12116Sjkh/* e_acosf.c -- float version of e_acos.c.
22116Sjkh * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
32116Sjkh */
42116Sjkh
52116Sjkh/*
62116Sjkh * ====================================================
72116Sjkh * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
82116Sjkh *
92116Sjkh * Developed at SunPro, a Sun Microsystems, Inc. business.
102116Sjkh * Permission to use, copy, modify, and distribute this
118870Srgrimes * software is freely granted, provided that this notice
122116Sjkh * is preserved.
132116Sjkh * ====================================================
142116Sjkh */
152116Sjkh
16176451Sdas#include <sys/cdefs.h>
17176451Sdas__FBSDID("$FreeBSD$");
182116Sjkh
192116Sjkh#include "math.h"
202116Sjkh#include "math_private.h"
212116Sjkh
228870Srgrimesstatic const float
232116Sjkhone =  1.0000000000e+00, /* 0x3F800000 */
242116Sjkhpi =  3.1415925026e+00, /* 0x40490fda */
25181062Sdaspio2_hi =  1.5707962513e+00; /* 0x3fc90fda */
26181062Sdasstatic volatile float
27181062Sdaspio2_lo =  7.5497894159e-08; /* 0x33a22168 */
28181062Sdasstatic const float
29181100SdaspS0 =  1.6666586697e-01,
30181100SdaspS1 = -4.2743422091e-02,
31181100SdaspS2 = -8.6563630030e-03,
32181100SdasqS1 = -7.0662963390e-01;
332116Sjkh
3497407Salfredfloat
3597407Salfred__ieee754_acosf(float x)
362116Sjkh{
372116Sjkh	float z,p,q,r,w,s,c,df;
382116Sjkh	int32_t hx,ix;
392116Sjkh	GET_FLOAT_WORD(hx,x);
402116Sjkh	ix = hx&0x7fffffff;
41181257Sdas	if(ix>=0x3f800000) {		/* |x| >= 1 */
42181257Sdas	    if(ix==0x3f800000) {	/* |x| == 1 */
43181257Sdas		if(hx>0) return 0.0;	/* acos(1) = 0 */
44181257Sdas		else return pi+(float)2.0*pio2_lo;	/* acos(-1)= pi */
45181257Sdas	    }
462116Sjkh	    return (x-x)/(x-x);		/* acos(|x|>1) is NaN */
472116Sjkh	}
482116Sjkh	if(ix<0x3f000000) {	/* |x| < 0.5 */
49181100Sdas	    if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/
502116Sjkh	    z = x*x;
51181100Sdas	    p = z*(pS0+z*(pS1+z*pS2));
52181100Sdas	    q = one+z*qS1;
532116Sjkh	    r = p/q;
542116Sjkh	    return pio2_hi - (x - (pio2_lo-x*r));
552116Sjkh	} else  if (hx<0) {		/* x < -0.5 */
562116Sjkh	    z = (one+x)*(float)0.5;
57181100Sdas	    p = z*(pS0+z*(pS1+z*pS2));
58181100Sdas	    q = one+z*qS1;
59181257Sdas	    s = sqrtf(z);
602116Sjkh	    r = p/q;
612116Sjkh	    w = r*s-pio2_lo;
622116Sjkh	    return pi - (float)2.0*(s+w);
632116Sjkh	} else {			/* x > 0.5 */
642116Sjkh	    int32_t idf;
652116Sjkh	    z = (one-x)*(float)0.5;
66181257Sdas	    s = sqrtf(z);
672116Sjkh	    df = s;
682116Sjkh	    GET_FLOAT_WORD(idf,df);
692116Sjkh	    SET_FLOAT_WORD(df,idf&0xfffff000);
702116Sjkh	    c  = (z-df*df)/(s+df);
71181100Sdas	    p = z*(pS0+z*(pS1+z*pS2));
72181100Sdas	    q = one+z*qS1;
732116Sjkh	    r = p/q;
742116Sjkh	    w = r*s+c;
752116Sjkh	    return (float)2.0*(df+w);
762116Sjkh	}
772116Sjkh}
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