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
  28#include "ieee754dp.h"
  29
  30ieee754dp ieee754dp_add(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(), "add", 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                if (xs == ys)
  77                        return x;
  78                SETCX(IEEE754_INVALID_OPERATION);
  79                return ieee754dp_xcpt(ieee754dp_indef(), "add", x, y);
  80
  81        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  82        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  83        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  84                return y;
  85
  86        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  87        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  88        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  89                return x;
  90
  91                /* Zero handling
  92                 */
  93
  94        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  95                if (xs == ys)
  96                        return x;
  97                else
  98                        return ieee754dp_zero(ieee754_csr.rm ==
  99                                              IEEE754_RD);
 100
 101        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
 102        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
 103                return x;
 104
 105        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 106        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 107                return y;
 108
 109        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 110                DPDNORMX;
 111
 112                /* FALL THROUGH */
 113
 114        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 115                DPDNORMY;
 116                break;
 117
 118        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 119                DPDNORMX;
 120                break;
 121
 122        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 123                break;
 124        }
 125        assert(xm & DP_HIDDEN_BIT);
 126        assert(ym & DP_HIDDEN_BIT);
 127
 128        /* provide guard,round and stick bit space */
 129        xm <<= 3;
 130        ym <<= 3;
 131
 132        if (xe > ye) {
 133                /* have to shift y fraction right to align
 134                 */
 135                int s = xe - ye;
 136                ym = XDPSRS(ym, s);
 137                ye += s;
 138        } else if (ye > xe) {
 139                /* have to shift x fraction right to align
 140                 */
 141                int 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                /* generate 28 bit result of adding two 27 bit numbers
 150                 * leaving result in xm,xs,xe
 151                 */
 152                xm = xm + ym;
 153                xe = xe;
 154                xs = xs;
 155
 156                if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */
 157                        xm = XDPSRS1(xm);
 158                        xe++;
 159                }
 160        } else {
 161                if (xm >= ym) {
 162                        xm = xm - ym;
 163                        xe = xe;
 164                        xs = xs;
 165                } else {
 166                        xm = ym - xm;
 167                        xe = xe;
 168                        xs = ys;
 169                }
 170                if (xm == 0)
 171                        return ieee754dp_zero(ieee754_csr.rm ==
 172                                              IEEE754_RD);
 173
 174                /* normalize to rounding precision */
 175                while ((xm >> (DP_MBITS + 3)) == 0) {
 176                        xm <<= 1;
 177                        xe--;
 178                }
 179
 180        }
 181        DPNORMRET2(xs, xe, xm, "add", x, y);
 182}
 183