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/* @(#)e_asin.c 1.3 95/01/18 */
/* FreeBSD: head/lib/msun/src/e_asin.c 176451 2008-02-22 02:30:36Z das */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunSoft, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* See comments in e_asin.c.
* Converted to long double by David Schultz <das@FreeBSD.ORG>.
*/
#include <float.h>
#include "invtrig.h"
#include "math.h"
#include "math_private.h"
static const long double
one = 1.00000000000000000000e+00,
huge = 1.000e+300;
long double
asinl(long double x)
{
union IEEEl2bits u;
long double t=0.0,w,p,q,c,r,s;
int16_t expsign, expt;
u.e = x;
expsign = u.xbits.expsign;
expt = expsign & 0x7fff;
if(expt >= BIAS) { /* |x|>= 1 */
if(expt==BIAS && ((u.bits.manh&~LDBL_NBIT)|u.bits.manl)==0)
/* asin(1)=+-pi/2 with inexact */
return x*pio2_hi+x*pio2_lo;
return (x-x)/(x-x); /* asin(|x|>1) is NaN */
} else if (expt<BIAS-1) { /* |x|<0.5 */
if(expt<ASIN_LINEAR) { /* if |x| is small, asinl(x)=x */
if(huge+x>one) return x;/* return x with inexact if x!=0*/
} else
t = x*x;
p = P(t);
q = Q(t);
w = p/q;
return x+x*w;
}
/* 1> |x|>= 0.5 */
w = one-fabsl(x);
t = w*0.5;
p = P(t);
q = Q(t);
s = sqrtl(t);
if(u.bits.manh>=THRESH) { /* if |x| is close to 1 */
w = p/q;
t = pio2_hi-(2.0*(s+s*w)-pio2_lo);
} else {
u.e = s;
u.bits.manl = 0;
w = u.e;
c = (t-w*w)/(s+w);
r = p/q;
p = 2.0*s*r-(pio2_lo-2.0*c);
q = pio4_hi-2.0*w;
t = pio4_hi-(p-q);
}
if(expsign>0) return t; else return -t;
}
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