anchor.diff:      end;
   backward([{jump,{f,To}}=J|[{bif,Op,{f,BifFail},Ops,Reg}|Is]=Is0], D, Acc) ->
       try replace_comp_op(To, Reg, Op, Ops, D) of
  -	I -> backward(Is, D, I++Acc)
  +	{Test,Jump} ->
  +            backward([Jump,Test|Is], D, Acc)
       catch
   	throw:not_possible ->
   	    case To =:= BifFail of
  
positive.code: replace_comp_op(To, Reg, Op, Ops, D) ->
      False = comp_op_find_shortcut(To, Reg, {atom,false}, D),
      True = comp_op_find_shortcut(To, Reg, {atom,true}, D),
      [bif_to_test(Op, Ops, False),{jump,{f,True}}].
  
  comp_op_find_shortcut(To0, Reg, Val, D) ->
      case shortcut_select_label(To0, Reg, Val, D) of
  
negative.code: %%   F1:  is_eq_exact F2 Reg Lit2          F1: is_eq_exact F2 Reg Lit2
  %%   L2:  ....				   L2:
  %%
  combine_eqs(To, [Reg,{Type,_}=Lit1]=Ops, D, Acc)
      when Type =:= atom; Type =:= integer ->
      Next = case Acc of
                 [{label,Lbl}|_] -> Lbl;
                 [{jump,{f,Lbl}}|_] -> Lbl
             end,
      case beam_utils:code_at(To, D) of
  	[{test,is_eq_exact,{f,F2},[Reg,{Type,_}=Lit2]},
  	 {label,L2}|_] when Lit1 =/= Lit2 ->
  	    {select,select_val,Reg,{f,F2},[Lit1,{f,Next},Lit2,{f,L2}]};
  	[{test,is_eq_exact,{f,F2},[Reg,{Type,_}=Lit2]},
  	 {jump,{f,L2}}|_] when Lit1 =/= Lit2 ->
  	    {select,select_val,Reg,{f,F2},[Lit1,{f,Next},Lit2,{f,L2}]};
  	[{select,select_val,Reg,{f,F2},[{Type,_}|_]=List0}|_] ->
  	    List = remove_from_list(Lit1, List0),
  	    {select,select_val,Reg,{f,F2},[Lit1,{f,Next}|List]};
  	_Is ->
  	    {test,is_eq_exact,{f,To},Ops}
  	end;
  