var(x)
# ranking function counter
components = len(pieces)
R = [z3.Int('R%d' % i) for i in range(components)]
for component in R: fp.declare_var(component)
RR = [z3.Int('RR%d' % i) for i in range(components)]
for component in RR: fp.declare_var(component)
# modifying and adding rules
for rule in self.rules:
r = Rule(rule.rule)
if r.is_entry(entry):
# ranking function(s) initialization before the loop
rank = [[z3.substitute_vars(x,*r.head_args()[1:])
for x in component] for component in pieces]
r.add_rank(R,[mx(component) for component in rank],RR)
fp.register_relation(r.predicate)
# print 'ENTRY:', r
elif r.is_loop(loop):
# ranking function(s) strict decrease within the loop
rank = [[z3.substitute_vars(x,*r.head_args()[1:])
for x in component] for component in pieces]
r.add_decrease(kind,R,[mx(component) for component in rank],RR)
# print 'LOOP:', r
# ranking function(s) boundedness from below within the loop
q = Rule(rule.rule)
q.add_bound(kind,R)
q.head_pc(-1)
fp.rule(q.head,[q.tail] + q.children)
# print 'EXIT:', q
# query
query = z3.Exists(q.variables,q.head)
else:
r.add_vars(R)
# print 'NONE:', r
# adding modified rules
if r.tail is None:
fp.rule(r.head)
else:
fp.rule(r.head,[r.tail] + r.children)
# print '\nFP:', fp
# querying for non-terminating execution
result = fp.query(query)
if result == z3.sat:
answer = fp.get_ground_sat_answer()
first = answer.children()[-2]
point = [x.as_long() for x in first.children()[1:-1]]
return list(zip(self.arguments[1:],point))
else:
return []
def substitute_vars (t, *m): rw = SubstituteVars (*m) res = rw (t) assert res.eq (z3.substitute_vars (t, *m)) return res
def termination(self, entry, header, kind, pieces, loop, exit):
""" instruments the rules in fp with a ranking function
in order to extract a NON-TERMINATING execution
such that rank is negative within the loop
"""
def mx(rankings):
""" builds a MAX combination of a list of ranking functions """
if len(rankings) <= 1:
return rankings[0]
else:
r = mx(rankings[1:])
return z3.If(rankings[0] < r, r, rankings[0])
# new z3.Fixedpoint object
fp = z3.Fixedpoint()
fp.set(engine="spacer")
fp.set("xform.inline_eager", False)
fp.set("xform.slice", False)
fp.set("xform.inline_linear", False)
fp.set("pdr.utvpi", False)
# fp.set('timeout',1000)
# variable declarations
for x in self.variables:
fp.declare_var(x)
# ranking function counter
components = len(pieces)
R = [z3.Int("R%d" % i) for i in range(components)]
for component in R:
fp.declare_var(component)
RR = [z3.Int("RR%d" % i) for i in range(components)]
for component in RR:
fp.declare_var(component)
# modifying and adding rules
for rule in self.rules:
r = Rule(rule.rule)
if r.is_entry(entry):
# ranking function(s) initialization before the loop
rank = [[z3.substitute_vars(x, *r.head_args()[1:]) for x in component] for component in pieces]
r.add_rank(R, [mx(component) for component in rank], RR)
fp.register_relation(r.predicate)
# print 'ENTRY:', r
elif r.is_loop(loop):
# ranking function(s) strict decrease within the loop
rank = [[z3.substitute_vars(x, *r.head_args()[1:]) for x in component] for component in pieces]
r.add_decrease(kind, R, [mx(component) for component in rank], RR)
# print 'LOOP:', r
# ranking function(s) boundedness from below within the loop
q = Rule(rule.rule)
q.add_bound(kind, R)
q.head_pc(-1)
fp.rule(q.head, [q.tail] + q.children)
# print 'EXIT:', q
# query
query = z3.Exists(q.variables, q.head)
else:
r.add_vars(R)
# print 'NONE:', r
# adding modified rules
if r.tail is None:
fp.rule(r.head)
else:
fp.rule(r.head, [r.tail] + r.children)
# print '\nFP:', fp
# querying for non-terminating execution
result = fp.query(query)
if result == z3.sat:
answer = fp.get_ground_sat_answer()
first = answer.children()[-2]
point = [x.as_long() for x in first.children()[1:-1]]
return zip(self.arguments[1:], point)
else:
return []
def piecewise(fp):
# program CFG
program = Program(fp)
parameters = program.parameters[1:]
variables = [
z3.Var(i, sort)
for (i, sort) in zip(list(range(len(parameters))), parameters)
]
arguments = program.arguments[1:]
# loops identification
loops = program.loops_identification()
