Re: [PATCH v1] x86: Remove generic strncat, strncpy, and stpncpy implementations

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

On Tue, Jul 5, 2022 at 5:06 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> These functions all have optimized versions:
> __strncat_sse2_unaligned, __strncpy_sse2_unaligned, and
> stpncpy_sse2_unaligned which are faster than their respective generic
> implementations.  Since the sse2 versions can run on baseline x86_64,

Is this true on all x86-64 processors?

> we should use these as the baseline implementation and can remove the
> generic implementations.
>
> Geometric mean of N=20 runs of the entire benchmark suite on:
> 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz (Tigerlake)
>
> __strncat_sse2_unaligned / __strncat_generic: .944
> __strncpy_sse2_unaligned / __strncpy_generic: .726
> __stpncpy_sse2_unaligned / __stpncpy_generic: .650
>
> Tested build with and without multiarch and full check with multiarch.
> ---
>  sysdeps/x86_64/multiarch/Makefile          |  3 --
>  sysdeps/x86_64/multiarch/ifunc-impl-list.c |  9 ++--
>  sysdeps/x86_64/multiarch/ifunc-strcpy.h    |  8 +---
>  sysdeps/x86_64/multiarch/ifunc-strncpy.h   | 48 ++++++++++++++++++++++
>  sysdeps/x86_64/multiarch/stpncpy-generic.c | 26 ------------
>  sysdeps/x86_64/multiarch/stpncpy.c         |  3 +-
>  sysdeps/x86_64/multiarch/strncat-generic.c | 21 ----------
>  sysdeps/x86_64/multiarch/strncat.c         |  3 +-
>  sysdeps/x86_64/multiarch/strncpy-generic.c | 24 -----------
>  sysdeps/x86_64/multiarch/strncpy.c         |  3 +-
>  10 files changed, 56 insertions(+), 92 deletions(-)
>  create mode 100644 sysdeps/x86_64/multiarch/ifunc-strncpy.h
>  delete mode 100644 sysdeps/x86_64/multiarch/stpncpy-generic.c
>  delete mode 100644 sysdeps/x86_64/multiarch/strncat-generic.c
>  delete mode 100644 sysdeps/x86_64/multiarch/strncpy-generic.c
>
> diff --git a/sysdeps/x86_64/multiarch/Makefile b/sysdeps/x86_64/multiarch/Makefile
> index 18cea04423..04e238efa0 100644
> --- a/sysdeps/x86_64/multiarch/Makefile
> +++ b/sysdeps/x86_64/multiarch/Makefile
> @@ -45,7 +45,6 @@ sysdep_routines += \
>    stpcpy-sse2-unaligned \
>    stpncpy-avx2 \
>    stpncpy-avx2-rtm \
> -  stpncpy-generic \
>    stpncpy-evex \
>    stpncpy-sse2-unaligned \
>    strcasecmp_l-avx2 \
> @@ -92,7 +91,6 @@ sysdep_routines += \
>    strncase_l-sse4_2 \
>    strncat-avx2 \
>    strncat-avx2-rtm \
> -  strncat-generic \
>    strncat-evex \
>    strncat-sse2-unaligned \
>    strncmp-avx2 \
> @@ -102,7 +100,6 @@ sysdep_routines += \
>    strncmp-sse4_2 \
>    strncpy-avx2 \
>    strncpy-avx2-rtm \
> -  strncpy-generic \
>    strncpy-evex \
>    strncpy-sse2-unaligned \
>    strnlen-avx2 \
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index adf7d4bafd..2c96cb62d2 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -403,8 +403,7 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>                                && CPU_FEATURE_USABLE (AVX512BW)),
>                               __stpncpy_evex)
>               IFUNC_IMPL_ADD (array, i, stpncpy, 1,
> -                             __stpncpy_sse2_unaligned)
> -             IFUNC_IMPL_ADD (array, i, stpncpy, 1, __stpncpy_generic))
> +                             __stpncpy_sse2_unaligned))
>
>    /* Support sysdeps/x86_64/multiarch/stpcpy.c.  */
>    IFUNC_IMPL (i, name, stpcpy,
> @@ -618,8 +617,7 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>                                && CPU_FEATURE_USABLE (AVX512BW)),
>                               __strncat_evex)
>               IFUNC_IMPL_ADD (array, i, strncat, 1,
> -                             __strncat_sse2_unaligned)
> -             IFUNC_IMPL_ADD (array, i, strncat, 1, __strncat_generic))
> +                             __strncat_sse2_unaligned))
>
>    /* Support sysdeps/x86_64/multiarch/strncpy.c.  */
>    IFUNC_IMPL (i, name, strncpy,
> @@ -634,8 +632,7 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>                                && CPU_FEATURE_USABLE (AVX512BW)),
>                               __strncpy_evex)
>               IFUNC_IMPL_ADD (array, i, strncpy, 1,
> -                             __strncpy_sse2_unaligned)
> -             IFUNC_IMPL_ADD (array, i, strncpy, 1, __strncpy_generic))
> +                             __strncpy_sse2_unaligned))
>
>    /* Support sysdeps/x86_64/multiarch/strpbrk.c.  */
>    IFUNC_IMPL (i, name, strpbrk,
> diff --git a/sysdeps/x86_64/multiarch/ifunc-strcpy.h b/sysdeps/x86_64/multiarch/ifunc-strcpy.h
> index 80529458d1..a15afa44e9 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-strcpy.h
> +++ b/sysdeps/x86_64/multiarch/ifunc-strcpy.h
> @@ -20,11 +20,7 @@
>
>  #include <init-arch.h>
>
