libquadmath/math/rintq.c

   1 /* rintq.c -- __float128 version of s_rint.c.
   2  * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 /*
  17  * rintq(x)
  18  * Return x rounded to integral value according to the prevailing
  19  * rounding mode.
  20  * Method:
  21  *      Using floating addition.
  22  * Exception:
  23  *      Inexact flag raised if x not equal to rintq(x).
  24  */
  25
  26 #include "quadmath-imp.h"
  27
  28 static const __float128
  29 TWO112[2]={
  30   5.19229685853482762853049632922009600E+33Q, /* 0x406F000000000000, 0 */
  31  -5.19229685853482762853049632922009600E+33Q  /* 0xC06F000000000000, 0 */
  32 };
  33
  34 __float128
  35 rintq (__float128 x)
  36 {
  37         int64_t i0,j0,sx;
  38         uint64_t i1 __attribute__ ((unused));
  39         __float128 w,t;
  40         GET_FLT128_WORDS64(i0,i1,x);
  41         sx = (((uint64_t)i0)>>63);
  42         j0 = ((i0>>48)&0x7fff)-0x3fff;
  43         if(j0<112) {
  44             if(j0<0) {
  45                 w = TWO112[sx]+x;
  46                 t = w-TWO112[sx];
  47                 GET_FLT128_MSW64(i0,t);
  48                 SET_FLT128_MSW64(t,(i0&0x7fffffffffffffffLL)|(sx<<63));
  49                 return t;
  50             }
  51         } else {
  52             if(j0==0x4000) return x+x;  /* inf or NaN */
  53             else return x;              /* x is integral */
  54         }
  55         w = TWO112[sx]+x;
  56         return w-TWO112[sx];
  57 }