1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
|
use rustc_data_structures::graph::{
self, DirectedGraph, WithNumNodes, WithStartNode, WithSuccessors,
};
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_data_structures::sync::OnceCell;
use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
/// Helper type to cache the result of `graph::is_cyclic`.
#[derive(Clone, Debug)]
pub(super) struct GraphIsCyclicCache {
cache: OnceCell<bool>,
}
impl GraphIsCyclicCache {
#[inline]
pub(super) fn new() -> Self {
GraphIsCyclicCache { cache: OnceCell::new() }
}
pub(super) fn is_cyclic<G>(&self, graph: &G) -> bool
where
G: ?Sized + DirectedGraph + WithStartNode + WithSuccessors + WithNumNodes,
{
*self.cache.get_or_init(|| graph::is_cyclic(graph))
}
/// Invalidates the cache.
#[inline]
pub(super) fn invalidate(&mut self) {
// Invalidating the cache requires mutating the MIR, which in turn requires a unique
// reference (`&mut`) to the `mir::Body`. Because of this, we can assume that all
// callers of `invalidate` have a unique reference to the MIR and thus to the
// cache. This means we never need to do synchronization when `invalidate` is called,
// we can simply reinitialize the `OnceCell`.
self.cache = OnceCell::new();
}
}
impl<S: Encoder> Encodable<S> for GraphIsCyclicCache {
#[inline]
fn encode(&self, s: &mut S) {
Encodable::encode(&(), s);
}
}
impl<D: Decoder> Decodable<D> for GraphIsCyclicCache {
#[inline]
fn decode(d: &mut D) -> Self {
let () = Decodable::decode(d);
Self::new()
}
}
impl<CTX> HashStable<CTX> for GraphIsCyclicCache {
#[inline]
fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {
// do nothing
}
}
TrivialTypeTraversalAndLiftImpls! {
GraphIsCyclicCache,
}
|
