(** 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 get_extcall_arg_inj : forall f rs rs' m m' l v, regset_ren f rs rs' -> mem_obs_eq f m m' -> get_extcall_arg rs m l = Some v -> exists v', get_extcall_arg rs' m' l = Some v' /\ val_obs f v v'.