IVUsers.h revision 448db1cdef5872713ef77beffacf502ae3450cd7 
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;
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, const SCEV *E,
40              Instruction* U, Value *O)
41    : CallbackVH(U), Parent(P), Expr(E), 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  /// getParent - Return a pointer to the IVUsers that owns
55  /// this IVStrideUse.
56  IVUsers *getParent() const { return Parent; }
57
58  /// getExpr - Return the expression for the use.
59  const SCEV *getExpr() const { return Expr; }
60
61  /// setExpr - Assign a new expression to this use.
62  void setExpr(const SCEV *Val) {
63    Expr = Val;
64  }
65
66  const SCEV *getStride(const Loop *L) const;
67
68  /// getOperandValToReplace - Return the Value of the operand in the user
69  /// instruction that this IVStrideUse is representing.
70  Value *getOperandValToReplace() const {
71    return OperandValToReplace;
72  }
73
74  /// setOperandValToReplace - Assign a new Value as the operand value
75  /// to replace.
76  void setOperandValToReplace(Value *Op) {
77    OperandValToReplace = Op;
78  }
79
80  /// getPostIncLoops - Return the set of loops for which the expression has
81  /// been adjusted to use post-inc mode.
82  const PostIncLoopSet &getPostIncLoops() const {
83    return PostIncLoops;
84  }
85
86  /// transformToPostInc - Transform the expression to post-inc form for the
87  /// given loop.
88  void transformToPostInc(const Loop *L);
89
90private:
91  /// Parent - a pointer to the IVUsers that owns this IVStrideUse.
92  IVUsers *Parent;
93
94  /// Expr - The expression for this use.
95  const SCEV *Expr;
96
97  /// OperandValToReplace - The Value of the operand in the user instruction
98  /// that this IVStrideUse is representing.
99  WeakVH OperandValToReplace;
100
101  /// PostIncLoops - The set of loops for which Expr has been adjusted to
102  /// use post-inc mode. This corresponds with SCEVExpander's post-inc concept.
103  PostIncLoopSet PostIncLoops;
104
105  /// Deleted - Implementation of CallbackVH virtual function to
106  /// receive notification when the User is deleted.
107  virtual void deleted();
108};
109
110template<> struct ilist_traits<IVStrideUse>
111  : public ilist_default_traits<IVStrideUse> {
112  // createSentinel is used to get hold of a node that marks the end of
113  // the list...
114  // The sentinel is relative to this instance, so we use a non-static
115  // method.
116  IVStrideUse *createSentinel() const {
117    // since i(p)lists always publicly derive from the corresponding
118    // traits, placing a data member in this class will augment i(p)list.
119    // But since the NodeTy is expected to publicly derive from
120    // ilist_node<NodeTy>, there is a legal viable downcast from it
121    // to NodeTy. We use this trick to superpose i(p)list with a "ghostly"
122    // NodeTy, which becomes the sentinel. Dereferencing the sentinel is
123    // forbidden (save the ilist_node<NodeTy>) so no one will ever notice
124    // the superposition.
125    return static_cast<IVStrideUse*>(&Sentinel);
126  }
127  static void destroySentinel(IVStrideUse*) {}
128
129  IVStrideUse *provideInitialHead() const { return createSentinel(); }
130  IVStrideUse *ensureHead(IVStrideUse*) const { return createSentinel(); }
131  static void noteHead(IVStrideUse*, IVStrideUse*) {}
132
133private:
134  mutable ilist_node<IVStrideUse> Sentinel;
135};
136
137class IVUsers : public LoopPass {
138  friend class IVStrideUse;
139  Loop *L;
140  LoopInfo *LI;
141  DominatorTree *DT;
142  ScalarEvolution *SE;
143  SmallPtrSet<Instruction*,16> Processed;
144
145  /// IVUses - A list of all tracked IV uses of induction variable expressions
146  /// we are interested in.
147  ilist<IVStrideUse> IVUses;
148
149  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
150
151  virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
152
153  virtual void releaseMemory();
154
155public:
156  static char ID; // Pass ID, replacement for typeid
157  IVUsers();
158
159  /// AddUsersIfInteresting - Inspect the specified Instruction.  If it is a
160  /// reducible SCEV, recursively add its users to the IVUsesByStride set and
161  /// return true.  Otherwise, return false.
162  bool AddUsersIfInteresting(Instruction *I);
163
164  IVStrideUse &AddUser(const SCEV *Expr,
165                       Instruction *User, Value *Operand);
166
167  /// getReplacementExpr - Return a SCEV expression which computes the
168  /// value of the OperandValToReplace of the given IVStrideUse.
169  const SCEV *getReplacementExpr(const IVStrideUse &U) const;
170
171  typedef ilist<IVStrideUse>::iterator iterator;
172  typedef ilist<IVStrideUse>::const_iterator const_iterator;
173  iterator begin() { return IVUses.begin(); }
174  iterator end()   { return IVUses.end(); }
175  const_iterator begin() const { return IVUses.begin(); }
176  const_iterator end() const   { return IVUses.end(); }
177  bool empty() const { return IVUses.empty(); }
178
179  void print(raw_ostream &OS, const Module* = 0) const;
180
181  /// dump - This method is used for debugging.
182  void dump() const;
183};
184
185Pass *createIVUsersPass();
186
187}
188
189#endif
190