//===- llvm/Analysis/AliasAnalysis.h - Alias Analysis Interface -*- 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 generic AliasAnalysis interface, which is used as the // common interface used by all clients of alias analysis information, and // implemented by all alias analysis implementations. Mod/Ref information is // also captured by this interface. // // Implementations of this interface must implement the various virtual methods, // which automatically provides functionality for the entire suite of client // APIs. // // This API represents memory as a (Pointer, Size) pair. The Pointer component // specifies the base memory address of the region, the Size specifies how large // of an area is being queried, or UnknownSize if the size is not known. // Pointers that point to two completely different objects in memory never // alias, regardless of the value of the Size component. // //===----------------------------------------------------------------------===// #ifndef LLVM_ANALYSIS_ALIAS_ANALYSIS_H #define LLVM_ANALYSIS_ALIAS_ANALYSIS_H #include "llvm/Support/CallSite.h" #include <vector> namespace llvm { class LoadInst; class StoreInst; class VAArgInst; class TargetData; class Pass; class AnalysisUsage; class AliasAnalysis { protected: const TargetData *TD; private: AliasAnalysis *AA; // Previous Alias Analysis to chain to. protected: /// InitializeAliasAnalysis - Subclasses must call this method to initialize /// the AliasAnalysis interface before any other methods are called. This is /// typically called by the run* methods of these subclasses. This may be /// called multiple times. /// void InitializeAliasAnalysis(Pass *P); /// getAnalysisUsage - All alias analysis implementations should invoke this /// directly (using AliasAnalysis::getAnalysisUsage(AU)). virtual void getAnalysisUsage(AnalysisUsage &AU) const; public: static char ID; // Class identification, replacement for typeinfo AliasAnalysis() : TD(0), AA(0) {} virtual ~AliasAnalysis(); // We want to be subclassed /// UnknownSize - This is a special value which can be used with the /// size arguments in alias queries to indicate that the caller does not /// know the sizes of the potential memory references. static uint64_t const UnknownSize = ~UINT64_C(0); /// getTargetData - Return a pointer to the current TargetData object, or /// null if no TargetData object is available. /// const TargetData *getTargetData() const { return TD; } /// getTypeStoreSize - Return the TargetData store size for the given type, /// if known, or a conservative value otherwise. /// uint64_t getTypeStoreSize(const Type *Ty); //===--------------------------------------------------------------------===// /// Alias Queries... /// /// Location - A description of a memory location. struct Location { /// Ptr - The address of the start of the location. const Value *Ptr; /// Size - The size of the location. uint64_t Size; /// TBAATag - The metadata node which describes the TBAA type of /// the location, or null if there is no (unique) tag. const MDNode *TBAATag; explicit Location(const Value *P = 0, uint64_t S = UnknownSize, const MDNode *N = 0) : Ptr(P), Size(S), TBAATag(N) {} Location getWithNewPtr(const Value *NewPtr) const { Location Copy(*this); Copy.Ptr = NewPtr; return Copy; } Location getWithoutTBAATag() const { Location Copy(*this); Copy.TBAATag = 0; return Copy; } }; /// Alias analysis result - Either we know for sure that it does not alias, we /// know for sure it must alias, or we don't know anything: The two pointers /// _might_ alias. This enum is designed so you can do things like: /// if (AA.alias(P1, P2)) { ... } /// to check to see if two pointers might alias. /// /// See docs/AliasAnalysis.html for more information on the specific meanings /// of these values. /// enum AliasResult { NoAlias = 0, MayAlias = 1, MustAlias = 2 }; /// alias - The main low level interface to the alias analysis implementation. /// Returns a Result indicating whether the two pointers are aliased to each /// other. This is the interface that must be implemented by specific alias /// analysis implementations. virtual AliasResult alias(const Location &LocA, const Location &LocB); /// alias - A convenience wrapper. AliasResult alias(const Value *V1, uint64_t V1Size, const Value *V2, uint64_t V2Size) { return alias(Location(V1, V1Size), Location(V2, V2Size)); } /// alias - A convenience wrapper. AliasResult alias(const Value *V1, const Value *V2) { return alias(V1, UnknownSize, V2, UnknownSize); } /// isNoAlias - A trivial helper function to check to see if the specified /// pointers are no-alias. bool isNoAlias(const Location &LocA, const Location &LocB) { return alias(LocA, LocB) == NoAlias; } /// isNoAlias - A convenience wrapper. bool isNoAlias(const Value *V1, uint64_t V1Size, const Value *V2, uint64_t V2Size) { return isNoAlias(Location(V1, V1Size), Location(V2, V2Size)); } /// pointsToConstantMemory - If the specified memory location is known to be /// constant, return true. This allows disambiguation of store /// instructions from constant pointers. /// virtual bool pointsToConstantMemory(const Location &Loc); /// pointsToConstantMemory - A convenient wrapper. bool pointsToConstantMemory(const