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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 __exp2 = exp2
/* INDENT OFF */
/*
* exp2(x)
* Code by K.C. Ng for SUN 4.0 libm.
* Method :
* exp2(x) = 2**x = 2**((x-anint(x))+anint(x))
* = 2**anint(x)*2**(x-anint(x))
* = 2**anint(x)*exp((x-anint(x))*ln2)
*/
/* INDENT ON */
#include "libm.h"
static const double C[] = {
0.0,
1.0,
0.5,
6.93147180559945286227e-01,
1.0e300,
1.0e-300,
};
#define zero C[0]
#define one C[1]
#define half C[2]
#define ln2 C[3]
#define huge C[4]
#define tiny C[5]
double
exp2(double x) {
int ix, hx, k;
double t;
ix = ((int *)&x)[HIWORD];
hx = ix & ~0x80000000;
if (hx >= 0x4090e000) { /* |x| >= 1080 or x is nan */
if (hx >= 0x7ff00000) { /* x is inf or nan */
if (ix == 0xfff00000 && ((int *)&x)[LOWORD] == 0)
return (zero);
return (x * x);
}
t = (ix < 0)? tiny : huge;
return (t * t);
}
if (hx < 0x3fe00000) { /* |x| < 0.5 */
if (hx < 0x3c000000)
return (one + x);
return (exp(ln2 * x));
}
k = (int)x;
if (x != (double)k)
k = (int)((ix < 0)? x - half : x + half);
return (scalbn(exp(ln2 * (x - (double)k)), k));
}
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