libquadmath/math/issignalingq.c

   1 /* Test for signaling NaN.
   2    Copyright (C) 2013-2018 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 #include "quadmath-imp.h"
  20
  21 int
  22 issignalingq (__float128 x)
  23 {
  24   uint64_t hxi, lxi __attribute__ ((unused));
  25   GET_FLT128_WORDS64 (hxi, lxi, x);
  26 #if HIGH_ORDER_BIT_IS_SET_FOR_SNAN
  27   /* We only have to care about the high-order bit of x's significand, because
  28      having it set (sNaN) already makes the significand different from that
  29      used to designate infinity.  */
  30   return ((hxi & UINT64_C (0x7fff800000000000))
  31           == UINT64_C (0x7fff800000000000));
  32 #else
  33   /* To keep the following comparison simple, toggle the quiet/signaling bit,
  34      so that it is set for sNaNs.  This is inverse to IEEE 754-2008 (as well as
  35      common practice for IEEE 754-1985).  */
  36   hxi ^= UINT64_C (0x0000800000000000);
  37   /* If lxi != 0, then set any suitable bit of the significand in hxi.  */
  38   hxi |= (lxi | -lxi) >> 63;
  39   /* We have to compare for greater (instead of greater or equal), because x's
  40      significand being all-zero designates infinity not NaN.  */
  41   return (hxi & UINT64_C (0x7fffffffffffffff)) > UINT64_C (0x7fff800000000000);
  42 #endif
  43 }