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_Etempvar: forall {cs: compspecs} i t, eval_expr (Etempvar i t) = eval_id i.