[PATCH] x86_64: Add tanh with FMA

[Sunil Pandey]

On Wed, Mar 12, 2025 at 3:02 PM H.J. Lu <hjl.tools@gmail.com> wrote:

> On Wed, Mar 12, 2025 at 2:00 PM Sunil K Pandey <skpgkp2@gmail.com> wrote:
> >
> > On Skylake, it improves tanh bench performance by:
> >
> >         Before          After           Improvement
> > max     110.89          95.826          14%
> > min     20.966          20.157          4%
> > mean    30.9601         29.8431         4%
> > ---
> >  sysdeps/ieee754/dbl-64/s_tanh.c           |  5 ++++
> >  sysdeps/x86_64/fpu/multiarch/Makefile     |  2 ++
> >  sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c | 11 ++++++++
> >  sysdeps/x86_64/fpu/multiarch/s_tanh.c     | 31 +++++++++++++++++++++++
> >  4 files changed, 49 insertions(+)
> >  create mode 100644 sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c
> >  create mode 100644 sysdeps/x86_64/fpu/multiarch/s_tanh.c
> >
> > diff --git a/sysdeps/ieee754/dbl-64/s_tanh.c
> b/sysdeps/ieee754/dbl-64/s_tanh.c
> > index 673a97102d..13063db04e 100644
> > --- a/sysdeps/ieee754/dbl-64/s_tanh.c
> > +++ b/sysdeps/ieee754/dbl-64/s_tanh.c
> > @@ -46,6 +46,11 @@ static char rcsid[] = "$NetBSD: s_tanh.c,v 1.7
> 1995/05/10 20:48:22 jtc Exp $";
> >
> >  static const double one = 1.0, two = 2.0, tiny = 1.0e-300;
> >
> > +#ifndef SECTION
> > +# define SECTION
> > +#endif
> > +
> > +SECTION
> >  double
> >  __tanh (double x)
> >  {
> > diff --git a/sysdeps/x86_64/fpu/multiarch/Makefile
> b/sysdeps/x86_64/fpu/multiarch/Makefile
> > index e823d2fcc6..a198315f1c 100644
> > --- a/sysdeps/x86_64/fpu/multiarch/Makefile
> > +++ b/sysdeps/x86_64/fpu/multiarch/Makefile
> > @@ -10,6 +10,7 @@ CFLAGS-s_expm1-fma.c = -mfma -mavx2
> >  CFLAGS-s_log1p-fma.c = -mfma -mavx2
> >  CFLAGS-s_sin-fma.c = -mfma -mavx2
> >  CFLAGS-s_tan-fma.c = -mfma -mavx2
> > +CFLAGS-s_tanh-fma.c = -mfma -mavx2
> >  CFLAGS-s_sincos-fma.c = -mfma -mavx2
> >  CFLAGS-s_exp10m1f-fma.c = -mfma -mavx2
> >  CFLAGS-s_exp2m1f-fma.c = -mfma -mavx2
> > @@ -96,6 +97,7 @@ libm-sysdep_routines += \
> >    s_sinf-sse2 \
> >    s_tan-avx \
> >    s_tan-fma \
> > +  s_tanh-fma \
> >    s_trunc-sse4_1 \
> >    s_truncf-sse4_1 \
> >  # libm-sysdep_routines
> > diff --git a/sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c
> b/sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c
> > new file mode 100644
> > index 0000000000..1b808b1227
> > --- /dev/null
> > +++ b/sysdeps/x86_64/fpu/multiarch/s_tanh-fma.c
> > @@ -0,0 +1,11 @@
> > +#define __tanh __tanh_fma
> > +#define __expm1 __expm1_fma
> > +
> > +/* NB: __expm1 may be expanded to __expm1_fma in the following
> > +   prototypes.  */
> > +extern long double __expm1l (long double);
> > +extern long double __expm1f128 (long double);
> > +
> > +#define SECTION __attribute__ ((section (".text.fma")))
> > +
> > +#include <sysdeps/ieee754/dbl-64/s_tanh.c>
> > diff --git a/sysdeps/x86_64/fpu/multiarch/s_tanh.c
> b/sysdeps/x86_64/fpu/multiarch/s_tanh.c
> > new file mode 100644
> > index 0000000000..5539b6c61c
> > --- /dev/null
> > +++ b/sysdeps/x86_64/fpu/multiarch/s_tanh.c
> > @@ -0,0 +1,31 @@
> > +/* Multiple versions of tanh.
> > +   Copyright (C) 2025 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 <sysdeps/x86/isa-level.h>
> > +#if MINIMUM_X86_ISA_LEVEL < AVX2_X86_ISA_LEVEL
> > +
> > +extern double __redirect_tanh (double);
> > +
> > +# define SYMBOL_NAME tanh
> > +# include "ifunc-fma.h"
> > +
> > +libc_ifunc_redirected (__redirect_tanh, __tanh, IFUNC_SELECTOR ());
> > +
> > +# define __tanh __tanh_sse2
> > +#endif
> > +#include <sysdeps/ieee754/dbl-64/s_tanh.c>
> > --
> > 2.48.1
> >
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
> Thanks.
>
> --
> H.J.
>

I would like to backport this patch to release branches.

Any comments or objections?

--Sunil
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