//===- AliasAnalysis.cpp - Generic Alias Analysis Interface Implementation -==//
//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
// This file implements the generic AliasAnalysis interface which is used as the
// common interface used by all clients and implementations of alias analysis.
//
//
//===----------------------------------------------------------------------===//
-#include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Pass.h"
#include "llvm/BasicBlock.h"
-#include "llvm/Support/InstVisitor.h"
-#include "llvm/iMemory.h"
-#include "llvm/iOther.h"
-#include "llvm/Constants.h"
-#include "llvm/GlobalValue.h"
-#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/Type.h"
+#include "llvm/Target/TargetData.h"
+using namespace llvm;
// Register the AliasAnalysis interface, providing a nice name to refer to.
namespace {
RegisterAnalysisGroup<AliasAnalysis> Z("Alias Analysis");
}
+char AliasAnalysis::ID = 0;
-// CanModify - Define a little visitor class that is used to check to see if
-// arbitrary chunks of code can modify a specified pointer.
-//
-namespace {
- struct CanModify : public InstVisitor<CanModify, bool> {
- AliasAnalysis &AA;
- const Value *Ptr;
+//===----------------------------------------------------------------------===//
+// Default chaining methods
+//===----------------------------------------------------------------------===//
+
+AliasAnalysis::AliasResult
+AliasAnalysis::alias(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->alias(V1, V1Size, V2, V2Size);
+}
+
+void AliasAnalysis::getMustAliases(Value *P, std::vector<Value*> &RetVals) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->getMustAliases(P, RetVals);
+}
+
+bool AliasAnalysis::pointsToConstantMemory(const Value *P) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->pointsToConstantMemory(P);
+}
+
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(Function *F, CallSite CS,
+ std::vector<PointerAccessInfo> *Info) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->getModRefBehavior(F, CS, Info);
+}
+
+bool AliasAnalysis::hasNoModRefInfoForCalls() const {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->hasNoModRefInfoForCalls();
+}
+
+void AliasAnalysis::deleteValue(Value *V) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ AA->deleteValue(V);
+}
+
+void AliasAnalysis::copyValue(Value *From, Value *To) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ AA->copyValue(From, To);
+}
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
+ // FIXME: we can do better.
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+ return AA->getModRefInfo(CS1, CS2);
+}
+
+
+//===----------------------------------------------------------------------===//
+// AliasAnalysis non-virtual helper method implementation
+//===----------------------------------------------------------------------===//
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(LoadInst *L, Value *P, unsigned Size) {
+ return alias(L->getOperand(0), TD->getTypeSize(L->getType()),
+ P, Size) ? Ref : NoModRef;
+}
+
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(StoreInst *S, Value *P, unsigned Size) {
+ // If the stored address cannot alias the pointer in question, then the
+ // pointer cannot be modified by the store.
+ if (!alias(S->getOperand(1), TD->getTypeSize(S->getOperand(0)->getType()),
+ P, Size))
+ return NoModRef;
+
+ // If the pointer is a pointer to constant memory, then it could not have been
+ // modified by this store.
+ return pointsToConstantMemory(P) ? NoModRef : Mod;
+}
- CanModify(AliasAnalysis *aa, const Value *ptr)
- : AA(*aa), Ptr(ptr) {}
+AliasAnalysis::ModRefResult
+AliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
+ ModRefResult Mask = ModRef;
+ if (Function *F = CS.getCalledFunction()) {
+ ModRefBehavior MRB = getModRefBehavior(F, CallSite());
+ if (MRB == OnlyReadsMemory)
+ Mask = Ref;
+ else if (MRB == DoesNotAccessMemory)
+ return NoModRef;
+ }
+
+ if (!AA) return Mask;
- bool visitInvokeInst(InvokeInst &II) {
- return AA.canInvokeModify(II, Ptr);
- }
- bool visitCallInst(CallInst &CI) {
- return AA.canCallModify(CI, Ptr);
- }
- bool visitStoreInst(StoreInst &SI) {
- return AA.alias(Ptr, SI.getOperand(1));
- }
+ // If P points to a constant memory location, the call definitely could not
+ // modify the memory location.
