Re: [Xen-devel] [PATCH] x86: use gcc6'es flags asm() output support

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.08.16 at 11:15, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 02/08/16 07:09, Jan Beulich wrote:
>>>>> On 01.08.16 at 19:11, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> On 01/08/16 17:06, Jan Beulich wrote:
>>>>>>> On 01.07.16 at 18:51, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>>> How about a different example, from the second hunk
>>>>>
>>>>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>>>>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>>>>> @@ -832,8 +832,19 @@ static int read_ulong(
>>>>>  static bool_t mul_dbl(unsigned long m[2])
>>>>>  {
>>>>>      bool_t rc;
>>>>> -    asm ( "mul %1; seto %2"
>>>>> -          : "+a" (m[0]), "+d" (m[1]), "=qm" (rc) );
>>>>> +
>>>>> +    asm ( "mul %1;"
>>>>> +#ifndef __GCC_ASM_FLAG_OUTPUTS__
>>>>> +          "seto %[rc];"
>>>>> +#endif
>>>>> +          : "+a" (m[0]), "+d" (m[1]),
>>>>> +#ifdef __GCC_ASM_FLAG_OUTPUTS__
>>>>> +            [rc] "=@cco" (rc)
>>>>> +#else
>>>>> +            [rc] "=qm" (rc)
>>>>> +#endif
>>>>> +        );
>>>>> +
>>>>>      return rc;
>>>>>  }
>>>> Looking at this again I think I really like the original, submitted version
>>>> better. Are you strongly biased towards the above form?
>>> I am not overly fussed between this version and the original submission.
>>>
>>> However, I definitely think that we shouldn't hide semantic bits of the
>>> ASM statement behind macros.
>> Well, the originally submitted variant doesn't do anything like that,
>> so may I translate the above to an ack?
> 
> You do already have a Rev-by from my first reply.

Oops, indeed. I'm sorry for the noise then.

Jan


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