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