[Bug string/19881] Improve x86-64 memset

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19881

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=830566307f038387ca0af3fd327706a8d1a2f595

commit 830566307f038387ca0af3fd327706a8d1a2f595
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Thu Mar 31 10:05:51 2016 -0700

    Add x86-64 memset with unaligned store and rep stosb

    Implement x86-64 memset with unaligned store and rep movsb.  Support
    16-byte, 32-byte and 64-byte vector register sizes.  A single file
    provides 2 implementations of memset, one with rep stosb and the other
    without rep stosb.  They share the same codes when size is between 2
    times of vector register size and REP_STOSB_THRESHOLD which defaults
    to 2KB.

    Key features:

    1. Use overlapping store to avoid branch.
    2. For size <= 4 times of vector register size, fully unroll the loop.
    3. For size > 4 times of vector register size, store 4 times of vector
    register size at a time.

        [BZ #19881]
        * sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add
        memset-sse2-unaligned-erms, memset-avx2-unaligned-erms and
        memset-avx512-unaligned-erms.
        * sysdeps/x86_64/multiarch/ifunc-impl-list.c
        (__libc_ifunc_impl_list): Test __memset_chk_sse2_unaligned,
        __memset_chk_sse2_unaligned_erms, __memset_chk_avx2_unaligned,
        __memset_chk_avx2_unaligned_erms, __memset_chk_avx512_unaligned,
        __memset_chk_avx512_unaligned_erms, __memset_sse2_unaligned,
        __memset_sse2_unaligned_erms, __memset_erms,
        __memset_avx2_unaligned, __memset_avx2_unaligned_erms,
        __memset_avx512_unaligned_erms and __memset_avx512_unaligned.
        * sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S: New
        file.
        * sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S:
        Likewise.
        * sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S:
        Likewise.
        * sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S:
        Likewise.

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

Summary of changes:
 ChangeLog                                          |   23 ++
 sysdeps/x86_64/multiarch/Makefile                  |    5 +-
 sysdeps/x86_64/multiarch/ifunc-impl-list.c         |   33 +++
 .../x86_64/multiarch/memset-avx2-unaligned-erms.S  |   14 +
 .../multiarch/memset-avx512-unaligned-erms.S       |   17 ++
 .../x86_64/multiarch/memset-sse2-unaligned-erms.S  |   16 ++
 .../x86_64/multiarch/memset-vec-unaligned-erms.S   |  251 ++++++++++++++++++++
 7 files changed, 358 insertions(+), 1 deletions(-)
 create mode 100644 sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S
 create mode 100644 sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S
 create mode 100644 sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S
 create mode 100644 sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S

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