mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-27 07:20:11 +00:00
62 lines
1.8 KiB
C
62 lines
1.8 KiB
C
/* s_scalbnl.c -- long double version of s_scalbn.c.
|
|
* Conversion to long double by Ulrich Drepper,
|
|
* Cygnus Support, drepper@cygnus.com.
|
|
*/
|
|
|
|
/*
|
|
* ====================================================
|
|
* 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 <math.h>
|
|
#include <math_private.h>
|
|
|
|
static const long double
|
|
two63 = 4.50359962737049600000e+15,
|
|
twom63 = 1.08420217248550443400e-19,
|
|
huge = 1.0e+4900L,
|
|
tiny = 1.0e-4900L;
|
|
|
|
long double
|
|
__scalblnl (long double x, long int n)
|
|
{
|
|
int32_t k,es,hx,lx;
|
|
GET_LDOUBLE_WORDS(es,hx,lx,x);
|
|
k = es&0x7fff; /* extract exponent */
|
|
if (__builtin_expect(k==0, 0)) { /* 0 or subnormal x */
|
|
if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
|
|
x *= two63;
|
|
GET_LDOUBLE_EXP(es,x);
|
|
k = (hx&0x7fff) - 63;
|
|
}
|
|
if (__builtin_expect(k==0x7fff, 0)) return x+x; /* NaN or Inf */
|
|
if (__builtin_expect(n< -50000, 0))
|
|
return tiny*__copysignl(tiny,x);
|
|
if (__builtin_expect(n> 50000 || k+n > 0x7ffe, 0))
|
|
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 (__builtin_expect(k > 0, 1)) /* normal result */
|
|
{SET_LDOUBLE_EXP(x,(es&0x8000)|k); return x;}
|
|
if (k <= -63)
|
|
return tiny*__copysignl(tiny,x); /*underflow*/
|
|
k += 63; /* subnormal result */
|
|
SET_LDOUBLE_EXP(x,(es&0x8000)|k);
|
|
return x*twom63;
|
|
}
|
|
weak_alias (__scalblnl, scalblnl)
|