There is a clever algorithm for bit reversal "discovered" at MIT (I
think) a long time ago.  Do:

        mult a,#100040020001            ;Make some copies
        and a, #210210210010            ; select some bits
        div a, #377                     ; cast out / squeeze...

All the numbers are octal.  The words are 36 bits long and the initial
multiply is allowed to get an arithmatic overflow.
Three instuctions. Five words (36 bits each).  Totally inapplicable to
the PIC, but pretty weird...

BillW