MachineLoopInfo.h revision d68a07650cdb2e18f18f362ba533459aa10e01b6 
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
38// Provide overrides for Loop methods that don't make sense for machine loops.
39template<> inline
40PHINode *LoopBase<MachineBasicBlock>::getCanonicalInductionVariable() const {
41  assert(0 && "getCanonicalInductionVariable not supported for machine loops!");
42  return 0;
43}
44
45template<> inline Instruction*
46LoopBase<MachineBasicBlock>::getCanonicalInductionVariableIncrement() const {
47  assert(0 &&
48     "getCanonicalInductionVariableIncrement not supported for machine loops!");
49  return 0;
50}
51
52template<>
53inline bool LoopBase<MachineBasicBlock>::isLoopInvariant(Value *V) const {
54  assert(0 && "isLoopInvariant not supported for machine loops!");
55  return false;
56}
57
58template<>
59inline Value *LoopBase<MachineBasicBlock>::getTripCount() const {
60  assert(0 && "getTripCount not supported for machine loops!");
61  return 0;
62}
63
64template<>
65inline bool LoopBase<MachineBasicBlock>::isLCSSAForm() const {
66  assert(0 && "isLCSSAForm not supported for machine loops");
67  return false;
68}
69
70typedef LoopBase<MachineBasicBlock> MachineLoop;
71
72class MachineLoopInfo : public MachineFunctionPass {
73  LoopInfoBase<MachineBasicBlock>* LI;
74  friend class LoopBase<MachineBasicBlock>;
75
76  LoopInfoBase<MachineBasicBlock>& getBase() { return *LI; }
77public:
78  static char ID; // Pass identification, replacement for typeid
79
80  MachineLoopInfo() : MachineFunctionPass(intptr_t(&ID)) {
81    LI = new LoopInfoBase<MachineBasicBlock>();
82  }
83
84  ~MachineLoopInfo() { delete LI; }
85
86  /// iterator/begin/end - The interface to the top-level loops in the current
87  /// function.
88  ///
89  typedef std::vector<MachineLoop*>::const_iterator iterator;
90  inline iterator begin() const { return LI->begin(); }
91  inline iterator end() const { return LI->end(); }
92  bool empty() const { return LI->empty(); }
93
94  /// getLoopFor - Return the inner most loop that BB lives in.  If a basic
95  /// block is in no loop (for example the entry node), null is returned.
96  ///
97  inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
98    return LI->getLoopFor(BB);
99  }
100
101  /// operator[] - same as getLoopFor...
102  ///
103  inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
104    return LI->getLoopFor(BB);
105  }
106
107  /// getLoopDepth - Return the loop nesting level of the specified block...
108  ///
109  inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
110    return LI->getLoopDepth(BB);
111  }
112
113  // isLoopHeader - True if the block is a loop header node
114  inline bool isLoopHeader(MachineBasicBlock *BB) const {
115    return LI->isLoopHeader(BB);
116  }
117
118  /// runOnFunction - Calculate the natural loop information.
119  ///
120  virtual bool runOnMachineFunction(MachineFunction &F);
121
122  virtual void releaseMemory() { LI->releaseMemory(); }
123
124  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
125
126  /// removeLoop - This removes the specified top-level loop from this loop info
127  /// object.  The loop is not deleted, as it will presumably be inserted into
128  /// another loop.
129  inline MachineLoop *removeLoop(iterator I) { return LI->removeLoop(I); }
130
131  /// changeLoopFor - Change the top-level loop that contains BB to the
132  /// specified loop.  This should be used by transformations that restructure
133  /// the loop hierarchy tree.
134  inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
135    LI->changeLoopFor(BB, L);
136  }
137
138  /// changeTopLevelLoop - Replace the specified loop in the top-level loops
139  /// list with the indicated loop.
140  inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
141    LI->changeTopLevelLoop(OldLoop, NewLoop);
142  }
143
144  /// addTopLevelLoop - This adds the specified loop to the collection of
145  /// top-level loops.
146  inline void addTopLevelLoop(MachineLoop *New) {
147    LI->addTopLevelLoop(New);
148  }
149
150  /// removeBlock - This method completely removes BB from all data structures,
151  /// including all of the Loop objects it is nested in and our mapping from
152  /// MachineBasicBlocks to loops.
153  void removeBlock(MachineBasicBlock *BB) {
154    LI->removeBlock(BB);
155  }
156};
157
158
159// Allow clients to walk the list of nested loops...
160template <> struct GraphTraits<const MachineLoop*> {
161  typedef const MachineLoop NodeType;
162  typedef std::vector<MachineLoop*>::const_iterator ChildIteratorType;
163
164  static NodeType *getEntryNode(const MachineLoop *L) { return L; }
165  static inline ChildIteratorType child_begin(NodeType *N) {
166    return N->begin();
167  }
168  static inline ChildIteratorType child_end(NodeType *N) {
169    return N->end();
170  }
171};
172
173template <> struct GraphTraits<MachineLoop*> {
174  typedef MachineLoop NodeType;
175  typedef std::vector<MachineLoop*>::const_iterator ChildIteratorType;
176
177  static NodeType *getEntryNode(MachineLoop *L) { return L; }
178  static inline ChildIteratorType child_begin(NodeType *N) {
179    return N->begin();
180  }
181  static inline ChildIteratorType child_end(NodeType *N) {
182    return N->end();
183  }
184};
185
186} // End llvm namespace
187
188#endif
189