arch/mips/math-emu/dp_div.c

   1 /* IEEE754 floating point arithmetic
   2  * double precision: common utilities
   3  */
   4 /*
   5  * MIPS floating point support
   6  * Copyright (C) 1994-2000 Algorithmics Ltd.
   7  *
   8  *  This program is free software; you can distribute it and/or modify it
   9  *  under the terms of the GNU General Public License (Version 2) as
  10  *  published by the Free Software Foundation.
  11  *
  12  *  This program is distributed in the hope it will be useful, but WITHOUT
  13  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15  *  for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License along
  18  *  with this program; if not, write to the Free Software Foundation, Inc.,
  19  *  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
  20  */
  21
  22 #include "ieee754dp.h"
  23
  24 union ieee754dp ieee754dp_div(union ieee754dp x, union ieee754dp y)
  25 {
  26         u64 rm;
  27         int re;
  28         u64 bm;
  29
  30         COMPXDP;
  31         COMPYDP;
  32
  33         EXPLODEXDP;
  34         EXPLODEYDP;
  35
  36         ieee754_clearcx();
  37
  38         FLUSHXDP;
  39         FLUSHYDP;
  40
  41         switch (CLPAIR(xc, yc)) {
  42         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  43         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  44         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  45         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  46         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  47                 return ieee754dp_nanxcpt(y);
  48
  49         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  50         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  51         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  52         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  53         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  54         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  55                 return ieee754dp_nanxcpt(x);
  56
  57         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  58         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  59         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  60         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  61                 return y;
  62
  63         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  64         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  65         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  66         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  67         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  68                 return x;
  69
  70
  71         /*
  72          * Infinity handling
  73          */
  74         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  75                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  76                 return ieee754dp_indef();
  77
  78         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  79         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  80         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  81                 return ieee754dp_zero(xs ^ ys);
  82
  83         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  84         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  85         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  86                 return ieee754dp_inf(xs ^ ys);
  87
  88         /*
  89          * Zero handling
  90          */
  91         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  92                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  93                 return ieee754dp_indef();
  94
  95         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  96         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  97                 ieee754_setcx(IEEE754_ZERO_DIVIDE);
  98                 return ieee754dp_inf(xs ^ ys);
  99
 100         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 101         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 102                 return ieee754dp_zero(xs == ys ? 0 : 1);
 103
 104         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 105                 DPDNORMX;
 106                 /* fall through */
 107
 108         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 109                 DPDNORMY;
 110                 break;
 111
 112         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 113                 DPDNORMX;
 114                 break;
 115
 116         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 117                 break;
 118         }
 119         assert(xm & DP_HIDDEN_BIT);
 120         assert(ym & DP_HIDDEN_BIT);
 121
 122         /* provide rounding space */
 123         xm <<= 3;
 124         ym <<= 3;
 125
 126         /* now the dirty work */
 127
 128         rm = 0;
 129         re = xe - ye;
 130
 131         for (bm = DP_MBIT(DP_FBITS + 2); bm; bm >>= 1) {
 132                 if (xm >= ym) {
 133                         xm -= ym;
 134                         rm |= bm;
 135                         if (xm == 0)
 136                                 break;
 137                 }
 138                 xm <<= 1;
 139         }
 140
 141         rm <<= 1;
 142         if (xm)
 143                 rm |= 1;        /* have remainder, set sticky */
 144
 145         assert(rm);
 146
 147         /*
 148          * Normalise rm to rounding precision ?
 149          */
 150         while ((rm >> (DP_FBITS + 3)) == 0) {
 151                 rm <<= 1;
 152                 re--;
 153         }
 154
 155         return ieee754dp_format(xs == ys ? 0 : 1, re, rm);
 156 }