Re: [Xen-devel] [PATCH 05/17] x86emul: add XOP decoding

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.09.16 at 18:11, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 08/09/16 14:11, Jan Beulich wrote:
>> @@ -1580,6 +1586,9 @@ struct x86_emulate_state {
>>          ext_0f   = vex_0f,
>>          ext_0f38 = vex_0f38,
>>          ext_0f3a = vex_0f3a,
>> +        ext_8f08 = 8,
>> +        ext_8f09,
>> +        ext_8f0a,
> 
> What is this = 8 for?  I presume you didn't slip it in accidentally, but
> I still can't figure out why.

So I can use the value directly from vex.opcx, without further
adjustment.

>> @@ -1848,18 +1857,30 @@ x86_decode(
>>                      rex_prefix |= REX_R;
>>  
>>                  b = insn_fetch_type(uint8_t);
>> -                switch ( ext = vex.opcx )
>> +                ext = vex.opcx;
>> +                if ( b != 0x8f )
>> +                {
>> +                    switch ( ext )
>> +                    {
>> +                    case vex_0f:
>> +                        d = twobyte_table[b];
>> +                        break;
>> +                    case vex_0f38:
>> +                        d = twobyte_table[0x38];
>> +                        break;
>> +                    case vex_0f3a:
>> +                        d = twobyte_table[0x3a];
>> +                        break;
>> +                    default:
>> +                        rc = X86EMUL_UNHANDLEABLE;
>> +                        goto done;
>> +                    }
>> +                }
>> +                else if ( ext < ext_8f08 +
>> +                                sizeof(xop_table) / sizeof(*xop_table) )
> 
> ARRAY_SIZE() ?

If we want to add another helper #define to the test code, yes. It
being a single instance, that addition didn't seem worth it to me.

Jan


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