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 t1pio2 = 1 * M_PI_2, /* 0x3FF921FB, 0x54442D18 */
21    t2pio2 = 2 * M_PI_2,                 /* 0x400921FB, 0x54442D18 */
22    t3pio2 = 3 * M_PI_2,                 /* 0x4012D97C, 0x7F3321D2 */
23    t4pio2 = 4 * M_PI_2;                 /* 0x401921FB, 0x54442D18 */
24
25float tanf(float x) {
26    double y;
27    uint32_t ix;
28    unsigned n, sign;
29
30    GET_FLOAT_WORD(ix, x);
31    sign = ix >> 31;
32    ix &= 0x7fffffff;
33
34    if (ix <= 0x3f490fda) {    /* |x| ~<= pi/4 */
35        if (ix < 0x39800000) { /* |x| < 2**-12 */
36            /* raise inexact if x!=0 and underflow if subnormal */
37            FORCE_EVAL(ix < 0x00800000 ? x / 0x1p120f : x + 0x1p120f);
38            return x;
39        }
40        return __tandf(x, 0);
41    }
42    if (ix <= 0x407b53d1) {   /* |x| ~<= 5*pi/4 */
43        if (ix <= 0x4016cbe3) /* |x| ~<= 3pi/4 */
44            return __tandf((sign ? x + t1pio2 : x - t1pio2), 1);
45        else
46            return __tandf((sign ? x + t2pio2 : x - t2pio2), 0);
47    }
48    if (ix <= 0x40e231d5) {   /* |x| ~<= 9*pi/4 */
49        if (ix <= 0x40afeddf) /* |x| ~<= 7*pi/4 */
50            return __tandf((sign ? x + t3pio2 : x - t3pio2), 1);
51        else
52            return __tandf((sign ? x + t4pio2 : x - t4pio2), 0);
53    }
54
55    /* tan(Inf or NaN) is NaN */
56    if (ix >= 0x7f800000)
57        return x - x;
58
59    /* argument reduction */
60    n = __rem_pio2f(x, &y);
61    return __tandf(y, n & 1);
62}
63