exp2l.c revision ddc0e0b53c661f6e439e3b7072b3ef353eadb4af
/*
* 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 __exp2l = exp2l
#include "libm.h"
#include "longdouble.h"
/*
* exp2l(x) = 2**x = 2**((x-anint(x))+anint(x))
* = 2**anint(x)*2**(x-anint(x))
* = 2**anint(x)*exp((x-anint(x))*ln2)
*/
#define TINY 1.0e-20L /* single: 1e-5, double: 1e-10, quad: 1e-20 */
#define OVFLEXP 16400 /* single: 130, double 1030, quad: 16400 */
#define UNFLEXP -16520 /* single:-155, double -1080, quad:-16520 */
static const long double
zero = 0.0L,
tiny = TINY * TINY,
half = 0.5L,
ln2 = 6.931471805599453094172321214581765680755e-0001L,
one = 1.0L;
static const int
ovflexp = OVFLEXP,
unflexp = UNFLEXP;
long double
exp2l(long double x) {
long double t;
if (!finitel(x)) {
if (isnanl(x) || x > zero)
return (x + x);
else
return (zero);
}
t = fabsl(x);
if (t < half) {
if (t < tiny)
return (one + x);
else
return (expl(ln2 * x));
}
t = anintl(x);
if (t < ovflexp) {
if (t >= unflexp)
return (scalbnl(expl(ln2 * (x - t)), (int) t));
else
return (scalbnl(one, unflexp)); /* underflow */
} else
return (scalbnl(one, ovflexp)); /* overflow */
}