libquadmath/math/rintq.c

   1 /* s_rintl.c -- long double 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 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: $";
  18 #endif
  19
  20 /*
  21  * rintq(x)
  22  * Return x rounded to integral value according to the prevailing
  23  * rounding mode.
  24  * Method:
  25  *      Using floating addition.
  26  * Exception:
  27  *      Inexact flag raised if x not equal to rintq(x).
  28  */
  29
  30 #define NO_MATH_REDIRECT
  31
  32 #include "quadmath-imp.h"
  33
  34 static const __float128
  35 TWO112[2]={
  36   5.19229685853482762853049632922009600E+33L, /* 0x406F000000000000, 0 */
  37  -5.19229685853482762853049632922009600E+33L  /* 0xC06F000000000000, 0 */
  38 };
  39
  40 __float128 rintq(__float128 x)
  41 {
  42         int64_t i0,j0,sx;
  43         uint64_t i1 __attribute__ ((unused));
  44         __float128 w,t;
  45         GET_FLT128_WORDS64(i0,i1,x);
  46         sx = (((uint64_t)i0)>>63);
  47         j0 = ((i0>>48)&0x7fff)-0x3fff;
  48         if(j0<112) {
  49             if(j0<0) {
  50                 w = TWO112[sx]+x;
  51                 t = w-TWO112[sx];
  52                 GET_FLT128_MSW64(i0,t);
  53                 SET_FLT128_MSW64(t,(i0&0x7fffffffffffffffLL)|(sx<<63));
  54                 return t;
  55             }
  56         } else {
  57             if(j0==0x4000) return x+x;  /* inf or NaN */
  58             else return x;              /* x is integral */
  59         }
  60         w = TWO112[sx]+x;
  61         return w-TWO112[sx];
  62 }