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diff --git a/include/llvm/Analysis/IntervalPartition.h b/include/llvm/Analysis/IntervalPartition.h
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+//===- IntervalPartition.h - Interval partition Calculation -----*- 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 IntervalPartition class, which
+// calculates and represents the interval partition of a function, or a
+// preexisting interval partition.
+//
+// In this way, the interval partition may be used to reduce a flow graph down
+// to its degenerate single node interval partition (unless it is irreducible).
+//
+// TODO: The IntervalPartition class should take a bool parameter that tells
+// whether it should add the "tails" of an interval to an interval itself or if
+// they should be represented as distinct intervals.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_INTERVALPARTITION_H
+#define LLVM_ANALYSIS_INTERVALPARTITION_H
+
+#include "llvm/Analysis/Interval.h"
+#include "llvm/Pass.h"
+#include <map>
+
+namespace llvm {
+
+//===----------------------------------------------------------------------===//
+//
+// IntervalPartition - This class builds and holds an "interval partition" for
+// a function.  This partition divides the control flow graph into a set of
+// maximal intervals, as defined with the properties above.  Intuitively, an
+// interval is a (possibly nonexistent) loop with a "tail" of non-looping
+// nodes following it.
+//
+class IntervalPartition : public FunctionPass {
+  typedef std::map<BasicBlock*, Interval*> IntervalMapTy;
+  IntervalMapTy IntervalMap;
+
+  typedef std::vector<Interval*> IntervalListTy;
+  Interval *RootInterval;
+  std::vector<Interval*> Intervals;
+
+public:
+  static char ID; // Pass identification, replacement for typeid
+
+  IntervalPartition() : FunctionPass(ID), RootInterval(nullptr) {
+    initializeIntervalPartitionPass(*PassRegistry::getPassRegistry());
+  }
+
+  // run - Calculate the interval partition for this function
+  bool runOnFunction(Function &F) override;
+
+  // IntervalPartition ctor - Build a reduced interval partition from an
+  // existing interval graph.  This takes an additional boolean parameter to
+  // distinguish it from a copy constructor.  Always pass in false for now.
+  //
+  IntervalPartition(IntervalPartition &I, bool);
+
+  // print - Show contents in human readable format...
+  void print(raw_ostream &O, const Module* = nullptr) const override;
+
+  // getRootInterval() - Return the root interval that contains the starting
+  // block of the function.
+  inline Interval *getRootInterval() { return RootInterval; }
+
+  // isDegeneratePartition() - Returns true if the interval partition contains
+  // a single interval, and thus cannot be simplified anymore.
+  bool isDegeneratePartition() { return Intervals.size() == 1; }
+
+  // TODO: isIrreducible - look for triangle graph.
+
+  // getBlockInterval - Return the interval that a basic block exists in.
+  inline Interval *getBlockInterval(BasicBlock *BB) {
+    IntervalMapTy::iterator I = IntervalMap.find(BB);
+    return I != IntervalMap.end() ? I->second : nullptr;
+  }
+
+  // getAnalysisUsage - Implement the Pass API
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesAll();
+  }
+
+  // Interface to Intervals vector...
+  const std::vector<Interval*> &getIntervals() const { return Intervals; }
+
+  // releaseMemory - Reset state back to before function was analyzed
+  void releaseMemory() override;
+
+private:
+  // addIntervalToPartition - Add an interval to the internal list of intervals,
+  // and then add mappings from all of the basic blocks in the interval to the
+  // interval itself (in the IntervalMap).
+  //
+  void addIntervalToPartition(Interval *I);
+
+  // updatePredecessors - Interval generation only sets the successor fields of
+  // the interval data structures.  After interval generation is complete,
+  // run through all of the intervals and propagate successor info as
+  // predecessor info.
+  //
+  void updatePredecessors(Interval *Int);
+};
+
+} // End llvm namespace
+
+#endif