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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [common/] [s_round.c] - Blame information for rev 207

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1 207 jeremybenn 
/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunPro, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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/*
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FUNCTION
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<<round>>, <<roundf>>--round to integer, to nearest
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INDEX
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        round
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INDEX
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        roundf
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ANSI_SYNOPSIS
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        #include <math.h>
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        double round(double <[x]>);
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        float roundf(float <[x]>);
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DESCRIPTION
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        The <<round>> functions round their argument to the nearest integer
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        value in floating-point format, rounding halfway cases away from zero,
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        regardless of the current rounding direction.  (While the "inexact"
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        floating-point exception behavior is unspecified by the C standard, the
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        <<round>> functions are written so that "inexact" is not raised if the
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        result does not equal the argument, which behavior is as recommended by
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        IEEE 754 for its related functions.)
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RETURNS
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<[x]> rounded to an integral value.
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PORTABILITY
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ANSI C, POSIX
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SEEALSO
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<<nearbyint>>, <<rint>>
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*/
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#include "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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        double round(double x)
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#else
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        double round(x)
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        double x;
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#endif
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{
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  /* Most significant word, least significant word. */
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  __int32_t msw, exponent_less_1023;
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  __uint32_t lsw;
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  EXTRACT_WORDS(msw, lsw, x);
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  /* Extract exponent field. */
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  exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023;
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  if (exponent_less_1023 < 20)
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    {
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      if (exponent_less_1023 < 0)
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        {
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          msw &= 0x80000000;
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          if (exponent_less_1023 == -1)
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            /* Result is +1.0 or -1.0. */
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            msw |= (1023 << 20);
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          lsw = 0;
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        }
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      else
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        {
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          __uint32_t exponent_mask = 0x000fffff >> exponent_less_1023;
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          if ((msw & exponent_mask) == 0 && lsw == 0)
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            /* x in an integral value. */
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            return x;
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          msw += 0x00080000 >> exponent_less_1023;
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          msw &= ~exponent_mask;
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          lsw = 0;
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        }
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    }
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  else if (exponent_less_1023 > 51)
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    {
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      if (exponent_less_1023 == 1024)
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        /* x is NaN or infinite. */
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        return x + x;
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      else
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        return x;
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    }
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  else
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    {
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      __uint32_t exponent_mask = 0xffffffff >> (exponent_less_1023 - 20);
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      __uint32_t tmp;
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      if ((lsw & exponent_mask) == 0)
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        /* x is an integral value. */
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        return x;
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      tmp = lsw + (1 << (51 - exponent_less_1023));
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      if (tmp < lsw)
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        msw += 1;
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      lsw = tmp;
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      lsw &= ~exponent_mask;
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    }
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  INSERT_WORDS(x, msw, lsw);
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  return x;
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}
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#endif /* _DOUBLE_IS_32BITS */

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