anchor.diff:           fold_instrs_rpo/4,
            linearize/1,
            mapfold_instrs_rpo/4,
  +         normalize/1,
            predecessors/1,
            rename_vars/3,
            rpo/1,rpo/2,
  
positive.code: %%% Internal functions.
  %%%
  
  def_used_1([#b_blk{is=Is,last=Last}|Bs], Preds, Def0, Used0) ->
      {Def,Used1} = def_used_is(Is, Preds, Def0, Used0),
      Used = gb_sets:union(gb_sets:from_list(used(Last)), Used1),
  
negative.code: -type cg_prim_op() :: 'bs_get' | 'bs_match_string' | 'bs_restore' | 'bs_skip' |
  'copy' | 'put_tuple_arity' | 'put_tuple_element'.
  
  -import(lists, [foldl/3,keyfind/3,mapfoldl/3,reverse/1]).
  
  -spec add_anno(Key, Value, Construct) -> Construct when
        Key :: atom(),
  