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

[Noah Goldstein <goldstein.w.n@gmail.com>]

On Wed, Jul 6, 2022 at 12:43 AM Mayshao-oc <Mayshao-oc@zhaoxin.com> wrote:
>
> On Wed, Jul 6, 2022 at 10:14 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > On Tue, Jul 5, 2022 at 7:05 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > >
> > > On Tue, Jul 5, 2022 at 6:33 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > >
> > > > 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?
> > >
> > > That they are faster or that sse2 can run on baseline x86_64?
>
> Both cases are true on Zhaoxin processors.
>
> >
> > Assuming you mean faster:
> >
> > maybe not for large strings on a processor that heavily prefers aligned
> > access.
> >
> > The generics are implemented as:
> >
> > strncat = strnlen + strlen + memcpy
> > strncpy = strnlen + memset + memcpy
> > stpncpy = strnlen + memset + memcpy
> >
> > For very large strings on processors with SSSE3
> > all of those functions can be implemented with only aligned
> > access in the loops.
> >
> > Not sure if it would work in favor of the generic implementations though as
> > they are essentially doing 2x + the number of memory accesses.
> >
> > mayshao do you have benchmark numbers on these functions?
>
> The results are attached.  If there is any problem with the results, please
> feel free to let me know.

Thank you,

Any chance you have performance numbers for:

strcpy_sse2 vs strcpy_sse2_unaligned
stpcpy_sse2 vs stpcpy_sse2_unaligned
strcat_sse2 vs strcat_sse2_unaligned
?
>
>
> Best Regards,
> May Shao
>
> >
> > >
> > >
> > > >
> > > > > 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.
> >