1  /* Test whether long double value is canonical.  ldbl-128ibm 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 <math.h>
      20  #include <math_private.h>
      21  #include <stdint.h>
      22  
      23  int
      24  __iscanonicall (long double x)
      25  {
      26    double xhi, xlo;
      27    uint64_t hx, lx;
      28  
      29    ldbl_unpack (x, &xhi, &xlo);
      30    EXTRACT_WORDS64 (hx, xhi);
      31    EXTRACT_WORDS64 (lx, xlo);
      32    int64_t ix = hx & 0x7fffffffffffffffULL;
      33    int64_t iy = lx & 0x7fffffffffffffffULL;
      34    int hexp = (ix & 0x7ff0000000000000LL) >> 52;
      35    int lexp = (iy & 0x7ff0000000000000LL) >> 52;
      36  
      37    if (iy == 0)
      38      /* Low part 0 is always OK.  */
      39      return 1;
      40  
      41    if (hexp == 0x7ff)
      42      /* If a NaN, the low part does not matter.  If an infinity, the
      43         low part must be 0, in which case we have already returned.  */
      44      return ix != 0x7ff0000000000000LL;
      45  
      46    /* The high part is finite and the low part is nonzero.  There must
      47       be sufficient difference between the exponents.  */
      48    bool low_p2;
      49    if (lexp == 0)
      50      {
      51        /* Adjust the exponent for subnormal low part.  */
      52        lexp = 12 - __builtin_clzll (iy);
      53        low_p2 = iy == (1LL << (51 + lexp));
      54      }
      55    else
      56      low_p2 = (iy & 0xfffffffffffffLL) == 0;
      57    int expdiff = hexp - lexp;
      58    return expdiff > 53 || (expdiff == 53 && low_p2 && (ix & 1) == 0);
      59  }
      60  libm_hidden_def (__iscanonicall)