#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CaptureTracking.h"
-#include "llvm/Analysis/MallocHelper.h"
+#include "llvm/Analysis/MallocFreeHelper.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Operator.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
-#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include <algorithm>
// Useful predicates
//===----------------------------------------------------------------------===//
-static const GEPOperator *isGEP(const Value *V) {
- return dyn_cast<GEPOperator>(V);
-}
-
static const Value *GetGEPOperands(const Value *V,
SmallVector<Value*, 16> &GEPOps) {
assert(GEPOps.empty() && "Expect empty list to populate!");
// Accumulate all of the chained indexes into the operand array
V = cast<User>(V)->getOperand(0);
- while (const User *G = isGEP(V)) {
+ while (const GEPOperator *G = dyn_cast<GEPOperator>(V)) {
if (!isa<Constant>(GEPOps[0]) || isa<GlobalValue>(GEPOps[0]) ||
!cast<Constant>(GEPOps[0])->isNullValue())
break; // Don't handle folding arbitrary pointer offsets yet...
/// object that never escapes from the function.
static bool isNonEscapingLocalObject(const Value *V) {
// If this is a local allocation, check to see if it escapes.
- if (isa<AllocationInst>(V) || isNoAliasCall(V))
+ if (isa<AllocaInst>(V) || isNoAliasCall(V))
return !PointerMayBeCaptured(V, false);
// If this is an argument that corresponds to a byval or noalias argument,
const Type *AccessTy;
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
AccessTy = GV->getType()->getElementType();
- } else if (const AllocationInst *AI = dyn_cast<AllocationInst>(V)) {
+ } else if (const AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
if (!AI->isArrayAllocation())
AccessTy = AI->getType()->getElementType();
else
/// implementations, in that it does not chain to a previous analysis. As
/// such it doesn't follow many of the rules that other alias analyses must.
///
- struct VISIBILITY_HIDDEN NoAA : public ImmutablePass, public AliasAnalysis {
+ struct NoAA : public ImmutablePass, public AliasAnalysis {
static char ID; // Class identification, replacement for typeinfo
NoAA() : ImmutablePass(&ID) {}
explicit NoAA(void *PID) : ImmutablePass(PID) { }
/// 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 VISIBILITY_HIDDEN BasicAliasAnalysis : public NoAA {
+ struct BasicAliasAnalysis : public NoAA {
static char ID; // Class identification, replacement for typeinfo
BasicAliasAnalysis() : NoAA(&ID) {}
AliasResult alias(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size);
+ const Value *V2, unsigned V2Size) {
+ assert(VisitedPHIs.empty() && "VisitedPHIs must be cleared after use!");
+ AliasResult Alias = aliasCheck(V1, V1Size, V2, V2Size);
+ VisitedPHIs.clear();
+ return Alias;
+ }
ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
bool pointsToConstantMemory(const Value *P);
private:
+ // VisitedPHIs - Track PHI nodes visited by a aliasCheck() call.
+ SmallPtrSet<const Value*, 16> VisitedPHIs;
+
+ // aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
+ // against another.
+ AliasResult aliasGEP(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size);
+
+ // aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI instruction
+ // against another.
+ AliasResult aliasPHI(const PHINode *PN, unsigned PNSize,
+ const Value *V2, unsigned V2Size);
+
+ /// aliasSelect - Disambiguate a Select instruction against another value.
