X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FAnalysis%2FAliasAnalysis.cpp;h=5171a45674568b346db6851547325eed75833466;hp=d01320c141c8273f2ecb69e226c26e28d9fbfb9f;hb=81ae170379339d924e746501718615af2a354d68;hpb=db4708cf86cece22539ff022cc0601612dd02ead diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp index d01320c141c..5171a456745 100644 --- a/lib/Analysis/AliasAnalysis.cpp +++ b/lib/Analysis/AliasAnalysis.cpp @@ -25,14 +25,19 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Analysis/CFG.h" +#include "llvm/Analysis/CaptureTracking.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/BasicBlock.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/Type.h" #include "llvm/Pass.h" -#include "llvm/BasicBlock.h" -#include "llvm/Function.h" -#include "llvm/IntrinsicInst.h" -#include "llvm/Instructions.h" -#include "llvm/LLVMContext.h" -#include "llvm/Type.h" -#include "llvm/Target/TargetData.h" +#include "llvm/Target/TargetLibraryInfo.h" using namespace llvm; // Register the AliasAnalysis interface, providing a nice name to refer to. @@ -49,9 +54,17 @@ AliasAnalysis::alias(const Location &LocA, const Location &LocB) { return AA->alias(LocA, LocB); } -bool AliasAnalysis::pointsToConstantMemory(const Location &Loc) { +bool AliasAnalysis::pointsToConstantMemory(const Location &Loc, + bool OrLocal) { assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!"); - return AA->pointsToConstantMemory(Loc); + return AA->pointsToConstantMemory(Loc, OrLocal); +} + +AliasAnalysis::Location +AliasAnalysis::getArgLocation(ImmutableCallSite CS, unsigned ArgIdx, + AliasAnalysis::ModRefResult &Mask) { + assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!"); + return AA->getArgLocation(CS, ArgIdx, Mask); } void AliasAnalysis::deleteValue(Value *V) { @@ -64,30 +77,47 @@ void AliasAnalysis::copyValue(Value *From, Value *To) { AA->copyValue(From, To); } +void AliasAnalysis::addEscapingUse(Use &U) { + assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!"); + AA->addEscapingUse(U); +} + + AliasAnalysis::ModRefResult AliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) { - // Don't assert AA because BasicAA calls us in order to make use of the - // logic here. + assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!"); ModRefBehavior MRB = getModRefBehavior(CS); if (MRB == DoesNotAccessMemory) return NoModRef; ModRefResult Mask = ModRef; - if (MRB == OnlyReadsMemory) + if (onlyReadsMemory(MRB)) Mask = Ref; - else if (MRB == AliasAnalysis::AccessesArguments) { + + if (onlyAccessesArgPointees(MRB)) { bool doesAlias = false; - for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end(); - AI != AE; ++AI) - if (!isNoAlias(Location(*AI), Loc)) { - doesAlias = true; - break; + ModRefResult AllArgsMask = NoModRef; + if (doesAccessArgPointees(MRB)) { + for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end(); + AI != AE; ++AI) { + const Value *Arg = *AI; + if (!Arg->getType()->isPointerTy()) + continue; + ModRefResult ArgMask; + Location CSLoc = + getArgLocation(CS, (unsigned) std::distance(CS.arg_begin(), AI), + ArgMask); + if (!isNoAlias(CSLoc, Loc)) { + doesAlias = true; + AllArgsMask = ModRefResult(AllArgsMask | ArgMask); + } } - + } if (!doesAlias) return NoModRef; + Mask = ModRefResult(Mask & AllArgsMask); } // If Loc is a constant memory location, the call definitely could not @@ -95,7 +125,7 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS, if ((Mask & Mod) && pointsToConstantMemory(Loc)) Mask = ModRefResult(Mask & ~Mod); - // If this is BasicAA, don't forward. + // If this is the end of the chain, don't forward. if (!AA) return Mask; // Otherwise, fall back to the next AA in the chain. But we can merge @@ -105,8 +135,7 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS, AliasAnalysis::ModRefResult AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) { - // Don't assert AA because BasicAA calls us in order to make use of the - // logic here. + assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!"); // If CS1 or CS2 are readnone, they don't interact. ModRefBehavior CS1B = getModRefBehavior(CS1); @@ -116,45 +145,75 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) { if (CS2B == DoesNotAccessMemory) return NoModRef; // If they both only read from memory, there is no dependence. - if (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory) + if (onlyReadsMemory(CS1B) && onlyReadsMemory(CS2B)) return NoModRef; AliasAnalysis::ModRefResult Mask = ModRef; // If CS1 only reads memory, the only dependence on CS2 can be // from CS1 reading memory written by CS2. - if (CS1B == OnlyReadsMemory) + if (onlyReadsMemory(CS1B)) Mask = ModRefResult(Mask & Ref); // If CS2 only access memory through arguments, accumulate the mod/ref // information from CS1's references to the memory referenced by // CS2's arguments. - if (CS2B == AccessesArguments) { + if (onlyAccessesArgPointees(CS2B)) { AliasAnalysis::ModRefResult R = NoModRef; - for (ImmutableCallSite::arg_iterator - I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) { - R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask); - if (R == Mask) - break; + if (doesAccessArgPointees(CS2B)) { + for (ImmutableCallSite::arg_iterator + I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) { + const Value *Arg = *I; + if (!Arg->getType()->isPointerTy()) + continue; + ModRefResult ArgMask; + Location CS2Loc = + getArgLocation(CS2, (unsigned) std::distance(CS2.arg_begin(), I), + ArgMask); + // ArgMask indicates what CS2 might do to CS2Loc, and the dependence of + // CS1 on that location is the inverse. + if (ArgMask == Mod) + ArgMask = ModRef; + else if (ArgMask == Ref) + ArgMask = Mod; + + R = ModRefResult((R | (getModRefInfo(CS1, CS2Loc) & ArgMask)) & Mask); + if (R == Mask) + break; + } } return R; } // If CS1 only accesses memory through arguments, check if CS2 references // any of the memory referenced by CS1's arguments. If not, return NoModRef. - if (CS1B == AccessesArguments) { + if (onlyAccessesArgPointees(CS1B)) { AliasAnalysis::ModRefResult R = NoModRef; - for (ImmutableCallSite::arg_iterator - I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) - if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) { - R = Mask; - break; + if (doesAccessArgPointees(CS1B)) { + for (ImmutableCallSite::arg_iterator + I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) { + const Value *Arg = *I; + if (!Arg->getType()->isPointerTy()) + continue; + ModRefResult ArgMask; + Location CS1Loc = getArgLocation( + CS1, (unsigned)std::distance(CS1.arg_begin(), I), ArgMask); + // ArgMask indicates what CS1 might do to CS1Loc; if CS1 might Mod + // CS1Loc, then we care about either a Mod or a Ref by CS2. If CS1 + // might Ref, then we care only about a Mod by CS2. + ModRefResult ArgR = getModRefInfo(CS2, CS1Loc); + if (((ArgMask & Mod) != NoModRef && (ArgR & ModRef) != NoModRef) || + ((ArgMask & Ref) != NoModRef && (ArgR & Mod) != NoModRef)) + R = ModRefResult((R | ArgMask) & Mask); + + if (R == Mask) + break; } - if (R == NoModRef) - return R; + } + return R; } - // If this is BasicAA, don't forward. + // If this is the end of the chain, don't forward. if (!AA) return Mask; // Otherwise, fall back to the next AA in the chain. But we can merge @@ -164,8 +223,7 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) { AliasAnalysis::ModRefBehavior AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) { - // Don't assert AA because BasicAA calls us in order to make use of the - // logic here. + assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!"); ModRefBehavior Min = UnknownModRefBehavior; @@ -174,12 +232,12 @@ AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) { if (const Function *F = CS.getCalledFunction()) Min = getModRefBehavior(F); - // If this is BasicAA, don't forward. + // If this is the end of the chain, don't forward. if (!AA) return Min; // Otherwise, fall back to the next AA in the chain. But we can merge // in any result we've managed to compute. - return std::min(AA->getModRefBehavior(CS), Min); + return ModRefBehavior(AA->getModRefBehavior(CS) & Min); } AliasAnalysis::ModRefBehavior @@ -192,18 +250,87 @@ AliasAnalysis::getModRefBehavior(const Function *F) { // AliasAnalysis non-virtual helper method implementation //===----------------------------------------------------------------------===// +AliasAnalysis::Location AliasAnalysis::getLocation(const LoadInst *LI) { + AAMDNodes AATags; + LI->getAAMetadata(AATags); + + return Location(LI->getPointerOperand(), + getTypeStoreSize(LI->getType()), AATags); +} + +AliasAnalysis::Location AliasAnalysis::getLocation(const StoreInst *SI) { + AAMDNodes AATags; + SI->getAAMetadata(AATags); + + return