61 lines
2 KiB
C
61 lines
2 KiB
C
/* s_scalbnl.c -- long double version of s_scalbn.c.
|
|
* Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
|
|
*/
|
|
|
|
/* @(#)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
|
|
|
|
/*
|
|
* scalbnq (long double x, int n)
|
|
* scalbnq(x,n) returns x* 2**n computed by exponent
|
|
* manipulation rather than by actually performing an
|
|
* exponentiation or a multiplication.
|
|
*/
|
|
|
|
#include "quadmath-imp.h"
|
|
|
|
static const __float128
|
|
two114 = 2.0769187434139310514121985316880384E+34Q, /* 0x4071000000000000, 0 */
|
|
twom114 = 4.8148248609680896326399448564623183E-35Q, /* 0x3F8D000000000000, 0 */
|
|
huge = 1.0E+4900Q,
|
|
tiny = 1.0E-4900Q;
|
|
|
|
__float128 scalbnq (__float128 x, int n)
|
|
{
|
|
int64_t k,hx,lx;
|
|
GET_FLT128_WORDS64(hx,lx,x);
|
|
k = (hx>>48)&0x7fff; /* extract exponent */
|
|
if (k==0) { /* 0 or subnormal x */
|
|
if ((lx|(hx&0x7fffffffffffffffULL))==0) return x; /* +-0 */
|
|
x *= two114;
|
|
GET_FLT128_MSW64(hx,x);
|
|
k = ((hx>>48)&0x7fff) - 114;
|
|
}
|
|
if (k==0x7fff) return x+x; /* NaN or Inf */
|
|
if (n< -50000) return tiny*copysignq(tiny,x); /*underflow*/
|
|
if (n> 50000 || k+n > 0x7ffe)
|
|
return huge*copysignq(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 */
|
|
{SET_FLT128_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48)); return x;}
|
|
if (k <= -114)
|
|
return tiny*copysignq(tiny,x); /*underflow*/
|
|
k += 114; /* subnormal result */
|
|
SET_FLT128_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48));
|
|
return x*twom114;
|
|
}
|