git.oblomov.eu Git - linux-2.6/blob - arch/mips/math-emu/dp_add.c

   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
  29 #include "ieee754dp.h"
  30
  31 ieee754dp ieee754dp_add(ieee754dp x, ieee754dp y)
  32 {
  33         COMPXDP;
  34         COMPYDP;
  35
  36         EXPLODEXDP;
  37         EXPLODEYDP;
  38
  39         CLEARCX;
  40
  41         FLUSHXDP;
  42         FLUSHYDP;
  43
  44         switch (CLPAIR(xc, yc)) {
  45         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  46         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  47         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  48         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  49         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  50         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  51         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  52         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  53         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  54         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  55         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  56                 SETCX(IEEE754_INVALID_OPERATION);
  57                 return ieee754dp_nanxcpt(ieee754dp_indef(), "add", x, y);
  58
  59         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  60         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  61         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  62         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  63                 return y;
  64
  65         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  66         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  67         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  68         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  69         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  70                 return x;
  71
  72
  73                 /* Infinity handling
  74                  */
  75
  76         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  77                 if (xs == ys)
  78                         return x;
  79                 SETCX(IEEE754_INVALID_OPERATION);
  80                 return ieee754dp_xcpt(ieee754dp_indef(), "add", x, y);
  81
  82         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  83         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  84         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  85                 return y;
  86
  87         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  88         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  89         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  90                 return x;
  91
  92                 /* Zero handling
  93                  */
  94
  95         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  96                 if (xs == ys)
  97                         return x;
  98                 else
  99                         return ieee754dp_zero(ieee754_csr.rm ==
 100                                               IEEE754_RD);
 101
 102         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
 103         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
 104                 return x;
 105
 106         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 107         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 108                 return y;
 109
 110         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 111                 DPDNORMX;
 112
 113                 /* FALL THROUGH */
 114
 115         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 116                 DPDNORMY;
 117                 break;
 118
 119         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 120                 DPDNORMX;
 121                 break;
 122
 123         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 124                 break;
 125         }
 126         assert(xm & DP_HIDDEN_BIT);
 127         assert(ym & DP_HIDDEN_BIT);
 128
 129         /* provide guard,round and stick bit space */
 130         xm <<= 3;
 131         ym <<= 3;
 132
 133         if (xe > ye) {
 134                 /* have to shift y fraction right to align
 135                  */
 136                 int s = xe - ye;
 137                 ym = XDPSRS(ym, s);
 138                 ye += s;
 139         } else if (ye > xe) {
 140                 /* have to shift x fraction right to align
 141                  */
 142                 int s = ye - xe;
 143                 xm = XDPSRS(xm, s);
 144                 xe += s;
 145         }
 146         assert(xe == ye);
 147         assert(xe <= DP_EMAX);
 148
 149         if (xs == ys) {
 150                 /* generate 28 bit result of adding two 27 bit numbers
 151                  * leaving result in xm,xs,xe
 152                  */
 153                 xm = xm + ym;
 154                 xe = xe;
 155                 xs = xs;
 156
 157                 if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */
 158                         xm = XDPSRS1(xm);
 159                         xe++;
 160                 }
 161         } else {
 162                 if (xm >= ym) {
 163                         xm = xm - ym;
 164                         xe = xe;
 165                         xs = xs;
 166                 } else {
 167                         xm = ym - xm;
 168                         xe = xe;
 169                         xs = ys;
 170                 }
 171                 if (xm == 0)
 172                         return ieee754dp_zero(ieee754_csr.rm ==
 173                                               IEEE754_RD);
 174
 175                 /* normalize to rounding precision */
 176                 while ((xm >> (DP_MBITS + 3)) == 0) {
 177                         xm <<= 1;
 178                         xe--;
 179                 }
 180
 181         }
 182         DPNORMRET2(xs, xe, xm, "add", x, y);
 183 }