X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FBasicAliasAnalysis.cpp;h=49d771a42d70836920ca1909a66b18215bdc1f40;hb=6316fbcb04af00fe76b6526fab09f51484014b3e;hp=580f7e5d9e44b258ca5b527a3944326fa263c605;hpb=07a96765daedf180a7102d39fe56c499878312b7;p=oota-llvm.git diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index 580f7e5d9e4..49d771a42d7 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -2,8 +2,8 @@ // // 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 is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // @@ -14,21 +14,121 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Analysis/CaptureTracking.h" #include "llvm/Analysis/Passes.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/Function.h" #include "llvm/GlobalVariable.h" #include "llvm/Instructions.h" +#include "llvm/IntrinsicInst.h" +#include "llvm/LLVMContext.h" +#include "llvm/Operator.h" #include "llvm/Pass.h" #include "llvm/Target/TargetData.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 "llvm/Support/ManagedStatic.h" #include using namespace llvm; +//===----------------------------------------------------------------------===// +// Useful predicates +//===----------------------------------------------------------------------===// + +static const GEPOperator *isGEP(const Value *V) { + return dyn_cast(V); +} + +static const Value *GetGEPOperands(const Value *V, + SmallVector &GEPOps) { + assert(GEPOps.empty() && "Expect empty list to populate!"); + GEPOps.insert(GEPOps.end(), cast(V)->op_begin()+1, + cast(V)->op_end()); + + // Accumulate all of the chained indexes into the operand array + V = cast(V)->getOperand(0); + + while (const User *G = isGEP(V)) { + if (!isa(GEPOps[0]) || isa(GEPOps[0]) || + !cast(GEPOps[0])->isNullValue()) + break; // Don't handle folding arbitrary pointer offsets yet... + GEPOps.erase(GEPOps.begin()); // Drop the zero index + GEPOps.insert(GEPOps.begin(), G->op_begin()+1, G->op_end()); + V = G->getOperand(0); + } + return V; +} + +/// isKnownNonNull - Return true if we know that the specified value is never +/// null. +static bool isKnownNonNull(const Value *V) { + // Alloca never returns null, malloc might. + if (isa(V)) return true; + + // A byval argument is never null. + if (const Argument *A = dyn_cast(V)) + return A->hasByValAttr(); + + // Global values are not null unless extern weak. + if (const GlobalValue *GV = dyn_cast(V)) + return !GV->hasExternalWeakLinkage(); + return false; +} + +/// isNonEscapingLocalObject - Return true if the pointer is to a function-local +/// 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(V) || isNoAliasCall(V)) + return !PointerMayBeCaptured(V, false); + + // If this is an argument that corresponds to a byval or noalias argument, + // then it has not escaped before entering the function. Check if it escapes + // inside the function. + if (const Argument *A = dyn_cast(V)) + if (A->hasByValAttr() || A->hasNoAliasAttr()) { + // Don't bother analyzing arguments already known not to escape. + if (A->hasNoCaptureAttr()) + return true; + return !PointerMayBeCaptured(V, false); + } + return false; +} + + +/// isObjectSmallerThan - Return true if we can prove that the object specified +/// by V is smaller than Size. +static bool isObjectSmallerThan(const Value *V, unsigned Size, + const TargetData &TD) { + const Type *AccessTy; + if (const GlobalVariable *GV = dyn_cast(V)) { + AccessTy = GV->getType()->getElementType(); + } else if (const AllocationInst *AI = dyn_cast(V)) { + if (!AI->isArrayAllocation()) + AccessTy = AI->getType()->getElementType(); + else + return false; + } else if (const Argument *A = dyn_cast(V)) { + if (A->hasByValAttr()) + AccessTy = cast(A->getType())->getElementType(); + else + return false; + } else { + return false; + } + + if (AccessTy->isSized()) + return TD.getTypeAllocSize(AccessTy) < Size; + return