//===- llvm/Analysis/MemoryDependenceAnalysis.h - Memory Deps --*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file defines the MemoryDependenceAnalysis analysis pass. // //===----------------------------------------------------------------------===// #ifndef LLVM_ANALYSIS_MEMORY_DEPENDENCE_H #define LLVM_ANALYSIS_MEMORY_DEPENDENCE_H #include "llvm/BasicBlock.h" #include "llvm/Pass.h" #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/OwningPtr.h" #include "llvm/ADT/PointerIntPair.h" namespace llvm { class Function; class FunctionPass; class Instruction; class CallSite; class AliasAnalysis; class TargetData; class MemoryDependenceAnalysis; class PredIteratorCache; /// MemDepResult - A memory dependence query can return one of three different /// answers, described below. class MemDepResult { enum DepType { /// Invalid - Clients of MemDep never see this. Invalid = 0, /// Clobber - This is a dependence on the specified instruction which /// clobbers the desired value. The pointer member of the MemDepResult /// pair holds the instruction that clobbers the memory. For example, /// this occurs when we see a may-aliased store to the memory location we /// care about. Clobber, /// Def - This is a dependence on the specified instruction which /// defines/produces the desired memory location. The pointer member of /// the MemDepResult pair holds the instruction that defines the memory. /// Cases of interest: /// 1. This could be a load or store for dependence queries on /// load/store. The value loaded or stored is the produced value. /// Note that the pointer operand may be different than that of the /// queried pointer due to must aliases and phi translation. Note /// that the def may not be the same type as the query, the pointers /// may just be must aliases. /// 2. For loads and stores, this could be an allocation instruction. In /// this case, the load is loading an undef value or a store is the /// first store to (that part of) the allocation. /// 3. Dependence queries on calls return Def only when they are /// readonly calls with identical callees and no intervening /// clobbers. No validation is done that the operands to the calls /// are the same. Def, /// NonLocal - This marker indicates that the query has no dependency in /// the specified block. To find out more, the client should query other /// predecessor blocks. NonLocal }; typedef PointerIntPair<Instruction*, 2, DepType> PairTy; PairTy Value; explicit MemDepResult(PairTy V) : Value(V) {} public: MemDepResult() : Value(0, Invalid) {} /// get methods: These are static ctor methods for creating various /// MemDepResult kinds. static MemDepResult getDef(Instruction *Inst) { return MemDepResult(PairTy(Inst, Def)); } static MemDepResult getClobber(Instruction *Inst) { return MemDepResult(PairTy(Inst, Clobber)); } static MemDepResult getNonLocal() { return MemDepResult(PairTy(0, NonLocal)); } /// isClobber - Return true if this MemDepResult represents a query that is /// a instruction clobber dependency. bool isClobber() const { return Value.getInt() == Clobber; } /// isDef - Return true if this MemDepResult represents a query that is /// a instruction definition dependency. bool isDef() const { return Value.getInt() == Def; } /// isNonLocal - Return true if this MemDepResult represents an query that /// is transparent to the start of the block, but where a non-local hasn't /// been done. bool isNonLocal() const { return Value.getInt() == NonLocal; } /// getInst() - If this is a normal dependency, return the instruction that /// is depended on. Otherwise, return null. Instruction *getInst() const { return Value.getPointer(); } bool operator==(const MemDepResult &M) const { return Value == M.Value; } bool operator!=(const MemDepResult &M) const { return Value != M.Value; } bool operator<(const MemDepResult &M) const { return Value < M.Value; } bool operator>(const MemDepResult &M) const { return Value > M.Value; } private: friend class MemoryDependenceAnalysis; /// Dirty - Entries with this marker occur in a LocalDeps map or /// NonLocalDeps map when the instruction they previously referenced was /// removed from MemDep. In either case, the entry may include an /// instruction pointer. If so, the pointer is an instruction in the /// block where scanning can start from, saving some work. /// /// In a default-constructed MemDepResult object, the type will be Dirty /// and the instruction pointer will be null. /// /// isDirty - Return true if this is a MemDepResult in its dirty/invalid. /// state. bool isDirty() const { return Value.getInt() == Invalid; } static MemDepResult getDirty(Instruction *Inst) { return MemDepResult(PairTy(Inst, Invalid)); } }; /// MemoryDependenceAnalysis - This is an analysis that determines, for a /// given memory operation, what preceding memory operations it depends on. /// It builds on alias analysis information, and tries to provide a lazy, /// caching interface to a common kind of alias information query. /// /// The dependency information returned is somewhat unusual, but is pragmatic. /// If queried about a store or call that might modify memory, the analysis /// will return the instruction[s] that may either load from that memory or /// store to it. If queried with a load or call that can never modify memory, /// the analysis will return calls and stores that might modify the pointer, /// but generally does not return loads unless a) they are volatile, or /// b) they load from *must-aliased* pointers. Returning a dependence on /// must-alias'd pointers instead of all pointers interacts well with the /// internal caching mechanism. /// class