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/* s_scalbnl.c -- long double version of s_scalbn.c.
*/
/* @(#)s_scalbn.c 5.1 93/09/24 */
/*
* ====================================================
* 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.
* ====================================================
*/
#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: $";
#endif
/*
* scalbnl (long double x, int n)
* scalbnl(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>
#include <math_ldbl_opt.h>
static const long double
twolm54 = 5.55111512312578270212e-17, /* 0x3C90000000000000, 0 */
huge = 1.0E+300L,
tiny = 1.0E-300L;
static const double
two54 = 1.80143985094819840000e+16, /* 0x4350000000000000 */
twom54 = 5.55111512312578270212e-17; /* 0x3C90000000000000 */
long double __scalbnl (long double x, int n)
{
int64_t k,l,hx,lx;
union { int64_t i; double d; } u;
double xhi, xlo;
ldbl_unpack (x, &xhi, &xlo);
EXTRACT_WORDS64 (hx, xhi);
EXTRACT_WORDS64 (lx, xlo);
k = (hx>>52)&0x7ff; /* extract exponent */
l = (lx>>52)&0x7ff;
if (k==0) { /* 0 or subnormal x */
if ((hx&0x7fffffffffffffffULL)==0) return x; /* +-0 */
u.i = hx;
u.d *= two54;
hx = u.i;
k = ((hx>>52)&0x7ff) - 54;
}
else if (k==0x7ff) return x+x; /* NaN or Inf */
if (n< -50000) return tiny*copysignl(tiny,x); /*underflow */
if (n> 50000 || k+n > 0x7fe)
return huge*copysignl(huge,x); /* overflow */
/* Now k and n are bounded we know that k = k+n does not
overflow. */
k = k+n;
if (k > 0) { /* normal result */
hx = (hx&0x800fffffffffffffULL)|(k<<52);
if ((lx & 0x7fffffffffffffffULL) == 0) { /* low part +-0 */
INSERT_WORDS64 (xhi, hx);
INSERT_WORDS64 (xlo, lx);
x = ldbl_pack (xhi, xlo);
return x;
}
if (l == 0) { /* low part subnormal */
u.i = lx;
u.d *= two54;
lx = u.i;
l = ((lx>>52)&0x7ff) - 54;
}
l = l + n;
if (l > 0)
lx = (lx&0x800fffffffffffffULL)|(l<<52);
else if (l <= -54)
lx = (lx&0x8000000000000000ULL);
else {
l += 54;
u.i = (lx&0x800fffffffffffffULL)|(l<<52);
u.d *= twom54;
lx = u.i;
}
INSERT_WORDS64 (xhi, hx);
INSERT_WORDS64 (xlo, lx);
x = ldbl_pack (xhi, xlo);
return x;
}
if (k <= -54)
return tiny*copysignl(tiny,x); /*underflow*/
k += 54; /* subnormal result */
lx &= 0x8000000000000000ULL;
hx &= 0x800fffffffffffffULL;
INSERT_WORDS64 (xhi, hx|(k<<52));
INSERT_WORDS64 (xlo, lx);
x = ldbl_pack (xhi, xlo);
return x*twolm54;
}
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