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
40class MachineLoop;
41extern template class LoopBase<MachineBasicBlock, MachineLoop>;
42
43class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> {
44public:
45  MachineLoop();
46
47  /// getTopBlock - Return the "top" block in the loop, which is the first
48  /// block in the linear layout, ignoring any parts of the loop not
49  /// contiguous with the part the contains the header.
50  MachineBasicBlock *getTopBlock();
51
52  /// getBottomBlock - Return the "bottom" block in the loop, which is the last
53  /// block in the linear layout, ignoring any parts of the loop not
54  /// contiguous with the part the contains the header.
55  MachineBasicBlock *getBottomBlock();
56
57  void dump() const;
58
59private:
60  friend class LoopInfoBase<MachineBasicBlock, MachineLoop>;
61  explicit MachineLoop(MachineBasicBlock *MBB)
62    : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {}
63};
64
65// Implementation in LoopInfoImpl.h
66extern template class LoopInfoBase<MachineBasicBlock, MachineLoop>;
67
68class MachineLoopInfo : public MachineFunctionPass {
69  LoopInfoBase<MachineBasicBlock, MachineLoop> LI;
70  friend class LoopBase<MachineBasicBlock, MachineLoop>;
71
72  void operator=(const MachineLoopInfo &) = delete;
73  MachineLoopInfo(const MachineLoopInfo &) = delete;
74
75public:
76  static char ID; // Pass identification, replacement for typeid
77
78  MachineLoopInfo() : MachineFunctionPass(ID) {
79    initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
80  }
81
82  LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
83
84  /// iterator/begin/end - The interface to the top-level loops in the current
85  /// function.
86  ///
87  typedef LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator iterator;
88  inline iterator begin() const { return LI.begin(); }
89  inline iterator end() const { return LI.end(); }
90  bool empty() const { return LI.empty(); }
91
92  /// getLoopFor - Return the inner most loop that BB lives in.  If a basic
93  /// block is in no loop (for example the entry node), null is returned.
94  ///
95  inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
96    return LI.getLoopFor(BB);
97  }
98
99  /// operator[] - same as getLoopFor...
100  ///
101  inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
102    return LI.getLoopFor(BB);
103  }
104
105  /// getLoopDepth - Return the loop nesting level of the specified block...
106  ///
107  inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
108    return LI.getLoopDepth(BB);
109  }
110
111  // isLoopHeader - True if the block is a loop header node
112  inline bool isLoopHeader(const MachineBasicBlock *BB) const {
113    return LI.isLoopHeader(BB);
114  }
115
116  /// runOnFunction - Calculate the natural loop information.
117  ///
118  bool runOnMachineFunction(MachineFunction &F) override;
119
120  void releaseMemory() override { LI.releaseMemory(); }
121
122  void getAnalysisUsage(AnalysisUsage &AU) const override;
123
124  /// removeLoop - This removes the specified top-level loop from this loop info
125  /// object.  The loop is not deleted, as it will presumably be inserted into
126  /// another loop.
127  inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
128
129  /// changeLoopFor - Change the top-level loop that contains BB to the
130  /// specified loop.  This should be used by transformations that restructure
131  /// the loop hierarchy tree.
132  inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
133    LI.changeLoopFor(BB, L);
134  }
135
136  /// changeTopLevelLoop - Replace the specified loop in the top-level loops
137  /// list with the indicated loop.
138  inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
139    LI.changeTopLevelLoop(OldLoop, NewLoop);
140  }
141
142  /// addTopLevelLoop - This adds the specified loop to the collection of
143  /// top-level loops.
144  inline void addTopLevelLoop(MachineLoop *New) {
145    LI.addTopLevelLoop(New);
146  }
147
148  /// removeBlock - This method completely removes BB from all data structures,
149  /// including all of the Loop objects it is nested in and our mapping from
150  /// MachineBasicBlocks to loops.
151  void removeBlock(MachineBasicBlock *BB) {
152    LI.removeBlock(BB);
153  }
154};
155
156
157// Allow clients to walk the list of nested loops...
158template <> struct GraphTraits<const MachineLoop*> {
159  typedef const MachineLoop NodeType;
160  typedef MachineLoopInfo::iterator ChildIteratorType;
161
162  static NodeType *getEntryNode(const MachineLoop *L) { return L; }
163  static inline ChildIteratorType child_begin(NodeType *N) {
164    return N->begin();
165  }
166  static inline ChildIteratorType child_end(NodeType *N) {
167    return N->end();
168  }
169};
170
171template <> struct GraphTraits<MachineLoop*> {
172  typedef MachineLoop NodeType;
173  typedef MachineLoopInfo::iterator ChildIteratorType;
174
175  static NodeType *getEntryNode(MachineLoop *L) { return L; }
176  static inline ChildIteratorType child_begin(NodeType *N) {
177    return N->begin();
178  }
179  static inline ChildIteratorType child_end(NodeType *N) {
180    return N->end();
181  }
182};
183
184} // End llvm namespace
185
186#endif
187