Re: [PATCH] x86: correct and improve "*vec_dupv2di"

[Jan Beulich <jbeulich@suse.com>]

On 15.06.2023 09:45, Hongtao Liu wrote:
> On Thu, Jun 15, 2023 at 3:07 PM Uros Bizjak via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>> On Thu, Jun 15, 2023 at 8:03 AM Jan Beulich via Gcc-patches
>> <gcc-patches@gcc.gnu.org> wrote:
>>> +    case 3:
>>> +      return "%vmovddup\t{%1, %0|%0, %1}";
>>> +    case 4:
>>> +      return "movlhps\t%0, %0";
>>> +    default:
>>> +      gcc_unreachable ();
>>> +    }
>>> +}
>>> +  [(set_attr "isa" "sse2_noavx,avx,avx512f,sse3,noavx")
>>> +   (set_attr "type" "sselog1,sselog1,ssemov,sselog1,ssemov")
>>> +   (set_attr "prefix" "orig,maybe_evex,evex,maybe_vex,orig")
>>> +   (set_attr "mode" "TI,TI,TI,DF,V4SF")
> alternative 2 should be XImode when !TARGET_AVX512VL.

This gives me a chance to actually raise a related question I stumbled
across several times: Which operand does the mode attribute actually
describe? I've seen places where it's the source, but I've also seen
places where it's the destination. Because of this mix I wasn't really
sure that getting this attribute entirely correct is actually
necessary, and hence I hoped it would be okay to not further complicate
the attribute here.

Jan