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 use core::f64::consts::FRAC_PI_2;
18
19 use super::{k_tanf, rem_pio2f};
20
21 /* Small multiples of pi/2 rounded to double precision. */
22 const T1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */
23 const T2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */
24 const T3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */
25 const T4_PIO2: f64 = 4. * FRAC_PI_2; /* 0x401921FB, 0x54442D18 */
26
27 /// The tangent of `x` (f32).
28 ///
29 /// `x` is specified in radians.
30 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
tanf(x: f32) -> f3231 pub fn tanf(x: f32) -> f32 {
32 let x64 = x as f64;
33
34 let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120
35
36 let mut ix = x.to_bits();
37 let sign = (ix >> 31) != 0;
38 ix &= 0x7fffffff;
39
40 if ix <= 0x3f490fda {
41 /* |x| ~<= pi/4 */
42 if ix < 0x39800000 {
43 /* |x| < 2**-12 */
44 /* raise inexact if x!=0 and underflow if subnormal */
45 force_eval!(if ix < 0x00800000 { x / x1p120 } else { x + x1p120 });
46 return x;
47 }
48 return k_tanf(x64, false);
49 }
50 if ix <= 0x407b53d1 {
51 /* |x| ~<= 5*pi/4 */
52 if ix <= 0x4016cbe3 {
53 /* |x| ~<= 3pi/4 */
54 return k_tanf(if sign { x64 + T1_PIO2 } else { x64 - T1_PIO2 }, true);
55 } else {
56 return k_tanf(if sign { x64 + T2_PIO2 } else { x64 - T2_PIO2 }, false);
57 }
58 }
59 if ix <= 0x40e231d5 {
60 /* |x| ~<= 9*pi/4 */
61 if ix <= 0x40afeddf {
62 /* |x| ~<= 7*pi/4 */
63 return k_tanf(if sign { x64 + T3_PIO2 } else { x64 - T3_PIO2 }, true);
64 } else {
65 return k_tanf(if sign { x64 + T4_PIO2 } else { x64 - T4_PIO2 }, false);
66 }
67 }
68
69 /* tan(Inf or NaN) is NaN */
70 if ix >= 0x7f800000 {
71 return x - x;
72 }
73
74 /* argument reduction */
75 let (n, y) = rem_pio2f(x);
76 k_tanf(y, n & 1 != 0)
77 }
78