From: "H.J. Lu" <hjl.tools@gmail.com>
To: Noah Goldstein <goldstein.w.n@gmail.com>
Cc: GNU C Library <libc-alpha@sourceware.org>,
"Carlos O'Donell" <carlos@systemhalted.org>
Subject: Re: [PATCH v6 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2
Date: Fri, 1 Jul 2022 15:38:23 -0700 [thread overview]
Message-ID: <CAMe9rOqGpyR_THEcgXfaaEDE7CSh9PBqM439jCF-tsUZnSMytg@mail.gmail.com> (raw)
In-Reply-To: <CAFUsyfK_zmSzVnkgNHUH_omsmqq3_bfdOsLMrh7B7ETU1ZCMjQ@mail.gmail.com>
On Thu, Jun 30, 2022 at 5:01 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Thu, Jun 30, 2022 at 5:01 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > On Thu, Jun 30, 2022 at 4:20 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > >
> > > On Thu, Jun 30, 2022 at 1:13 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > > >
> > > > Just for clarities sake and so that if a future implementation is
> > > > added we remember to add the check.
> > > > ---
> > > > sysdeps/x86_64/multiarch/ifunc-sse4_2.h | 4 ++++
> > > > 1 file changed, 4 insertions(+)
> > > >
> > > > diff --git a/sysdeps/x86_64/multiarch/ifunc-sse4_2.h b/sysdeps/x86_64/multiarch/ifunc-sse4_2.h
> > > > index ee36525bcf..752798278c 100644
> > > > --- a/sysdeps/x86_64/multiarch/ifunc-sse4_2.h
> > > > +++ b/sysdeps/x86_64/multiarch/ifunc-sse4_2.h
> > > > @@ -27,6 +27,10 @@ IFUNC_SELECTOR (void)
> > > > {
> > > > const struct cpu_features* cpu_features = __get_cpu_features ();
> > > >
> > > > + /* This function uses slow sse4.2 instructions (pcmpstri) but since
> > > > + there is no other optimized implementation keep using it. If an
> > > > + optimized fallback is added add a X86_ISA_CPU_FEATURE_ARCH_P
> > > > + (cpu_features, Slow_SSE4_2) check. */
> > >
> > > This function always uses sse4.2 instructions (pcmpstri) since there
> > > is no other optimized implementation. If an ...
> >
> > Is it all sse4.2 instructions that count for Slow_SSE4.2 or other the
> > microcode string ones?
> other->only*
No. Only the string instructions are slow.
> > >
> > > > if (CPU_FEATURE_USABLE_P (cpu_features, SSE4_2))
> > > > return OPTIMIZE (sse42);
> > > >
> > > > --
> > > > 2.34.1
> > > >
> > >
> > >
> > > --
> > > H.J.
--
H.J.
next prev parent reply other threads:[~2022-07-01 22:39 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-28 15:27 [PATCH v1 " Noah Goldstein
2022-06-28 15:27 ` [PATCH v1 2/2] x86: Add support for building str{c|p}{brk|spn} with explicit ISA level Noah Goldstein
2022-06-29 19:20 ` H.J. Lu
2022-06-29 22:07 ` Noah Goldstein
2022-06-29 18:53 ` [PATCH v1 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 H.J. Lu
2022-06-29 19:19 ` Noah Goldstein
2022-06-29 22:06 ` Noah Goldstein
2022-06-29 22:05 ` [PATCH v2 " Noah Goldstein
2022-06-29 22:05 ` [PATCH v2 2/2] x86: Add support for building str{c|p}{brk|spn} with explicit ISA level Noah Goldstein
2022-06-29 22:15 ` H.J. Lu
2022-06-30 3:11 ` Noah Goldstein
2022-06-30 3:27 ` Noah Goldstein
2022-06-29 22:12 ` [PATCH v2 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 H.J. Lu
2022-06-30 3:09 ` Noah Goldstein
2022-06-30 3:08 ` [PATCH v4 1/2] x86: Add missing IS_IN (libc) check to strncmp-sse4_2.S Noah Goldstein
2022-06-30 3:08 ` [PATCH v4 2/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 Noah Goldstein
2022-06-30 3:10 ` [PATCH v4 1/2] x86: Add missing IS_IN (libc) check to strncmp-sse4_2.S Noah Goldstein
2022-06-30 3:10 ` [PATCH v5 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 Noah Goldstein
2022-06-30 3:10 ` [PATCH v5 2/2] x86: Add support for building str{c|p}{brk|spn} with explicit ISA level Noah Goldstein
2022-06-30 3:44 ` [PATCH v6 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 Noah Goldstein
2022-06-30 3:44 ` [PATCH v6 2/2] x86: Add support for building str{c|p}{brk|spn} with explicit ISA level Noah Goldstein
2022-06-30 7:47 ` [PATCH v6 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 Andreas Schwab
2022-06-30 20:13 ` Noah Goldstein
2022-06-30 20:13 ` Noah Goldstein
2022-06-30 20:13 ` [PATCH v6 2/2] x86: Add support for building str{c|p}{brk|spn} with explicit ISA level Noah Goldstein
2022-07-01 22:35 ` H.J. Lu
2022-06-30 23:20 ` [PATCH v6 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 H.J. Lu
2022-07-01 0:01 ` Noah Goldstein
2022-07-01 0:01 ` Noah Goldstein
2022-07-01 22:38 ` H.J. Lu [this message]
2022-07-01 22:52 ` Noah Goldstein
2022-07-03 18:00 ` H.J. Lu
2022-07-04 4:28 ` Noah Goldstein
2022-07-04 4:28 ` [PATCH v7 " Noah Goldstein
2022-07-04 4:28 ` [PATCH v7 2/2] x86: Add support for building str{c|p}{brk|spn} with explicit ISA level Noah Goldstein
2022-07-05 15:41 ` [PATCH v7 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2 H.J. Lu
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