[PATCH 10/13] s390: Use sqrt{f} builtin

Stefan Liebler stli@linux.ibm.com
Wed Jun 10 15:39:40 GMT 2020


Hi Adhemerval,

my last tests with the sqrt builtin on s390x showed that gcc emits a
call to libm which would lead to an infinite loop:
if (x < 0)
 sqrt(x)
else
 sqdbr-instruction

Can you have a look into the generated code?
I will also apply your series and perform some test-runs. (next week as
I'll be on vacation the next days)

Then I'll also have a look at the fma-builtins. But those should be fine
for float and double.

Bye.
Stefan

On 6/9/20 11:32 PM, Adhemerval Zanella via Libc-alpha wrote:
> Checked on s390x-linux-gnu.
> ---
>  sysdeps/s390/fpu/e_sqrt.c                 | 30 -----------------------
>  sysdeps/s390/fpu/e_sqrtf.c                | 30 -----------------------
>  sysdeps/s390/fpu/math-use-builtins-sqrt.h |  4 +++
>  3 files changed, 4 insertions(+), 60 deletions(-)
>  delete mode 100644 sysdeps/s390/fpu/e_sqrt.c
>  delete mode 100644 sysdeps/s390/fpu/e_sqrtf.c
>  create mode 100644 sysdeps/s390/fpu/math-use-builtins-sqrt.h
> 
> diff --git a/sysdeps/s390/fpu/e_sqrt.c b/sysdeps/s390/fpu/e_sqrt.c
> deleted file mode 100644
> index 484c6aae95..0000000000
> --- a/sysdeps/s390/fpu/e_sqrt.c
> +++ /dev/null
> @@ -1,30 +0,0 @@
> -/* Copyright (C) 2004-2020 Free Software Foundation, Inc.
> -   Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>.
> -   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 <math_private.h>
> -#include <libm-alias-finite.h>
> -
> -double
> -__ieee754_sqrt (double x)
> -{
> -  double res;
> -
> -  __asm__ ( "sqdbr %0,%1" : "=f" (res) : "f" (x) );
> -  return res;
> -}
> -libm_alias_finite (__ieee754_sqrt, __sqrt)
> diff --git a/sysdeps/s390/fpu/e_sqrtf.c b/sysdeps/s390/fpu/e_sqrtf.c
> deleted file mode 100644
> index bce49c90f1..0000000000
> --- a/sysdeps/s390/fpu/e_sqrtf.c
> +++ /dev/null
> @@ -1,30 +0,0 @@
> -/* Copyright (C) 2004-2020 Free Software Foundation, Inc.
> -   Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>.
> -   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 <math_private.h>
> -#include <libm-alias-finite.h>
> -
> -float
> -__ieee754_sqrtf (float x)
> -{
> -  float res;
> -
> -  __asm__ ( "sqebr %0,%1" : "=f" (res) : "f" (x) );
> -  return res;
> -}
> -libm_alias_finite (__ieee754_sqrtf, __sqrtf)
> diff --git a/sysdeps/s390/fpu/math-use-builtins-sqrt.h b/sysdeps/s390/fpu/math-use-builtins-sqrt.h
> new file mode 100644
> index 0000000000..e94c915ba6
> --- /dev/null
> +++ b/sysdeps/s390/fpu/math-use-builtins-sqrt.h
> @@ -0,0 +1,4 @@
> +#define USE_SQRT_BUILTIN 1
> +#define USE_SQRTF_BUILTIN 1
> +#define USE_SQRTL_BUILTIN 0
> +#define USE_SQRTF128_BUILTIN 0
> 



More information about the Libc-alpha mailing list