ilogbl.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 ilogbl = __ilogbl
#endif
#include "libm.h"
#include "xpg6.h" /* __xpg6 */
#if defined(__sparc)
#define ISNORMALL(k, x) (k != 0x7fff) /* assuming k != 0 */
#define X86PDNRM(k, x)
#define XSCALE_OFFSET 0x406f /* 0x3fff + 112 */
static const long double xscale = 5192296858534827628530496329220096.0L;
/* 2^112 */
#elif defined(__x86)
/*
* if pseudo-denormal, replace by the equivalent normal
*/
#define X86PDNRM(k, x) if (k == 0 && (((int *) &x)[1] & 0x80000000) != 0) \
((int *) &x)[2] |= k = 1
#if defined(HANDLE_UNSUPPORTED) /* assuming k != 0 */
#define ISNORMALL(k, x) (k != 0x7fff && (((int *) &x)[1] & 0x80000000) != 0)
#else
#define ISNORMALL(k, x) (k != 0x7fff)
#endif
#define XSCALE_OFFSET 0x403e /* 0x3fff + 63 */
static const long double xscale = 9223372036854775808.0L; /* 2^63 */
#endif
static int
raise_invalid(int v) { /* SUSv3 requires ilogbl(0,+/-Inf,NaN) raise invalid */
#ifndef lint
if ((__xpg6 & _C99SUSv3_ilogb_0InfNaN_raises_invalid) != 0) {
static const double zero = 0.0;
volatile double dummy;
dummy = zero / zero;
}
#endif
return (v);
}
int
ilogbl(long double x) {
int k = XBIASED_EXP(x);
X86PDNRM(k, x);
if (k == 0) {
if (ISZEROL(x))
return (raise_invalid(0x80000001));
else {
x *= xscale; /* scale up by 2^112 or 2^63 */
return (XBIASED_EXP(x) - XSCALE_OFFSET);
}
} else if (ISNORMALL(k, x))
return (k - 0x3fff);
else
return (raise_invalid(0x7fffffff));
}