return false;
}
+/// isEscapeSource - Return true if the pointer is one which would have
+/// been considered an escape by isNonEscapingLocalObject.
+static bool isEscapeSource(const Value *V) {
+ if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
+ return true;
+
+ // The load case works because isNonEscapingLocalObject considers all
+ // stores to be escapes (it passes true for the StoreCaptures argument
+ // to PointerMayBeCaptured).
+ if (isa<LoadInst>(V))
+ return true;
+
+ return false;
+}
/// isObjectSmallerThan - Return true if we can prove that the object specified
/// by V is smaller than Size.
} else if (const CallInst* CI = extractMallocCall(V)) {
if (!isArrayMalloc(V, &TD))
// The size is the argument to the malloc call.
- if (const ConstantInt* C = dyn_cast<ConstantInt>(CI->getOperand(1)))
+ if (const ConstantInt* C = dyn_cast<ConstantInt>(CI->getArgOperand(0)))
return (C->getZExtValue() < Size);
return false;
} else if (const Argument *A = dyn_cast<Argument>(V)) {
///
struct NoAA : public ImmutablePass, public AliasAnalysis {
static char ID; // Class identification, replacement for typeinfo
- NoAA() : ImmutablePass(&ID) {}
- explicit NoAA(void *PID) : ImmutablePass(PID) { }
+ NoAA() : ImmutablePass(ID) {}
+ explicit NoAA(char &PID) : ImmutablePass(PID) { }
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
}
return MayAlias;
}
- virtual void getArgumentAccesses(Function *F, CallSite CS,
- std::vector<PointerAccessInfo> &Info) {
- llvm_unreachable("This method may not be called on this function!");
- }
-
virtual bool pointsToConstantMemory(const Value *P) { return false; }
- virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size) {
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
+ const Value *P, unsigned Size) {
return ModRef;
}
- virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) {
return ModRef;
}
virtual void deleteValue(Value *V) {}
virtual void copyValue(Value *From, Value *To) {}
+
+ /// 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.
+ virtual void *getAdjustedAnalysisPointer(AnalysisID PI) {
+ if (PI == &AliasAnalysis::ID)
+ return (AliasAnalysis*)this;
+ return this;
+ }
};
} // End of anonymous namespace
// Register this pass...
char NoAA::ID = 0;
-static RegisterPass<NoAA>
-U("no-aa", "No Alias Analysis (always returns 'may' alias)", true, true);
-
-// Declare that we implement the AliasAnalysis interface
-static RegisterAnalysisGroup<AliasAnalysis> V(U);
+INITIALIZE_AG_PASS(NoAA, AliasAnalysis, "no-aa",
+ "No Alias Analysis (always returns 'may' alias)",
+ true, true, false);
ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
//===----------------------------------------------------------------------===//
-// BasicAA Pass
+// BasicAliasAnalysis Pass
//===----------------------------------------------------------------------===//
+#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 NULL;
+}
+
+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
+
namespace {
/// BasicAliasAnalysis - This is the default alias analysis implementation.
/// Because it doesn't chain to a previous alias analysis (like -no-aa), it
/// derives from the NoAA class.
struct BasicAliasAnalysis : public NoAA {
static char ID; // Class identification, replacement for typeinfo
- BasicAliasAnalysis() : NoAA(&ID) {}
+ BasicAliasAnalysis() : NoAA(ID) {}
+
AliasResult alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
- assert(VisitedPHIs.empty() && "VisitedPHIs must be cleared after use!");
+ assert(Visited.empty() && "Visited must be cleared after use!");
+ assert(notDifferentParent(V1, V2) &&
+ "BasicAliasAnalysis doesn't support interprocedural queries.");
AliasResult Alias = aliasCheck(V1, V1Size, V2, V2Size);
- VisitedPHIs.clear();
+ Visited.clear();
return Alias;
}
- ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
- ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
+ ModRefResult getModRefInfo(ImmutableCallSite CS,
+ const Value *P, unsigned Size);
+ ModRefResult getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2);
/// pointsToConstantMemory - Chase pointers until we find a (constant
/// global) or not.
bool pointsToConstantMemory(const Value *P);
+ /// 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.
