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sp_div.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_div(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(), "div", 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_INF):
            SETCX(IEEE754_INVALID_OPERATION);
            return ieee754sp_xcpt(ieee754sp_indef(), "div", x, y);

      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
            return ieee754sp_zero(xs ^ ys);

      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
      case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
            return ieee754sp_inf(xs ^ ys);

            /* Zero handling
             */

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

      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
            SETCX(IEEE754_ZERO_DIVIDE);
            return ieee754sp_xcpt(ieee754sp_inf(xs ^ ys), "div", x, y);

      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
      case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
            return ieee754sp_zero(xs == ys ? 0 : 1);

      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;
      }
      assert(xm & SP_HIDDEN_BIT);
      assert(ym & SP_HIDDEN_BIT);

      /* provide rounding space */
      xm <<= 3;
      ym <<= 3;

      {
            /* now the dirty work */

            unsigned rm = 0;
            int re = xe - ye;
            unsigned bm;

            for (bm = SP_MBIT(SP_MBITS + 2); bm; bm >>= 1) {
                  if (xm >= ym) {
                        xm -= ym;
                        rm |= bm;
                        if (xm == 0)
                              break;
                  }
                  xm <<= 1;
            }
            rm <<= 1;
            if (xm)
                  rm |= 1;    /* have remainder, set sticky */

            assert(rm);

            /* normalise rm to rounding precision ?
             */
            while ((rm >> (SP_MBITS + 3)) == 0) {
                  rm <<= 1;
                  re--;
            }

            SPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);
      }
}

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