ap/libc/glibc/glibc-2.23/sysdeps/mips/bits/nan.h

/* `NAN' constant for IEEE 754 machines.  MIPS version.
   Copyright (C) 1992-2016 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/>.  */

#ifndef _MATH_H
# error "Never use <bits/nan.h> directly; include <math.h> instead."
#endif


/* IEEE Not A Number.  */
/* In legacy-NaN mode MIPS has the qNaN and sNaN patterns reversed
   compared to most other architectures.  IEEE 754-1985 left the
   definition of this open to implementations, and for MIPS the top bit
   of the mantissa must be SET to indicate a sNaN.  In 2008-NaN mode
   MIPS aligned to IEEE 754-2008.  */

#if __GNUC_PREREQ(3,3)

# define NAN	(__builtin_nanf (""))

#elif defined __GNUC__

/* No 2008-NaN mode support in any GCC version before 4.9.  */

# define NAN \
  (__extension__							      \
   ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; })  \
    { __l: 0x7fbfffffUL }).__d)

#else

# include <endian.h>

# if __BYTE_ORDER == __BIG_ENDIAN
#  ifdef __mips_nan2008
#   define __qnan_bytes		{ 0x7f, 0xc0, 0, 0 }
#  else
#   define __qnan_bytes		{ 0x7f, 0xbf, 0xff, 0xff }
#  endif
# endif
# if __BYTE_ORDER == __LITTLE_ENDIAN
#  ifdef __mips_nan2008
#   define __qnan_bytes		{ 0, 0, 0xc0, 0x7f }
#  else
#   define __qnan_bytes		{ 0xff, 0xff, 0xbf, 0x7f }
#  endif
# endif

static union { unsigned char __c[4]; float __d; } __qnan_union
  __attribute__ ((__unused__)) = { __qnan_bytes };
# define NAN	(__qnan_union.__d)

#endif	/* GCC.  */