anchor.diff:  %%  The state (constructed by index_instructions/1) is used to allow us
   %%  to determine the kill state across branches.
   
  +-spec is_killed(beam_asm:reg(), [instruction()], code_index()) -> boolean().
  +
   is_killed(R, Is, D) ->
       St = #live{lbl=D,res=gb_trees:empty()},
       case check_liveness(R, Is, St) of
  
positive.code: %%  whose destination is a register that will not be used.
  %%  Also insert {'%live',Live,Regs} annotations at the beginning
  %%  and end of each block.
  %%
  live_opt(Is0) ->
      {[{label,Fail}|_]=Bef,[Fi|Is]} =
  	splitwith(fun({func_info,_,_,_}) -> false;
  
negative.code: 
  %% split_even/1
  %% [1,2,3,4,5,6] -> {[1,3,5],[2,4,6]}
  
  -spec split_even(list()) -> {list(),list()}.
  
  split_even(Rs) -> split_even(Rs, [], []).
  
  