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dp_mul.c

/* IEEE754 floating point arithmetic
 * double precision: common utilities
 */
/*
 * 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 "ieee754dp.h"

ieee754dp ieee754dp_mul(ieee754dp x, ieee754dp y)
{
      COMPXDP;
      COMPYDP;

      EXPLODEXDP;
      EXPLODEYDP;

      CLEARCX;

      FLUSHXDP;
      FLUSHYDP;

      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 ieee754dp_nanxcpt(ieee754dp_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 ieee754dp_xcpt(ieee754dp_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 ieee754dp_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 ieee754dp_zero(xs ^ ys);


      case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
            DPDNORMX;

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

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

      case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
            break;
      }
      /* rm = xm * ym, re = xe+ye basicly */
      assert(xm & DP_HIDDEN_BIT);
      assert(ym & DP_HIDDEN_BIT);
      {
            int re = xe + ye;
            int rs = xs ^ ys;
            u64 rm;

            /* shunt to top of word */
            xm <<= 64 - (DP_MBITS + 1);
            ym <<= 64 - (DP_MBITS + 1);

            /* multiply 32bits xm,ym to give high 32bits rm with stickness
             */

            /* 32 * 32 => 64 */
#define DPXMULT(x, y)   ((u64)(x) * (u64)y)

            {
                  unsigned lxm = xm;
                  unsigned hxm = xm >> 32;
                  unsigned lym = ym;
                  unsigned hym = ym >> 32;
                  u64 lrm;
                  u64 hrm;

                  lrm = DPXMULT(lxm, lym);
                  hrm = DPXMULT(hxm, hym);

                  {
                        u64 t = DPXMULT(lxm, hym);
                        {
                              u64 at =
                                  lrm + (t << 32);
                              hrm += at < lrm;
                              lrm = at;
                        }
                        hrm = hrm + (t >> 32);
                  }

                  {
                        u64 t = DPXMULT(hxm, lym);
                        {
                              u64 at =
                                  lrm + (t << 32);
                              hrm += at < lrm;
                              lrm = at;
                        }
                        hrm = hrm + (t >> 32);
                  }
                  rm = hrm | (lrm != 0);
            }

            /*
             * sticky shift down to normal rounding precision
             */
            if ((s64) rm < 0) {
                  rm =
                      (rm >> (64 - (DP_MBITS + 1 + 3))) |
                      ((rm << (DP_MBITS + 1 + 3)) != 0);
                  re++;
            } else {
                  rm =
                      (rm >> (64 - (DP_MBITS + 1 + 3 + 1))) |
                      ((rm << (DP_MBITS + 1 + 3 + 1)) != 0);
            }
            assert(rm & (DP_HIDDEN_BIT << 3));
            DPNORMRET2(rs, re, rm, "mul", x, y);
      }
}

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