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