diff --git a/src/librustc/middle/graph.rs b/src/librustc/middle/graph.rs
new file mode 100644
index 00000000000..804dc88746c
--- /dev/null
+++ b/src/librustc/middle/graph.rs
@@ -0,0 +1,411 @@
+// Copyright 2012 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.
+
+/*!
+
+A graph module for use in dataflow, region resolution, and elsewhere.
+
+# Interface details
+
+You customize the graph by specifying a "node data" type `N` and an
+"edge data" type `E`. You can then later gain access (mutable or
+immutable) to these "user-data" bits. Currently, you can only add
+nodes or edges to the graph. You cannot remove or modify them once
+added. This could be changed if we have a need.
+
+# Implementation details
+
+The main tricky thing about this code is the way that edges are
+stored. The edges are stored in a central array, but they are also
+threaded onto two linked lists for each node, one for incoming edges
+and one for outgoing edges. Note that every edge is a member of some
+incoming list and some outgoing list.  Basically you can load the
+first index of the linked list from the node data structures (the
+field `first_edge`) and then, for each edge, load the next index from
+the field `next_edge`). Each of those fields is an array that should
+be indexed by the direction (see the type `Direction`).
+
+*/
+
+use std::prelude::*;
+use std::uint;
+use std::vec;
+
+pub struct Graph<N,E> {
+    priv nodes: ~[Node<N>],
+    priv edges: ~[Edge<E>],
+}
+
+pub struct Node<N> {
+    priv first_edge: [EdgeIndex, ..2], // see module comment
+    data: N,
+}
+
+pub struct Edge<E> {
+    priv next_edge: [EdgeIndex, ..2], // see module comment
+    priv source: NodeIndex,
+    priv target: NodeIndex,
+    data: E,
+}
+
+#[deriving(Eq)]
+pub struct NodeIndex(uint);
+pub static InvalidNodeIndex: NodeIndex = NodeIndex(uint::max_value);
+
+#[deriving(Eq)]
+pub struct EdgeIndex(uint);
+pub static InvalidEdgeIndex: EdgeIndex = EdgeIndex(uint::max_value);
+
+// Use a private field here to guarantee no more instances are created:
+pub struct Direction { priv repr: uint }
+pub static Outgoing: Direction = Direction { repr: 0 };
+pub static Incoming: Direction = Direction { repr: 1 };
+
+impl<N,E> Graph<N,E> {
+    pub fn new() -> Graph<N,E> {
+        Graph {nodes: ~[], edges: ~[]}
+    }
+
+    pub fn with_capacity(num_nodes: uint,
+                         num_edges: uint) -> Graph<N,E> {
+        Graph {nodes: vec::with_capacity(num_nodes),
+               edges: vec::with_capacity(num_edges)}
+    }
+
+    ///////////////////////////////////////////////////////////////////////////
+    // Simple accessors
+
+    #[inline]
+    pub fn all_nodes<'a>(&'a self) -> &'a [Node<N>] {
+        let nodes: &'a [Node<N>] = self.nodes;
+        nodes
+    }
+
+    #[inline]
+    pub fn all_edges<'a>(&'a self) -> &'a [Edge<E>] {
+        let edges: &'a [Edge<E>] = self.edges;
+        edges
+    }
+
+    ///////////////////////////////////////////////////////////////////////////
+    // Node construction
+
+    pub fn next_node_index(&self) -> NodeIndex {
+        NodeIndex(self.nodes.len())
+    }
+
+    pub fn add_node(&mut self, data: N) -> NodeIndex {
+        let idx = self.next_node_index();
+        self.nodes.push(Node {
+            first_edge: [InvalidEdgeIndex, InvalidEdgeIndex],
+            data: data
+        });
+        idx
+    }
+
+    pub fn mut_node_data<'a>(&'a mut self, idx: NodeIndex) -> &'a mut N {
+        &mut self.nodes[*idx].data
+    }
+
+    pub fn node_data<'a>(&'a self, idx: NodeIndex) -> &'a N {
+        &self.nodes[*idx].data
+    }
+
+    pub fn node<'a>(&'a self, idx: NodeIndex) -> &'a Node<N> {
+        &self.nodes[*idx]
+    }
+
+    ///////////////////////////////////////////////////////////////////////////
+    // Edge construction and queries
+
+    pub fn next_edge_index(&self) -> EdgeIndex {
+        EdgeIndex(self.edges.len())
+    }
+
+    pub fn add_edge(&mut self,
+                    source: NodeIndex,
+                    target: NodeIndex,
+                    data: E) -> EdgeIndex {
+        let idx = self.next_edge_index();
+
+        // read current first of the list of edges from each node
+        let source_first = self.nodes[*source].first_edge[Outgoing.repr];
+        let target_first = self.nodes[*target].first_edge[Incoming.repr];
+
+        // create the new edge, with the previous firsts from each node
+        // as the next pointers
+        self.edges.push(Edge {
+            next_edge: [source_first, target_first],
+            source: source,
+            target: target,
+            data: data
+        });
+
+        // adjust the firsts for each node target be the next object.
