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 * ########################################################################
   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 "ieee754sp.h"
  28
  29ieee754sp ieee754sp_mul(ieee754sp x, ieee754sp y)
  30{
  31        COMPXSP;
  32        COMPYSP;
  33
  34        EXPLODEXSP;
  35        EXPLODEYSP;
  36
  37        CLEARCX;
  38
  39        FLUSHXSP;
  40        FLUSHYSP;
  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 ieee754sp_nanxcpt(ieee754sp_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 ieee754sp_xcpt(ieee754sp_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 ieee754sp_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 ieee754sp_zero(xs ^ ys);
  91
  92
  93        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  94                SPDNORMX;
  95
  96        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  97                SPDNORMY;
  98                break;
  99
 100        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 101                SPDNORMX;
 102                break;
 103
 104        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 105                break;
 106        }
 107        /* rm = xm * ym, re = xe+ye basicly */
 108        assert(xm & SP_HIDDEN_BIT);
 109        assert(ym & SP_HIDDEN_BIT);
 110
 111        {
 112                int re = xe + ye;
 113                int rs = xs ^ ys;
 114                unsigned rm;
 115
 116                /* shunt to top of word */
 117                xm <<= 32 - (SP_MBITS + 1);
 118                ym <<= 32 - (SP_MBITS + 1);
 119
 120                /* multiply 32bits xm,ym to give high 32bits rm with stickness
 121                 */
 122                {
 123                        unsigned short lxm = xm & 0xffff;
 124                        unsigned short hxm = xm >> 16;
 125                        unsigned short lym = ym & 0xffff;
 126                        unsigned short hym = ym >> 16;
 127                        unsigned lrm;
 128                        unsigned hrm;
 129
 130                        lrm = lxm * lym;        /* 16 * 16 => 32 */
 131                        hrm = hxm * hym;        /* 16 * 16 => 32 */
 132
 133                        {
 134                                unsigned t = lxm * hym; /* 16 * 16 => 32 */
 135                                {
 136                                        unsigned at = lrm + (t << 16);
 137                                        hrm += at < lrm;
 138                                        lrm = at;
 139                                }
 140                                hrm = hrm + (t >> 16);
 141                        }
 142
 143                        {
 144                                unsigned t = hxm * lym; /* 16 * 16 => 32 */
 145                                {
 146                                        unsigned at = lrm + (t << 16);
 147                                        hrm += at < lrm;
 148                                        lrm = at;
 149                                }
 150                                hrm = hrm + (t >> 16);
 151                        }
 152                        rm = hrm | (lrm != 0);
 153                }
 154
 155                /*
 156                 * sticky shift down to normal rounding precision
 157                 */
 158                if ((int) rm < 0) {
 159                        rm = (rm >> (32 - (SP_MBITS + 1 + 3))) |
 160                            ((rm << (SP_MBITS + 1 + 3)) != 0);
 161                        re++;
 162                } else {
 163                        rm = (rm >> (32 - (SP_MBITS + 1 + 3 + 1))) |
 164                            ((rm << (SP_MBITS + 1 + 3 + 1)) != 0);
 165                }
 166                assert(rm & (SP_HIDDEN_BIT << 3));
 167
 168                SPNORMRET2(rs, re, rm, "mul", x, y);
 169        }
 170}
 171