| //===- 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. If Size is 0, two pointers only alias if they |
| // are exactly equal. If size is greater than zero, but small, the two pointers |
| // alias if the areas pointed to overlap. If the size is very large (ie, ~0U), |
| // then the two pointers alias if they may be pointing to components of the same |
| // memory object. 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 "llvm/System/IncludeFile.h" |
| #include <vector> |
| |
| namespace llvm { |
| |
| class LoadInst; |
| class StoreInst; |
| class VAArgInst; |
| class TargetData; |
| class Pass; |
| class AnalysisUsage; |
| |
| class AliasAnalysis { |
| protected: |
| const TargetData *TD; |
| AliasAnalysis *AA; // Previous Alias Analysis to chain to. |
| |
| /// 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)) to make sure that |
| /// TargetData is required by the pass. |
| 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 |
| |
| /// getTargetData - Every alias analysis implementation depends on the size of |
| /// data items in the current Target. This provides a uniform way to handle |
| /// it. |
| /// |
| const TargetData &getTargetData() const { return *TD; } |
| |
| //===--------------------------------------------------------------------===// |
| /// Alias Queries... |
| /// |
| |
| /// 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. |
| /// |
| 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 Value *V1, unsigned V1Size, |
| const Value *V2, unsigned V2Size); |
| |
| /// getMustAliases - If there are any pointers known that must alias this |
| /// pointer, return them now. This allows alias-set based alias analyses to |
| /// perform a form a value numbering (which is exposed by load-vn). If an |
| /// alias analysis supports this, it should ADD any must aliased pointers to |
| /// the specified vector. |
| /// |
| virtual void getMustAliases(Value *P, std::vector<Value*> &RetVals); |
| |
| /// pointsToConstantMemory - If the specified pointer is known to point into |
| /// constant global memory, return true. This allows disambiguation of store |
| /// instructions from constant pointers. |
| /// |
| virtual bool pointsToConstantMemory(const Value *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 |
| // non-volatile and well known ways, but does not access any other memory. |
| // |
| // Clients may use the Info parameter of getModRefBehavior to get specific |
| // information about how pointer arguments are used. |
| AccessesArguments, |
| |
| // AccessesArgumentsAndGlobals - This function has accesses function |
| // arguments and global variables in non-volatile and well-known ways, but |
| // does not access any other memory. |
| // |
| // Clients may use the Info parameter of getModRefBehavior to get specific |
| // information about how pointer arguments are used. |
| 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 |
| }; |
| |
| /// PointerAccessInfo - This struct is used to return results for pointers, |
| /// globals, and the return value of a function. |
| struct PointerAccessInfo { |
| /// V - The value this record corresponds to. This may be an Argument for |
| /// the function, a GlobalVariable, or null, corresponding to the return |
| /// value for the function. |
| Value *V; |
| |
| /// ModRefInfo - Whether the pointer is loaded or stored to/from. |
| /// |
| ModRefResult ModRefInfo; |
| |
| /// AccessType - Specific fine-grained access information for the argument. |
| /// If none of these classifications is general enough, the |
| /// getModRefBehavior method should not return AccessesArguments*. If a |
| /// record is not returned for a particular argument, the argument is never |
| /// dead and never dereferenced. |
| enum AccessType { |
| /// ScalarAccess - The pointer is dereferenced. |
| /// |
| ScalarAccess, |
| |
| /// ArrayAccess - The pointer is indexed through as an array of elements. |
| /// |
| ArrayAccess, |
| |
| /// ElementAccess ?? P->F only? |
| |
| /// CallsThrough - Indirect calls are made through the specified function |
| /// pointer. |
| CallsThrough |
| }; |
| }; |
| |