# proving termination...
rank = dict()
for node in loops:
# ...for all loops involving each node
if loops[node]:
if debug: print('\nloop:', loops[node], '\n')
loop = set([n for path in loops[node] for n in path]) # loop nodes
entry = set([(n, node)
for n in program.prev[node] - loop]) # entry edges
edges = set([
n for path in loops[node] for n in zip(path[:-1], path[1:])
]) # loop edges
# exit = set([(node,n)
# for n in program.next[node] - loop]) # exit edges
exit = set([(i, n) for i in loop
for n in program.next[i] - loop]) # exit edges
bits = list() # (potentially) terminating bits
pieces = [[z3.IntSort().cast(0)]] # candidate ranking functions
bit = program.get_bit(entry, node, 'max', pieces, edges, exit)
while bit:
bit[node][0][-len(pieces)] -= bit[node][-1][-len(pieces)]
bits.append(bit[node][0][:len(bit[node][0]) - len(pieces) + 1])
rankings = ranking(bits, variables)
for i in range(len(bits)):
rankings = ranking(bits[:i + 1], variables)
if not rankings:
if debug: print()
del bits[:-1]
rankings = ranking(bits, variables)
if debug:
print(
'bit:',
list(
zip(arguments + ['-' for component in pieces],
bits[-1])))
pieces[0].extend(rankings)
if debug:
print('pieces:', [[
z3.substitute_vars(x, *arguments) for x in component
] for component in pieces])
bit = program.get_bit(entry, node, 'max', pieces, edges, exit)
# check candidate ranking functions
point = program.termination(entry, node, 'max', pieces, edges,
exit)
pieces = [[z3.substitute_vars(x, *arguments) for x in component]
for component in pieces]
if point:
rank[node] = (False, point)
if debug: print('\nnon-terminating execution:', point)
if debug: print('(partial) loop ranking functions:', pieces)
else:
rank[node] = (True, pieces)
if debug: print('\nloop ranking functions:', pieces)
if debug: print('\nranking functions:', rank)
if all([r[0] for r in list(rank.values())]):
stat("Result", "TRUE")
else:
stat("Result", "FALSE")
def get_bit(self, entry, header, kind, pieces, loop, exit):
""" instruments the program rules with a ranking function
in order to extract a TERMINATING execution
such that rank is negative at loop exit
"""
def mx(rankings):
""" builds a MAX combination of a list of ranking functions """
if len(rankings) <= 1:
return rankings[0]
else:
r = mx(rankings[1:])
return z3.If(rankings[0] < r, r, rankings[0])
# new z3.Fixedpoint object
fp = z3.Fixedpoint()
fp.set(engine="spacer")
fp.set("xform.inline_eager", False)
fp.set("xform.slice", False)
fp.set("xform.inline_linear", False)
fp.set("pdr.utvpi", False)
# fp.set('timeout',1000)
# variable declarations
for x in self.variables:
fp.declare_var(x)
# ranking function counter
components = len(pieces)
R = [z3.Int("R%d" % i) for i in range(components)]
for component in R:
fp.declare_var(component)
RR = [z3.Int("RR%d" % i) for i in range(components)]
for component in RR:
fp.declare_var(component)
# modifying and adding rules
for rule in self.rules:
r = Rule(rule.rule)
if r.is_entry(entry):
# ranking function(s) initialization before the loop
rank = [[z3.substitute_vars(x, *r.head_args()[1:]) for x in component] for component in pieces]
r.add_rank(R, [mx(component) for component in rank], RR)
fp.register_relation(r.predicate)
elif r.is_loop(loop):
# ranking function(s) strict decrease within the loop
rank = [[z3.substitute_vars(x, *r.head_args()[1:]) for x in component] for component in pieces]
r.add_decrease(kind, R, [mx(component) for component in rank], RR)
elif r.is_exit(exit):
r.add_vars(R)
# ranking function(s) boundedness from below after the loop
q = Rule(rule.rule)
q.add_bound(kind, R)
q.head_pc(-1)
fp.rule(q.head, [q.tail] + q.children)
# query
query = z3.Exists(q.variables, q.head)
else:
r.add_vars(R)
# print 'NONE:', r
# adding modified rules
if r.tail is None:
fp.rule(r.head)
else:
body = [r.tail] + r.children
fp.rule(r.head, body)