+ AliasResult aliasSelect(const SelectInst *SI, unsigned SISize,
+ const Value *V2, unsigned V2Size);
+
+ AliasResult aliasCheck(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size);
+
// CheckGEPInstructions - Check two GEP instructions with known
// must-aliasing base pointers. This checks to see if the index expressions
// preclude the pointers from aliasing...
if (!passedAsArg)
return NoModRef;
}
+
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
+ switch (II->getIntrinsicID()) {
+ default: break;
+ case Intrinsic::memcpy:
+ case Intrinsic::memmove: {
+ unsigned Len = ~0U;
+ if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3)))
+ Len = LenCI->getZExtValue();
+ Value *Dest = II->getOperand(1);
+ Value *Src = II->getOperand(2);
+ if (alias(Dest, Len, P, Size) == NoAlias) {
+ if (alias(Src, Len, P, Size) == NoAlias)
+ return NoModRef;
+ return Ref;
+ }
+ }
+ break;
+ case Intrinsic::memset:
+ if (ConstantInt *LenCI = dyn_cast<ConstantInt>(II->getOperand(3))) {
+ unsigned Len = LenCI->getZExtValue();
+ Value *Dest = II->getOperand(1);
+ if (alias(Dest, Len, P, Size) == NoAlias)
+ return NoModRef;
+ }
+ break;
+ case Intrinsic::atomic_cmp_swap:
+ case Intrinsic::atomic_swap:
+ case Intrinsic::atomic_load_add:
+ case Intrinsic::atomic_load_sub:
+ case Intrinsic::atomic_load_and:
+ case Intrinsic::atomic_load_nand:
+ case Intrinsic::atomic_load_or:
+ case Intrinsic::atomic_load_xor:
+ case Intrinsic::atomic_load_max:
+ case Intrinsic::atomic_load_min:
+ case Intrinsic::atomic_load_umax:
+ case Intrinsic::atomic_load_umin:
+ if (TD) {
+ Value *Op1 = II->getOperand(1);
+ unsigned Op1Size = TD->getTypeStoreSize(Op1->getType());
+ if (alias(Op1, Op1Size, P, Size) == NoAlias)
+ return NoModRef;
+ }
+ break;
+ case Intrinsic::lifetime_start:
+ case Intrinsic::lifetime_end:
+ case Intrinsic::invariant_start: {
+ unsigned PtrSize = cast<ConstantInt>(II->getOperand(1))->getZExtValue();
+ if (alias(II->getOperand(2), PtrSize, P, Size) == NoAlias)
+ return NoModRef;
+ }
+ break;
+ case Intrinsic::invariant_end: {
+ unsigned PtrSize = cast<ConstantInt>(II->getOperand(2))->getZExtValue();
+ if (alias(II->getOperand(3), PtrSize, P, Size) == NoAlias)
+ return NoModRef;
+ }
+ break;
+ }
+ }
}
// The AliasAnalysis base class has some smarts, lets use them.
return NoAA::getModRefInfo(CS1, CS2);
}
-
-// alias - Provide a bunch of ad-hoc rules to disambiguate in common cases, such
-// as array references.
+// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
+// against another.
//
AliasAnalysis::AliasResult
-BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size) {
- // 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()))
- return NoAlias; // Scalars cannot alias each other
-
- // Figure out what objects these things are pointing to if we can.
- const Value *O1 = V1->getUnderlyingObject();
- const Value *O2 = V2->getUnderlyingObject();
-
- if (O1 != O2) {
- // If V1/V2 point to two different objects we know that we have no alias.
- if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
- return NoAlias;
-
- // Arguments can't alias with local allocations or noalias calls.
- if ((isa<Argument>(O1) && (isa<AllocationInst>(O2) || isNoAliasCall(O2))) ||
- (isa<Argument>(O2) && (isa<AllocationInst>(O1) || isNoAliasCall(O1))))
- return NoAlias;
-
- // Most objects can't alias null.
- if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
- (isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
- 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.
- LLVMContext &Context = V1->getContext();
- if (TD)
- if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, Context, *TD)) ||
- (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, Context, *TD)))
- return NoAlias;
-
- // If one pointer is the result of a call/invoke 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.
- if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
- isNonEscapingLocalObject(O2) && O1 != O2)
- return NoAlias;
- if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
- isNonEscapingLocalObject(O1) && O1 != O2)
- return NoAlias;
-
+BasicAliasAnalysis::aliasGEP(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
// If we have two gep instructions with must-alias'ing base pointers, figure
// out if the indexes to the GEP tell us anything about the derived pointer.
