sysdeps/ieee754/ldbl-128ibm/s_remquol.c

   1 /* Compute remainder and a congruent to the quotient.
   2    Copyright (C) 1997-2024 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
  21 #include <math_private.h>
  22 #include <math_ldbl_opt.h>
  23
  24
  25 static const long double zero = 0.0;
  26
  27
  28 long double
  29 __remquol (long double x, long double y, int *quo)
  30 {
  31   int64_t hx,hy;
  32   uint64_t sx,lx,ly,qs;
  33   int cquo;
  34   double xhi, xlo, yhi, ylo;
  35
  36   ldbl_unpack (x, &xhi, &xlo);
  37   EXTRACT_WORDS64 (hx, xhi);
  38   EXTRACT_WORDS64 (lx, xlo);
  39   ldbl_unpack (y, &yhi, &ylo);
  40   EXTRACT_WORDS64 (hy, yhi);
  41   EXTRACT_WORDS64 (ly, ylo);
  42   sx = hx & 0x8000000000000000ULL;
  43   qs = sx ^ (hy & 0x8000000000000000ULL);
  44   ly ^= hy & 0x8000000000000000ULL;
  45   hy &= 0x7fffffffffffffffLL;
  46   lx ^= sx;
  47   hx &= 0x7fffffffffffffffLL;
  48
  49   /* Purge off exception values.  */
  50   if (hy == 0)
  51     return (x * y) / (x * y);                   /* y = 0 */
  52   if ((hx >= 0x7ff0000000000000LL)              /* x not finite */
  53       || (hy > 0x7ff0000000000000LL))           /* y is NaN */
  54     return (x * y) / (x * y);
  55
  56   if (hy <= 0x7fbfffffffffffffLL)
  57     x = __ieee754_fmodl (x, 8 * y);              /* now x < 8y */
  58
  59   if (((hx - hy) | (lx - ly)) == 0)
  60     {
  61       *quo = qs ? -1 : 1;
  62       return zero * x;
  63     }
  64
  65   x  = fabsl (x);
  66   y  = fabsl (y);
  67   cquo = 0;
  68
  69   if (hy <= 0x7fcfffffffffffffLL && x >= 4 * y)
  70     {
  71       x -= 4 * y;
  72       cquo += 4;
  73     }
  74   if (hy <= 0x7fdfffffffffffffLL && x >= 2 * y)
  75     {
  76       x -= 2 * y;
  77       cquo += 2;
  78     }
  79
  80   if (hy < 0x0020000000000000LL)
  81     {
  82       if (x + x > y)
  83         {
  84           x -= y;
  85           ++cquo;
  86           if (x + x >= y)
  87             {
  88               x -= y;
  89               ++cquo;
  90             }
  91         }
  92     }
  93   else
  94     {
  95       long double y_half = 0.5L * y;
  96       if (x > y_half)
  97         {
  98           x -= y;
  99           ++cquo;
 100           if (x >= y_half)
 101             {
 102               x -= y;
 103               ++cquo;
 104             }
 105         }
 106     }
 107
 108   *quo = qs ? -cquo : cquo;
 109
 110   /* Ensure correct sign of zero result in round-downward mode.  */
 111   if (x == 0.0L)
 112     x = 0.0L;
 113   if (sx)
 114     x = -x;
 115   return x;
 116 }
 117 long_double_symbol (libm, __remquol, remquol);