arch/mips/math-emu/sp_mul.c

   1 /* IEEE754 floating point arithmetic
   2  * single precision
   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 "ieee754sp.h"
  29
  30 ieee754sp ieee754sp_mul(ieee754sp x, ieee754sp y)
  31 {
  32         COMPXSP;
  33         COMPYSP;
  34
  35         EXPLODEXSP;
  36         EXPLODEYSP;
  37
  38         CLEARCX;
  39
  40         FLUSHXSP;
  41         FLUSHYSP;
  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 ieee754sp_nanxcpt(ieee754sp_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 ieee754sp_xcpt(ieee754sp_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 ieee754sp_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 ieee754sp_zero(xs ^ ys);
  92
  93
  94         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  95                 SPDNORMX;
  96
  97         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  98                 SPDNORMY;
  99                 break;
 100
 101         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 102                 SPDNORMX;
 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 & SP_HIDDEN_BIT);
 110         assert(ym & SP_HIDDEN_BIT);
 111
 112         {
 113                 int re = xe + ye;
 114                 int rs = xs ^ ys;
 115                 unsigned rm;
 116
 117                 /* shunt to top of word */
 118                 xm <<= 32 - (SP_MBITS + 1);
 119                 ym <<= 32 - (SP_MBITS + 1);
 120
 121                 /* multiply 32bits xm,ym to give high 32bits rm with stickness
 122                  */
 123                 {
 124                         unsigned short lxm = xm & 0xffff;
 125                         unsigned short hxm = xm >> 16;
 126                         unsigned short lym = ym & 0xffff;
 127                         unsigned short hym = ym >> 16;
 128                         unsigned lrm;
 129                         unsigned hrm;
 130
 131                         lrm = lxm * lym;        /* 16 * 16 => 32 */
 132                         hrm = hxm * hym;        /* 16 * 16 => 32 */
 133
 134                         {
 135                                 unsigned t = lxm * hym; /* 16 * 16 => 32 */
 136                                 {
 137                                         unsigned at = lrm + (t << 16);
 138                                         hrm += at < lrm;
 139                                         lrm = at;
 140                                 }
 141                                 hrm = hrm + (t >> 16);
 142                         }
 143
 144                         {
 145                                 unsigned t = hxm * lym; /* 16 * 16 => 32 */
 146                                 {
 147                                         unsigned at = lrm + (t << 16);
 148                                         hrm += at < lrm;
 149                                         lrm = at;
 150                                 }
 151                                 hrm = hrm + (t >> 16);
 152                         }
 153                         rm = hrm | (lrm != 0);
 154                 }
 155
 156                 /*
 157                  * sticky shift down to normal rounding precision
 158                  */
 159                 if ((int) rm < 0) {
 160                         rm = (rm >> (32 - (SP_MBITS + 1 + 3))) |
 161                             ((rm << (SP_MBITS + 1 + 3)) != 0);
 162                         re++;
 163                 } else {
 164                         rm = (rm >> (32 - (SP_MBITS + 1 + 3 + 1))) |
 165                             ((rm << (SP_MBITS + 1 + 3 + 1)) != 0);
 166                 }
 167                 assert(rm & (SP_HIDDEN_BIT << 3));
 168
 169                 SPNORMRET2(rs, re, rm, "mul", x, y);
 170         }
 171 }