Proof with eauto with val_renamings.
intros; destruct v; inversion Hval_obs; subst; simpl...
Qed.

(* Specifications: *)
Lemma val_obs_longofintu:
forall f v v'
(Hobs: val_obs f v v'),
val_obs f (Val.longofintu v) (Val.longofintu v').
Lemma val_obs_floatofsingle:
forall f v v'
(Hval_obs: val_obs f v v'),
val_obs f (Val.floatofsingle v) (Val.floatofsingle v').
Lemma val_obs_intoffloat:
forall f v v'
(Hval_obs: val_obs f v v'),
val_obs f (Val.maketotal (Val.intoffloat v))
(Val.maketotal (Val.intoffloat v')).