(** Injections on registers *)

  Definition reg_ren f (r:PregEq.t) (rs rs' : regset) : Prop :=
    val_obs f (Pregmap.get r rs) (Pregmap.get r rs').Definition regset_ren f rs rs' : Prop :=
    forall r, reg_ren f r rs rs'.Definition core_inj f c c' :=
    match c, c' with State rs _, State rs' _ => regset_ren f rs rs' end.

Lemma extcall_arg_reg: forall f rs rs' m m' locs arg (Hrs_ren: regset_ren f rs rs') (Hobs_eq: mem_obs_eq f m m') (Harg: extcall_arg rs m locs arg), exists arg', extcall_arg rs' m' locs arg' /\ val_obs f arg arg'.