> -#ifndef GENERIC
> -# define GENERIC sse2
> -#endif
> -
> -extern __typeof (REDIRECT_NAME) OPTIMIZE (GENERIC) attribute_hidden;
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2_unaligned)
>    attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> @@ -53,5 +49,5 @@ IFUNC_SELECTOR (void)
>    if (CPU_FEATURES_ARCH_P (cpu_features, Fast_Unaligned_Load))
>      return OPTIMIZE (sse2_unaligned);
>
> -  return OPTIMIZE (GENERIC);
> +  return OPTIMIZE (sse2);
>  }
> diff --git a/sysdeps/x86_64/multiarch/ifunc-strncpy.h b/sysdeps/x86_64/multiarch/ifunc-strncpy.h
> new file mode 100644
> index 0000000000..323225af4d
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/ifunc-strncpy.h
> @@ -0,0 +1,48 @@
> +/* Common definition for ifunc st{r|p}n{cpy|cat}
> +   All versions must be listed in ifunc-impl-list.c.
> +   Copyright (C) 2022 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
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <init-arch.h>
> +
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2_unaligned)
> +  attribute_hidden;
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;
> +
> +static inline void *
> +IFUNC_SELECTOR (void)
> +{
> +  const struct cpu_features* cpu_features = __get_cpu_features ();
> +
> +  if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> +      && 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))
> +       return OPTIMIZE (evex);
> +
> +      if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
> +       return OPTIMIZE (avx2_rtm);
> +
> +      if (!CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_VZEROUPPER))
> +       return OPTIMIZE (avx2);
> +    }
> +
> +  return OPTIMIZE (sse2_unaligned);
> +}
> diff --git a/sysdeps/x86_64/multiarch/stpncpy-generic.c b/sysdeps/x86_64/multiarch/stpncpy-generic.c
> deleted file mode 100644
> index 87826845b0..0000000000
> --- a/sysdeps/x86_64/multiarch/stpncpy-generic.c
> +++ /dev/null
> @@ -1,26 +0,0 @@
> -/* stpncpy.
> -   Copyright (C) 2022 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
> -   <https://www.gnu.org/licenses/>.  */
> -
> -
> -#define STPNCPY __stpncpy_generic
> -#undef weak_alias
> -#define weak_alias(ignored1, ignored2)
> -#undef libc_hidden_def
> -#define libc_hidden_def(stpncpy)
> -
> -#include <string/stpncpy.c>
> diff --git a/sysdeps/x86_64/multiarch/stpncpy.c b/sysdeps/x86_64/multiarch/stpncpy.c
> index 879bc83f0b..a8d083ff0d 100644
> --- a/sysdeps/x86_64/multiarch/stpncpy.c
> +++ b/sysdeps/x86_64/multiarch/stpncpy.c
> @@ -25,9 +25,8 @@
>  # undef stpncpy
>  # undef __stpncpy
>
> -# define GENERIC generic
>  # define SYMBOL_NAME stpncpy
> -# include "ifunc-strcpy.h"
> +# include "ifunc-strncpy.h"
>
>  libc_ifunc_redirected (__redirect_stpncpy, __stpncpy, IFUNC_SELECTOR ());
>
> diff --git a/sysdeps/x86_64/multiarch/strncat-generic.c b/sysdeps/x86_64/multiarch/strncat-generic.c
> deleted file mode 100644
> index 0090669cd1..0000000000
> --- a/sysdeps/x86_64/multiarch/strncat-generic.c
> +++ /dev/null
> @@ -1,21 +0,0 @@
> -/* strncat.
> -   Copyright (C) 2022 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
> -   <https://www.gnu.org/licenses/>.  */
> -
> -
> -#define STRNCAT __strncat_generic
> -#include <string/strncat.c>
> diff --git a/sysdeps/x86_64/multiarch/strncat.c b/sysdeps/x86_64/multiarch/strncat.c
> index 50fba8a41f..a590c25d51 100644
> --- a/sysdeps/x86_64/multiarch/strncat.c
> +++ b/sysdeps/x86_64/multiarch/strncat.c
> @@ -24,8 +24,7 @@
>  # undef strncat
>
>  # define SYMBOL_NAME strncat
> -# define GENERIC generic
> -# include "ifunc-strcpy.h"
> +# include "ifunc-strncpy.h"
>
>  libc_ifunc_redirected (__redirect_strncat, strncat, IFUNC_SELECTOR ());
>  strong_alias (strncat, __strncat);
> diff --git a/sysdeps/x86_64/multiarch/strncpy-generic.c b/sysdeps/x86_64/multiarch/strncpy-generic.c
> deleted file mode 100644
> index 9916153dd5..0000000000
> --- a/sysdeps/x86_64/multiarch/strncpy-generic.c
> +++ /dev/null
> @@ -1,24 +0,0 @@
> -/* strncpy.
> -   Copyright (C) 2022 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
> -   <https://www.gnu.org/licenses/>.  */
> -
> -
> -#define STRNCPY __strncpy_generic
> -#undef libc_hidden_builtin_def
> -#define libc_hidden_builtin_def(strncpy)
> -
> -#include <string/strncpy.c>
> diff --git a/sysdeps/x86_64/multiarch/strncpy.c b/sysdeps/x86_64/multiarch/strncpy.c
> index 7fc7d72ec5..c83440f0e3 100644
> --- a/sysdeps/x86_64/multiarch/strncpy.c
> +++ b/sysdeps/x86_64/multiarch/strncpy.c
> @@ -24,8 +24,7 @@
>  # undef strncpy
>
>  # define SYMBOL_NAME strncpy
> -# define GENERIC generic
> -# include "ifunc-strcpy.h"
> +# include "ifunc-strncpy.h"
>
>  libc_ifunc_redirected (__redirect_strncpy, strncpy, IFUNC_SELECTOR ());
>
> --
> 2.34.1
>


--
H.J.