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IntervalPartition.h

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00001 //===- IntervalPartition.h - Interval partition Calculation -----*- C++ -*-===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file contains the declaration of the IntervalPartition class, which
00011 // calculates and represents the interval partition of a function, or a
00012 // preexisting interval partition.
00013 //
00014 // In this way, the interval partition may be used to reduce a flow graph down
00015 // to its degenerate single node interval partition (unless it is irreducible).
00016 //
00017 // TODO: The IntervalPartition class should take a bool parameter that tells
00018 // whether it should add the "tails" of an interval to an interval itself or if
00019 // they should be represented as distinct intervals.
00020 //
00021 //===----------------------------------------------------------------------===//
00022 
00023 #ifndef LLVM_INTERVAL_PARTITION_H
00024 #define LLVM_INTERVAL_PARTITION_H
00025 
00026 #include "llvm/Analysis/Interval.h"
00027 #include "llvm/Pass.h"
00028 
00029 namespace llvm {
00030 
00031 //===----------------------------------------------------------------------===//
00032 //
00033 // IntervalPartition - This class builds and holds an "interval partition" for
00034 // a function.  This partition divides the control flow graph into a set of
00035 // maximal intervals, as defined with the properties above.  Intuitively, a
00036 // BasicBlock is a (possibly nonexistent) loop with a "tail" of non looping
00037 // nodes following it.
00038 //
00039 class IntervalPartition : public FunctionPass {
00040   typedef std::map<BasicBlock*, Interval*> IntervalMapTy;
00041   IntervalMapTy IntervalMap;
00042 
00043   typedef std::vector<Interval*> IntervalListTy;
00044   Interval *RootInterval;
00045   std::vector<Interval*> Intervals;
00046 
00047 public:
00048   IntervalPartition() : RootInterval(0) {}
00049 
00050   // run - Calculate the interval partition for this function
00051   virtual bool runOnFunction(Function &F);
00052 
00053   // IntervalPartition ctor - Build a reduced interval partition from an
00054   // existing interval graph.  This takes an additional boolean parameter to
00055   // distinguish it from a copy constructor.  Always pass in false for now.
00056   //
00057   IntervalPartition(IntervalPartition &I, bool);
00058 
00059   // Destructor - Free memory
00060   ~IntervalPartition() { destroy(); }
00061 
00062   // print - Show contents in human readable format...
00063   virtual void print(std::ostream &O) const;
00064 
00065   // getRootInterval() - Return the root interval that contains the starting
00066   // block of the function.
00067   inline Interval *getRootInterval() { return RootInterval; }
00068 
00069   // isDegeneratePartition() - Returns true if the interval partition contains
00070   // a single interval, and thus cannot be simplified anymore.
00071   bool isDegeneratePartition() { return Intervals.size() == 1; }
00072 
00073   // TODO: isIrreducible - look for triangle graph.
00074 
00075   // getBlockInterval - Return the interval that a basic block exists in.
00076   inline Interval *getBlockInterval(BasicBlock *BB) {
00077     IntervalMapTy::iterator I = IntervalMap.find(BB);
00078     return I != IntervalMap.end() ? I->second : 0;
00079   }
00080 
00081   // getAnalysisUsage - Implement the Pass API
00082   virtual void getAnalysisUsage(AnalysisUsage &AU) const {
00083     AU.setPreservesAll();
00084   }
00085 
00086   // Interface to Intervals vector...
00087   const std::vector<Interval*> &getIntervals() const { return Intervals; }
00088 
00089 private:
00090   // destroy - Reset state back to before function was analyzed
00091   void destroy();
00092 
00093   // addIntervalToPartition - Add an interval to the internal list of intervals,
00094   // and then add mappings from all of the basic blocks in the interval to the
00095   // interval itself (in the IntervalMap).
00096   //
00097   void addIntervalToPartition(Interval *I);
00098 
00099   // updatePredecessors - Interval generation only sets the successor fields of
00100   // the interval data structures.  After interval generation is complete,
00101   // run through all of the intervals and propagate successor info as
00102   // predecessor info.
00103   //
00104   void updatePredecessors(Interval *Int);
00105 };
00106 
00107 } // End llvm namespace
00108 
00109 #endif