Location(SI->getPointerOperand(), + getTypeStoreSize(SI->getValueOperand()->getType()), AATags); +} + +AliasAnalysis::Location AliasAnalysis::getLocation(const VAArgInst *VI) { + AAMDNodes AATags; + VI->getAAMetadata(AATags); + + return Location(VI->getPointerOperand(), UnknownSize, AATags); +} + +AliasAnalysis::Location +AliasAnalysis::getLocation(const AtomicCmpXchgInst *CXI) { + AAMDNodes AATags; + CXI->getAAMetadata(AATags); + + return Location(CXI->getPointerOperand(), + getTypeStoreSize(CXI->getCompareOperand()->getType()), + AATags); +} + +AliasAnalysis::Location +AliasAnalysis::getLocation(const AtomicRMWInst *RMWI) { + AAMDNodes AATags; + RMWI->getAAMetadata(AATags); + + return Location(RMWI->getPointerOperand(), + getTypeStoreSize(RMWI->getValOperand()->getType()), AATags); +} + +AliasAnalysis::Location +AliasAnalysis::getLocationForSource(const MemTransferInst *MTI) { + uint64_t Size = UnknownSize; + if (ConstantInt *C = dyn_cast(MTI->getLength())) + Size = C->getValue().getZExtValue(); + + // memcpy/memmove can have AA tags. For memcpy, they apply + // to both the source and the destination. + AAMDNodes AATags; + MTI->getAAMetadata(AATags); + + return Location(MTI->getRawSource(), Size, AATags); +} + +AliasAnalysis::Location +AliasAnalysis::getLocationForDest(const MemIntrinsic *MTI) { + uint64_t Size = UnknownSize; + if (ConstantInt *C = dyn_cast(MTI->getLength())) + Size = C->getValue().getZExtValue(); + + // memcpy/memmove can have AA tags. For memcpy, they apply + // to both the source and the destination. + AAMDNodes AATags; + MTI->getAAMetadata(AATags); + + return Location(MTI->getRawDest(), Size, AATags); +} + + + AliasAnalysis::ModRefResult AliasAnalysis::getModRefInfo(const LoadInst *L, const Location &Loc) { - // Be conservative in the face of volatile. - if (L->isVolatile()) + // Be conservative in the face of volatile/atomic. + if (!L->isUnordered()) return ModRef; // If the load address doesn't alias the given address, it doesn't read // or write the specified memory. - if (!alias(Location(L->getOperand(0), - getTypeStoreSize(L->getType()), - L->getMetadata(LLVMContext::MD_tbaa)), - Loc)) + if (!alias(getLocation(L), Loc)) return NoModRef; // Otherwise, a load just reads. @@ -212,16 +339,13 @@ AliasAnalysis::getModRefInfo(const LoadInst *L, const Location &Loc) { AliasAnalysis::ModRefResult AliasAnalysis::getModRefInfo(const StoreInst *S, const Location &Loc) { - // Be conservative in the face of volatile. - if (S->isVolatile()) + // Be conservative in the face of volatile/atomic. + if (!S->isUnordered()) return ModRef; // If the store address cannot alias the pointer in question, then the // specified memory cannot be modified by the store. - if (!alias(Location(S->getOperand(1), - getTypeStoreSize(S->getOperand(0)->getType()), - S->getMetadata(LLVMContext::MD_tbaa)), - Loc)) + if (!alias(getLocation(S), Loc)) return NoModRef; // If the pointer is a pointer to constant memory, then it could not have been @@ -237,10 +361,7 @@ AliasAnalysis::ModRefResult AliasAnalysis::getModRefInfo(const VAArgInst *V, const Location &Loc) { // If the va_arg address cannot alias the pointer in question, then the // specified memory cannot be accessed by the va_arg. - if (!alias(Location(V->getOperand(0), - UnknownSize, - V->getMetadata(LLVMContext::MD_tbaa)), - Loc)) + if (!alias(getLocation(V), Loc)) return NoModRef; // If the pointer is a pointer to constant memory, then it could not have been @@ -252,11 +373,83 @@ AliasAnalysis::getModRefInfo(const VAArgInst *V, const Location &Loc) { return ModRef; } -AliasAnalysis::ModRefBehavior -AliasAnalysis::getIntrinsicModRefBehavior(unsigned iid) { -#define GET_INTRINSIC_MODREF_BEHAVIOR -#include "llvm/Intrinsics.gen" -#undef GET_INTRINSIC_MODREF_BEHAVIOR +AliasAnalysis::ModRefResult +AliasAnalysis::getModRefInfo(const AtomicCmpXchgInst *CX, const Location &Loc) { + // Acquire/Release cmpxchg has properties that matter for arbitrary addresses. + if (CX->getSuccessOrdering() > Monotonic) + return ModRef; + + // If the cmpxchg address does not alias the location, it does not access it. + if (!alias(getLocation(CX), Loc)) + return NoModRef; + + return ModRef; +} + +AliasAnalysis::ModRefResult +AliasAnalysis::getModRefInfo(const AtomicRMWInst *RMW, const Location &Loc) { + // Acquire/Release atomicrmw has properties