false; +} + +//===----------------------------------------------------------------------===// +// NoAA Pass +//===----------------------------------------------------------------------===// + namespace { /// NoAA - This class implements the -no-aa pass, which always returns "I /// don't know" for alias queries. NoAA is unlike other alias analysis @@ -37,8 +137,8 @@ namespace { /// struct VISIBILITY_HIDDEN NoAA : public ImmutablePass, public AliasAnalysis { static char ID; // Class identification, replacement for typeinfo - NoAA() : ImmutablePass((intptr_t)&ID) {} - explicit NoAA(intptr_t PID) : ImmutablePass(PID) { } + NoAA() : ImmutablePass(&ID) {} + explicit NoAA(void *PID) : ImmutablePass(PID) { } virtual void getAnalysisUsage(AnalysisUsage &AU) const { AU.addRequired(); @@ -53,14 +153,9 @@ namespace { return MayAlias; } - virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS, - std::vector *Info) { - return UnknownModRefBehavior; - } - virtual void getArgumentAccesses(Function *F, CallSite CS, std::vector &Info) { - assert(0 && "This method may not be called on this function!"); + llvm_unreachable("This method may not be called on this function!"); } virtual void getMustAliases(Value *P, std::vector &RetVals) { } @@ -76,32 +171,34 @@ namespace { virtual void deleteValue(Value *V) {} virtual void copyValue(Value *From, Value *To) {} }; +} // End of anonymous namespace - // Register this pass... - char NoAA::ID = 0; - RegisterPass - U("no-aa", "No Alias Analysis (always returns 'may' alias)"); +// Register this pass... +char NoAA::ID = 0; +static RegisterPass +U("no-aa", "No Alias Analysis (always returns 'may' alias)", true, true); - // Declare that we implement the AliasAnalysis interface - RegisterAnalysisGroup V(U); -} // End of anonymous namespace +// Declare that we implement the AliasAnalysis interface +static RegisterAnalysisGroup V(U); ImmutablePass *llvm::createNoAAPass() { return new NoAA(); } +//===----------------------------------------------------------------------===// +// BasicAA Pass +//===----------------------------------------------------------------------===// + 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 VISIBILITY_HIDDEN BasicAliasAnalysis : public NoAA { static char ID; // Class identification, replacement for typeinfo - BasicAliasAnalysis() : NoAA((intptr_t)&ID) { } + BasicAliasAnalysis() : NoAA(&ID) {} AliasResult alias(const Value *V1, unsigned V1Size, const Value *V2, unsigned V2Size); ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size); - ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) { - return NoAA::getModRefInfo(CS1,CS2); - } + ModRefResult getModRefInfo(CallSite CS1, CallSite CS2); /// hasNoModRefInfoForCalls - We can provide mod/ref information against /// non-escaping allocations. @@ -111,9 +208,6 @@ namespace { /// global) or not. bool pointsToConstantMemory(const Value *P); - virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS, - std::vector *Info); - private: // CheckGEPInstructions - Check two GEP instructions with known // must-aliasing base pointers. This checks to see if the index expressions @@ -124,114 +218,30 @@ namespace { const Type *BasePtr2Ty, Value **GEP2Ops, unsigned NumGEP2Ops, unsigned G2Size); }; +} // End of anonymous namespace - // Register this pass... - char BasicAliasAnalysis::ID = 0; - RegisterPass - X("basicaa", "Basic Alias Analysis (default AA impl)"); +// Register this pass... +char BasicAliasAnalysis::ID = 0; +static RegisterPass +X("basicaa", "Basic Alias Analysis (default AA impl)", false, true); - // Declare that we implement the AliasAnalysis interface - RegisterAnalysisGroup Y(X); -} // End of anonymous namespace +// Declare that we implement the AliasAnalysis interface +static RegisterAnalysisGroup Y(X); ImmutablePass *llvm::createBasicAliasAnalysisPass() { return new