MemoryDependenceAnalysis : public FunctionPass { // A map from instructions to their dependency. typedef DenseMap<Instruction*, MemDepResult> LocalDepMapType; LocalDepMapType LocalDeps; public: typedef std::pair<BasicBlock*, MemDepResult> NonLocalDepEntry; typedef std::vector<NonLocalDepEntry> NonLocalDepInfo; private: /// ValueIsLoadPair - This is a pair<Value*, bool> where the bool is true if /// the dependence is a read only dependence, false if read/write. typedef PointerIntPair<Value*, 1, bool> ValueIsLoadPair; /// BBSkipFirstBlockPair - This pair is used when caching information for a /// block. If the pointer is null, the cache value is not a full query that /// starts at the specified block. If non-null, the bool indicates whether /// or not the contents of the block was skipped. typedef PointerIntPair<BasicBlock*, 1, bool> BBSkipFirstBlockPair; /// CachedNonLocalPointerInfo - This map stores the cached results of doing /// a pointer lookup at the bottom of a block. The key of this map is the /// pointer+isload bit, the value is a list of <bb->result> mappings. typedef DenseMap<ValueIsLoadPair, std::pair<BBSkipFirstBlockPair, NonLocalDepInfo> > CachedNonLocalPointerInfo; CachedNonLocalPointerInfo NonLocalPointerDeps; // A map from instructions to their non-local pointer dependencies. typedef DenseMap<Instruction*, SmallPtrSet<ValueIsLoadPair, 4> > ReverseNonLocalPtrDepTy; ReverseNonLocalPtrDepTy ReverseNonLocalPtrDeps; /// PerInstNLInfo - This is the instruction we keep for each cached access /// that we have for an instruction. The pointer is an owning pointer and /// the bool indicates whether we have any dirty bits in the set. typedef std::pair<NonLocalDepInfo, bool> PerInstNLInfo; // A map from instructions to their non-local dependencies. typedef DenseMap<Instruction*, PerInstNLInfo> NonLocalDepMapType; NonLocalDepMapType NonLocalDeps; // A reverse mapping from dependencies to the dependees. This is // used when removing instructions to keep the cache coherent. typedef DenseMap<Instruction*, SmallPtrSet<Instruction*, 4> > ReverseDepMapType; ReverseDepMapType ReverseLocalDeps; // A reverse mapping form dependencies to the non-local dependees. ReverseDepMapType ReverseNonLocalDeps; /// Current AA implementation, just a cache. AliasAnalysis *AA; TargetData *TD; OwningPtr<PredIteratorCache> PredCache; public: MemoryDependenceAnalysis(); ~MemoryDependenceAnalysis(); static char ID; /// Pass Implementation stuff. This doesn't do any analysis eagerly. bool runOnFunction(Function &); /// Clean up memory in between runs void releaseMemory(); /// getAnalysisUsage - Does not modify anything. It uses Value Numbering /// and Alias Analysis. /// virtual void getAnalysisUsage(AnalysisUsage &AU) const; /// getDependency - Return the instruction on which a memory operation /// depends. See the class comment for more details. It is illegal to call /// this on non-memory instructions. MemDepResult getDependency(Instruction *QueryInst); /// getNonLocalCallDependency - Perform a full dependency query for the /// specified call, returning the set of blocks that the value is /// potentially live across. The returned set of results will include a /// "NonLocal" result for all blocks where the value is live across. /// /// This method assumes the instruction returns a "NonLocal" dependency /// within its own block. /// /// This returns a reference to an internal data structure that may be /// invalidated on the next non-local query or when an instruction is /// removed. Clients must copy this data if they want it around longer than /// that. const NonLocalDepInfo &getNonLocalCallDependency(CallSite QueryCS); /// getNonLocalPointerDependency - Perform a full dependency query for an /// access to the specified (non-volatile) memory location, returning the /// set of instructions that either define or clobber the value. /// /// This method assumes the pointer has a "NonLocal" dependency within BB. void getNonLocalPointerDependency(Value *Pointer, bool isLoad, BasicBlock *BB, SmallVectorImpl<NonLocalDepEntry> &Result); /// removeInstruction - Remove an instruction from the dependence analysis, /// updating the dependence of instructions that previously depended on it. void removeInstruction(Instruction *InstToRemove); /// invalidateCachedPointerInfo - This method is used to invalidate cached /// information about the specified pointer, because it may be too /// conservative in memdep. This is an optional call that can be used when /// the client detects an equivalence between the pointer and some other /// value and replaces the other value with ptr. This can make Ptr available /// in more places that cached info does not necessarily keep. void invalidateCachedPointerInfo(Value *Ptr); private: MemDepResult getPointerDependencyFrom(Value *Pointer, uint64_t MemSize, bool isLoad, BasicBlock::iterator ScanIt, BasicBlock *BB); MemDepResult getCallSiteDependencyFrom(CallSite C, bool isReadOnlyCall, BasicBlock::iterator ScanIt, BasicBlock *BB); bool getNonLocalPointerDepFromBB(Value *Pointer, uint64_t Size, bool isLoad, BasicBlock *BB, SmallVectorImpl<NonLocalDepEntry> &Result, DenseMap<BasicBlock*, Value*> &Visited, bool SkipFirstBlock = false); MemDepResult GetNonLocalInfoForBlock(Value *Pointer, uint64_t PointeeSize, bool isLoad, BasicBlock *BB, NonLocalDepInfo *Cache, unsigned NumSortedEntries); void RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P); /// verifyRemoved - Verify that the specified instruction does not occur /// in our internal data structures. void verifyRemoved(Instruction *Inst) const; }; } // End llvm namespace #endif