Proof with eauto with wd.
intros.
induction regs as [|r regs]; simpl; auto.
intros r'.
rewrite undef_regs_comm;
rewrite Pregmap.gsspec;
unfold Pregmap.get;
destruct (Pregmap.elt_eq r' r); simpl...
Qed.
Hint Extern 0 (valid_val _ (undef_regs _ _ # _ <- _ _)) => eapply regset_wd_set : wd.
Hint Resolve regset_wd_domain
valid_val_list_incr valid_val_domain
valid_val_list_domain regset_wd_undef : wd.

(* Specifications: *)
Lemma valid_symb:
forall f fg g id i
(Hge_wd: ge_wd fg g)
(Hincr: ren_domain_incr fg f),
valid_val f (symbol_address g id i).