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//! Lazily compute the inverse of each `SwitchInt`'s switch targets. Modeled after
//! `Predecessors`/`PredecessorCache`.
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_data_structures::sync::OnceCell;
use rustc_index::vec::IndexVec;
use rustc_serialize as serialize;
use smallvec::SmallVec;
use crate::mir::{BasicBlock, BasicBlockData, Terminator, TerminatorKind};
pub type SwitchSources = IndexVec<BasicBlock, IndexVec<BasicBlock, SmallVec<[Option<u128>; 1]>>>;
#[derive(Clone, Debug)]
pub(super) struct SwitchSourceCache {
cache: OnceCell<SwitchSources>,
}
impl SwitchSourceCache {
#[inline]
pub(super) fn new() -> Self {
SwitchSourceCache { cache: OnceCell::new() }
}
/// Invalidates the switch source cache.
#[inline]
pub(super) fn invalidate(&mut self) {
self.cache = OnceCell::new();
}
/// Returns the switch sources for this MIR.
#[inline]
pub(super) fn compute(
&self,
basic_blocks: &IndexVec<BasicBlock, BasicBlockData<'_>>,
) -> &SwitchSources {
self.cache.get_or_init(|| {
let mut switch_sources = IndexVec::from_elem(
IndexVec::from_elem(SmallVec::new(), basic_blocks),
basic_blocks,
);
for (bb, data) in basic_blocks.iter_enumerated() {
if let Some(Terminator {
kind: TerminatorKind::SwitchInt { targets, .. }, ..
}) = &data.terminator
{
for (value, target) in targets.iter() {
switch_sources[target][bb].push(Some(value));
}
switch_sources[targets.otherwise()][bb].push(None);
}
}
switch_sources
})
}
}
impl<S: serialize::Encoder> serialize::Encodable<S> for SwitchSourceCache {
#[inline]
fn encode(&self, s: &mut S) -> Result<(), S::Error> {
s.emit_unit()
}
}
impl<D: serialize::Decoder> serialize::Decodable<D> for SwitchSourceCache {
#[inline]
fn decode(_: &mut D) -> Self {
Self::new()
}
}
impl<CTX> HashStable<CTX> for SwitchSourceCache {
#[inline]
fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {
// do nothing
}
}
TrivialTypeFoldableAndLiftImpls! {
SwitchSourceCache,
}
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