anchor.diff:                      I = I0#b_set{op=has_map_field,dst=SuccDst},
                       live_opt_is([I|Is], Live0, Acc);
                   _ ->
  -                    Live1 = gb_sets:delete(SuccDst, Live0),
  -                    Live = gb_sets:add(Dst, Live1),
  +                    Live1 = cerl_sets:del_element(SuccDst, Live0),
  +                    Live = cerl_sets:add_element(Dst, Live1),
                       live_opt_is([I0|Is], Live, [SuccI|Acc])
               end;
           {false, true} ->
  
positive.code: live_opt_is([#b_set{op={succeeded,guard},dst=SuccDst,args=[Dst]}=SuccI,
               #b_set{op=Op,dst=Dst}=I0|Is],
              Live0, Acc) ->
      case {gb_sets:is_member(SuccDst, Live0),
            gb_sets:is_member(Dst, Live0)} of
          {true, true} ->
              Live = gb_sets:delete(SuccDst, Live0),
              live_opt_is([I0|Is], Live, [SuccI|Acc]);
          {true, false} ->
              %% The result of the instruction before {succeeded,guard} is
  
negative.code: live_opt([{L,Blk0}|Bs], LiveMap0, Blocks) ->
      Blk1 = beam_ssa_share:block(Blk0, Blocks),
      Successors = beam_ssa:successors(Blk1),
      Live0 = live_opt_succ(Successors, L, LiveMap0, cerl_sets:new()),
      {Blk,Live} = live_opt_blk(Blk1, Live0),
      LiveMap = live_opt_phis(Blk#b_blk.is, L, Live, LiveMap0),
      live_opt(Bs, LiveMap, Blocks#{L:=Blk});
  live_opt([], _, Acc) -> Acc.
  
  live_opt_succ([S|Ss], L, LiveMap, Live0) ->
      case LiveMap of
          #{{S,L}:=Live} ->
              %% The successor has a phi node, and the value for
              %% this block in the phi node is a variable.
              live_opt_succ(Ss, L, LiveMap, cerl_sets:union(Live0, Live));
          #{S:=Live} ->
              %% No phi node in the successor, or the value for
              %% this block in the phi node is a literal.
              live_opt_succ(Ss, L, LiveMap, cerl_sets:union(Live0, Live));
          #{} ->
              %% A peek_message block which has not been processed yet.
              live_opt_succ(Ss, L, LiveMap, Live0)
  