anchor.diff:                               match attrs, cfg.steps.unfold_attr with
                                | None, Some _ -> false
                                | Some ats, Some ats' -> BU.for_some (fun at -> BU.for_some (attr_eq at) ats') ats
  -                             | _, _ -> false))
  +                             | _, _ -> false)))
                    in
                    log cfg (fun () -> BU.print3 ">>> For %s (%s), should_delta = %s\n"
                                    (Print.term_to_string t)
  
positive.code: 
      // GM: This is basically saying "if exclude iota, don't memoize".
      // what's up with that?
      if not cfg.steps.iota
      then if cfg.steps.hnf
           then let arg = closure_as_term cfg env_arg tm in
  
negative.code:                          | Eager_unfolding_only -> true
                           | Unfold l -> Common.delta_depth_greater_than fv.fv_delta l)
                   in
                   let should_delta = should_delta && (
                            let attrs = Env.attrs_of_qninfo qninfo in
                             // never unfold something marked tac_opaque when reducing tactics
                            (not cfg.steps.unfold_tac ||
                             not (cases (BU.for_some (attr_eq U.tac_opaque_attr)) false attrs)) &&
  