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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 __scalbn = scalbn
#include "libm.h"
static const double
one = 1.0,
huge = 1.0e300,
tiny = 1.0e-300,
twom54 = 5.5511151231257827021181583404541015625e-17;
#if defined(__x86)
static const double two52 = 4503599627370496.0;
#else
/*
* Normalize non-zero subnormal x and return biased exponent of x in [-51,0]
*/
static int
ilogb_biased(unsigned *px) {
int s = 52;
unsigned v = px[HIWORD] & ~0x80000000, w = px[LOWORD], t = v;
if (t)
s -= 32;
else
t = w;
if (t & 0xffff0000)
s -= 16, t >>= 16;
if (t & 0xff00)
s -= 8, t >>= 8;
if (t & 0xf0)
s -= 4, t >>= 4;
t <<= 1;
s -= (0xffffaa50 >> t) & 0x3;
if (s < 32) {
v = (v << s) | w >> (32 - s);
w <<= s;
} else {
v = w << (s - 32);
w = 0;
}
px[HIWORD] = (px[HIWORD] & 0x80000000) | v;
px[LOWORD] = w;
return (1 - s);
}
#endif /* defined(__x86) */
double
scalbn(double x, int n) {
int *px, ix, hx, k;
px = (int *)&x;
ix = px[HIWORD];
hx = ix & ~0x80000000;
k = hx >> 20;
if (k == 0x7ff) /* x is inf or NaN */
return (x * one);
if (k == 0) {
if ((hx | px[LOWORD]) == 0 || n == 0)
return (x);
#if defined(__x86)
x *= two52;
ix = px[HIWORD];
k = ((ix & ~0x80000000) >> 20) - 52;
#else
k = ilogb_biased((unsigned *)px);
ix = px[HIWORD];
#endif
/* now k is in the range -51..0 */
k += n;
if (k > n) /* integer overflow occurred */
k = -100;
} else {
/* k is in the range 1..1023 */
k += n;
if (k < n) /* integer overflow occurred */
k = 0x7ff;
}
if (k > 0x7fe)
return (huge * ((ix < 0)? -huge : huge));
if (k < 1) {
if (k <= -54)
return (tiny * ((ix < 0)? -tiny : tiny));
k += 54;
px[HIWORD] = (ix & ~0x7ff00000) | (k << 20);
return (x * twom54);
}
px[HIWORD] = (ix & ~0x7ff00000) | (k << 20);
return (x);
}
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