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  *
   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
  30 union ieee754dp ieee754dp_add(union ieee754dp x, union ieee754dp y)
  31 {
  32         COMPXDP;
  33         COMPYDP;
  34
  35         EXPLODEXDP;
  36         EXPLODEYDP;
  37
  38         ieee754_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                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  56                 return ieee754dp_nanxcpt(ieee754dp_indef());
  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                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  79                 return ieee754dp_indef();
  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_FBITS + 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_FBITS + 3)) == 0) {
 176                         xm <<= 1;
 177                         xe--;
 178                 }
 179
 180         }
 181
 182         return ieee754dp_format(xs, xe, xm);
 183 }