97 lines
2.7 KiB
Rust
97 lines
2.7 KiB
Rust
/* 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 core::f64::consts::FRAC_PI_2;
|
|
|
|
use crate::soft_f64::SoftF64;
|
|
|
|
use super::{
|
|
helpers::{k_cosf, k_sinf, rem_pio2f},
|
|
SoftF32,
|
|
};
|
|
|
|
/* Small multiples of pi/2 rounded to double precision. */
|
|
const C1_PIO2: SoftF64 = SoftF64(1.).mul(SoftF64(FRAC_PI_2)); /* 0x3FF921FB, 0x54442D18 */
|
|
const C2_PIO2: SoftF64 = SoftF64(2.).mul(SoftF64(FRAC_PI_2)); /* 0x400921FB, 0x54442D18 */
|
|
const C3_PIO2: SoftF64 = SoftF64(3.).mul(SoftF64(FRAC_PI_2)); /* 0x4012D97C, 0x7F3321D2 */
|
|
const C4_PIO2: SoftF64 = SoftF64(4.).mul(SoftF64(FRAC_PI_2)); /* 0x401921FB, 0x54442D18 */
|
|
|
|
pub const fn cos(x: SoftF32) -> SoftF32 {
|
|
let x64 = SoftF64(x.0 as f64);
|
|
|
|
let x1p120 = SoftF32::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 */
|
|
let _ = x.add(x1p120);
|
|
return SoftF32(1.0);
|
|
}
|
|
return k_cosf(x64);
|
|
}
|
|
if ix <= 0x407b53d1 {
|
|
/* |x| ~<= 5*pi/4 */
|
|
if ix > 0x4016cbe3 {
|
|
/* |x| ~> 3*pi/4 */
|
|
return k_cosf(if sign {
|
|
x64.add(C2_PIO2)
|
|
} else {
|
|
x64.sub(C2_PIO2)
|
|
})
|
|
.neg();
|
|
} else if sign {
|
|
return k_sinf(x64.add(C1_PIO2));
|
|
} else {
|
|
return k_sinf(C1_PIO2.sub(x64));
|
|
}
|
|
}
|
|
if ix <= 0x40e231d5 {
|
|
/* |x| ~<= 9*pi/4 */
|
|
if ix > 0x40afeddf {
|
|
/* |x| ~> 7*pi/4 */
|
|
return k_cosf(if sign {
|
|
x64.add(C4_PIO2)
|
|
} else {
|
|
x64.sub(C4_PIO2)
|
|
});
|
|
} else if sign {
|
|
return k_sinf(x64.neg().sub(C3_PIO2));
|
|
} else {
|
|
return k_sinf(x64.sub(C3_PIO2));
|
|
}
|
|
}
|
|
|
|
/* cos(Inf or NaN) is NaN */
|
|
if ix >= 0x7f800000 {
|
|
return x.sub(x);
|
|
}
|
|
|
|
/* general argument reduction needed */
|
|
let (n, y) = rem_pio2f(x);
|
|
match n & 3 {
|
|
0 => k_cosf(y),
|
|
1 => k_sinf(y.neg()),
|
|
2 => k_cosf(y).neg(),
|
|
_ => k_sinf(y),
|
|
}
|
|
}
|