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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 __scalbln = scalbln
#include "libm.h"
#include <float.h> /* DBL_MAX, DBL_MIN */
static const double 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
scalbln(double x, long n) {
int *px = (int *) &x, ix, k;
ix = px[HIWORD] & ~0x80000000;
k = ix >> 20;
if (k == 0x7ff)
#if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
return ((px[HIWORD] & 0x80000) != 0 ? x : x + x);
/* assumes sparc-like QNaN */
#else
return (x + x);
#endif
if ((px[LOWORD] | ix) == 0 || n == 0)
return (x);
if (k == 0) {
#if defined(__x86)
x *= two52;
k = ((px[HIWORD] & ~0x80000000) >> 20) - 52;
#else
k = ilogb_biased((unsigned *) px);
#endif
}
k += (int) n;
if (n > 5000 || k > 0x7fe)
return (DBL_MAX * copysign(DBL_MAX, x));
if (n < -5000 || k <= -54)
return (DBL_MIN * copysign(DBL_MIN, x));
if (k > 0) {
px[HIWORD] = (px[HIWORD] & ~0x7ff00000) | (k << 20);
return (x);
}
k += 54;
px[HIWORD] = (px[HIWORD] & ~0x7ff00000) | (k << 20);
return (x * twom54);
}
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