Re: [PATCH v2] x86: Remove SSSE3 instruction for broadcast in memset.S (SSE2 Only)

[Sunil Pandey <skpgkp2@gmail.com>]

On Mon, Feb 7, 2022 at 12:56 PM Noah Goldstein via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On Mon, Feb 7, 2022 at 1:49 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Mon, Feb 7, 2022 at 11:39 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > >
> > > commit b62ace2740a106222e124cc86956448fa07abf4d
> > > Author: Noah Goldstein <goldstein.w.n@gmail.com>
> > > Date:   Sun Feb 6 00:54:18 2022 -0600
> > >
> > >     x86: Improve vec generation in memset-vec-unaligned-erms.S
> > >
> > > Revert usage of 'pshufb' in broadcast logic as it is an SSSE3
> > > instruction and memset.S is restricted to only SSE2 instructions.
> > > ---
> > >  sysdeps/x86_64/memset.S | 7 ++++---
> > >  1 file changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/sysdeps/x86_64/memset.S b/sysdeps/x86_64/memset.S
> > > index ccf036be53..3f0517bbfc 100644
> > > --- a/sysdeps/x86_64/memset.S
> > > +++ b/sysdeps/x86_64/memset.S
> > > @@ -30,9 +30,10 @@
> > >
> > >  # define MEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > >    movd d, %xmm0; \
> > > -  pxor %xmm1, %xmm1; \
> > > -  pshufb %xmm1, %xmm0; \
> > > -  movq r, %rax
> > > +  movq r, %rax; \
> > > +  punpcklbw %xmm0, %xmm0; \
> > > +  punpcklwd %xmm0, %xmm0; \
> > > +  pshufd $0, %xmm0, %xmm0
> > >
> > >  # define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
> > >    movd d, %xmm0; \
> > > --
> > > 2.25.1
> > >
> >
> > LGTM.
> >
> > Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
> >
> > Thanks.
>
> Thanks pushed.
> >
> > --
> > H.J.

I would like to backport this patch to release branches.
Any comments or objections?

--Sunil