1  /*
       2   * ====================================================
       3   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       4   *
       5   * Developed at SunPro, a Sun Microsystems, Inc. business.
       6   * Permission to use, copy, modify, and distribute this
       7   * software is freely granted, provided that this notice
       8   * is preserved.
       9   * ====================================================
      10   */
      11  
      12  /*
      13   * rint(x)
      14   * Return x rounded to integral value according to the prevailing
      15   * rounding mode.
      16   * Method:
      17   *	Using floating addition.
      18   * Exception:
      19   *	Inexact flag raised if x not equal to rint(x).
      20   */
      21  
      22  #define NO_MATH_REDIRECT
      23  #include <math.h>
      24  #include <math_private.h>
      25  #include <libm-alias-double.h>
      26  #include <math-use-builtins.h>
      27  
      28  double
      29  __rint (double x)
      30  {
      31  #if USE_RINT_BUILTIN
      32    return __builtin_rint (x);
      33  #else
      34    /* Use generic implementation.  */
      35    static const double
      36      TWO52[2] = {
      37  		4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
      38  		-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
      39    };
      40    int64_t i0, sx;
      41    int32_t j0;
      42    EXTRACT_WORDS64 (i0, x);
      43    sx = (i0 >> 63) & 1;
      44    j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
      45    if (j0 < 52)
      46      {
      47        if (j0 < 0)
      48  	{
      49  	  double w = TWO52[sx] + x;
      50  	  double t =  w - TWO52[sx];
      51  	  EXTRACT_WORDS64 (i0, t);
      52  	  INSERT_WORDS64 (t, (i0 & UINT64_C (0x7fffffffffffffff))
      53  			  | (sx << 63));
      54  	  return t;
      55  	}
      56      }
      57    else
      58      {
      59        if (j0 == 0x400)
      60  	return x + x;			/* inf or NaN  */
      61        else
      62  	return x;			/* x is integral  */
      63      }
      64    double w = TWO52[sx] + x;
      65    return w - TWO52[sx];
      66  #endif /* ! USE_RINT_BUILTIN  */
      67  }
      68  #ifndef __rint
      69  libm_alias_double (__rint, rint)
      70  #endif