+getPicBaseMaybeNat :: NatM (Maybe Reg)
+getPicBaseMaybeNat = NatM (\state -> (natm_pic state, state))
+
+getPicBaseNat :: MachRep -> NatM Reg
+getPicBaseNat rep = do
+ mbPicBase <- getPicBaseMaybeNat
+ case mbPicBase of
+ Just picBase -> return picBase
+ Nothing -> do
+ reg <- getNewRegNat rep
+ NatM (\state -> (reg, state { natm_pic = Just reg }))