RE: [PATCH] x86: simplify VexVVVV_SRC2 handling for the XOP case

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

> As already suggested during review, rather than having an extra conditional in
> build_modrm_byte() (a code path used for quite a few more insns, including
> even certain GPR ones), adjust the attribute in the installed template to
> properly describe things with operands swapped.

Agreed, putting special handlings together makes it easier to understand.

> ---
> I think we could even omit the conditional in match_template(), as all other
> insns where XOP.W / VEX.W controls operand order are Src1VVVV anyway.
> Opinions?
> 

Yes, since we change i.tm.opcode_modifier.vexw, i.tm.opcode_modifier.vexvvvv should also be changed together without any conditions.

Lili.
> --- a/gas/config/tc-i386.c
> +++ b/gas/config/tc-i386.c
> @@ -9255,6 +9255,10 @@ match_template (char mnem_suffix)
>  	 flipping VEX.W.  */
>        i.tm.opcode_modifier.vexw ^= VEXW0 ^ VEXW1;
> 
> +      /* In 3-operand insns XOP.W changes which operand goes into XOP.vvvv.
> */
> +      if (i.tm.opcode_modifier.vexvvvv == VexVVVV_SRC2)
> +	i.tm.opcode_modifier.vexvvvv = VexVVVV_SRC1;
> +
>      swap_first_2:
>        j = i.tm.operand_types[0].bitfield.imm8;
>        i.tm.operand_types[j] = operand_types[j + 1]; @@ -10441,15 +10445,8
> @@ build_modrm_byte (void)
>      {
>      /* VEX.vvvv encodes the last source register operand.  */
>      case VexVVVV_SRC2:
> -      if (source != op)
> -	{
> -	  v = source++;
> -	  break;
> -	}
> -      /* For vprot*, vpshl*, and vpsha*, XOP.W controls the swapping of src1
> -	 and src2, and it requires fall through when the operands are swapped.
> -       */
> -      /* Fall through.  */
> +      v = source++;
> +      break;
>      /* VEX.vvvv encodes the first source register operand.  */
>      case VexVVVV_SRC1:
>        v =  dest - 1;