sysdeps/ieee754/dbl-64/wordsize-64/s_rint.c

   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 #include <math.h>
  23 #include <math_private.h>
  24
  25 static const double
  26 TWO52[2]={
  27   4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  28  -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  29 };
  30
  31 double
  32 __rint(double x)
  33 {
  34         int64_t i0,sx;
  35         int32_t j0;
  36         EXTRACT_WORDS64(i0,x);
  37         sx = (i0>>63)&1;
  38         j0 = ((i0>>52)&0x7ff)-0x3ff;
  39         if(j0<52) {
  40             if(j0<0) {
  41                 double w = TWO52[sx]+x;
  42                 double t =  w-TWO52[sx];
  43                 EXTRACT_WORDS64(i0,t);
  44                 INSERT_WORDS64(t,(i0&UINT64_C(0x7fffffffffffffff))|(sx<<63));
  45                 return t;
  46             }
  47         } else {
  48             if(j0==0x400) return x+x;   /* inf or NaN */
  49             else return x;              /* x is integral */
  50         }
  51         double w = TWO52[sx]+x;
  52         return w-TWO52[sx];
  53 }
  54 #ifndef __rint
  55 weak_alias (__rint, rint)
  56 # ifdef NO_LONG_DOUBLE
  57 strong_alias (__rint, __rintl)
  58 weak_alias (__rint, rintl)
  59 # endif
  60 #endif