Re: [RISCV] [GNU AS] Possible `vmsge{u}.vx` instruction lowering bug?

[Kiva Oyama <libkernelpanic@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1988 bytes --]

>  Is the following expected?

Yes.

> Seems "vd is any" also has the same issue.

I rechecked the spec, for every masked vmsge{u}.vx, the lowered instruction
is only masked when `vd != v0`.
So your patch does fix these two problems.

Thank you for clarifying.

Best Regards,
Kiva Oyama

On Wed, Aug 30, 2023 at 1:51 PM Jan Beulich <jbeulich@suse.com> wrote:

> On 30.08.2023 04:51, Nelson Chu wrote:
> > Hi Jan,
> > Thanks for pointing that out.
> >
> > Hi Kiva,
> > Maybe you can send a better patch for this issue if you are interested,
> > including what Jan suggested.  Thanks :-)
>
> Hmm, both of your replies above make me suspect a misunderstanding: I
> think your patch does exactly what is needed.
>
> Jan
>
> > On Tue, Aug 29, 2023 at 4:52 PM Jan Beulich <jbeulich@suse.com> wrote:
> >
> >> On 29.08.2023 09:59, Nelson Chu wrote:
> >>> Is the following expected?
> >>
> >> I think so, but Kiva - please confirm.
> >>
> >>>  Seems "vd is any" also has the same issue.
> >>
> >> Right, that's what ...
> >>
> >>>> I think this wants fixing alike in binutils: From looking at
> >>>> vector_macro(),
> >>>> it appears that emitting the masked form is merely an accident
> resulting
> >>>> from the inverted encoding of "masking". In particular, if masking was
> >>>> indeed meant, I expect code there would be
> >>>>
> >>>>                   if (vd == vm)
> >>>>                     {
> >>>>                       macro_build (NULL, "vmslt.vx", "Vd,Vt,sVm",
> vtemp,
> >>>> vs2, vs1, vm);
> >>>>                       macro_build (NULL, "vmandnot.mm", "Vd,Vt,Vs",
> vd,
> >>>> vm, vtemp);
> >>>>                     }
> >>>>                   else
> >>>>                     ...
> >>>>
> >>>> much like it is a few lines down from there. (Apparently the "else"
> path
> >>>> omitted above is similarly affected.)
> >>
> >> ... I was referring to with the parenthesized sentence.
> >>
> >> Jan
> >>
> >
>
>