BasicAliasAnalysis(); } -// 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(V->getType())) return 0; - - // If we are at some type of object, return it. GlobalValues and Allocations - // have unique addresses. - if (isa(V) || isa(V) || isa(V)) - return V; - - // Traverse through different addressing mechanisms... - if (const Instruction *I = dyn_cast(V)) { - if (isa(I) || isa(I)) - return getUnderlyingObject(I->getOperand(0)); - } else if (const ConstantExpr *CE = dyn_cast(V)) { - if (CE->getOpcode() == Instruction::BitCast || - CE->getOpcode() == Instruction::GetElementPtr) - return getUnderlyingObject(CE->getOperand(0)); - } - return 0; -} - -static const User *isGEP(const Value *V) { - if (isa(V) || - (isa(V) && - cast(V)->getOpcode() == Instruction::GetElementPtr)) - return cast(V); - return 0; -} - -static const Value *GetGEPOperands(const Value *V, - SmallVector &GEPOps){ - assert(GEPOps.empty() && "Expect empty list to populate!"); - GEPOps.insert(GEPOps.end(), cast(V)->op_begin()+1, - cast(V)->op_end()); - - // Accumulate all of the chained indexes into the operand array - V = cast(V)->getOperand(0); - - while (const User *G = isGEP(V)) { - if (!isa(GEPOps[0]) || isa(GEPOps[0]) || - !cast(GEPOps[0])->isNullValue()) - break; // Don't handle folding arbitrary pointer offsets yet... - GEPOps.erase(GEPOps.begin()); // Drop the zero index - GEPOps.insert(GEPOps.begin(), G->op_begin()+1, G->op_end()); - V = G->getOperand(0); - } - return V; -} /// pointsToConstantMemory - Chase pointers until we find a (constant /// global) or not. bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) { - if (const Value *V = getUnderlyingObject(P)) - if (const GlobalVariable *GV = dyn_cast(V)) - return GV->isConstant(); + if (const GlobalVariable *GV = + dyn_cast(P->getUnderlyingObject())) + return GV->isConstant(); return false; } -// Determine if an AllocationInst instruction escapes from the function it is -// contained in. If it does not escape, there is no way for another function to -// mod/ref it. We do this by looking at its uses and determining if the uses -// can escape (recursively). -static bool AddressMightEscape(const Value *V) { - for (Value::use_const_iterator UI = V->use_begin(), E = V->use_end(); - UI != E; ++UI) { - const Instruction *I = cast(*UI); - switch (I->getOpcode()) { - case Instruction::Load: - break; //next use. - case Instruction::Store: - if (I->getOperand(0) == V) - return true; // Escapes if the pointer is stored. - break; // next use. - case Instruction::GetElementPtr: - if (AddressMightEscape(I)) - return true; - case Instruction::BitCast: - if (!isa(I->getType())) - return true; - if (AddressMightEscape(I)) - return true; - break; // next use - case Instruction::Ret: - // If returned, the address will escape to calling functions, but no - // callees could modify it. - break; // next use - default: - return true; - } - } - return false; -} // getModRefInfo - Check to see if the specified callsite can clobber the // specified memory object. Since we only look at local properties of this @@ -240,33 +250,67 @@ static bool AddressMightEscape(const Value *V) { // AliasAnalysis::ModRefResult BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) { - if (!isa(P)) - if (const AllocationInst *AI = - dyn_cast_or_null(getUnderlyingObject(P))) { - // Okay, the pointer is to a stack allocated object. If we can prove that - // the pointer never "escapes", then we know the call cannot clobber it, - // because it simply can't get its address. - if (!AddressMightEscape(AI)) - return NoModRef; - - // If this is a tail call and P points to a stack location, we know that - // the tail call cannot access or modify the local stack. + if (!isa(P)) { + const Value *Object = P->getUnderlyingObject(); + + // If this is a tail call and P points to a stack location, we know that + // the tail