Re: [PATCH v2 2/3] x86: Add support to build wcscpy with explicit ISA level

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

On Wed, Jul 13, 2022 at 4:33 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> 1. Add ISA level build guards to different implementations.
>     - wcscpy-ssse3.S is used as ISA level 2/3/4.
>     - wcscpy-generic.c is only used at ISA level 1 and will
>       only build if compiled with ISA level == 1. Otherwise
>       there is no reason to include it as we will always use
>       wcscpy-ssse3.S
>
> 2. Refactor the ifunc selector and ifunc implementation list to use
>    the ISA level aware wrapper macros that allow functions below the
>    compiled ISA level (with a guranteed replacement) to be skipped.
>
> Tested with and without multiarch on x86_64 for ISA levels:
> {generic, x86-64-v2, x86-64-v3, x86-64-v4}
>
> And m32 with and without multiarch.
> ---
>  sysdeps/x86_64/Makefile                    |  1 +
>  sysdeps/x86_64/multiarch/Makefile          |  1 -
>  sysdeps/x86_64/multiarch/ifunc-impl-list.c | 12 +++++--
>  sysdeps/x86_64/multiarch/wcscpy-generic.c  |  9 +++--
>  sysdeps/x86_64/multiarch/wcscpy-ssse3.S    | 16 +++++++--
>  sysdeps/x86_64/multiarch/wcscpy.c          |  5 +--
>  sysdeps/x86_64/wcscpy-generic.c            | 31 +++++++++++++++++
>  sysdeps/x86_64/wcscpy.S                    | 40 ++++++++++++++++++++++
>  8 files changed, 103 insertions(+), 12 deletions(-)
>  create mode 100644 sysdeps/x86_64/wcscpy-generic.c
>  create mode 100644 sysdeps/x86_64/wcscpy.S
>
> diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
> index 341ee69a35..c19bef2dec 100644
> --- a/sysdeps/x86_64/Makefile
> +++ b/sysdeps/x86_64/Makefile
> @@ -199,6 +199,7 @@ endif
>  ifeq ($(subdir),wcsmbs)
>
>  sysdep_routines += \
> +  wcscpy-generic \
>    wcsncmp-generic \
>    wcsnlen-generic \
>  # sysdep_routines
> diff --git a/sysdeps/x86_64/multiarch/Makefile b/sysdeps/x86_64/multiarch/Makefile
> index ba29a65716..df4601c294 100644
> --- a/sysdeps/x86_64/multiarch/Makefile
> +++ b/sysdeps/x86_64/multiarch/Makefile
> @@ -134,7 +134,6 @@ sysdep_routines += \
>    wcscmp-avx2-rtm \
>    wcscmp-evex \
>    wcscmp-sse2 \
> -  wcscpy-generic \
>    wcscpy-ssse3 \
>    wcslen-avx2 \
>    wcslen-avx2-rtm \
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index 3b1df9b73c..9318e98cc8 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -791,9 +791,15 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>
>    /* Support sysdeps/x86_64/multiarch/wcscpy.c.  */
>    IFUNC_IMPL (i, name, wcscpy,
> -             IFUNC_IMPL_ADD (array, i, wcscpy, CPU_FEATURE_USABLE (SSSE3),
> -                             __wcscpy_ssse3)
> -             IFUNC_IMPL_ADD (array, i, wcscpy, 1, __wcscpy_generic))
> +             /* ISA V4 wrapper for SSSE3 implementation because
> +                the SSSE3 implementation is also used at ISA
> +                level 3/4.  */
> +             X86_IFUNC_IMPL_ADD_V4 (array, i, wcscpy,
> +                                    CPU_FEATURE_USABLE (SSSE3),
> +                                    __wcscpy_ssse3)
> +             X86_IFUNC_IMPL_ADD_V1 (array, i, wcscpy,
> +                                    1,
> +                                    __wcscpy_generic))
>
>    /* Support sysdeps/x86_64/multiarch/wcslen.c.  */
>    IFUNC_IMPL (i, name, wcslen,
> diff --git a/sysdeps/x86_64/multiarch/wcscpy-generic.c b/sysdeps/x86_64/multiarch/wcscpy-generic.c
> index 5ea905f33f..93d314aaad 100644
> --- a/sysdeps/x86_64/multiarch/wcscpy-generic.c
> +++ b/sysdeps/x86_64/multiarch/wcscpy-generic.c
> @@ -17,8 +17,11 @@
>     <https://www.gnu.org/licenses/>.  */
>
>
> -#if IS_IN (libc)
> +#include <isa-level.h>
> +
> +#if ISA_SHOULD_BUILD (1)
> +
