-//===- llvm/Analysis/BasicAliasAnalysis.h - Alias Analysis Impl -*- C++ -*-===//
+//===- BasicAliasAnalysis.cpp - Local Alias Analysis Impl -----------------===//
+//
+// 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 defines the default implementation of the Alias Analysis interface
// that simply implements a few identities (two different globals cannot alias,
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Pass.h"
-#include "llvm/iMemory.h"
+#include "llvm/Argument.h"
#include "llvm/iOther.h"
#include "llvm/ConstantHandling.h"
#include "llvm/GlobalValue.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/Support/GetElementPtrTypeIterator.h"
+using namespace llvm;
// Make sure that anything that uses AliasAnalysis pulls in this file...
-void BasicAAStub() {}
+void llvm::BasicAAStub() {}
-class GetElementPtrInst;
namespace {
struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
AliasResult alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size);
private:
- // CheckGEPInstructions - Check two GEP instructions of compatible types and
- // equal number of arguments. This checks to see if the index expressions
+ // CheckGEPInstructions - Check two GEP instructions with known
+ // must-aliasing base pointers. This checks to see if the index expressions
// preclude the pointers from aliasing...
- AliasResult CheckGEPInstructions(GetElementPtrInst *GEP1, unsigned G1Size,
- GetElementPtrInst *GEP2, unsigned G2Size);
+ AliasResult
+ CheckGEPInstructions(const Type* BasePtr1Ty, std::vector<Value*> &GEP1Ops,
+ unsigned G1Size,
+ const Type *BasePtr2Ty, std::vector<Value*> &GEP2Ops,
+ unsigned G2Size);
};
// Register this pass...
InitializeAliasAnalysis(this);
}
-
-
-// hasUniqueAddress - Return true if the
+// hasUniqueAddress - Return true if the specified value points to something
+// with a unique, discernable, address.
static inline bool hasUniqueAddress(const Value *V) {
- return isa<GlobalValue>(V) || isa<MallocInst>(V) || isa<AllocaInst>(V);
+ return isa<GlobalValue>(V) || isa<AllocationInst>(V);
}
+// getUnderlyingObject - This traverses the use chain to figure out what object
+// the specified value points to. If the value points to, or is derived from, a
+// unique object or an argument, return it.
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;
+ if (hasUniqueAddress(V) || isa<Argument>(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));
+ } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
+ if (CE->getOpcode() == Instruction::Cast ||
+ CE->getOpcode() == Instruction::GetElementPtr)
+ return getUnderlyingObject(CE->getOperand(0));
+ } else if (const ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(V)) {
+ return CPR->getValue();
}
return 0;
}
+static const User *isGEP(const Value *V) {
+ if (isa<GetElementPtrInst>(V) ||
+ (isa<ConstantExpr>(V) &&
+ cast<ConstantExpr>(V)->getOpcode() == Instruction::GetElementPtr))
+ return cast<User>(V);
+ 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.
AliasAnalysis::AliasResult
BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
+ // Strip off any constant expression casts if they exist
+ if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V1))
+ if (CE->getOpcode() == Instruction::Cast)
+ V1 = CE->getOperand(0);
+ if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V2))
+ if (CE->getOpcode() == Instruction::Cast)
+ V2 = CE->getOperand(0);
+
// Strip off constant pointer refs if they exist
if (const ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(V1))
V1 = CPR->getValue();
const Value *O1 = getUnderlyingObject(V1);
const Value *O2 = getUnderlyingObject(V2);
- // Pointing at a discernable object?
+ // Pointing at a discernible object?
if (O1 && O2) {
- // If they are two different objects, we know that we have no alias...
- if (O1 != O2) return NoAlias;
+ if (isa<Argument>(O1)) {
+ // Incoming argument cannot alias locally allocated object!
+ if (isa<AllocationInst>(O2)) return NoAlias;
+ // Otherwise, nothing is known...
