arch/mips/math-emu/sp_add.c

   1 /* IEEE754 floating point arithmetic
   2  * single precision
   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 "ieee754sp.h"
  23
  24 union ieee754sp ieee754sp_add(union ieee754sp x, union ieee754sp y)
  25 {
  26         int s;
  27
  28         COMPXSP;
  29         COMPYSP;
  30
  31         EXPLODEXSP;
  32         EXPLODEYSP;
  33
  34         ieee754_clearcx();
  35
  36         FLUSHXSP;
  37         FLUSHYSP;
  38
  39         switch (CLPAIR(xc, yc)) {
  40         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  41         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  42         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  43         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  44         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  45                 return ieee754sp_nanxcpt(y);
  46
  47         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  48         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  49         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  50         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  51         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  52         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  53                 return ieee754sp_nanxcpt(x);
  54
  55         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  56         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  57         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  58         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  59                 return y;
  60
  61         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  62         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  63         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  64         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  65         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  66                 return x;
  67
  68
  69         /*
  70          * Infinity handling
  71          */
  72         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  73                 if (xs == ys)
  74                         return x;
  75                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  76                 return ieee754sp_indef();
  77
  78         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  79         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  80         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  81                 return y;
  82
  83         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  84         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  85         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  86                 return x;
  87
  88         /*
  89          * Zero handling
  90          */
  91         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  92                 if (xs == ys)
  93                         return x;
  94                 else
  95                         return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
  96
  97         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  98         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  99                 return x;
 100
 101         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 102         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 103                 return y;
 104
 105         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 106                 SPDNORMX;
 107                 /* fall through */
 108
 109         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 110                 SPDNORMY;
 111                 break;
 112
 113         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 114                 SPDNORMX;
 115                 break;
 116
 117         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 118                 break;
 119         }
 120         assert(xm & SP_HIDDEN_BIT);
 121         assert(ym & SP_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 = XSPSRS(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 = XSPSRS(xm, s);
 142                 xe += s;
 143         }
 144         assert(xe == ye);
 145         assert(xe <= SP_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
 154                 if (xm >> (SP_FBITS + 1 + 3)) { /* carry out */
 155                         SPXSRSX1();
 156                 }
 157         } else {
 158                 if (xm >= ym) {
 159                         xm = xm - ym;
 160                 } else {
 161                         xm = ym - xm;
 162                         xs = ys;
 163                 }
 164                 if (xm == 0)
 165                         return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
 166
 167                 /*
 168                  * Normalize in extended single precision
 169                  */
 170                 while ((xm >> (SP_FBITS + 3)) == 0) {
 171                         xm <<= 1;
 172                         xe--;
 173                 }
 174         }
 175
 176         return ieee754sp_format(xs, xe, xm);
 177 }