git.oblomov.eu Git - linux-2.6/blob - 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  * 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
  30 ieee754sp 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 }