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

   1 /* Compute remainder and a congruent to the quotient.
   2    Copyright (C) 1997-2019 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997 and
   5                   Jakub Jelinek <jj@ultra.linux.cz>, 1999.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 #include <math.h>
  22
  23 #include <math_private.h>
  24 #include <math_ldbl_opt.h>
  25
  26
  27 static const long double zero = 0.0;
  28
  29
  30 long double
  31 __remquol (long double x, long double y, int *quo)
  32 {
  33   int64_t hx,hy;
  34   uint64_t sx,lx,ly,qs;
  35   int cquo;
  36   double xhi, xlo, yhi, ylo;
  37
  38   ldbl_unpack (x, &xhi, &xlo);
  39   EXTRACT_WORDS64 (hx, xhi);
  40   EXTRACT_WORDS64 (lx, xlo);
  41   ldbl_unpack (y, &yhi, &ylo);
  42   EXTRACT_WORDS64 (hy, yhi);
  43   EXTRACT_WORDS64 (ly, ylo);
  44   sx = hx & 0x8000000000000000ULL;
  45   qs = sx ^ (hy & 0x8000000000000000ULL);
  46   ly ^= hy & 0x8000000000000000ULL;
  47   hy &= 0x7fffffffffffffffLL;
  48   lx ^= sx;
  49   hx &= 0x7fffffffffffffffLL;
  50
  51   /* Purge off exception values.  */
  52   if (hy == 0)
  53     return (x * y) / (x * y);                   /* y = 0 */
  54   if ((hx >= 0x7ff0000000000000LL)              /* x not finite */
  55       || (hy > 0x7ff0000000000000LL))           /* y is NaN */
  56     return (x * y) / (x * y);
  57
  58   if (hy <= 0x7fbfffffffffffffLL)
  59     x = __ieee754_fmodl (x, 8 * y);              /* now x < 8y */
  60
  61   if (((hx - hy) | (lx - ly)) == 0)
  62     {
  63       *quo = qs ? -1 : 1;
  64       return zero * x;
  65     }
  66
  67   x  = fabsl (x);
  68   y  = fabsl (y);
  69   cquo = 0;
  70
  71   if (hy <= 0x7fcfffffffffffffLL && x >= 4 * y)
  72     {
  73       x -= 4 * y;
  74       cquo += 4;
  75     }
  76   if (hy <= 0x7fdfffffffffffffLL && x >= 2 * y)
  77     {
  78       x -= 2 * y;
  79       cquo += 2;
  80     }
  81
  82   if (hy < 0x0020000000000000LL)
  83     {
  84       if (x + x > y)
  85         {
  86           x -= y;
  87           ++cquo;
  88           if (x + x >= y)
  89             {
  90               x -= y;
  91               ++cquo;
  92             }
  93         }
  94     }
  95   else
  96     {
  97       long double y_half = 0.5L * y;
  98       if (x > y_half)
  99         {
 100           x -= y;
 101           ++cquo;
 102           if (x >= y_half)
 103             {
 104               x -= y;
 105               ++cquo;
 106             }
 107         }
 108     }
 109
 110   *quo = qs ? -cquo : cquo;
 111
 112   /* Ensure correct sign of zero result in round-downward mode.  */
 113   if (x == 0.0L)
 114     x = 0.0L;
 115   if (sx)
 116     x = -x;
 117   return x;
 118 }
 119 long_double_symbol (libm, __remquol, remquol);