round.c revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#if defined(ELFOBJ)
#pragma weak round = __round
#endif
#include "libm.h"
double
round(double x) {
union {
unsigned i[2];
double d;
} xx;
unsigned hx, sx, i;
xx.d = x;
hx = xx.i[HIWORD] & ~0x80000000;
sx = xx.i[HIWORD] & 0x80000000;
if (hx < 0x43300000) { /* |x| < 2^52 */
if (hx < 0x3ff00000) { /* |x| < 1 */
if (hx >= 0x3fe00000)
return (sx ? -1.0 : 1.0);
return (sx ? -0.0 : 0.0);
}
/* round x at the integer bit */
if (hx < 0x41300000) {
i = 1 << (0x412 - (hx >> 20));
xx.i[HIWORD] = (xx.i[HIWORD] + i) & ~(i | (i - 1));
xx.i[LOWORD] = 0;
} else {
i = 1 << (0x432 - (hx >> 20));
xx.i[LOWORD] += i;
if (xx.i[LOWORD] < i)
xx.i[HIWORD]++;
xx.i[LOWORD] &= ~(i | (i - 1));
}
return (xx.d);
} else if (hx < 0x7ff00000)
return (x);
else
#if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
return (hx >= 0x7ff80000 ? x : x + x);
/* assumes sparc-like QNaN */
#else
return (x + x);
#endif
}