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_MACHINELOOPINFO_H
31#define LLVM_CODEGEN_MACHINELOOPINFO_H
32
33#include "llvm/Analysis/LoopInfo.h"
34#include "llvm/CodeGen/MachineBasicBlock.h"
35#include "llvm/CodeGen/MachineFunctionPass.h"
36
37namespace llvm {
38
39// Implementation in LoopInfoImpl.h
40#ifdef __GNUC__
41class MachineLoop;
42__extension__ extern template class LoopBase<MachineBasicBlock, MachineLoop>;
43#endif
44
45class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> {
46public:
47  MachineLoop();
48
49  /// getTopBlock - Return the "top" block in the loop, which is the first
50  /// block in the linear layout, ignoring any parts of the loop not
51  /// contiguous with the part the contains the header.
52  MachineBasicBlock *getTopBlock();
53
54  /// getBottomBlock - Return the "bottom" block in the loop, which is the last
55  /// block in the linear layout, ignoring any parts of the loop not
56  /// contiguous with the part the contains the header.
57  MachineBasicBlock *getBottomBlock();
58
59  void dump() const;
60
61private:
62  friend class LoopInfoBase<MachineBasicBlock, MachineLoop>;
63  explicit MachineLoop(MachineBasicBlock *MBB)
64    : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {}
65};
66
67// Implementation in LoopInfoImpl.h
68#ifdef __GNUC__
69__extension__ extern template
70class LoopInfoBase<MachineBasicBlock, MachineLoop>;
71#endif
72
73class MachineLoopInfo : public MachineFunctionPass {
74  LoopInfoBase<MachineBasicBlock, MachineLoop> LI;
75  friend class LoopBase<MachineBasicBlock, MachineLoop>;
76
77  void operator=(const MachineLoopInfo &) LLVM_DELETED_FUNCTION;
78  MachineLoopInfo(const MachineLoopInfo &) LLVM_DELETED_FUNCTION;
79
80public:
81  static char ID; // Pass identification, replacement for typeid
82
83  MachineLoopInfo() : MachineFunctionPass(ID) {
84    initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
85  }
86
87  LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
88
89  /// iterator/begin/end - The interface to the top-level loops in the current
90  /// function.
91  ///
92  typedef LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator iterator;
93  inline iterator begin() const { return LI.begin(); }
94  inline iterator end() const { return LI.end(); }
95  bool empty() const { return LI.empty(); }
96
97  /// getLoopFor - Return the inner most loop that BB lives in.  If a basic
98  /// block is in no loop (for example the entry node), null is returned.
99  ///
100  inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
101    return LI.getLoopFor(BB);
102  }
103
104  /// operator[] - same as getLoopFor...
105  ///
106  inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
107    return LI.getLoopFor(BB);
108  }
109
110  /// getLoopDepth - Return the loop nesting level of the specified block...
111  ///
112  inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
113    return LI.getLoopDepth(BB);
114  }
115
116  // isLoopHeader - True if the block is a loop header node
117  inline bool isLoopHeader(MachineBasicBlock *BB) const {
118    return LI.isLoopHeader(BB);
119  }
120
121  /// runOnFunction - Calculate the natural loop information.
122  ///
123  bool runOnMachineFunction(MachineFunction &F) override;
124
125  void releaseMemory() override { LI.releaseMemory(); }
126
127  void getAnalysisUsage(AnalysisUsage &AU) const override;
128
129  /// removeLoop - This removes the specified top-level loop from this loop info
130  /// object.  The loop is not deleted, as it will presumably be inserted into
131  /// another loop.
132  inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
133
134  /// changeLoopFor - Change the top-level loop that contains BB to the
135  /// specified loop.  This should be used by transformations that restructure
136  /// the loop hierarchy tree.
137  inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
138    LI.changeLoopFor(BB, L);
139  }
140
141  /// changeTopLevelLoop - Replace the specified loop in the top-level loops
142  /// list with the indicated loop.
143  inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
144    LI.changeTopLevelLoop(OldLoop, NewLoop);
145  }
146
147  /// addTopLevelLoop - This adds the specified loop to the collection of
148  /// top-level loops.
149  inline void addTopLevelLoop(MachineLoop *New) {
150    LI.addTopLevelLoop(New);
151  }
152
153  /// removeBlock - This method completely removes BB from all data structures,
154  /// including all of the Loop objects it is nested in and our mapping from
155  /// MachineBasicBlocks to loops.
156  void removeBlock(MachineBasicBlock *BB) {
157    LI.removeBlock(BB);
158  }
159};
160
161
162// Allow clients to walk the list of nested loops...
163template <> struct GraphTraits<const MachineLoop*> {
164  typedef const MachineLoop NodeType;
165  typedef MachineLoopInfo::iterator ChildIteratorType;
166
167  static NodeType *getEntryNode(const 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
176template <> struct GraphTraits<MachineLoop*> {
177  typedef MachineLoop NodeType;
178  typedef MachineLoopInfo::iterator ChildIteratorType;
179
180  static NodeType *getEntryNode(MachineLoop *L) { return L; }
181  static inline ChildIteratorType child_begin(NodeType *N) {
182    return N->begin();
183  }
184  static inline ChildIteratorType child_end(NodeType *N) {
185    return N->end();
186  }
187};
188
189} // End llvm namespace
190
191#endif
192