diff options
Diffstat (limited to 'vendor/compiler_builtins/libm/src/math/cos.rs')
-rw-r--r-- | vendor/compiler_builtins/libm/src/math/cos.rs | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/vendor/compiler_builtins/libm/src/math/cos.rs b/vendor/compiler_builtins/libm/src/math/cos.rs new file mode 100644 index 000000000..db8bc4989 --- /dev/null +++ b/vendor/compiler_builtins/libm/src/math/cos.rs @@ -0,0 +1,73 @@ +// origin: FreeBSD /usr/src/lib/msun/src/s_cos.c */ +// +// ==================================================== +// 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_cos, k_sin, rem_pio2}; + +// cos(x) +// Return cosine function of x. +// +// kernel function: +// k_sin ... sine function on [-pi/4,pi/4] +// k_cos ... cosine function on [-pi/4,pi/4] +// rem_pio2 ... argument reduction routine +// +// Method. +// Let S,C and T denote the sin, cos and tan respectively on +// [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 +// in [-pi/4 , +pi/4], and let n = k mod 4. +// We have +// +// n sin(x) cos(x) tan(x) +// ---------------------------------------------------------- +// 0 S C T +// 1 C -S -1/T +// 2 -S -C T +// 3 -C S -1/T +// ---------------------------------------------------------- +// +// Special cases: +// Let trig be any of sin, cos, or tan. +// trig(+-INF) is NaN, with signals; +// trig(NaN) is that NaN; +// +// Accuracy: +// TRIG(x) returns trig(x) nearly rounded +// +#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] +pub fn cos(x: f64) -> f64 { + let ix = (f64::to_bits(x) >> 32) as u32 & 0x7fffffff; + + /* |x| ~< pi/4 */ + if ix <= 0x3fe921fb { + if ix < 0x3e46a09e { + /* if x < 2**-27 * sqrt(2) */ + /* raise inexact if x != 0 */ + if x as i32 == 0 { + return 1.0; + } + } + return k_cos(x, 0.0); + } + + /* cos(Inf or NaN) is NaN */ + if ix >= 0x7ff00000 { + return x - x; + } + + /* argument reduction needed */ + let (n, y0, y1) = rem_pio2(x); + match n & 3 { + 0 => k_cos(y0, y1), + 1 => -k_sin(y0, y1, 1), + 2 => -k_cos(y0, y1), + _ => k_sin(y0, y1, 1), + } +} |