-//===- llvm/Analysis/BasicAliasAnalysis.h - Alias Analysis Impl -*- C++ -*-===//
+//===- BasicAliasAnalysis.h - Stateless, local Alias Analysis ---*- C++ -*-===//
//
-// This file defines the default implementation of the Alias Analysis interface
-// that simply implements a few identities (two different globals cannot alias,
-// etc), but otherwise does no analysis.
+// The LLVM Compiler Infrastructure
//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This is the interface for LLVM's primary stateless and local alias analysis.
+///
//===----------------------------------------------------------------------===//
-#ifndef LLVM_ANALYSIS_BASIC_ALIAS_ANALYSIS_H
-#define LLVM_ANALYSIS_BASIC_ALIAS_ANALYSIS_H
+#ifndef LLVM_ANALYSIS_BASICALIASANALYSIS_H
+#define LLVM_ANALYSIS_BASICALIASANALYSIS_H
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Pass.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/GetElementPtrTypeIterator.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/Support/ErrorHandling.h"
+
+namespace llvm {
+class AssumptionCache;
+class DominatorTree;
+class LoopInfo;
+
+/// This is the AA result object for the basic, local, and stateless alias
+/// analysis. It implements the AA query interface in an entirely stateless
+/// manner. As one consequence, it is never invalidated. While it does retain
+/// some storage, that is used as an optimization and not to preserve
+/// information from query to query.
+class BasicAAResult : public AAResultBase<BasicAAResult> {
+ friend AAResultBase<BasicAAResult>;
+
+ const DataLayout &DL;
+ AssumptionCache &AC;
+ DominatorTree *DT;
+ LoopInfo *LI;
+
+public:
+ BasicAAResult(const DataLayout &DL, const TargetLibraryInfo &TLI,
+ AssumptionCache &AC, DominatorTree *DT = nullptr,
+ LoopInfo *LI = nullptr)
+ : AAResultBase(TLI), DL(DL), AC(AC), DT(DT), LI(LI) {}
+
+ BasicAAResult(const BasicAAResult &Arg)
+ : AAResultBase(Arg), DL(Arg.DL), AC(Arg.AC), DT(Arg.DT), LI(Arg.LI) {}
+ BasicAAResult(BasicAAResult &&Arg)
+ : AAResultBase(std::move(Arg)), DL(Arg.DL), AC(Arg.AC), DT(Arg.DT),
+ LI(Arg.LI) {}
+
+ /// Handle invalidation events from the new pass manager.
+ ///
+ /// By definition, this result is stateless and so remains valid.
+ bool invalidate(Function &, const PreservedAnalyses &) { return false; }
+
+ AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB);
+
+ ModRefInfo getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc);
+
+ ModRefInfo getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2);
-struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
+ /// Chases pointers until we find a (constant global) or not.
+ bool pointsToConstantMemory(const MemoryLocation &Loc, bool OrLocal);
- // alias - This is the only method here that does anything interesting...
- //
- Result alias(const Value *V1, const Value *V2);
-
- /// canCallModify - We are not interprocedural, so we do nothing exciting.
+ /// Get the location associated with a pointer argument of a callsite.
+ ModRefInfo getArgModRefInfo(ImmutableCallSite CS, unsigned ArgIdx);
+
+ /// Returns the behavior when calling the given call site.
+ FunctionModRefBehavior getModRefBehavior(ImmutableCallSite CS);
+
+ /// Returns the behavior when calling the given function. For use when the
+ /// call site is not known.
+ FunctionModRefBehavior getModRefBehavior(const Function *F);
+
+private:
+ // A linear transformation of a Value; this class represents ZExt(SExt(V,
+ // SExtBits), ZExtBits) * Scale + Offset.
+ struct VariableGEPIndex {
+
+ // An opaque Value - we can't decompose this further.
+ const Value *V;
+
+ // We need to track what extensions we've done as we consider the same Value
+ // with different extensions as different variables in a GEP's linear
+ // expression;
+ // e.g.: if V == -1, then sext(x) != zext(x).
+ unsigned ZExtBits;
+ unsigned SExtBits;
+
+ int64_t Scale;
+
+ bool operator==(const VariableGEPIndex &Other) const {
+ return V == Other.V && ZExtBits == Other.ZExtBits &&
+ SExtBits == Other.SExtBits && Scale == Other.Scale;
+ }
+
+ bool operator!=(const VariableGEPIndex &Other) const {
+ return !operator==(Other);
+ }
+ };
+
+ /// Track alias queries to guard against recursion.
+ typedef std::pair<MemoryLocation, MemoryLocation> LocPair;
+ typedef SmallDenseMap<LocPair, AliasResult, 8> AliasCacheTy;
+ AliasCacheTy AliasCache;
+
+ /// Tracks phi nodes we have visited.
///
- Result canCallModify(const CallInst &CI, const Value *Ptr) {
- return MayAlias;
- }
-
- /// canInvokeModify - We are not interprocedural, so we do nothing exciting.
