1 /* origin: FreeBSD /usr/src/lib/msun/src/s_atanf.c */
3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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
13 * ====================================================
19 static const float atanhi
[] = {
20 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
21 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
22 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
23 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
26 static const float atanlo
[] = {
27 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
28 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
29 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
30 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
33 static const float aT
[] = {
47 GET_FLOAT_WORD(ix
, x
);
50 if (ix
>= 0x4c800000) { /* if |x| >= 2**26 */
53 z
= atanhi
[3] + 0x1p
-120f
;
56 if (ix
< 0x3ee00000) { /* |x| < 0.4375 */
57 if (ix
< 0x39800000) { /* |x| < 2**-12 */
59 /* raise underflow for subnormal x */
66 if (ix
< 0x3f980000) { /* |x| < 1.1875 */
67 if (ix
< 0x3f300000) { /* 7/16 <= |x| < 11/16 */
69 x
= (2.0f
*x
- 1.0f
)/(2.0f
+ x
);
70 } else { /* 11/16 <= |x| < 19/16 */
72 x
= (x
- 1.0f
)/(x
+ 1.0f
);
75 if (ix
< 0x401c0000) { /* |x| < 2.4375 */
77 x
= (x
- 1.5f
)/(1.0f
+ 1.5f
*x
);
78 } else { /* 2.4375 <= |x| < 2**26 */
84 /* end of argument reduction */
87 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
88 s1
= z
*(aT
[0]+w
*(aT
[2]+w
*aT
[4]));
89 s2
= w
*(aT
[1]+w
*aT
[3]);
92 z
= atanhi
[id
] - ((x
*(s1
+s2
) - atanlo
[id
]) - x
);