LXR linux/arch/mips/math-emu/sp

   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
  24union 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_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_zero(xs ^ ys);
 100
 101
 102        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 103                SPDNORMX;
 104
 105        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 106                SPDNORMY;
 107                break;
 108
 109        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 110                SPDNORMX;
 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 & SP_HIDDEN_BIT);
 118        assert(ym & SP_HIDDEN_BIT);
 119
 120        re = xe + ye;
 121        rs = xs ^ ys;
 122
 123        /* shunt to top of word */
 124        xm <<= 32 - (SP_FBITS + 1);
 125        ym <<= 32 - (SP_FBITS + 1);
 126
 127        /*
 128         * Multiply 32 bits xm, ym to give high 32 bits rm with stickness.
 129         */
 130        lxm = xm & 0xffff;
 131        hxm = xm >> 16;
 132        lym = ym & 0xffff;
 133        hym = ym >> 16;
 134
 135        lrm = lxm * lym;        /* 16 * 16 => 32 */
 136        hrm = hxm * hym;        /* 16 * 16 => 32 */
 137
 138        t = lxm * hym; /* 16 * 16 => 32 */
 139        at = lrm + (t << 16);
 140        hrm += at < lrm;
 141        lrm = at;
 142        hrm = hrm + (t >> 16);
 143
 144        t = hxm * lym; /* 16 * 16 => 32 */
 145        at = lrm + (t << 16);
 146        hrm += at < lrm;
 147        lrm = at;
 148        hrm = hrm + (t >> 16);
 149
 150        rm = hrm | (lrm != 0);
 151
 152        /*
 153         * Sticky shift down to normal rounding precision.
 154         */
 155        if ((int) rm < 0) {
 156                rm = (rm >> (32 - (SP_FBITS + 1 + 3))) |
 157                    ((rm << (SP_FBITS + 1 + 3)) != 0);
 158                re++;
 159        } else {
 160                rm = (rm >> (32 - (SP_FBITS + 1 + 3 + 1))) |
 161                     ((rm << (SP_FBITS + 1 + 3 + 1)) != 0);
 162        }
 163        assert(rm & (SP_HIDDEN_BIT << 3));
 164
 165        return ieee754sp_format(rs, re, rm);
 166}
 167