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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
commit698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch)
tree173a775858bd501c378080a10dca74132f05bc50 /vendor/compiler_builtins/libm/src/math/k_sin.rs
parentInitial commit. (diff)
downloadrustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz
rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'vendor/compiler_builtins/libm/src/math/k_sin.rs')
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1 files changed, 57 insertions, 0 deletions
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+// origin: FreeBSD /usr/src/lib/msun/src/k_sin.c
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunSoft, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+
+const S1: f64 = -1.66666666666666324348e-01; /* 0xBFC55555, 0x55555549 */
+const S2: f64 = 8.33333333332248946124e-03; /* 0x3F811111, 0x1110F8A6 */
+const S3: f64 = -1.98412698298579493134e-04; /* 0xBF2A01A0, 0x19C161D5 */
+const S4: f64 = 2.75573137070700676789e-06; /* 0x3EC71DE3, 0x57B1FE7D */
+const S5: f64 = -2.50507602534068634195e-08; /* 0xBE5AE5E6, 0x8A2B9CEB */
+const S6: f64 = 1.58969099521155010221e-10; /* 0x3DE5D93A, 0x5ACFD57C */
+
+// kernel sin function on ~[-pi/4, pi/4] (except on -0), pi/4 ~ 0.7854
+// Input x is assumed to be bounded by ~pi/4 in magnitude.
+// Input y is the tail of x.
+// Input iy indicates whether y is 0. (if iy=0, y assume to be 0).
+//
+// Algorithm
+// 1. Since sin(-x) = -sin(x), we need only to consider positive x.
+// 2. Callers must return sin(-0) = -0 without calling here since our
+// odd polynomial is not evaluated in a way that preserves -0.
+// Callers may do the optimization sin(x) ~ x for tiny x.
+// 3. sin(x) is approximated by a polynomial of degree 13 on
+// [0,pi/4]
+// 3 13
+// sin(x) ~ x + S1*x + ... + S6*x
+// where
+//
+// |sin(x) 2 4 6 8 10 12 | -58
+// |----- - (1+S1*x +S2*x +S3*x +S4*x +S5*x +S6*x )| <= 2
+// | x |
+//
+// 4. sin(x+y) = sin(x) + sin'(x')*y
+// ~ sin(x) + (1-x*x/2)*y
+// For better accuracy, let
+// 3 2 2 2 2
+// r = x *(S2+x *(S3+x *(S4+x *(S5+x *S6))))
+// then 3 2
+// sin(x) = x + (S1*x + (x *(r-y/2)+y))
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub(crate) fn k_sin(x: f64, y: f64, iy: i32) -> f64 {
+ let z = x * x;
+ let w = z * z;
+ let r = S2 + z * (S3 + z * S4) + z * w * (S5 + z * S6);
+ let v = z * x;
+ if iy == 0 {
+ x + v * (S1 + z * r)
+ } else {
+ x - ((z * (0.5 * y - v * r) - y) - v * S1)
+ }
+}