IntervalPartition.h revision 90c579de5a383cee278acc3f7e7b9d0a656e6a35 
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, a
37// BasicBlock 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
53  // run - Calculate the interval partition for this function
54  virtual bool runOnFunction(Function &F);
55
56  // IntervalPartition ctor - Build a reduced interval partition from an
57  // existing interval graph.  This takes an additional boolean parameter to
58  // distinguish it from a copy constructor.  Always pass in false for now.
59  //
60  IntervalPartition(IntervalPartition &I, bool);
61
62  // print - Show contents in human readable format...
63  virtual void print(raw_ostream &O, const Module* = 0) const;
64
65  // getRootInterval() - Return the root interval that contains the starting
66  // block of the function.
67  inline Interval *getRootInterval() { return RootInterval; }
68
69  // isDegeneratePartition() - Returns true if the interval partition contains
70  // a single interval, and thus cannot be simplified anymore.
71  bool isDegeneratePartition() { return Intervals.size() == 1; }
72
73  // TODO: isIrreducible - look for triangle graph.
74
75  // getBlockInterval - Return the interval that a basic block exists in.
76  inline Interval *getBlockInterval(BasicBlock *BB) {
77    IntervalMapTy::iterator I = IntervalMap.find(BB);
78    return I != IntervalMap.end() ? I->second : 0;
79  }
80
81  // getAnalysisUsage - Implement the Pass API
82  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
83    AU.setPreservesAll();
84  }
85
86  // Interface to Intervals vector...
87  const std::vector<Interval*> &getIntervals() const { return Intervals; }
88
89  // releaseMemory - Reset state back to before function was analyzed
90  void releaseMemory();
91
92private:
93  // addIntervalToPartition - Add an interval to the internal list of intervals,
94  // and then add mappings from all of the basic blocks in the interval to the
95  // interval itself (in the IntervalMap).
96  //
97  void addIntervalToPartition(Interval *I);
98
99  // updatePredecessors - Interval generation only sets the successor fields of
100  // the interval data structures.  After interval generation is complete,
101  // run through all of the intervals and propagate successor info as
102  // predecessor info.
103  //
104  void updatePredecessors(Interval *Int);
105};
106
107} // End llvm namespace
108
109#endif
110