IVUsers.h revision 62c102360ad39e005c3c8c42fe85bfc9f2f23474 
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 ScalarEvolution;
28class SCEV;
29class IVUsers;
30class DataLayout;
31
32/// IVStrideUse - Keep track of one use of a strided induction variable.
33/// The Expr member keeps track of the expression, User is the actual user
34/// instruction of the operand, and 'OperandValToReplace' is the operand of
35/// the User that is the use.
36class IVStrideUse : public CallbackVH, public ilist_node<IVStrideUse> {
37  friend class IVUsers;
38public:
39  IVStrideUse(IVUsers *P, Instruction* U, Value *O)
40    : CallbackVH(U), Parent(P), OperandValToReplace(O) {
41  }
42
43  /// getUser - Return the user instruction for this use.
44  Instruction *getUser() const {
45    return cast<Instruction>(getValPtr());
46  }
47
48  /// setUser - Assign a new user instruction for this use.
49  void setUser(Instruction *NewUser) {
50    setValPtr(NewUser);
51  }
52
53  /// getOperandValToReplace - Return the Value of the operand in the user
54  /// instruction that this IVStrideUse is representing.
55  Value *getOperandValToReplace() const {
56    return OperandValToReplace;
57  }
58
59  /// setOperandValToReplace - Assign a new Value as the operand value
60  /// to replace.
61  void setOperandValToReplace(Value *Op) {
62    OperandValToReplace = Op;
63  }
64
65  /// getPostIncLoops - Return the set of loops for which the expression has
66  /// been adjusted to use post-inc mode.
67  const PostIncLoopSet &getPostIncLoops() const {
68    return PostIncLoops;
69  }
70
71  /// transformToPostInc - Transform the expression to post-inc form for the
72  /// given loop.
73  void transformToPostInc(const Loop *L);
74
75private:
76  /// Parent - a pointer to the IVUsers that owns this IVStrideUse.
77  IVUsers *Parent;
78
79  /// OperandValToReplace - The Value of the operand in the user instruction
80  /// that this IVStrideUse is representing.
81  WeakVH OperandValToReplace;
82
83  /// PostIncLoops - The set of loops for which Expr has been adjusted to
84  /// use post-inc mode. This corresponds with SCEVExpander's post-inc concept.
85  PostIncLoopSet PostIncLoops;
86
87  /// Deleted - Implementation of CallbackVH virtual function to
88  /// receive notification when the User is deleted.
89  virtual void deleted();
90};
91
92template<> struct ilist_traits<IVStrideUse>
93  : public ilist_default_traits<IVStrideUse> {
94  // createSentinel is used to get hold of a node that marks the end of
95  // the list...
96  // The sentinel is relative to this instance, so we use a non-static
97  // method.
98  IVStrideUse *createSentinel() const {
99    // since i(p)lists always publicly derive from the corresponding
100    // traits, placing a data member in this class will augment i(p)list.
101    // But since the NodeTy is expected to publicly derive from
102    // ilist_node<NodeTy>, there is a legal viable downcast from it
103    // to NodeTy. We use this trick to superpose i(p)list with a "ghostly"
104    // NodeTy, which becomes the sentinel. Dereferencing the sentinel is
105    // forbidden (save the ilist_node<NodeTy>) so no one will ever notice
106    // the superposition.
107    return static_cast<IVStrideUse*>(&Sentinel);
108  }
109  static void destroySentinel(IVStrideUse*) {}
110
111  IVStrideUse *provideInitialHead() const { return createSentinel(); }
112  IVStrideUse *ensureHead(IVStrideUse*) const { return createSentinel(); }
113  static void noteHead(IVStrideUse*, IVStrideUse*) {}
114
115private:
116  mutable ilist_node<IVStrideUse> Sentinel;
117};
118
119class IVUsers : public LoopPass {
120  friend class IVStrideUse;
121  Loop *L;
122  LoopInfo *LI;
123  DominatorTree *DT;
124  ScalarEvolution *SE;
125  DataLayout *TD;
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
138public:
139  static char ID; // Pass ID, replacement for typeid
140  IVUsers();
141
142  Loop *getLoop() const { return L; }
143
144  /// AddUsersIfInteresting - Inspect the specified Instruction.  If it is a
145  /// reducible SCEV, recursively add its users to the IVUsesByStride set and
146  /// return true.  Otherwise, return false.
147  bool 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  bool isIVUserOrOperand(Instruction *Inst) const {
169    return Processed.count(Inst);
170  }
171
172  void print(raw_ostream &OS, const Module* = 0) const;
173
174  /// dump - This method is used for debugging.
175  void dump() const;
176protected:
177  bool AddUsersImpl(Instruction *I, SmallPtrSet<Loop*,16> &SimpleLoopNests);
178};
179
180Pass *createIVUsersPass();
181
182}
183
184#endif
185