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 * 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 "ieee754dp.h"
  29
  30ieee754dp ieee754dp_div(ieee754dp x, ieee754dp y)
  31{
  32        COMPXDP;
  33        COMPYDP;
  34
  35        EXPLODEXDP;
  36        EXPLODEYDP;
  37
  38        CLEARCX;
  39
  40        FLUSHXDP;
  41        FLUSHYDP;
  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 ieee754dp_nanxcpt(ieee754dp_indef(), "div", 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
  75        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  76                SETCX(IEEE754_INVALID_OPERATION);
  77                return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
  78
  79        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  80        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  81        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  82                return ieee754dp_zero(xs ^ ys);
  83
  84        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  85        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  86        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  87                return ieee754dp_inf(xs ^ ys);
  88
  89                /* Zero handling
  90                 */
  91
  92        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  93                SETCX(IEEE754_INVALID_OPERATION);
  94                return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
  95
  96        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  97        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  98                SETCX(IEEE754_ZERO_DIVIDE);
  99                return ieee754dp_xcpt(ieee754dp_inf(xs ^ ys), "div", x, y);
 100
 101        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 102        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 103                return ieee754dp_zero(xs == ys ? 0 : 1);
 104
 105        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 106                DPDNORMX;
 107
 108        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 109                DPDNORMY;
 110                break;
 111
 112        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 113                DPDNORMX;
 114                break;
 115
 116        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 117                break;
 118        }
 119        assert(xm & DP_HIDDEN_BIT);
 120        assert(ym & DP_HIDDEN_BIT);
 121
 122        /* provide rounding space */
 123        xm <<= 3;
 124        ym <<= 3;
 125
 126        {
 127                /* now the dirty work */
 128
 129                u64 rm = 0;
 130                int re = xe - ye;
 131                u64 bm;
 132
 133                for (bm = DP_MBIT(DP_MBITS + 2); bm; bm >>= 1) {
 134                        if (xm >= ym) {
 135                                xm -= ym;
 136                                rm |= bm;
 137                                if (xm == 0)
 138                                        break;
 139                        }
 140                        xm <<= 1;
 141                }
 142                rm <<= 1;
 143                if (xm)
 144                        rm |= 1;        /* have remainder, set sticky */
 145
 146                assert(rm);
 147
 148                /* normalise rm to rounding precision ?
 149                 */
 150                while ((rm >> (DP_MBITS + 3)) == 0) {
 151                        rm <<= 1;
 152                        re--;
 153                }
 154
 155                DPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);
 156        }
 157}
 158