Logo Search packages:      
Sourcecode: linux version File versions  Download package

sp_mul.c

/* IEEE754 floating point arithmetic
 * single precision
 */
/*
 * MIPS floating point support
 * Copyright (C) 1994-2000 Algorithmics Ltd.
 * http://www.algor.co.uk
 *
 * ########################################################################
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * ########################################################################
 */


#include "ieee754sp.h"

ieee754sp ieee754sp_mul(ieee754sp x, ieee754sp y)
{
      COMPXSP;
      COMPYSP;

      EXPLODEXSP;
      EXPLODEYSP;

      CLEARCX;

      FLUSHXSP;
      FLUSHYSP;

      switch (CLPAIR(xc, yc)) {
      case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
      case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
      case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
      case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
      case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
      case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
      case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
            SETCX(IEEE754_INVALID_OPERATION);
            return ieee754sp_nanxcpt(ieee754sp_indef(), "mul", x, y);

      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
            return y;

      case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
      case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
      case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
      case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
      case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
            return x;


            /* Infinity handling */

      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
            SETCX(IEEE754_INVALID_OPERATION);
            return ieee754sp_xcpt(ieee754sp_indef(), "mul", x, y);

      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
            return ieee754sp_inf(xs ^ ys);

      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
            return ieee754sp_zero(xs ^ ys);


      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
            SPDNORMX;

      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
            SPDNORMY;
            break;

      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
            SPDNORMX;
            break;

      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
            break;
      }
      /* rm = xm * ym, re = xe+ye basicly */
      assert(xm & SP_HIDDEN_BIT);
      assert(ym & SP_HIDDEN_BIT);

      {
            int re = xe + ye;
            int rs = xs ^ ys;
            unsigned rm;

            /* shunt to top of word */
            xm <<= 32 - (SP_MBITS + 1);
            ym <<= 32 - (SP_MBITS + 1);

            /* multiply 32bits xm,ym to give high 32bits rm with stickness
             */
            {
                  unsigned short lxm = xm & 0xffff;
                  unsigned short hxm = xm >> 16;
                  unsigned short lym = ym & 0xffff;
                  unsigned short hym = ym >> 16;
                  unsigned lrm;
                  unsigned hrm;

                  lrm = lxm * lym;  /* 16 * 16 => 32 */
                  hrm = hxm * hym;  /* 16 * 16 => 32 */

                  {
                        unsigned t = lxm * hym; /* 16 * 16 => 32 */
                        {
                              unsigned at = lrm + (t << 16);
                              hrm += at < lrm;
                              lrm = at;
                        }
                        hrm = hrm + (t >> 16);
                  }

                  {
                        unsigned t = hxm * lym; /* 16 * 16 => 32 */
                        {
                              unsigned at = lrm + (t << 16);
                              hrm += at < lrm;
                              lrm = at;
                        }
                        hrm = hrm + (t >> 16);
                  }
                  rm = hrm | (lrm != 0);
            }

            /*
             * sticky shift down to normal rounding precision
             */
            if ((int) rm < 0) {
                  rm = (rm >> (32 - (SP_MBITS + 1 + 3))) |
                      ((rm << (SP_MBITS + 1 + 3)) != 0);
                  re++;
            } else {
                  rm = (rm >> (32 - (SP_MBITS + 1 + 3 + 1))) |
                      ((rm << (SP_MBITS + 1 + 3 + 1)) != 0);
            }
            assert(rm & (SP_HIDDEN_BIT << 3));

            SPNORMRET2(rs, re, rm, "mul", x, y);
      }
}

Generated by  Doxygen 1.6.0   Back to index