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[] = {
41 static const float huge = 1.0e30;
48 GET_FLOAT_WORD(hx, x);
50 if (ix >= 0x4c800000) { /* if |x| >= 2**26 */
51 if (ix > 0x7f800000) /* NaN */
54 return atanhi[3] + *(volatile float *)&atanlo[3];
56 return -atanhi[3] - *(volatile float *)&atanlo[3];
58 if (ix < 0x3ee00000) { /* |x| < 0.4375 */
59 if (ix < 0x39800000) { /* |x| < 2**-12 */
67 if (ix < 0x3f980000) { /* |x| < 1.1875 */
68 if (ix < 0x3f300000) { /* 7/16 <= |x| < 11/16 */
70 x = (2.0f*x - 1.0f)/(2.0f + x);
71 } else { /* 11/16 <= |x| < 19/16 */
73 x = (x - 1.0f)/(x + 1.0f);
76 if (ix < 0x401c0000) { /* |x| < 2.4375 */
78 x = (x - 1.5f)/(1.0f + 1.5f*x);
79 } else { /* 2.4375 <= |x| < 2**26 */
85 /* end of argument reduction */
88 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
89 s1 = z*(aT[0]+w*(aT[2]+w*aT[4]));
90 s2 = w*(aT[1]+w*aT[3]);
93 z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
94 return hx < 0 ? -z : z;