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  * ########################################################################
   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
  29 ieee754dp 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 }