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  *  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
  24 union 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_SNAN, IEEE754_CLASS_QNAN):
  41         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  42         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  43         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  44         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  45         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  46         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  47         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  48         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  49         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  50         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  51                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  52                 return ieee754dp_nanxcpt(ieee754dp_indef());
  53
  54         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  55         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  56         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  57         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  58                 return y;
  59
  60         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  61         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  62         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  63         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  64         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  65                 return x;
  66
  67
  68         /*
  69          * Infinity handling
  70          */
  71         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  72                 if (xs == ys)
  73                         return x;
  74                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  75                 return ieee754dp_indef();
  76
  77         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  78         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  79         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  80                 return y;
  81
  82         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  83         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  84         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  85                 return x;
  86
  87         /*
  88          * Zero handling
  89          */
  90         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  91                 if (xs == ys)
  92                         return x;
  93                 else
  94                         return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
  95
  96         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  97         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  98                 return x;
  99
 100         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 101         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 102                 return y;
 103
 104         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 105                 DPDNORMX;
 106
 107                 /* FALL THROUGH */
 108
 109         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 110                 DPDNORMY;
 111                 break;
 112
 113         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 114                 DPDNORMX;
 115                 break;
 116
 117         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 118                 break;
 119         }
 120         assert(xm & DP_HIDDEN_BIT);
 121         assert(ym & DP_HIDDEN_BIT);
 122
 123         /*
 124          * Provide guard,round and stick bit space.
 125          */
 126         xm <<= 3;
 127         ym <<= 3;
 128
 129         if (xe > ye) {
 130                 /*
 131                  * Have to shift y fraction right to align.
 132                  */
 133                 s = xe - ye;
 134                 ym = XDPSRS(ym, s);
 135                 ye += s;
 136         } else if (ye > xe) {
 137                 /*
 138                  * Have to shift x fraction right to align.
 139                  */
 140                 s = ye - xe;
 141                 xm = XDPSRS(xm, s);
 142                 xe += s;
 143         }
 144         assert(xe == ye);
 145         assert(xe <= DP_EMAX);
 146
 147         if (xs == ys) {
 148                 /*
 149                  * Generate 28 bit result of adding two 27 bit numbers
 150                  * leaving result in xm, xs and 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 == FPU_CSR_RD);
 172
 173                 /*
 174                  * Normalize to rounding precision.
 175                  */
 176                 while ((xm >> (DP_FBITS + 3)) == 0) {
 177                         xm <<= 1;
 178                         xe--;
 179                 }
 180         }
 181
 182         return ieee754dp_format(xs, xe, xm);
 183 }