Move predecessor cache outside of Body, use wrapper types to manage C…

…ache and Body (WIP, amend this commit)

src/librustc/mir/cache.rs

@@ -1,47 +1,255 @@
 use rustc_index::vec::IndexVec;
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_serialize::{Encodable, Encoder, Decodable, Decoder};
-use crate::ich::StableHashingContext;
-use crate::mir::BasicBlock;
+//use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+//use rustc_serialize::{Encodable, Encoder, Decodable, Decoder};
+//use crate::ich::StableHashingContext;
+use crate::mir::{BasicBlock, BasicBlockData, Body, LocalDecls, Location, Successors};
+use rustc_data_structures::graph::{self, GraphPredecessors, GraphSuccessors};
+use rustc_data_structures::graph::dominators::{dominators, Dominators};
+use std::iter;
+use std::ops::{Index, IndexMut};
+use std::vec::IntoIter;
 
 #[derive(Clone, Debug)]
-pub(in crate::mir) struct Cache {
-    pub(in crate::mir) predecessors: Option<IndexVec<BasicBlock, Vec<BasicBlock>>>
+pub struct Cache {
+    predecessors: Option<IndexVec<BasicBlock, Vec<BasicBlock>>>,
 }
 
 
-impl rustc_serialize::Encodable for Cache {
-    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
-        Encodable::encode(&(), s)
+//impl<'tcx, T> rustc_serialize::Encodable for Cache<'tcx, T> {
+//    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
+//        Encodable::encode(&(), s)
+//    }
+//}
+//
+//impl<'tcx, T> rustc_serialize::Decodable for Cache<'tcx, T> {
+//    fn decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
+//        Decodable::decode(d).map(|_v: ()| Self::new())
+//    }
+//}
+//
+//impl<'a, 'tcx, T> HashStable<StableHashingContext<'a>> for Cache<'tcx, T> {
+//    fn hash_stable(&self, _: &mut StableHashingContext<'a>, _: &mut StableHasher) {
+//        // Do nothing.
+//    }
+//}
+
+impl Cache {
+    pub fn new() -> Self {
+        Self {
+            predecessors: None,
+        }
+    }
+
+    #[inline]
+    pub fn invalidate_predecessors(&mut self) {
+        // FIXME: consider being more fine-grained
+        self.predecessors = None;
+    }
+
+    #[inline]
+    /// This will recompute the predecessors cache if it is not available
+    pub fn predecessors(&mut self, body: &Body<'_>) -> &IndexVec<BasicBlock, Vec<BasicBlock>> {
+        if self.predecessors.is_none() {
+            let mut result = IndexVec::from_elem(vec![], body.basic_blocks());
+            for (bb, data) in body.basic_blocks().iter_enumerated() {
+                if let Some(ref term) = data.terminator {
+                    for &tgt in term.successors() {
+                        result[tgt].push(bb);
+                    }
+                }
+            }
+
+            self.predecessors = Some(result)
+        }
+
+        self.predecessors.as_ref().unwrap()
+    }
+
+    #[inline]
+    pub fn predecessors_for(&mut self, bb: BasicBlock, body: &Body<'_>) -> &[BasicBlock] {
+        &self.predecessors(body)[bb]
+    }
+
+    #[inline]
+    pub fn predecessor_locations<'a>(&'a mut self, loc: Location, body: &'a Body<'a>) -> impl Iterator<Item = Location> + 'a {
+        let if_zero_locations = if loc.statement_index == 0 {
+            let predecessor_blocks = self.predecessors_for(loc.block, body);
+            let num_predecessor_blocks = predecessor_blocks.len();
+            Some(
+                (0..num_predecessor_blocks)
+                    .map(move |i| predecessor_blocks[i])
+                    .map(move |bb| body.terminator_loc(bb)),
+            )
+        } else {
+            None
+        };
+
+        let if_not_zero_locations = if loc.statement_index == 0 {
+            None
+        } else {
+            Some(Location { block: loc.block, statement_index: loc.statement_index - 1 })
+        };
+
+        if_zero_locations.into_iter().flatten().chain(if_not_zero_locations)
+    }
+
+    #[inline]
+    pub fn basic_blocks_mut<'a, 'tcx>(&mut self, body: &'a mut Body<'tcx>) -> &'a mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
+        debug!("bbm: Clearing predecessors cache for body at: {:?}", body.span.data());
+        self.invalidate_predecessors();
+        &mut body.basic_blocks
+    }
+
+    #[inline]
+    pub fn basic_blocks_and_local_decls_mut<'a, 'tcx>(
+        &mut self,
+        body: &'a mut Body<'tcx>
+    ) -> (&'a mut IndexVec<BasicBlock, BasicBlockData<'tcx>>, &'a mut LocalDecls<'tcx>) {
+        debug!("bbaldm: Clearing predecessors cache for body at: {:?}", body.span.data());
+        self.invalidate_predecessors();
+        (&mut body.basic_blocks, &mut body.local_decls)
+    }
+}
+
+pub struct OwningCache<'tcx> {
+    cache: Cache,
+    body: Body<'tcx>,
+}
+
+impl<'tcx> OwningCache<'tcx> {
+    pub fn borrow(&mut self) -> BorrowedCache<'_, 'tcx> {
+        BorrowedCache {
+            cache: &mut self.cache,
+            body: &self.body,
+        }
+    }
+
+    pub fn borrow_mut(&mut self) -> MutCache<'_, 'tcx> {
+        MutCache {
+            cache: &mut self.cache,
+            body: &mut self.body,
+        }
+    }
+}
+
+pub struct BorrowedCache<'a, 'tcx> {
+    cache: &'a mut Cache,
+    body: &'a Body<'tcx>
+}
+
+impl<'a, 'tcx> BorrowedCache<'a, 'tcx> {
+    #[inline]
+    pub fn predecessors_for(&mut self, bb: BasicBlock) -> &[BasicBlock] {
+        self.cache.predecessors_for(bb, self.body)
+    }
+
+    #[inline]
+    pub fn body(&self) -> &Body<'tcx> {
+        self.body
+    }
+
+    #[inline]
+    pub fn basic_blocks(&self) -> &IndexVec<BasicBlock, BasicBlockData<'tcx>> {
+        &self.body.basic_blocks
+    }
+
+    #[inline]
+    pub fn dominators(&mut self) -> Dominators<BasicBlock> {
+        dominators(self)
     }
 }
 
