From: Aurelien Jarno <aurelien@aurel32.net>
To: libc-stable@sourceware.org
Cc: Aurelien Jarno <aurelien@aurel32.net>,
Noah Goldstein <goldstein.w.n@gmail.com>
Subject: [COMMITTED 2.33 3/8] x86-64: Require BMI2 for AVX2 strcmp implementation
Date: Tue, 4 Oct 2022 00:04:43 +0200 [thread overview]
Message-ID: <20221003220448.3298308-3-aurelien@aurel32.net> (raw)
In-Reply-To: <20221003220448.3298308-1-aurelien@aurel32.net>
The AVX2 strcmp implementation uses the 'bzhi' instruction, which
belongs to the BMI2 CPU feature.
NB: It also uses the 'tzcnt' BMI1 instruction, but it is executed as BSF
as BSF if the CPU doesn't support TZCNT, and produces the same result
for non-zero input.
Partially fixes: b77b06e0e296 ("x86: Optimize strcmp-avx2.S")
Partially resolves: BZ #29611
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
(cherry picked from commit 4d64c6445735e9b34e2ac8e369312cbfc2f88e17)
---
sysdeps/x86_64/multiarch/ifunc-impl-list.c | 4 +++-
sysdeps/x86_64/multiarch/strcmp.c | 4 ++--
2 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
index ca64b34c14..70931f1598 100644
--- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
@@ -503,10 +503,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
/* Support sysdeps/x86_64/multiarch/strcmp.c. */
IFUNC_IMPL (i, name, strcmp,
IFUNC_IMPL_ADD (array, i, strcmp,
- CPU_FEATURE_USABLE (AVX2),
+ (CPU_FEATURE_USABLE (AVX2)
+ && CPU_FEATURE_USABLE (BMI2)),
__strcmp_avx2)
IFUNC_IMPL_ADD (array, i, strcmp,
(CPU_FEATURE_USABLE (AVX2)
+ && CPU_FEATURE_USABLE (BMI2)
&& CPU_FEATURE_USABLE (RTM)),
__strcmp_avx2_rtm)
IFUNC_IMPL_ADD (array, i, strcmp,
diff --git a/sysdeps/x86_64/multiarch/strcmp.c b/sysdeps/x86_64/multiarch/strcmp.c
index b457fb4c15..0c0cd20a03 100644
--- a/sysdeps/x86_64/multiarch/strcmp.c
+++ b/sysdeps/x86_64/multiarch/strcmp.c
@@ -40,11 +40,11 @@ IFUNC_SELECTOR (void)
const struct cpu_features* cpu_features = __get_cpu_features ();
if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)
+ && CPU_FEATURE_USABLE_P (cpu_features, BMI2)
&& CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
{
if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
- && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)
- && CPU_FEATURE_USABLE_P (cpu_features, BMI2))
+ && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
return OPTIMIZE (evex);
if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
--
2.35.1
next prev parent reply other threads:[~2022-10-03 22:04 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-03 22:04 [COMMITTED 2.33 1/8] x86: include BMI1 and BMI2 in x86-64-v3 level Aurelien Jarno
2022-10-03 22:04 ` [COMMITTED 2.33 2/8] x86-64: Require BMI2 for AVX2 str(n)casecmp implementations Aurelien Jarno
2022-10-03 22:04 ` Aurelien Jarno [this message]
2022-10-03 22:04 ` [COMMITTED 2.33 4/8] x86-64: Require BMI2 for AVX2 strncmp implementation Aurelien Jarno
2022-10-03 22:04 ` [COMMITTED 2.33 5/8] x86-64: Require BMI2 for AVX2 wcs(n)cmp implementations Aurelien Jarno
2022-10-03 22:04 ` [COMMITTED 2.33 6/8] x86-64: Require BMI2 for AVX2 (raw|w)memchr implementations Aurelien Jarno
2022-10-03 22:04 ` [COMMITTED 2.33 7/8] x86-64: Require BMI2 and LZCNT for AVX2 memrchr implementation Aurelien Jarno
2022-10-03 22:04 ` [COMMITTED 2.33 8/8] x86-64: Require BMI1/BMI2 for AVX2 strrchr and wcsrchr implementations Aurelien Jarno
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