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

   1 /* Compute remainder and a congruent to the quotient.
   2    Copyright (C) 1997,1999,2002,2004,2006 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   u_int64_t sx,lx,ly,qs;
  35   int cquo;
  36
  37   GET_LDOUBLE_WORDS64 (hx, lx, x);
  38   GET_LDOUBLE_WORDS64 (hy, ly, y);
  39   sx = hx & 0x8000000000000000ULL;
  40   qs = sx ^ (hy & 0x8000000000000000ULL);
  41   hy &= 0x7fffffffffffffffLL;
  42   hx &= 0x7fffffffffffffffLL;
  43
  44   /* Purge off exception values.  */
  45   if ((hy | (ly & 0x7fffffffffffffff)) == 0)
  46     return (x * y) / (x * y);                   /* y = 0 */
  47   if ((hx >= 0x7ff0000000000000LL)              /* x not finite */
  48       || ((hy >= 0x7ff0000000000000LL)          /* y is NaN */
  49           && (((hy - 0x7ff0000000000000LL) | ly) != 0)))
  50     return (x * y) / (x * y);
  51
  52   if (hy <= 0x7fbfffffffffffffLL)
  53     x = __ieee754_fmodl (x, 8 * y);              /* now x < 8y */
  54
  55   if (((hx - hy) | (lx - ly)) == 0)
  56     {
  57       *quo = qs ? -1 : 1;
  58       return zero * x;
  59     }
  60
  61   x  = fabsl (x);
  62   y  = fabsl (y);
  63   cquo = 0;
  64
  65   if (x >= 4 * y)
  66     {
  67       x -= 4 * y;
  68       cquo += 4;
  69     }
  70   if (x >= 2 * y)
  71     {
  72       x -= 2 * y;
  73       cquo += 2;
  74     }
  75
  76   if (hy < 0x0020000000000000LL)
  77     {
  78       if (x + x > y)
  79         {
  80           x -= y;
  81           ++cquo;
  82           if (x + x >= y)
  83             {
  84               x -= y;
  85               ++cquo;
  86             }
  87         }
  88     }
  89   else
  90     {
  91       long double y_half = 0.5L * y;
  92       if (x > y_half)
  93         {
  94           x -= y;
  95           ++cquo;
  96           if (x >= y_half)
  97             {
  98               x -= y;
  99               ++cquo;
 100             }
 101         }
 102     }
 103
 104   *quo = qs ? -cquo : cquo;
 105
 106   if (sx)
 107     x = -x;
 108   return x;
 109 }
 110 long_double_symbol (libm, __remquol, remquol);