anchor.diff:  %%  to safe labels (i.e., the code at those labels don't depend
   %%  on the contents of any Y register).
   
  +frame_size([{'%',_}|Is], Safe) ->
  +    frame_size(Is, Safe);
   frame_size([{block,_}|Is], Safe) ->
       frame_size(Is, Safe);
   frame_size([{call_fun,_}|Is], Safe) ->
  
positive.code: %%  This function handles the same instructions as frame_size/2. It
  %%  assumes that any labels in the instructions are safe labels.
  
  is_not_used(Y, [{apply,_}|Is]) ->
      is_not_used(Y, Is);
  is_not_used(Y, [{bif,_,{f,_},Ss,Dst}|Is]) ->
  
negative.code:     safe_labels(Is, Acc);
  safe_labels([], Acc) -> cerl_sets:from_list(Acc).
  
  is_safe_label([{'%',_}|Is]) ->
      is_safe_label(Is);
  is_safe_label([{line,_}|Is]) ->
      is_safe_label(Is);
  is_safe_label([{badmatch,{Tag,_}}|_]) ->
  