+ virtual void *getAdjustedAnalysisPointer(AnalysisID PI) {
+ if (PI == &AliasAnalysis::ID)
+ return (AliasAnalysis*)this;
+ return this;
+ }
+
private:
- // VisitedPHIs - Track PHI nodes visited by a aliasCheck() call.
- SmallPtrSet<const Value*, 16> VisitedPHIs;
+ // Visited - Track instructions visited by a aliasPHI, aliasSelect(), and aliasGEP().
+ SmallPtrSet<const Value*, 16> Visited;
// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP
// instruction against another.
// Register this pass...
char BasicAliasAnalysis::ID = 0;
-static RegisterPass<BasicAliasAnalysis>
-X("basicaa", "Basic Alias Analysis (default AA impl)", false, true);
-
-// Declare that we implement the AliasAnalysis interface
-static RegisterAnalysisGroup<AliasAnalysis, true> Y(X);
+INITIALIZE_AG_PASS(BasicAliasAnalysis, AliasAnalysis, "basicaa",
+ "Basic Alias Analysis (default AA impl)",
+ false, true, true);
ImmutablePass *llvm::createBasicAliasAnalysisPass() {
return new BasicAliasAnalysis();
/// function, we really can't say much about this query. We do, however, use
/// simple "address taken" analysis on local objects.
AliasAnalysis::ModRefResult
-BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
+BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
+ const Value *P, unsigned Size) {
+ assert(notDifferentParent(CS.getInstruction(), P) &&
+ "AliasAnalysis query involving multiple functions!");
+
const Value *Object = P->getUnderlyingObject();
// If this is a tail call and P points to a stack location, we know that
// the current function not to the current function, and a tail callee
// may reference them.
if (isa<AllocaInst>(Object))
- if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
+ if (const CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
if (CI->isTailCall())
return NoModRef;
isNonEscapingLocalObject(Object)) {
bool PassedAsArg = false;
unsigned ArgNo = 0;
- for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
+ for (ImmutableCallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
CI != CE; ++CI, ++ArgNo) {
// Only look at the no-capture pointer arguments.
- if (!isa<PointerType>((*CI)->getType()) ||
+ if (!(*CI)->getType()->isPointerTy() ||
!CS.paramHasAttr(ArgNo+1, Attribute::NoCapture))
continue;
// is impossible to alias the pointer we're checking. If not, we have to
// assume that the call could touch the pointer, even though it doesn't
// escape.
- if (!isNoAlias(cast<Value>(CI), ~0U, P, ~0U)) {
+ if (!isNoAlias(cast<Value>(CI), UnknownSize, P, UnknownSize)) {
PassedAsArg = true;
break;
}
}
// Finally, handle specific knowledge of intrinsics.
- IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
+ const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction());
if (II == 0)
return AliasAnalysis::getModRefInfo(CS, P, Size);
default: break;
case Intrinsic::memcpy:
case Intrinsic::memmove: {
- unsigned Len = ~0U;
- if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3)))
+ unsigned Len = UnknownSize;
+ if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2)))
Len = LenCI->getZExtValue();
- Value *Dest = II->getOperand(1);
- Value *Src = II->getOperand(2);
+ Value *Dest = II->getArgOperand(0);
+ Value *Src = II->getArgOperand(1);
if (isNoAlias(Dest, Len, P, Size)) {
if (isNoAlias(Src, Len, P, Size))
return NoModRef;
case Intrinsic::memset:
// Since memset is 'accesses arguments' only, the AliasAnalysis base class
// will handle it for the variable length case.
