diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp index c82c802fcccf..15ae344522f1 100644 --- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp +++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp @@ -39,26 +39,6 @@ using namespace llvm; // Useful predicates //===----------------------------------------------------------------------===// -static const Value *GetGEPOperands(const GEPOperator *V, - SmallVector &GEPOps) { - assert(GEPOps.empty() && "Expect empty list to populate!"); - GEPOps.insert(GEPOps.end(), V->op_begin()+1, V->op_end()); - - // Accumulate all of the chained indexes into the operand array. - Value *BasePtr = V->getOperand(0); - while (1) { - V = dyn_cast(BasePtr); - if (V == 0) return BasePtr; - - // Don't handle folding arbitrary pointer offsets yet. - if (!isa(GEPOps[0]) || !cast(GEPOps[0])->isNullValue()) - return BasePtr; - - GEPOps.erase(GEPOps.begin()); // Drop the zero index - GEPOps.insert(GEPOps.begin(), V->op_begin()+1, V->op_end()); - } -} - /// isKnownNonNull - Return true if we know that the specified value is never /// null. static bool isKnownNonNull(const Value *V) { @@ -235,15 +215,6 @@ namespace { 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. - AliasResult - CheckGEPInstructions(const Type* BasePtr1Ty, - Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1Size, - const Type *BasePtr2Ty, - Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2Size); }; } // End of anonymous namespace @@ -418,7 +389,7 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) { /// FIXME: Move this out to ValueTracking.cpp /// static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs, - SmallVectorImpl > &VarIndices, + SmallVectorImpl > &VarIndices, const TargetData *TD) { // FIXME: Should limit depth like getUnderlyingObject? BaseOffs = 0; @@ -488,6 +459,7 @@ static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs, // If we already had an occurrance of this index variable, merge this // scale into it. For example, we want to handle: // A[x][x] -> x*16 + x*4 -> x*20 + // This also ensures that 'x' only appears in the index list once. for (unsigned i = 0, e = VarIndices.size(); i != e; ++i) { if (VarIndices[i].first == Index) { Scale += VarIndices[i].second; @@ -512,6 +484,39 @@ static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs, } } +/// GetIndiceDifference - 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( + SmallVectorImpl > &Dest, + const SmallVectorImpl > &Src) { + if (Src.empty()) return; + + for (unsigned i = 0, e = Src.size(); i != e; ++i) { + const Value *V = Src[i].first; + int64_t Scale = Src[i].second; + + // Find V in Dest. This is N^2, but pointer indices almost never have more + // than a few variable indexes. + for (unsigned j = 0, e = Dest.size(); j != e; ++j) { + if (Dest[j].first != V) continue; + + // If we found it, subtract off Scale V's from the entry in Dest. If it + // goes to zero, remove the entry. + if (Dest[j].second != Scale) + Dest[j].second -= Scale; + else + Dest.erase(Dest.begin()+j); + Scale = 0; + break; + } + + // If we didn't consume this entry, add it to the end of the Dest list. + if (Scale) + Dest.push_back(std::make_pair(V, -Scale)); + } +} /// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction /// against another pointer. We know that V1 is a GEP, but we don't know @@ -523,101 +528,83 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, unsigned V1Size, const Value *V2, unsigned V2Size, const Value *UnderlyingV1, const Value *UnderlyingV2) { + int64_t GEP1BaseOffset; + SmallVector, 4> GEP1VariableIndices; + // 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 GEPOperator *GEP2 = dyn_cast(V2)) { - // If V1 and V2 are identical GEPs, just recurse down on both of them. - // This allows us to analyze things like: - // P = gep A, 0, i, 1 - // Q = gep B, 0, i, 1 - // by just analyzing A and B. This is even safe for variable indices. - if (GEP1->getType() == GEP2->getType() && - GEP1->getNumOperands() == GEP2->getNumOperands() && - 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 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 (isa(GEP1->getOperand(0)) && - GEP1->getOperand(1) == - Constant::getNullValue(GEP1->getOperand(1)->getType())) - GEP1 = cast(GEP1->getOperand(0)); - const Value *BasePtr1 = GEP1->getOperand(0); - - while (isa(GEP2->getOperand(0)) && - GEP2->getOperand(1) == - Constant::getNullValue(GEP2->getOperand(1)->getType())) - GEP2 = cast(GEP2->getOperand(0)); - const Value *BasePtr2 = GEP2->getOperand(0); - // Do the base pointers alias? - 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 - // figure out anything about the resultant pointers, to try to prove - // non-aliasing. + AliasResult BaseAlias = aliasCheck(UnderlyingV1, ~0U, UnderlyingV2, ~0U); + + // If we get a No or May, then return it immediately, no amount of analysis + // will improve this situation. + if (BaseAlias != MustAlias) return BaseAlias; + + // Otherwise, we have a MustAlias. Since the base pointers alias each other + // exactly, see if the computed offset from the common pointer tells us + // about the relation of the resulting pointer. + const Value *GEP1BasePtr = + DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD); + + int64_t GEP2BaseOffset; + SmallVector, 4> GEP2VariableIndices; + const Value *GEP2BasePtr = + DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD); + + // If DecomposeGEPExpression isn't able to look all the way through the + // addressing operation, we must not have TD and this is too complex for us + // to handle without it. + if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) { + assert(TD == 0 && + "DecomposeGEPExpression and getUnderlyingObject disagree!"); + return MayAlias; + } + + // Subtract the GEP2 pointer from the GEP1 pointer to find out their + // symbolic difference. + GEP1BaseOffset -= GEP2BaseOffset; + GetIndiceDifference(GEP1VariableIndices, GEP2VariableIndices); + + } else { + // Check to see if these two pointers are related by the getelementptr + // instruction. If one pointer is a GEP with a non-zero index of the other + // pointer, we know they cannot alias. + // + // FIXME: The check below only looks at the size of one of the pointers, not + // both, this may cause us to miss things. + if (V1Size == ~0U || V2Size == ~0U) + return MayAlias; - // Collect all of the chained GEP operands together into one simple place - SmallVector GEP1Ops, GEP2Ops; - BasePtr1 = GetGEPOperands(GEP1, GEP1Ops); - BasePtr2 = GetGEPOperands(GEP2, GEP2Ops); + AliasResult R = aliasCheck(UnderlyingV1, ~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 GetGEPOperands were able to fold to the same must-aliased pointer, - // do the comparison. - if (BasePtr1 == BasePtr2) { - AliasResult GAlias = - CheckGEPInstructions(BasePtr1->getType(), - &GEP1Ops[0], GEP1Ops.size(), V1Size, - BasePtr2->getType(), - &GEP2Ops[0], GEP2Ops.size(), V2Size); - if (GAlias != MayAlias) - return GAlias; - } + const Value *GEP1BasePtr = + DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD); + + // If DecomposeGEPExpression isn't able to look all the way through the + // addressing operation, we must not have TD and this is too complex for us + // to handle without it. + if (GEP1BasePtr != UnderlyingV1) { + assert(TD == 0 && + "DecomposeGEPExpression and getUnderlyingObject