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. */
20static const double
21t1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
22t2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
23t3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
24t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
25
26float 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