IntervalPartition.h revision adb4a40cb6ef2dba298e9dac5a905fcd2bee6e35 
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
30namespace 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, an
37// interval is a (possibly nonexistent) loop with a "tail" of non looping
38// nodes following it.
39//
40class 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
48public:
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
94private:
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