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/* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.c */
/*
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
* Optimized by Bruce D. Evans.
*/
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
use super::{k_cosf, k_sinf, rem_pio2f};
use core::f64::consts::FRAC_PI_2;
/* Small multiples of pi/2 rounded to double precision. */
const C1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */
const C2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */
const C3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */
const C4_PIO2: f64 = 4. * FRAC_PI_2; /* 0x401921FB, 0x54442D18 */
#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn cosf(x: f32) -> f32 {
let x64 = x as f64;
let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120
let mut ix = x.to_bits();
let sign = (ix >> 31) != 0;
ix &= 0x7fffffff;
if ix <= 0x3f490fda {
/* |x| ~<= pi/4 */
if ix < 0x39800000 {
/* |x| < 2**-12 */
/* raise inexact if x != 0 */
force_eval!(x + x1p120);
return 1.;
}
return k_cosf(x64);
}
if ix <= 0x407b53d1 {
/* |x| ~<= 5*pi/4 */
if ix > 0x4016cbe3 {
/* |x| ~> 3*pi/4 */
return -k_cosf(if sign { x64 + C2_PIO2 } else { x64 - C2_PIO2 });
} else if sign {
return k_sinf(x64 + C1_PIO2);
} else {
return k_sinf(C1_PIO2 - x64);
}
}
if ix <= 0x40e231d5 {
/* |x| ~<= 9*pi/4 */
if ix > 0x40afeddf {
/* |x| ~> 7*pi/4 */
return k_cosf(if sign { x64 + C4_PIO2 } else { x64 - C4_PIO2 });
} else if sign {
return k_sinf(-x64 - C3_PIO2);
} else {
return k_sinf(x64 - C3_PIO2);
}
}
/* cos(Inf or NaN) is NaN */
if ix >= 0x7f800000 {
return x - x;
}
/* general argument reduction needed */
let (n, y) = rem_pio2f(x);
match n & 3 {
0 => k_cosf(y),
1 => k_sinf(-y),
2 => -k_cosf(y),
_ => k_sinf(y),
}
}