call cannot access or modify the local stack. + // We cannot exclude byval arguments here; these belong to the caller of + // the current function not to the current function, and a tail callee + // may reference them. + if (isa(Object)) if (CallInst *CI = dyn_cast(CS.getInstruction())) - if (CI->isTailCall() && isa(AI)) + if (CI->isTailCall()) return NoModRef; + + // If the pointer is to a locally allocated object that does not escape, + // then the call can not mod/ref the pointer unless the call takes the + // argument without capturing it. + if (isNonEscapingLocalObject(Object) && CS.getInstruction() != Object) { + bool passedAsArg = false; + // TODO: Eventually only check 'nocapture' arguments. + for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end(); + CI != CE; ++CI) + if (isa((*CI)->getType()) && + alias(cast(CI), ~0U, P, ~0U) != NoAlias) + passedAsArg = true; + + if (!passedAsArg) + return NoModRef; } + } // The AliasAnalysis base class has some smarts, lets use them. return AliasAnalysis::getModRefInfo(CS, P, Size); } + +AliasAnalysis::ModRefResult +BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite 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 (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory) + return Ref; + + // Otherwise, fall back to NoAA (mod+ref). + return NoAA::getModRefInfo(CS1, CS2); +} + + // 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. :) +// as array references. // AliasAnalysis::AliasResult BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, const Value *V2, unsigned V2Size) { + LLVMContext &Context = V1->getType()->getContext(); + // Strip off any constant expression casts if they exist if (const ConstantExpr *CE = dyn_cast(V1)) if (CE->isCast() && isa(CE->getOperand(0)->getType())) @@ -278,97 +322,88 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, // Are we checking for alias of the same value? if (V1 == V2) return MustAlias; - if ((!isa(V1->getType()) || !isa(V2->getType())) && - V1->getType() != Type::Int64Ty && V2->getType() != Type::Int64Ty) + if (!isa(V1->getType()) || !isa(V2->getType())) return NoAlias; // Scalars cannot alias each other - // Strip off cast instructions... + // Strip off cast instructions. Since V1 and V2 are pointers, they must be + // pointer<->pointer bitcasts. if (const BitCastInst *I = dyn_cast(V1)) return alias(I->getOperand(0), V1Size, V2, V2Size); if (const BitCastInst *I = dyn_cast(V2)) return alias(V1, V1Size, I->getOperand(0), V2Size); - // 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 discernible object? - if (O1) { - if (O2) { - if (isa(O1)) { - // Incoming argument cannot alias locally allocated object! - if (isa(O2)) return NoAlias; - // Otherwise, nothing is known... - } else if (isa(O2)) { - // Incoming argument cannot alias locally allocated object! - if (isa(O1)) return NoAlias; - // Otherwise, nothing is known... - } else if (O1 != O2) { - // If they are two different objects, we know that we have no alias... - 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. - } + // 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(O1) && (isa(O2) || isNoAliasCall(O2))) || + (isa(O2) && (isa(O1) || isNoAliasCall(O1)))) + return NoAlias; - if (!isa(O1) && isa(V2)) - return NoAlias; // Unique values don't alias null - - if (isa(O1) || - (isa(O1) && - !cast(O1)->isArrayAllocation())) - if (cast(O1->getType())->getElementType()->isSized()) { - // If the size of the other access is larger than the total size of the - // global/alloca/malloc, it cannot be accessing the global (it's - // undefined to load or store bytes before or after an object). - const Type *ElTy = cast(O1->getType())->getElementType(); - unsigned GlobalSize = getTargetData().getTypeSize(ElTy); - if (GlobalSize < V2Size && V2Size != ~0U) - return NoAlias; - } - } - - if (O2) { - if (!isa(O2) && isa(V1)) - return