+ if ((Mask & Mod) && AA->pointsToConstantMemory(P))
+ Mask = ModRefResult(Mask & ~Mod);
- // Other instructions do not alias anything.
- bool visitInstruction(Instruction &I) { return false; }
- };
+ return ModRefResult(Mask & AA->getModRefInfo(CS, P, Size));
}
// AliasAnalysis destructor: DO NOT move this to the header file for
//
AliasAnalysis::~AliasAnalysis() {}
-/// canBasicBlockModify - Return true if it is possible for execution of the
-/// specified basic block to modify the value pointed to by Ptr.
+/// setTargetData - Subclasses must call this method to initialize the
+/// AliasAnalysis interface before any other methods are called.
///
-bool AliasAnalysis::canBasicBlockModify(const BasicBlock &bb,
- const Value *Ptr) {
- CanModify CM(this, Ptr);
- BasicBlock &BB = const_cast<BasicBlock&>(bb);
+void AliasAnalysis::InitializeAliasAnalysis(Pass *P) {
+ TD = &P->getAnalysis<TargetData>();
+ AA = &P->getAnalysis<AliasAnalysis>();
+}
- for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
- if (CM.visit(I)) // Check every instruction in the basic block...
- return true;
+// getAnalysisUsage - All alias analysis implementations should invoke this
+// directly (using AliasAnalysis::getAnalysisUsage(AU)) to make sure that
+// TargetData is required by the pass.
+void AliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<TargetData>(); // All AA's need TargetData.
+ AU.addRequired<AliasAnalysis>(); // All AA's chain
+}
- return false;
+/// canBasicBlockModify - Return true if it is possible for execution of the
+/// specified basic block to modify the value pointed to by Ptr.
+///
+bool AliasAnalysis::canBasicBlockModify(const BasicBlock &BB,
+ const Value *Ptr, unsigned Size) {
+ return canInstructionRangeModify(BB.front(), BB.back(), Ptr, Size);
}
/// canInstructionRangeModify - Return true if it is possible for the execution
///
bool AliasAnalysis::canInstructionRangeModify(const Instruction &I1,
const Instruction &I2,
- const Value *Ptr) {
+ const Value *Ptr, unsigned Size) {
assert(I1.getParent() == I2.getParent() &&
"Instructions not in same basic block!");
- CanModify CM(this, Ptr);
BasicBlock::iterator I = const_cast<Instruction*>(&I1);
BasicBlock::iterator E = const_cast<Instruction*>(&I2);
++E; // Convert from inclusive to exclusive range.
- for (; I != E; ++I)
- if (CM.visit(I)) // Check every instruction in the basic block...
+ for (; I != E; ++I) // Check every instruction in range
+ if (getModRefInfo(I, const_cast<Value*>(Ptr), Size) & Mod)
return true;
-
return false;
}
-//===----------------------------------------------------------------------===//
-// BasicAliasAnalysis Pass Implementation
-//===----------------------------------------------------------------------===//
-//
-// Because of the way .a files work, the implementation of the
-// BasicAliasAnalysis class MUST be in the AliasAnalysis file itself, or else we
-// run the risk of AliasAnalysis being used, but the default implementation not
-// being linked into the tool that uses it. As such, we register and implement
-// the class here.
-//
-namespace {
- // Register this pass...
- RegisterOpt<BasicAliasAnalysis>
- X("basicaa", "Basic Alias Analysis (default AA impl)");
-
- // Declare that we implement the AliasAnalysis interface
- RegisterAnalysisGroup<AliasAnalysis, BasicAliasAnalysis, true> Y;
-} // End of anonymous namespace
-
-
-
-// hasUniqueAddress - Return true if the
-static inline bool hasUniqueAddress(const Value *V) {
- return isa<GlobalValue>(V) || isa<MallocInst>(V) || isa<AllocaInst>(V);
-}
-
-static const Value *getUnderlyingObject(const Value *V) {
- if (!isa<PointerType>(V->getType())) return 0;
-
- // If we are at some type of object... return it.
- if (hasUniqueAddress(V)) return V;
-
- // Traverse through different addressing mechanisms...