+ } else if (isa<Argument>(O2)) {
+ // Incoming argument cannot alias locally allocated object!
+ if (isa<AllocationInst>(O1)) return NoAlias;
+ // Otherwise, nothing is known...
+ } else {
+ // 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)) {
+ } else if (O1 && !isa<Argument>(O1) && isa<ConstantPointerNull>(V2)) {
return NoAlias; // Unique values don't alias null
- } else if (O2 && isa<ConstantPointerNull>(V1)) {
+ } else if (O2 && !isa<Argument>(O2) && isa<ConstantPointerNull>(V1)) {
return NoAlias; // Unique values don't alias null
}
- // If we have two gep instructions with identical indices, return an alias
- // result equal to the alias result of the original pointer...
+ // 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 (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()) {
- AliasResult GAlias =
- CheckGEPInstructions((GetElementPtrInst*)GEP1, V1Size,
- (GetElementPtrInst*)GEP2, V2Size);
- if (GAlias != MayAlias)
- return GAlias;
+ if (isGEP(V1) && isGEP(V2)) {
+ // Drill down into the first non-gep value, to test for must-aliasing of
+ // the base pointers.
+ const Value *BasePtr1 = V1, *BasePtr2 = V2;
+ do {
+ BasePtr1 = cast<User>(BasePtr1)->getOperand(0);
+ } while (isGEP(BasePtr1) &&
+ cast<User>(BasePtr1)->getOperand(1) ==
+ Constant::getNullValue(cast<User>(BasePtr1)->getOperand(1)->getType()));
+ do {
+ BasePtr2 = cast<User>(BasePtr2)->getOperand(0);
+ } while (isGEP(BasePtr2) &&
+ cast<User>(BasePtr2)->getOperand(1) ==
+ Constant::getNullValue(cast<User>(BasePtr2)->getOperand(1)->getType()));
+
+ // Do the base pointers alias?
+ AliasResult BaseAlias = alias(BasePtr1, V1Size, BasePtr2, V2Size);
+ if (BaseAlias == NoAlias) return NoAlias;
+ if (BaseAlias == MustAlias) {
+ // If the base pointers alias each other exactly, check to see if we can
+ // figure out anything about the resultant pointers, to try to prove
+ // non-aliasing.
+
+ // Collect all of the chained GEP operands together into one simple place
+ std::vector<Value*> GEP1Ops(cast<User>(V1)->op_begin()+1,
+ cast<User>(V1)->op_end());
+ std::vector<Value*> GEP2Ops(cast<User>(V2)->op_begin()+1,
+ cast<User>(V2)->op_end());
+
+ // Accumulate all of the chained indexes into the operand arrays
+ BasePtr1 = cast<User>(V1)->getOperand(0);
+ BasePtr2 = cast<User>(V2)->getOperand(0);
+ while (const User *G = isGEP(BasePtr1)) {
+ if (!isa<Constant>(GEP1Ops[0]) ||
+ !cast<Constant>(GEP1Ops[0])->isNullValue())
+ break; // Don't handle folding arbitrary pointer offsets yet...
+ GEP1Ops.erase(GEP1Ops.begin());
+ GEP1Ops.insert(GEP1Ops.begin(), G->op_begin()+1, G->op_end());
+ BasePtr1 = G->getOperand(0);
}
+ while (const User *G = isGEP(BasePtr2)) {
+ if (!isa<Constant>(GEP2Ops[0]) ||
+ !cast<Constant>(GEP2Ops[0])->isNullValue())
+ break; // Don't handle folding arbitrary pointer offsets yet...
