[PATCH 2/8] Support APX GPR32 with extend evex prefix

[Jan Beulich]

On 19.10.2023 13:58, Cui, Lili wrote:
>> -----Original Message-----
>> From: Cui, Lili
>> Sent: Wednesday, October 18, 2023 7:31 PM
>>
>> OK, I'll try to add more checks, and add description for them.
>>
> 
> Added some bit checks in the decoder.
> 
> --- a/opcodes/i386-dis.c
> +++ b/opcodes/i386-dis.c
> @@ -11533,6 +11642,13 @@ OP_E_memory (instr_info *ins, int bytemode, int sizeflag)
>                 abort ();
>               if (ins->vex.evex)
>                 {
> +                 /* S/G EVEX insns require EVEX.P[10] == 1 */
> +                 if (ins->rex2 & REX_X)
> +                   {
> +                     oappend (ins, "(bad)");
> +                     return true;
> +                   }

I think I understand this, but ...

> @@ -9003,6 +9003,9 @@ get_valid_dis386 (const struct dis386 *dp, instr_info *ins)
>         case 0x4:
>           vex_table_index = EVEX_MAP4;
>           ins->evex_type = evex_from_legacy;
> +         /* EVEX from legacy instrucions require EVEX.P[2:0] must be 0x04.  */
> +         if (!((*ins->codep & 0x7) == 0x04))
> +           return  &bad_opcode;

... what's this about? Aren't you in a switch() dealing with the exact same
three bits?

> @@ -9063,6 +9066,22 @@ get_valid_dis386 (const struct dis386 *dp, instr_info *ins)
>         }
> 
>        ins->need_vex = 4;
> +
> +      /* EVEX from legacy requrie EVEX.P[17:16] must be 0, EVEX.P[23:21] must
> +        be 0.
> +        EVEX from evex requrie EVEX.P[17:16] must be 0. EVEX.P[23:22] must
> +        be 0, EVEX.P[20] must be 0.  */
> +      if (ins->evex_type == evex_from_legacy || ins->evex_type == evex_from_vex)
> +       {
> +         if (!((*ins->codep & 0x3) == 0)
> +             || !((*ins->codep >> 6 & 0x3) == 0)
> +             || (ins->evex_type == evex_from_legacy
> +                 && !((*ins->codep >> 5 & 0x1) == 0))
> +             || (ins->evex_type == evex_from_vex
> +                 && !ins->vex.b))
> +           return &bad_opcode;

I guess I'm confused here: So far we don't use EVEX.P[] as notation in
comments. Can you please use the respective field names instead? Also
can you please improve readability by converting !(a == b) into a != b?

Jan