From: Noah Goldstein <goldstein.w.n@gmail.com>
To: libc-alpha@sourceware.org
Subject: [PATCH v7 1/2] x86: Add comment explaining no Slow_SSE4_2 check in ifunc-sse4_2
Date: Sun, 3 Jul 2022 21:28:06 -0700 [thread overview]
Message-ID: <20220704042807.3863553-1-goldstein.w.n@gmail.com> (raw)
In-Reply-To: <20220628152717.17838-1-goldstein.w.n@gmail.com>
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 | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/sysdeps/x86_64/multiarch/ifunc-sse4_2.h b/sysdeps/x86_64/multiarch/ifunc-sse4_2.h
index ee36525bcf..f8b56936ec 100644
--- a/sysdeps/x86_64/multiarch/ifunc-sse4_2.h
+++ b/sysdeps/x86_64/multiarch/ifunc-sse4_2.h
@@ -27,6 +27,12 @@ IFUNC_SELECTOR (void)
{
const struct cpu_features* cpu_features = __get_cpu_features ();
+ /* This function uses the `pcmpstri` sse4.2 instruction which can be
+ slow on some CPUs. This normally would be guarded by a
+ Slow_SSE4_2 check, but since there is no other optimized
+ implementation its best to keep it regardless. If an optimized
+ fallback is added add a X86_ISA_CPU_FEATURE_ARCH_P (cpu_features,
+ Slow_SSE4_2) check. */
if (CPU_FEATURE_USABLE_P (cpu_features, SSE4_2))
return OPTIMIZE (sse42);
--
2.34.1
next prev parent reply other threads:[~2022-07-04 4:28 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
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 ` Noah Goldstein [this message]
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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