void bv_cbmct::convert_waitfor(const exprt &expr, bvt &bv)
{
if(expr.operands().size()!=4)
throw "waitfor expected to have four operands";
exprt new_cycle;
const exprt &old_cycle=expr.op0();
const exprt &cycle_var=expr.op1();
const exprt &bound=expr.op2();
const exprt &predicate=expr.op3();
make_free_bv_expr(expr.type(), new_cycle);
mp_integer bound_value;
if(to_integer(bound, bound_value))
throw "waitfor bound must be a constant";
{
// constraint: new_cycle>=old_cycle
exprt rel_expr(ID_ge, bool_typet());
rel_expr.copy_to_operands(new_cycle, old_cycle);
set_to_true(rel_expr);
}
{
// constraint: new_cycle<=bound+1
exprt one=from_integer(1, bound.type());
exprt bound_plus1(ID_plus, bound.type());
bound_plus1.reserve_operands(2);
bound_plus1.copy_to_operands(bound);
bound_plus1.move_to_operands(one);
exprt rel_expr(ID_le, bool_typet());
rel_expr.copy_to_operands(new_cycle, bound_plus1);
set_to_true(rel_expr);
}
for(mp_integer i=0; i<=bound_value; i=i+1)
{
// replace cycle_var by old_cycle+i;
exprt old_cycle_plus_i(ID_plus, old_cycle.type());
old_cycle_plus_i.operands().resize(2);
old_cycle_plus_i.op0()=old_cycle;
old_cycle_plus_i.op1()=from_integer(i, old_cycle.type());
exprt tmp_predicate=predicate;
replace_expr(cycle_var, old_cycle_plus_i, tmp_predicate);
// CONSTRAINT:
// if((cycle)<=bound) {
// if((cycle)<new_cycle)
// assume(!property);
// else if((cycle)==new_cycle)
// assume(property);
{
exprt cycle_le_bound(ID_le, bool_typet());
cycle_le_bound.operands().resize(2);
cycle_le_bound.op0()=old_cycle_plus_i;
cycle_le_bound.op1()=bound;
exprt cycle_lt_new_cycle(ID_lt, bool_typet());
cycle_lt_new_cycle.operands().resize(2);
cycle_lt_new_cycle.op0()=old_cycle_plus_i;
cycle_lt_new_cycle.op1()=new_cycle;
exprt and_expr(ID_and, bool_typet());
and_expr.operands().resize(2);
and_expr.op0().swap(cycle_le_bound);
and_expr.op1().swap(cycle_lt_new_cycle);
exprt top_impl(ID_implies, bool_typet());
top_impl.reserve_operands(2);
top_impl.move_to_operands(and_expr);
top_impl.copy_to_operands(tmp_predicate);
top_impl.op1().make_not();
set_to_true(top_impl);
}
{
exprt cycle_le_bound(ID_le, bool_typet());
cycle_le_bound.operands().resize(2);
cycle_le_bound.op0()=old_cycle_plus_i;
cycle_le_bound.op1()=bound;
exprt cycle_eq_new_cycle(ID_equal, bool_typet());
cycle_eq_new_cycle.operands().resize(2);
cycle_eq_new_cycle.op0()=old_cycle_plus_i;
cycle_eq_new_cycle.op1()=new_cycle;
exprt and_expr(ID_and, bool_typet());
and_expr.operands().resize(2);
and_expr.op0().swap(cycle_le_bound);
and_expr.op1().swap(cycle_eq_new_cycle);
exprt top_impl(ID_implies, bool_typet());
top_impl.reserve_operands(2);
top_impl.move_to_operands(and_expr);
top_impl.copy_to_operands(tmp_predicate);
set_to_true(top_impl);
}
}
// result: new_cycle
return convert_bitvector(new_cycle, bv);
}
