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