- if (const Instruction *I = dyn_cast<Instruction>(V)) {
- if (isa<CastInst>(I) || isa<GetElementPtrInst>(I))
- return getUnderlyingObject(I->getOperand(0));
- }
- return 0;
-}
-
-
-// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
-// as array references. Note that this function is heavily tail recursive.
-// Hopefully we have a smart C++ compiler. :)
-//
-AliasAnalysis::Result BasicAliasAnalysis::alias(const Value *V1,
- const Value *V2) {
- // Strip off constant pointer refs if they exist
- if (const ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(V1))
- V1 = CPR->getValue();
- if (const ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(V2))
- V2 = CPR->getValue();
-
- // Are we checking for alias of the same value?
- if (V1 == V2) return MustAlias;
-
- if ((!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType())) &&
- V1->getType() != Type::LongTy && V2->getType() != Type::LongTy)
- return NoAlias; // Scalars cannot alias each other
-
- // Strip off cast instructions...
- if (const Instruction *I = dyn_cast<CastInst>(V1))
- return alias(I->getOperand(0), V2);
- if (const Instruction *I = dyn_cast<CastInst>(V2))
- return alias(V1, I->getOperand(0));
-
- // If we have two gep instructions with identical indices, return an alias
- // result equal to the alias result of the original pointer...
- //
- if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(V1))
- if (const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(V2))
- if (GEP1->getNumOperands() == GEP2->getNumOperands() &&
- GEP1->getOperand(0)->getType() == GEP2->getOperand(0)->getType()) {
- if (std::equal(GEP1->op_begin()+1, GEP1->op_end(), GEP2->op_begin()+1))
- return alias(GEP1->getOperand(0), GEP2->getOperand(0));
-
- // If all of the indexes to the getelementptr are constant, but
- // different (well we already know they are different), then we know
- // that there cannot be an alias here if the two base pointers DO alias.
- //
- bool AllConstant = true;
- for (unsigned i = 1, e = GEP1->getNumOperands(); i != e; ++i)
- if (!isa<Constant>(GEP1->getOperand(i)) ||
- !isa<Constant>(GEP2->getOperand(i))) {
- AllConstant = false;
- break;
- }
-
- // If we are all constant, then look at where the the base pointers
- // alias. If they are known not to alias, then we are dealing with two
- // different arrays or something, so no alias is possible. If they are
- // known to be the same object, then we cannot alias because we are
- // indexing into a different part of the object. As usual, MayAlias
- // doesn't tell us anything.
- //
- if (AllConstant &&
- alias(GEP1->getOperand(0), GEP2->getOperand(0)) != MayAlias)
- return NoAlias;
- }
-
- // Figure out what objects these things are pointing to if we can...
- const Value *O1 = getUnderlyingObject(V1);
- const Value *O2 = getUnderlyingObject(V2);
-
- // Pointing at a discernable object?
- if (O1 && O2) {
- // If they are two different objects, we know that we have no alias...
- if (O1 != O2) return NoAlias;
-
- // If they are the same object, they we can look at the indexes. If they
- // index off of the object is the same for both pointers, they must alias.
- // If they are provably different, they must not alias. Otherwise, we can't
- // tell anything.
- } else if (O1 && isa<ConstantPointerNull>(V2)) {
- return NoAlias; // Unique values don't alias null
- } else if (O2 && isa<ConstantPointerNull>(V1)) {
- return NoAlias; // Unique values don't alias null
- }
-
- // Check to see if these two pointers are related by a getelementptr
- // instruction. If one pointer is a GEP with a non-zero index of the other
- // pointer, we know they cannot alias.
- //
- if (isa<GetElementPtrInst>(V2))
- std::swap(V1, V2);
-
- if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V1))
- if (GEP->getOperand(0) == V2) {
- // If there is at least one non-zero constant index, we know they cannot
- // alias.
- for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
- if (const Constant *C = dyn_cast<Constant>(GEP->getOperand(i)))
- if (!C->isNullValue())
- return NoAlias;
- }
-
- return MayAlias;
-}
+// Because of the way .a files work, we must force the BasicAA implementation to
+// be pulled in if the AliasAnalysis classes are pulled in. Otherwise we run
+// the risk of AliasAnalysis being used, but the default implementation not
+// being linked into the tool that uses it.
+DEFINING_FILE_FOR(AliasAnalysis)
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