1  /* Test whether long double value is canonical.  ldbl-96 version.
       2     Copyright (C) 2016-2023 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 <float.h>
      20  #include <math.h>
      21  #include <math_private.h>
      22  #include <stdbool.h>
      23  #include <stdint.h>
      24  
      25  int
      26  __iscanonicall (long double x)
      27  {
      28    uint32_t se, i0, i1 __attribute__ ((unused));
      29  
      30    GET_LDOUBLE_WORDS (se, i0, i1, x);
      31    int32_t ix = se & 0x7fff;
      32    bool mant_high = (i0 & 0x80000000) != 0;
      33  
      34    if (LDBL_MIN_EXP == -16381)
      35      /* Intel variant: the high mantissa bit should have a value
      36         determined by the exponent.  */
      37      return ix > 0 ? mant_high : !mant_high;
      38    else
      39      /* M68K variant: both values of the high bit are valid for the
      40         greatest and smallest exponents, while other exponents require
      41         the high bit to be set.  */
      42      return ix == 0 || ix == 0x7fff || mant_high;
      43  }
      44  libm_hidden_def (__iscanonicall)