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      1 //===- IntervalPartition.h - Interval partition Calculation -----*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file contains the declaration of the IntervalPartition class, which
     11 // calculates and represents the interval partition of a function, or a
     12 // preexisting interval partition.
     13 //
     14 // In this way, the interval partition may be used to reduce a flow graph down
     15 // to its degenerate single node interval partition (unless it is irreducible).
     16 //
     17 // TODO: The IntervalPartition class should take a bool parameter that tells
     18 // whether it should add the "tails" of an interval to an interval itself or if
     19 // they should be represented as distinct intervals.
     20 //
     21 //===----------------------------------------------------------------------===//
     22 
     23 #ifndef LLVM_INTERVAL_PARTITION_H
     24 #define LLVM_INTERVAL_PARTITION_H
     25 
     26 #include "llvm/Analysis/Interval.h"
     27 #include "llvm/Pass.h"
     28 #include <map>
     29 
     30 namespace llvm {
     31 
     32 //===----------------------------------------------------------------------===//
     33 //
     34 // IntervalPartition - This class builds and holds an "interval partition" for
     35 // a function.  This partition divides the control flow graph into a set of
     36 // maximal intervals, as defined with the properties above.  Intuitively, a
     37 // BasicBlock is a (possibly nonexistent) loop with a "tail" of non looping
     38 // nodes following it.
     39 //
     40 class IntervalPartition : public FunctionPass {
     41   typedef std::map<BasicBlock*, Interval*> IntervalMapTy;
     42   IntervalMapTy IntervalMap;
     43 
     44   typedef std::vector<Interval*> IntervalListTy;
     45   Interval *RootInterval;
     46   std::vector<Interval*> Intervals;
     47 
     48 public:
     49   static char ID; // Pass identification, replacement for typeid
     50 
     51   IntervalPartition() : FunctionPass(ID), RootInterval(0) {
     52     initializeIntervalPartitionPass(*PassRegistry::getPassRegistry());
     53   }
     54 
     55   // run - Calculate the interval partition for this function
     56   virtual bool runOnFunction(Function &F);
     57 
     58   // IntervalPartition ctor - Build a reduced interval partition from an
     59   // existing interval graph.  This takes an additional boolean parameter to
     60   // distinguish it from a copy constructor.  Always pass in false for now.
     61   //
     62   IntervalPartition(IntervalPartition &I, bool);
     63 
     64   // print - Show contents in human readable format...
     65   virtual void print(raw_ostream &O, const Module* = 0) const;
     66 
     67   // getRootInterval() - Return the root interval that contains the starting
     68   // block of the function.
     69   inline Interval *getRootInterval() { return RootInterval; }
     70 
     71   // isDegeneratePartition() - Returns true if the interval partition contains
     72   // a single interval, and thus cannot be simplified anymore.
     73   bool isDegeneratePartition() { return Intervals.size() == 1; }
     74 
     75   // TODO: isIrreducible - look for triangle graph.
     76 
     77   // getBlockInterval - Return the interval that a basic block exists in.
     78   inline Interval *getBlockInterval(BasicBlock *BB) {
     79     IntervalMapTy::iterator I = IntervalMap.find(BB);
     80     return I != IntervalMap.end() ? I->second : 0;
     81   }
     82 
     83   // getAnalysisUsage - Implement the Pass API
     84   virtual void getAnalysisUsage(AnalysisUsage &AU) const {
     85     AU.setPreservesAll();
     86   }
     87 
     88   // Interface to Intervals vector...
     89   const std::vector<Interval*> &getIntervals() const { return Intervals; }
     90 
     91   // releaseMemory - Reset state back to before function was analyzed
     92   void releaseMemory();
     93 
     94 private:
     95   // addIntervalToPartition - Add an interval to the internal list of intervals,
     96   // and then add mappings from all of the basic blocks in the interval to the
     97   // interval itself (in the IntervalMap).
     98   //
     99   void addIntervalToPartition(Interval *I);
    100 
    101   // updatePredecessors - Interval generation only sets the successor fields of
    102   // the interval data structures.  After interval generation is complete,
    103   // run through all of the intervals and propagate successor info as
    104   // predecessor info.
    105   //
    106   void updatePredecessors(Interval *Int);
    107 };
    108 
    109 } // End llvm namespace
    110 
    111 #endif
    112