disagree!"); + return MayAlias; } } - - // 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. + + // In the two GEP Case, if there is no difference in the offsets of the + // computed pointers, the resultant pointers are a must alias. This + // hapens when we have two lexically identical GEP's (for example). // - // FIXME: The check below only looks at the size of one of the pointers, not - // both, this may cause us to miss things. - if (V1Size == ~0U || V2Size == ~0U) - return MayAlias; - - AliasResult R = aliasCheck(UnderlyingV1, ~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; - - int64_t GEP1BaseOffset; - SmallVector, 4> VariableIndices; - const Value *GEP1BasePtr = - DecomposeGEPExpression(GEP1, GEP1BaseOffset, VariableIndices, TD); - - // If DecomposeGEPExpression isn't able to look all the way through the - // addressing operation, we must not have TD and this is too complex for us - // to handle without it. - if (GEP1BasePtr != UnderlyingV1) { - assert(TD == 0 && - "DecomposeGEPExpression and getUnderlyingObject disagree!"); - return MayAlias; - } - - // If we have getelementptr , 0, 0, 0, 0, ... and V2 must aliases - // the ptr, the end result is a must alias also. - if (GEP1BaseOffset == 0 && VariableIndices.empty()) + // In the other case, if we have getelementptr , 0, 0, 0, 0, ... and V2 + // must aliases the GEP, the end result is a must alias also. + if (GEP1BaseOffset == 0 && GEP1VariableIndices.empty()) return MustAlias; // If we have a known constant offset, see if this offset is larger than the @@ -631,9 +618,10 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, unsigned V1Size, // multiple of any of our variable indices. This allows us to transform // things like &A[i][1] because i has a stride of (e.g.) 8 bytes but the 1 // provides an offset of 4 bytes (assuming a <= 4 byte access). - for (unsigned i = 0, e = VariableIndices.size(); i != e && GEP1BaseOffset;++i) - if (int64_t RemovedOffset = GEP1BaseOffset/VariableIndices[i].second) - GEP1BaseOffset -= RemovedOffset*VariableIndices[i].second; + for (unsigned i = 0, e = GEP1VariableIndices.size(); + i != e && GEP1BaseOffset;++i) + if (int64_t RemovedOffset = GEP1BaseOffset/GEP1VariableIndices[i].second) + GEP1BaseOffset -= RemovedOffset*GEP1VariableIndices[i].second; // If our known offset is bigger than the access size, we know we don't have // an alias. @@ -850,351 +838,5 @@ BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size, return MayAlias; } -// This function is used to determine if the indices of two GEP instructions are -// equal. V1 and V2 are the indices. -static bool IndexOperandsEqual(Value *V1, Value *V2) { - if (V1->getType() == V2->getType()) - return V1 == V2; - if (Constant *C1 = dyn_cast(V1)) - if (Constant *C2 = dyn_cast(V2)) { - // Sign extend the constants to long types, if necessary - if (C1->getType() != Type::getInt64Ty(C1->getContext())) - C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext())); - if (C2->getType() != Type::getInt64Ty(C1->getContext())) - C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext())); - return C1 == C2; - } - return false; -} - -/// 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, Value **GEP1Ops, unsigned NumGEP1Ops, unsigned G1S, - const Type *BasePtr2Ty, Value **GEP2Ops, unsigned NumGEP2Ops, 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 PointerType *GEPPointerTy = cast(BasePtr1Ty); - - // Find the (possibly empty) initial sequence of equal values... which are not - // necessarily constants. - unsigned NumGEP1Operands = NumGEP1Ops, NumGEP2Operands = NumGEP2Ops; - unsigned MinOperands = std::min(NumGEP1Operands, NumGEP2Operands); - unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands); - unsigned UnequalOper = 0; - while (UnequalOper != MinOperands && - IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper])) { - // Advance through the type as we go... - ++UnequalOper; - if (const CompositeType *CT = dyn_cast(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) { - if (NumGEP1Ops < NumGEP2Ops) { - std::swap(GEP1Ops, GEP2Ops); - std::swap(NumGEP1Ops, NumGEP2Ops); - } - - bool AllAreZeros = true; - for (unsigned i = UnequalOper; i != MaxOperands; ++i) - if (!isa(GEP1Ops[i]) || - !cast(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 - // no-alias result if there are differing constant pairs in the index - // chain. For example: - // A[i][0] != A[j][1] iff (&A[0][1]-&A[0][0] >= std::max(G1S, G2S)) - // - // We have to be careful here about array accesses. In particular, consider: - // A[1][0] vs A[0][i] - // In this case, we don't *know* that the array will be accessed in bounds: - // the index could even be negative. Because of this, we have to - // conservatively *give up* and return may alias. We disregard differing - // array subscripts that are followed by a variable index without going - // through a struct. - // - 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 getelementptrs... - unsigned FirstConstantOper = UnequalOper; - for (; FirstConstantOper != MinOperands; ++FirstConstantOper) { - const Value *G1Oper = GEP1Ops[FirstConstantOper]; - const Value *G2Oper = GEP2Ops[FirstConstantOper]; - - if (G1Oper != G2Oper) // Found non-equal constant indexes... - if (Constant *G1OC = dyn_cast(const_cast(G1Oper))) - if (Constant *G2OC = dyn_cast(const_cast(G2Oper))){ - if (G1OC->getType() != G2OC->getType()) { - // Sign extend both operands to long. - const Type *Int64Ty = Type::getInt64Ty(G1OC->getContext()); - if (G1OC->getType() != Int64Ty) - G1OC = ConstantExpr::getSExt(G1OC, Int64Ty); - if (G2OC->getType() != Int64Ty) - G2OC = ConstantExpr::getSExt(G2OC, Int64Ty); - GEP1Ops[FirstConstantOper] = G1OC; - GEP2Ops[FirstConstantOper] = G2OC; - } - - if (G1OC != G2OC) { - // Handle the "be careful" case above: if this is an array/vector - // subscript, scan for a subsequent variable array index. - if (const SequentialType *STy = - dyn_cast(BasePtr1Ty)) { - const Type *NextTy = STy; - bool isBadCase = false; - - for (unsigned Idx = FirstConstantOper; - Idx != MinOperands && isa(NextTy); ++Idx) { - const Value *V1 = GEP1Ops[Idx], *V2 = GEP2Ops[Idx]; - if (!isa(V1) || !isa(V2)) { - isBadCase = true; - break; - } - // If the array is indexed beyond the bounds of the static type - // at this level, it will also fall into the "be careful" case. - // It would theoretically be possible to analyze these cases, - // but for now just be conservatively correct. - if (const ArrayType *ATy = dyn_cast(STy)) - if (cast(G1OC)->getZExtValue() >= - ATy->getNumElements() || - cast(G2OC)->getZExtValue() >= - ATy->getNumElements()) { - isBadCase = true; - break; - } - if (const VectorType *VTy = dyn_cast(STy)) - if (cast(G1OC)->getZExtValue() >= - VTy->getNumElements() || - cast(G2OC)->getZExtValue() >= - VTy->getNumElements()) { - isBadCase = true; - break; - } - STy = cast(NextTy); - NextTy = cast(NextTy)->getElementType(); - } - - if (isBadCase) G1OC = 0; - } - - // Make sure they are comparable (ie, not constant expressions), and - // make sure the GEP with the smaller leading constant is GEP1. - if (G1OC) { - Constant *Compare = ConstantExpr::getICmp(ICmpInst::ICMP_SGT, - G1OC, G2OC); - if (ConstantInt *CV = dyn_cast(Compare)) { - if (CV->getZExtValue()) { // If they are comparable and G2 > G1 - std::swap(GEP1Ops, GEP2Ops); // Make GEP1 < GEP2 - std::swap(NumGEP1Ops, NumGEP2Ops); - } - break; - } - } - } - } - BasePtr1Ty = cast(BasePtr1Ty)->getTypeAtIndex(G1Oper); - } - - // 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. Check this now. - if (FirstConstantOper == MinOperands) { - // Without TargetData, we won't know what the offsets are. - if (!TD) - return MayAlias; - - // Make GEP1Ops be the longer one if there is a longer one. - if (NumGEP1Ops < NumGEP2Ops) { - std::swap(GEP1Ops, GEP2Ops); - std::swap(NumGEP1Ops, NumGEP2Ops); - } - - // Is there anything to check? - if (NumGEP1Ops > MinOperands) { - for (unsigned i = FirstConstantOper; i != MaxOperands; ++i) - if (isa(GEP1Ops[i]) && - !cast(GEP1Ops[i])->isZero()) { - // Yup, there's a constant in the tail. Set all variables to - // constants in the GEP instruction to make it suitable for - // TargetData::getIndexedOffset. - for (i = 0; i != MaxOperands; ++i) - if (!isa(GEP1Ops[i])) - GEP1Ops[i] = Constant::getNullValue(GEP1Ops[i]->getType()); - // Okay, now get the offset. This is the relative offset for the full - // instruction. - int64_t Offset1 = TD->getIndexedOffset(GEPPointerTy, GEP1Ops, - NumGEP1Ops); - - // Now check without any constants at the end. - int64_t Offset2 = TD->getIndexedOffset(GEPPointerTy, GEP1Ops, - MinOperands); - - // Make sure we compare the absolute difference. - if (Offset1 > Offset2) - std::swap(Offset1, Offset2); - - // If the tail provided a bit enough offset, return noalias! - if ((uint64_t)(Offset2-Offset1) >= SizeMax) - return NoAlias; - // Otherwise break - we don't look for another constant in the tail. - break; - } - } - - // 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. - - // Advance BasePtr[12]Ty over this first differing constant operand. - BasePtr2Ty = cast(BasePtr1Ty)-> - getTypeAtIndex(GEP2Ops[FirstConstantOper]); - BasePtr1Ty = cast(BasePtr1Ty)-> - getTypeAtIndex(GEP1Ops[FirstConstantOper]); - - // 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 sequence of array subscripts into constant zeros to start with. - const Type *ZeroIdxTy = GEPPointerTy; - for (unsigned i = 0; i != FirstConstantOper; ++i) { - if (!isa(ZeroIdxTy)) - GEP1Ops[i] = GEP2Ops[i] = - Constant::getNullValue(Type::getInt32Ty(ZeroIdxTy->getContext())); - - if (const CompositeType *CT = dyn_cast(ZeroIdxTy)) - ZeroIdxTy = CT->getTypeAtIndex(GEP1Ops[i]); - } - - // We know that GEP1Ops[FirstConstantOper] & GEP2Ops[FirstConstantOper] are ok - - // Loop over the rest of the operands... - for (unsigned i = FirstConstantOper+1; i != MaxOperands; ++i) { - const Value *Op1 = i < NumGEP1Ops ? GEP1Ops[i] : 0; - const Value *Op2 = i < NumGEP2Ops ? GEP2Ops[i] : 0; - // If they are equal, use a zero index... - if (Op1 == Op2 && BasePtr1Ty == BasePtr2Ty) { - if (!isa(Op1)) - GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Op1->getType()); - // Otherwise, just keep the constants we have. - } else { - if (Op1) { - if (const ConstantInt *Op1C = dyn_cast(Op1)) { - // If this is an array index, make sure the array element is in range. - if (const ArrayType *AT = dyn_cast(BasePtr1Ty)) { - if (Op1C->getZExtValue() >= AT->getNumElements()) - return MayAlias; // Be conservative with out-of-range accesses - } else if (const VectorType *VT = dyn_cast(BasePtr1Ty)) { - if (Op1C->getZExtValue() >= VT->getNumElements()) - return MayAlias; // Be conservative with out-of-range accesses - } - - } 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 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(BasePtr1Ty)) - GEP1Ops[i] = - ConstantInt::get(Type::getInt64Ty(AT->getContext()), - AT->getNumElements()-1); - else if (const VectorType *VT = dyn_cast(BasePtr1Ty)) - GEP1Ops[i] = - ConstantInt::get(Type::getInt64Ty(VT->getContext()), - VT->getNumElements()-1); - } - } - - if (Op2) { - if (const ConstantInt *Op2C = dyn_cast(Op2)) { - // If this is an array index, make sure the array element is in range. - if (const ArrayType *AT = dyn_cast(BasePtr2Ty)) { - if (Op2C->getZExtValue() >= AT->getNumElements()) - return MayAlias; // Be conservative with out-of-range accesses - } else if (const VectorType *VT = dyn_cast(BasePtr2Ty)) { - if (Op2C->getZExtValue() >= VT->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(BasePtr1Ty)) - BasePtr1Ty = CT->getTypeAtIndex(GEP1Ops[i]); - else - BasePtr1Ty = 0; - } - - if (BasePtr2Ty && Op2) { - if (const CompositeType *CT = dyn_cast(BasePtr2Ty)) - BasePtr2Ty = CT->getTypeAtIndex(GEP2Ops[i]); - else - BasePtr2Ty = 0; - } - } - - if (TD && GEPPointerTy->getElementType()->isSized()) { - int64_t Offset1 = - TD->getIndexedOffset(GEPPointerTy, GEP1Ops, NumGEP1Ops); - int64_t Offset2 = - TD->getIndexedOffset(GEPPointerTy, GEP2Ops, NumGEP2Ops); - assert(Offset1 != Offset2 && - "There is at least one different constant here!"); - - // Make sure we compare the absolute difference. - if (Offset1 > Offset2) - std::swap(Offset1, Offset2); - - if ((uint64_t)(Offset2-Offset1) >= SizeMax) { - //cerr << "Determined that these two GEP's don't alias [" - // << SizeMax << " bytes]: \n" << *GEP1 << *GEP2; - return NoAlias; - } - } - return MayAlias; -} - // Make sure that anything that uses AliasAnalysis pulls in this file. DEFINING_FILE_FOR(BasicAliasAnalysis) diff --git a/llvm/test/Analysis/BasicAA/2008-12-09-GEP-IndicesAlias.ll b/llvm/test/Analysis/BasicAA/2008-12-09-GEP-IndicesAlias.ll index aaf9061953e7..e8f8a8e4b9f1 100644 --- a/llvm/test/Analysis/BasicAA/2008-12-09-GEP-IndicesAlias.ll +++ b/llvm/test/Analysis/BasicAA/2008-12-09-GEP-IndicesAlias.ll @@ -1,7 +1,9 @@ -; RUN: opt < %s -aa-eval -print-all-alias-modref-info -disable-output |& grep {MustAlias:.*%R,.*%r} +; RUN: opt < %s -gvn -instcombine -S |& FileCheck %s ; Make sure that basicaa thinks R and r are must aliases. -define i32 @test(i8 * %P) { +target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128" + +define i32 @test1(i8 * %P) { entry: %Q = bitcast i8* %P to {i32, i32}* %R = getelementptr {i32, i32}* %Q, i32 0, i32 1 @@ -13,4 +15,59 @@ entry: %t = sub i32 %S, %s ret i32 %t +; CHECK: @test1 +; CHECK: ret i32 0 +} + +define i32 @test2(i8 * %P) { +entry: + %Q = bitcast i8* %P to {i32, i32, i32}* + %R = getelementptr {i32, i32, i32}* %Q, i32 0, i32 1 + %S = load i32* %R + + %r = getelementptr {i32, i32, i32}* %Q, i32 0, i32 2 + store i32 42, i32* %r + + %s = load i32* %R + + %t = sub i32 %S, %s + ret i32 %t +; CHECK: @test2 +; CHECK: ret i32 0 +} + + +; This was a miscompilation. +define i32 @test3({float, {i32, i32, i32}}* %P) { +entry: + %P2 = getelementptr {float, {i32, i32, i32}}* %P, i32 0, i32 1 + %R = getelementptr {i32, i32, i32}* %P2, i32 0, i32 1 + %S = load i32* %R + + %r = getelementptr {i32, i32, i32}* %P2, i32 0, i32 2 + store i32 42, i32* %r + + %s = load i32* %R + + %t = sub i32 %S, %s + ret i32 %t +; CHECK: @test3 +; CHECK: ret i32 0 +} + + +;; This is reduced from the SmallPtrSet constructor. +%SmallPtrSetImpl = type { i8**, i32, i32, i32, [1 x i8*] } +%SmallPtrSet64 = type { %SmallPtrSetImpl, [64 x i8*] } + +define i32 @test4(%SmallPtrSet64* %P) { +entry: + %tmp2 = getelementptr inbounds %SmallPtrSet64* %P, i64 0, i32 0, i32 1 + store i32 64, i32* %tmp2, align 8 + %tmp3 = getelementptr inbounds %SmallPtrSet64* %P, i64 0, i32 0, i32 4, i64 64 + store i8* null, i8** %tmp3, align 8 + %tmp4 = load i32* %tmp2, align 8 + ret i32 %tmp4 +; CHECK: @test4 +; CHECK: ret i32 64 }