GCD

    AREA gcd,code,readonly
    ENTRY
main
    push {r4-r6, lr}
    mov r4, #10
    mov r5, #15

gcd_loop
    cmp r4, r5
    beq done
    cmp r4, r5
    blt swap
    mov r6, r4
    mov r4, r5
    mov r5, r6
swap
    sub r5, r5, r4
    b gcd_loop

done
    mov r0, r4
    pop {r4-r6, pc}

    END