[PATCH] powerpc: Add support for fmaf128() in hardware

Adhemerval Zanella adhemerval.zanella@linaro.org
Tue Mar 24 20:23:48 GMT 2020 


On 20/03/2020 17:52, Raphael Moreira Zinsly via Libc-alpha wrote:
> Adds a POWER9 version of fmaf128 that uses the xsmaddqp
> instruction.
> 
> Co-authored-by: Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  .../powerpc64/le/fpu/multiarch/Makefile       |  4 +-
>  .../le/fpu/multiarch/s_fmaf128-power9.c       | 26 +++++++++++++
>  .../le/fpu/multiarch/s_fmaf128-ppc64.c        | 24 ++++++++++++
>  .../powerpc64/le/fpu/multiarch/s_fmaf128.c    | 36 ++++++++++++++++++
>  .../powerpc64/le/power9/fpu/s_fmaf128.c       | 37 +++++++++++++++++++
>  5 files changed, 126 insertions(+), 1 deletion(-)
>  create mode 100644 sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128-power9.c
>  create mode 100644 sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128-ppc64.c
>  create mode 100644 sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128.c
>  create mode 100644 sysdeps/powerpc/powerpc64/le/power9/fpu/s_fmaf128.c
> 
> diff --git a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/Makefile b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/Makefile
> index a32f3d8b81..8db708205e 100644
> --- a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/Makefile
> +++ b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/Makefile
> @@ -1,6 +1,8 @@
>  ifeq ($(subdir),math)
> -libm-sysdep_routines += w_sqrtf128-power9 w_sqrtf128-ppc64le
> +libm-sysdep_routines += w_sqrtf128-power9 w_sqrtf128-ppc64le s_fmaf128-ppc64 s_fmaf128-power9
>  
>  CFLAGS-w_sqrtf128-ppc64le.c += -mfloat128
>  CFLAGS-w_sqrtf128-power9.c += -mfloat128 -mcpu=power9
> +CFLAGS-s_fmaf128-ppc64.c += -mfloat128
> +CFLAGS-s_fmaf128-power9.c += -mfloat128 -mcpu=power9
>  endif

Ok.

> diff --git a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128-power9.c b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128-power9.c
> new file mode 100644
> index 0000000000..8df77ceade
> --- /dev/null
> +++ b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128-power9.c
> @@ -0,0 +1,26 @@
> +/* __fmaf128() PowerPC64LE POWER9 version.
> +   Copyright (C) 2020 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <libm-alias-float128.h>
> +
> +#undef libm_alias_float128
> +#define libm_alias_float128(a, b)
> +
> +#define __fmaf128 __fmaf128_power9
> +
> +#include <sysdeps/powerpc/powerpc64/le/power9/fpu/s_fmaf128.c>

Ok.

> diff --git a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128-ppc64.c b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128-ppc64.c
> new file mode 100644
> index 0000000000..7374a799af
> --- /dev/null
> +++ b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128-ppc64.c
> @@ -0,0 +1,24 @@
> +/* __fmaf128() PowerPC64LE version.
> +   Copyright (C) 2020 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#undef weak_alias
> +#define weak_alias(a, b)
> +
> +#define __fmaf128 __fmaf128_ppc64
> +
> +#include <sysdeps/ieee754/float128/s_fmaf128.c>

Ok.

> diff --git a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128.c b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128.c
> new file mode 100644
> index 0000000000..3a370950f9
> --- /dev/null
> +++ b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/s_fmaf128.c
> @@ -0,0 +1,36 @@
> +/* Multiple versions of fmaf128.
> +   Copyright (C) 2020 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <libm-alias-float128.h>
> +
> +#define fmaf128 __redirect_fmaf128
> +#include <math.h>
> +#undef fmaf128
> +
> +#include <math_ldbl_opt.h>
> +#include "init-arch.h"
> +
> +extern __typeof (__redirect_fmaf128) __fmaf128_ppc64 attribute_hidden;
> +extern __typeof (__redirect_fmaf128) __fmaf128_power9 attribute_hidden;
> +
> +libc_ifunc_redirected (__redirect_fmaf128, __fmaf128,
> +		       (hwcap2 & PPC_FEATURE2_HAS_IEEE128)
> +		       ? __fmaf128_power9
> +		       : __fmaf128_ppc64);
> +
> +libm_alias_float128 (__fma, fma)

Ok.

> diff --git a/sysdeps/powerpc/powerpc64/le/power9/fpu/s_fmaf128.c b/sysdeps/powerpc/powerpc64/le/power9/fpu/s_fmaf128.c
> new file mode 100644
> index 0000000000..ecd30f1cef
> --- /dev/null
> +++ b/sysdeps/powerpc/powerpc64/le/power9/fpu/s_fmaf128.c
> @@ -0,0 +1,37 @@
> +/* Compute x * y + z as a ternary operation for _Float128.  POWER9 version.
> +   Copyright (C) 2020 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.
> +
> +   In addition to the permissions in the GNU Lesser General Public
> +   License, the Free Software Foundation gives you unlimited
> +   permission to link the compiled version of this file into
> +   combinations with other programs, and to distribute those
> +   combinations without any restriction coming from the use of this
> +   file.  (The Lesser General Public License restrictions do apply in
> +   other respects; for example, they cover modification of the file,
> +   and distribution when not linked into a combine executable.)
> +
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <libm-alias-float128.h>
> +
> +__float128
> +__fmaf128 (__float128 x, __float128 y, __float128 z)
> +{
> +  asm ("xsmaddqp\t%0, %1, %2" : "+v" (z) : "v" (x), "v" (y));
> +  return z;
> +}
> +
> +libm_alias_float128 (__fma, fma)
> 
I think you can 'x * y + z' here, at least GCC 6 optimizes it correctly [1].

[1] https://godbolt.org/z/pHSdDN

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