Re: [PATCH] x86_64: memset optimized with AVX512

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Dec 3, 2015 at 12:46 PM, Andrew Senkevich
<andrew.n.senkevich@gmail.com> wrote:
> Hi,
>
> here is AVX512 memset implementation.
> It is faster enough than AVX2 memset on KNL hardware, performance
> results attached.
>
> 2015-12-03  Andrew Senkevich  <andrew.senkevich@intel.com>
>
>         * sysdeps/x86_64/multiarch/Makefile: Added new file.
>         * sysdeps/x86_64/multiarch/ifunc-impl-list.c: Added test.
>         * sysdeps/x86_64/multiarch/memset-avx512.S: New file.
>         * sysdeps/x86_64/multiarch/memset.S: Added new IFUNC branch.
>         * sysdeps/x86_64/multiarch/memset-avx2.S: Added libc_hidden_def for
>         __memset_avx2.
>
> diff --git a/sysdeps/x86_64/multiarch/Makefile
> b/sysdeps/x86_64/multiarch/Makefile
> index bb811c2..5bb859e 100644
> --- a/sysdeps/x86_64/multiarch/Makefile
> +++ b/sysdeps/x86_64/multiarch/Makefile
> @@ -18,7 +18,7 @@ sysdep_routines += strncat-c stpncpy-c strncpy-c
> strcmp-ssse3 \
>                    stpcpy-sse2-unaligned stpncpy-sse2-unaligned \
>                    strcat-sse2-unaligned strncat-sse2-unaligned \
>                    strchr-sse2-no-bsf memcmp-ssse3 strstr-sse2-unaligned \
> -                  strcspn-c strpbrk-c strspn-c varshift memset-avx2
> +                  strcspn-c strpbrk-c strspn-c varshift memset-avx2
> memset-avx512
>  CFLAGS-varshift.c += -msse4
>  CFLAGS-strcspn-c.c += -msse4
>  CFLAGS-strpbrk-c.c += -msse4
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index 5c0c219..a8be3eb 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -83,7 +83,10 @@ __libc_ifunc_impl_list (const char *name, struct
> libc_ifunc_impl *array,
>               IFUNC_IMPL_ADD (array, i, memset, 1, __memset_sse2)
>               IFUNC_IMPL_ADD (array, i, memset,
>                               HAS_ARCH_FEATURE (AVX2_Usable),
> -                             __memset_avx2))
> +                             __memset_avx2)
> +             IFUNC_IMPL_ADD (array, i, memset,
> +                             HAS_ARCH_FEATURE (AVX512F_Usable),
> +                             __memset_avx512))
>
>    /* Support sysdeps/x86_64/multiarch/stpncpy.S.  */
>    IFUNC_IMPL (i, name, stpncpy,
> diff --git a/sysdeps/x86_64/multiarch/memset-avx2.S
> b/sysdeps/x86_64/multiarch/memset-avx2.S
> index 28eabad..f96baf3 100644
> --- a/sysdeps/x86_64/multiarch/memset-avx2.S
> +++ b/sysdeps/x86_64/multiarch/memset-avx2.S
> @@ -165,4 +165,6 @@ L(gobble_data):
>         ret
>
>  END (MEMSET)
> +libc_hidden_def (__memset_avx2)

Why is this change needed?  If it is needed, please submit
a separate patch.

> +
>  #endif
> diff --git a/sysdeps/x86_64/multiarch/memset-avx512.S
> b/sysdeps/x86_64/multiarch/memset-avx512.S
> new file mode 100644
> index 0000000..083177e
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/memset-avx512.S
> @@ -0,0 +1,191 @@
> +/* memset optimized with AVX512.
> +   Copyright (C) 2015 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <sysdep.h>
> +
> +#if IS_IN (libc)
> +
> +#include "asm-syntax.h"
> +#ifndef MEMSET
> +# define MEMSET        __memset_avx512
> +#endif
> +

Should __memset_chk_avx512 also be provided?

-- 
H.J.