RE: [PATCH 5/8] Support APX NDD

["Cui, Lili" <lili.cui@intel.com>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Sent: Wednesday, November 22, 2023 4:48 PM
> To: Cui, Lili <lili.cui@intel.com>
> Cc: Lu, Hongjiu <hongjiu.lu@intel.com>; ccoutant@gmail.com;
> binutils@sourceware.org; Kong, Lingling <lingling.kong@intel.com>
> Subject: Re: [PATCH 5/8] Support APX NDD
> 
> On 22.11.2023 08:46, Cui, Lili wrote:
> >>>>> @@ -9087,7 +9104,7 @@ get_valid_dis386 (const struct dis386 *dp,
> >>>> instr_info *ins)
> >>>>>  	return &err_opcode;
> >>>>>
> >>>>>        /* Set vector length.  */
> >>>>> -      if (ins->modrm.mod == 3 && ins->vex.b)
> >>>>> +      if (ins->modrm.mod == 3 && ins->vex.b && ins->evex_type ==
> >>>>> + evex_default)
> >>>>>  	ins->vex.length = 512;
> >>>>>        else
> >>>>>  	{
> >>>>
> >>>> Is this change really needed for anything?
> >>>
> >>> If it's NDD and ins->vex.b ==1, we need to avoid giving NDD a wrong
> value.
> >>
> >> But this is recording ->vex.length, not anything NDD related (afaics).
> >
> > There are some instructions that use OP_VEX, which will use ->vex.length.
> >
> > For example:
> > "addB",             { VexGb, Eb, Gb }
> 
> But that's a GPR, for which ->vex.length is not supposed to have an effect.
> 

For EVEX-promoted instructions,  evex.ll == 0b00, which has the same encoding as vex.length == 128 and they can share the same processing with ->vex.length, ->vex.length also handles GPR in OP_VEX.


  switch (ins->vex.length)
    {
    case 128:
      switch (bytemode)
        {
        case x_mode:
          names = att_names_xmm;
          ins->evex_used |= EVEX_len_used;
          break;
        case v_mode:
        case dq_mode:
          if (ins->rex & REX_W)
            names = att_names64;
          else if (bytemode == v_mode
                   && !(sizeflag & DFLAG))
            names = att_names16;
          else
            names = att_names32;
          break;
        case b_mode:
          names = att_names8rex;
          break;
        case q_mode:
          names = att_names64;
          break;
        case mask_bd_mode:
        case mask_mode:
          if (reg > 0x7)
            {
              oappend (ins, "(bad)");
              return true;
            }
          names = att_names_mask;
          break;
        default:
          abort ();
          return true;
        }
      break;

Thanks,
Lili.