// Note that we also handle chains of getelementptr instructions as well as
// constant expression getelementptrs here.
//
- if (isGEP(V1) && isGEP(V2)) {
+ if (isa<GEPOperator>(V1) && isa<GEPOperator>(V2)) {
const User *GEP1 = cast<User>(V1);
const User *GEP2 = cast<User>(V2);
GEP1->getOperand(0)->getType() == GEP2->getOperand(0)->getType() &&
// All operands are the same, ignoring the base.
std::equal(GEP1->op_begin()+1, GEP1->op_end(), GEP2->op_begin()+1))
- return alias(GEP1->getOperand(0), V1Size, GEP2->getOperand(0), V2Size);
-
+ return aliasCheck(GEP1->getOperand(0), V1Size,
+ GEP2->getOperand(0), V2Size);
// Drill down into the first non-gep value, to test for must-aliasing of
// the base pointers.
- while (isGEP(GEP1->getOperand(0)) &&
+ while (isa<GEPOperator>(GEP1->getOperand(0)) &&
GEP1->getOperand(1) ==
Constant::getNullValue(GEP1->getOperand(1)->getType()))
GEP1 = cast<User>(GEP1->getOperand(0));
const Value *BasePtr1 = GEP1->getOperand(0);
- while (isGEP(GEP2->getOperand(0)) &&
+ while (isa<GEPOperator>(GEP2->getOperand(0)) &&
GEP2->getOperand(1) ==
Constant::getNullValue(GEP2->getOperand(1)->getType()))
GEP2 = cast<User>(GEP2->getOperand(0));
const Value *BasePtr2 = GEP2->getOperand(0);
// Do the base pointers alias?
- AliasResult BaseAlias = alias(BasePtr1, ~0U, BasePtr2, ~0U);
+ AliasResult BaseAlias = aliasCheck(BasePtr1, ~0U, BasePtr2, ~0U);
if (BaseAlias == NoAlias) return NoAlias;
if (BaseAlias == MustAlias) {
// If the base pointers alias each other exactly, check to see if we can
// instruction. If one pointer is a GEP with a non-zero index of the other
// pointer, we know they cannot alias.
//
- if (isGEP(V2)) {
- std::swap(V1, V2);
- std::swap(V1Size, V2Size);
+ if (V1Size == ~0U || V2Size == ~0U)
+ return MayAlias;
+
+ SmallVector<Value*, 16> GEPOperands;
+ const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
+
+ AliasResult R = aliasCheck(BasePtr, ~0U, 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
+ // cannot alias per GEP semantics: "A pointer value formed from a
+ // getelementptr instruction is associated with the addresses associated
+ // with the first operand of the getelementptr".
+ return R;
+
+ // If there is at least one non-zero constant index, we know they cannot
+ // alias.
+ bool ConstantFound = false;
+ bool AllZerosFound = true;
+ for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
+ if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
+ if (!C->isNullValue()) {
+ ConstantFound = true;
+ AllZerosFound = false;
+ break;
+ }
+ } else {
+ AllZerosFound = false;
+ }
+
+ // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
+ // the ptr, the end result is a must alias also.
+ if (AllZerosFound)
+ return MustAlias;
+
+ if (ConstantFound) {
+ if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
+ return NoAlias;
+
+ // Otherwise we have to check to see that the distance is more than
+ // the size of the argument... build an index vector that is equal to
+ // the arguments provided, except substitute 0's for any variable
+ // indexes we find...
