libm/math/
sinf.rs

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 super::{k_cosf, k_sinf, rem_pio2f};
18
19use core::f64::consts::FRAC_PI_2;
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#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
28pub fn sinf(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_sinf(x64);
50    }
51    if ix <= 0x407b53d1 {
52        /* |x| ~<= 5*pi/4 */
53        if ix <= 0x4016cbe3 {
54            /* |x| ~<= 3pi/4 */
55            if sign {
56                return -k_cosf(x64 + S1_PIO2);
57            } else {
58                return k_cosf(x64 - S1_PIO2);
59            }
60        }
61        return k_sinf(if sign {
62            -(x64 + S2_PIO2)
63        } else {
64            -(x64 - S2_PIO2)
65        });
66    }
67    if ix <= 0x40e231d5 {
68        /* |x| ~<= 9*pi/4 */
69        if ix <= 0x40afeddf {
70            /* |x| ~<= 7*pi/4 */
71            if sign {
72                return k_cosf(x64 + S3_PIO2);
73            } else {
74                return -k_cosf(x64 - S3_PIO2);
75            }
76        }
77        return k_sinf(if sign { x64 + S4_PIO2 } else { x64 - S4_PIO2 });
78    }
79
80    /* sin(Inf or NaN) is NaN */
81    if ix >= 0x7f800000 {
82        return x - x;
83    }
84
85    /* general argument reduction needed */
86    let (n, y) = rem_pio2f(x);
87    match n & 3 {
88        0 => k_sinf(y),
89        1 => k_cosf(y),
90        2 => k_sinf(-y),
91        _ => -k_cosf(y),
92    }
93}