| /* origin: FreeBSD /usr/src/lib/msun/src/e_rem_pio2f.c */ |
| /* |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| * Debugged and optimized by Bruce D. Evans. |
| */ |
| /* |
| * ==================================================== |
| * 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::rem_pio2_large; |
| |
| use core::f64; |
| |
| const TOINT: f64 = 1.5 / f64::EPSILON; |
| |
| /// 53 bits of 2/pi |
| const INV_PIO2: f64 = 6.36619772367581382433e-01; /* 0x3FE45F30, 0x6DC9C883 */ |
| /// first 25 bits of pi/2 |
| const PIO2_1: f64 = 1.57079631090164184570e+00; /* 0x3FF921FB, 0x50000000 */ |
| /// pi/2 - pio2_1 |
| const PIO2_1T: f64 = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */ |
| |
| /// Return the remainder of x rem pi/2 in *y |
| /// |
| /// use double precision for everything except passing x |
| /// use __rem_pio2_large() for large x |
| #[inline] |
| #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| pub(crate) fn rem_pio2f(x: f32) -> (i32, f64) { |
| let x64 = x as f64; |
| |
| let mut tx: [f64; 1] = [0.]; |
| let mut ty: [f64; 1] = [0.]; |
| |
| let ix = x.to_bits() & 0x7fffffff; |
| /* 25+53 bit pi is good enough for medium size */ |
| if ix < 0x4dc90fdb { |
| /* |x| ~< 2^28*(pi/2), medium size */ |
| /* Use a specialized rint() to get fn. Assume round-to-nearest. */ |
| let f_n = x64 * INV_PIO2 + TOINT - TOINT; |
| return (f_n as i32, x64 - f_n * PIO2_1 - f_n * PIO2_1T); |
| } |
| if ix >= 0x7f800000 { |
| /* x is inf or NaN */ |
| return (0, x64 - x64); |
| } |
| /* scale x into [2^23, 2^24-1] */ |
| let sign = (x.to_bits() >> 31) != 0; |
| let e0 = ((ix >> 23) - (0x7f + 23)) as i32; /* e0 = ilogb(|x|)-23, positive */ |
| tx[0] = f32::from_bits(ix - (e0 << 23) as u32) as f64; |
| let n = rem_pio2_large(&tx, &mut ty, e0, 0); |
| if sign { |
| return (-n, -ty[0]); |
| } |
| (n, ty[0]) |
| } |
