glibc/sysdeps/generic/get-rounding-mode.h

/* Determine floating-point rounding mode within libc.  Generic version.
   Copyright (C) 2012-2020 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
   <https://www.gnu.org/licenses/>.  */

#ifndef _GET_ROUNDING_MODE_H
#define _GET_ROUNDING_MODE_H	1

#include <fpu_control.h>
#include <stdlib.h>

/* Define values for FE_* modes not defined for this architecture.  */
#ifdef FE_DOWNWARD
# define ORIG_FE_DOWNWARD FE_DOWNWARD
#else
# define ORIG_FE_DOWNWARD 0
#endif
#ifdef FE_TONEAREST
# define ORIG_FE_TONEAREST FE_TONEAREST
#else
# define ORIG_FE_TONEAREST 0
#endif
#ifdef FE_TOWARDZERO
# define ORIG_FE_TOWARDZERO FE_TOWARDZERO
#else
# define ORIG_FE_TOWARDZERO 0
#endif
#ifdef FE_UPWARD
# define ORIG_FE_UPWARD FE_UPWARD
#else
# define ORIG_FE_UPWARD 0
#endif
#define FE_CONSTRUCT_DISTINCT_VALUE(X, Y, Z) \
  ((((X) & 1) | ((Y) & 2) | ((Z) & 4)) ^ 7)
#ifndef FE_DOWNWARD
# define FE_DOWNWARD FE_CONSTRUCT_DISTINCT_VALUE (ORIG_FE_TONEAREST,	\
						  ORIG_FE_TOWARDZERO,	\
						  ORIG_FE_UPWARD)
#endif
#ifndef FE_TONEAREST
# define FE_TONEAREST FE_CONSTRUCT_DISTINCT_VALUE (FE_DOWNWARD,		\
						   ORIG_FE_TOWARDZERO,	\
						   ORIG_FE_UPWARD)
#endif
#ifndef FE_TOWARDZERO
# define FE_TOWARDZERO FE_CONSTRUCT_DISTINCT_VALUE (FE_DOWNWARD,	\
						    FE_TONEAREST,	\
						    ORIG_FE_UPWARD)
#endif
#ifndef FE_UPWARD
# define FE_UPWARD FE_CONSTRUCT_DISTINCT_VALUE (FE_DOWNWARD,	\
						FE_TONEAREST,	\
						FE_TOWARDZERO)
#endif

/* Return the floating-point rounding mode.  */

static inline int
get_rounding_mode (void)
{
#if (defined _FPU_RC_DOWN			\
     || defined _FPU_RC_NEAREST			\
     || defined _FPU_RC_ZERO			\
     || defined _FPU_RC_UP)
  fpu_control_t fc;
  const fpu_control_t mask = (0
# ifdef _FPU_RC_DOWN
			      | _FPU_RC_DOWN
# endif
# ifdef _FPU_RC_NEAREST
			      | _FPU_RC_NEAREST
# endif
# ifdef _FPU_RC_ZERO
			      | _FPU_RC_ZERO
# endif
# ifdef _FPU_RC_UP
			      | _FPU_RC_UP
# endif
			      );

  _FPU_GETCW (fc);
  switch (fc & mask)
    {
# ifdef _FPU_RC_DOWN
    case _FPU_RC_DOWN:
      return FE_DOWNWARD;
# endif

# ifdef _FPU_RC_NEAREST
    case _FPU_RC_NEAREST:
      return FE_TONEAREST;
# endif

# ifdef _FPU_RC_ZERO
    case _FPU_RC_ZERO:
      return FE_TOWARDZERO;
# endif

# ifdef _FPU_RC_UP
    case _FPU_RC_UP:
      return FE_UPWARD;
# endif

    default:
      abort ();
    }
#else
  return FE_TONEAREST;
#endif
}

#endif /* get-rounding-mode.h */