+ if (TD &&
+ cast<PointerType>(BasePtr->getType())->getElementType()->isSized()) {
+ for (unsigned i = 0; i != GEPOperands.size(); ++i)
+ if (!isa<ConstantInt>(GEPOperands[i]))
+ GEPOperands[i] = Constant::getNullValue(GEPOperands[i]->getType());
+ int64_t Offset = TD->getIndexedOffset(BasePtr->getType(),
+ &GEPOperands[0],
+ GEPOperands.size());
+
+ if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
+ return NoAlias;
+ }
}
- if (V1Size != ~0U && V2Size != ~0U)
- if (isGEP(V1)) {
- SmallVector<Value*, 16> GEPOperands;
- const Value *BasePtr = GetGEPOperands(V1, GEPOperands);
-
- AliasResult R = alias(BasePtr, V1Size, V2, V2Size);
- if (R == MustAlias) {
- // If there is at least one non-zero constant index, we know they cannot
- // alias.
- bool ConstantFound = false;
- bool AllZerosFound = true;
- for (unsigned i = 0, e = GEPOperands.size(); i != e; ++i)
- if (const Constant *C = dyn_cast<Constant>(GEPOperands[i])) {
- if (!C->isNullValue()) {
- ConstantFound = true;
- AllZerosFound = false;
- break;
- }
- } else {
- AllZerosFound = false;
- }
+ return MayAlias;
+}
- // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
- // the ptr, the end result is a must alias also.
- if (AllZerosFound)
- return MustAlias;
+// aliasSelect - Provide a bunch of ad-hoc rules to disambiguate a Select instruction
+// against another.
+AliasAnalysis::AliasResult
+BasicAliasAnalysis::aliasSelect(const SelectInst *SI, unsigned SISize,
+ const Value *V2, unsigned V2Size) {
+ // 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 (SI->getCondition() == SI2->getCondition()) {
+ AliasResult Alias =
+ aliasCheck(SI->getTrueValue(), SISize,
+ SI2->getTrueValue(), V2Size);
+ if (Alias == MayAlias)
+ return MayAlias;
+ AliasResult ThisAlias =
+ aliasCheck(SI->getFalseValue(), SISize,
+ SI2->getFalseValue(), V2Size);
+ if (ThisAlias != Alias)
+ return MayAlias;
+ return Alias;
+ }
- if (ConstantFound) {
- if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
- return NoAlias;
+ // 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);
+ if (Alias == MayAlias)
+ return MayAlias;
+ AliasResult ThisAlias =
+ aliasCheck(SI->getFalseValue(), SISize, V2, V2Size);
+ if (ThisAlias != Alias)
+ return MayAlias;
+ return Alias;
+}
- // Otherwise we have to check to see that the distance is more than
- // the size of the argument... build an index vector that is equal to
- // the arguments provided, except substitute 0's for any variable
- // indexes we find...
- if (TD && cast<PointerType>(
- BasePtr->getType())->getElementType()->isSized()) {
- for (unsigned i = 0; i != GEPOperands.size(); ++i)
- if (!isa<ConstantInt>(GEPOperands[i]))
- GEPOperands[i] =
- Constant::getNullValue(GEPOperands[i]->getType());
- int64_t Offset =
- TD->getIndexedOffset(BasePtr->getType(),
- &GEPOperands[0],
- GEPOperands.size());
-
- if (Offset >= (int64_t)V2Size || Offset <= -(int64_t)V1Size)
- return NoAlias;
- }
- }
+// aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI instruction
+// against another.
+AliasAnalysis::AliasResult
+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))
+ return MayAlias;
+
+ // If the values are PHIs in the same block, we can do a more precise
+ // as well as efficient check: just check for aliases between the values
+ // on corresponding edges.
