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 * 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 "ieee754sp.h"
  29
  30ieee754sp ieee754sp_add(ieee754sp x, ieee754sp y)
  31{
  32        COMPXSP;
  33        COMPYSP;
  34
  35        EXPLODEXSP;
  36        EXPLODEYSP;
  37
  38        CLEARCX;
  39
  40        FLUSHXSP;
  41        FLUSHYSP;
  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 ieee754sp_nanxcpt(ieee754sp_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 ieee754sp_xcpt(ieee754sp_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 ieee754sp_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                SPDNORMX;
 111
 112        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 113                SPDNORMY;
 114                break;
 115
 116        case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 117                SPDNORMX;
 118                break;
 119
 120        case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 121                break;
 122        }
 123        assert(xm & SP_HIDDEN_BIT);
 124        assert(ym & SP_HIDDEN_BIT);
 125
 126        /* provide guard,round and stick bit space */
 127        xm <<= 3;
 128        ym <<= 3;
 129
 130        if (xe > ye) {
 131                /* have to shift y fraction right to align
 132                 */
 133                int s = xe - ye;
 134                SPXSRSYn(s);
 135        } else if (ye > xe) {
 136                /* have to shift x fraction right to align
 137                 */
 138                int s = ye - xe;
 139                SPXSRSXn(s);
 140        }
 141        assert(xe == ye);
 142        assert(xe <= SP_EMAX);
 143
 144        if (xs == ys) {
 145                /* generate 28 bit result of adding two 27 bit numbers
 146                 * leaving result in xm,xs,xe
 147                 */
 148                xm = xm + ym;
 149                xe = xe;
 150                xs = xs;
 151
 152                if (xm >> (SP_MBITS + 1 + 3)) { /* carry out */
 153                        SPXSRSX1();
 154                }
 155        } else {
 156                if (xm >= ym) {
 157                        xm = xm - ym;
 158                        xe = xe;
 159                        xs = xs;
 160                } else {
 161                        xm = ym - xm;
 162                        xe = xe;
 163                        xs = ys;
 164                }
 165                if (xm == 0)
 166                        return ieee754sp_zero(ieee754_csr.rm ==
 167                                              IEEE754_RD);
 168
 169                /* normalize in extended single precision */
 170                while ((xm >> (SP_MBITS + 3)) == 0) {
 171                        xm <<= 1;
 172                        xe--;
 173                }
 174
 175        }
 176        SPNORMRET2(xs, xe, xm, "add", x, y);
 177}
 178