1 /* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.c */
2 /*
3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
4 * Optimized by Bruce D. Evans.
5 */
6 /*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17 #include "libm.h"
18
19 /* Small multiples of pi/2 rounded to double precision. */
20 static const double
21 t1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
22 t2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
23 t3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
24 t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
25
tanf(float x)26 float tanf(float x)
27 {
28 double y;
29 uint32_t ix;
30 unsigned n, sign;
31
32 GET_FLOAT_WORD(ix, x);
33 sign = ix >> 31;
34 ix &= 0x7fffffff;
35
36 if (ix <= 0x3f490fda) { /* |x| ~<= pi/4 */
37 if (ix < 0x39800000) { /* |x| < 2**-12 */
38 /* raise inexact if x!=0 and underflow if subnormal */
39 FORCE_EVAL(ix < 0x00800000 ? x/0x1p120f : x+0x1p120f);
40 return x;
41 }
42 return __tandf(x, 0);
43 }
44 if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */
45 if (ix <= 0x4016cbe3) /* |x| ~<= 3pi/4 */
46 return __tandf((sign ? x+t1pio2 : x-t1pio2), 1);
47 else
48 return __tandf((sign ? x+t2pio2 : x-t2pio2), 0);
49 }
50 if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */
51 if (ix <= 0x40afeddf) /* |x| ~<= 7*pi/4 */
52 return __tandf((sign ? x+t3pio2 : x-t3pio2), 1);
53 else
54 return __tandf((sign ? x+t4pio2 : x-t4pio2), 0);
55 }
56
57 /* tan(Inf or NaN) is NaN */
58 if (ix >= 0x7f800000)
59 return x - x;
60
61 /* argument reduction */
62 n = __rem_pio2f(x, &y);
63 return __tandf(y, n&1);
64 }
65