arch/mips/math-emu/sp_mul.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  * ########################################################################
   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 #include "ieee754sp.h"
  28
  29 ieee754sp ieee754sp_mul(ieee754sp x, ieee754sp y)
  30 {
  31         COMPXSP;
  32         COMPYSP;
  33
  34         EXPLODEXSP;
  35         EXPLODEYSP;
  36
  37         CLEARCX;
  38
  39         FLUSHXSP;
  40         FLUSHYSP;
  41
  42         switch (CLPAIR(xc, yc)) {
  43         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
  44         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
  45         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
  46         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
  47         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
  48         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
  49         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
  50         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
  51         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
  52         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
  53         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
  54                 SETCX(IEEE754_INVALID_OPERATION);
  55                 return ieee754sp_nanxcpt(ieee754sp_indef(), "mul", x, y);
  56
  57         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
  58         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
  59         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
  60         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
  61                 return y;
  62
  63         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
  64         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
  65         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
  66         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
  67         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
  68                 return x;
  69
  70
  71                 /* Infinity handling */
  72
  73         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  74         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  75                 SETCX(IEEE754_INVALID_OPERATION);
  76                 return ieee754sp_xcpt(ieee754sp_indef(), "mul", x, y);
  77
  78         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  79         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  80         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  81         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  82         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  83                 return ieee754sp_inf(xs ^ ys);
  84
  85         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  86         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
  87         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
  88         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  89         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  90                 return ieee754sp_zero(xs ^ ys);
  91
  92
  93         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
  94                 SPDNORMX;
  95
  96         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
  97                 SPDNORMY;
  98                 break;
  99
 100         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 101                 SPDNORMX;
 102                 break;
 103
 104         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 105                 break;
 106         }
 107         /* rm = xm * ym, re = xe+ye basically */
 108         assert(xm & SP_HIDDEN_BIT);
 109         assert(ym & SP_HIDDEN_BIT);
 110
 111         {
 112                 int re = xe + ye;
 113                 int rs = xs ^ ys;
 114                 unsigned rm;
 115
 116                 /* shunt to top of word */
 117                 xm <<= 32 - (SP_MBITS + 1);
 118                 ym <<= 32 - (SP_MBITS + 1);
 119
 120                 /* multiply 32bits xm,ym to give high 32bits rm with stickness
 121                  */
 122                 {
 123                         unsigned short lxm = xm & 0xffff;
 124                         unsigned short hxm = xm >> 16;
 125                         unsigned short lym = ym & 0xffff;
 126                         unsigned short hym = ym >> 16;
 127                         unsigned lrm;
 128                         unsigned hrm;
 129
 130                         lrm = lxm * lym;        /* 16 * 16 => 32 */
 131                         hrm = hxm * hym;        /* 16 * 16 => 32 */
 132
 133                         {
 134                                 unsigned t = lxm * hym; /* 16 * 16 => 32 */
 135                                 {
 136                                         unsigned at = lrm + (t << 16);
 137                                         hrm += at < lrm;
 138                                         lrm = at;
 139                                 }
 140                                 hrm = hrm + (t >> 16);
 141                         }
 142
 143                         {
 144                                 unsigned t = hxm * lym; /* 16 * 16 => 32 */
 145                                 {
 146                                         unsigned at = lrm + (t << 16);
 147                                         hrm += at < lrm;
 148                                         lrm = at;
 149                                 }
 150                                 hrm = hrm + (t >> 16);
 151                         }
 152                         rm = hrm | (lrm != 0);
 153                 }
 154
 155                 /*
 156                  * sticky shift down to normal rounding precision
 157                  */
 158                 if ((int) rm < 0) {
 159                         rm = (rm >> (32 - (SP_MBITS + 1 + 3))) |
 160                             ((rm << (SP_MBITS + 1 + 3)) != 0);
 161                         re++;
 162                 } else {
 163                         rm = (rm >> (32 - (SP_MBITS + 1 + 3 + 1))) |
 164                             ((rm << (SP_MBITS + 1 + 3 + 1)) != 0);
 165                 }
 166                 assert(rm & (SP_HIDDEN_BIT << 3));
 167
 168                 SPNORMRET2(rs, re, rm, "mul", x, y);
 169         }
 170 }