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 * http://www.algor.co.uk
   8 *
   9 * ########################################################################
  10 *
  11 *  This program is free software; you can distribute it and/or modify it
  12 *  under the terms of the GNU General Public License (Version 2) as
  13 *  published by the Free Software Foundation.
  14 *
  15 *  This program is distributed in the hope it will be useful, but WITHOUT
  16 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  17 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  18 *  for more details.
  19 *
  20 *  You should have received a copy of the GNU General Public License along
  21 *  with this program; if not, write to the Free Software Foundation, Inc.,
  22 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
  23 *
  24 * ########################################################################
  25 */
  26
  27
  28#include "ieee754dp.h"
  29
  30ieee754dp ieee754dp_mul(ieee754dp x, ieee754dp y)
  31{
  32        COMPXDP;
  33        COMPYDP;
  34
  35        EXPLODEXDP;
  36        EXPLODEYDP;
  37
  38        CLEARCX;
  39
  40        FLUSHXDP;
  41        FLUSHYDP;
  42
  43        switch (CLPAIR(xc, yc)) {
  44        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  45        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  46        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  47        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  48        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  49        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  50        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  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                SETCX(IEEE754_INVALID_OPERATION);
  56                return ieee754dp_nanxcpt(ieee754dp_indef(), "mul", x, y);
  57
  58        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  59        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  60        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  61        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  62                return y;
  63
  64        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  65        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  66        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  67        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  68        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  69                return x;
  70
  71
  72                /* Infinity handling */
  73
  74        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  75        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  76                SETCX(IEEE754_INVALID_OPERATION);
  77                return ieee754dp_xcpt(ieee754dp_indef(), "mul", x, y);
  78
  79        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  80        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  81        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  82        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  83        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  84                return ieee754dp_inf(xs ^ ys);
  85
  86        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  87        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  88        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  89        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  90        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  91                return ieee754dp_zero(xs ^ ys);
  92
  93
  94        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  95                DPDNORMX;
  96
  97        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  98                DPDNORMY;
  99                break;
 100
 101        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 102                DPDNORMX;
 103                break;
 104
 105        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 106                break;
 107        }
 108        /* rm = xm * ym, re = xe+ye basicly */
 109        assert(xm & DP_HIDDEN_BIT);
 110        assert(ym & DP_HIDDEN_BIT);
 111        {
 112                int re = xe + ye;
 113                int rs = xs ^ ys;
 114                u64 rm;
 115
 116                /* shunt to top of word */
 117                xm <<= 64 - (DP_MBITS + 1);
 118                ym <<= 64 - (DP_MBITS + 1);
 119
 120                /* multiply 32bits xm,ym to give high 32bits rm with stickness
 121                 */
 122
 123                /* 32 * 32 => 64 */
 124#define DPXMULT(x, y)   ((u64)(x) * (u64)y)
 125
 126                {
 127                        unsigned lxm = xm;
 128                        unsigned hxm = xm >> 32;
 129                        unsigned lym = ym;
 130                        unsigned hym = ym >> 32;
 131                        u64 lrm;
 132                        u64 hrm;
 133
 134                        lrm = DPXMULT(lxm, lym);
 135                        hrm = DPXMULT(hxm, hym);
 136
 137                        {
 138                                u64 t = DPXMULT(lxm, hym);
 139                                {
 140                                        u64 at =
 141                                            lrm + (t << 32);
 142                                        hrm += at < lrm;
 143                                        lrm = at;
 144                                }
 145                                hrm = hrm + (t >> 32);
 146                        }
 147
 148                        {
 149                                u64 t = DPXMULT(hxm, lym);
 150                                {
 151                                        u64 at =
 152                                            lrm + (t << 32);
 153                                        hrm += at < lrm;
 154                                        lrm = at;
 155                                }
 156                                hrm = hrm + (t >> 32);
 157                        }
 158                        rm = hrm | (lrm != 0);
 159                }
 160
 161                /*
 162                 * sticky shift down to normal rounding precision
 163                 */
 164                if ((s64) rm < 0) {
 165                        rm =
 166                            (rm >> (64 - (DP_MBITS + 1 + 3))) |
 167                            ((rm << (DP_MBITS + 1 + 3)) != 0);
 168                        re++;
 169                } else {
 170                        rm =
 171                            (rm >> (64 - (DP_MBITS + 1 + 3 + 1))) |
 172                            ((rm << (DP_MBITS + 1 + 3 + 1)) != 0);
 173                }
 174                assert(rm & (DP_HIDDEN_BIT << 3));
 175                DPNORMRET2(rs, re, rm, "mul", x, y);
 176        }
 177}
 178