Hint Rewrite sem_cast_neutral_int using
(auto;
match goal with H: is_int ?i ?s ?v |- isVint ?v => apply (is_int_is_Vint i s v H) end) : norm.

Lemma eval_expr_binop: forall {cs: compspecs}  op a1 a2 t, eval_expr (Ebinop op a1 a2 t) =
`(eval_binop op (typeof a1) (typeof a2)) (eval_expr a1) (eval_expr a2).