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
17use core::f64::consts::FRAC_PI_2;
18
19use super::{k_cosf, k_sinf, rem_pio2f};
20
21/* Small multiples of pi/2 rounded to double precision. */
22const S1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */
23const S2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */
24const S3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */
25const 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)]
31pub fn sinf(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 {
46 x / x1p120
47 } else {
48 x + x1p120
49 });
50 return x;
51 }
52 return k_sinf(x64);
53 }
54 if ix <= 0x407b53d1 {
55 /* |x| ~<= 5*pi/4 */
56 if ix <= 0x4016cbe3 {
57 /* |x| ~<= 3pi/4 */
58 if sign {
59 return -k_cosf(x64 + S1_PIO2);
60 } else {
61 return k_cosf(x64 - S1_PIO2);
62 }
63 }
64 return k_sinf(if sign {
65 -(x64 + S2_PIO2)
66 } else {
67 -(x64 - S2_PIO2)
68 });
69 }
70 if ix <= 0x40e231d5 {
71 /* |x| ~<= 9*pi/4 */
72 if ix <= 0x40afeddf {
73 /* |x| ~<= 7*pi/4 */
74 if sign {
75 return k_cosf(x64 + S3_PIO2);
76 } else {
77 return -k_cosf(x64 - S3_PIO2);
78 }
79 }
80 return k_sinf(if sign { x64 + S4_PIO2 } else { x64 - S4_PIO2 });
81 }
82
83 /* sin(Inf or NaN) is NaN */
84 if ix >= 0x7f800000 {
85 return x - x;
86 }
87
88 /* general argument reduction needed */
89 let (n, y) = rem_pio2f(x);
90 match n & 3 {
91 0 => k_sinf(y),
92 1 => k_cosf(y),
93 2 => k_sinf(-y),
94 _ => -k_cosf(y),
95 }
96}
97