## Zadanie 8.  x * y

*Argumeny:* x, y : 128b (16B) liczby całkowite **bez znaku**
    | %rdi x1 | %rsi x0 | := x
    | %rdx y1 | %rcx y0 | := y

*Wynik:* w %rax i %rdx

(x1 * 2^64 + x0) * (y1 * 2^64 + y0) =
 = x1y1 * 2^128 + (x1y0 + x0y1) * 2^64 + x0y0

```
mul128:  ; Liczymy (x1y0 + x0y1) * 2^64 + x0y0
    movq %rdx, %rax     ; rax := y1
    mulq %rsi           ; rdx|rax := y1 * x0
    movq %rax, %r8      ; r8 := x0y1 lower

    movq %rdi, %rax     ; rax := x1
    mulq %rcx           ; rdx|rax := x1 * y0
    movq %rax, %r9      ; r9 := x1y0 lower

    movq %rsi, %rax     ; rax := x0
    mulq %rcx           ; rdx|rax := x0 * y0
    movq %rax, %r10     ; r10 := x0y0 lower

    leaq (%r8,%r9),%rax ; rax := x0y1 lower + x1y0 lower
    addq %rdx, %rax     ; rax := rax + x0y0 higher

    movq %r10, %rdx
```