X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;ds=sidebyside;f=lib%2FAnalysis%2FBasicAliasAnalysis.cpp;h=279ff0603f1fa916c0aabc79bccc5a5c47cf2b3e;hb=d04a8d4b33ff316ca4cf961e06c9e312eff8e64f;hp=23b89ddf75f68011896180ca4eb8e3194e40a3b5;hpb=1680a24e534f3066f99fa6b8a618e71373e2920c;p=oota-llvm.git diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index 23b89ddf75f..279ff0603f1 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -13,9 +13,16 @@ // //===----------------------------------------------------------------------===// -#include "llvm/Analysis/AliasAnalysis.h" #include "llvm/Analysis/Passes.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Analysis/CaptureTracking.h" +#include "llvm/Analysis/InstructionSimplify.h" +#include "llvm/Analysis/MemoryBuiltins.h" +#include "llvm/Analysis/ValueTracking.h" #include "llvm/Constants.h" +#include "llvm/DataLayout.h" #include "llvm/DerivedTypes.h" #include "llvm/Function.h" #include "llvm/GlobalAlias.h" @@ -25,16 +32,9 @@ #include "llvm/LLVMContext.h" #include "llvm/Operator.h" #include "llvm/Pass.h" -#include "llvm/Analysis/CaptureTracking.h" -#include "llvm/Analysis/MemoryBuiltins.h" -#include "llvm/Analysis/InstructionSimplify.h" -#include "llvm/Analysis/ValueTracking.h" -#include "llvm/Target/TargetData.h" -#include "llvm/Target/TargetLibraryInfo.h" -#include "llvm/ADT/SmallPtrSet.h" -#include "llvm/ADT/SmallVector.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/GetElementPtrTypeIterator.h" +#include "llvm/Target/TargetLibraryInfo.h" #include using namespace llvm; @@ -58,12 +58,12 @@ static bool isNonEscapingLocalObject(const Value *V) { // 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; + if (A->hasByValAttr() || A->hasNoAliasAttr()) + // Note even if the argument is marked nocapture we still need to check + // for copies made inside the function. The nocapture attribute only + // specifies that there are no copies made that outlive the function. return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true); - } + return false; } @@ -84,58 +84,23 @@ static bool isEscapeSource(const Value *V) { /// getObjectSize - Return the size of the object specified by V, or /// UnknownSize if unknown. -static uint64_t getObjectSize(const Value *V, const TargetData &TD, +static uint64_t getObjectSize(const Value *V, const DataLayout &TD, + const TargetLibraryInfo &TLI, bool RoundToAlign = false) { - Type *AccessTy; - unsigned Align; - if (const GlobalVariable *GV = dyn_cast(V)) { - if (!GV->hasDefinitiveInitializer()) - return AliasAnalysis::UnknownSize; - AccessTy = GV->getType()->getElementType(); - Align = GV->getAlignment(); - } else if (const AllocaInst *AI = dyn_cast(V)) { - if (!AI->isArrayAllocation()) - AccessTy = AI->getType()->getElementType(); - else - return AliasAnalysis::UnknownSize; - Align = AI->getAlignment(); - } else if (const CallInst* CI = extractMallocCall(V)) { - if (!RoundToAlign && !isArrayMalloc(V, &TD)) - // The size is the argument to the malloc call. - if (const ConstantInt* C = dyn_cast(CI->getArgOperand(0))) - return C->getZExtValue(); - return AliasAnalysis::UnknownSize; - } else if (const Argument *A = dyn_cast(V)) { - if (A->hasByValAttr()) { - AccessTy = cast(A->getType())->getElementType(); - Align = A->getParamAlignment(); - } else { - return AliasAnalysis::UnknownSize; - } - } else { - return AliasAnalysis::UnknownSize; - } - - if (!AccessTy->isSized()) - return AliasAnalysis::UnknownSize; - - uint64_t Size = TD.getTypeAllocSize(AccessTy); - if (RoundToAlign) { - if (!Align) - return AliasAnalysis::UnknownSize; - Size = RoundUpToAlignment(Size, Align); - } - - return Size; + uint64_t Size; + if (getObjectSize(V, Size, &TD, &TLI, RoundToAlign)) + return Size; + return AliasAnalysis::UnknownSize; } /// isObjectSmallerThan - Return true if we can prove that the object specified /// by V is smaller than Size. static bool isObjectSmallerThan(const Value *V, uint64_t Size, - const TargetData &TD) { + const DataLayout &TD, + const TargetLibraryInfo &TLI) { // This