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diff --git a/include/llvm/Analysis/Interval.h b/include/llvm/Analysis/Interval.h
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+//===- llvm/Analysis/Interval.h - Interval Class Declaration ----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the declaration of the Interval class, which
+// represents a set of CFG nodes and is a portion of an interval partition.
+//
+// Intervals have some interesting and useful properties, including the
+// following:
+//    1. The header node of an interval dominates all of the elements of the
+//       interval
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_INTERVAL_H
+#define LLVM_INTERVAL_H
+
+#include "llvm/ADT/GraphTraits.h"
+#include <vector>
+#include <iosfwd>
+
+namespace llvm {
+
+class BasicBlock;
+
+//===----------------------------------------------------------------------===//
+//
+/// Interval Class - An Interval is a set of nodes defined such that every node
+/// in the interval has all of its predecessors in the interval (except for the
+/// header)
+///
+class Interval {
+  /// HeaderNode - The header BasicBlock, which dominates all BasicBlocks in this
+  /// interval.  Also, any loops in this interval must go through the HeaderNode.
+  ///
+  BasicBlock *HeaderNode;
+public:
+  typedef std::vector<BasicBlock*>::iterator succ_iterator;
+  typedef std::vector<BasicBlock*>::iterator pred_iterator;
+  typedef std::vector<BasicBlock*>::iterator node_iterator;
+
+  inline Interval(BasicBlock *Header) : HeaderNode(Header) {
+    Nodes.push_back(Header);
+  }
+
+  inline Interval(const Interval &I) // copy ctor
+    : HeaderNode(I.HeaderNode), Nodes(I.Nodes), Successors(I.Successors) {}
+
+  inline BasicBlock *getHeaderNode() const { return HeaderNode; }
+
+  /// Nodes - The basic blocks in this interval.
+  ///
+  std::vector<BasicBlock*> Nodes;
+
+  /// Successors - List of BasicBlocks that are reachable directly from nodes in
+  /// this interval, but are not in the interval themselves.
+  /// These nodes necessarily must be header nodes for other intervals.
+  ///
+  std::vector<BasicBlock*> Successors;
+
+  /// Predecessors - List of BasicBlocks that have this Interval's header block
+  /// as one of their successors.
+  ///
+  std::vector<BasicBlock*> Predecessors;
+
+  /// contains - Find out if a basic block is in this interval
+  inline bool contains(BasicBlock *BB) const {
+    for (unsigned i = 0; i < Nodes.size(); ++i)
+      if (Nodes[i] == BB) return true;
+    return false;
+    // I don't want the dependency on <algorithm>
+    //return find(Nodes.begin(), Nodes.end(), BB) != Nodes.end();
+  }
+
+  /// isSuccessor - find out if a basic block is a successor of this Interval
+  inline bool isSuccessor(BasicBlock *BB) const {
+    for (unsigned i = 0; i < Successors.size(); ++i)
+      if (Successors[i] == BB) return true;
+    return false;
+    // I don't want the dependency on <algorithm>
+    //return find(Successors.begin(), Successors.end(), BB) != Successors.end();
+  }
+
+  /// Equality operator.  It is only valid to compare two intervals from the
+  /// same partition, because of this, all we have to check is the header node
+  /// for equality.
+  ///
+  inline bool operator==(const Interval &I) const {
+    return HeaderNode == I.HeaderNode;
+  }
+
+  /// isLoop - Find out if there is a back edge in this interval...
+  bool isLoop() const;
+
+  /// print - Show contents in human readable format...
+  void print(std::ostream &O) const;
+  void print(std::ostream *O) const { if (O) print(*O); }
+};
+
+/// succ_begin/succ_end - define methods so that Intervals may be used
+/// just like BasicBlocks can with the succ_* functions, and *::succ_iterator.
+///
+inline Interval::succ_iterator succ_begin(Interval *I) {
+  return I->Successors.begin();
+}
+inline Interval::succ_iterator succ_end(Interval *I)   {
+  return I->Successors.end();
+}
+
+/// pred_begin/pred_end - define methods so that Intervals may be used
+/// just like BasicBlocks can with the pred_* functions, and *::pred_iterator.
+///
+inline Interval::pred_iterator pred_begin(Interval *I) {
+  return I->Predecessors.begin();
+}
+inline Interval::pred_iterator pred_end(Interval *I)   {
+  return I->Predecessors.end();
+}
+
+template <> struct GraphTraits<Interval*> {
+  typedef Interval NodeType;
+  typedef Interval::succ_iterator ChildIteratorType;
+
+  static NodeType *getEntryNode(Interval *I) { return I; }
+
+  /// nodes_iterator/begin/end - Allow iteration over all nodes in the graph
+  static inline ChildIteratorType child_begin(NodeType *N) {
+    return succ_begin(N);
+  }
+  static inline ChildIteratorType child_end(NodeType *N) {
+    return succ_end(N);
+  }
+};
+
+template <> struct GraphTraits<Inverse<Interval*> > {
+  typedef Interval NodeType;
+  typedef Interval::pred_iterator ChildIteratorType;
+  static NodeType *getEntryNode(Inverse<Interval *> G) { return G.Graph; }
+  static inline ChildIteratorType child_begin(NodeType *N) {
+    return pred_begin(N);
+  }
+  static inline ChildIteratorType child_end(NodeType *N) {
+    return pred_end(N);
+  }
+};
+
+} // End llvm namespace
+
+#endif