Value *P) { return pointsToConstantMemory(Location(P)); } //===--------------------------------------------------------------------===// /// Simple mod/ref information... /// /// ModRefResult - Represent the result of a mod/ref query. Mod and Ref are /// bits which may be or'd together. /// enum ModRefResult { NoModRef = 0, Ref = 1, Mod = 2, ModRef = 3 }; /// ModRefBehavior - Summary of how a function affects memory in the program. /// Loads from constant globals are not considered memory accesses for this /// interface. Also, functions may freely modify stack space local to their /// invocation without having to report it through these interfaces. enum ModRefBehavior { // DoesNotAccessMemory - This function does not perform any non-local loads // or stores to memory. // // This property corresponds to the GCC 'const' attribute. DoesNotAccessMemory, // AccessesArguments - This function accesses function arguments in well // known (possibly volatile) ways, but does not access any other memory. AccessesArguments, // AccessesArgumentsAndGlobals - This function has accesses function // arguments and global variables well known (possibly volatile) ways, but // does not access any other memory. AccessesArgumentsAndGlobals, // OnlyReadsMemory - This function does not perform any non-local stores or // volatile loads, but may read from any memory location. // // This property corresponds to the GCC 'pure' attribute. OnlyReadsMemory, // UnknownModRefBehavior - This indicates that the function could not be // classified into one of the behaviors above. UnknownModRefBehavior }; /// getModRefBehavior - Return the behavior when calling the given call site. virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS); /// getModRefBehavior - Return the behavior when calling the given function. /// For use when the call site is not known. virtual ModRefBehavior getModRefBehavior(const Function *F); /// getIntrinsicModRefBehavior - Return the modref behavior of the intrinsic /// with the given id. Most clients won't need this, because the regular /// getModRefBehavior incorporates this information. static ModRefBehavior getIntrinsicModRefBehavior(unsigned iid); /// doesNotAccessMemory - If the specified call is known to never read or /// write memory, return true. If the call only reads from known-constant /// memory, it is also legal to return true. Calls that unwind the stack /// are legal for this predicate. /// /// Many optimizations (such as CSE and LICM) can be performed on such calls /// without worrying about aliasing properties, and many calls have this /// property (e.g. calls to 'sin' and 'cos'). /// /// This property corresponds to the GCC 'const' attribute. /// bool doesNotAccessMemory(ImmutableCallSite CS) { return getModRefBehavior(CS) == DoesNotAccessMemory; } /// doesNotAccessMemory - If the specified function is known to never read or /// write memory, return true. For use when the call site is not known. /// bool doesNotAccessMemory(const Function *F) { return getModRefBehavior(F) == DoesNotAccessMemory; } /// onlyReadsMemory - If the specified call is known to only read from /// non-volatile memory (or not access memory at all), return true. Calls /// that unwind the stack are legal for this predicate. /// /// This property allows many common optimizations to be performed in the /// absence of interfering store instructions, such as CSE of strlen calls. /// /// This property corresponds to the GCC 'pure' attribute. /// bool onlyReadsMemory(ImmutableCallSite CS) { ModRefBehavior MRB = getModRefBehavior(CS); return MRB == DoesNotAccessMemory || MRB == OnlyReadsMemory; } /// onlyReadsMemory - If the specified function is known to only read from /// non-volatile memory (or not access memory at all), return true. For use /// when the call site is not known. /// bool onlyReadsMemory(const Function *F) { ModRefBehavior MRB = getModRefBehavior(F); return MRB == DoesNotAccessMemory || MRB == OnlyReadsMemory; } /// getModRefInfo - Return information about whether or not an instruction may /// read or write the specified memory location. An instruction /// that doesn't read or write memory may be trivially LICM'd for example. ModRefResult getModRefInfo(const Instruction *I, const Location &Loc) { switch (I->getOpcode()) { case Instruction::VAArg: return getModRefInfo((const VAArgInst*)I, Loc); case Instruction::Load: return getModRefInfo((const LoadInst*)I, Loc); case Instruction::Store: return getModRefInfo((const StoreInst*)I, Loc); case Instruction::Call: return getModRefInfo((const CallInst*)I, Loc); case Instruction::Invoke: return getModRefInfo((const InvokeInst*)I,Loc); default: return NoModRef; } } /// getModRefInfo - A convenience wrapper. ModRefResult getModRefInfo(const Instruction *I, const Value *P, uint64_t Size) { return getModRefInfo(I, Location(P, Size)); } /// getModRefInfo (for call sites) - Return whether information about whether /// a particular call site modifies or reads the specified memory location. virtual ModRefResult getModRefInfo(ImmutableCallSite CS, const Location &Loc); /// getModRefInfo (for call sites) - A convenience wrapper. ModRefResult getModRefInfo(ImmutableCallSite CS, const Value *P, uint64_t