Re: [PATCH 12/12] i386: Do not raise inexact exception on trunc/truncf

["H.J. Lu" <hjl.tools@gmail.com>]

On Thu, Dec 28, 2023 at 9:23 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> It is not allowed anymore on ISO C23.
>
> Checked on x86_64-linux-gnu and i686-linux-gnu.
> ---
>  sysdeps/i386/fpu/{s_trunc.S => s_trunc.c}   | 37 +++++++++++----------
>  sysdeps/i386/fpu/{s_truncf.S => s_truncf.c} | 37 +++++++++++----------
>  2 files changed, 38 insertions(+), 36 deletions(-)
>  rename sysdeps/i386/fpu/{s_trunc.S => s_trunc.c} (61%)
>  rename sysdeps/i386/fpu/{s_truncf.S => s_truncf.c} (61%)
>
> diff --git a/sysdeps/i386/fpu/s_trunc.S b/sysdeps/i386/fpu/s_trunc.c
> similarity index 61%
> rename from sysdeps/i386/fpu/s_trunc.S
> rename to sysdeps/i386/fpu/s_trunc.c
> index 145288bc8e..b071ad9750 100644
> --- a/sysdeps/i386/fpu/s_trunc.S
> +++ b/sysdeps/i386/fpu/s_trunc.c
> @@ -1,5 +1,5 @@
> -/* Truncate double value.
> -   Copyright (C) 1997-2023 Free Software Foundation, Inc.
> +/* Round to integer, toward zero.  i386 version.
> +   Copyright (C) 2023 Free Software Foundation, Inc.

2024.

>     This file is part of the GNU C Library.
>
>     The GNU C Library is free software; you can redistribute it and/or
> @@ -16,22 +16,23 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#include <machine/asm.h>
> +#define NO_MATH_REDIRECT
> +#include <math.h>
> +#include <fenv_private.h>
>  #include <libm-alias-double.h>
>
> -ENTRY(__trunc)
> -       fldl    4(%esp)
> -       subl    $32, %esp
> -       cfi_adjust_cfa_offset (32)
> -       fnstenv 4(%esp)
> -       movl    $0xc00, %edx
> -       orl     4(%esp), %edx
> -       movl    %edx, (%esp)
> -       fldcw   (%esp)
> -       frndint
> -       fldenv  4(%esp)
> -       addl    $32, %esp
> -       cfi_adjust_cfa_offset (-32)
> -       ret
> -END(__trunc)
> +double
> +__trunc (double x)
> +{
> +  fenv_t fenv;
> +  double r;
> +
> +  libc_feholdexcept_setround_387 (&fenv, FE_TOWARDZERO);
> +  asm volatile ("frndint" : "=t" (r) : "0" (x));
> +  /* Preserve "invalid" exceptions from sNaN input.  */
> +  fenv.__status_word |= libc_fetestexcept_387 (FE_INVALID);
> +  libc_fesetenv_387 (&fenv);
> +
> +  return r;
> +}
>  libm_alias_double (__trunc, trunc)
> diff --git a/sysdeps/i386/fpu/s_truncf.S b/sysdeps/i386/fpu/s_truncf.c
> similarity index 61%
> rename from sysdeps/i386/fpu/s_truncf.S
> rename to sysdeps/i386/fpu/s_truncf.c
> index 7bdf0e5111..86d46ff660 100644
> --- a/sysdeps/i386/fpu/s_truncf.S
> +++ b/sysdeps/i386/fpu/s_truncf.c
> @@ -1,5 +1,5 @@
> -/* Truncate float value.
> -   Copyright (C) 1997-2023 Free Software Foundation, Inc.
> +/* Round to integer, toward zero.  i386 version.
> +   Copyright (C) 2023 Free Software Foundation, Inc.

2024.

>     This file is part of the GNU C Library.
>
>     The GNU C Library is free software; you can redistribute it and/or
> @@ -16,22 +16,23 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#include <machine/asm.h>
> +#define NO_MATH_REDIRECT
> +#include <math.h>
> +#include <fenv_private.h>
>  #include <libm-alias-float.h>
>
> -ENTRY(__truncf)
> -       flds    4(%esp)
> -       subl    $32, %esp
> -       cfi_adjust_cfa_offset (32)
> -       fnstenv 4(%esp)
> -       movl    $0xc00, %edx
> -       orl     4(%esp), %edx
> -       movl    %edx, (%esp)
> -       fldcw   (%esp)
> -       frndint
> -       fldenv  4(%esp)
> -       addl    $32, %esp
> -       cfi_adjust_cfa_offset (-32)
> -       ret
> -END(__truncf)
> +float
> +__truncf (float x)
> +{
> +  fenv_t fenv;
> +  float r;
> +
> +  libc_feholdexcept_setround_387 (&fenv, FE_TOWARDZERO);
> +  asm volatile ("frndint" : "=t" (r) : "0" (x));
> +  /* Preserve "invalid" exceptions from sNaN input.  */
> +  fenv.__status_word |= libc_fetestexcept_387 (FE_INVALID);
> +  libc_fesetenv_387 (&fenv);
> +
> +  return r;
> +}
>  libm_alias_float (__trunc, trunc)
> --
> 2.34.1
>


-- 
H.J.