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

   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
  29ieee754dp ieee754dp_div(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(), "div", 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
  74        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  75                SETCX(IEEE754_INVALID_OPERATION);
  76                return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
  77
  78        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  79        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  80        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  81                return ieee754dp_zero(xs ^ ys);
  82
  83        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  84        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  85        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  86                return ieee754dp_inf(xs ^ ys);
  87
  88                /* Zero handling
  89                 */
  90
  91        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  92                SETCX(IEEE754_INVALID_OPERATION);
  93                return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
  94
  95        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  96        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  97                SETCX(IEEE754_ZERO_DIVIDE);
  98                return ieee754dp_xcpt(ieee754dp_inf(xs ^ ys), "div", x, y);
  99
 100        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 101        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 102                return ieee754dp_zero(xs == ys ? 0 : 1);
 103
 104        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 105                DPDNORMX;
 106
 107        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 108                DPDNORMY;
 109                break;
 110
 111        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 112                DPDNORMX;
 113                break;
 114
 115        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 116                break;
 117        }
 118        assert(xm & DP_HIDDEN_BIT);
 119        assert(ym & DP_HIDDEN_BIT);
 120
 121        /* provide rounding space */
 122        xm <<= 3;
 123        ym <<= 3;
 124
 125        {
 126                /* now the dirty work */
 127
 128                u64 rm = 0;
 129                int re = xe - ye;
 130                u64 bm;
 131
 132                for (bm = DP_MBIT(DP_MBITS + 2); bm; bm >>= 1) {
 133                        if (xm >= ym) {
 134                                xm -= ym;
 135                                rm |= bm;
 136                                if (xm == 0)
 137                                        break;
 138                        }
 139                        xm <<= 1;
 140                }
 141                rm <<= 1;
 142                if (xm)
 143                        rm |= 1;        /* have remainder, set sticky */
 144
 145                assert(rm);
 146
 147                /* normalise rm to rounding precision ?
 148                 */
 149                while ((rm >> (DP_MBITS + 3)) == 0) {
 150                        rm <<= 1;
 151                        re--;
 152                }
 153
 154                DPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);
 155        }
 156}
 157