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/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
* scalbn (double x, int n)
* scalbn(x,n) returns x* 2**n computed by exponent
* manipulation rather than by actually performing an
* exponentiation or a multiplication.
*/
#include <math.h>
#include <math_private.h>
static const double
two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
huge = 1.0e+300,
tiny = 1.0e-300;
double
__scalbn (double x, int n)
{
int32_t k, hx, lx;
EXTRACT_WORDS (hx, lx, x);
k = (hx & 0x7ff00000) >> 20; /* extract exponent */
if (__builtin_expect (k == 0, 0)) /* 0 or subnormal x */
{
if ((lx | (hx & 0x7fffffff)) == 0)
return x; /* +-0 */
x *= two54;
GET_HIGH_WORD (hx, x);
k = ((hx & 0x7ff00000) >> 20) - 54;
}
if (__builtin_expect (k == 0x7ff, 0))
return x + x; /* NaN or Inf */
if (__builtin_expect (n < -50000, 0))
return tiny * __copysign (tiny, x); /*underflow*/
if (__builtin_expect (n > 50000 || k + n > 0x7fe, 0))
return huge * __copysign (huge, x); /* overflow */
/* Now k and n are bounded we know that k = k+n does not
overflow. */
k = k + n;
if (__builtin_expect (k > 0, 1)) /* normal result */
{
SET_HIGH_WORD (x, (hx & 0x800fffff) | (k << 20)); return x;
}
if (k <= -54)
return tiny * __copysign (tiny, x); /*underflow*/
k += 54; /* subnormal result */
SET_HIGH_WORD (x, (hx & 0x800fffff) | (k << 20));
return x * twom54;
}
weak_alias (__scalbn, scalbn)
#ifdef NO_LONG_DOUBLE
strong_alias (__scalbn, __scalbnl)
weak_alias (__scalbn, scalbnl)
#endif
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