# querying for terminating execution with negative ranking function
bit = dict()
result = fp.query(query)
if result == z3.sat:
answer = fp.get_ground_sat_answer()
children = answer.children()
# print 'CHILDREN:\n', children
bit = dict()
for child in children:
if child.children(): # some predicate might not have values
values = [x.as_long() for x in child.children()]
if values[0] not in bit:
bit[values[0]] = [values[1:]]
else:
bit[values[0]].insert(0, values[1:])
# adding the first child to loop header to ensure progress
# (when the source of exit edges is not the loop header)
first = [child for child in children if child.children()][0]
values = [x.as_long() for x in first.children()]
if header not in bit:
bit[header] = [values[1:]]
else:
bit[header].append(values[1:])
return bit
else:
return bit
def piecewise(fp):
# program CFG
program = Program(fp)
parameters = program.parameters[1:]
variables = [z3.Var(i, sort) for (i,sort)
in zip(list(range(len(parameters))),parameters)]
arguments = program.arguments[1:]
# loops identification
loops = program.loops_identification()
# proving termination...
rank = dict()
for node in loops:
# ...for all loops involving each node
if loops[node]:
if debug: print '\nloop:', loops[node], '\n'
loop = set([n for path in loops[node] for n in path]) # loop nodes
entry = set([(n,node)
for n in program.prev[node] - loop]) # entry edges
edges = set([n for path in loops[node]
for n in zip(path[:-1],path[1:])]) # loop edges
# exit = set([(node,n)
# for n in program.next[node] - loop]) # exit edges
exit = set([(i,n)
for i in loop for n in program.next[i] - loop]) # exit edges
bits = list() # (potentially) terminating bits
pieces = [[z3.IntSort().cast(0)]] # candidate ranking functions
bit = program.get_bit(entry,node,'max',pieces,edges,exit)
while bit:
bit[node][0][-len(pieces)] -= bit[node][-1][-len(pieces)]
bits.append(bit[node][0][:len(bit[node][0])-len(pieces)+1])
rankings = ranking(bits,variables)
for i in range(len(bits)):
rankings = ranking(bits[:i+1],variables)
if not rankings:
if debug: print
del bits[:-1]
rankings = ranking(bits,variables)
if debug: print 'bit:', zip(arguments + ['-'
for component in pieces],bits[-1])
pieces[0].extend(rankings)
if debug: print 'pieces:', [[z3.substitute_vars(x,*arguments)
for x in component] for component in pieces]
bit = program.get_bit(entry,node,'max',pieces,edges,exit)
# check candidate ranking functions
point = program.termination(entry,node,'max',pieces,edges,exit)
pieces = [[z3.substitute_vars(x,*arguments)
for x in component] for component in pieces]
if point:
rank[node] = (False,point)
if debug: print '\nnon-terminating execution:', point
if debug: print '(partial) loop ranking functions:', pieces
else:
rank[node] = (True,pieces)
if debug: print '\nloop ranking functions:', pieces
if debug: print '\nranking functions:', rank
if all([r[0] for r in rank.values()]):
stat("Result", "TRUE")
else:
stat("Result", "FALSE")
def get_bit(self,entry,header,kind,pieces,loop,exit):
""" instruments the program rules with a ranking function
in order to extract a TERMINATING execution
such that rank is negative at loop exit
"""
def mx(rankings):
""" builds a MAX combination of a list of ranking functions """
if len(rankings) <= 1:
return rankings[0]
else:
r = mx(rankings[1:])
return z3.If(rankings[0] < r,r,rankings[0])
# new z3.Fixedpoint object
fp = z3.Fixedpoint()
fp.set(engine='spacer')
fp.set('xform.inline_eager', False)
fp.set('xform.slice', False)
fp.set('xform.inline_linear', False)
fp.set('pdr.utvpi', False)
# fp.set('timeout',1000)
# variable declarations
for x in self.variables:
fp.declare_var(x)
# ranking function counter
components = len(pieces)
R = [z3.Int('R%d' % i) for i in range(components)]
for component in R: fp.declare_var(component)
RR = [z3.Int('RR%d' % i) for i in range(components)]
