arch/mips/math-emu/dp_mul.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_mul(union ieee754dp x, union ieee754dp y)
  25 {
  26         int re;
  27         int rs;
  28         u64 rm;
  29         unsigned lxm;
  30         unsigned hxm;
  31         unsigned lym;
  32         unsigned 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
 105         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 106                 DPDNORMY;
 107                 break;
 108
 109         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 110                 DPDNORMX;
 111                 break;
 112
 113         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 114                 break;
 115         }
 116         /* rm = xm * ym, re = xe+ye basically */
 117         assert(xm & DP_HIDDEN_BIT);
 118         assert(ym & DP_HIDDEN_BIT);
 119
 120         re = xe + ye;
 121         rs = xs ^ ys;
 122
 123         /* shunt to top of word */
 124         xm <<= 64 - (DP_FBITS + 1);
 125         ym <<= 64 - (DP_FBITS + 1);
 126
 127         /*
 128          * Multiply 32 bits xm, ym to give high 32 bits rm with stickness.
 129          */
 130
 131         /* 32 * 32 => 64 */
 132 #define DPXMULT(x, y)   ((u64)(x) * (u64)y)
 133
 134         lxm = xm;
 135         hxm = xm >> 32;
 136         lym = ym;
 137         hym = ym >> 32;
 138
 139         lrm = DPXMULT(lxm, lym);
 140         hrm = DPXMULT(hxm, hym);
 141
 142         t = DPXMULT(lxm, hym);
 143
 144         at = lrm + (t << 32);
 145         hrm += at < lrm;
 146         lrm = at;
 147
 148         hrm = hrm + (t >> 32);
 149
 150         t = DPXMULT(hxm, lym);
 151
 152         at = 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          * Sticky shift down to normal rounding precision.
 162          */
 163         if ((s64) rm < 0) {
 164                 rm = (rm >> (64 - (DP_FBITS + 1 + 3))) |
 165                      ((rm << (DP_FBITS + 1 + 3)) != 0);
 166                         re++;
 167         } else {
 168                 rm = (rm >> (64 - (DP_FBITS + 1 + 3 + 1))) |
 169                      ((rm << (DP_FBITS + 1 + 3 + 1)) != 0);
 170         }
 171         assert(rm & (DP_HIDDEN_BIT << 3));
 172
 173         return ieee754dp_format(rs, re, rm);
 174 }