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/* origin: FreeBSD /usr/src/lib/msun/src/e_acosf.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@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.
* ====================================================
*/
#include "libm.h"
static const float
pi = 3.1415925026e+00, /* 0x40490fda */
pio2_hi = 1.5707962513e+00; /* 0x3fc90fda */
static const volatile float
pio2_lo = 7.5497894159e-08; /* 0x33a22168 */
static const float
pS0 = 1.6666586697e-01,
pS1 = -4.2743422091e-02,
pS2 = -8.6563630030e-03,
qS1 = -7.0662963390e-01;
float acosf(float x)
{
float z,p,q,r,w,s,c,df;
int32_t hx,ix;
GET_FLOAT_WORD(hx, x);
ix = hx & 0x7fffffff;
if (ix >= 0x3f800000) { /* |x| >= 1 */
if (ix == 0x3f800000) { /* |x| == 1 */
if (hx > 0) return 0.0f; /* acos(1) = 0 */
return pi + 2.0f*pio2_lo; /* acos(-1)= pi */
}
return (x-x)/(x-x); /* acos(|x|>1) is NaN */
}
if (ix < 0x3f000000) { /* |x| < 0.5 */
if (ix <= 0x32800000) /* |x| < 2**-26 */
return pio2_hi + pio2_lo;
z = x*x;
p = z*(pS0+z*(pS1+z*pS2));
q = 1.0f+z*qS1;
r = p/q;
return pio2_hi - (x - (pio2_lo-x*r));
} else if (hx < 0) { /* x < -0.5 */
z = (1.0f+x)*0.5f;
p = z*(pS0+z*(pS1+z*pS2));
q = 1.0f+z*qS1;
s = sqrtf(z);
r = p/q;
w = r*s-pio2_lo;
return pi - 2.0f*(s+w);
} else { /* x > 0.5 */
int32_t idf;
z = (1.0f-x)*0.5f;
s = sqrtf(z);
df = s;
GET_FLOAT_WORD(idf,df);
SET_FLOAT_WORD(df,idf&0xfffff000);
c = (z-df*df)/(s+df);
p = z*(pS0+z*(pS1+z*pS2));
q = 1.0f+z*qS1;
r = p/q;
w = r*s+c;
return 2.0f*(df+w);
}
}
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