gistfile1.txt

; uint32_t unscramble(uint32_t)
; arg in eax, return in eax
            0000:096e      51             push cx
            0000:096f      b90800         mov cx, 8
            0000:0972      66355555aaaa   xor eax, 0xaaaa5555
        .-> 0000:0978      66d1e0         shl eax, 1
       ,==< 0000:097b      7308           jae 0x985
       |:   0000:097d      663557000080   xor eax, 0x80000057
       |:   0000:0983      0c01           or al, 1
       ``=< 0000:0985      e2f1           loop 0x978
            0000:0987      59             pop cx
            0000:0988      c3             ret

Unscramble.hs

module Unscramble where

import Data.Word
import Data.Bits

unscramble :: Word32 -> Word32
unscramble x = result where
  initial = x `xor` 0xaaaa5555
  t y = if y .&. 0x80000000 == 0
        then y `shift` 1
        else ((y `shift` 1) `xor` 0x80000057) .|. 1
  result = (iterate t initial) !! 8