for component in RR: fp.declare_var(component)
# modifying and adding rules
for rule in self.rules:
r = Rule(rule.rule)
if r.is_entry(entry):
# ranking function(s) initialization before the loop
rank = [[z3.substitute_vars(x,*r.head_args()[1:])
for x in component] for component in pieces]
r.add_rank(R,[mx(component) for component in rank],RR)
fp.register_relation(r.predicate)
elif r.is_loop(loop):
# ranking function(s) strict decrease within the loop
rank = [[z3.substitute_vars(x,*r.head_args()[1:])
for x in component] for component in pieces]
r.add_decrease(kind,R,[mx(component) for component in rank],RR)
elif r.is_exit(exit):
r.add_vars(R)
# ranking function(s) boundedness from below after the loop
q = Rule(rule.rule)
q.add_bound(kind,R)
q.head_pc(-1)
fp.rule(q.head,[q.tail] + q.children)
# query
query = z3.Exists(q.variables,q.head)
else:
r.add_vars(R)
# print 'NONE:', r
# adding modified rules
if r.tail is None:
fp.rule(r.head)
else:
body = [r.tail] + r.children
fp.rule(r.head,body)
# querying for terminating execution with negative ranking function
bit = dict()
result = fp.query(query)
if result == z3.sat:
answer = fp.get_ground_sat_answer()
children = answer.children()
# print 'CHILDREN:\n', children
bit = dict()
for child in children:
if child.children(): # some predicate might not have values
values = [x.as_long() for x in child.children()]
if values[0] not in bit:
bit[values[0]] = [values[1:]]
else:
bit[values[0]].insert(0,values[1:])
# adding the first child to loop header to ensure progress
# (when the source of exit edges is not the loop header)
first = [child for child in children if child.children()][0]
values = [x.as_long() for x in first.children()]
if header not in bit:
bit[header] = [values[1:]]
else:
bit[header].append(values[1:])
return bit
else:
return bit
def substitute_vars (t, *m): rw = SubstituteVars (*m) res = rw (t) assert res.eq (z3.substitute_vars (t, *m)) return res
def substitute(self, other, expr):
def update_term(t, args):
n = len(args)
# Need to pass an AstArray type into Z3_update_term, not a python list
args_ast_arr = (z3.Ast * n)()
for i in range(n):
args_ast_arr[i] = args[i].as_ast()
return _to_expr_ref(
z3.Z3_update_term(t.ctx_ref(), t.as_ast(), n, args_ast_arr),
t.ctx)
cache = z3.AstMap(ctx=expr.ctx)
for addr, state in self._expanded_global_state.items():
other_state = other.initial_contract_state(addr)
cache[state.storage] = other_state.storage
cache[state.balance] = other_state.balance
cache[state.nonce] = other_state.nonce
fnsubs = []
for k, v in self._cache.items():
if isinstance(v, mem.Memory):
# Uses of Memory objects will produce an expression containing
# the underlying array object (_mem). If required the index
# (_idx) will have been substituted with the actual indexing
# expression at that point, so we do not need to consider it
# here.
cache[v._mem] = getattr(other, k)()._mem
elif z3.is_app(v) and v.num_args() > 0:
fnsubs.append((v, getattr(other, k)()))
else:
cache[v] = getattr(other, k)()
todo = [expr]
while todo:
n = todo[-1]
if n in cache:
todo.pop()
elif z3.is_var(n):
cache[n] = n
todo.pop()
elif z3.is_app(n):
new_args = []
for i in range(n.num_args()):
arg = n.arg(i)
if arg not in cache:
todo.append(arg)
else:
new_args.append(cache[arg])
# Only actually do the substitution if all the arguments have
# already been processed
if len(new_args) == n.num_args():
todo.pop()
fn = n.decl()
for oldfn, newfn in fnsubs:
if z3.eq(fn, oldfn):
new_fn = z3.substitute_vars(newfn, *new_args)
break
else:
# TODO only if new_args != old_args
if len(new_args) != fn.arity():
new_fn = update_term(n, new_args)
else:
new_fn = fn(*new_args)
cache[n] = new_fn
else:
assert z3.is_quantifier(n)
# Not currently implemented as don't use quanitifers at the
# moment
raise NotImplementedError()
return cache[expr]