> > Complementing a bit without affecting W requires
> >lengthy goto instructions.
>
> Not true!  As a final thought on this neverending subject, consider:
>         bcf     tmp,0           ;Use value of 0
>         skpc                    ;if carry is 1
>         bsf     tmp,0           ;if carry 0, use 1.
>         rrf     tmp,f           ;New bit to carry bit.
> This does require a temporary register, but not W.  It doesn't affect any
> status bits except carry.  It can be made conditional by skipping the rrf
> conditionally.

If you add an "rlf tmp,f" to the beginning of that, then "tmp" will be
unaffected (though making it conditional will be a little harder).