add_possible_sm
add_possible_sm(clone, clone);
add_possible_sm(true_sm, true_sm);
add_possible_sm(false_sm, false_sm);
add_possible_sm(to, to);
add_possible_sm(to, tmp);
add_possible_sm(res, one);
add_possible_sm(res, two);
void add_possible_sm(struct sm_state *to, struct sm_state *new);