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dp_tlong.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"

s64 ieee754dp_tlong(ieee754dp x)
{
      COMPXDP;

      CLEARCX;

      EXPLODEXDP;
      FLUSHXDP;

      switch (xc) {
      case IEEE754_CLASS_SNAN:
      case IEEE754_CLASS_QNAN:
      case IEEE754_CLASS_INF:
            SETCX(IEEE754_INVALID_OPERATION);
            return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x);
      case IEEE754_CLASS_ZERO:
            return 0;
      case IEEE754_CLASS_DNORM:
      case IEEE754_CLASS_NORM:
            break;
      }
      if (xe >= 63) {
            /* look for valid corner case */
            if (xe == 63 && xs && xm == DP_HIDDEN_BIT)
                  return -0x8000000000000000LL;
            /* Set invalid. We will only use overflow for floating
               point overflow */
            SETCX(IEEE754_INVALID_OPERATION);
            return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x);
      }
      /* oh gawd */
      if (xe > DP_MBITS) {
            xm <<= xe - DP_MBITS;
      } else if (xe < DP_MBITS) {
            u64 residue;
            int round;
            int sticky;
            int odd;

            if (xe < -1) {
                  residue = xm;
                  round = 0;
                  sticky = residue != 0;
                  xm = 0;
            }
            else {
                  /* Shifting a u64 64 times does not work,
                  * so we do it in two steps. Be aware that xe
                  * may be -1 */
                  residue = xm << (xe + 1);
                  residue <<= 63 - DP_MBITS;
                  round = (residue >> 63) != 0;
                  sticky = (residue << 1) != 0;
                  xm >>= DP_MBITS - xe;
            }
            odd = (xm & 0x1) != 0x0;
            switch (ieee754_csr.rm) {
            case IEEE754_RN:
                  if (round && (sticky || odd))
                        xm++;
                  break;
            case IEEE754_RZ:
                  break;
            case IEEE754_RU:  /* toward +Infinity */
                  if ((round || sticky) && !xs)
                        xm++;
                  break;
            case IEEE754_RD:  /* toward -Infinity */
                  if ((round || sticky) && xs)
                        xm++;
                  break;
            }
            if ((xm >> 63) != 0) {
                  /* This can happen after rounding */
                  SETCX(IEEE754_INVALID_OPERATION);
                  return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x);
            }
            if (round || sticky)
                  SETCX(IEEE754_INEXACT);
      }
      if (xs)
            return -xm;
      else
            return xm;
}


u64 ieee754dp_tulong(ieee754dp x)
{
      ieee754dp hb = ieee754dp_1e63();

      /* what if x < 0 ?? */
      if (ieee754dp_lt(x, hb))
            return (u64) ieee754dp_tlong(x);

      return (u64) ieee754dp_tlong(ieee754dp_sub(x, hb)) |
          (1ULL << 63);
}

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