anchor.diff:      St0 = #live{lbl=D,res=gb_trees:empty()},
       case check_liveness_at(R, Lbl, St0) of
   	{killed,_} -> true;
  +	{exit_not_used,_} -> true;
   	{_,_} -> false
       end.
   
  
positive.code: 		false ->
  		    if
  			R =:= Dst -> {killed,St};
  			true -> check_liveness(R, Is, St)
  		    end
  	    end
      end;
  
negative.code: 		{killed,St} ->
  		    case member(R, Ds) of
  			true -> {killed,St};
  			false -> check_liveness_block(R, Is, St)
  		    end;
  		{exit_not_used,St} ->
  		    case member(R, Ds) of
  			true -> {exit_not_used,St};
  			false -> check_liveness_block(R, Is, St)
  		    end;
  		{not_used,St} ->
  