[PATCH 16/17] x86_64: Add exp10m1f with FMA

[Noah Goldstein]

On Fri, Oct 25, 2024 at 1:31 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> The CORE-MATH exp10m1f implementation showed slight worse latency
> when using x86_64 baseline ABI.  This patch adds a ifunc variant
> with similar performance for x86_64-v3.
> ---
>  sysdeps/ieee754/flt-32/s_exp10m1f.c           |  2 ++
>  sysdeps/x86_64/fpu/multiarch/Makefile         |  2 ++
>  sysdeps/x86_64/fpu/multiarch/s_exp10m1f-fma.c |  4 +++
>  sysdeps/x86_64/fpu/multiarch/s_exp10m1f.c     | 33 +++++++++++++++++++
>  4 files changed, 41 insertions(+)
>  create mode 100644 sysdeps/x86_64/fpu/multiarch/s_exp10m1f-fma.c
>  create mode 100644 sysdeps/x86_64/fpu/multiarch/s_exp10m1f.c
>
> diff --git a/sysdeps/ieee754/flt-32/s_exp10m1f.c b/sysdeps/ieee754/flt-32/s_exp10m1f.c
> index 610f269b01..c918c905e8 100644
> --- a/sysdeps/ieee754/flt-32/s_exp10m1f.c
> +++ b/sysdeps/ieee754/flt-32/s_exp10m1f.c
> @@ -222,4 +222,6 @@ __exp10m1f (float x)
>        return (s - 1.0) + w * c0;
>      }
>  }
> +#ifndef __exp10m1f
>  libm_alias_float (__exp10m1, exp10m1)
> +#endif
> diff --git a/sysdeps/x86_64/fpu/multiarch/Makefile b/sysdeps/x86_64/fpu/multiarch/Makefile
> index cbe09d49f4..dcff4df2f1 100644
> --- a/sysdeps/x86_64/fpu/multiarch/Makefile
> +++ b/sysdeps/x86_64/fpu/multiarch/Makefile
> @@ -11,6 +11,7 @@ CFLAGS-s_log1p-fma.c = -mfma -mavx2
>  CFLAGS-s_sin-fma.c = -mfma -mavx2
>  CFLAGS-s_tan-fma.c = -mfma -mavx2
>  CFLAGS-s_sincos-fma.c = -mfma -mavx2
> +CFLAGS-s_exp10m1f-fma.c = -mfma -mavx2
>
>  CFLAGS-e_exp2f-fma.c = -mfma -mavx2
>  CFLAGS-e_expf-fma.c = -mfma -mavx2
> @@ -72,6 +73,7 @@ libm-sysdep_routines += \
>    s_ceilf-sse4_1 \
>    s_cosf-fma \
>    s_cosf-sse2 \
> +  s_exp10m1f-fma \
>    s_expm1-fma \
>    s_floor-sse4_1 \
>    s_floorf-sse4_1 \
> diff --git a/sysdeps/x86_64/fpu/multiarch/s_exp10m1f-fma.c b/sysdeps/x86_64/fpu/multiarch/s_exp10m1f-fma.c
> new file mode 100644
> index 0000000000..3dda04e2dd
> --- /dev/null
> +++ b/sysdeps/x86_64/fpu/multiarch/s_exp10m1f-fma.c
> @@ -0,0 +1,4 @@
> +#define __exp10m1f __exp10m1f_fma
> +#define SECTION __attribute__ ((section (".text.fma")))
> +
> +#include <sysdeps/ieee754/flt-32/s_exp10m1f.c>
> diff --git a/sysdeps/x86_64/fpu/multiarch/s_exp10m1f.c b/sysdeps/x86_64/fpu/multiarch/s_exp10m1f.c
> new file mode 100644
> index 0000000000..8040b7ed79
> --- /dev/null
> +++ b/sysdeps/x86_64/fpu/multiarch/s_exp10m1f.c
> @@ -0,0 +1,33 @@
> +/* Multiple versions of exp10m1.
> +   Copyright (C) 2024 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
> +# include <libm-alias-float.h>
> +
> +extern float __redirect_exp10m1f (float);
> +
> +# define SYMBOL_NAME exp10m1f
> +# include "ifunc-fma.h"
> +
> +libc_ifunc_redirected (__redirect_exp10m1f, __exp10m1f, IFUNC_SELECTOR ());
> +libm_alias_float (__exp10m1, exp10m1)
> +
> +# define __exp10m1f __exp10m1f_sse2
> +#endif
> +#include <sysdeps/ieee754/flt-32/s_exp10m1f.c>
> --
> 2.43.0
>

LGTM
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>