Re: [Xen-devel] [PATCH 2/2] x86emul: simplify asm() constraints

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.03.15 at 11:42, <tim@xxxxxxx> wrote:
> At 16:36 +0000 on 10 Mar (1426001780), Jan Beulich wrote:
>> @@ -806,9 +802,9 @@ static int read_ulong(
>>  static bool_t mul_dbl(unsigned long m[2])
>>  {
>>      bool_t rc;
>> -    asm ( "mul %4; seto %b2"
>> -          : "=a" (m[0]), "=d" (m[1]), "=q" (rc)
>> -          : "0" (m[0]), "1" (m[1]), "2" (0) );
>> +    asm ( "mul %1; seto %b2"
>> +          : "+a" (m[0]), "+d" (m[1]), "=q" (rc)
>> +          : "2" (0) );
> 
> Would 'bool_t rc = 0' allow you to switch operand 2 to +q and drop the
> last input operand as well?

Yes.

>  Or did that also produce worse code?

I didn't try yet, but I can't see why it would.

Jan


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