Ltac wlt_ind :=
  match goal with
  | [ |- forall (n: word ?len), ?P ] =>
    refine (well_founded_ind (@wlt_wf len) (fun n => P) _)
  end.

Lemma wmsb_split2: forall sz (w: word (sz + 1)) b, wmsb w b = if weq (split2 _ 1 w) (natToWord _ 0) then false else true.