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/* origin: FreeBSD /usr/src/lib/msun/src/s_scalbnl.c */
/*
* ====================================================
* 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.
* ====================================================
*/
/*
* 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 "libm.h"
#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double scalbnl(long double x, int n)
{
return scalbn(x, n);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
static const long double
huge = 0x1p16000L,
tiny = 0x1p-16000L;
long double scalbnl(long double x, int n)
{
union IEEEl2bits u;
int k;
u.e = x;
k = u.bits.exp; /* extract exponent */
if (k == 0) { /* 0 or subnormal x */
if ((u.bits.manh|u.bits.manl) == 0) /* +-0 */
return x;
u.e *= 0x1p128;
k = u.bits.exp - 128;
if (n < -50000)
return tiny*x; /*underflow*/
}
if (k == 0x7fff) /* NaN or Inf */
return x + x;
k = k + n;
if (k >= 0x7fff)
return huge*copysignl(huge, x); /* overflow */
if (k > 0) { /* normal result */
u.bits.exp = k;
return u.e;
}
if (k <= -128)
if (n > 50000) /* in case integer overflow in n+k */
return huge*copysign(huge, x); /*overflow*/
return tiny*copysign(tiny, x); /*underflow*/
k += 128; /* subnormal result */
u.bits.exp = k;
return u.e*0x1p-128;
}
#endif
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