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  *
   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 "ieee754sp.h"
  23
  24 union ieee754sp ieee754sp_mul(union ieee754sp x, union ieee754sp y)
  25 {
  26         int re;
  27         int rs;
  28         unsigned rm;
  29         unsigned short lxm;
  30         unsigned short hxm;
  31         unsigned short lym;
  32         unsigned short hym;
  33         unsigned lrm;
  34         unsigned hrm;
  35         unsigned t;
  36         unsigned at;
  37
  38         COMPXSP;
  39         COMPYSP;
  40
  41         EXPLODEXSP;
  42         EXPLODEYSP;
  43
  44         ieee754_clearcx();
  45
  46         FLUSHXSP;
  47         FLUSHYSP;
  48
  49         switch (CLPAIR(xc, yc)) {
  50         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  51         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  52         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  53         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  54         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  55         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  56         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  57         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  58         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  59         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  60         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  61                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  62                 return ieee754sp_nanxcpt(ieee754sp_indef());
  63
  64         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  65         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  66         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  67         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  68                 return y;
  69
  70         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  71         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  72         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  73         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  74         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  75                 return x;
  76
  77
  78         /*
  79          * Infinity handling
  80          */
  81         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  82         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  83                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  84                 return ieee754sp_indef();
  85
  86         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  87         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  88         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  89         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  90         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  91                 return ieee754sp_inf(xs ^ ys);
  92
  93         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  94         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  95         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  96         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  97         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  98                 return ieee754sp_zero(xs ^ ys);
  99
 100
 101         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 102                 SPDNORMX;
 103
 104         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 105                 SPDNORMY;
 106                 break;
 107
 108         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 109                 SPDNORMX;
 110                 break;
 111
 112         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 113                 break;
 114         }
 115         /* rm = xm * ym, re = xe+ye basically */
 116         assert(xm & SP_HIDDEN_BIT);
 117         assert(ym & SP_HIDDEN_BIT);
 118
 119         re = xe + ye;
 120         rs = xs ^ ys;
 121
 122         /* shunt to top of word */
 123         xm <<= 32 - (SP_FBITS + 1);
 124         ym <<= 32 - (SP_FBITS + 1);
 125
 126         /*
 127          * Multiply 32 bits xm, ym to give high 32 bits rm with stickness.
 128          */
 129         lxm = xm & 0xffff;
 130         hxm = xm >> 16;
 131         lym = ym & 0xffff;
 132         hym = ym >> 16;
 133
 134         lrm = lxm * lym;        /* 16 * 16 => 32 */
 135         hrm = hxm * hym;        /* 16 * 16 => 32 */
 136
 137         t = lxm * hym; /* 16 * 16 => 32 */
 138         at = lrm + (t << 16);
 139         hrm += at < lrm;
 140         lrm = at;
 141         hrm = hrm + (t >> 16);
 142
 143         t = hxm * lym; /* 16 * 16 => 32 */
 144         at = lrm + (t << 16);
 145         hrm += at < lrm;
 146         lrm = at;
 147         hrm = hrm + (t >> 16);
 148
 149         rm = hrm | (lrm != 0);
 150
 151         /*
 152          * Sticky shift down to normal rounding precision.
 153          */
 154         if ((int) rm < 0) {
 155                 rm = (rm >> (32 - (SP_FBITS + 1 + 3))) |
 156                     ((rm << (SP_FBITS + 1 + 3)) != 0);
 157                 re++;
 158         } else {
 159                 rm = (rm >> (32 - (SP_FBITS + 1 + 3 + 1))) |
 160                      ((rm << (SP_FBITS + 1 + 3 + 1)) != 0);
 161         }
 162         assert(rm & (SP_HIDDEN_BIT << 3));
 163
 164         return ieee754sp_format(rs, re, rm);
 165 }