+//===- BasicAliasAnalysis.h - Stateless, local Alias Analysis ---*- C++ -*-===//
+//
+// 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_BASICALIASANALYSIS_H
+#define LLVM_ANALYSIS_BASICALIASANALYSIS_H
+
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Analysis/AliasAnalysis.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/Pass.h"
+#include "llvm/Support/ErrorHandling.h"
+
+namespace llvm {
+
+ /// BasicAliasAnalysis - This is the primary alias analysis implementation.
+ struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
+ static char ID; // Class identification, replacement for typeinfo
+
+#ifndef NDEBUG
+ static const Function *getParent(const Value *V) {
+ if (const Instruction *inst = dyn_cast<Instruction>(V))
+ return inst->getParent()->getParent();
+
+ if (const Argument *arg = dyn_cast<Argument>(V))
+ return arg->getParent();
+
+ return nullptr;
+ }
+
+ static bool notDifferentParent(const Value *O1, const Value *O2) {
+
+ const Function *F1 = getParent(O1);
+ const Function *F2 = getParent(O2);
+
+ return !F1 || !F2 || F1 == F2;
+ }
+#endif
+
+ BasicAliasAnalysis() : ImmutablePass(ID) {
+ initializeBasicAliasAnalysisPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool doInitialization(Module &M) override;
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<AliasAnalysis>();
+ AU.addRequired<AssumptionCacheTracker>();
+ AU.addRequired<TargetLibraryInfoWrapperPass>();
+ }
+
+ AliasResult alias(const MemoryLocation &LocA,
+ const MemoryLocation &LocB) override {
+ assert(AliasCache.empty() && "AliasCache must be cleared after use!");
+ assert(notDifferentParent(LocA.Ptr, LocB.Ptr) &&
+ "BasicAliasAnalysis doesn't support interprocedural queries.");
+ AliasResult Alias = aliasCheck(LocA.Ptr, LocA.Size, LocA.AATags,
+ LocB.Ptr, LocB.Size, LocB.AATags);
+ // AliasCache rarely has more than 1 or 2 elements, always use
+ // shrink_and_clear so it quickly returns to the inline capacity of the
+ // SmallDenseMap if it ever grows larger.
+ // FIXME: This should really be shrink_to_inline_capacity_and_clear().
+ AliasCache.shrink_and_clear();
+ VisitedPhiBBs.clear();
+ return Alias;
+ }
+
+ ModRefInfo getModRefInfo(ImmutableCallSite CS,
+ const MemoryLocation &Loc) override;
+
+ ModRefInfo getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) override;
+
+ /// pointsToConstantMemory - Chase pointers until we find a (constant
+ /// global) or not.
+ bool pointsToConstantMemory(const MemoryLocation &Loc,
+ bool OrLocal) override;
+
+ /// Get the location associated with a pointer argument of a callsite.
+ ModRefInfo getArgModRefInfo(ImmutableCallSite CS, unsigned ArgIdx) override;
+
+ /// getModRefBehavior - Return the behavior when calling the given
+ /// call site.
+ FunctionModRefBehavior getModRefBehavior(ImmutableCallSite CS) override;
+
+ /// getModRefBehavior - Return the behavior when calling the given function.
+ /// For use when the call site is not known.
+ FunctionModRefBehavior getModRefBehavior(const Function *F) override;
+
+ /// getAdjustedAnalysisPointer - This method is used when a pass implements
+ /// an analysis interface through multiple inheritance. If needed, it
+ /// should override this to adjust the this pointer as needed for the
+ /// specified pass info.
+ void *getAdjustedAnalysisPointer(const void *ID) override {
+ if (ID == &AliasAnalysis::ID)
+ return (AliasAnalysis*)this;
+ return this;
+ }
+
+ private:
+ enum ExtensionKind {
+ EK_NotExtended,
+ EK_SignExt,
+ EK_ZeroExt
+ };
+
+ struct VariableGEPIndex {
+ const Value *V;
+ ExtensionKind Extension;
+ int64_t Scale;
+
+ bool operator==(const VariableGEPIndex &Other) const {
+ return V == Other.V && Extension == Other.Extension &&
+ Scale == Other.Scale;
+ }
+
+ bool operator!=(const VariableGEPIndex &Other) const {
+ return !operator==(Other);
+ }
+ };
+
+ // AliasCache - Track alias queries to guard against recursion.
+ typedef std::pair<MemoryLocation, MemoryLocation> LocPair;
+ typedef SmallDenseMap<LocPair, AliasResult, 8> AliasCacheTy;
+ AliasCacheTy AliasCache;
+
+ /// \brief Track phi nodes we have visited. 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.
+ /// 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;
+
+ // Visited - Track instructions visited by pointsToConstantMemory.
+ SmallPtrSet<const Value*, 16> Visited;
+
+ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
+ ExtensionKind &Extension,
+ const DataLayout &DL, unsigned Depth,
+ AssumptionCache *AC, DominatorTree *DT);
+
+ static const Value *
+ DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
+ SmallVectorImpl<VariableGEPIndex> &VarIndices,
+ bool &MaxLookupReached, const DataLayout &DL,
+ AssumptionCache *AC, DominatorTree *DT);
+
+ /// \brief Check whether two Values can be considered equivalent.
+ ///
+ /// In addition to pointer equivalence of \p V1 and \p V2 this checks
+ /// whether they can not be part of a cycle in the value graph by looking at
+ /// all visited phi nodes an making sure that the phis cannot reach the
+ /// value. We have to do this because we are looking through phi nodes (That
+ /// is we say noalias(V, phi(VA, VB)) if noalias(V, VA) and noalias(V, VB).
+ bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2);
+
+ /// \brief Dest and Src are the variable indices from two decomposed
+ /// GetElementPtr instructions GEP1 and GEP2 which have common base
+ /// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic
+ /// difference between the two pointers.
+ void GetIndexDifference(SmallVectorImpl<VariableGEPIndex> &Dest,
+ const SmallVectorImpl<VariableGEPIndex> &Src);
+
+ // aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP
+ // instruction against another.
+ 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);
+
+ // aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI
+ // instruction against another.
+ AliasResult aliasPHI(const PHINode *PN, uint64_t PNSize,
+ const AAMDNodes &PNAAInfo,
+ const Value *V2, uint64_t V2Size,
+ const AAMDNodes &V2AAInfo);
+
+ /// aliasSelect - Disambiguate a Select instruction against another value.
+ 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);
+ };
+
+
+ //===--------------------------------------------------------------------===//
+ //
+ // createBasicAliasAnalysisPass - This pass implements the stateless alias
+ // analysis.
+ //
+ ImmutablePass *createBasicAliasAnalysisPass();
+
+}
+
+#endif
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