>  # define WCSCPY  __wcscpy_generic
> -#endif
> +# include <wcsmbs/wcscpy.c>
>
> -#include <wcsmbs/wcscpy.c>
> +#endif
> diff --git a/sysdeps/x86_64/multiarch/wcscpy-ssse3.S b/sysdeps/x86_64/multiarch/wcscpy-ssse3.S
> index aa2b9d030f..62741071e6 100644
> --- a/sysdeps/x86_64/multiarch/wcscpy-ssse3.S
> +++ b/sysdeps/x86_64/multiarch/wcscpy-ssse3.S
> @@ -16,11 +16,21 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#if IS_IN (libc)
> +#include <isa-level.h>
> +
> +/* MINIMUM_X86_ISA_LEVEL <= 4 because there are not V3/V4
> +   implementations so we need this to build for ISA V3/V4
> +    builds. */
> +#if ISA_SHOULD_BUILD (4)
> +
> +# ifndef WCSCPY
> +#  define WCSCPY       __wcscpy_ssse3
> +# endif
> +
>  # include <sysdep.h>
>
>         .section .text.ssse3,"ax",@progbits
> -ENTRY (__wcscpy_ssse3)
> +ENTRY (WCSCPY)
>
>         mov     %rsi, %rcx
>         mov     %rdi, %rdx
> @@ -547,5 +557,5 @@ L(Exit16):
>         mov     %rdi, %rax
>         ret
>
> -END(__wcscpy_ssse3)
> +END(WCSCPY)
>  #endif
> diff --git a/sysdeps/x86_64/multiarch/wcscpy.c b/sysdeps/x86_64/multiarch/wcscpy.c
> index 53c3228dc2..92c917b6b4 100644
> --- a/sysdeps/x86_64/multiarch/wcscpy.c
> +++ b/sysdeps/x86_64/multiarch/wcscpy.c
> @@ -26,15 +26,16 @@
>  # define SYMBOL_NAME wcscpy
>  # include <init-arch.h>
>
> -extern __typeof (REDIRECT_NAME) OPTIMIZE (generic) attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (ssse3) attribute_hidden;
>
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (generic) attribute_hidden;
> +
>  static inline void *
>  IFUNC_SELECTOR (void)
>  {
>    const struct cpu_features* cpu_features = __get_cpu_features ();
>
> -  if (CPU_FEATURE_USABLE_P (cpu_features, SSSE3))
> +  if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, SSSE3))
>      return OPTIMIZE (ssse3);
>
>    return OPTIMIZE (generic);
> diff --git a/sysdeps/x86_64/wcscpy-generic.c b/sysdeps/x86_64/wcscpy-generic.c
> new file mode 100644
> index 0000000000..eef74ae53d
> --- /dev/null
> +++ b/sysdeps/x86_64/wcscpy-generic.c
> @@ -0,0 +1,31 @@
> +/* wcscpy dispatch for RTLD and non-multiarch .c ISA level 1 build.
> +   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/>.  */
> +
> +/* wcscpy non-multiarch build is split into two files,
> +   wcscpy-generic.c and wcscpy.S. The wcscpy-generic.c build is for
> +   ISA level <= 1 and just uses wcsmbs/wcscpy.c.  This must be split
> +   into two files because we cannot include C code from assembly or
> +   vice versa.  */
> +
> +#include <isa-level.h>
> +
> +#if MINIMUM_X86_ISA_LEVEL <= 1
> +
> +# include "wcsmbs/wcscpy.c"
> +
> +#endif
> diff --git a/sysdeps/x86_64/wcscpy.S b/sysdeps/x86_64/wcscpy.S
> new file mode 100644
> index 0000000000..11d0bb4bab
> --- /dev/null
> +++ b/sysdeps/x86_64/wcscpy.S
> @@ -0,0 +1,40 @@
> +/* wcscpy dispatch for RTLD and non-multiarch .c files
> +   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/>.  */
> +
> +/* wcscpy non-multiarch build is split into two files,
> +   wcscpy-generic.c and wcscpy.S. The wcscpy.S build is for
> +   ISA level >= 2 uses the optimized assembly implementations in
> +   multiarch/wcscpy*.S.  This must be split into two files because
> +   we cannot include C code from assembly or vice versa.  */
> +
> +#include <isa-level.h>
> +
> +#if MINIMUM_X86_ISA_LEVEL >= 2
> +
> +# define WCSCPY        __wcscpy
> +
> +# define DEFAULT_IMPL_V2       "multiarch/wcscpy-ssse3.S"
> +/* isa-default-impl.h expects DEFAULT_IMPL_V1 to be defined but it
> +   should never be used from here.  */
> +# define DEFAULT_IMPL_V1       "ERROR -- Invalid ISA IMPL"
> +
> +# include "isa-default-impl.h"
> +
> +weak_alias (__wcscpy, wcscpy)
> +libc_hidden_def (__wcscpy)
> +#endif
> --
> 2.34.1
>

LGTM.

Thanks.

-- 
H.J.