sysdeps/ieee754/ldbl-128/s_rintl.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  * rintl(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 rintl(x).
  28  */
  29
  30 #include "math.h"
  31 #include "math_private.h"
  32
  33 #ifdef __STDC__
  34 static const long double
  35 #else
  36 static long double
  37 #endif
  38 TWO112[2]={
  39   5.19229685853482762853049632922009600E+33L, /* 0x406F000000000000, 0 */
  40  -5.19229685853482762853049632922009600E+33L  /* 0xC06F000000000000, 0 */
  41 };
  42
  43 #ifdef __STDC__
  44         long double __rintl(long double x)
  45 #else
  46         long double __rintl(x)
  47         long double x;
  48 #endif
  49 {
  50         int64_t i0,j0,sx;
  51         u_int64_t i,i1;
  52         long double w,t;
  53         GET_LDOUBLE_WORDS64(i0,i1,x);
  54         sx = (((u_int64_t)i0)>>63);
  55         j0 = ((i0>>48)&0x7fff)-0x3fff;
  56         if(j0<48) {
  57             if(j0<0) {
  58                 if(((i0&0x7fffffffffffffffLL)|i1)==0) return x;
  59                 i1 |= (i0&0x0000ffffffffffffLL);
  60                 i0 &= 0xffffe00000000000ULL;
  61                 i0 |= ((i1|-i1)>>16)&0x0000800000000000LL;
  62                 SET_LDOUBLE_MSW64(x,i0);
  63                 w = TWO112[sx]+x;
  64                 t = w-TWO112[sx];
  65                 GET_LDOUBLE_MSW64(i0,t);
  66                 SET_LDOUBLE_MSW64(t,(i0&0x7fffffffffffffffLL)|(sx<<63));
  67                 return t;
  68             } else {
  69                 i = (0x0000ffffffffffffLL)>>j0;
  70                 if(((i0&i)|i1)==0) return x; /* x is integral */
  71                 i>>=1;
  72                 if(((i0&i)|i1)!=0) {
  73                     if(j0==47) i1 = 0x4000000000000000ULL; else
  74                     i0 = (i0&(~i))|((0x0000200000000000LL)>>j0);
  75                 }
  76             }
  77         } else if (j0>111) {
  78             if(j0==0x4000) return x+x;  /* inf or NaN */
  79             else return x;              /* x is integral */
  80         } else {
  81             i = -1ULL>>(j0-48);
  82             if((i1&i)==0) return x;     /* x is integral */
  83             i>>=1;
  84             if((i1&i)!=0) i1 = (i1&(~i))|((0x4000000000000000LL)>>(j0-48));
  85         }
  86         SET_LDOUBLE_WORDS64(x,i0,i1);
  87         w = TWO112[sx]+x;
  88         return w-TWO112[sx];
  89 }
  90 weak_alias (__rintl, rintl)