1 /* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.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_cosf, k_sinf, rem_pio2f};
18
19 use core::f64::consts::FRAC_PI_2;
20
21 /* Small multiples of pi/2 rounded to double precision. */
22 const C1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */
23 const C2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */
24 const C3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */
25 const C4_PIO2: f64 = 4. * FRAC_PI_2; /* 0x401921FB, 0x54442D18 */
26
27 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
cosf(x: f32) -> f3228 pub fn cosf(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 */
42 force_eval!(x + x1p120);
43 return 1.;
44 }
45 return k_cosf(x64);
46 }
47 if ix <= 0x407b53d1 {
48 /* |x| ~<= 5*pi/4 */
49 if ix > 0x4016cbe3 {
50 /* |x| ~> 3*pi/4 */
51 return -k_cosf(if sign { x64 + C2_PIO2 } else { x64 - C2_PIO2 });
52 } else if sign {
53 return k_sinf(x64 + C1_PIO2);
54 } else {
55 return k_sinf(C1_PIO2 - x64);
56 }
57 }
58 if ix <= 0x40e231d5 {
59 /* |x| ~<= 9*pi/4 */
60 if ix > 0x40afeddf {
61 /* |x| ~> 7*pi/4 */
62 return k_cosf(if sign { x64 + C4_PIO2 } else { x64 - C4_PIO2 });
63 } else if sign {
64 return k_sinf(-x64 - C3_PIO2);
65 } else {
66 return k_sinf(x64 - C3_PIO2);
67 }
68 }
69
70 /* cos(Inf or NaN) is NaN */
71 if ix >= 0x7f800000 {
72 return x - x;
73 }
74
75 /* general argument reduction needed */
76 let (n, y) = rem_pio2f(x);
77 match n & 3 {
78 0 => k_cosf(y),
79 1 => k_sinf(-y),
80 2 => -k_cosf(y),
81 _ => k_sinf(y),
82 }
83 }
84