src/librustc/mir/cache.rs

   1 use rustc_data_structures::indexed_vec::IndexVec;
   2 use rustc_data_structures::sync::{RwLock, MappedReadGuard, ReadGuard};
   3 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableHasherResult};
   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<W: StableHasherResult>(&self,
  28                                           _: &mut StableHashingContext<'a>,
  29                                           _: &mut StableHasher<W>) {
  30         // Do nothing.
  31     }
  32 }
  33
  34 impl Cache {
  35     pub fn new() -> Self {
  36         Cache {
  37             predecessors: RwLock::new(None)
  38         }
  39     }
  40
  41     pub fn invalidate(&self) {
  42         // FIXME: consider being more fine-grained
  43         *self.predecessors.borrow_mut() = None;
  44     }
  45
  46     pub fn predecessors(
  47         &self,
  48         body: &Body<'_>
  49     ) -> MappedReadGuard<'_, IndexVec<BasicBlock, Vec<BasicBlock>>> {
  50         if self.predecessors.borrow().is_none() {
  51             *self.predecessors.borrow_mut() = Some(calculate_predecessors(body));
  52         }
  53
  54         ReadGuard::map(self.predecessors.borrow(), |p| p.as_ref().unwrap())
  55     }
  56 }
  57
  58 fn calculate_predecessors(body: &Body<'_>) -> IndexVec<BasicBlock, Vec<BasicBlock>> {
  59     let mut result = IndexVec::from_elem(vec![], body.basic_blocks());
  60     for (bb, data) in body.basic_blocks().iter_enumerated() {
  61         if let Some(ref term) = data.terminator {
  62             for &tgt in term.successors() {
  63                 result[tgt].push(bb);
  64             }
  65         }
  66     }
  67
  68     result
  69 }
  70
  71 CloneTypeFoldableAndLiftImpls! {
  72     Cache,
  73 }