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 super::{k_tanf, rem_pio2f};
18
19 use core::f64::consts::FRAC_PI_2;
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 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
tanf(x: f32) -> f3228 pub fn tanf(x: f32) -> f32 {
29 let x64 = x as f64;
30
31 let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120
32
33 let mut ix = x.to_bits();
34 let sign = (ix >> 31) != 0;
35 ix &= 0x7fffffff;
36
37 if ix <= 0x3f490fda {
38 /* |x| ~<= pi/4 */
39 if ix < 0x39800000 {
40 /* |x| < 2**-12 */
41 /* raise inexact if x!=0 and underflow if subnormal */
42 force_eval!(if ix < 0x00800000 {
43 x / x1p120
44 } else {
45 x + x1p120
46 });
47 return x;
48 }
49 return k_tanf(x64, false);
50 }
51 if ix <= 0x407b53d1 {
52 /* |x| ~<= 5*pi/4 */
53 if ix <= 0x4016cbe3 {
54 /* |x| ~<= 3pi/4 */
55 return k_tanf(if sign { x64 + T1_PIO2 } else { x64 - T1_PIO2 }, true);
56 } else {
57 return k_tanf(if sign { x64 + T2_PIO2 } else { x64 - T2_PIO2 }, false);
58 }
59 }
60 if ix <= 0x40e231d5 {
61 /* |x| ~<= 9*pi/4 */
62 if ix <= 0x40afeddf {
63 /* |x| ~<= 7*pi/4 */
64 return k_tanf(if sign { x64 + T3_PIO2 } else { x64 - T3_PIO2 }, true);
65 } else {
66 return k_tanf(if sign { x64 + T4_PIO2 } else { x64 - T4_PIO2 }, false);
67 }
68 }
69
70 /* tan(Inf or NaN) is NaN */
71 if ix >= 0x7f800000 {
72 return x - x;
73 }
74
75 /* argument reduction */
76 let (n, y) = rem_pio2f(x);
77 k_tanf(y, n & 1 != 0)
78 }
79