sysdeps/ieee754/ldbl-96/s_remquol.c

   1 /* Compute remainder and a congruent to the quotient.
   2    Copyright (C) 1997-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <math.h>
  21
  22 #include <math_private.h>
  23
  24
  25 static const long double zero = 0.0;
  26
  27
  28 long double
  29 __remquol (long double x, long double p, int *quo)
  30 {
  31   int32_t ex,ep,hx,hp;
  32   u_int32_t sx,lx,lp;
  33   int cquo,qs;
  34
  35   GET_LDOUBLE_WORDS (ex, hx, lx, x);
  36   GET_LDOUBLE_WORDS (ep, hp, lp, p);
  37   sx = ex & 0x8000;
  38   qs = (sx ^ (ep & 0x8000)) >> 15;
  39   ep &= 0x7fff;
  40   ex &= 0x7fff;
  41
  42   /* Purge off exception values.  */
  43   if ((ep | hp | lp) == 0)
  44     return (x * p) / (x * p);                   /* p = 0 */
  45   if ((ex == 0x7fff)                            /* x not finite */
  46       || ((ep == 0x7fff)                        /* p is NaN */
  47           && ((hp | lp) != 0)))
  48     return (x * p) / (x * p);
  49
  50   if (ep <= 0x7ffb)
  51     x = __ieee754_fmodl (x, 8 * p);             /* now x < 8p */
  52
  53   if (((ex - ep) | (hx - hp) | (lx - lp)) == 0)
  54     {
  55       *quo = qs ? -1 : 1;
  56       return zero * x;
  57     }
  58
  59   x  = fabsl (x);
  60   p  = fabsl (p);
  61   cquo = 0;
  62
  63   if (x >= 4 * p)
  64     {
  65       x -= 4 * p;
  66       cquo += 4;
  67     }
  68   if (x >= 2 * p)
  69     {
  70       x -= 2 * p;
  71       cquo += 2;
  72     }
  73
  74   if (ep < 0x0002)
  75     {
  76       if (x + x > p)
  77         {
  78           x -= p;
  79           ++cquo;
  80           if (x + x >= p)
  81             {
  82               x -= p;
  83               ++cquo;
  84             }
  85         }
  86     }
  87   else
  88     {
  89       long double p_half = 0.5 * p;
  90       if (x > p_half)
  91         {
  92           x -= p;
  93           ++cquo;
  94           if (x >= p_half)
  95             {
  96               x -= p;
  97               ++cquo;
  98             }
  99         }
 100     }
 101
 102   *quo = qs ? -cquo : cquo;
 103
 104   if (sx)
 105     x = -x;
 106   return x;
 107 }
 108 weak_alias (__remquol, remquol)