sysdeps/ieee754/dbl-64/s_issignaling.c

   1 /* Test for signaling NaN.
   2    Copyright (C) 2013-2019 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 <math.h>
  20 #include <math_private.h>
  21 #include <nan-high-order-bit.h>
  22
  23 int
  24 __issignaling (double x)
  25 {
  26 #if HIGH_ORDER_BIT_IS_SET_FOR_SNAN
  27   uint32_t hxi;
  28   GET_HIGH_WORD (hxi, x);
  29   /* We only have to care about the high-order bit of x's significand, because
  30      having it set (sNaN) already makes the significand different from that
  31      used to designate infinity.  */
  32   return (hxi & 0x7ff80000) == 0x7ff80000;
  33 #else
  34   uint32_t hxi, lxi;
  35   EXTRACT_WORDS (hxi, lxi, x);
  36   /* To keep the following comparison simple, toggle the quiet/signaling bit,
  37      so that it is set for sNaNs.  This is inverse to IEEE 754-2008 (as well as
  38      common practice for IEEE 754-1985).  */
  39   hxi ^= 0x00080000;
  40   /* If lxi != 0, then set any suitable bit of the significand in hxi.  */
  41   hxi |= (lxi | -lxi) >> 31;
  42   /* We have to compare for greater (instead of greater or equal), because x's
  43      significand being all-zero designates infinity not NaN.  */
  44   return (hxi & 0x7fffffff) > 0x7ff80000;
  45 #endif
  46 }
  47 libm_hidden_def (__issignaling)