add graph algorithms and add dominator to cache

src/librustc/lib.rs

@@ -110,6 +110,7 @@ pub mod mir {
     pub mod transform;
     pub mod traversal;
     pub mod mir_map;
+    pub mod mir_cfg;
 }
 
 pub mod session;

src/librustc/mir/cache.rs

@@ -10,14 +10,17 @@
 
 use std::cell::{Ref, RefCell};
 use rustc_data_structures::indexed_vec::IndexVec;
+use rustc_data_structures::graph_algorithms::dominators::{Dominators, dominators};
+use mir::mir_cfg::MirCfg;
 
 use mir::repr::{Mir, BasicBlock};
 
 use rustc_serialize as serialize;
 
 #[derive(Clone)]
 pub struct Cache {
-    predecessors: RefCell<Option<IndexVec<BasicBlock, Vec<BasicBlock>>>>
+    predecessors: RefCell<Option<IndexVec<BasicBlock, Vec<BasicBlock>>>>,
+    dominators: RefCell<Option<Dominators<MirCfg>>>,
 }
 
 
@@ -33,11 +36,11 @@ impl serialize::Decodable for Cache {
     }
 }
 
-
 impl Cache {
     pub fn new() -> Self {
         Cache {
-            predecessors: RefCell::new(None)
+            predecessors: RefCell::new(None),
+            dominators: RefCell::new(None),
         }
     }
 
@@ -53,6 +56,14 @@ impl Cache {
 
         Ref::map(self.predecessors.borrow(), |p| p.as_ref().unwrap())
     }
+
+    pub fn dominators(&self, mir: &Mir) -> Ref<Dominators<MirCfg>> {
+        if self.dominators.borrow().is_none() {
+            *self.dominators.borrow_mut() = Some(calculate_dominators(mir, self));
+        }
+
+        Ref::map(self.dominators.borrow(), |p| p.as_ref().unwrap())
+    }
 }
 
 fn calculate_predecessors(mir: &Mir) -> IndexVec<BasicBlock, Vec<BasicBlock>> {
@@ -67,3 +78,8 @@ fn calculate_predecessors(mir: &Mir) -> IndexVec<BasicBlock, Vec<BasicBlock>> {
 
     result
 }
+
+fn calculate_dominators(mir: &Mir, cache: &Cache) -> Dominators<MirCfg> {
+    let m = MirCfg::new(mir, cache);
+    dominators(&m)
+}

src/librustc/mir/mir_cfg.rs

@@ -0,0 +1,78 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::{iter, slice};
+use rustc_data_structures::indexed_vec::IndexVec;
+use rustc_data_structures::graph_algorithms::{Graph, GraphPredecessors, GraphSuccessors};
+use mir::repr::{Mir, BasicBlock, START_BLOCK};
+use mir::cache::Cache;
+
+impl MirCfg {
+    pub fn new<'a, 'tcx>(mir: &Mir, cache: &Cache) -> Self {
+        MirCfg {
+            predecessors: cache.predecessors(mir).clone(),
+            successors: calculate_successors(mir),
+            n_nodes: mir.basic_blocks().len(),
+            start_node: START_BLOCK,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct MirCfg {
+    predecessors: IndexVec<BasicBlock,Vec<BasicBlock>>,
+    successors: IndexVec<BasicBlock,Vec<BasicBlock>>,
+    start_node: BasicBlock,
+    n_nodes: usize,
+}
+
+impl Graph for MirCfg {
+
+    type Node = BasicBlock;
+
+    fn num_nodes(&self) -> usize { self.n_nodes }
+
+    fn start_node(&self) -> Self::Node { self.start_node }
+
+    fn predecessors<'graph>(&'graph self, node: Self::Node)
+                            -> <Self as GraphPredecessors<'graph>>::Iter
+    {
+        self.predecessors[node].iter().cloned()
+    }
+    fn successors<'graph>(&'graph self, node: Self::Node)
+                            -> <Self as GraphSuccessors<'graph>>::Iter
+    {
+        self.successors[node].iter().cloned()
+    }
+}
+
+impl<'g> GraphPredecessors<'g> for MirCfg {
+    type Item = BasicBlock;
+    type Iter = iter::Cloned<slice::Iter<'g, BasicBlock>>;
+}
+
+impl<'g>  GraphSuccessors<'g> for MirCfg {
+   type Item = BasicBlock;
+    type Iter = iter::Cloned<slice::Iter<'g, BasicBlock>>;
+}
+
+fn calculate_successors<'a, 'tcx>(mir: &'a Mir<'tcx>) -> IndexVec<BasicBlock, Vec<BasicBlock>> {
+    let mut successors = IndexVec::from_elem(vec![], mir.basic_blocks());
+    for (bb, data) in mir.basic_blocks().iter_enumerated() {
+        if let Some(ref term) = data.terminator {
+            successors[bb].append(term.successors().to_mut());
+        }
+    }
+    for ss in successors.iter_mut() {
+        ss.sort();
+        ss.dedup();
+    }
+    successors
+}

src/librustc/mir/repr.rs

@@ -12,6 +12,7 @@ use graphviz::IntoCow;
 use middle::const_val::ConstVal;
 use rustc_const_math::{ConstUsize, ConstInt, ConstMathErr};
 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
+use rustc_data_structures::graph_algorithms::NodeIndex;
 use hir::def_id::DefId;
 use ty::subst::Substs;
 use ty::{self, AdtDef, ClosureSubsts, FnOutput, Region, Ty};
@@ -162,6 +163,24 @@ impl<'tcx> IndexMut<BasicBlock> for Mir<'tcx> {
     }
 }
 
+impl From<usize> for BasicBlock {
+    fn from(n: usize) -> BasicBlock {
+        assert!(n < (u32::MAX as usize));
+        BasicBlock(n as u32)
+    }
+}
+impl Into<usize> for BasicBlock {
+    fn into(self: BasicBlock) -> usize {
+        self.index()
+    }
+}
+
+impl NodeIndex for BasicBlock {
+    fn as_usize(self) -> usize {
+        self.index()
+    }
+}
+
 /// Grouped information about the source code origin of a MIR entity.
 /// Intended to be inspected by diagnostics and debuginfo.
 /// Most passes can work with it as a whole, within a single function.