.text
    .global sort_by_age


// r0 - N
// r1 - pointer
// r2 - i
// r3 - j
// r4 - max_i = n - 2
// r5 - max_j = n - i - 2
// r6 - shift
// r7/r8 = arr[j]/arr[j + 1]
// r9 - swap_loop

sort_by_age:
    push {r4-r9, lr}

    mov r4, r0
    sub r4, #2

    mov r2, #-1

for_i:
    add r2, #1
    cmp r2, r4
    bgt exit

    mov r5, r4
    sub r5, r2

    mov r3, #-1

for_j:
    add r3, #1
    cmp r3, r5
    bgt for_i

    mov r6, #48
    mul r6, r3
    add r6, #4
    ldr r7, [r1, r6]
    add r6, #48
    ldr r8, [r1, r6]

    cmp r7, r8
    bgt swap
    b for_j

swap:
    mov r9, #-1
    sub r6, #52

swap_loop:
    add r9, #1
    cmp r9, #12
    beq for_j

    ldr r7, [r1, r6]
    add r6, #48
    ldr r8, [r1, r6]
    str r7, [r1, r6]
    sub r6, #48
    str r8, [r1, r6]
    add r6, #4
    b swap_loop

exit:
    pop {r4-r9, lr}
    bx lr