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use rustc_index::vec::IndexVec;
use rustc_data_structures::sync::{RwLock, MappedReadGuard, ReadGuard};
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_serialize::{Encodable, Encoder, Decodable, Decoder};
use crate::ich::StableHashingContext;
use crate::mir::{Body, BasicBlock};
#[derive(Clone, Debug)]
pub struct Cache {
predecessors: RwLock<Option<IndexVec<BasicBlock, Vec<BasicBlock>>>>
}
impl rustc_serialize::Encodable for Cache {
fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
Encodable::encode(&(), s)
}
}
impl rustc_serialize::Decodable for Cache {
fn decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
Decodable::decode(d).map(|_v: ()| Self::new())
}
}
impl<'a> HashStable<StableHashingContext<'a>> for Cache {
fn hash_stable(&self, _: &mut StableHashingContext<'a>, _: &mut StableHasher) {
// Do nothing.
}
}
impl Cache {
pub fn new() -> Self {
Cache {
predecessors: RwLock::new(None)
}
}
pub fn invalidate(&self) {
// FIXME: consider being more fine-grained
*self.predecessors.borrow_mut() = None;
}
pub fn predecessors(
&self,
body: &Body<'_>
) -> MappedReadGuard<'_, IndexVec<BasicBlock, Vec<BasicBlock>>> {
if self.predecessors.borrow().is_none() {
*self.predecessors.borrow_mut() = Some(calculate_predecessors(body));
}
ReadGuard::map(self.predecessors.borrow(), |p| p.as_ref().unwrap())
}
}
fn calculate_predecessors(body: &Body<'_>) -> IndexVec<BasicBlock, Vec<BasicBlock>> {
let mut result = IndexVec::from_elem(vec![], body.basic_blocks());
for (bb, data) in body.basic_blocks().iter_enumerated() {
if let Some(ref term) = data.terminator {
for &tgt in term.successors() {
result[tgt].push(bb);
}
}
}
result
}
CloneTypeFoldableAndLiftImpls! {
Cache,
}
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