/rust/registry/src/index.crates.io-1949cf8c6b5b557f/libm-0.2.15/src/math/sinf.rs
Line | Count | Source |
1 | | /* origin: FreeBSD /usr/src/lib/msun/src/s_sinf.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_cosf, k_sinf, rem_pio2f}; |
20 | | |
21 | | /* Small multiples of pi/2 rounded to double precision. */ |
22 | | const S1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */ |
23 | | const S2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */ |
24 | | const S3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */ |
25 | | const S4_PIO2: f64 = 4. * FRAC_PI_2; /* 0x401921FB, 0x54442D18 */ |
26 | | |
27 | | /// The sine of `x` (f32). |
28 | | /// |
29 | | /// `x` is specified in radians. |
30 | | #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
31 | 0 | pub fn sinf(x: f32) -> f32 { |
32 | 0 | let x64 = x as f64; |
33 | | |
34 | 0 | let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120 |
35 | | |
36 | 0 | let mut ix = x.to_bits(); |
37 | 0 | let sign = (ix >> 31) != 0; |
38 | 0 | ix &= 0x7fffffff; |
39 | | |
40 | 0 | if ix <= 0x3f490fda { |
41 | | /* |x| ~<= pi/4 */ |
42 | 0 | if ix < 0x39800000 { |
43 | | /* |x| < 2**-12 */ |
44 | | /* raise inexact if x!=0 and underflow if subnormal */ |
45 | 0 | force_eval!(if ix < 0x00800000 { |
46 | 0 | x / x1p120 |
47 | | } else { |
48 | 0 | x + x1p120 |
49 | | }); |
50 | 0 | return x; |
51 | 0 | } |
52 | 0 | return k_sinf(x64); |
53 | 0 | } |
54 | 0 | if ix <= 0x407b53d1 { |
55 | | /* |x| ~<= 5*pi/4 */ |
56 | 0 | if ix <= 0x4016cbe3 { |
57 | | /* |x| ~<= 3pi/4 */ |
58 | 0 | if sign { |
59 | 0 | return -k_cosf(x64 + S1_PIO2); |
60 | | } else { |
61 | 0 | return k_cosf(x64 - S1_PIO2); |
62 | | } |
63 | 0 | } |
64 | 0 | return k_sinf(if sign { |
65 | 0 | -(x64 + S2_PIO2) |
66 | | } else { |
67 | 0 | -(x64 - S2_PIO2) |
68 | | }); |
69 | 0 | } |
70 | 0 | if ix <= 0x40e231d5 { |
71 | | /* |x| ~<= 9*pi/4 */ |
72 | 0 | if ix <= 0x40afeddf { |
73 | | /* |x| ~<= 7*pi/4 */ |
74 | 0 | if sign { |
75 | 0 | return k_cosf(x64 + S3_PIO2); |
76 | | } else { |
77 | 0 | return -k_cosf(x64 - S3_PIO2); |
78 | | } |
79 | 0 | } |
80 | 0 | return k_sinf(if sign { x64 + S4_PIO2 } else { x64 - S4_PIO2 }); |
81 | 0 | } |
82 | | |
83 | | /* sin(Inf or NaN) is NaN */ |
84 | 0 | if ix >= 0x7f800000 { |
85 | 0 | return x - x; |
86 | 0 | } |
87 | | |
88 | | /* general argument reduction needed */ |
89 | 0 | let (n, y) = rem_pio2f(x); |
90 | 0 | match n & 3 { |
91 | 0 | 0 => k_sinf(y), |
92 | 0 | 1 => k_cosf(y), |
93 | 0 | 2 => k_sinf(-y), |
94 | 0 | _ => -k_cosf(y), |
95 | | } |
96 | 0 | } |