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
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
|
//! Lazily compute the reverse control-flow graph for the MIR.
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_data_structures::sync::OnceCell;
use rustc_index::vec::IndexVec;
use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
use smallvec::SmallVec;
use crate::mir::{BasicBlock, BasicBlockData};
// Typically 95%+ of basic blocks have 4 or fewer predecessors.
pub type Predecessors = IndexVec<BasicBlock, SmallVec<[BasicBlock; 4]>>;
#[derive(Clone, Debug)]
pub(super) struct PredecessorCache {
cache: OnceCell<Predecessors>,
}
impl PredecessorCache {
#[inline]
pub(super) fn new() -> Self {
PredecessorCache { cache: OnceCell::new() }
}
/// Invalidates the predecessor cache.
#[inline]
pub(super) fn invalidate(&mut self) {
// Invalidating the predecessor 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 predecessor
// cache. This means we never need to do synchronization when `invalidate` is called, we can
// simply reinitialize the `OnceCell`.
self.cache = OnceCell::new();
}
/// Returns the predecessor graph for this MIR.
#[inline]
pub(super) fn compute(
&self,
basic_blocks: &IndexVec<BasicBlock, BasicBlockData<'_>>,
) -> &Predecessors {
self.cache.get_or_init(|| {
let mut preds = IndexVec::from_elem(SmallVec::new(), basic_blocks);
for (bb, data) in basic_blocks.iter_enumerated() {
if let Some(term) = &data.terminator {
for succ in term.successors() {
preds[succ].push(bb);
}
}
}
preds
})
}
}
impl<S: Encoder> Encodable<S> for PredecessorCache {
#[inline]
fn encode(&self, _s: &mut S) {}
}
impl<D: Decoder> Decodable<D> for PredecessorCache {
#[inline]
fn decode(_: &mut D) -> Self {
Self::new()
}
}
impl<CTX> HashStable<CTX> for PredecessorCache {
#[inline]
fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {
// do nothing
}
}
TrivialTypeTraversalAndLiftImpls! {
PredecessorCache,
}
|
