src/librustc/mir/cache.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use rustc_data_structures::indexed_vec::IndexVec;
  12 use rustc_data_structures::sync::{RwLock, MappedReadGuard, ReadGuard};
  13 use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
  14                                            StableHasherResult};
  15 use ich::StableHashingContext;
  16 use mir::{Mir, BasicBlock};
  17
  18 use rustc_serialize as serialize;
  19
  20 #[derive(Clone, Debug)]
  21 pub struct Cache {
  22     predecessors: RwLock<Option<IndexVec<BasicBlock, Vec<BasicBlock>>>>
  23 }
  24
  25
  26 impl serialize::Encodable for Cache {
  27     fn encode<S: serialize::Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
  28         serialize::Encodable::encode(&(), s)
  29     }
  30 }
  31
  32 impl serialize::Decodable for Cache {
  33     fn decode<D: serialize::Decoder>(d: &mut D) -> Result<Self, D::Error> {
  34         serialize::Decodable::decode(d).map(|_v: ()| Self::new())
  35     }
  36 }
  37
  38 impl<'a> HashStable<StableHashingContext<'a>> for Cache {
  39     fn hash_stable<W: StableHasherResult>(&self,
  40                                           _: &mut StableHashingContext<'a>,
  41                                           _: &mut StableHasher<W>) {
  42         // do nothing
  43     }
  44 }
  45
  46 impl Cache {
  47     pub fn new() -> Self {
  48         Cache {
  49             predecessors: RwLock::new(None)
  50         }
  51     }
  52
  53     pub fn invalidate(&self) {
  54         // FIXME: consider being more fine-grained
  55         *self.predecessors.borrow_mut() = None;
  56     }
  57
  58     pub fn predecessors(
  59         &self,
  60         mir: &Mir<'_>
  61     ) -> MappedReadGuard<'_, IndexVec<BasicBlock, Vec<BasicBlock>>> {
  62         if self.predecessors.borrow().is_none() {
  63             *self.predecessors.borrow_mut() = Some(calculate_predecessors(mir));
  64         }
  65
  66         ReadGuard::map(self.predecessors.borrow(), |p| p.as_ref().unwrap())
  67     }
  68 }
  69
  70 fn calculate_predecessors(mir: &Mir<'_>) -> IndexVec<BasicBlock, Vec<BasicBlock>> {
  71     let mut result = IndexVec::from_elem(vec![], mir.basic_blocks());
  72     for (bb, data) in mir.basic_blocks().iter_enumerated() {
  73         if let Some(ref term) = data.terminator {
  74             for &tgt in term.successors() {
  75                 result[tgt].push(bb);
  76             }
  77         }
  78     }
  79
  80     result
  81 }
  82
  83 CloneTypeFoldableAndLiftImpls! {
  84     Cache,
  85 }