possibly_false_rl
if (!possibly_false_rl(rl_left, expr->op, rl_right)) {
int possibly_false_rl(struct range_list *left_ranges, int comparison, struct range_list *right_ranges);
if (!possibly_false_rl(var_rl, comparison, ret_range))
return possibly_false_rl(var_rl, comparison, rl);
poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
return possibly_false_rl(a, comparison, b);
return possibly_false_rl(b, comparison, a);