+ if (const PHINode *PN2 = dyn_cast<PHINode>(V2))
+ if (PN2->getParent() == PN->getParent()) {
+ AliasResult Alias =
+ aliasCheck(PN->getIncomingValue(0), PNSize,
+ PN2->getIncomingValueForBlock(PN->getIncomingBlock(0)),
+ V2Size);
+ if (Alias == MayAlias)
+ return MayAlias;
+ for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) {
+ AliasResult ThisAlias =
+ aliasCheck(PN->getIncomingValue(i), PNSize,
+ PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)),
+ V2Size);
+ if (ThisAlias != Alias)
+ return MayAlias;
}
+ return Alias;
}
+ SmallPtrSet<Value*, 4> UniqueSrc;
+ SmallVector<Value*, 4> V1Srcs;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ Value *PV1 = PN->getIncomingValue(i);
+ if (isa<PHINode>(PV1))
+ // If any of the source itself is a PHI, return MayAlias conservatively
+ // to avoid compile time explosion. The worst possible case is if both
+ // sides are PHI nodes. In which case, this is O(m x n) time where 'm'
+ // and 'n' are the number of PHI sources.
+ return MayAlias;
+ if (UniqueSrc.insert(PV1))
+ V1Srcs.push_back(PV1);
+ }
+
+ AliasResult Alias = aliasCheck(V2, V2Size, V1Srcs[0], PNSize);
+ // Early exit if the check of the first PHI source against V2 is MayAlias.
+ // Other results are not possible.
+ if (Alias == MayAlias)
+ return MayAlias;
+
+ // If all sources of the PHI node NoAlias or MustAlias V2, then returns
+ // NoAlias / MustAlias. Otherwise, returns MayAlias.
+ 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
+ // above aliasCheck call, so these subsequent calls to aliasCheck
+ // don't need to assume that V2 is being visited recursively.
+ VisitedPHIs.erase(V2);
+
+ AliasResult ThisAlias = aliasCheck(V2, V2Size, V, PNSize);
+ if (ThisAlias != Alias || ThisAlias == MayAlias)
+ return MayAlias;
+ }
+
+ return Alias;
+}
+
+// aliasCheck - Provide a bunch of ad-hoc rules to disambiguate in common cases,
+// such as array references.
+//
+AliasAnalysis::AliasResult
+BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
+ // 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()))
+ return NoAlias; // Scalars cannot alias each other
+
+ // Figure out what objects these things are pointing to if we can.
+ const Value *O1 = V1->getUnderlyingObject();
+ const Value *O2 = V2->getUnderlyingObject();
+
+ if (O1 != O2) {
+ // If V1/V2 point to two different objects we know that we have no alias.
+ if (isIdentifiedObject(O1) && isIdentifiedObject(O2))
+ 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))))
+ return NoAlias;
+
+ // Most objects can't alias null.
+ if ((isa<ConstantPointerNull>(V2) && isKnownNonNull(O1)) ||
+ (isa<ConstantPointerNull>(V1) && isKnownNonNull(O2)))
+ 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.
+ LLVMContext &Context = V1->getContext();
+ if (TD)
+ if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, Context, *TD)) ||
+ (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, Context, *TD)))
+ return NoAlias;
+
+ // If one pointer is the result of a call/invoke 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.
+ if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) &&
+ isNonEscapingLocalObject(O2) && O1 != O2)
+ return NoAlias;
+ if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) &&
+ isNonEscapingLocalObject(O1) && O1 != O2)
+ return NoAlias;
+
+ if (!isa<GEPOperator>(V1) && isa<GEPOperator>(V2)) {
+ std::swap(V1, V2);
+ std::swap(V1Size, V2Size);
+ }
+ if (isa<GEPOperator>(V1))
+ return aliasGEP(V1, V1Size, V2, V2Size);
+
+ if (isa<PHINode>(V2) && !isa<PHINode>(V1)) {
+ std::swap(V1, V2);
+ std::swap(V1Size, V2Size);
+ }
+ if (const PHINode *PN = dyn_cast<PHINode>(V1))
+ return aliasPHI(PN, V1Size, V2, V2Size);
+
+ if (isa<SelectInst>(V2) && !isa<SelectInst>(V1)) {
+ std::swap(V1, V2);
+ std::swap(V1Size, V2Size);
+ }
+ if (const SelectInst *S1 = dyn_cast<SelectInst>(V1))
+ return aliasSelect(S1, V1Size, V2, V2Size);
+
return MayAlias;
}
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