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/Instruction.h"
21 #include "llvm/IR/ValueHandle.h"
22 
23 namespace llvm {
24 
25 class AssumptionCache;
26 class DominatorTree;
27 class ScalarEvolution;
28 class SCEV;
29 class IVUsers;
30 
31 /// IVStrideUse - Keep track of one use of a strided induction variable.
32 /// The Expr member keeps track of the expression, User is the actual user
33 /// instruction of the operand, and 'OperandValToReplace' is the operand of
34 /// the User that is the use.
35 class IVStrideUse final : public CallbackVH, public ilist_node<IVStrideUse> {
36   friend class IVUsers;
37 public:
IVStrideUse(IVUsers * P,Instruction * U,Value * O)38   IVStrideUse(IVUsers *P, Instruction* U, Value *O)
39     : CallbackVH(U), Parent(P), OperandValToReplace(O) {
40   }
41 
42   /// getUser - Return the user instruction for this use.
getUser()43   Instruction *getUser() const {
44     return cast<Instruction>(getValPtr());
45   }
46 
47   /// setUser - Assign a new user instruction for this use.
setUser(Instruction * NewUser)48   void setUser(Instruction *NewUser) {
49     setValPtr(NewUser);
50   }
51 
52   /// getOperandValToReplace - Return the Value of the operand in the user
53   /// instruction that this IVStrideUse is representing.
getOperandValToReplace()54   Value *getOperandValToReplace() const {
55     return OperandValToReplace;
56   }
57 
58   /// setOperandValToReplace - Assign a new Value as the operand value
59   /// to replace.
setOperandValToReplace(Value * Op)60   void setOperandValToReplace(Value *Op) {
61     OperandValToReplace = Op;
62   }
63 
64   /// getPostIncLoops - Return the set of loops for which the expression has
65   /// been adjusted to use post-inc mode.
getPostIncLoops()66   const PostIncLoopSet &getPostIncLoops() const {
67     return PostIncLoops;
68   }
69 
70   /// transformToPostInc - Transform the expression to post-inc form for the
71   /// given loop.
72   void transformToPostInc(const Loop *L);
73 
74 private:
75   /// Parent - a pointer to the IVUsers that owns this IVStrideUse.
76   IVUsers *Parent;
77 
78   /// OperandValToReplace - The Value of the operand in the user instruction
79   /// that this IVStrideUse is representing.
80   WeakTrackingVH OperandValToReplace;
81 
82   /// PostIncLoops - The set of loops for which Expr has been adjusted to
83   /// use post-inc mode. This corresponds with SCEVExpander's post-inc concept.
84   PostIncLoopSet PostIncLoops;
85 
86   /// Deleted - Implementation of CallbackVH virtual function to
87   /// receive notification when the User is deleted.
88   void deleted() override;
89 };
90 
91 class IVUsers {
92   friend class IVStrideUse;
93   Loop *L;
94   AssumptionCache *AC;
95   LoopInfo *LI;
96   DominatorTree *DT;
97   ScalarEvolution *SE;
98   SmallPtrSet<Instruction*, 16> Processed;
99 
100   /// IVUses - A list of all tracked IV uses of induction variable expressions
101   /// we are interested in.
102   ilist<IVStrideUse> IVUses;
103 
104   // Ephemeral values used by @llvm.assume in this function.
105   SmallPtrSet<const Value *, 32> EphValues;
106 
107 public:
108   IVUsers(Loop *L, AssumptionCache *AC, LoopInfo *LI, DominatorTree *DT,
109           ScalarEvolution *SE);
110 
IVUsers(IVUsers && X)111   IVUsers(IVUsers &&X)
112       : L(std::move(X.L)), AC(std::move(X.AC)), DT(std::move(X.DT)),
113         SE(std::move(X.SE)), Processed(std::move(X.Processed)),
114         IVUses(std::move(X.IVUses)), EphValues(std::move(X.EphValues)) {
115     for (IVStrideUse &U : IVUses)
116       U.Parent = this;
117   }
118   IVUsers(const IVUsers &) = delete;
119   IVUsers &operator=(IVUsers &&) = delete;
120   IVUsers &operator=(const IVUsers &) = delete;
121 
getLoop()122   Loop *getLoop() const { return L; }
123 
124   /// AddUsersIfInteresting - Inspect the specified Instruction.  If it is a
125   /// reducible SCEV, recursively add its users to the IVUsesByStride set and
126   /// return true.  Otherwise, return false.
127   bool AddUsersIfInteresting(Instruction *I);
128 
129   IVStrideUse &AddUser(Instruction *User, Value *Operand);
130 
131   /// getReplacementExpr - Return a SCEV expression which computes the
132   /// value of the OperandValToReplace of the given IVStrideUse.
133   const SCEV *getReplacementExpr(const IVStrideUse &IU) const;
134 
135   /// getExpr - Return the expression for the use. Returns nullptr if the result
136   /// is not invertible.
137   const SCEV *getExpr(const IVStrideUse &IU) const;
138 
139   const SCEV *getStride(const IVStrideUse &IU, const Loop *L) const;
140 
141   typedef ilist<IVStrideUse>::iterator iterator;
142   typedef ilist<IVStrideUse>::const_iterator const_iterator;
begin()143   iterator begin() { return IVUses.begin(); }
end()144   iterator end()   { return IVUses.end(); }
begin()145   const_iterator begin() const { return IVUses.begin(); }
end()146   const_iterator end() const   { return IVUses.end(); }
empty()147   bool empty() const { return IVUses.empty(); }
148 
isIVUserOrOperand(Instruction * Inst)149   bool isIVUserOrOperand(Instruction *Inst) const {
150     return Processed.count(Inst);
151   }
152 
153   void releaseMemory();
154 
155   void print(raw_ostream &OS, const Module * = nullptr) const;
156 
157   /// dump - This method is used for debugging.
158   void dump() const;
159 };
160 
161 Pass *createIVUsersPass();
162 
163 class IVUsersWrapperPass : public LoopPass {
164   std::unique_ptr<IVUsers> IU;
165 
166 public:
167   static char ID;
168 
169   IVUsersWrapperPass();
170 
getIU()171   IVUsers &getIU() { return *IU; }
getIU()172   const IVUsers &getIU() const { return *IU; }
173 
174   void getAnalysisUsage(AnalysisUsage &AU) const override;
175 
176   bool runOnLoop(Loop *L, LPPassManager &LPM) override;
177 
178   void releaseMemory() override;
179 
180   void print(raw_ostream &OS, const Module * = nullptr) const override;
181 };
182 
183 /// Analysis pass that exposes the \c IVUsers for a loop.
184 class IVUsersAnalysis : public AnalysisInfoMixin<IVUsersAnalysis> {
185   friend AnalysisInfoMixin<IVUsersAnalysis>;
186   static AnalysisKey Key;
187 
188 public:
189   typedef IVUsers Result;
190 
191   IVUsers run(Loop &L, LoopAnalysisManager &AM,
192               LoopStandardAnalysisResults &AR);
193 };
194 
195 }
196 
197 #endif
198