            segment .text
            global  main
    main:
            push    rbp
            mov     rbp, rsp
            sub     rsp, 32        ; shaow register space
            mov     rax, 0x12345678; Inditial value for rax
            ror     rax, 8         ; Preserve bits 7-0
            shr     rax, 4         ; Shift out original 11-8
            shl     rax, 4         ; Bits 3-0 are 0's
            or      rax, 1010b     ; Set the field to 1010b
            rol     rax, 8         ; Bring back bits 7-0
            xor     rax, rax
            leave
            ret