+ GEP2Ops.erase(GEP2Ops.begin());
+ GEP2Ops.insert(GEP2Ops.begin(), G->op_begin()+1, G->op_end());
+ BasePtr2 = G->getOperand(0);
+ }
+
+ AliasResult GAlias =
+ CheckGEPInstructions(BasePtr1->getType(), GEP1Ops, V1Size,
+ BasePtr2->getType(), GEP2Ops, V2Size);
+ if (GAlias != MayAlias)
+ return GAlias;
+ }
+ }
// 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
std::swap(V1Size, V2Size);
}
- 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())
+ if (V1Size != ~0U && V2Size != ~0U)
+ if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V1)) {
+ AliasResult R = alias(GEP->getOperand(0), 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 = 1, e = GEP->getNumOperands(); i != e; ++i)
+ if (const Constant *C = dyn_cast<Constant>(GEP->getOperand(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...
+
+ std::vector<Value*> Indices;
+ Indices.reserve(GEP->getNumOperands()-1);
+ for (unsigned i = 1; i != GEP->getNumOperands(); ++i)
+ if (const Constant *C = dyn_cast<Constant>(GEP->getOperand(i)))
+ Indices.push_back((Value*)C);
+ else
+ Indices.push_back(Constant::getNullValue(Type::LongTy));
+ const Type *Ty = GEP->getOperand(0)->getType();
+ int Offset = getTargetData().getIndexedOffset(Ty, Indices);
+ if (Offset >= (int)V2Size || Offset <= -(int)V1Size)
return NoAlias;
+ }
+ }
}
-
+
return MayAlias;
}
-// CheckGEPInstructions - Check two GEP instructions of compatible types and
-// equal number of arguments. This checks to see if the index expressions
-// preclude the pointers from aliasing...
-//
-AliasAnalysis::AliasResult
-BasicAliasAnalysis::CheckGEPInstructions(GetElementPtrInst *GEP1, unsigned G1S,
- GetElementPtrInst *GEP2, unsigned G2S){
- // Do the base pointers alias?
- AliasResult BaseAlias = alias(GEP1->getOperand(0), G1S,
- GEP2->getOperand(0), G2S);
- if (BaseAlias != MustAlias) // No or May alias: We cannot add anything...
- return BaseAlias;
-
- // Find the (possibly empty) initial sequence of equal values...
- unsigned NumGEPOperands = GEP1->getNumOperands();
- unsigned UnequalOper = 1;
- while (UnequalOper != NumGEPOperands &&
- GEP1->getOperand(UnequalOper) == GEP2->getOperand(UnequalOper))
+/// CheckGEPInstructions - Check two GEP instructions with known must-aliasing
+/// base pointers. This checks to see if the index expressions preclude the
+/// pointers from aliasing...
+AliasAnalysis::AliasResult BasicAliasAnalysis::
+CheckGEPInstructions(const Type* BasePtr1Ty, std::vector<Value*> &GEP1Ops,
+ unsigned G1S,
+ const Type *BasePtr2Ty, std::vector<Value*> &GEP2Ops,
+ unsigned G2S) {
+ // We currently can't handle the case when the base pointers have different
+ // primitive types. Since this is uncommon anyway, we are happy being
+ // extremely conservative.
+ if (BasePtr1Ty != BasePtr2Ty)
+ return MayAlias;
+
+ const Type *GEPPointerTy = BasePtr1Ty;
+
+ // Find the (possibly empty) initial sequence of equal values... which are not
+ // necessarily constants.
+ unsigned NumGEP1Operands = GEP1Ops.size(), NumGEP2Operands = GEP2Ops.size();
+ unsigned MinOperands = std::min(NumGEP1Operands, NumGEP2Operands);
+ unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands);
+ unsigned UnequalOper = 0;
+ while (UnequalOper != MinOperands &&
+ GEP1Ops[UnequalOper] == GEP2Ops[UnequalOper]) {
+ // Advance through the type as we go...
++UnequalOper;
+ if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
+ BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[UnequalOper-1]);
+ else {
+ // If all operands equal each other, then the derived pointers must
+ // alias each other...
+ BasePtr1Ty = 0;
+ assert(UnequalOper == NumGEP1Operands && UnequalOper == NumGEP2Operands &&
+ "Ran out of type nesting, but not out of operands?");
+ return MustAlias;
+ }
+ }
+
+ // If we have seen all constant operands, and run out of indexes on one of the
+ // getelementptrs, check to see if the tail of the leftover one is all zeros.
