Proof with eauto with val_renamings.
intros.
destruct v1, v1'; inversion Hval_obs;
inversion Hval_obs'; subst; simpl; eauto with val_renamings.
Qed.

(* Specifications: *)
(** Floating point functions *)
Lemma val_obs_addf:
forall f v1 v2 v1' v2'
(Hval_obs': val_obs f v1' v2')
(Hval_obs: val_obs f v1 v2),
val_obs f (Val.addf v1 v1') (Val.addf v2 v2').