Ltac destruct_eqb_type := 
match goal with H: context [eqb_type ?t1 ?t2] |- _ =>
 let J := fresh "J" in 
  destruct (eqb_type t1 t2) eqn:?J;
 [apply eqb_type_true in J | apply eqb_type_false in J]
end.

Lemma classify_cast_eq: forall t1 t2, t1 <> int_or_ptr_type -> t2 <> int_or_ptr_type -> classify_cast t1 t2 = Cop.classify_cast t1 t2.