Proof with eauto with val_renamings.
intros.
destruct v1, v1'; inversion Hval_obs;
inversion Hval_obs'; subst;
solve [simpl; eauto with val_renamings ||
destruct Archi.ptr64; simpl; eauto with val_renamings].
Qed.

Lemma val_obs_addl:
forall f v1 v2 v1' v2'
(Hval_obs': val_obs f v1' v2')
(Hval_obs: val_obs f v1 v2),
val_obs f (Val.addl v1 v1') (Val.addl v2 v2').