//===- 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_MEMORYDEPENDENCEANALYSIS_H #define LLVM_ANALYSIS_MEMORYDEPENDENCEANALYSIS_H #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/OwningPtr.h" #include "llvm/ADT/PointerIntPair.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/Analysis/AliasAnalysis.h" #include "llvm/IR/BasicBlock.h" #include "llvm/Pass.h" #include "llvm/Support/ValueHandle.h" namespace llvm { class Function; class FunctionPass; class Instruction; class CallSite; class AliasAnalysis; class DataLayout; class MemoryDependenceAnalysis; class PredIteratorCache; class DominatorTree; class PHITransAddr; /// 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. /// /// There are several cases that may be interesting here: /// 1. Loads are clobbered by may-alias stores. /// 2. Loads are considered clobbered by partially-aliased loads. The /// client may choose to analyze deeper into these cases. 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 or memory use intrinsics with identical callees /// and no intervening clobbers. No validation is done that the /// operands to the calls are the same. Def, /// Other - This marker indicates that the query has no known dependency /// in the specified block. More detailed state info is encoded in the /// upper part of the pair (i.e. the Instruction*) Other }; /// If DepType is "Other", the upper part of the pair /// (i.e. the Instruction* part) is instead used to encode more detailed /// type information as follows enum OtherType { /// 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 = 0x4, /// NonFuncLocal - This marker indicates that the query has no /// dependency in the specified function. NonFuncLocal = 0x8, /// Unknown - This marker indicates that the query dependency /// is unknown. Unknown = 0xc }; 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) { assert(Inst && "Def requires inst"); return MemDepResult(PairTy(Inst, Def)); } static MemDepResult getClobber(Instruction *Inst) { assert(Inst && "Clobber requires inst"); return MemDepResult(PairTy(Inst, Clobber)); } static MemDepResult getNonLocal() { return MemDepResult( PairTy(reinterpret_cast<Instruction*>(NonLocal), Other)); } static MemDepResult getNonFuncLocal() { return MemDepResult( PairTy(reinterpret_cast<Instruction*>(NonFuncLocal), Other)); } static MemDepResult getUnknown() { return MemDepResult( PairTy(reinterpret_cast<Instruction*>(Unknown), Other)); } /// isClobber - Return true if this MemDepResult represents a query that is /// an instruction clobber dependency. bool isClobber() const { return Value.getInt() == Clobber; } /// isDef - Return true if this MemDepResult represents a query that is /// an instruction definition dependency. bool isDef() const { return Value.getInt() == Def; } /// isNonLocal - Return true if this MemDepResult represents a 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() == Other && Value.getPointer() == reinterpret_cast<Instruction*>(NonLocal); } /// isNonFuncLocal - Return true if this MemDepResult represents a query /// that is transparent to the start of the function. bool isNonFuncLocal() const { return Value.getInt() == Other && Value.getPointer() == reinterpret_cast<Instruction*>(NonFuncLocal); } /// isUnknown - Return true if this MemDepResult represents a query which /// cannot and/or will not be computed. bool isUnknown() const { return Value.getInt() == Other && Value.getPointer() == reinterpret_cast<Instruction*>(Unknown); } /// getInst() - If this is a normal dependency, return the instruction that /// is depended on. Otherwise, return null. Instruction *getInst() const { if (Value.getInt() == Other) return NULL; 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)); } }; /// NonLocalDepEntry - This is an entry in the NonLocalDepInfo cache. For /// each BasicBlock (the BB entry) it keeps a MemDepResult. class NonLocalDepEntry { BasicBlock *BB; MemDepResult Result; public: NonLocalDepEntry(BasicBlock *bb, MemDepResult result) : BB(bb), Result(result) {} // This is used for searches. NonLocalDepEntry(BasicBlock *bb) : BB(bb) {} // BB is the sort key, it can't be changed. BasicBlock *getBB() const { return BB; } void setResult(const MemDepResult &R) { Result = R; } const MemDepResult &getResult() const { return Result; } bool operator<(const NonLocalDepEntry &RHS) const { return BB < RHS.BB; } }; /// NonLocalDepResult - This is a result from a