sysdeps/mips/bits/nan.h

   1 /* `NAN' constant for IEEE 754 machines.  MIPS version.
   2    Copyright (C) 1992-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _MATH_H
  20 # error "Never use <bits/nan.h> directly; include <math.h> instead."
  21 #endif
  22
  23
  24 /* IEEE Not A Number.  */
  25 /* In legacy-NaN mode MIPS has the qNaN and sNaN patterns reversed
  26    compared to most other architectures.  IEEE 754-1985 left the
  27    definition of this open to implementations, and for MIPS the top bit
  28    of the mantissa must be SET to indicate a sNaN.  In 2008-NaN mode
  29    MIPS aligned to IEEE 754-2008.  */
  30
  31 #if __GNUC_PREREQ(3,3)
  32
  33 # define NAN    (__builtin_nanf (""))
  34
  35 #elif defined __GNUC__
  36
  37 /* No 2008-NaN mode support in any GCC version before 4.9.  */
  38
  39 # define NAN \
  40   (__extension__                                                              \
  41    ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; })  \
  42     { __l: 0x7fbfffffUL }).__d)
  43
  44 #else
  45
  46 # include <endian.h>
  47
  48 # if __BYTE_ORDER == __BIG_ENDIAN
  49 #  ifdef __mips_nan2008
  50 #   define __qnan_bytes         { 0x7f, 0xc0, 0, 0 }
  51 #  else
  52 #   define __qnan_bytes         { 0x7f, 0xbf, 0xff, 0xff }
  53 #  endif
  54 # endif
  55 # if __BYTE_ORDER == __LITTLE_ENDIAN
  56 #  ifdef __mips_nan2008
  57 #   define __qnan_bytes         { 0, 0, 0xc0, 0x7f }
  58 #  else
  59 #   define __qnan_bytes         { 0xff, 0xff, 0xbf, 0x7f }
  60 #  endif
  61 # endif
  62
  63 static union { unsigned char __c[4]; float __d; } __qnan_union
  64   __attribute__ ((__unused__)) = { __qnan_bytes };
  65 # define NAN    (__qnan_union.__d)
  66
  67 #endif  /* GCC.  */