sysdeps/libm-ieee754/s_remquof.c

   1 /* Compute remainder and a congruent to the quotient.
   2    Copyright (C) 1997 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 Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    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    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <math.h>
  22
  23 #include "math_private.h"
  24
  25
  26 static const float zero = 0.0;
  27
  28
  29 float
  30 __remquof (float x, float y, int *quo)
  31 {
  32   int32_t hx,hy;
  33   u_int32_t sx;
  34   int cquo, qs;
  35
  36   GET_FLOAT_WORD (hx, x);
  37   GET_FLOAT_WORD (hy, y);
  38   sx = hx & 0x80000000;
  39   qs = sx ^ (hy & 0x80000000);
  40   hy &= 0x7fffffff;
  41   hx &= 0x7fffffff;
  42
  43   /* Purge off exception values.  */
  44   if (hy == 0)
  45     return (x * y) / (x * y);                   /* y = 0 */
  46   if ((hx >= 0x7f800000)                        /* x not finite */
  47       || (hy > 0x7f800000))                     /* y is NaN */
  48     return (x * y) / (x * y);
  49
  50   if (hy <= 0x7dffffff)
  51     x = __ieee754_fmodf (x, 8 * y);             /* now x < 8y */
  52
  53   if ((hx - hy) == 0)
  54     {
  55       *quo = qs ? -1 : 1;
  56       return zero * x;
  57     }
  58
  59   x  = fabsf (x);
  60   y  = fabsf (y);
  61   cquo = 0;
  62
  63   if (x >= 4 * y)
  64     {
  65       x -= 4 * y;
  66       cquo += 4;
  67     }
  68   if (x >= 2 * y)
  69     {
  70       x -= 2 * y;
  71       cquo += 2;
  72     }
  73
  74   if (hy < 0x01000000)
  75     {
  76       if (x + x > y)
  77         {
  78           x -= y;
  79           ++cquo;
  80           if (x + x >= y)
  81             {
  82               x -= y;
  83               ++cquo;
  84             }
  85         }
  86     }
  87   else
  88     {
  89       float y_half = 0.5 * y;
  90       if (x > y_half)
  91         {
  92           x -= y;
  93           ++cquo;
  94           if (x >= y_half)
  95             {
  96               x -= y;
  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 (__remquof, remquof)