NoAlias; // Unique values don't alias null - - if (isa(O2) || - (isa(O2) && - !cast(O2)->isArrayAllocation())) - if (cast(O2->getType())->getElementType()->isSized()) { - // If the size of the other access is larger than the total size of the - // global/alloca/malloc, it cannot be accessing the object (it's - // undefined to load or store bytes before or after an object). - const Type *ElTy = cast(O2->getType())->getElementType(); - unsigned GlobalSize = getTargetData().getTypeSize(ElTy); - if (GlobalSize < V1Size && V1Size != ~0U) - return NoAlias; - } + // Most objects can't alias null. + if ((isa(V2) && isKnownNonNull(O1)) || + (isa(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. + const TargetData &TD = getTargetData(); + if ((V1Size != ~0U && isObjectSmallerThan(O2, V1Size, TD)) || + (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, 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(O1) || isa(O1)) && + isNonEscapingLocalObject(O2) && O1 != O2) + return NoAlias; + if ((isa(O2) || isa(O2)) && + isNonEscapingLocalObject(O1) && O1 != O2) + return NoAlias; + // 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)) { + const User *GEP1 = cast(V1); + const User *GEP2 = 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 alias(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. - const Value *BasePtr1 = V1, *BasePtr2 = V2; - do { - BasePtr1 = cast(BasePtr1)->getOperand(0); - } while (isGEP(BasePtr1) && - cast(BasePtr1)->getOperand(1) == - Constant::getNullValue(cast(BasePtr1)->getOperand(1)->getType())); - do { - BasePtr2 = cast(BasePtr2)->getOperand(0); - } while (isGEP(BasePtr2) && - cast(BasePtr2)->getOperand(1) == - Constant::getNullValue(cast(BasePtr2)->getOperand(1)->getType())); + while (isGEP(GEP1->getOperand(0)) && + GEP1->getOperand(1) == + Context.getNullValue(GEP1->getOperand(1)->getType())) + GEP1 = cast(GEP1->getOperand(0)); + const Value *BasePtr1 = GEP1->getOperand(0); + + while (isGEP(GEP2->getOperand(0)) && + GEP2->getOperand(1) == + Context.getNullValue(GEP2->getOperand(1)->getType())) + GEP2 = cast(GEP2->getOperand(0)); + const Value *BasePtr2 = GEP2->getOperand(0); // Do the base pointers alias? AliasResult BaseAlias = alias(BasePtr1, ~0U, BasePtr2, ~0U); @@ -446,7 +481,7 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, for (unsigned i = 0; i != GEPOperands.size(); ++i) if (!isa(GEPOperands[i])) GEPOperands[i] = - Constant::getNullValue(GEPOperands[i]->getType()); + Context.getNullValue(GEPOperands[i]->getType()); int64_t Offset = getTargetData().getIndexedOffset(BasePtr->getType(), &GEPOperands[0], @@ -462,18 +497,18 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, return MayAlias; } -// This function is used to determin if the indices of two GEP instructions are +// 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) { +static bool IndexOperandsEqual(Value *V1, Value *V2, LLVMContext &Context) { 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::Int64Ty) - C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); + C1 = Context.getConstantExprSExt(C1, Type::Int64Ty); if (C2->getType() != Type::Int64Ty) - C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); + C2 = Context.getConstantExprSExt(C2, Type::Int64Ty); return C1 == C2; } return false; @@ -494,6 +529,8 @@ BasicAliasAnalysis::CheckGEPInstructions( const PointerType *GEPPointerTy = cast(BasePtr1Ty); + LLVMContext &Context = GEPPointerTy->getContext(); + // Find the (possibly empty) initial sequence of equal values... which are not // necessarily constants. unsigned NumGEP1Operands = NumGEP1Ops, NumGEP2Operands = NumGEP2Ops; @@ -501,7 +538,8 @@ BasicAliasAnalysis::CheckGEPInstructions( unsigned MaxOperands = std::max(NumGEP1Operands, NumGEP2Operands); unsigned UnequalOper = 0; while (UnequalOper != MinOperands && - IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper])) { + IndexOperandsEqual(GEP1Ops[UnequalOper], GEP2Ops[UnequalOper], + Context)) { // Advance through the type as we go... ++UnequalOper; if (const CompositeType *CT = dyn_cast(BasePtr1Ty)) @@ -566,9 +604,9 @@ BasicAliasAnalysis::CheckGEPInstructions( if (G1OC->getType() != G2OC->getType()) { // Sign extend both operands to long. if (G1OC->getType() != Type::Int64Ty) - G1OC = ConstantExpr::getSExt(G1OC, Type::Int64Ty); + G1OC = Context.getConstantExprSExt(G1OC, Type::Int64Ty); if (G2OC->getType() != Type::Int64Ty) - G2OC = ConstantExpr::getSExt(G2OC, Type::Int64Ty); + G2OC = Context.getConstantExprSExt(G2OC, Type::Int64Ty); GEP1Ops[FirstConstantOper] = G1OC; GEP2Ops[FirstConstantOper] = G2OC; } @@ -576,18 +614,39 @@ BasicAliasAnalysis::CheckGEPInstructions( if (G1OC != G2OC) { // Handle the "be careful" case above: if this is an array/vector // subscript, scan for a subsequent variable array index. - if (isa(BasePtr1Ty)) { - const Type *NextTy = - cast(BasePtr1Ty)->getElementType(); + if (const SequentialType *STy = + dyn_cast(BasePtr1Ty)) { + const Type *NextTy = STy; bool isBadCase = false; - for (unsigned Idx = FirstConstantOper+1; + 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(); } @@ -630,11 +689,11 @@ BasicAliasAnalysis::CheckGEPInstructions( 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 suiteable for + // 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()); + GEP1Ops[i] = Context.getNullValue(GEP1Ops[i]->getType()); // Okay, now get the offset. This is the relative offset for the full // instruction. const TargetData &TD = getTargetData(); @@ -645,9 +704,15 @@ BasicAliasAnalysis::CheckGEPInstructions( 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; } } @@ -673,7 +738,7 @@ BasicAliasAnalysis::CheckGEPInstructions( const Type *ZeroIdxTy = GEPPointerTy; for (unsigned i = 0; i != FirstConstantOper; ++i) { if (!isa(ZeroIdxTy)) - GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Type::Int32Ty); + GEP1Ops[i] = GEP2Ops[i] = Context.getNullValue(Type::Int32Ty); if (const CompositeType *CT = dyn_cast(ZeroIdxTy)) ZeroIdxTy = CT->getTypeAtIndex(GEP1Ops[i]); @@ -688,7 +753,7 @@ BasicAliasAnalysis::CheckGEPInstructions( // If they are equal, use a zero index... if (Op1 == Op2 && BasePtr1Ty == BasePtr2Ty) { if (!isa(Op1)) - GEP1Ops[i] = GEP2Ops[i] = Constant::getNullValue(Op1->getType()); + GEP1Ops[i] = GEP2Ops[i] = Context.getNullValue(Op1->getType()); // Otherwise, just keep the constants we have. } else { if (Op1) { @@ -697,8 +762,8 @@ BasicAliasAnalysis::CheckGEPInstructions( 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 *PT = dyn_cast(BasePtr1Ty)) { - if (Op1C->getZExtValue() >= PT->getNumElements()) + } else if (const VectorType *VT = dyn_cast(BasePtr1Ty)) { + if (Op1C->getZExtValue() >= VT->getNumElements()) return MayAlias; // Be conservative with out-of-range accesses } @@ -714,25 +779,26 @@ BasicAliasAnalysis::CheckGEPInstructions( // value possible. // if (const ArrayType *AT = dyn_cast(BasePtr1Ty)) - GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,AT->getNumElements()-1); - else if (const VectorType *PT = dyn_cast(BasePtr1Ty)) - GEP1Ops[i] = ConstantInt::get(Type::Int64Ty,PT->getNumElements()-1); - + GEP1Ops[i] = + Context.getConstantInt(Type::Int64Ty,AT->getNumElements()-1); + else if (const VectorType *VT = dyn_cast(BasePtr1Ty)) + GEP1Ops[i] = + Context.getConstantInt(Type::Int64Ty,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(BasePtr1Ty)) { + 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 *PT = dyn_cast(BasePtr1Ty)) { - if (Op2C->getZExtValue() >= PT->getNumElements()) + } 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()); + GEP2Ops[i] = Context.getNullValue(Op2->getType()); } } } @@ -757,8 +823,13 @@ BasicAliasAnalysis::CheckGEPInstructions( getTargetData().getIndexedOffset(GEPPointerTy, GEP1Ops, NumGEP1Ops); int64_t