1 /* 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
16 #include <sys/cdefs.h>
17 __FBSDID("$FreeBSD$");
18
19 #include "math.h"
20 #include "math_private.h"
21
22 static const float
23 one = 1.0000000000e+00, /* 0x3F800000 */
24 pi = 3.1415925026e+00, /* 0x40490fda */
25 pio2_hi = 1.5707962513e+00; /* 0x3fc90fda */
26 static volatile float
27 pio2_lo = 7.5497894159e-08; /* 0x33a22168 */
28 static const float
29 pS0 = 1.6666586697e-01,
30 pS1 = -4.2743422091e-02,
31 pS2 = -8.6563630030e-03,
32 qS1 = -7.0662963390e-01;
33
34 float
__ieee754_acosf(float x)35 __ieee754_acosf(float x)
36 {
37 float z,p,q,r,w,s,c,df;
38 int32_t hx,ix;
39 GET_FLOAT_WORD(hx,x);
40 ix = hx&0x7fffffff;
41 if(ix>=0x3f800000) { /* |x| >= 1 */
42 if(ix==0x3f800000) { /* |x| == 1 */
43 if(hx>0) return 0.0; /* acos(1) = 0 */
44 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
45 }
46 return (x-x)/(x-x); /* acos(|x|>1) is NaN */
47 }
48 if(ix<0x3f000000) { /* |x| < 0.5 */
49 if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/
50 z = x*x;
51 p = z*(pS0+z*(pS1+z*pS2));
52 q = one+z*qS1;
53 r = p/q;
54 return pio2_hi - (x - (pio2_lo-x*r));
55 } else if (hx<0) { /* x < -0.5 */
56 z = (one+x)*(float)0.5;
57 p = z*(pS0+z*(pS1+z*pS2));
58 q = one+z*qS1;
59 s = sqrtf(z);
60 r = p/q;
61 w = r*s-pio2_lo;
62 return pi - (float)2.0*(s+w);
63 } else { /* x > 0.5 */
64 int32_t idf;
65 z = (one-x)*(float)0.5;
66 s = sqrtf(z);
67 df = s;
68 GET_FLOAT_WORD(idf,df);
69 SET_FLOAT_WORD(df,idf&0xfffff000);
70 c = (z-df*df)/(s+df);
71 p = z*(pS0+z*(pS1+z*pS2));
72 q = one+z*qS1;
73 r = p/q;
74 w = r*s+c;
75 return (float)2.0*(df+w);
76 }
77 }
78