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 *  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 "ieee754dp.h"
  23
  24union ieee754dp ieee754dp_add(union ieee754dp x, union ieee754dp y)
  25{
  26        int s;
  27
  28        COMPXDP;
  29        COMPYDP;
  30
  31        EXPLODEXDP;
  32        EXPLODEYDP;
  33
  34        ieee754_clearcx();
  35
  36        FLUSHXDP;
  37        FLUSHYDP;
  38
  39        switch (CLPAIR(xc, yc)) {
  40        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  41        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  42        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  43        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  44        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  45                return ieee754dp_nanxcpt(y);
  46
  47        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  48        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  49        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  50        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  51        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  52        case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  53                return ieee754dp_nanxcpt(x);
  54
  55        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  56        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  57        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  58        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  59                return y;
  60
  61        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  62        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  63        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  64        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  65        case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  66                return x;
  67
  68
  69        /*
  70         * Infinity handling
  71         */
  72        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  73                if (xs == ys)
  74                        return x;
  75                ieee754_setcx(IEEE754_INVALID_OPERATION);
  76                return ieee754dp_indef();
  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 y;
  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 x;
  87
  88        /*
  89         * Zero handling
  90         */
  91        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  92                if (xs == ys)
  93                        return x;
  94                else
  95                        return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
  96
  97        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  98        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  99                return x;
 100
 101        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 102        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 103                return y;
 104
 105        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 106                DPDNORMX;
 107
 108                /* FALL THROUGH */
 109
 110        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 111                DPDNORMY;
 112                break;
 113
 114        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 115                DPDNORMX;
 116                break;
 117
 118        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 119                break;
 120        }
 121        assert(xm & DP_HIDDEN_BIT);
 122        assert(ym & DP_HIDDEN_BIT);
 123
 124        /*
 125         * Provide guard,round and stick bit space.
 126         */
 127        xm <<= 3;
 128        ym <<= 3;
 129
 130        if (xe > ye) {
 131                /*
 132                 * Have to shift y fraction right to align.
 133                 */
 134                s = xe - ye;
 135                ym = XDPSRS(ym, s);
 136                ye += s;
 137        } else if (ye > xe) {
 138                /*
 139                 * Have to shift x fraction right to align.
 140                 */
 141                s = ye - xe;
 142                xm = XDPSRS(xm, s);
 143                xe += s;
 144        }
 145        assert(xe == ye);
 146        assert(xe <= DP_EMAX);
 147
 148        if (xs == ys) {
 149                /*
 150                 * Generate 28 bit result of adding two 27 bit numbers
 151                 * leaving result in xm, xs and xe.
 152                 */
 153                xm = xm + ym;
 154
 155                if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */
 156                        xm = XDPSRS1(xm);
 157                        xe++;
 158                }
 159        } else {
 160                if (xm >= ym) {
 161                        xm = xm - ym;
 162                } else {
 163                        xm = ym - xm;
 164                        xs = ys;
 165                }
 166                if (xm == 0)
 167                        return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
 168
 169                /*
 170                 * Normalize to rounding precision.
 171                 */
 172                while ((xm >> (DP_FBITS + 3)) == 0) {
 173                        xm <<= 1;
 174                        xe--;
 175                }
 176        }
 177
 178        return ieee754dp_format(xs, xe, xm);
 179}
 180