Offset2 = getTargetData().getIndexedOffset(GEPPointerTy, GEP2Ops, NumGEP2Ops); - assert(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; @@ -768,123 +839,5 @@ BasicAliasAnalysis::CheckGEPInstructions( return MayAlias; } -namespace { - struct VISIBILITY_HIDDEN StringCompare { - bool operator()(const char *LHS, const char *RHS) { - return strcmp(LHS, RHS) < 0; - } - }; -} - -// Note that this list cannot contain libm functions (such as acos and sqrt) -// that set errno on a domain or other error. -static const char *DoesntAccessMemoryFns[] = { - "abs", "labs", "llabs", "imaxabs", "fabs", "fabsf", "fabsl", - "trunc", "truncf", "truncl", "ldexp", - - "atan", "atanf", "atanl", "atan2", "atan2f", "atan2l", - "cbrt", - "cos", "cosf", "cosl", - "exp", "expf", "expl", - "hypot", - "sin", "sinf", "sinl", - "tan", "tanf", "tanl", "tanh", "tanhf", "tanhl", - - "floor", "floorf", "floorl", "ceil", "ceilf", "ceill", - - // ctype.h - "isalnum", "isalpha", "iscntrl", "isdigit", "isgraph", "islower", "isprint" - "ispunct", "isspace", "isupper", "isxdigit", "tolower", "toupper", - - // wctype.h" - "iswalnum", "iswalpha", "iswcntrl", "iswdigit", "iswgraph", "iswlower", - "iswprint", "iswpunct", "iswspace", "iswupper", "iswxdigit", - - "iswctype", "towctrans", "towlower", "towupper", - - "btowc", "wctob", - - "isinf", "isnan", "finite", - - // C99 math functions - "copysign", "copysignf", "copysignd", - "nexttoward", "nexttowardf", "nexttowardd", - "nextafter", "nextafterf", "nextafterd", - - // ISO C99: - "__signbit", "__signbitf", "__signbitl", -}; - - -static const char *OnlyReadsMemoryFns[] = { - "atoi", "atol", "atof", "atoll", "atoq", "a64l", - "bcmp", "memcmp", "memchr", "memrchr", "wmemcmp", "wmemchr", - - // Strings - "strcmp", "strcasecmp", "strcoll", "strncmp", "strncasecmp", - "strchr", "strcspn", "strlen", "strpbrk", "strrchr", "strspn", "strstr", - "index", "rindex", - - // Wide char strings - "wcschr", "wcscmp", "wcscoll", "wcscspn", "wcslen", "wcsncmp", "wcspbrk", - "wcsrchr", "wcsspn", "wcsstr", - - // glibc - "alphasort", "alphasort64", "versionsort", "versionsort64", - - // C99 - "nan", "nanf", "nand", - - // File I/O - "feof", "ferror", "fileno", - "feof_unlocked", "ferror_unlocked", "fileno_unlocked" -}; - -static ManagedStatic > NoMemoryTable; -static ManagedStatic > OnlyReadsMemoryTable; - - -AliasAnalysis::ModRefBehavior -BasicAliasAnalysis::getModRefBehavior(Function *F, CallSite CS, - std::vector *Info) { - if (!F->isDeclaration()) return UnknownModRefBehavior; - - static bool Initialized = false; - if (!Initialized) { - NoMemoryTable->insert(NoMemoryTable->end(), - DoesntAccessMemoryFns, - DoesntAccessMemoryFns+ - sizeof(DoesntAccessMemoryFns)/sizeof(DoesntAccessMemoryFns[0])); - - OnlyReadsMemoryTable->insert(OnlyReadsMemoryTable->end(), - OnlyReadsMemoryFns, - OnlyReadsMemoryFns+ - sizeof(OnlyReadsMemoryFns)/sizeof(OnlyReadsMemoryFns[0])); -#define GET_MODREF_BEHAVIOR -#include "llvm/Intrinsics.gen" -#undef GET_MODREF_BEHAVIOR - - // Sort the table the first time through. - std::sort(NoMemoryTable->begin(), NoMemoryTable->end(), StringCompare()); - std::sort(OnlyReadsMemoryTable->begin(), OnlyReadsMemoryTable->end(), - StringCompare()); - Initialized = true; - } - - std::vector::iterator Ptr = - std::lower_bound(NoMemoryTable->begin(), NoMemoryTable->end(), - F->getName().c_str(), StringCompare()); - if (Ptr != NoMemoryTable->end() && *Ptr == F->getName()) - return DoesNotAccessMemory; - - Ptr = std::lower_bound(OnlyReadsMemoryTable->begin(), - OnlyReadsMemoryTable->end(), - F->getName().c_str(), StringCompare()); - if (Ptr != OnlyReadsMemoryTable->end() && *Ptr == F->getName()) - return OnlyReadsMemory; - - return UnknownModRefBehavior; -} - // Make sure that anything that uses AliasAnalysis pulls in this file... DEFINING_FILE_FOR(BasicAliasAnalysis)