IVUsers.h revision eaa40ff74e41176250bd6b50116ab03b0c596d5e 
1//===- llvm/Analysis/IVUsers.h - Induction Variable Users -------*- 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 implements bookkeeping for "interesting" users of expressions
11// computed from induction variables.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_ANALYSIS_IVUSERS_H
16#define LLVM_ANALYSIS_IVUSERS_H
17
18#include "llvm/Analysis/LoopPass.h"
19#include "llvm/Analysis/ScalarEvolutionNormalization.h"
20#include "llvm/Support/ValueHandle.h"
21
22namespace llvm {
23
24class DominatorTree;
25class Instruction;
26class Value;
27class IVUsers;
28class ScalarEvolution;
29class SCEV;
30class SCEVAddRecExpr;
31class IVUsers;
32
33/// IVStrideUse - Keep track of one use of a strided induction variable.
34/// The Expr member keeps track of the expression, User is the actual user
35/// instruction of the operand, and 'OperandValToReplace' is the operand of
36/// the User that is the use.
37class IVStrideUse : public CallbackVH, public ilist_node<IVStrideUse> {
38  friend class IVUsers;
39public:
40  IVStrideUse(IVUsers *P, Instruction* U, Value *O)
41    : CallbackVH(U), Parent(P), OperandValToReplace(O) {
42  }
43
44  /// getUser - Return the user instruction for this use.
45  Instruction *getUser() const {
46    return cast<Instruction>(getValPtr());
47  }
48
49  /// setUser - Assign a new user instruction for this use.
50  void setUser(Instruction *NewUser) {
51    setValPtr(NewUser);
52  }
53
54  /// getOperandValToReplace - Return the Value of the operand in the user
55  /// instruction that this IVStrideUse is representing.
56  Value *getOperandValToReplace() const {
57    return OperandValToReplace;
58  }
59
60  /// setOperandValToReplace - Assign a new Value as the operand value
61  /// to replace.
62  void setOperandValToReplace(Value *Op) {
63    OperandValToReplace = Op;
64  }
65
66  /// getPostIncLoops - Return the set of loops for which the expression has
67  /// been adjusted to use post-inc mode.
68  const PostIncLoopSet &getPostIncLoops() const {
69    return PostIncLoops;
70  }
71
72  /// transformToPostInc - Transform the expression to post-inc form for the
73  /// given loop.
74  void transformToPostInc(const Loop *L);
75
76private:
77  /// Parent - a pointer to the IVUsers that owns this IVStrideUse.
78  IVUsers *Parent;
79
80  /// OperandValToReplace - The Value of the operand in the user instruction
81  /// that this IVStrideUse is representing.
82  WeakVH OperandValToReplace;
83
84  /// PostIncLoops - The set of loops for which Expr has been adjusted to
85  /// use post-inc mode. This corresponds with SCEVExpander's post-inc concept.
86  PostIncLoopSet PostIncLoops;
87
88  /// Deleted - Implementation of CallbackVH virtual function to
89  /// receive notification when the User is deleted.
90  virtual void deleted();
91};
92
93template<> struct ilist_traits<IVStrideUse>
94  : public ilist_default_traits<IVStrideUse> {
95  // createSentinel is used to get hold of a node that marks the end of
96  // the list...
97  // The sentinel is relative to this instance, so we use a non-static
98  // method.
99  IVStrideUse *createSentinel() const {
100    // since i(p)lists always publicly derive from the corresponding
101    // traits, placing a data member in this class will augment i(p)list.
102    // But since the NodeTy is expected to publicly derive from
103    // ilist_node<NodeTy>, there is a legal viable downcast from it
104    // to NodeTy. We use this trick to superpose i(p)list with a "ghostly"
105    // NodeTy, which becomes the sentinel. Dereferencing the sentinel is
106    // forbidden (save the ilist_node<NodeTy>) so no one will ever notice
107    // the superposition.
108    return static_cast<IVStrideUse*>(&Sentinel);
109  }
110  static void destroySentinel(IVStrideUse*) {}
111
112  IVStrideUse *provideInitialHead() const { return createSentinel(); }
113  IVStrideUse *ensureHead(IVStrideUse*) const { return createSentinel(); }
114  static void noteHead(IVStrideUse*, IVStrideUse*) {}
115
116private:
117  mutable ilist_node<IVStrideUse> Sentinel;
118};
119
120class IVUsers : public LoopPass {
121  friend class IVStrideUse;
122  Loop *L;
123  LoopInfo *LI;
124  DominatorTree *DT;
125  ScalarEvolution *SE;
126  SmallPtrSet<Instruction *, 16> Processed;
127
128  /// IVUses - A list of all tracked IV uses of induction variable expressions
129  /// we are interested in.
130  ilist<IVStrideUse> IVUses;
131
132  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
133
134  virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
135
136  virtual void releaseMemory();
137
138  const SCEVAddRecExpr *findInterestingAddRec(const SCEV *S) const;
139  bool isInterestingUser(const Instruction *User) const;
140
141public:
142  static char ID; // Pass ID, replacement for typeid
143  IVUsers();
144
145  /// AddUsersIfInteresting - Inspect the def-use graph starting at the
146  /// specified Instruction and add IVUsers.
147  void AddUsersIfInteresting(Instruction *I);
148
149  IVStrideUse &AddUser(Instruction *User, Value *Operand);
150
151  /// getReplacementExpr - Return a SCEV expression which computes the
152  /// value of the OperandValToReplace of the given IVStrideUse.
153  const SCEV *getReplacementExpr(const IVStrideUse &IU) const;
154
155  /// getExpr - Return the expression for the use.
156  const SCEV *getExpr(const IVStrideUse &IU) const;
157
158  const SCEV *getStride(const IVStrideUse &IU, const Loop *L) const;
159
160  typedef ilist<IVStrideUse>::iterator iterator;
161  typedef ilist<IVStrideUse>::const_iterator const_iterator;
162  iterator begin() { return IVUses.begin(); }
163  iterator end()   { return IVUses.end(); }
164  const_iterator begin() const { return IVUses.begin(); }
165  const_iterator end() const   { return IVUses.end(); }
166  bool empty() const { return IVUses.empty(); }
167
168  void print(raw_ostream &OS, const Module* = 0) const;
169
170  /// dump - This method is used for debugging.
171  void dump() const;
172};
173
174Pass *createIVUsersPass();
175
176}
177
178#endif
179