Re: [PATCH V5 8/9] Support APX NDD optimized encoding.

[Jan Beulich <jbeulich@suse.com>]

On 28.12.2023 02:27, Cui, Lili wrote:
> @@ -7754,6 +7804,60 @@ match_template (char mnem_suffix)
>  	  i.memshift = memshift;
>  	}
>  
> +      /* If we can optimize a NDD insn to legacy insn, like
> +	 add %r16, %r8, %r8 -> add %r16, %r8,
> +	 add  %r8, %r16, %r8 -> add %r16, %r8, then rematch template.
> +	 Note that the semantics have not been changed.  */
> +      if (optimize
> +	  && !i.no_optimize
> +	  && i.vec_encoding != vex_encoding_evex
> +	  && t + 1 < current_templates.end
> +	  && !t[1].opcode_modifier.evex
> +	  && t[1].opcode_space <= SPACE_0F38
> +	  && t->opcode_modifier.vexvvvv == VexVVVV_DST
> +	  && (i.types[i.operands - 1].bitfield.dword
> +	      || i.types[i.operands - 1].bitfield.qword))

While you check the last operand's type here, ...

> +	{
> +	  unsigned int match_dest_op = can_convert_NDD_to_legacy (t);
> +
> +	  if (match_dest_op != (unsigned int) ~0)
> +	    {
> +	      size_match = true;
> +	      /* We ensure that the next template has the same input
> +		 operands as the original matching template by the first
> +		 opernd (ATT). To avoid someone support new NDD insns and
> +		 put it in the wrong position.  */
> +	      overlap0 = operand_type_and (i.types[0],
> +					   t[1].operand_types[0]);
> +	      if (t->opcode_modifier.d)
> +		overlap1 = operand_type_and (i.types[0],
> +					     t[1].operand_types[1]);
> +	      if (!operand_type_match (overlap0, i.types[0])
> +		  && (!t->opcode_modifier.d
> +		      || !operand_type_match (overlap1, i.types[0])))
> +		size_match = false;

.. why is it the first one's here? That may be a memory operand, which
in AT&T mode cannot possibly have a size.

Jan