1  /* Test for signaling NaN.
       2     Copyright (C) 2013-2023 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     <https://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  __issignalingl (long double x)
      25  {
      26    uint64_t xi;
      27    /* For inspecting NaN status, we only have to look at the first of the pair
      28       of IEEE 754 64-bit precision numbers.  */
      29    double xhi;
      30  
      31    xhi = ldbl_high (x);
      32    EXTRACT_WORDS64 (xi, xhi);
      33  #if HIGH_ORDER_BIT_IS_SET_FOR_SNAN
      34  # error untested
      35    /* We only have to care about the high-order bit of x's significand, because
      36       having it set (sNaN) already makes the significand different from that
      37       used to designate infinity.  */
      38    return (xi & UINT64_C (0x7ff8000000000000)) == UINT64_C (0x7ff8000000000000);
      39  #else
      40    /* To keep the following comparison simple, toggle the quiet/signaling bit,
      41       so that it is set for sNaNs.  This is inverse to IEEE 754-2008 (as well as
      42       common practice for IEEE 754-1985).  */
      43    xi ^= UINT64_C (0x0008000000000000);
      44    /* We have to compare for greater (instead of greater or equal), because x's
      45       significand being all-zero designates infinity not NaN.  */
      46    return (xi & UINT64_C (0x7fffffffffffffff)) > UINT64_C (0x7ff8000000000000);
      47  #endif
      48  }
      49  libm_hidden_def (__issignalingl)