llvm/Analysis/IVUsers.h

0001 //===- llvm/Analysis/IVUsers.h - Induction Variable Users -------*- C++ -*-===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008 //
0009 // This file implements bookkeeping for "interesting" users of expressions
0010 // computed from induction variables.
0011 //
0012 //===----------------------------------------------------------------------===//
0013
0014 #ifndef LLVM_ANALYSIS_IVUSERS_H
0015 #define LLVM_ANALYSIS_IVUSERS_H
0016
0017 #include "llvm/Analysis/LoopAnalysisManager.h"
0018 #include "llvm/Analysis/LoopPass.h"
0019 #include "llvm/Analysis/ScalarEvolutionNormalization.h"
0020 #include "llvm/IR/Instruction.h"
0021 #include "llvm/IR/ValueHandle.h"
0022
0023 namespace llvm {
0024
0025 class AssumptionCache;
0026 class DominatorTree;
0027 class ScalarEvolution;
0028 class SCEV;
0029 class IVUsers;
0030
0031 /// IVStrideUse - Keep track of one use of a strided induction variable.
0032 /// The Expr member keeps track of the expression, User is the actual user
0033 /// instruction of the operand, and 'OperandValToReplace' is the operand of
0034 /// the User that is the use.
0035 class IVStrideUse final : public CallbackVH, public ilist_node<IVStrideUse> {
0036   friend class IVUsers;
0037 public:
0038   IVStrideUse(IVUsers *P, Instruction* U, Value *O)
0039     : CallbackVH(U), Parent(P), OperandValToReplace(O) {
0040   }
0041
0042   /// getUser - Return the user instruction for this use.
0043   Instruction *getUser() const {
0044     return cast<Instruction>(getValPtr());
0045   }
0046
0047   /// setUser - Assign a new user instruction for this use.
0048   void setUser(Instruction *NewUser) {
0049     setValPtr(NewUser);
0050   }
0051
0052   /// getOperandValToReplace - Return the Value of the operand in the user
0053   /// instruction that this IVStrideUse is representing.
0054   Value *getOperandValToReplace() const {
0055     return OperandValToReplace;
0056   }
0057
0058   /// setOperandValToReplace - Assign a new Value as the operand value
0059   /// to replace.
0060   void setOperandValToReplace(Value *Op) {
0061     OperandValToReplace = Op;
0062   }
0063
0064   /// getPostIncLoops - Return the set of loops for which the expression has
0065   /// been adjusted to use post-inc mode.
0066   const PostIncLoopSet &getPostIncLoops() const {
0067     return PostIncLoops;
0068   }
0069
0070   /// transformToPostInc - Transform the expression to post-inc form for the
0071   /// given loop.
0072   void transformToPostInc(const Loop *L);
0073
0074 private:
0075   /// Parent - a pointer to the IVUsers that owns this IVStrideUse.
0076   IVUsers *Parent;
0077
0078   /// OperandValToReplace - The Value of the operand in the user instruction
0079   /// that this IVStrideUse is representing.
0080   WeakTrackingVH OperandValToReplace;
0081
0082   /// PostIncLoops - The set of loops for which Expr has been adjusted to
0083   /// use post-inc mode. This corresponds with SCEVExpander's post-inc concept.
0084   PostIncLoopSet PostIncLoops;
0085
0086   /// Deleted - Implementation of CallbackVH virtual function to
0087   /// receive notification when the User is deleted.
0088   void deleted() override;
0089 };
0090
0091 class IVUsers {
0092   friend class IVStrideUse;
0093   Loop *L;
0094   AssumptionCache *AC;
0095   LoopInfo *LI;
0096   DominatorTree *DT;
0097   ScalarEvolution *SE;
0098   SmallPtrSet<Instruction*, 16> Processed;
0099
0100   /// IVUses - A list of all tracked IV uses of induction variable expressions
0101   /// we are interested in.
