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 * 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/* modf function is always exact for a finite number
  31*/
  32ieee754dp ieee754dp_modf(ieee754dp x, ieee754dp * ip)
  33{
  34        COMPXDP;
  35
  36        CLEARCX;
  37
  38        EXPLODEXDP;
  39
  40        switch (xc) {
  41        case IEEE754_CLASS_SNAN:
  42        case IEEE754_CLASS_QNAN:
  43        case IEEE754_CLASS_INF:
  44        case IEEE754_CLASS_ZERO:
  45                *ip = x;
  46                return x;
  47        case IEEE754_CLASS_DNORM:
  48                /* far to small */
  49                *ip = ieee754dp_zero(xs);
  50                return x;
  51        case IEEE754_CLASS_NORM:
  52                break;
  53        }
  54        if (xe < 0) {
  55                *ip = ieee754dp_zero(xs);
  56                return x;
  57        }
  58        if (xe >= DP_MBITS) {
  59                *ip = x;
  60                return ieee754dp_zero(xs);
  61        }
  62        /* generate ipart mantissa by clearing bottom bits
  63         */
  64        *ip = builddp(xs, xe + DP_EBIAS,
  65                      ((xm >> (DP_MBITS - xe)) << (DP_MBITS - xe)) &
  66                      ~DP_HIDDEN_BIT);
  67
  68        /* generate fpart mantissa by clearing top bits
  69         * and normalizing (must be able to normalize)
  70         */
  71        xm = (xm << (64 - (DP_MBITS - xe))) >> (64 - (DP_MBITS - xe));
  72        if (xm == 0)
  73                return ieee754dp_zero(xs);
  74
  75        while ((xm >> DP_MBITS) == 0) {
  76                xm <<= 1;
  77                xe--;
  78        }
  79        return builddp(xs, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
  80}
  81