- if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3))) {
+ if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getArgOperand(2))) {
unsigned Len = LenCI->getZExtValue();
- Value *Dest = II->getOperand(1);
+ Value *Dest = II->getArgOperand(0);
if (isNoAlias(Dest, Len, P, Size))
return NoModRef;
}
case Intrinsic::atomic_load_umax:
case Intrinsic::atomic_load_umin:
if (TD) {
- Value *Op1 = II->getOperand(1);
+ Value *Op1 = II->getArgOperand(0);
unsigned Op1Size = TD->getTypeStoreSize(Op1->getType());
if (isNoAlias(Op1, Op1Size, P, Size))
return NoModRef;
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
case Intrinsic::invariant_start: {
- unsigned PtrSize = cast<ConstantInt>(II->getOperand(1))->getZExtValue();
- if (isNoAlias(II->getOperand(2), PtrSize, P, Size))
+ unsigned PtrSize = cast<ConstantInt>(II->getArgOperand(0))->getZExtValue();
+ if (isNoAlias(II->getArgOperand(1), PtrSize, P, Size))
return NoModRef;
break;
}
case Intrinsic::invariant_end: {
- unsigned PtrSize = cast<ConstantInt>(II->getOperand(2))->getZExtValue();
- if (isNoAlias(II->getOperand(3), PtrSize, P, Size))
+ unsigned PtrSize = cast<ConstantInt>(II->getArgOperand(1))->getZExtValue();
+ if (isNoAlias(II->getArgOperand(2), PtrSize, P, Size))
return NoModRef;
break;
}
AliasAnalysis::ModRefResult
-BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
+BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) {
// If CS1 or CS2 are readnone, they don't interact.
ModRefBehavior CS1B = AliasAnalysis::getModRefBehavior(CS1);
if (CS1B == DoesNotAccessMemory) return NoModRef;
ModRefBehavior CS2B = AliasAnalysis::getModRefBehavior(CS2);
if (CS2B == DoesNotAccessMemory) return NoModRef;
- // If they both only read from memory, just return ref.
+ // If they both only read from memory, there is no dependence.
if (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory)
- return Ref;
+ return NoModRef;
+
+ AliasAnalysis::ModRefResult Mask = ModRef;
+
+ // If CS1 only reads memory, the only dependence on CS2 can be
+ // from CS1 reading memory written by CS2.
+ if (CS1B == OnlyReadsMemory)
+ Mask = ModRefResult(Mask & Ref);
+ // If CS2 only access memory through arguments, accumulate the mod/ref
+ // information from CS1's references to the memory referenced by
+ // CS2's arguments.
+ if (CS2B == AccessesArguments) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ for (ImmutableCallSite::arg_iterator
+ I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
+ R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask);
+ if (R == Mask)
+ break;
+ }
+ return R;
+ }
+
+ // If CS1 only accesses memory through arguments, check if CS2 references
+ // any of the memory referenced by CS1's arguments. If not, return NoModRef.
+ if (CS1B == AccessesArguments) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ for (ImmutableCallSite::arg_iterator
+ I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I)
+ if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) {
+ R = Mask;
+ break;
+ }
+ if (R == NoModRef)
+ return R;
+ }
+
// Otherwise, fall back to NoAA (mod+ref).
- return NoAA::getModRefInfo(CS1, CS2);
+ return ModRefResult(NoAA::getModRefInfo(CS1, CS2) & Mask);
}
-/// GetIndiceDifference - Dest and Src are the variable indices from two
+/// GetIndexDifference - 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.
-static void GetIndiceDifference(
+static void GetIndexDifference(
SmallVectorImpl<std::pair<const Value*, int64_t> > &Dest,
const SmallVectorImpl<std::pair<const Value*, int64_t> > &Src) {
if (Src.empty()) return;
const Value *V2, unsigned V2Size,
const Value *UnderlyingV1,
const Value *UnderlyingV2) {
+ // If this GEP has been visited before, we're on a use-def cycle.
+ // Such cycles are only valid when PHI nodes are involved or in unreachable
+ // code. The visitPHI function catches cycles containing PHIs, but there
+ // could still be a cycle without PHIs in unreachable code.
