Subversion Repositories openrisc_2011-10-31

/*

 * ====================================================

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunPro, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice

 * is preserved.

 * ====================================================

 */

#include "fdlibm.h"

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

        double trunc(double x)

#else

        double trunc(x)

        double x;

#endif

{

  int signbit;

  /* Most significant word, least significant word. */

  int msw;

  unsigned int lsw;

  int exponent_less_1023;

  EXTRACT_WORDS(msw, lsw, x);

  /* Extract sign bit. */

  signbit = msw & 0x80000000;

  /* Extract exponent field. */

  exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023;

  if (exponent_less_1023 < 20)

    {

      /* All significant digits are in msw. */

      if (exponent_less_1023 < 0)

        {

          /* -1 < x < 1, so result is +0 or -0. */

          INSERT_WORDS(x, signbit, 0);

        }

      else

        {

          /* All relevant fraction bits are in msw, so lsw of the result is 0. */

          INSERT_WORDS(x, signbit | (msw & ~(0x000fffff >> exponent_less_1023)), 0);

        }

    }

  else if (exponent_less_1023 > 51)

    {

      if (exponent_less_1023 == 1024)

        {

          /* x is infinite, or not a number, so trigger an exception. */

          return x + x;

        }

      /* All bits in the fraction fields of the msw and lsw are needed in the result. */

    }

  else

    {

      /* All fraction bits in msw are relevant.  Truncate irrelevant

         bits from lsw. */

      INSERT_WORDS(x, msw, lsw & ~(0xffffffffu >> (exponent_less_1023 - 20)));

    }

  return x;

}

#endif /* _DOUBLE_IS_32BITS */