sysdeps/mips/bits/nan.h

   1 /* `NAN' constant for IEEE 754 machines.
   2    Copyright (C) 1992, 1996, 1997, 1999, 2002, 2004
   3    Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library.  If not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _MATH_H
  21 # error "Never use <bits/nan.h> directly; include <math.h> instead."
  22 #endif
  23
  24
  25 /* IEEE Not A Number (QNaN). Note that MIPS has the QNaN and SNaN patterns
  26    reversed compared to most other architectures. The IEEE spec left
  27    the definition of this open to implementations, and for MIPS the top
  28    bit of the mantissa must be SET to indicate a SNaN.  */
  29
  30 #if __GNUC_PREREQ(3,3)
  31
  32 # define NAN    (__builtin_nanf(""))
  33
  34 #elif defined __GNUC__
  35
  36 # define NAN \
  37   (__extension__                                                            \
  38    ((union { unsigned __l __attribute__((__mode__(__SI__))); float __d; })  \
  39     { __l: 0x7fbfffffUL }).__d)
  40
  41 #else
  42
  43 # include <endian.h>
  44
  45 # if __BYTE_ORDER == __BIG_ENDIAN
  46 #  define __nan_bytes           { 0x7f, 0xbf, 0xff, 0xff }
  47 # endif
  48 # if __BYTE_ORDER == __LITTLE_ENDIAN
  49 #  define __nan_bytes           { 0xff, 0xff, 0xbf, 0x7f }
  50 # endif
  51
  52 static union { unsigned char __c[4]; float __d; } __nan_union = { __nan_bytes };
  53 # define NAN    (__nan_union.__d)
  54
  55 #endif  /* GCC.  */