function needs to use the aligned object size because we allow // reads a bit past the end given sufficient alignment. - uint64_t ObjectSize = getObjectSize(V, TD, /*RoundToAlign*/true); + uint64_t ObjectSize = getObjectSize(V, TD, TLI, /*RoundToAlign*/true); return ObjectSize != AliasAnalysis::UnknownSize && ObjectSize < Size; } @@ -143,8 +108,8 @@ static bool isObjectSmallerThan(const Value *V, uint64_t Size, /// isObjectSize - Return true if we can prove that the object specified /// by V has size Size. static bool isObjectSize(const Value *V, uint64_t Size, - const TargetData &TD) { - uint64_t ObjectSize = getObjectSize(V, TD); + const DataLayout &TD, const TargetLibraryInfo &TLI) { + uint64_t ObjectSize = getObjectSize(V, TD, TLI); return ObjectSize != AliasAnalysis::UnknownSize && ObjectSize == Size; } @@ -163,6 +128,15 @@ namespace { const Value *V; ExtensionKind Extension; int64_t Scale; + + bool operator==(const VariableGEPIndex &Other) const { + return V == Other.V && Extension == Other.Extension && + Scale == Other.Scale; + } + + bool operator!=(const VariableGEPIndex &Other) const { + return !operator==(Other); + } }; } @@ -177,7 +151,7 @@ namespace { /// represented in the result. static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset, ExtensionKind &Extension, - const TargetData &TD, unsigned Depth) { + const DataLayout &TD, unsigned Depth) { assert(V->getType()->isIntegerTy() && "Not an integer value"); // Limit our recursion depth. @@ -252,14 +226,14 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset, /// specified amount, but which may have other unrepresented high bits. As such, /// the gep cannot necessarily be reconstructed from its decomposed form. /// -/// When TargetData is around, this function is capable of analyzing everything +/// When DataLayout is around, this function is capable of analyzing everything /// that GetUnderlyingObject can look through. When not, it just looks /// through pointer casts. /// static const Value * DecomposeGEPExpression(const Value *V, int64_t &BaseOffs, SmallVectorImpl &VarIndices, - const TargetData *TD) { + const DataLayout *TD) { // Limit recursion depth to limit compile time in crazy cases. unsigned MaxLookup = 6; @@ -303,7 +277,7 @@ DecomposeGEPExpression(const Value *V, int64_t &BaseOffs, ->getElementType()->isSized()) return V; - // If we are lacking TargetData information, we can't compute the offets of + // If we are lacking DataLayout information, we can't compute the offets of // elements computed by GEPs. However, we can handle bitcast equivalent // GEPs. if (TD == 0) { @@ -454,13 +428,7 @@ namespace { /// BasicAliasAnalysis - This is the primary alias analysis implementation. struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis { static char ID; // Class identification, replacement for typeinfo - BasicAliasAnalysis() : ImmutablePass(ID), - // AliasCache rarely has more than 1 or 2 elements, - // so start it off fairly small so that clear() - // doesn't have to tromp through 64 (the default) - // elements on each alias query. This really wants - // something like a SmallDenseMap. - AliasCache(8) { + BasicAliasAnalysis() : ImmutablePass(ID) { initializeBasicAliasAnalysisPass(*PassRegistry::getPassRegistry()); } @@ -480,7 +448,11 @@ namespace { "BasicAliasAnalysis doesn't support interprocedural queries."); AliasResult Alias = aliasCheck(LocA.Ptr, LocA.Size, LocA.TBAATag, LocB.Ptr, LocB.Size, LocB.TBAATag); - AliasCache.clear(); + // AliasCache rarely has more than 1 or 2 elements, always use + // shrink_and_clear so it quickly returns to the inline capacity of the + // SmallDenseMap if it ever grows larger. + // FIXME: This should really be shrink_to_inline_capacity_and_clear(). + AliasCache.shrink_and_clear(); return Alias; } @@ -518,7 +490,7 @@ namespace { private: // AliasCache - Track alias queries to guard against recursion. typedef std::pair LocPair; - typedef DenseMap AliasCacheTy; + typedef SmallDenseMap AliasCacheTy; AliasCacheTy AliasCache; // Visited - Track