+        self.nodes[*source].first_edge[Outgoing.repr] = idx;
+        self.nodes[*target].first_edge[Incoming.repr] = idx;
+
+        return idx;
+    }
+
+    pub fn mut_edge_data<'a>(&'a mut self, idx: EdgeIndex) -> &'a mut E {
+        &mut self.edges[*idx].data
+    }
+
+    pub fn edge_data<'a>(&'a self, idx: EdgeIndex) -> &'a E {
+        &self.edges[*idx].data
+    }
+
+    pub fn edge<'a>(&'a self, idx: EdgeIndex) -> &'a Edge<E> {
+        &self.edges[*idx]
+    }
+
+    pub fn first_adjacent(&self, node: NodeIndex, dir: Direction) -> EdgeIndex {
+        //! Accesses the index of the first edge adjacent to `node`.
+        //! This is useful if you wish to modify the graph while walking
+        //! the linked list of edges.
+
+        self.nodes[*node].first_edge[dir.repr]
+    }
+
+    pub fn next_adjacent(&self, edge: EdgeIndex, dir: Direction) -> EdgeIndex {
+        //! Accesses the next edge in a given direction.
+        //! This is useful if you wish to modify the graph while walking
+        //! the linked list of edges.
+
+        self.edges[*edge].next_edge[dir.repr]
+    }
+
+    ///////////////////////////////////////////////////////////////////////////
+    // Iterating over nodes, edges
+
+    pub fn each_node(&self, f: &fn(NodeIndex, &Node<N>) -> bool) -> bool {
+        //! Iterates over all edges defined in the graph.
+
+        uint::range(0, self.nodes.len(),
+                    |i| f(NodeIndex(i), &self.nodes[i]))
+    }
+
+    pub fn each_edge(&self, f: &fn(EdgeIndex, &Edge<E>) -> bool) -> bool {
+        //! Iterates over all edges defined in the graph.
+
+        uint::range(0, self.nodes.len(),
+                    |i| f(EdgeIndex(i), &self.edges[i]))
+    }
+
+    pub fn each_outgoing_edge(&self,
+                              source: NodeIndex,
+                              f: &fn(EdgeIndex, &Edge<E>) -> bool) -> bool {
+        //! Iterates over all outgoing edges from the node `from`
+
+        self.each_adjacent_edge(source, Outgoing, f)
+    }
+
+    pub fn each_incoming_edge(&self,
+                              target: NodeIndex,
+                              f: &fn(EdgeIndex, &Edge<E>) -> bool) -> bool {
+        //! Iterates over all incoming edges to the node `target`
+
+        self.each_adjacent_edge(target, Incoming, f)
+    }
+
+    pub fn each_adjacent_edge(&self,
+                              node: NodeIndex,
+                              dir: Direction,
+                              f: &fn(EdgeIndex, &Edge<E>) -> bool) -> bool {
+        //! Iterates over all edges adjacent to the node `node`
+        //! in the direction `dir` (either `Outgoing` or `Incoming)
+
+        let mut edge_idx = self.first_adjacent(node, dir);
+        while edge_idx != InvalidEdgeIndex {
+            let edge = &self.edges[*edge_idx];
+            if !f(edge_idx, edge) {
+                return false;
+            }
+            edge_idx = edge.next_edge[dir.repr];
+        }
+        return true;
+    }
+
+    ///////////////////////////////////////////////////////////////////////////
+    // Fixed-point iteration
+    //
+    // A common use for graphs in our compiler is to perform
+    // fixed-point iteration. In this case, each edge represents a
+    // constaint, and the nodes themselves are associated with
+    // variables or other bitsets. This method facilitates such a
+    // computation.
