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_mul(union ieee754dp x, union ieee754dp y)
  25{
  26        int re;
  27        int rs;
  28        u64 rm;
  29        unsigned int lxm;
  30        unsigned int hxm;
  31        unsigned int lym;
  32        unsigned int hym;
  33        u64 lrm;
  34        u64 hrm;
  35        u64 t;
  36        u64 at;
  37
  38        COMPXDP;
  39        COMPYDP;
  40
  41        EXPLODEXDP;
  42        EXPLODEYDP;
  43
  44        ieee754_clearcx();
  45
  46        FLUSHXDP;
  47        FLUSHYDP;
  48
  49        switch (CLPAIR(xc, yc)) {
  50        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  51        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  52        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  53        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  54        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  55                return ieee754dp_nanxcpt(y);
  56
  57        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  58        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  59        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  60        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  61        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  62        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  63                return ieee754dp_nanxcpt(x);
  64
  65        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  66        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  67        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  68        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  69                return y;
  70
  71        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  72        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  73        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  74        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  75        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  76                return x;
  77
  78
  79        /*
  80         * Infinity handling
  81         */
  82        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  83        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  84                ieee754_setcx(IEEE754_INVALID_OPERATION);
  85                return ieee754dp_indef();
  86
  87        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  88        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  89        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  90        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  91        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  92                return ieee754dp_inf(xs ^ ys);
  93
  94        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  95        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  96        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  97        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  98        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  99                return ieee754dp_zero(xs ^ ys);
 100
 101
 102        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 103                DPDNORMX;
 104                /* fall through */
 105
 106        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 107                DPDNORMY;
 108                break;
 109
 110        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 111                DPDNORMX;
 112                break;
 113
 114        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 115                break;
 116        }
 117        /* rm = xm * ym, re = xe+ye basically */
 118        assert(xm & DP_HIDDEN_BIT);
 119        assert(ym & DP_HIDDEN_BIT);
 120
 121        re = xe + ye;
 122        rs = xs ^ ys;
 123
 124        /* shunt to top of word */
 125        xm <<= 64 - (DP_FBITS + 1);
 126        ym <<= 64 - (DP_FBITS + 1);
 127
 128        /*
 129         * Multiply 64 bits xm, ym to give high 64 bits rm with stickness.
 130         */
 131
 132        lxm = xm;
 133        hxm = xm >> 32;
 134        lym = ym;
 135        hym = ym >> 32;
 136
 137        lrm = DPXMULT(lxm, lym);
 138        hrm = DPXMULT(hxm, hym);
 139
 140        t = DPXMULT(lxm, hym);
 141
 142        at = lrm + (t << 32);
 143        hrm += at < lrm;
 144        lrm = at;
 145
 146        hrm = hrm + (t >> 32);
 147
 148        t = DPXMULT(hxm, lym);
 149
 150        at = lrm + (t << 32);
 151        hrm += at < lrm;
 152        lrm = at;
 153
 154        hrm = hrm + (t >> 32);
 155
 156        rm = hrm | (lrm != 0);
 157
 158        /*
 159         * Sticky shift down to normal rounding precision.
 160         */
 161        if ((s64) rm < 0) {
 162                rm = (rm >> (64 - (DP_FBITS + 1 + 3))) |
 163                     ((rm << (DP_FBITS + 1 + 3)) != 0);
 164                re++;
 165        } else {
 166                rm = (rm >> (64 - (DP_FBITS + 1 + 3 + 1))) |
 167                     ((rm << (DP_FBITS + 1 + 3 + 1)) != 0);
 168        }
 169        assert(rm & (DP_HIDDEN_BIT << 3));
 170
 171        return ieee754dp_format(rs, re, rm);
 172}
 173