+ /// When interpret "Value" pointer equality as value equality we need to make
+ /// sure that the "Value" is not part of a cycle. Otherwise, two uses could
+ /// come from different "iterations" of a cycle and see different values for
+ /// the same "Value" pointer.
///
- Result canInvokeModify(const InvokeInst &I, const Value *Ptr) {
- return MayAlias; // We are not interprocedural
- }
+ /// The following example shows the problem:
+ /// %p = phi(%alloca1, %addr2)
+ /// %l = load %ptr
+ /// %addr1 = gep, %alloca2, 0, %l
+ /// %addr2 = gep %alloca2, 0, (%l + 1)
+ /// alias(%p, %addr1) -> MayAlias !
+ /// store %l, ...
+ SmallPtrSet<const BasicBlock *, 8> VisitedPhiBBs;
+
+ /// Tracks instructions visited by pointsToConstantMemory.
+ SmallPtrSet<const Value *, 16> Visited;
+
+ static const Value *
+ GetLinearExpression(const Value *V, APInt &Scale, APInt &Offset,
+ unsigned &ZExtBits, unsigned &SExtBits,
+ const DataLayout &DL, unsigned Depth, AssumptionCache *AC,
+ DominatorTree *DT, bool &NSW, bool &NUW);
+
+ static const Value *
+ DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
+ SmallVectorImpl<VariableGEPIndex> &VarIndices,
+ bool &MaxLookupReached, const DataLayout &DL,
+ AssumptionCache *AC, DominatorTree *DT);
+ /// \brief A Heuristic for aliasGEP that searches for a constant offset
+ /// between the variables.
+ ///
+ /// GetLinearExpression has some limitations, as generally zext(%x + 1)
+ /// != zext(%x) + zext(1) if the arithmetic overflows. GetLinearExpression
+ /// will therefore conservatively refuse to decompose these expressions.
+ /// However, we know that, for all %x, zext(%x) != zext(%x + 1), even if
+ /// the addition overflows.
+ bool
+ constantOffsetHeuristic(const SmallVectorImpl<VariableGEPIndex> &VarIndices,
+ uint64_t V1Size, uint64_t V2Size, int64_t BaseOffset,
+ AssumptionCache *AC, DominatorTree *DT);
+
+ bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2);
+
+ void GetIndexDifference(SmallVectorImpl<VariableGEPIndex> &Dest,
+ const SmallVectorImpl<VariableGEPIndex> &Src);
+
+ AliasResult aliasGEP(const GEPOperator *V1, uint64_t V1Size,
+ const AAMDNodes &V1AAInfo, const Value *V2,
+ uint64_t V2Size, const AAMDNodes &V2AAInfo,
+ const Value *UnderlyingV1, const Value *UnderlyingV2);
+
+ AliasResult aliasPHI(const PHINode *PN, uint64_t PNSize,
+ const AAMDNodes &PNAAInfo, const Value *V2,
+ uint64_t V2Size, const AAMDNodes &V2AAInfo);
+
+ AliasResult aliasSelect(const SelectInst *SI, uint64_t SISize,
+ const AAMDNodes &SIAAInfo, const Value *V2,
+ uint64_t V2Size, const AAMDNodes &V2AAInfo);
+
+ AliasResult aliasCheck(const Value *V1, uint64_t V1Size, AAMDNodes V1AATag,
+ const Value *V2, uint64_t V2Size, AAMDNodes V2AATag);
};
+/// Analysis pass providing a never-invalidated alias analysis result.
+class BasicAA {
+public:
+ typedef BasicAAResult Result;
+
+ /// \brief Opaque, unique identifier for this analysis pass.
+ static void *ID() { return (void *)&PassID; }
+
+ BasicAAResult run(Function &F, AnalysisManager<Function> *AM);
+
+ /// \brief Provide access to a name for this pass for debugging purposes.
+ static StringRef name() { return "BasicAliasAnalysis"; }
+
+private:
+ static char PassID;
+};
+
+/// Legacy wrapper pass to provide the BasicAAResult object.
+class BasicAAWrapperPass : public FunctionPass {
+ std::unique_ptr<BasicAAResult> Result;
+
+ virtual void anchor();
+
+public:
+ static char ID;
+
+ BasicAAWrapperPass();
+
+ BasicAAResult &getResult() { return *Result; }
+ const BasicAAResult &getResult() const { return *Result; }
+
+ bool runOnFunction(Function &F) override;
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+};
+
+FunctionPass *createBasicAAWrapperPass();
+
+/// A helper for the legacy pass manager to create a \c BasicAAResult object
+/// populated to the best of our ability for a particular function when inside
+/// of a \c ModulePass or a \c CallGraphSCCPass.
+BasicAAResult createLegacyPMBasicAAResult(Pass &P, Function &F);
+}
+
#endif
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