Re: [PATCH v2 0/1] MR4720: Implement test_continue() for amd64

[Jinoh Kang (＠iamahuman)]

Jinoh Kang (@iamahuman) commented about dlls/ntdll/tests/exception.c:
> -
>    0x48, 0x8b, 0x4c, 0x24, 0x08, /* mov rcx, [rsp+8*1]; context */
> -
>    0x48, 0x8b, 0x54, 0x24, 0x10, /* mov rdx, [rsp+8*2]; arg2 */
> -
>    0x48, 0x83, 0xec, 0x70,       /* sub rsp, 0x70; change stack */
> -
> -
>    /* setup context to return to label 1 */
> -
>    0x48, 0x8d, 0x05, 0x1b, 0x00, 0x00, 0x00, /* lea rax, [rel 1] (0x1b) */
> -
>    0x48, 0x89, 0x81, 0xf8, 0x00, 0x00, 0x00, /* mov [rcx + 0xf8 (context.Rip)], rax */
> -
> -
>    /* trash EFLAGS */
> -
>    0x9c,                               /* pushfq   */
> -
>    0x58,                               /* pop rax  */
> -
>    0x48, 0x0d, 0x00, 0x45, 0x00, 0x00, /* or rax, 0x0100 + 0x4400; set trap flag so it's cleared.
> -
>                                           FIXME: also clearing Direction Flag and Nested Task as those break Wine */
> -
> -
>    0x48, 0xf7, 0xd0,                   /* not rax  */
> -
>    0x50,                               /* push rax */

Avoid changing unrelated flags. Reserved flag bits may obtain a meaning in the future and break tests.

```suggestion:-3+0
        0x48, 0x81, 0x34, 0x24, 0xd5, 0x08, /* xorq $0x8d5,(%rsp) */
        0x00, 0x00,
```

Use xorq (QWORD PTR) instead of xorw (WORD PTR) to keep it straightforward and avoid potential store-to-load forwarding issues.