Size) { return getModRefInfo(CS, Location(P, Size)); } /// getModRefInfo (for calls) - Return whether information about whether /// a particular call modifies or reads the specified memory location. ModRefResult getModRefInfo(const CallInst *C, const Location &Loc) { return getModRefInfo(ImmutableCallSite(C), Loc); } /// getModRefInfo (for calls) - A convenience wrapper. ModRefResult getModRefInfo(const CallInst *C, const Value *P, uint64_t Size) { return getModRefInfo(C, Location(P, Size)); } /// getModRefInfo (for invokes) - Return whether information about whether /// a particular invoke modifies or reads the specified memory location. ModRefResult getModRefInfo(const InvokeInst *I, const Location &Loc) { return getModRefInfo(ImmutableCallSite(I), Loc); } /// getModRefInfo (for invokes) - A convenience wrapper. ModRefResult getModRefInfo(const InvokeInst *I, const Value *P, uint64_t Size) { return getModRefInfo(I, Location(P, Size)); } /// getModRefInfo (for loads) - Return whether information about whether /// a particular load modifies or reads the specified memory location. ModRefResult getModRefInfo(const LoadInst *L, const Location &Loc); /// getModRefInfo (for loads) - A convenience wrapper. ModRefResult getModRefInfo(const LoadInst *L, const Value *P, uint64_t Size) { return getModRefInfo(L, Location(P, Size)); } /// getModRefInfo (for stores) - Return whether information about whether /// a particular store modifies or reads the specified memory location. ModRefResult getModRefInfo(const StoreInst *S, const Location &Loc); /// getModRefInfo (for stores) - A convenience wrapper. ModRefResult getModRefInfo(const StoreInst *S, const Value *P, uint64_t Size) { return getModRefInfo(S, Location(P, Size)); } /// getModRefInfo (for va_args) - Return whether information about whether /// a particular va_arg modifies or reads the specified memory location. ModRefResult getModRefInfo(const VAArgInst* I, const Location &Loc); /// getModRefInfo (for va_args) - A convenience wrapper. ModRefResult getModRefInfo(const VAArgInst* I, const Value* P, uint64_t Size) { return getModRefInfo(I, Location(P, Size)); } /// getModRefInfo - Return information about whether two call sites may refer /// to the same set of memory locations. See /// http://llvm.org/docs/AliasAnalysis.html#ModRefInfo /// for details. virtual ModRefResult getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2); //===--------------------------------------------------------------------===// /// Higher level methods for querying mod/ref information. /// /// canBasicBlockModify - Return true if it is possible for execution of the /// specified basic block to modify the value pointed to by Ptr. bool canBasicBlockModify(const BasicBlock &BB, const Location &Loc); /// canBasicBlockModify - A convenience wrapper. bool canBasicBlockModify(const BasicBlock &BB, const Value *P, uint64_t Size){ return canBasicBlockModify(BB, Location(P, Size)); } /// canInstructionRangeModify - Return true if it is possible for the /// execution of the specified instructions to modify the value pointed to by /// Ptr. The instructions to consider are all of the instructions in the /// range of [I1,I2] INCLUSIVE. I1 and I2 must be in the same basic block. bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2, const Location &Loc); /// canInstructionRangeModify - A convenience wrapper. bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2, const Value *Ptr, uint64_t Size) { return canInstructionRangeModify(I1, I2, Location(Ptr, Size)); } //===--------------------------------------------------------------------===// /// Methods that clients should call when they transform the program to allow /// alias analyses to update their internal data structures. Note that these /// methods may be called on any instruction, regardless of whether or not /// they have pointer-analysis implications. /// /// deleteValue - This method should be called whenever an LLVM Value is /// deleted from the program, for example when an instruction is found to be /// redundant and is eliminated. /// virtual void deleteValue(Value *V); /// copyValue - This method should be used whenever a preexisting value in the /// program is copied or cloned, introducing a new value. Note that analysis /// implementations should tolerate clients that use this method to introduce /// the same value multiple times: if the analysis already knows about a /// value, it should ignore the request. /// virtual void copyValue(Value *From, Value *To); /// replaceWithNewValue - This method is the obvious combination of the two /// above, and it provided as a helper to simplify client code. /// void replaceWithNewValue(Value *Old, Value *New) { copyValue(Old, New); deleteValue(Old); } }; /// isNoAliasCall - Return true if this pointer is returned by a noalias /// function. bool isNoAliasCall(const Value *V); /// isIdentifiedObject - Return true if this pointer refers to a distinct and /// identifiable object. This returns true for: /// Global Variables and Functions (but not Global Aliases) /// Allocas and Mallocs /// ByVal and NoAlias Arguments /// NoAlias returns /// bool isIdentifiedObject(const Value *V); } // End llvm namespace #endif