+ // If so, return mustalias.
+ if (UnequalOper == MinOperands && MinOperands != MaxOperands) {
+ if (GEP1Ops.size() < GEP2Ops.size()) std::swap(GEP1Ops, GEP2Ops);
- // If all operands equal each other, then the derived pointers must
- // alias each other...
- if (UnequalOper == NumGEPOperands) return MustAlias;
+ bool AllAreZeros = true;
+ for (unsigned i = UnequalOper; i != MaxOperands; ++i)
+ if (!isa<Constant>(GEP1Ops[i]) ||
+ !cast<Constant>(GEP1Ops[i])->isNullValue()) {
+ AllAreZeros = false;
+ break;
+ }
+ if (AllAreZeros) return MustAlias;
+ }
+
// So now we know that the indexes derived from the base pointers,
// which are known to alias, are different. We can still determine a
//
unsigned SizeMax = std::max(G1S, G2S);
if (SizeMax == ~0U) return MayAlias; // Avoid frivolous work...
-
+
// Scan for the first operand that is constant and unequal in the
// two getelemenptrs...
unsigned FirstConstantOper = UnequalOper;
- for (; FirstConstantOper != NumGEPOperands; ++FirstConstantOper) {
- const Value *G1Oper = GEP1->getOperand(FirstConstantOper);
- const Value *G2Oper = GEP2->getOperand(FirstConstantOper);
+ for (; FirstConstantOper != MinOperands; ++FirstConstantOper) {
+ const Value *G1Oper = GEP1Ops[FirstConstantOper];
+ const Value *G2Oper = GEP2Ops[FirstConstantOper];
+
if (G1Oper != G2Oper && // Found non-equal constant indexes...
isa<Constant>(G1Oper) && isa<Constant>(G2Oper)) {
- // Make sure they are comparable... and make sure the GEP with
- // the smaller leading constant is GEP1.
- ConstantBool *Compare =
- *cast<Constant>(GEP1->getOperand(FirstConstantOper)) >
- *cast<Constant>(GEP2->getOperand(FirstConstantOper));
+ // Make sure they are comparable (ie, not constant expressions)... and
+ // make sure the GEP with the smaller leading constant is GEP1.
+ ConstantBool *Compare = *cast<Constant>(G1Oper) > *cast<Constant>(G2Oper);
if (Compare) { // If they are comparable...
if (Compare->getValue())
- std::swap(GEP1, GEP2); // Make GEP1 < GEP2
+ std::swap(GEP1Ops, GEP2Ops); // Make GEP1 < GEP2
break;
}
}
+ BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(G1Oper);
}
- // No constant operands, we cannot tell anything...
- if (FirstConstantOper == NumGEPOperands) return MayAlias;
+ // No shared constant operands, and we ran out of common operands. At this
+ // point, the GEP instructions have run through all of their operands, and we
+ // haven't found evidence that there are any deltas between the GEP's.
+ // However, one GEP may have more operands than the other. If this is the
+ // case, there may still be hope. This this now.
+ if (FirstConstantOper == MinOperands) {
+ // Make GEP1Ops be the longer one if there is a longer one.
+ if (GEP1Ops.size() < GEP2Ops.size())
+ std::swap(GEP1Ops, GEP2Ops);
+
+ // Is there anything to check?
+ if (GEP1Ops.size() > MinOperands) {
+ for (unsigned i = FirstConstantOper; i != MaxOperands; ++i)
+ if (isa<Constant>(GEP1Ops[i]) && !isa<ConstantExpr>(GEP1Ops[i]) &&
+ !cast<Constant>(GEP1Ops[i])->isNullValue()) {
+ // Yup, there's a constant in the tail. Set all variables to
+ // constants in the GEP instruction to make it suiteable for
+ // TargetData::getIndexedOffset.
