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Elliott Hughesa0ee0782013-01-30 19:06:37 -08001/* e_acosf.c -- float version of e_acos.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5/*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
Elliott Hughesa0ee0782013-01-30 19:06:37 -080016#include "math.h"
17#include "math_private.h"
18
19static const float
20one = 1.0000000000e+00, /* 0x3F800000 */
21pi = 3.1415925026e+00, /* 0x40490fda */
22pio2_hi = 1.5707962513e+00; /* 0x3fc90fda */
23static volatile float
24pio2_lo = 7.5497894159e-08; /* 0x33a22168 */
25static const float
26pS0 = 1.6666586697e-01,
27pS1 = -4.2743422091e-02,
28pS2 = -8.6563630030e-03,
29qS1 = -7.0662963390e-01;
30
31float
Elliott Hughes4088e3a2023-08-03 13:33:56 -070032acosf(float x)
Elliott Hughesa0ee0782013-01-30 19:06:37 -080033{
34 float z,p,q,r,w,s,c,df;
35 int32_t hx,ix;
36 GET_FLOAT_WORD(hx,x);
37 ix = hx&0x7fffffff;
38 if(ix>=0x3f800000) { /* |x| >= 1 */
39 if(ix==0x3f800000) { /* |x| == 1 */
40 if(hx>0) return 0.0; /* acos(1) = 0 */
41 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
42 }
43 return (x-x)/(x-x); /* acos(|x|>1) is NaN */
44 }
45 if(ix<0x3f000000) { /* |x| < 0.5 */
46 if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/
47 z = x*x;
48 p = z*(pS0+z*(pS1+z*pS2));
49 q = one+z*qS1;
50 r = p/q;
51 return pio2_hi - (x - (pio2_lo-x*r));
52 } else if (hx<0) { /* x < -0.5 */
53 z = (one+x)*(float)0.5;
54 p = z*(pS0+z*(pS1+z*pS2));
55 q = one+z*qS1;
56 s = sqrtf(z);
57 r = p/q;
58 w = r*s-pio2_lo;
59 return pi - (float)2.0*(s+w);
60 } else { /* x > 0.5 */
61 int32_t idf;
62 z = (one-x)*(float)0.5;
63 s = sqrtf(z);
64 df = s;
65 GET_FLOAT_WORD(idf,df);
66 SET_FLOAT_WORD(df,idf&0xfffff000);
67 c = (z-df*df)/(s+df);
68 p = z*(pS0+z*(pS1+z*pS2));
69 q = one+z*qS1;
70 r = p/q;
71 w = r*s+c;
72 return (float)2.0*(df+w);
73 }
74}