git.oblomov.eu Git - linux-2.6/blob - 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  * 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 "ieee754dp.h"
  29
  30 ieee754dp ieee754dp_div(ieee754dp x, ieee754dp y)
  31 {
  32         COMPXDP;
  33         COMPYDP;
  34
  35         EXPLODEXDP;
  36         EXPLODEYDP;
  37
  38         CLEARCX;
  39
  40         FLUSHXDP;
  41         FLUSHYDP;
  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 ieee754dp_nanxcpt(ieee754dp_indef(), "div", 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                 SETCX(IEEE754_INVALID_OPERATION);
  77                 return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
  78
  79         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
  80         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
  81         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
  82                 return ieee754dp_zero(xs ^ ys);
  83
  84         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
  85         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
  86         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
  87                 return ieee754dp_inf(xs ^ ys);
  88
  89                 /* Zero handling
  90                  */
  91
  92         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
  93                 SETCX(IEEE754_INVALID_OPERATION);
  94                 return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
  95
  96         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
  97         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
  98                 SETCX(IEEE754_ZERO_DIVIDE);
  99                 return ieee754dp_xcpt(ieee754dp_inf(xs ^ ys), "div", x, y);
 100
 101         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 102         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 103                 return ieee754dp_zero(xs == ys ? 0 : 1);
 104
 105         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 106                 DPDNORMX;
 107
 108         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 109                 DPDNORMY;
 110                 break;
 111
 112         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
 113                 DPDNORMX;
 114                 break;
 115
 116         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
 117                 break;
 118         }
 119         assert(xm & DP_HIDDEN_BIT);
 120         assert(ym & DP_HIDDEN_BIT);
 121
 122         /* provide rounding space */
 123         xm <<= 3;
 124         ym <<= 3;
 125
 126         {
 127                 /* now the dirty work */
 128
 129                 u64 rm = 0;
 130                 int re = xe - ye;
 131                 u64 bm;
 132
 133                 for (bm = DP_MBIT(DP_MBITS + 2); bm; bm >>= 1) {
 134                         if (xm >= ym) {
 135                                 xm -= ym;
 136                                 rm |= bm;
 137                                 if (xm == 0)
 138                                         break;
 139                         }
 140                         xm <<= 1;
 141                 }
 142                 rm <<= 1;
 143                 if (xm)
 144                         rm |= 1;        /* have remainder, set sticky */
 145
 146                 assert(rm);
 147
 148                 /* normalise rm to rounding precision ?
 149                  */
 150                 while ((rm >> (DP_MBITS + 3)) == 0) {
 151                         rm <<= 1;
 152                         re--;
 153                 }
 154
 155                 DPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);
 156         }
 157 }