From: "H.J. Lu" <hjl.tools@gmail.com>
To: Noah Goldstein <goldstein.w.n@gmail.com>
Cc: Sunil Pandey <skpgkp2@gmail.com>, libc-alpha@sourceware.org
Subject: Re: [PATCH] x86_64: Exclude SSE, AVX and FMA4 variants in libm multiarch
Date: Tue, 20 Feb 2024 10:04:48 -0800 [thread overview]
Message-ID: <CAMe9rOrNQUXDfbFADYc7GtbBx1Fpnr6yy8jvSm07ZTwXVRd2rw@mail.gmail.com> (raw)
In-Reply-To: <CAFUsyfL6aCKsLNhyMM6eYebLVRBxx5ivy+dT47K9yjNBGEv-og@mail.gmail.com>
On Tue, Feb 20, 2024 at 9:56 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Tue, Feb 20, 2024 at 5:51 PM Sunil Pandey <skpgkp2@gmail.com> wrote:
> >
> >
> >
> > On Tue, Feb 20, 2024 at 9:34 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >>
> >> On Tue, Feb 20, 2024 at 4:58 PM Sunil K Pandey <skpgkp2@gmail.com> wrote:
> >> >
> >> > When glibc is built with FMA and AVX2 enabled by default, the resulting
> >> > glibc binaries won't run on SSE or FMA4 processors. Exclude SSE, AVX and
> >> > FMA4 variants in libm multiarch when both FMA and AVX2 are enabled by
> >> > default. Disallow glibc build with only AVX2 or FMA enabled as all AVX2
> >> > processors, including VMs, should also support FMA and vice versa.
> >> >
> >> > When glibc is built with SSE4.1 enabled by default, only keep SSE4.1
> >> > variant.
> >> Not avx2 + FMA as well?
> >
> >
> > Correct. Logic is as follows
> > If (build with AVX2+FMA): Keep AVX2+FMA variants only.
> > else if (build with SSE4.1): Keep SSE4.1 variants only.
> What if someone builds with sse4.1 as a minimum but then
> runs on avx2+ machines?
Only SSE4.1 variant will be used in this case. Both SSE4.1
and AVX versions only have a single instruction. This matches
the compiler builtin function of SS4.1 and AVX.
--
H.J.
next prev parent reply other threads:[~2024-02-20 18:05 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-20 16:58 Sunil K Pandey
2024-02-20 17:33 ` Noah Goldstein
2024-02-20 17:51 ` Sunil Pandey
2024-02-20 17:56 ` Noah Goldstein
2024-02-20 18:04 ` H.J. Lu [this message]
2024-02-20 18:07 ` Noah Goldstein
2024-02-20 18:13 ` H.J. Lu
2024-02-20 18:19 ` Noah Goldstein
2024-02-20 18:27 ` H.J. Lu
2024-02-20 18:32 ` Noah Goldstein
2024-02-20 18:36 ` H.J. Lu
2024-02-20 18:38 ` Noah Goldstein
2024-02-20 18:48 ` Adhemerval Zanella Netto
2024-02-20 18:54 ` H.J. Lu
2024-02-20 19:02 ` Adhemerval Zanella Netto
2024-02-20 19:10 ` H.J. Lu
2024-02-20 19:56 ` Adhemerval Zanella Netto
2024-02-20 20:03 ` Adhemerval Zanella Netto
2024-02-20 20:18 ` Noah Goldstein
2024-02-20 20:27 ` H.J. Lu
2024-02-24 2:35 ` [PATCH v2] " Sunil K Pandey
2024-02-24 14:30 ` H.J. Lu
2024-02-24 14:55 ` H.J. Lu
2024-02-24 16:23 ` H.J. Lu
2024-02-24 16:27 ` H.J. Lu
2024-02-24 22:23 ` Sunil Pandey
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