| /// getModRefBehavior - Return the behavior when calling the given call site. |
| virtual ModRefBehavior getModRefBehavior(CallSite CS, |
| std::vector<PointerAccessInfo> *Info = 0); |
| |
| /// getModRefBehavior - Return the behavior when calling the given function. |
| /// For use when the call site is not known. |
| virtual ModRefBehavior getModRefBehavior(Function *F, |
| std::vector<PointerAccessInfo> *Info = 0); |
| |
| /// 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(CallSite 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(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(CallSite 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(Function *F) { |
| ModRefBehavior MRB = getModRefBehavior(F); |
| return MRB == DoesNotAccessMemory || MRB == OnlyReadsMemory; |
| } |
| |
| |
| /// getModRefInfo - Return information about whether or not an instruction may |
| /// read or write memory specified by the pointer operand. An instruction |
| /// that doesn't read or write memory may be trivially LICM'd for example. |
| |
| /// getModRefInfo (for call sites) - Return whether information about whether |
| /// a particular call site modifies or reads the memory specified by the |
| /// pointer. |
| /// |
| virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size); |
| |
| /// getModRefInfo - Return information about whether two call sites may refer |
| /// to the same set of memory locations. This function returns NoModRef if |
| /// the two calls refer to disjoint memory locations, Ref if CS1 reads memory |
| /// written by CS2, Mod if CS1 writes to memory read or written by CS2, or |
| /// ModRef if CS1 might read or write memory accessed by CS2. |
| /// |
| virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2); |
| |
| /// hasNoModRefInfoForCalls - Return true if the analysis has no mod/ref |
| /// information for pairs of function calls (other than "pure" and "const" |
| /// functions). This can be used by clients to avoid many pointless queries. |
| /// Remember that if you override this and chain to another analysis, you must |
| /// make sure that it doesn't have mod/ref info either. |
| /// |
| virtual bool hasNoModRefInfoForCalls() const; |
| |
| public: |
| /// Convenience functions... |
| ModRefResult getModRefInfo(LoadInst *L, Value *P, unsigned Size); |
| ModRefResult getModRefInfo(StoreInst *S, Value *P, unsigned Size); |
| ModRefResult getModRefInfo(CallInst *C, Value *P, unsigned Size) { |
| return getModRefInfo(CallSite(C), P, Size); |
| } |
| ModRefResult getModRefInfo(InvokeInst *I, Value *P, unsigned Size) { |
| return getModRefInfo(CallSite(I), P, Size); |
| } |
| ModRefResult getModRefInfo(VAArgInst* I, Value* P, unsigned Size) { |
| return AliasAnalysis::ModRef; |
| } |
| ModRefResult getModRefInfo(Instruction *I, Value *P, unsigned Size) { |
| switch (I->getOpcode()) { |
| case Instruction::VAArg: return getModRefInfo((VAArgInst*)I, P, Size); |
| case Instruction::Load: return getModRefInfo((LoadInst*)I, P, Size); |
| case Instruction::Store: return getModRefInfo((StoreInst*)I, P, Size); |
| case Instruction::Call: return getModRefInfo((CallInst*)I, P, Size); |
| case Instruction::Invoke: return getModRefInfo((InvokeInst*)I, P, Size); |
| default: return NoModRef; |
| } |
| } |
| |
| //===--------------------------------------------------------------------===// |
| /// 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 Value *P, unsigned 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 Value *Ptr, unsigned 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 |
| /// Allocas and Mallocs |
| /// ByVal and NoAlias Arguments |
| /// NoAlias returns |
| /// |
| bool isIdentifiedObject(const Value *V); |
| |
| } // End llvm namespace |
| |
| // Because of the way .a files work, we must force the BasicAA implementation to |
| // be pulled in if the AliasAnalysis header is included. Otherwise we run |
| // the risk of AliasAnalysis being used, but the default implementation not |
| // being linked into the tool that uses it. |
| FORCE_DEFINING_FILE_TO_BE_LINKED(AliasAnalysis) |
| FORCE_DEFINING_FILE_TO_BE_LINKED(BasicAliasAnalysis) |
| |
| #endif |