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[Bug libc/21396] Use AVX2 memcpy/memset on Skylake server


https://sourceware.org/bugzilla/show_bug.cgi?id=21396

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4cb334c4d6249686653137ec273d081371b3672d

commit 4cb334c4d6249686653137ec273d081371b3672d
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Tue Apr 18 14:01:45 2017 -0700

    x86: Use AVX2 memcpy/memset on Skylake server [BZ #21396]

    On Skylake server, AVX512 load/store instructions in memcpy/memset may
    lead to lower CPU turbo frequency in certain situations.  Use of AVX2
    in memcpy/memset has been observed to have improved overall performance
    in many workloads due to the higher frequency.

    Since AVX512ER is unique to Xeon Phi, this patch sets Prefer_No_AVX512
    if AVX512ER isn't available so that AVX2 versions of memcpy/memset are
    used on Skylake server.

        [BZ #21396]
        * sysdeps/x86/cpu-features.c (init_cpu_features): Set
        Prefer_No_AVX512 if AVX512ER isn't available.
        * sysdeps/x86/cpu-features.h (bit_arch_Prefer_No_AVX512): New.
        (index_arch_Prefer_No_AVX512): Likewise.
        * sysdeps/x86_64/multiarch/memcpy.S (__new_memcpy): Don't use
        AVX512 version if Prefer_No_AVX512 is set.
        * sysdeps/x86_64/multiarch/memcpy_chk.S (__memcpy_chk):
        Likewise.
        * sysdeps/x86_64/multiarch/memmove.S (__libc_memmove): Likewise.
        * sysdeps/x86_64/multiarch/memmove_chk.S (__memmove_chk):
        Likewise.
        * sysdeps/x86_64/multiarch/mempcpy.S (__mempcpy): Likewise.
        * sysdeps/x86_64/multiarch/mempcpy_chk.S (__mempcpy_chk):
        Likewise.
        * sysdeps/x86_64/multiarch/memset.S (memset): Likewise.
        * sysdeps/x86_64/multiarch/memset_chk.S (__memset_chk):
        Likewise.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                              |   21 +++++++++++++++++++++
 sysdeps/x86/cpu-features.c             |    6 +++++-
 sysdeps/x86/cpu-features.h             |    3 +++
 sysdeps/x86_64/multiarch/memcpy.S      |    2 ++
 sysdeps/x86_64/multiarch/memcpy_chk.S  |    2 ++
 sysdeps/x86_64/multiarch/memmove.S     |    2 ++
 sysdeps/x86_64/multiarch/memmove_chk.S |    2 ++
 sysdeps/x86_64/multiarch/mempcpy.S     |    2 ++
 sysdeps/x86_64/multiarch/mempcpy_chk.S |    2 ++
 sysdeps/x86_64/multiarch/memset.S      |    2 ++
 sysdeps/x86_64/multiarch/memset_chk.S  |    2 ++
 11 files changed, 45 insertions(+), 1 deletions(-)

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