s_rintf.c revision 97413 
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 97413 2002-05-28 18:15:04Z alfred $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23/*
24 * TWO23 is double instead of float to avoid a bug in gcc.  Without
25 * this, gcc thinks that TWO23[sx]+x and w-TWO23[sx] already have float
26 * precision and doesn't clip them to float precision when they are
27 * assigned and returned.
28 */
29static const double
30TWO23[2]={
31  8.3886080000e+06, /* 0x4b000000 */
32 -8.3886080000e+06, /* 0xcb000000 */
33};
34
35float
36rintf(float x)
37{
38	int32_t i0,j0,sx;
39	u_int32_t i,i1;
40	float w,t;
41	GET_FLOAT_WORD(i0,x);
42	sx = (i0>>31)&1;
43	j0 = ((i0>>23)&0xff)-0x7f;
44	if(j0<23) {
45	    if(j0<0) {
46		if((i0&0x7fffffff)==0) return x;
47		i1 = (i0&0x07fffff);
48		i0 &= 0xfff00000;
49		i0 |= ((i1|-i1)>>9)&0x400000;
50		SET_FLOAT_WORD(x,i0);
51	        w = TWO23[sx]+x;
52	        t =  w-TWO23[sx];
53		GET_FLOAT_WORD(i0,t);
54		SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
55	        return t;
56	    } else {
57		i = (0x007fffff)>>j0;
58		if((i0&i)==0) return x; /* x is integral */
59		i>>=1;
60		if((i0&i)!=0) i0 = (i0&(~i))|((0x100000)>>j0);
61	    }
62	} else {
63	    if(j0==0x80) return x+x;	/* inf or NaN */
64	    else return x;		/* x is integral */
65	}
66	SET_FLOAT_WORD(x,i0);
67	w = TWO23[sx]+x;
68	return w-TWO23[sx];
69}
70