src/librustc/mir/cache.rs

   1 use rustc_index::vec::IndexVec;
   2 use rustc_data_structures::sync::{RwLock, MappedReadGuard, ReadGuard};
   3 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
   4 use rustc_serialize::{Encodable, Encoder, Decodable, Decoder};
   5 use crate::ich::StableHashingContext;
   6 use crate::mir::{Body, BasicBlock};
   7
   8 #[derive(Clone, Debug)]
   9 pub struct Cache {
  10     predecessors: RwLock<Option<IndexVec<BasicBlock, Vec<BasicBlock>>>>
  11 }
  12
  13
  14 impl rustc_serialize::Encodable for Cache {
  15     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
  16         Encodable::encode(&(), s)
  17     }
  18 }
  19
  20 impl rustc_serialize::Decodable for Cache {
  21     fn decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
  22         Decodable::decode(d).map(|_v: ()| Self::new())
  23     }
  24 }
  25
  26 impl<'a> HashStable<StableHashingContext<'a>> for Cache {
  27     fn hash_stable(&self, _: &mut StableHashingContext<'a>, _: &mut StableHasher) {
  28         // Do nothing.
  29     }
  30 }
  31
  32 impl Cache {
  33     pub fn new() -> Self {
  34         Cache {
  35             predecessors: RwLock::new(None)
  36         }
  37     }
  38
  39     pub fn invalidate(&self) {
  40         // FIXME: consider being more fine-grained
  41         *self.predecessors.borrow_mut() = None;
  42     }
  43
  44     pub fn predecessors(
  45         &self,
  46         body: &Body<'_>
  47     ) -> MappedReadGuard<'_, IndexVec<BasicBlock, Vec<BasicBlock>>> {
  48         if self.predecessors.borrow().is_none() {
  49             *self.predecessors.borrow_mut() = Some(calculate_predecessors(body));
  50         }
  51
  52         ReadGuard::map(self.predecessors.borrow(), |p| p.as_ref().unwrap())
  53     }
  54 }
  55
  56 fn calculate_predecessors(body: &Body<'_>) -> IndexVec<BasicBlock, Vec<BasicBlock>> {
  57     let mut result = IndexVec::from_elem(vec![], body.basic_blocks());
  58     for (bb, data) in body.basic_blocks().iter_enumerated() {
  59         if let Some(ref term) = data.terminator {
  60             for &tgt in term.successors() {
  61                 result[tgt].push(bb);
  62             }
  63         }
  64     }
  65
  66     result
  67 }
  68
  69 CloneTypeFoldableAndLiftImpls! {
  70     Cache,
  71 }