arch/mips/math-emu/dp_div.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 #include "ieee754dp.h"
  28
  29 ieee754dp ieee754dp_div(ieee754dp x, ieee754dp y)
  30 {
  31         COMPXDP;
  32         COMPYDP;
  33
  34         EXPLODEXDP;
  35         EXPLODEYDP;
  36
  37         CLEARCX;
  38
  39         FLUSHXDP;
  40         FLUSHYDP;
  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 ieee754dp_nanxcpt(ieee754dp_indef(), "div", 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
  74         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
  75                 SETCX(IEEE754_INVALID_OPERATION);
  76                 return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
  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 ieee754dp_zero(xs ^ ys);
  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 ieee754dp_inf(xs ^ ys);
  87
  88                 /* Zero handling
  89                  */
  90
  91         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  92                 SETCX(IEEE754_INVALID_OPERATION);
  93                 return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
  94
  95         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  96         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  97                 SETCX(IEEE754_ZERO_DIVIDE);
  98                 return ieee754dp_xcpt(ieee754dp_inf(xs ^ ys), "div", x, y);
  99
 100         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 101         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 102                 return ieee754dp_zero(xs == ys ? 0 : 1);
 103
 104         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 105                 DPDNORMX;
 106
 107         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 108                 DPDNORMY;
 109                 break;
 110
 111         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 112                 DPDNORMX;
 113                 break;
 114
 115         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 116                 break;
 117         }
 118         assert(xm & DP_HIDDEN_BIT);
 119         assert(ym & DP_HIDDEN_BIT);
 120
 121         /* provide rounding space */
 122         xm <<= 3;
 123         ym <<= 3;
 124
 125         {
 126                 /* now the dirty work */
 127
 128                 u64 rm = 0;
 129                 int re = xe - ye;
 130                 u64 bm;
 131
 132                 for (bm = DP_MBIT(DP_MBITS + 2); bm; bm >>= 1) {
 133                         if (xm >= ym) {
 134                                 xm -= ym;
 135                                 rm |= bm;
 136                                 if (xm == 0)
 137                                         break;
 138                         }
 139                         xm <<= 1;
 140                 }
 141                 rm <<= 1;
 142                 if (xm)
 143                         rm |= 1;        /* have remainder, set sticky */
 144
 145                 assert(rm);
 146
 147                 /* normalise rm to rounding precision ?
 148                  */
 149                 while ((rm >> (DP_MBITS + 3)) == 0) {
 150                         rm <<= 1;
 151                         re--;
 152                 }
 153
 154                 DPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);
 155         }
 156 }