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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /vendor/compiler_builtins/libm/src/math/k_tan.rs | |
parent | Initial commit. (diff) | |
download | rustc-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_tan.rs')
-rw-r--r-- | vendor/compiler_builtins/libm/src/math/k_tan.rs | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/vendor/compiler_builtins/libm/src/math/k_tan.rs b/vendor/compiler_builtins/libm/src/math/k_tan.rs new file mode 100644 index 000000000..d177010bb --- /dev/null +++ b/vendor/compiler_builtins/libm/src/math/k_tan.rs @@ -0,0 +1,105 @@ +// origin: FreeBSD /usr/src/lib/msun/src/k_tan.c */ +// +// ==================================================== +// Copyright 2004 Sun Microsystems, Inc. All Rights Reserved. +// +// Permission to use, copy, modify, and distribute this +// software is freely granted, provided that this notice +// is preserved. +// ==================================================== + +// kernel tan 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 odd indicates whether tan (if odd = 0) or -1/tan (if odd = 1) is returned. +// +// Algorithm +// 1. Since tan(-x) = -tan(x), we need only to consider positive x. +// 2. Callers must return tan(-0) = -0 without calling here since our +// odd polynomial is not evaluated in a way that preserves -0. +// Callers may do the optimization tan(x) ~ x for tiny x. +// 3. tan(x) is approximated by a odd polynomial of degree 27 on +// [0,0.67434] +// 3 27 +// tan(x) ~ x + T1*x + ... + T13*x +// where +// +// |tan(x) 2 4 26 | -59.2 +// |----- - (1+T1*x +T2*x +.... +T13*x )| <= 2 +// | x | +// +// Note: tan(x+y) = tan(x) + tan'(x)*y +// ~ tan(x) + (1+x*x)*y +// Therefore, for better accuracy in computing tan(x+y), let +// 3 2 2 2 2 +// r = x *(T2+x *(T3+x *(...+x *(T12+x *T13)))) +// then +// 3 2 +// tan(x+y) = x + (T1*x + (x *(r+y)+y)) +// +// 4. For x in [0.67434,pi/4], let y = pi/4 - x, then +// tan(x) = tan(pi/4-y) = (1-tan(y))/(1+tan(y)) +// = 1 - 2*(tan(y) - (tan(y)^2)/(1+tan(y))) +static T: [f64; 13] = [ + 3.33333333333334091986e-01, /* 3FD55555, 55555563 */ + 1.33333333333201242699e-01, /* 3FC11111, 1110FE7A */ + 5.39682539762260521377e-02, /* 3FABA1BA, 1BB341FE */ + 2.18694882948595424599e-02, /* 3F9664F4, 8406D637 */ + 8.86323982359930005737e-03, /* 3F8226E3, E96E8493 */ + 3.59207910759131235356e-03, /* 3F6D6D22, C9560328 */ + 1.45620945432529025516e-03, /* 3F57DBC8, FEE08315 */ + 5.88041240820264096874e-04, /* 3F4344D8, F2F26501 */ + 2.46463134818469906812e-04, /* 3F3026F7, 1A8D1068 */ + 7.81794442939557092300e-05, /* 3F147E88, A03792A6 */ + 7.14072491382608190305e-05, /* 3F12B80F, 32F0A7E9 */ + -1.85586374855275456654e-05, /* BEF375CB, DB605373 */ + 2.59073051863633712884e-05, /* 3EFB2A70, 74BF7AD4 */ +]; +const PIO4: f64 = 7.85398163397448278999e-01; /* 3FE921FB, 54442D18 */ +const PIO4_LO: f64 = 3.06161699786838301793e-17; /* 3C81A626, 33145C07 */ + +#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] +pub(crate) fn k_tan(mut x: f64, mut y: f64, odd: i32) -> f64 { + let hx = (f64::to_bits(x) >> 32) as u32; + let big = (hx & 0x7fffffff) >= 0x3FE59428; /* |x| >= 0.6744 */ + if big { + let sign = hx >> 31; + if sign != 0 { + x = -x; + y = -y; + } + x = (PIO4 - x) + (PIO4_LO - y); + y = 0.0; + } + let z = x * x; + let w = z * z; + /* + * Break x^5*(T[1]+x^2*T[2]+...) into + * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) + + * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12])) + */ + let r = T[1] + w * (T[3] + w * (T[5] + w * (T[7] + w * (T[9] + w * T[11])))); + let v = z * (T[2] + w * (T[4] + w * (T[6] + w * (T[8] + w * (T[10] + w * T[12]))))); + let s = z * x; + let r = y + z * (s * (r + v) + y) + s * T[0]; + let w = x + r; + if big { + let sign = hx >> 31; + let s = 1.0 - 2.0 * odd as f64; + let v = s - 2.0 * (x + (r - w * w / (w + s))); + return if sign != 0 { -v } else { v }; + } + if odd == 0 { + return w; + } + /* -1.0/(x+r) has up to 2ulp error, so compute it accurately */ + let w0 = zero_low_word(w); + let v = r - (w0 - x); /* w0+v = r+x */ + let a = -1.0 / w; + let a0 = zero_low_word(a); + a0 + a * (1.0 + a0 * w0 + a0 * v) +} + +fn zero_low_word(x: f64) -> f64 { + f64::from_bits(f64::to_bits(x) & 0xFFFF_FFFF_0000_0000) +} |