13c744f30d
This change moves: 1. `libcoretest` into `libcore/tests` 2. `libcollectionstest` into `libcollections/tests` This is a follow-up to #39561.
93 lines
2.7 KiB
Rust
93 lines
2.7 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Extended precision "soft float", for internal use only.
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// This module is only for dec2flt and flt2dec, and only public because of coretests.
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// It is not intended to ever be stabilized.
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#![doc(hidden)]
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#![unstable(feature = "core_private_diy_float",
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reason = "internal routines only exposed for testing",
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issue = "0")]
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/// A custom 64-bit floating point type, representing `f * 2^e`.
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#[derive(Copy, Clone, Debug)]
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#[doc(hidden)]
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pub struct Fp {
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/// The integer mantissa.
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pub f: u64,
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/// The exponent in base 2.
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pub e: i16,
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}
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impl Fp {
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/// Returns a correctly rounded product of itself and `other`.
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pub fn mul(&self, other: &Fp) -> Fp {
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const MASK: u64 = 0xffffffff;
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let a = self.f >> 32;
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let b = self.f & MASK;
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let c = other.f >> 32;
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let d = other.f & MASK;
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let ac = a * c;
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let bc = b * c;
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let ad = a * d;
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let bd = b * d;
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let tmp = (bd >> 32) + (ad & MASK) + (bc & MASK) + (1 << 31) /* round */;
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let f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);
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let e = self.e + other.e + 64;
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Fp { f: f, e: e }
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}
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/// Normalizes itself so that the resulting mantissa is at least `2^63`.
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pub fn normalize(&self) -> Fp {
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let mut f = self.f;
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let mut e = self.e;
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if f >> (64 - 32) == 0 {
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f <<= 32;
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e -= 32;
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}
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if f >> (64 - 16) == 0 {
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f <<= 16;
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e -= 16;
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}
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if f >> (64 - 8) == 0 {
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f <<= 8;
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e -= 8;
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}
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if f >> (64 - 4) == 0 {
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f <<= 4;
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e -= 4;
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}
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if f >> (64 - 2) == 0 {
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f <<= 2;
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e -= 2;
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}
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if f >> (64 - 1) == 0 {
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f <<= 1;
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e -= 1;
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}
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debug_assert!(f >= (1 >> 63));
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Fp { f: f, e: e }
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}
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/// Normalizes itself to have the shared exponent.
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/// It can only decrease the exponent (and thus increase the mantissa).
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pub fn normalize_to(&self, e: i16) -> Fp {
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let edelta = self.e - e;
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assert!(edelta >= 0);
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let edelta = edelta as usize;
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assert_eq!(self.f << edelta >> edelta, self.f);
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Fp {
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f: self.f << edelta,
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e: e,
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}
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}
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}
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