1 //===- llvm/Analysis/IVUsers.h - Induction Variable Users -------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements bookkeeping for "interesting" users of expressions
10 // computed from induction variables.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_ANALYSIS_IVUSERS_H
15 #define LLVM_ANALYSIS_IVUSERS_H
16 
17 #include "llvm/Analysis/LoopAnalysisManager.h"
18 #include "llvm/Analysis/LoopPass.h"
19 #include "llvm/Analysis/ScalarEvolutionNormalization.h"
20 #include "llvm/IR/ValueHandle.h"
21 
22 namespace llvm {
23 
24 class AssumptionCache;
25 class DominatorTree;
26 class ScalarEvolution;
27 class SCEV;
28 class IVUsers;
29 
30 /// IVStrideUse - Keep track of one use of a strided induction variable.
31 /// The Expr member keeps track of the expression, User is the actual user
32 /// instruction of the operand, and 'OperandValToReplace' is the operand of
33 /// the User that is the use.
34 class IVStrideUse final : public CallbackVH, public ilist_node<IVStrideUse> {
35   friend class IVUsers;
36 public:
IVStrideUse(IVUsers * P,Instruction * U,Value * O)37   IVStrideUse(IVUsers *P, Instruction* U, Value *O)
38     : CallbackVH(U), Parent(P), OperandValToReplace(O) {
39   }
40 
41   /// getUser - Return the user instruction for this use.
getUser()42   Instruction *getUser() const {
43     return cast<Instruction>(getValPtr());
44   }
45 
46   /// setUser - Assign a new user instruction for this use.
setUser(Instruction * NewUser)47   void setUser(Instruction *NewUser) {
48     setValPtr(NewUser);
49   }
50 
51   /// getOperandValToReplace - Return the Value of the operand in the user
52   /// instruction that this IVStrideUse is representing.
getOperandValToReplace()53   Value *getOperandValToReplace() const {
54     return OperandValToReplace;
55   }
56 
57   /// setOperandValToReplace - Assign a new Value as the operand value
58   /// to replace.
setOperandValToReplace(Value * Op)59   void setOperandValToReplace(Value *Op) {
60     OperandValToReplace = Op;
61   }
62 
63   /// getPostIncLoops - Return the set of loops for which the expression has
64   /// been adjusted to use post-inc mode.
getPostIncLoops()65   const PostIncLoopSet &getPostIncLoops() const {
66     return PostIncLoops;
67   }
68 
69   /// transformToPostInc - Transform the expression to post-inc form for the
70   /// given loop.
71   void transformToPostInc(const Loop *L);
72 
73 private:
74   /// Parent - a pointer to the IVUsers that owns this IVStrideUse.
75   IVUsers *Parent;
76 
77   /// OperandValToReplace - The Value of the operand in the user instruction
78   /// that this IVStrideUse is representing.
79   WeakTrackingVH OperandValToReplace;
80 
81   /// PostIncLoops - The set of loops for which Expr has been adjusted to
82   /// use post-inc mode. This corresponds with SCEVExpander's post-inc concept.
83   PostIncLoopSet PostIncLoops;
84 
85   /// Deleted - Implementation of CallbackVH virtual function to
86   /// receive notification when the User is deleted.
87   void deleted() override;
88 };
89 
90 class IVUsers {
91   friend class IVStrideUse;
92   Loop *L;
93   AssumptionCache *AC;
94   LoopInfo *LI;
95   DominatorTree *DT;
96   ScalarEvolution *SE;
97   SmallPtrSet<Instruction*, 16> Processed;
98 
99   /// IVUses - A list of all tracked IV uses of induction variable expressions
100   /// we are interested in.
101   ilist<IVStrideUse> IVUses;
102 
103   // Ephemeral values used by @llvm.assume in this function.
104   SmallPtrSet<const Value *, 32> EphValues;
105 
106 public:
107   IVUsers(Loop *L, AssumptionCache *AC, LoopInfo *LI, DominatorTree *DT,
108           ScalarEvolution *SE);
109 
IVUsers(IVUsers && X)110   IVUsers(IVUsers &&X)
111       : L(std::move(X.L)), AC(std::move(X.AC)), DT(std::move(X.DT)),
112         SE(std::move(X.SE)), Processed(std::move(X.Processed)),
113         IVUses(std::move(X.IVUses)), EphValues(std::move(X.EphValues)) {
114     for (IVStrideUse &U : IVUses)
115       U.Parent = this;
116   }
117   IVUsers(const IVUsers &) = delete;
118   IVUsers &operator=(IVUsers &&) = delete;
119   IVUsers &operator=(const IVUsers &) = delete;
120 
getLoop()121   Loop *getLoop() const { return L; }
122 
123   /// AddUsersIfInteresting - Inspect the specified Instruction.  If it is a
124   /// reducible SCEV, recursively add its users to the IVUsesByStride set and
125   /// return true.  Otherwise, return false.
126   bool AddUsersIfInteresting(Instruction *I);
127 
128   IVStrideUse &AddUser(Instruction *User, Value *Operand);
129 
130   /// getReplacementExpr - Return a SCEV expression which computes the
131   /// value of the OperandValToReplace of the given IVStrideUse.
132   const SCEV *getReplacementExpr(const IVStrideUse &IU) const;
133 
134   /// getExpr - Return the expression for the use. Returns nullptr if the result
135   /// is not invertible.
136   const SCEV *getExpr(const IVStrideUse &IU) const;
137 
138   const SCEV *getStride(const IVStrideUse &IU, const Loop *L) const;
139 
140   typedef ilist<IVStrideUse>::iterator iterator;
141   typedef ilist<IVStrideUse>::const_iterator const_iterator;
begin()142   iterator begin() { return IVUses.begin(); }
end()143   iterator end()   { return IVUses.end(); }
begin()144   const_iterator begin() const { return IVUses.begin(); }
end()145   const_iterator end() const   { return IVUses.end(); }
empty()146   bool empty() const { return IVUses.empty(); }
147 
isIVUserOrOperand(Instruction * Inst)148   bool isIVUserOrOperand(Instruction *Inst) const {
149     return Processed.count(Inst);
150   }
151 
152   void releaseMemory();
153 
154   void print(raw_ostream &OS, const Module * = nullptr) const;
155 
156   /// dump - This method is used for debugging.
157   void dump() const;
158 };
159 
160 Pass *createIVUsersPass();
161 
162 class IVUsersWrapperPass : public LoopPass {
163   std::unique_ptr<IVUsers> IU;
164 
165 public:
166   static char ID;
167 
168   IVUsersWrapperPass();
169 
getIU()170   IVUsers &getIU() { return *IU; }
getIU()171   const IVUsers &getIU() const { return *IU; }
172 
173   void getAnalysisUsage(AnalysisUsage &AU) const override;
174 
175   bool runOnLoop(Loop *L, LPPassManager &LPM) override;
176 
177   void releaseMemory() override;
178 
179   void print(raw_ostream &OS, const Module * = nullptr) const override;
180 };
181 
182 /// Analysis pass that exposes the \c IVUsers for a loop.
183 class IVUsersAnalysis : public AnalysisInfoMixin<IVUsersAnalysis> {
184   friend AnalysisInfoMixin<IVUsersAnalysis>;
185   static AnalysisKey Key;
186 
187 public:
188   typedef IVUsers Result;
189 
190   IVUsers run(Loop &L, LoopAnalysisManager &AM,
191               LoopStandardAnalysisResults &AR);
192 };
193 
194 }
195 
196 #endif
197