+ for (i = 0; i != MaxOperands; ++i)
+ if (!isa<Constant>(GEP1Ops[i]) || isa<ConstantExpr>(GEP1Ops[i]))
+ GEP1Ops[i] = Constant::getNullValue(GEP1Ops[i]->getType());
+ // Okay, now get the offset. This is the relative offset for the full
+ // instruction.
+ const TargetData &TD = getTargetData();
+ int64_t Offset1 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops);
+
+ // Now crop off any constants from the end...
+ GEP1Ops.resize(MinOperands);
+ int64_t Offset2 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops);
+
+ // If the tail provided a bit enough offset, return noalias!
+ if ((uint64_t)(Offset2-Offset1) >= SizeMax)
+ return NoAlias;
+ }
+ }
+
+ // Couldn't find anything useful.
+ return MayAlias;
+ }
// If there are non-equal constants arguments, then we can figure
// out a minimum known delta between the two index expressions... at
// this point we know that the first constant index of GEP1 is less
// than the first constant index of GEP2.
- //
- std::vector<Value*> Indices1;
- Indices1.reserve(NumGEPOperands-1);
- for (unsigned i = 1; i != FirstConstantOper; ++i)
- Indices1.push_back(Constant::getNullValue(GEP1->getOperand(i)
- ->getType()));
- std::vector<Value*> Indices2;
- Indices2.reserve(NumGEPOperands-1);
- Indices2 = Indices1; // Copy the zeros prefix...
-
- // Add the two known constant operands...
- Indices1.push_back((Value*)GEP1->getOperand(FirstConstantOper));
- Indices2.push_back((Value*)GEP2->getOperand(FirstConstantOper));
+
+ // Advance BasePtr[12]Ty over this first differing constant operand.
+ BasePtr2Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(GEP2Ops[FirstConstantOper]);
+ BasePtr1Ty = cast<CompositeType>(BasePtr1Ty)->getTypeAtIndex(GEP1Ops[FirstConstantOper]);
- const Type *GEPPointerTy = GEP1->getOperand(0)->getType();
+ // We are going to be using TargetData::getIndexedOffset to determine the
+ // offset that each of the GEP's is reaching. To do this, we have to convert
+ // all variable references to constant references. To do this, we convert the
+ // initial equal sequence of variables into constant zeros to start with.
+ for (unsigned i = 0; i != FirstConstantOper; ++i) {
+ if (!isa<Constant>(GEP1Ops[i]) || isa<ConstantExpr>(GEP1Ops[i]) ||
+ !isa<Constant>(GEP2Ops[i]) || isa<ConstantExpr>(GEP2Ops[i])) {
+ GEP1Ops[i] = Constant::getNullValue(GEP1Ops[i]->getType());
+ GEP2Ops[i] = Constant::getNullValue(GEP2Ops[i]->getType());
+ }
+ }
+
+ // We know that GEP1Ops[FirstConstantOper] & GEP2Ops[FirstConstantOper] are ok
+
// Loop over the rest of the operands...
- for (unsigned i = FirstConstantOper+1; i!=NumGEPOperands; ++i){
- const Value *Op1 = GEP1->getOperand(i);
- const Value *Op2 = GEP1->getOperand(i);
- if (Op1 == Op2) { // If they are equal, use a zero index...
- Indices1.push_back(Constant::getNullValue(Op1->getType()));
- Indices2.push_back(Indices1.back());
+ for (unsigned i = FirstConstantOper+1; i != MaxOperands; ++i) {
+ const Value *Op1 = i < GEP1Ops.size() ? GEP1Ops[i] : 0;
+ const Value *Op2 = i < GEP2Ops.size() ? GEP2Ops[i] : 0;
+ // If they are equal, use a zero index...
+ if (Op1 == Op2 && BasePtr1Ty == BasePtr2Ty) {
+ if (!isa<Constant>(Op1) || isa<ConstantExpr>(Op1))
+ GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Op1->getType());
+ // Otherwise, just keep the constants we have.
