s_rintf.c revision 153046 
1/* s_rintf.c -- float version of s_rint.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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#ifndef lint
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/s_rintf.c 153046 2005-12-03 09:00:29Z bde $";
18#endif
19
20#include <sys/types.h>
21#include "math.h"
22#include "math_private.h"
23
24static const float
25TWO23[2]={
26  8.3886080000e+06, /* 0x4b000000 */
27 -8.3886080000e+06, /* 0xcb000000 */
28};
29
30float
31rintf(float x)
32{
33	int32_t i0,j0,sx;
34	volatile float w,t;	/* volatile works around gcc bug */
35	GET_FLOAT_WORD(i0,x);
36	sx = (i0>>31)&1;
37	j0 = ((i0>>23)&0xff)-0x7f;
38	if(j0<23) {
39	    if(j0<0) {
40		if((i0&0x7fffffff)==0) return x;
41	        w = TWO23[sx]+x;
42	        t =  w-TWO23[sx];
43		GET_FLOAT_WORD(i0,t);
44		SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
45	        return t;
46	    }
47	    w = TWO23[sx]+x;
48	    return w-TWO23[sx];
49	}
50	if(j0==0x80) return x+x;	/* inf or NaN */
51	else return x;			/* x is integral */
52}
53