0102   ilist<IVStrideUse> IVUses;
0103
0104   // Ephemeral values used by @llvm.assume in this function.
0105   SmallPtrSet<const Value *, 32> EphValues;
0106
0107 public:
0108   IVUsers(Loop *L, AssumptionCache *AC, LoopInfo *LI, DominatorTree *DT,
0109           ScalarEvolution *SE);
0110
0111   IVUsers(IVUsers &&X)
0112       : L(std::move(X.L)), AC(std::move(X.AC)), DT(std::move(X.DT)),
0113         SE(std::move(X.SE)), Processed(std::move(X.Processed)),
0114         IVUses(std::move(X.IVUses)), EphValues(std::move(X.EphValues)) {
0115     for (IVStrideUse &U : IVUses)
0116       U.Parent = this;
0117   }
0118   IVUsers(const IVUsers &) = delete;
0119   IVUsers &operator=(IVUsers &&) = delete;
0120   IVUsers &operator=(const IVUsers &) = delete;
0121
0122   Loop *getLoop() const { return L; }
0123
0124   /// AddUsersIfInteresting - Inspect the specified Instruction.  If it is a
0125   /// reducible SCEV, recursively add its users to the IVUsesByStride set and
0126   /// return true.  Otherwise, return false.
0127   bool AddUsersIfInteresting(Instruction *I);
0128
0129   IVStrideUse &AddUser(Instruction *User, Value *Operand);
0130
0131   /// getReplacementExpr - Return a SCEV expression which computes the
0132   /// value of the OperandValToReplace of the given IVStrideUse.
0133   const SCEV *getReplacementExpr(const IVStrideUse &IU) const;
0134
0135   /// getExpr - Return the expression for the use. Returns nullptr if the result
0136   /// is not invertible.
0137   const SCEV *getExpr(const IVStrideUse &IU) const;
0138
0139   const SCEV *getStride(const IVStrideUse &IU, const Loop *L) const;
0140
0141   typedef ilist<IVStrideUse>::iterator iterator;
0142   typedef ilist<IVStrideUse>::const_iterator const_iterator;
0143   iterator begin() { return IVUses.begin(); }
0144   iterator end()   { return IVUses.end(); }
0145   const_iterator begin() const { return IVUses.begin(); }
0146   const_iterator end() const   { return IVUses.end(); }
0147   bool empty() const { return IVUses.empty(); }
0148
0149   bool isIVUserOrOperand(Instruction *Inst) const {
0150     return Processed.count(Inst);
0151   }
0152
0153   void releaseMemory();
0154
0155   void print(raw_ostream &OS, const Module * = nullptr) const;
0156
0157   /// dump - This method is used for debugging.
0158   void dump() const;
0159 };
0160
0161 Pass *createIVUsersPass();
0162
0163 class IVUsersWrapperPass : public LoopPass {
0164   std::unique_ptr<IVUsers> IU;
0165
0166 public:
0167   static char ID;
0168
0169   IVUsersWrapperPass();
0170
0171   IVUsers &getIU() { return *IU; }
0172   const IVUsers &getIU() const { return *IU; }
0173
0174   void getAnalysisUsage(AnalysisUsage &AU) const override;
0175
0176   bool runOnLoop(Loop *L, LPPassManager &LPM) override;
0177
0178   void releaseMemory() override;
0179
0180   void print(raw_ostream &OS, const Module * = nullptr) const override;
0181 };
0182
0183 /// Analysis pass that exposes the \c IVUsers for a loop.
0184 class IVUsersAnalysis : public AnalysisInfoMixin<IVUsersAnalysis> {
0185   friend AnalysisInfoMixin<IVUsersAnalysis>;
0186   static AnalysisKey Key;
0187
0188 public:
0189   typedef IVUsers Result;
0190
0191   IVUsers run(Loop &L, LoopAnalysisManager &AM,
0192               LoopStandardAnalysisResults &AR);
0193 };
0194
0195 }
0196
0197 #endif