Alex Crichton
a0a5bd85c9
These annotations fall into a few categories * Some simply aren't needed since functions will always be in the same CGU anyway and are already candidates for inlining. * Many are on massive functions which shouldn't be inlined across crates due to code size concerns. * Others aren't necessary since calls to this crate are rarely inlined anyway (since it's lowered through LLVM). If this crate is called directly and inlining is needed then LTO can always be turned on, otherwise this will benefit downstream consumers by avoiding re-codegen'ing so many functions.
86 lines
2.6 KiB
Rust
86 lines
2.6 KiB
Rust
// origin: FreeBSD /usr/src/lib/msun/src/s_sin.c */
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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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use super::{k_cos, k_sin, rem_pio2};
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// sin(x)
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// Return sine function of x.
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//
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// kernel function:
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// k_sin ... sine function on [-pi/4,pi/4]
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// k_cos ... cose function on [-pi/4,pi/4]
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// rem_pio2 ... argument reduction routine
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//
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// Method.
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// Let S,C and T denote the sin, cos and tan respectively on
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// [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
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// in [-pi/4 , +pi/4], and let n = k mod 4.
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// We have
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//
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// n sin(x) cos(x) tan(x)
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// ----------------------------------------------------------
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// 0 S C T
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// 1 C -S -1/T
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// 2 -S -C T
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// 3 -C S -1/T
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// ----------------------------------------------------------
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//
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// Special cases:
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// Let trig be any of sin, cos, or tan.
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// trig(+-INF) is NaN, with signals;
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// trig(NaN) is that NaN;
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//
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// Accuracy:
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// TRIG(x) returns trig(x) nearly rounded
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#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
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pub fn sin(x: f64) -> f64 {
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let x1p120 = f64::from_bits(0x4770000000000000); // 0x1p120f === 2 ^ 120
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/* High word of x. */
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let ix = (f64::to_bits(x) >> 32) as u32 & 0x7fffffff;
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/* |x| ~< pi/4 */
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if ix <= 0x3fe921fb {
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if ix < 0x3e500000 {
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/* |x| < 2**-26 */
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/* raise inexact if x != 0 and underflow if subnormal*/
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if ix < 0x00100000 {
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force_eval!(x / x1p120);
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} else {
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force_eval!(x + x1p120);
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}
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return x;
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}
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return k_sin(x, 0.0, 0);
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}
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/* sin(Inf or NaN) is NaN */
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if ix >= 0x7ff00000 {
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return x - x;
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}
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/* argument reduction needed */
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let (n, y0, y1) = rem_pio2(x);
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match n & 3 {
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0 => k_sin(y0, y1, 1),
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1 => k_cos(y0, y1),
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2 => -k_sin(y0, y1, 1),
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_ => -k_cos(y0, y1),
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}
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}
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#[test]
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fn test_near_pi() {
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let x = f64::from_bits(0x400921fb000FD5DD); // 3.141592026217707
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let sx = f64::from_bits(0x3ea50d15ced1a4a2); // 6.273720864039205e-7
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assert_eq!(sin(x), sx);
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}
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