IVUsers.h revision f85092c25525f75eef6982ffa40c9b48b87da987 
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 IVUsers;
31class TargetData;
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, Value *PN)
41    : CallbackVH(U), Parent(P), OperandValToReplace(O), Phi(PN) {
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  /// getPhi - Return the phi node that represents this IV.
55  PHINode *getPhi() const {
56    return cast<PHINode>(Phi);
57  }
58
59  /// getOperandValToReplace - Return the Value of the operand in the user
60  /// instruction that this IVStrideUse is representing.
61  Value *getOperandValToReplace() const {
62    return OperandValToReplace;
63  }
64
65  /// setOperandValToReplace - Assign a new Value as the operand value
66  /// to replace.
67  void setOperandValToReplace(Value *Op) {
68    OperandValToReplace = Op;
69  }
70
71  /// getPostIncLoops - Return the set of loops for which the expression has
72  /// been adjusted to use post-inc mode.
73  const PostIncLoopSet &getPostIncLoops() const {
74    return PostIncLoops;
75  }
76
77  /// transformToPostInc - Transform the expression to post-inc form for the
78  /// given loop.
79  void transformToPostInc(const Loop *L);
80
81private:
82  /// Parent - a pointer to the IVUsers that owns this IVStrideUse.
83  IVUsers *Parent;
84
85  /// OperandValToReplace - The Value of the operand in the user instruction
86  /// that this IVStrideUse is representing.
87  WeakVH OperandValToReplace;
88
89  /// Phi - The loop header phi that represents this IV.
90  WeakVH Phi;
91
92  /// PostIncLoops - The set of loops for which Expr has been adjusted to
93  /// use post-inc mode. This corresponds with SCEVExpander's post-inc concept.
94  PostIncLoopSet PostIncLoops;
95
96  /// Deleted - Implementation of CallbackVH virtual function to
97  /// receive notification when the User is deleted.
98  virtual void deleted();
99};
100
101template<> struct ilist_traits<IVStrideUse>
102  : public ilist_default_traits<IVStrideUse> {
103  // createSentinel is used to get hold of a node that marks the end of
104  // the list...
105  // The sentinel is relative to this instance, so we use a non-static
106  // method.
107  IVStrideUse *createSentinel() const {
108    // since i(p)lists always publicly derive from the corresponding
109    // traits, placing a data member in this class will augment i(p)list.
110    // But since the NodeTy is expected to publicly derive from
111    // ilist_node<NodeTy>, there is a legal viable downcast from it
112    // to NodeTy. We use this trick to superpose i(p)list with a "ghostly"
113    // NodeTy, which becomes the sentinel. Dereferencing the sentinel is
114    // forbidden (save the ilist_node<NodeTy>) so no one will ever notice
115    // the superposition.
116    return static_cast<IVStrideUse*>(&Sentinel);
117  }
118  static void destroySentinel(IVStrideUse*) {}
119
120  IVStrideUse *provideInitialHead() const { return createSentinel(); }
121  IVStrideUse *ensureHead(IVStrideUse*) const { return createSentinel(); }
122  static void noteHead(IVStrideUse*, IVStrideUse*) {}
123
124private:
125  mutable ilist_node<IVStrideUse> Sentinel;
126};
127
128class IVUsers : public LoopPass {
129  friend class IVStrideUse;
130  Loop *L;
131  LoopInfo *LI;
132  DominatorTree *DT;
133  ScalarEvolution *SE;
134  TargetData *TD;
135  SmallPtrSet<Instruction*,16> Processed;
136
137  /// IVUses - A list of all tracked IV uses of induction variable expressions
138  /// we are interested in.
139  ilist<IVStrideUse> IVUses;
140
141  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
142
143  virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
144
145  virtual void releaseMemory();
146
147public:
148  static char ID; // Pass ID, replacement for typeid
149  IVUsers();
150
151  /// AddUsersIfInteresting - Inspect the specified Instruction.  If it is a
152  /// reducible SCEV, recursively add its users to the IVUsesByStride set and
153  /// return true.  Otherwise, return false.
154  bool AddUsersIfInteresting(Instruction *I, PHINode *Phi);
155
156  IVStrideUse &AddUser(Instruction *User, Value *Operand, PHINode *Phi);
157
158  /// getReplacementExpr - Return a SCEV expression which computes the
159  /// value of the OperandValToReplace of the given IVStrideUse.
160  const SCEV *getReplacementExpr(const IVStrideUse &IU) const;
161
162  /// getExpr - Return the expression for the use.
163  const SCEV *getExpr(const IVStrideUse &IU) const;
164
165  const SCEV *getStride(const IVStrideUse &IU, const Loop *L) const;
166
167  typedef ilist<IVStrideUse>::iterator iterator;
168  typedef ilist<IVStrideUse>::const_iterator const_iterator;
169  iterator begin() { return IVUses.begin(); }
170  iterator end()   { return IVUses.end(); }
171  const_iterator begin() const { return IVUses.begin(); }
172  const_iterator end() const   { return IVUses.end(); }
173  bool empty() const { return IVUses.empty(); }
174
175  void print(raw_ostream &OS, const Module* = 0) const;
176
177  /// dump - This method is used for debugging.
178  void dump() const;
179};
180
181Pass *createIVUsersPass();
182
183}
184
185#endif
186