+ if (!Visited.insert(GEP1))
+ return MayAlias;
+
int64_t GEP1BaseOffset;
SmallVector<std::pair<const Value*, int64_t>, 4> GEP1VariableIndices;
// out if the indexes to the GEP tell us anything about the derived pointer.
if (const GEPOperator *GEP2 = dyn_cast<GEPOperator>(V2)) {
// Do the base pointers alias?
- AliasResult BaseAlias = aliasCheck(UnderlyingV1, ~0U, UnderlyingV2, ~0U);
+ AliasResult BaseAlias = aliasCheck(UnderlyingV1, UnknownSize,
+ UnderlyingV2, UnknownSize);
// If we get a No or May, then return it immediately, no amount of analysis
// will improve this situation.
// Subtract the GEP2 pointer from the GEP1 pointer to find out their
// symbolic difference.
GEP1BaseOffset -= GEP2BaseOffset;
- GetIndiceDifference(GEP1VariableIndices, GEP2VariableIndices);
+ GetIndexDifference(GEP1VariableIndices, GEP2VariableIndices);
} else {
// Check to see if these two pointers are related by the getelementptr
// pointer, we know they cannot alias.
// If both accesses are unknown size, we can't do anything useful here.
- if (V1Size == ~0U && V2Size == ~0U)
+ if (V1Size == UnknownSize && V2Size == UnknownSize)
return MayAlias;
- AliasResult R = aliasCheck(UnderlyingV1, ~0U, V2, V2Size);
+ AliasResult R = aliasCheck(UnderlyingV1, UnknownSize, V2, V2Size);
if (R != MustAlias)
// If V2 may alias GEP base pointer, conservatively returns MayAlias.
// If V2 is known not to alias GEP base pointer, then the two values
AliasAnalysis::AliasResult
BasicAliasAnalysis::aliasSelect(const SelectInst *SI, unsigned SISize,
const Value *V2, unsigned V2Size) {
+ // If this select has been visited before, we're on a use-def cycle.
+ // Such cycles are only valid when PHI nodes are involved or in unreachable
+ // code. The visitPHI function catches cycles containing PHIs, but there
+ // could still be a cycle without PHIs in unreachable code.
+ if (!Visited.insert(SI))
+ return MayAlias;
+
// If the values are Selects with the same condition, we can do a more precise
// check: just check for aliases between the values on corresponding arms.
if (const SelectInst *SI2 = dyn_cast<SelectInst>(V2))
// If both arms of the Select node NoAlias or MustAlias V2, then returns
// NoAlias / MustAlias. Otherwise, returns MayAlias.
AliasResult Alias =
- aliasCheck(SI->getTrueValue(), SISize, V2, V2Size);
+ aliasCheck(V2, V2Size, SI->getTrueValue(), SISize);
if (Alias == MayAlias)
return MayAlias;
+
+ // If V2 is visited, the recursive case will have been caught in the
+ // above aliasCheck call, so these subsequent calls to aliasCheck
+ // don't need to assume that V2 is being visited recursively.
+ Visited.erase(V2);
+
AliasResult ThisAlias =
- aliasCheck(SI->getFalseValue(), SISize, V2, V2Size);
+ aliasCheck(V2, V2Size, SI->getFalseValue(), SISize);
if (ThisAlias != Alias)
return MayAlias;
return Alias;
BasicAliasAnalysis::aliasPHI(const PHINode *PN, unsigned PNSize,
const Value *V2, unsigned V2Size) {
// The PHI node has already been visited, avoid recursion any further.
- if (!VisitedPHIs.insert(PN))
+ if (!Visited.insert(PN))
return MayAlias;
// If the values are PHIs in the same block, we can do a more precise
for (unsigned i = 1, e = V1Srcs.size(); i != e; ++i) {
Value *V = V1Srcs[i];
- // If V2 is a PHI, the recursive case will have been caught in the
+ // If V2 is visited, the recursive case will have been caught in the
// above aliasCheck call, so these subsequent calls to aliasCheck
// don't need to assume that V2 is being visited recursively.
