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Diffstat (limited to 'compiler/rustc_middle/src/mir/switch_sources.rs')
-rw-r--r-- | compiler/rustc_middle/src/mir/switch_sources.rs | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/mir/switch_sources.rs b/compiler/rustc_middle/src/mir/switch_sources.rs new file mode 100644 index 000000000..b91c0c257 --- /dev/null +++ b/compiler/rustc_middle/src/mir/switch_sources.rs @@ -0,0 +1,78 @@ +//! Lazily compute the inverse of each `SwitchInt`'s switch targets. Modeled after +//! `Predecessors`/`PredecessorCache`. + +use rustc_data_structures::fx::FxHashMap; +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, Terminator, TerminatorKind}; + +pub type SwitchSources = FxHashMap<(BasicBlock, 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: SwitchSources = FxHashMap::default(); + 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.entry((target, bb)).or_default().push(Some(value)); + } + switch_sources.entry((targets.otherwise(), bb)).or_default().push(None); + } + } + + switch_sources + }) + } +} + +impl<S: Encoder> Encodable<S> for SwitchSourceCache { + #[inline] + fn encode(&self, _s: &mut S) {} +} + +impl<D: Decoder> 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 + } +} + +TrivialTypeTraversalAndLiftImpls! { + SwitchSourceCache, +} |