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/*
* 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.
*/
#pragma weak __ilogb = ilogb
#include "libm.h"
#include "xpg6.h" /* __xpg6 */
#if defined(__x86)
static const double two52 = 4503599627370496.0;
#else
/*
* v: high part of a non-zero subnormal |x|; w: low part of |x|
*/
static int
ilogb_subnormal(unsigned v, unsigned w) {
int r = -1022 - 52;
if (v)
r += 32;
else
v = w;
if (v & 0xffff0000)
r += 16, v >>= 16;
if (v & 0xff00)
r += 8, v >>= 8;
if (v & 0xf0)
r += 4, v >>= 4;
v <<= 1;
return (r + ((0xffffaa50 >> v) & 0x3));
}
#endif /* defined(__x86) */
static int
raise_invalid(int v) { /* SUSv3 requires ilogb(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
ilogb(double x) {
int *px = (int *) &x, k = px[HIWORD] & ~0x80000000;
if (k < 0x00100000) {
if ((px[LOWORD] | k) == 0)
return (raise_invalid(0x80000001));
else {
#if defined(__x86)
x *= two52;
return (((px[HIWORD] & 0x7ff00000) >> 20) - 1075);
#else
return (ilogb_subnormal(k, px[LOWORD]));
#endif
}
} else if (k < 0x7ff00000)
return ((k >> 20) - 1023);
else
return (raise_invalid(0x7fffffff));
}
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