LXR linux/arch/mips/math-emu/dp

   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/* modf function is always exact for a finite number
  30*/
  31ieee754dp ieee754dp_modf(ieee754dp x, ieee754dp *ip)
  32{
  33        COMPXDP;
  34
  35        CLEARCX;
  36
  37        EXPLODEXDP;
  38
  39        switch (xc) {
  40        case IEEE754_CLASS_SNAN:
  41        case IEEE754_CLASS_QNAN:
  42        case IEEE754_CLASS_INF:
  43        case IEEE754_CLASS_ZERO:
  44                *ip = x;
  45                return x;
  46        case IEEE754_CLASS_DNORM:
  47                /* far to small */
  48                *ip = ieee754dp_zero(xs);
  49                return x;
  50        case IEEE754_CLASS_NORM:
  51                break;
  52        }
  53        if (xe < 0) {
  54                *ip = ieee754dp_zero(xs);
  55                return x;
  56        }
  57        if (xe >= DP_MBITS) {
  58                *ip = x;
  59                return ieee754dp_zero(xs);
  60        }
  61        /* generate ipart mantissa by clearing bottom bits
  62         */
  63        *ip = builddp(xs, xe + DP_EBIAS,
  64                      ((xm >> (DP_MBITS - xe)) << (DP_MBITS - xe)) &
  65                      ~DP_HIDDEN_BIT);
  66
  67        /* generate fpart mantissa by clearing top bits
  68         * and normalizing (must be able to normalize)
  69         */
  70        xm = (xm << (64 - (DP_MBITS - xe))) >> (64 - (DP_MBITS - xe));
  71        if (xm == 0)
  72                return ieee754dp_zero(xs);
  73
  74        while ((xm >> DP_MBITS) == 0) {
  75                xm <<= 1;
  76                xe--;
  77        }
  78        return builddp(xs, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
  79}
  80