xref: /illumos-gate/usr/src/lib/libm/common/C/rint.c (revision ddc0e0b5)
125c28e83SPiotr Jasiukajtis /*
225c28e83SPiotr Jasiukajtis  * CDDL HEADER START
325c28e83SPiotr Jasiukajtis  *
425c28e83SPiotr Jasiukajtis  * The contents of this file are subject to the terms of the
525c28e83SPiotr Jasiukajtis  * Common Development and Distribution License (the "License").
625c28e83SPiotr Jasiukajtis  * You may not use this file except in compliance with the License.
725c28e83SPiotr Jasiukajtis  *
825c28e83SPiotr Jasiukajtis  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
925c28e83SPiotr Jasiukajtis  * or http://www.opensolaris.org/os/licensing.
1025c28e83SPiotr Jasiukajtis  * See the License for the specific language governing permissions
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1225c28e83SPiotr Jasiukajtis  *
1325c28e83SPiotr Jasiukajtis  * When distributing Covered Code, include this CDDL HEADER in each
1425c28e83SPiotr Jasiukajtis  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
1525c28e83SPiotr Jasiukajtis  * If applicable, add the following below this CDDL HEADER, with the
1625c28e83SPiotr Jasiukajtis  * fields enclosed by brackets "[]" replaced with your own identifying
1725c28e83SPiotr Jasiukajtis  * information: Portions Copyright [yyyy] [name of copyright owner]
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2025c28e83SPiotr Jasiukajtis  */
2125c28e83SPiotr Jasiukajtis /*
2225c28e83SPiotr Jasiukajtis  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
2325c28e83SPiotr Jasiukajtis  */
2425c28e83SPiotr Jasiukajtis /*
2525c28e83SPiotr Jasiukajtis  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
2625c28e83SPiotr Jasiukajtis  * Use is subject to license terms.
2725c28e83SPiotr Jasiukajtis  */
2825c28e83SPiotr Jasiukajtis 
29*ddc0e0b5SRichard Lowe #pragma weak __rint = rint
3025c28e83SPiotr Jasiukajtis 
3125c28e83SPiotr Jasiukajtis /*
3225c28e83SPiotr Jasiukajtis  * rint(x) return x rounded to integral according to the rounding direction
3325c28e83SPiotr Jasiukajtis  * rint(x) returns result with the same sign as x's,  including 0.0.
3425c28e83SPiotr Jasiukajtis  */
3525c28e83SPiotr Jasiukajtis 
3625c28e83SPiotr Jasiukajtis #include "libm.h"
3725c28e83SPiotr Jasiukajtis 
3825c28e83SPiotr Jasiukajtis #if defined(__i386) && !defined(__amd64) && (!defined(__FLT_EVAL_METHOD__) || \
3925c28e83SPiotr Jasiukajtis 	__FLT_EVAL_METHOD__ != 0)
4025c28e83SPiotr Jasiukajtis extern enum fp_precision_type __swapRP(enum fp_precision_type);
4125c28e83SPiotr Jasiukajtis #define	DECLRP(x)	enum fp_precision_type x;
4225c28e83SPiotr Jasiukajtis #define	SWAPRP(new, x)	x = __swapRP(new);
4325c28e83SPiotr Jasiukajtis #define	RESTRP(x)	(void) __swapRP(x);
4425c28e83SPiotr Jasiukajtis #else
4525c28e83SPiotr Jasiukajtis #define	DECLRP(x)
4625c28e83SPiotr Jasiukajtis #define	SWAPRP(new, x)
4725c28e83SPiotr Jasiukajtis #define	RESTRP(x)
4825c28e83SPiotr Jasiukajtis #endif
4925c28e83SPiotr Jasiukajtis 
5025c28e83SPiotr Jasiukajtis static const double
5125c28e83SPiotr Jasiukajtis 	two52 = 4503599627370496.0,
5225c28e83SPiotr Jasiukajtis 	zero = 0.0,
5325c28e83SPiotr Jasiukajtis 	one = 1.0;
5425c28e83SPiotr Jasiukajtis 
5525c28e83SPiotr Jasiukajtis double
rint(double x)5625c28e83SPiotr Jasiukajtis rint(double x) {
5725c28e83SPiotr Jasiukajtis 	DECLRP(rp)
5825c28e83SPiotr Jasiukajtis 	double	t, w;
5925c28e83SPiotr Jasiukajtis 	int	ix, hx;
6025c28e83SPiotr Jasiukajtis 
6125c28e83SPiotr Jasiukajtis 	ix = ((int *)&x)[HIWORD];
6225c28e83SPiotr Jasiukajtis 	hx = ix & ~0x80000000;
6325c28e83SPiotr Jasiukajtis 
6425c28e83SPiotr Jasiukajtis 	if (hx >= 0x43300000)
6525c28e83SPiotr Jasiukajtis 		return (x * one);
6625c28e83SPiotr Jasiukajtis 	t = (ix < 0)? -two52 : two52;
6725c28e83SPiotr Jasiukajtis 	SWAPRP(fp_double, rp)		/* set precision mode to double */
6825c28e83SPiotr Jasiukajtis 	w = x + t;			/* x+sign(x)*2**52 rounded */
6925c28e83SPiotr Jasiukajtis 	RESTRP(rp)			/* restore precision mode */
7025c28e83SPiotr Jasiukajtis 	if (w == t)
7125c28e83SPiotr Jasiukajtis 		return ((ix < 0)? -zero : zero);
7225c28e83SPiotr Jasiukajtis 	return (w - t);
7325c28e83SPiotr Jasiukajtis }