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  }