MachineLoopInfo.h revision 218893 
1//===- llvm/CodeGen/MachineLoopInfo.h - Natural Loop Calculator -*- 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 defines the MachineLoopInfo class that is used to identify natural
11// loops and determine the loop depth of various nodes of the CFG.  Note that
12// natural loops may actually be several loops that share the same header node.
13//
14// This analysis calculates the nesting structure of loops in a function.  For
15// each natural loop identified, this analysis identifies natural loops
16// contained entirely within the loop and the basic blocks the make up the loop.
17//
18// It can calculate on the fly various bits of information, for example:
19//
20//  * whether there is a preheader for the loop
21//  * the number of back edges to the header
22//  * whether or not a particular block branches out of the loop
23//  * the successor blocks of the loop
24//  * the loop depth
25//  * the trip count
26//  * etc...
27//
28//===----------------------------------------------------------------------===//
29
30#ifndef LLVM_CODEGEN_MACHINE_LOOP_INFO_H
31#define LLVM_CODEGEN_MACHINE_LOOP_INFO_H
32
33#include "llvm/CodeGen/MachineFunctionPass.h"
34#include "llvm/Analysis/LoopInfo.h"
35
36namespace llvm {
37
38class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> {
39public:
40  MachineLoop();
41
42  /// getTopBlock - Return the "top" block in the loop, which is the first
43  /// block in the linear layout, ignoring any parts of the loop not
44  /// contiguous with the part the contains the header.
45  MachineBasicBlock *getTopBlock();
46
47  /// getBottomBlock - Return the "bottom" block in the loop, which is the last
48  /// block in the linear layout, ignoring any parts of the loop not
49  /// contiguous with the part the contains the header.
50  MachineBasicBlock *getBottomBlock();
51
52  void dump() const;
53
54private:
55  friend class LoopInfoBase<MachineBasicBlock, MachineLoop>;
56  explicit MachineLoop(MachineBasicBlock *MBB)
57    : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {}
58};
59
60class MachineLoopInfo : public MachineFunctionPass {
61  LoopInfoBase<MachineBasicBlock, MachineLoop> LI;
62  friend class LoopBase<MachineBasicBlock, MachineLoop>;
63
64  void operator=(const MachineLoopInfo &);  // do not implement
65  MachineLoopInfo(const MachineLoopInfo &); // do not implement
66
67public:
68  static char ID; // Pass identification, replacement for typeid
69
70  MachineLoopInfo() : MachineFunctionPass(ID) {
71    initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
72  }
73
74  LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
75
76  /// iterator/begin/end - The interface to the top-level loops in the current
77  /// function.
78  ///
79  typedef LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator iterator;
80  inline iterator begin() const { return LI.begin(); }
81  inline iterator end() const { return LI.end(); }
82  bool empty() const { return LI.empty(); }
83
84  /// getLoopFor - Return the inner most loop that BB lives in.  If a basic
85  /// block is in no loop (for example the entry node), null is returned.
86  ///
87  inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
88    return LI.getLoopFor(BB);
89  }
90
91  /// operator[] - same as getLoopFor...
92  ///
93  inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
94    return LI.getLoopFor(BB);
95  }
96
97  /// getLoopDepth - Return the loop nesting level of the specified block...
98  ///
99  inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
100    return LI.getLoopDepth(BB);
101  }
102
103  // isLoopHeader - True if the block is a loop header node
104  inline bool isLoopHeader(MachineBasicBlock *BB) const {
105    return LI.isLoopHeader(BB);
106  }
107
108  /// runOnFunction - Calculate the natural loop information.
109  ///
110  virtual bool runOnMachineFunction(MachineFunction &F);
111
112  virtual void releaseMemory() { LI.releaseMemory(); }
113
114  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
115
116  /// removeLoop - This removes the specified top-level loop from this loop info
117  /// object.  The loop is not deleted, as it will presumably be inserted into
118  /// another loop.
119  inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
120
121  /// changeLoopFor - Change the top-level loop that contains BB to the
122  /// specified loop.  This should be used by transformations that restructure
123  /// the loop hierarchy tree.
124  inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
125    LI.changeLoopFor(BB, L);
126  }
127
128  /// changeTopLevelLoop - Replace the specified loop in the top-level loops
129  /// list with the indicated loop.
130  inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
131    LI.changeTopLevelLoop(OldLoop, NewLoop);
132  }
133
134  /// addTopLevelLoop - This adds the specified loop to the collection of
135  /// top-level loops.
136  inline void addTopLevelLoop(MachineLoop *New) {
137    LI.addTopLevelLoop(New);
138  }
139
140  /// removeBlock - This method completely removes BB from all data structures,
141  /// including all of the Loop objects it is nested in and our mapping from
142  /// MachineBasicBlocks to loops.
143  void removeBlock(MachineBasicBlock *BB) {
144    LI.removeBlock(BB);
145  }
146};
147
148
149// Allow clients to walk the list of nested loops...
150template <> struct GraphTraits<const MachineLoop*> {
151  typedef const MachineLoop NodeType;
152  typedef MachineLoopInfo::iterator ChildIteratorType;
153
154  static NodeType *getEntryNode(const MachineLoop *L) { return L; }
155  static inline ChildIteratorType child_begin(NodeType *N) {
156    return N->begin();
157  }
158  static inline ChildIteratorType child_end(NodeType *N) {
159    return N->end();
160  }
161};
162
163template <> struct GraphTraits<MachineLoop*> {
164  typedef MachineLoop NodeType;
165  typedef MachineLoopInfo::iterator ChildIteratorType;
166
167  static NodeType *getEntryNode(MachineLoop *L) { return L; }
168  static inline ChildIteratorType child_begin(NodeType *N) {
169    return N->begin();
170  }
171  static inline ChildIteratorType child_end(NodeType *N) {
172    return N->end();
173  }
174};
175
176} // End llvm namespace
177
178#endif
179