From: Chris Lattner Date: Wed, 26 Feb 2003 19:24:47 +0000 (+0000) Subject: Checkin of new alias analysis interface: X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=1c56b730a6313886076d7b293a126ae5576f5288;p=oota-llvm.git Checkin of new alias analysis interface: * Takes into account the size of the memory reference to determine aliasing. * Expose mod/ref information in a more consistent way git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5631 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/include/llvm/Analysis/AliasAnalysis.h b/include/llvm/Analysis/AliasAnalysis.h index 322dd547016..90713aeaf9e 100644 --- a/include/llvm/Analysis/AliasAnalysis.h +++ b/include/llvm/Analysis/AliasAnalysis.h @@ -2,24 +2,61 @@ // // 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. +// 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 -class Value; -class CallInst; -class InvokeInst; -class BasicBlock; -class Instruction; +#include "llvm/Support/CallSite.h" +class LoadInst; +class StoreInst; +class TargetData; +class AnalysisUsage; +class Pass; + +class AliasAnalysis { + const TargetData *TD; +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)) to make sure that + // TargetData is required by the pass. + virtual void getAnalysisUsage(AnalysisUsage &AU) const; + +public: + AliasAnalysis() : TD(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; } -struct AliasAnalysis { + //===--------------------------------------------------------------------===// + /// 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 @@ -27,29 +64,72 @@ struct AliasAnalysis { /// if (AA.alias(P1, P2)) { ... } /// to check to see if two pointers might alias. /// - enum Result { NoAlias = 0, MayAlias = 1, MustAlias = 2 }; + 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 Result alias(const Value *V1, const Value *V2) = 0; + virtual AliasResult alias(const Value *V1, unsigned V1Size, + const Value *V2, unsigned V2Size) { + return MayAlias; + } - /// canCallModify - Return a Result that indicates whether the specified - /// function call can modify the memory location pointed to by Ptr. + //===--------------------------------------------------------------------===// + /// Simple mod/ref information... /// - virtual Result canCallModify(const CallInst &CI, const Value *Ptr) = 0; - /// canInvokeModify - Return a Result that indicates whether the specified - /// function invoke can modify the memory location pointed to by Ptr. + /// ModRefResult - Represent the result of a mod/ref query. Mod and Ref are + /// bits which may be or'd together. /// - virtual Result canInvokeModify(const InvokeInst &I, const Value *Ptr) = 0; + enum ModRefResult { NoModRef = 0, Ref = 1, Mod = 2, ModRef = 3 }; + + /// 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) { + return ModRef; + } + + /// 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 they both read + /// some of the same memory, Mod if they both write to some of the same + /// memory, and ModRef if they read and write to the same memory. + /// + virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) { + return ModRef; + } + + /// 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(Instruction *I, Value *P, unsigned Size) { + switch (I->getOpcode()) { + 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; + } + } /// 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 *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 @@ -57,9 +137,7 @@ struct AliasAnalysis { /// 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); - - virtual ~AliasAnalysis(); // We want to be subclassed + const Value *Ptr, unsigned Size); }; #endif