From: Noah Goldstein <goldstein.w.n@gmail.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Mayshao-oc <Mayshao-oc@zhaoxin.com>,
GNU C Library <libc-alpha@sourceware.org>,
"Carlos O'Donell" <carlos@systemhalted.org>
Subject: Re: [PATCH v1] x86: Remove generic strncat, strncpy, and stpncpy implementations
Date: Tue, 5 Jul 2022 19:47:52 -0700 [thread overview]
Message-ID: <CAFUsyfK9W0equpdLCRDctU3oSi8yycTrSvK7dzMN=0A28bjJqg@mail.gmail.com> (raw)
In-Reply-To: <CAFUsyf+egohYVJo6R=VaX9tBOBJpY+UVi5PHDMKcfm32q6wqMA@mail.gmail.com>
On Tue, Jul 5, 2022 at 7:14 PM 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?
>
> 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?
If you do benchmark the strcpy family, any chance you can also
report results for strcpy/stpcpy/strcat sse2 vs sse2_unaligned?
My guess is the sse2_unaligned versions are much faster and if
so we can drop the sse2 implementations.
>
> >
> >
> > >
> > > > 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.
next prev parent reply other threads:[~2022-07-06 2:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-06 0:06 Noah Goldstein
2022-07-06 1:32 ` H.J. Lu
2022-07-06 2:05 ` Noah Goldstein
2022-07-06 2:14 ` Noah Goldstein
2022-07-06 2:47 ` Noah Goldstein [this message]
2022-07-06 7:42 ` Mayshao-oc
2022-07-06 18:49 ` Noah Goldstein
2022-07-07 2:57 ` Mayshao-oc
2022-07-07 3:11 ` Noah Goldstein
2022-07-12 18:43 ` Noah Goldstein
2022-07-06 18:08 ` H.J. Lu
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