-impl rustc_serialize::Decodable for Cache {
-    fn decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error> {
-        Decodable::decode(d).map(|_v: ()| Self::new())
+impl<'a, 'tcx> Index<BasicBlock> for BorrowedCache<'a, 'tcx> {
+    type Output = BasicBlockData<'tcx>;
+
+    #[inline]
+    fn index(&self, index: BasicBlock) -> &BasicBlockData<'tcx> {
+        &self.body[index]
     }
 }
 
-impl<'a> HashStable<StableHashingContext<'a>> for Cache {
-    fn hash_stable(&self, _: &mut StableHashingContext<'a>, _: &mut StableHasher) {
-        // Do nothing.
+impl<'a, 'tcx> graph::DirectedGraph for BorrowedCache<'a, 'tcx> {
+    type Node = BasicBlock;
+}
+
+impl<'a, 'graph, 'tcx> graph::GraphPredecessors<'graph> for BorrowedCache<'a, 'tcx> {
+    type Item = BasicBlock;
+    type Iter = IntoIter<BasicBlock>;
+}
+
+impl<'a, 'tcx> graph::WithPredecessors for BorrowedCache<'a, 'tcx> {
+    fn predecessors(
+        &mut self,
+        node: Self::Node,
+    ) -> <Self as GraphPredecessors<'_>>::Iter {
+        self.predecessors_for(node).to_vec().into_iter()
     }
 }
 
-impl Cache {
-    pub fn new() -> Self {
-        Cache {
-            predecessors: None
-        }
+impl<'a, 'tcx> graph::WithNumNodes for BorrowedCache<'a, 'tcx> {
+    fn num_nodes(&self) -> usize {
+        self.body.num_nodes()
     }
+}
 
+impl<'a, 'tcx> graph::WithStartNode for BorrowedCache<'a, 'tcx> {
+    fn start_node(&self) -> Self::Node {
+        self.body.start_node()
+    }
+}
+
+impl<'a, 'tcx> graph::WithSuccessors for BorrowedCache<'a, 'tcx> {
+    fn successors(
+        &self,
+        node: Self::Node,
+    ) -> <Self as GraphSuccessors<'_>>::Iter {
+        self.body.successors(node)
+    }
+}
+
+impl<'a, 'b, 'tcx> graph::GraphSuccessors<'b> for BorrowedCache<'a, 'tcx> {
+    type Item = BasicBlock;
+    type Iter = iter::Cloned<Successors<'b>>;
+}
+
+pub struct MutCache<'a, 'tcx> {
+    cache: &'a mut Cache,
+    body: &'a mut Body<'tcx>,
+}
+
+impl<'a, 'tcx> MutCache<'a, 'tcx> {
     #[inline]
-    pub fn invalidate_predecessors(&mut self) {
-        // FIXME: consider being more fine-grained
-        self.predecessors = None;
+    pub fn body(&mut self) -> &mut Body<'tcx> {
+        self.body
+    }
+
+    #[inline]
+    pub fn basic_blocks(&self) -> &IndexVec<BasicBlock, BasicBlockData<'tcx>> {
+        &self.body.basic_blocks
+    }
+
+    #[inline]
+    pub fn basic_blocks_mut(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> {
+        self.cache.basic_blocks_mut(&mut self.body)
     }
 }
 
-CloneTypeFoldableAndLiftImpls! {
-    Cache,
+impl<'a, 'tcx> Index<BasicBlock> for MutCache<'a, 'tcx> {
+    type Output = BasicBlockData<'tcx>;
+
+    #[inline]
+    fn index(&self, index: BasicBlock) -> &BasicBlockData<'tcx> {
+        &self.body[index]
+    }
 }
+
+impl<'a, 'tcx> IndexMut<BasicBlock> for MutCache<'a, 'tcx> {
+    fn index_mut(&mut self, index: BasicBlock) -> &mut Self::Output {
+        self.cache.invalidate_predecessors();
+        &mut self.body.basic_blocks[index]
+    }
+}
+
+//CloneTypeFoldableAndLiftImpls! {
+//    Cache,
+//}