Hint Rewrite sem_cast_pointer2' using (try apply Coq.Init.Logic.I; try assumption; reflexivity) : norm.

Lemma sem_cast_pointer2:
forall v t1 t2 t3 t1' t2',
t1' = Tpointer t1 noattr ->
t2' = Tpointer t2 noattr ->
tc_val (Tpointer t3 noattr) v ->
force_val (sem_cast t1' t2' v) = v.