LXR linux/arch/mips/math-emu/dp

   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
  24union 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}
 157