- VisitedPHIs.erase(V2);
+ Visited.erase(V2);
AliasResult ThisAlias = aliasCheck(V2, V2Size, V, PNSize);
if (ThisAlias != Alias || ThisAlias == MayAlias)
AliasAnalysis::AliasResult
BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
+ // If either of the memory references is empty, it doesn't matter what the
+ // pointer values are.
+ if (V1Size == 0 || V2Size == 0)
+ return NoAlias;
+
// Strip off any casts if they exist.
V1 = V1->stripPointerCasts();
V2 = V2->stripPointerCasts();
// Are we checking for alias of the same value?
if (V1 == V2) return MustAlias;
- if (!isa<PointerType>(V1->getType()) || !isa<PointerType>(V2->getType()))
+ if (!V1->getType()->isPointerTy() || !V2->getType()->isPointerTy())
return NoAlias; // Scalars cannot alias each other
// Figure out what objects these things are pointing to if we can.
(isa<Constant>(O2) && isIdentifiedObject(O1) && !isa<Constant>(O1)))
return NoAlias;
- // Arguments can't alias with local allocations or noalias calls.
- if ((isa<Argument>(O1) && (isa<AllocaInst>(O2) || isNoAliasCall(O2))) ||
- (isa<Argument>(O2) && (isa<AllocaInst>(O1) || isNoAliasCall(O1))))
+ // Arguments can't alias with local allocations or noalias calls
+ // in the same function.
+ if (((isa<Argument>(O1) && (isa<AllocaInst>(O2) || isNoAliasCall(O2))) ||
+ (isa<Argument>(O2) && (isa<AllocaInst>(O1) || isNoAliasCall(O1)))))
return NoAlias;
// Most objects can't alias null.
- if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
- (isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
+ if ((isa<ConstantPointerNull>(O2) && isKnownNonNull(O1)) ||
+ (isa<ConstantPointerNull>(O1) && isKnownNonNull(O2)))
return NoAlias;
- }
+ // If one pointer is the result of a call/invoke or load and the other is a
+ // non-escaping local object within the same function, then we know the
+ // object couldn't escape to a point where the call could return it.
+ //
+ // Note that if the pointers are in different functions, there are a
+ // variety of complications. A call with a nocapture argument may still
+ // temporary store the nocapture argument's value in a temporary memory
+ // location if that memory location doesn't escape. Or it may pass a
+ // nocapture value to other functions as long as they don't capture it.
+ if (isEscapeSource(O1) && isNonEscapingLocalObject(O2))
+ return NoAlias;
+ if (isEscapeSource(O2) && isNonEscapingLocalObject(O1))
+ return NoAlias;
+ }
+
// If the size of one access is larger than the entire object on the other
// side, then we know such behavior is undefined and can assume no alias.
if (TD)
- if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, *TD)) ||
- (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, *TD)))
+ if ((V1Size != UnknownSize && isObjectSmallerThan(O2, V1Size, *TD)) ||
+ (V2Size != UnknownSize && isObjectSmallerThan(O1, V2Size, *TD)))
return NoAlias;
- // If one pointer is the result of a call/invoke or load and the other is a
- // non-escaping local object, then we know the object couldn't escape to a
- // point where the call could return it. The load case works because
- // isNonEscapingLocalObject considers all stores to be escapes (it
- // passes true for the StoreCaptures argument to PointerMayBeCaptured).
- if (O1 != O2) {
- if ((isa<CallInst>(O1) || isa<InvokeInst>(O1) || isa<LoadInst>(O1) ||
- isa<Argument>(O1)) &&
- isNonEscapingLocalObject(O2))
- return NoAlias;
- if ((isa<CallInst>(O2) || isa<InvokeInst>(O2) || isa<LoadInst>(O2) ||
- isa<Argument>(O2)) &&
- isNonEscapingLocalObject(O1))
- return NoAlias;
- }
-
// FIXME: This isn't aggressively handling alias(GEP, PHI) for example: if the
// GEP can't simplify, we don't even look at the PHI cases.
if (!isa<GEPOperator>(V1) && isa<GEPOperator>(V2)) {
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