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, write to the Free
  19    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  20    02111-1307 USA.  */
  21
  22 #include <math.h>
  23
  24 #include "math_private.h"
  25 #include <math_ldbl_opt.h>
  26
  27
  28 static const long double zero = 0.0;
  29
  30
  31 long double
  32 __remquol (long double x, long double y, int *quo)
  33 {
  34   int64_t hx,hy;
  35   u_int64_t sx,lx,ly,qs;
  36   int cquo;
  37
  38   GET_LDOUBLE_WORDS64 (hx, lx, x);
  39   GET_LDOUBLE_WORDS64 (hy, ly, y);
  40   sx = hx & 0x8000000000000000ULL;
  41   qs = sx ^ (hy & 0x8000000000000000ULL);
  42   hy &= 0x7fffffffffffffffLL;
  43   hx &= 0x7fffffffffffffffLL;
  44
  45   /* Purge off exception values.  */
  46   if ((hy | (ly & 0x7fffffffffffffff)) == 0)
  47     return (x * y) / (x * y);                   /* y = 0 */
  48   if ((hx >= 0x7ff0000000000000LL)              /* x not finite */
  49       || ((hy >= 0x7ff0000000000000LL)          /* y is NaN */
  50           && (((hy - 0x7ff0000000000000LL) | ly) != 0)))
  51     return (x * y) / (x * y);
  52
  53   if (hy <= 0x7fbfffffffffffffLL)
  54     x = __ieee754_fmodl (x, 8 * y);              /* now x < 8y */
  55
  56   if (((hx - hy) | (lx - ly)) == 0)
  57     {
  58       *quo = qs ? -1 : 1;
  59       return zero * x;
  60     }
  61
  62   x  = fabsl (x);
  63   y  = fabsl (y);
  64   cquo = 0;
  65
  66   if (x >= 4 * y)
  67     {
  68       x -= 4 * y;
  69       cquo += 4;
  70     }
  71   if (x >= 2 * y)
  72     {
  73       x -= 2 * y;
  74       cquo += 2;
  75     }
  76
  77   if (hy < 0x0020000000000000LL)
  78     {
  79       if (x + x > y)
  80         {
  81           x -= y;
  82           ++cquo;
  83           if (x + x >= y)
  84             {
  85               x -= y;
  86               ++cquo;
  87             }
  88         }
  89     }
  90   else
  91     {
  92       long double y_half = 0.5L * y;
  93       if (x > y_half)
  94         {
  95           x -= y;
  96           ++cquo;
  97           if (x >= y_half)
  98             {
  99               x -= y;
 100               ++cquo;
 101             }
 102         }
 103     }
 104
 105   *quo = qs ? -cquo : cquo;
 106
 107   if (sx)
 108     x = -x;
 109   return x;
 110 }
 111 long_double_symbol (libm, __remquol, remquol);