instructions visited by pointsToConstantMemory. @@ -527,6 +499,7 @@ namespace { // aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP // instruction against another. AliasResult aliasGEP(const GEPOperator *V1, uint64_t V1Size, + const MDNode *V1TBAAInfo, const Value *V2, uint64_t V2Size, const MDNode *V2TBAAInfo, const Value *UnderlyingV1, const Value *UnderlyingV2); @@ -844,6 +817,21 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS, return ModRefResult(AliasAnalysis::getModRefInfo(CS, Loc) & Min); } +static bool areVarIndicesEqual(SmallVector &Indices1, + SmallVector &Indices2) { + unsigned Size1 = Indices1.size(); + unsigned Size2 = Indices2.size(); + + if (Size1 != Size2) + return false; + + for (unsigned I = 0; I != Size1; ++I) + if (Indices1[I] != Indices2[I]) + return false; + + return true; +} + /// 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 /// anything about V2. UnderlyingV1 is GetUnderlyingObject(GEP1, TD), @@ -851,6 +839,7 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS, /// AliasAnalysis::AliasResult BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size, + const MDNode *V1TBAAInfo, const Value *V2, uint64_t V2Size, const MDNode *V2TBAAInfo, const Value *UnderlyingV1, @@ -858,9 +847,41 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size, int64_t GEP1BaseOffset; SmallVector 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. + // If we have two gep instructions with must-alias or not-alias'ing base + // pointers, figure out if the indexes to the GEP tell us anything about the + // derived pointer. if (const GEPOperator *GEP2 = dyn_cast(V2)) { + // Check for geps of non-aliasing underlying pointers where the offsets are + // identical. + if (V1Size == V2Size) { + // Do the base pointers alias assuming type and size. + AliasResult PreciseBaseAlias = aliasCheck(UnderlyingV1, V1Size, + V1TBAAInfo, UnderlyingV2, + V2Size, V2TBAAInfo); + if (PreciseBaseAlias == NoAlias) { + // See if the computed offset from the common pointer tells us about the + // relation of the resulting pointer. + int64_t GEP2BaseOffset; + SmallVector GEP2VariableIndices; + const Value *GEP2BasePtr = + DecomposeGEPExpression(GEP2, GEP2BaseOffset, GEP2VariableIndices, TD); + const Value *GEP1BasePtr = + DecomposeGEPExpression(GEP1, GEP1BaseOffset, GEP1VariableIndices, TD); + // DecomposeGEPExpression and GetUnderlyingObject should return the + // same result except when DecomposeGEPExpression has no DataLayout. + if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) { + assert(TD == 0 && + "DecomposeGEPExpression and GetUnderlyingObject disagree!"); + return MayAlias; + } + // Same offsets. + if (GEP1BaseOffset == GEP2BaseOffset && + areVarIndicesEqual(GEP1VariableIndices, GEP2VariableIndices)) + return NoAlias; + GEP1VariableIndices.clear(); + } + } + // Do the base pointers alias? AliasResult BaseAlias = aliasCheck(UnderlyingV1, UnknownSize, 0, UnderlyingV2, UnknownSize, 0); @@ -880,9 +901,8 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size, 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. + // DecomposeGEPExpression and GetUnderlyingObject should return the + // same result except when DecomposeGEPExpression has no DataLayout. if (GEP1BasePtr != UnderlyingV1 || GEP2BasePtr != UnderlyingV2) { assert(TD == 0 && "DecomposeGEPExpression and GetUnderlyingObject disagree!"); @@ -916,9 +936,8 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size, 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. + // DecomposeGEPExpression and GetUnderlyingObject should return the + // same result except when DecomposeGEPExpression has no DataLayout. if (GEP1BasePtr != UnderlyingV1) { assert(TD == 0 && "DecomposeGEPExpression and GetUnderlyingObject disagree!"); @@ -1041,13 +1060,52 @@ BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize, // on corresponding edges. if (const PHINode *PN2 = dyn_cast(V2)) if (PN2->getParent() == PN->getParent()) { + LocPair Locs(Location(PN, PNSize, PNTBAAInfo), + Location(V2, V2Size, V2TBAAInfo)); + if (PN > V2) + std::swap(Locs.first, Locs.second); + + // Find the first incoming phi value not from its parent. + unsigned f = 0; + while (PN->getIncomingBlock(f) == PN->getParent() && + f < PN->getNumIncomingValues()-1) + ++f; + AliasResult Alias = - aliasCheck(PN->getIncomingValue(0), PNSize, PNTBAAInfo, - PN2->getIncomingValueForBlock(PN->getIncomingBlock(0)), + aliasCheck(PN->getIncomingValue(f), PNSize, PNTBAAInfo, + PN2->getIncomingValueForBlock(PN->getIncomingBlock(f)), V2Size, V2TBAAInfo); if (Alias == MayAlias) return MayAlias; - for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) { + + // If the first source of the PHI nodes NoAlias and the other inputs are + // the PHI node itself through some amount of recursion this does not add + // any new information so just return NoAlias. + // bb: + // ptr = ptr2 + 1 + // loop: + // ptr_phi = phi [bb, ptr], [loop, ptr_plus_one] + // ptr2_phi = phi [bb, ptr2], [loop, ptr2_plus_one] + // ... + // ptr_plus_one = gep ptr_phi, 1 + // ptr2_plus_one = gep ptr2_phi, 1 + // We assume for the recursion that the the phis (ptr_phi, ptr2_phi) do + // not alias each other. + bool ArePhisAssumedNoAlias = false; + AliasResult OrigAliasResult = NoAlias; + if (Alias == NoAlias) { + // Pretend the phis do not alias. + assert(AliasCache.count(Locs) && + "There must exist an entry for the phi node"); + OrigAliasResult = AliasCache[Locs]; + AliasCache[Locs] = NoAlias; + ArePhisAssumedNoAlias = true; + } + + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { + if (i == f) + continue; + AliasResult ThisAlias = aliasCheck(PN->getIncomingValue(i), PNSize, PNTBAAInfo, PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)), @@ -1056,6 +1114,11 @@ BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize, if (Alias == MayAlias) break; } + + // Reset if speculation failed. + if (ArePhisAssumedNoAlias && Alias != NoAlias) + AliasCache[Locs] = OrigAliasResult; + return Alias; } @@ -1170,8 +1233,8 @@ BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size, // If the size of one access is larger than the entire object on the other // side, then we know such behavior is undefined and can assume no alias. if (TD) - if ((V1Size != UnknownSize && isObjectSmallerThan(O2, V1Size, *TD)) || - (V2Size != UnknownSize && isObjectSmallerThan(O1, V2Size, *TD))) + if ((V1Size != UnknownSize && isObjectSmallerThan(O2, V1Size, *TD, *TLI)) || + (V2Size != UnknownSize && isObjectSmallerThan(O1, V2Size, *TD, *TLI))) return NoAlias; // Check the cache before climbing up use-def chains. This also terminates @@ -1191,15 +1254,17 @@ BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size, std::swap(V1, V2); std::swap(V1Size, V2Size); std::swap(O1, O2); + std::swap(V1TBAAInfo, V2TBAAInfo); } if (const GEPOperator *GV1 = dyn_cast(V1)) { - AliasResult Result = aliasGEP(GV1, V1Size, V2, V2Size, V2TBAAInfo, O1, O2); + AliasResult Result = aliasGEP(GV1, V1Size, V1TBAAInfo, V2, V2Size, V2TBAAInfo, O1, O2); if (Result != MayAlias) return AliasCache[Locs] = Result; } if (isa(V2) && !isa(V1)) { std::swap(V1, V2); std::swap(V1Size, V2Size); + std::swap(V1TBAAInfo, V2TBAAInfo); } if (const PHINode *PN = dyn_cast(V1)) { AliasResult Result = aliasPHI(PN, V1Size, V1TBAAInfo, @@ -1210,6 +1275,7 @@ BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size, if (isa(V2) && !isa(V1)) { std::swap(V1, V2); std::swap(V1Size, V2Size); + std::swap(V1TBAAInfo, V2TBAAInfo); } if (const SelectInst *S1 = dyn_cast(V1)) { AliasResult Result = aliasSelect(S1, V1Size, V1TBAAInfo, @@ -1221,8 +1287,8 @@ BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size, // accesses is accessing the entire object, then the accesses must // overlap in some way. if (TD && O1 == O2) - if ((V1Size != UnknownSize && isObjectSize(O1, V1Size, *TD)) || - (V2Size != UnknownSize && isObjectSize(O2, V2Size, *TD))) + if ((V1Size != UnknownSize && isObjectSize(O1, V1Size, *TD, *TLI)) || + (V2Size != UnknownSize && isObjectSize(O2, V2Size, *TD, *TLI))) return AliasCache[Locs] = PartialAlias; AliasResult Result =