} else {
- if (isa<Constant>(Op1))
- Indices1.push_back((Value*)Op1);
- else {
- // GEP1 is known to produce a value less than GEP2. To be
- // conservatively correct, we must assume the largest
- // possible constant is used in this position. This cannot
- // be the initial index to the GEP instructions (because we
- // know we have at least one element before this one with
- // the different constant arguments), so we know that the
- // current index must be into either a struct or array.
- // Because of this, we can calculate the maximum value
- // possible.
- //
- const Type *ElTy = GEP1->getIndexedType(GEPPointerTy,
- Indices1, true);
- if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
- Indices1.push_back(ConstantUInt::get(Type::UByteTy,
- STy->getNumContainedTypes()));
+ if (Op1) {
+ if (const ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
+ // If this is an array index, make sure the array element is in range.
+ if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
+ if (Op1C->getRawValue() >= AT->getNumElements())
+ return MayAlias; // Be conservative with out-of-range accesses
+
} else {
- Indices1.push_back(ConstantSInt::get(Type::LongTy,
- cast<ArrayType>(ElTy)->getNumElements()));
+ // GEP1 is known to produce a value less than GEP2. To be
+ // conservatively correct, we must assume the largest possible
+ // constant is used in this position. This cannot be the initial
+ // index to the GEP instructions (because we know we have at least one
+ // element before this one with the different constant arguments), so
+ // we know that the current index must be into either a struct or
+ // array. Because we know it's not constant, this cannot be a
+ // structure index. Because of this, we can calculate the maximum
+ // value possible.
+ //
+ if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
+ GEP1Ops[i] = ConstantSInt::get(Type::LongTy,AT->getNumElements()-1);
}
}
- if (isa<Constant>(Op2))
- Indices2.push_back((Value*)Op2);
- else // Conservatively assume the minimum value for this index
- Indices2.push_back(Constant::getNullValue(Op1->getType()));
+ if (Op2) {
+ if (const ConstantInt *Op2C = dyn_cast<ConstantInt>(Op2)) {
+ // If this is an array index, make sure the array element is in range.
+ if (const ArrayType *AT = dyn_cast<ArrayType>(BasePtr1Ty))
+ if (Op2C->getRawValue() >= AT->getNumElements())
+ return MayAlias; // Be conservative with out-of-range accesses
+ } else { // Conservatively assume the minimum value for this index
+ GEP2Ops[i] = Constant::getNullValue(Op2->getType());
+ }
+ }
+ }
+
+ if (BasePtr1Ty && Op1) {
+ if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr1Ty))
+ BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[i]);
+ else
+ BasePtr1Ty = 0;
+ }
+
+ if (BasePtr2Ty && Op2) {
+ if (const CompositeType *CT = dyn_cast<CompositeType>(BasePtr2Ty))
+ BasePtr2Ty = CT->getTypeAtIndex(GEP2Ops[i]);
+ else
+ BasePtr2Ty = 0;
}
}
- unsigned Offset1 = getTargetData().getIndexedOffset(GEPPointerTy, Indices1);
- unsigned Offset2 = getTargetData().getIndexedOffset(GEPPointerTy, Indices2);
+ int64_t Offset1 = getTargetData().getIndexedOffset(GEPPointerTy, GEP1Ops);
+ int64_t Offset2 = getTargetData().getIndexedOffset(GEPPointerTy, GEP2Ops);
assert(Offset1 < Offset2 &&"There is at least one different constant here!");
- if (Offset2-Offset1 >= SizeMax) {
+ if ((uint64_t)(Offset2-Offset1) >= SizeMax) {
//std::cerr << "Determined that these two GEP's don't alias ["
// << SizeMax << " bytes]: \n" << *GEP1 << *GEP2;
return NoAlias;
projects / oota-llvm.git / blobdiff