NonLocal dependence query. /// For each BasicBlock (the BB entry) it keeps a MemDepResult and the /// (potentially phi translated) address that was live in the block. class NonLocalDepResult { NonLocalDepEntry Entry; Value *Address; public: NonLocalDepResult(BasicBlock *bb, MemDepResult result, Value *address) : Entry(bb, result), Address(address) {} // BB is the sort key, it can't be changed. BasicBlock *getBB() const { return Entry.getBB(); } void setResult(const MemDepResult &R, Value *Addr) { Entry.setResult(R); Address = Addr; } const MemDepResult &getResult() const { return Entry.getResult(); } /// getAddress - Return the address of this pointer in this block. This can /// be different than the address queried for the non-local result because /// of phi translation. This returns null if the address was not available /// in a block (i.e. because phi translation failed) or if this is a cached /// result and that address was deleted. /// /// The address is always null for a non-local 'call' dependence. Value *getAddress() const { return Address; } }; /// 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::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<const 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; /// NonLocalPointerInfo - This record is the information kept for each /// (value, is load) pair. struct NonLocalPointerInfo { /// Pair - The pair of the block and the skip-first-block flag. BBSkipFirstBlockPair Pair; /// NonLocalDeps - The results of the query for each relevant block. NonLocalDepInfo NonLocalDeps; /// Size - The maximum size of the dereferences of the /// pointer. May be UnknownSize if the sizes are unknown. uint64_t Size; /// TBAATag - The TBAA tag associated with dereferences of the /// pointer. May be null if there are no tags or conflicting tags. const MDNode *TBAATag; NonLocalPointerInfo() : Size(AliasAnalysis::UnknownSize), TBAATag(0) {} }; /// 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, NonLocalPointerInfo> 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 from dependencies to the non-local dependees. ReverseDepMapType ReverseNonLocalDeps; /// Current AA implementation, just a cache. AliasAnalysis *AA; DataLayout *TD; DominatorTree *DT; 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(const AliasAnalysis::Location &Loc, bool isLoad, BasicBlock *BB, SmallVectorImpl<NonLocalDepResult> &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); /// invalidateCachedPredecessors - Clear the PredIteratorCache info. /// This needs to be done when the CFG changes, e.g., due to splitting /// critical edges. void invalidateCachedPredecessors(); /// getPointerDependencyFrom - Return the instruction on which a memory /// location depends. If isLoad is true, this routine ignores may-aliases /// with read-only operations. If isLoad is false, this routine ignores /// may-aliases with reads from read-only locations. If possible, pass /// the query instruction as well; this function may take advantage of /// the metadata annotated to the query instruction to refine the result. /// /// Note that this is an uncached query, and thus may be inefficient. /// MemDepResult getPointerDependencyFrom(const AliasAnalysis::Location &Loc, bool isLoad, BasicBlock::iterator ScanIt, BasicBlock *BB, Instruction *QueryInst = 0); /// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that /// looks at a memory location for a load (specified by MemLocBase, Offs, /// and Size) and compares it against a load. If the specified load could /// be safely widened to a larger integer load that is 1) still efficient, /// 2) safe for the target, and 3) would provide the specified memory /// location value, then this function returns the size in bytes of the /// load width to use. If not, this returns zero. static unsigned getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs, unsigned MemLocSize, const LoadInst *LI, const DataLayout &TD); private: MemDepResult getCallSiteDependencyFrom(CallSite C, bool isReadOnlyCall, BasicBlock::iterator ScanIt, BasicBlock *BB); bool getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, const AliasAnalysis::Location &Loc, bool isLoad, BasicBlock *BB, SmallVectorImpl<NonLocalDepResult> &Result, DenseMap<BasicBlock*, Value*> &Visited, bool SkipFirstBlock = false); MemDepResult GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc, 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