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  * 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
  30 ieee754dp 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 }