sysdeps/ieee754/dbl-64/s_issignaling.c

   1 /* Test for signaling NaN.
   2    Copyright (C) 2013-2015 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 #include <math.h>
  20 #include <math_private.h>
  21
  22 int
  23 __issignaling (double x)
  24 {
  25 #ifdef HIGH_ORDER_BIT_IS_SET_FOR_SNAN
  26   u_int32_t hxi;
  27   GET_HIGH_WORD (hxi, x);
  28   /* We only have to care about the high-order bit of x's significand, because
  29      having it set (sNaN) already makes the significand different from that
  30      used to designate infinity.  */
  31   return (hxi & 0x7ff80000) == 0x7ff80000;
  32 #else
  33   u_int32_t hxi, lxi;
  34   EXTRACT_WORDS (hxi, lxi, x);
  35   /* To keep the following comparison simple, toggle the quiet/signaling bit,
  36      so that it is set for sNaNs.  This is inverse to IEEE 754-2008 (as well as
  37      common practice for IEEE 754-1985).  */
  38   hxi ^= 0x00080000;
  39   /* If lxi != 0, then set any suitable bit of the significand in hxi.  */
  40   hxi |= (lxi | -lxi) >> 31;
  41   /* We have to compare for greater (instead of greater or equal), because x's
  42      significand being all-zero designates infinity not NaN.  */
  43   return (hxi & 0x7fffffff) > 0x7ff80000;
  44 #endif
  45 }
  46 libm_hidden_def (__issignaling)