1/* @(#)s_rint.c 5.1 93/09/24 */
2/*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13/*
14 * rint(x)
15 * Return x rounded to integral value according to the prevailing
16 * rounding mode.
17 * Method:
18 *	Using floating addition.
19 * Exception:
20 *	Inexact flag raised if x not equal to rint(x).
21 */
22
23#include <float.h>
24#include <math.h>
25
26#include "math_private.h"
27
28static const double
29TWO52[2]={
30  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
31 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
32};
33
34double
35rint(double x)
36{
37	int32_t i0,jj0,sx;
38	u_int32_t i,i1;
39	double t;
40	volatile double w;	/* clip extra precision */
41	EXTRACT_WORDS(i0,i1,x);
42	sx = (i0>>31)&1;
43	jj0 = ((i0>>20)&0x7ff)-0x3ff;
44	if(jj0<20) {
45	    if(jj0<0) {
46		if(((i0&0x7fffffff)|i1)==0) return x;
47		i1 |= (i0&0x0fffff);
48		i0 &= 0xfffe0000;
49		i0 |= ((i1|-i1)>>12)&0x80000;
50		SET_HIGH_WORD(x,i0);
51	        w = TWO52[sx]+x;
52	        t =  w-TWO52[sx];
53		GET_HIGH_WORD(i0,t);
54		SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
55	        return t;
56	    } else {
57		i = (0x000fffff)>>jj0;
58		if(((i0&i)|i1)==0) return x; /* x is integral */
59		i>>=1;
60		if(((i0&i)|i1)!=0) {
61		    if(jj0==19) i1 = 0x40000000; else
62		    i0 = (i0&(~i))|((0x20000)>>jj0);
63		}
64	    }
65	} else if (jj0>51) {
66	    if(jj0==0x400) return x+x;	/* inf or NaN */
67	    else return x;		/* x is integral */
68	} else {
69	    i = ((u_int32_t)(0xffffffff))>>(jj0-20);
70	    if((i1&i)==0) return x;	/* x is integral */
71	    i>>=1;
72	    if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(jj0-20));
73	}
74	INSERT_WORDS(x,i0,i1);
75	w = TWO52[sx]+x;
76	return w-TWO52[sx];
77}
78DEF_STD(rint);
79LDBL_MAYBE_NONSTD_CLONE(rint);
80