that matter for arbitrary addresses. + if (RMW->getOrdering() > Monotonic) + return ModRef; + + // If the atomicrmw address does not alias the location, it does not access it. + if (!alias(getLocation(RMW), Loc)) + return NoModRef; + + return ModRef; +} + +// FIXME: this is really just shoring-up a deficiency in alias analysis. +// BasicAA isn't willing to spend linear time determining whether an alloca +// was captured before or after this particular call, while we are. However, +// with a smarter AA in place, this test is just wasting compile time. +AliasAnalysis::ModRefResult +AliasAnalysis::callCapturesBefore(const Instruction *I, + const AliasAnalysis::Location &MemLoc, + DominatorTree *DT) { + if (!DT || !DL) return AliasAnalysis::ModRef; + + const Value *Object = GetUnderlyingObject(MemLoc.Ptr, DL); + if (!isIdentifiedObject(Object) || isa(Object) || + isa(Object)) + return AliasAnalysis::ModRef; + + ImmutableCallSite CS(I); + if (!CS.getInstruction() || CS.getInstruction() == Object) + return AliasAnalysis::ModRef; + + if (llvm::PointerMayBeCapturedBefore(Object, /* ReturnCaptures */ true, + /* StoreCaptures */ true, I, DT, + /* include Object */ true)) + return AliasAnalysis::ModRef; + + unsigned ArgNo = 0; + AliasAnalysis::ModRefResult R = AliasAnalysis::NoModRef; + for (ImmutableCallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end(); + CI != CE; ++CI, ++ArgNo) { + // Only look at the no-capture or byval pointer arguments. If this + // pointer were passed to arguments that were neither of these, then it + // couldn't be no-capture. + if (!(*CI)->getType()->isPointerTy() || + (!CS.doesNotCapture(ArgNo) && !CS.isByValArgument(ArgNo))) + continue; + + // If this is a no-capture pointer argument, see if we can tell that it + // is impossible to alias the pointer we're checking. If not, we have to + // assume that the call could touch the pointer, even though it doesn't + // escape. + if (isNoAlias(AliasAnalysis::Location(*CI), + AliasAnalysis::Location(Object))) + continue; + if (CS.doesNotAccessMemory(ArgNo)) + continue; + if (CS.onlyReadsMemory(ArgNo)) { + R = AliasAnalysis::Ref; + continue; + } + return AliasAnalysis::ModRef; + } + return R; } // AliasAnalysis destructor: DO NOT move this to the header file for @@ -270,7 +463,9 @@ AliasAnalysis::~AliasAnalysis() {} /// AliasAnalysis interface before any other methods are called. /// void AliasAnalysis::InitializeAliasAnalysis(Pass *P) { - TD = P->getAnalysisIfAvailable(); + DataLayoutPass *DLP = P->getAnalysisIfAvailable(); + DL = DLP ? &DLP->getDataLayout() : nullptr; + TLI = P->getAnalysisIfAvailable(); AA = &P->getAnalysis(); } @@ -280,11 +475,11 @@ void AliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { AU.addRequired(); // All AA's chain } -/// getTypeStoreSize - Return the TargetData store size for the given type, +/// getTypeStoreSize - Return the DataLayout store size for the given type, /// if known, or a conservative value otherwise. /// -uint64_t AliasAnalysis::getTypeStoreSize(const Type *Ty) { - return TD ? TD->getTypeStoreSize(Ty) : UnknownSize; +uint64_t AliasAnalysis::getTypeStoreSize(Type *Ty) { + return DL ? DL->getTypeStoreSize(Ty) : UnknownSize; } /// canBasicBlockModify - Return true if it is possible for execution of the @@ -324,6 +519,15 @@ bool llvm::isNoAliasCall(const Value *V) { return false; } +/// isNoAliasArgument - Return true if this is an argument with the noalias +/// attribute. +bool llvm::isNoAliasArgument(const Value *V) +{ + if (const Argument *A = dyn_cast(V)) + return A->hasNoAliasAttr(); + return false; +} + /// isIdentifiedObject - Return true if this pointer refers to a distinct and /// identifiable object. This returns true for: /// Global Variables and Functions (but not Global Aliases) @@ -342,3 +546,13 @@ bool llvm::isIdentifiedObject(const Value *V) { return A->hasNoAliasAttr() || A->hasByValAttr(); return false; } + +/// isIdentifiedFunctionLocal - Return true if V is umabigously identified +/// at the function-level. Different IdentifiedFunctionLocals can't alias. +/// Further, an IdentifiedFunctionLocal can not alias with any function +/// arguments other than itself, which is not necessarily true for +/// IdentifiedObjects. +bool llvm::isIdentifiedFunctionLocal(const Value *V) +{ + return isa(V) || isNoAliasCall(V) || isNoAliasArgument(V); +}