Jorge Aparicio
69 lines
1.8 KiB
Rust
69 lines
1.8 KiB
Rust
/* origin: FreeBSD /usr/src/lib/msun/src/e_asinf.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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*/
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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 super::fabsf::fabsf;
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use super::sqrt::sqrt;
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const PIO2: f64 = 1.570796326794896558e+00;
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/* coefficients for R(x^2) */
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const P_S0: f32 = 1.6666586697e-01;
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const P_S1: f32 = -4.2743422091e-02;
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const P_S2: f32 = -8.6563630030e-03;
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const Q_S1: f32 = -7.0662963390e-01;
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#[inline]
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fn r(z: f32) -> f32 {
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let p = z * (P_S0 + z * (P_S1 + z * P_S2));
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let q = 1. + z * Q_S1;
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p / q
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}
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#[inline]
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pub fn asinf(mut x: f32) -> f32 {
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let x1p_120 = f64::from_bits(0x3870000000000000); // 0x1p-120 === 2 ^ (-120)
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let hx = x.to_bits();
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let ix = hx & 0x7fffffff;
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if ix >= 0x3f800000 {
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/* |x| >= 1 */
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if ix == 0x3f800000 {
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/* |x| == 1 */
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return ((x as f64) * PIO2 + x1p_120) as f32; /* asin(+-1) = +-pi/2 with inexact */
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}
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return 0. / (x - x); /* asin(|x|>1) is NaN */
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}
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if ix < 0x3f000000 {
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/* |x| < 0.5 */
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/* if 0x1p-126 <= |x| < 0x1p-12, avoid raising underflow */
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if (ix < 0x39800000) && (ix >= 0x00800000) {
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return x;
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}
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return x + x * r(x * x);
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}
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/* 1 > |x| >= 0.5 */
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let z = (1. - fabsf(x)) * 0.5;
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let s = sqrt(z as f64);
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x = (PIO2 - 2. * (s + s * (r(z) as f64))) as f32;
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if (hx >> 31) != 0 {
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-x
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} else {
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x
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}
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}
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