+
+    pub fn iterate_until_fixed_point(&self,
+                                     op: &fn(iter_index: uint,
+                                             edge_index: EdgeIndex,
+                                             edge: &Edge<E>) -> bool) {
+        let mut iteration = 0;
+        let mut changed = true;
+        while changed {
+            changed = false;
+            iteration += 1;
+            for self.edges.iter().enumerate().advance |(i, edge)| {
+                changed |= op(iteration, EdgeIndex(i), edge);
+            }
+        }
+    }
+}
+
+pub fn each_edge_index(max_edge_index: EdgeIndex, f: &fn(EdgeIndex) -> bool) {
+    let mut i = 0;
+    let n = *max_edge_index;
+    while i < n {
+        if !f(EdgeIndex(i)) {
+            return;
+        }
+        i += 1;
+    }
+}
+
+impl<E> Edge<E> {
+    pub fn source(&self) -> NodeIndex {
+        self.source
+    }
+
+    pub fn target(&self) -> NodeIndex {
+        self.target
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use middle::graph::*;
+
+    type TestNode = Node<&'static str>;
+    type TestEdge = Edge<&'static str>;
+    type TestGraph = Graph<&'static str, &'static str>;
+
+    fn create_graph() -> TestGraph {
+        let mut graph = Graph::new();
+
+        // Create a simple graph
+        //
+        //    A -+> B --> C
+        //       |  |     ^
+        //       |  v     |
+        //       F  D --> E
+
+        let a = graph.add_node("A");
+        let b = graph.add_node("B");
+        let c = graph.add_node("C");
+        let d = graph.add_node("D");
+        let e = graph.add_node("E");
+        let f = graph.add_node("F");
+
+        graph.add_edge(a, b, "AB");
+        graph.add_edge(b, c, "BC");
+        graph.add_edge(b, d, "BD");
+        graph.add_edge(d, e, "DE");
+        graph.add_edge(e, c, "EC");
+        graph.add_edge(f, b, "FB");
+
+        return graph;
+    }
+
+    #[test]
+    fn each_node() {
+        let graph = create_graph();
+        let expected = ["A", "B", "C", "D", "E", "F"];
+        for graph.each_node |idx, node| {
+            assert_eq!(&expected[*idx], graph.node_data(idx));
+            assert_eq!(expected[*idx], node.data);
+        }
+    }
+
+    #[test]
+    fn each_edge() {
+        let graph = create_graph();
+        let expected = ["AB", "BC", "BD", "DE", "EC", "FB"];
+        for graph.each_edge |idx, edge| {
+            assert_eq!(&expected[*idx], graph.edge_data(idx));
+            assert_eq!(expected[*idx], edge.data);
+        }
+    }
+
+    fn test_adjacent_edges<N:Eq,E:Eq>(graph: &Graph<N,E>,
+                                      start_index: NodeIndex,
+                                      start_data: N,
+                                      expected_incoming: &[(E,N)],
+                                      expected_outgoing: &[(E,N)]) {
+        assert_eq!(graph.node_data(start_index), &start_data);
+
+        let mut counter = 0;
+        for graph.each_incoming_edge(start_index) |edge_index, edge| {
+            assert_eq!(graph.edge_data(edge_index), &edge.data);
+            assert!(counter < expected_incoming.len());
+            debug!("counter=%? expected=%? edge_index=%? edge=%?",
+                   counter, expected_incoming[counter], edge_index, edge);
+            match expected_incoming[counter] {
+                (ref e, ref n) => {
+                    assert_eq!(e, &edge.data);
+                    assert_eq!(n, graph.node_data(edge.source));
+                    assert_eq!(start_index, edge.target);
+                }
+            }
+            counter += 1;
+        }
+        assert_eq!(counter, expected_incoming.len());
+
+        let mut counter = 0;
+        for graph.each_outgoing_edge(start_index) |edge_index, edge| {
+            assert_eq!(graph.edge_data(edge_index), &edge.data);
+            assert!(counter < expected_outgoing.len());
+            debug!("counter=%? expected=%? edge_index=%? edge=%?",
+                   counter, expected_outgoing[counter], edge_index, edge);
+            match expected_outgoing[counter] {
+                (ref e, ref n) => {
+                    assert_eq!(e, &edge.data);
+                    assert_eq!(start_index, edge.source);
+                    assert_eq!(n, graph.node_data(edge.target));
+                }
+            }
+            counter += 1;
+        }
+        assert_eq!(counter, expected_outgoing.len());
+    }
+
+    #[test]
+    fn each_adjacent_from_a() {
+        let graph = create_graph();
+        test_adjacent_edges(&graph, NodeIndex(0), "A",
+                            [],
+                            [("AB", "B")]);
+    }
+
+    #[test]
+    fn each_adjacent_from_b() {
+        let graph = create_graph();
+        test_adjacent_edges(&graph, NodeIndex(1), "B",
+                            [("FB", "F"), ("AB", "A"),],
+                            [("BD", "D"), ("BC", "C"),]);
+    }
+
+    #[test]
+    fn each_adjacent_from_c() {
+        let graph = create_graph();
+        test_adjacent_edges(&graph, NodeIndex(2), "C",
+                            [("EC", "E"), ("BC", "B")],
+                            []);
+    }
+
+    #[test]
+    fn each_adjacent_from_d() {
+        let graph = create_graph();
+        test_adjacent_edges(&graph, NodeIndex(3), "D",
+                            [("BD", "B")],
+                            [("DE", "E")]);
+    }
+}
\ No newline at end of file
diff --git a/src/librustc/rustc.rs b/src/librustc/rustc.rs
index f4014180c64..9e53ef63054 100644
--- a/src/librustc/rustc.rs
+++ b/src/librustc/rustc.rs
@@ -74,6 +74,7 @@ pub mod middle {
     pub mod entry;
     pub mod effect;
     pub mod reachable;
+    pub mod graph;
 }
 
 pub mod front {