s_rintf.c revision 97409 
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 97409 2002-05-28 17:51:46Z 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
35	float rintf(float x)
36{
37	int32_t i0,j0,sx;
38	u_int32_t i,i1;
39	float w,t;
40	GET_FLOAT_WORD(i0,x);
41	sx = (i0>>31)&1;
42	j0 = ((i0>>23)&0xff)-0x7f;
43	if(j0<23) {
44	    if(j0<0) {
45		if((i0&0x7fffffff)==0) return x;
46		i1 = (i0&0x07fffff);
47		i0 &= 0xfff00000;
48		i0 |= ((i1|-i1)>>9)&0x400000;
49		SET_FLOAT_WORD(x,i0);
50	        w = TWO23[sx]+x;
51	        t =  w-TWO23[sx];
52		GET_FLOAT_WORD(i0,t);
53		SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
54	        return t;
55	    } else {
56		i = (0x007fffff)>>j0;
57		if((i0&i)==0) return x; /* x is integral */
58		i>>=1;
59		if((i0&i)!=0) i0 = (i0&(~i))|((0x100000)>>j0);
60	    }
61	} else {
62	    if(j0==0x80) return x+x;	/* inf or NaN */
63	    else return x;		/* x is integral */
64	}
65	SET_FLOAT_WORD(x,i0);
66	w = TWO23[sx]+x;
67	return w-TWO23[sx];
68}
69