X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FAliasAnalysis.cpp;h=054930c0e1936c2ec64450dd89defbe6990b34e9;hb=55ec2218c448ef9e0d09b5534885b6d2a9786a73;hp=94a6d41872cf40adf8fb70be482144f177e37d12;hpb=6d8eb156e6be727570b300bac7712f745a318c7d;p=oota-llvm.git diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp index 94a6d41872c..054930c0e19 100644 --- a/lib/Analysis/AliasAnalysis.cpp +++ b/lib/Analysis/AliasAnalysis.cpp @@ -25,14 +25,18 @@ //===----------------------------------------------------------------------===// #include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/Analysis/CaptureTracking.h" +#include "llvm/Analysis/Dominators.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/BasicBlock.h" +#include "llvm/IR/DataLayout.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. @@ -65,6 +69,12 @@ 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) { @@ -80,14 +90,20 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS, if (onlyAccessesArgPointees(MRB)) { bool doesAlias = false; - if (doesAccessArgPointees(MRB)) + if (doesAccessArgPointees(MRB)) { + MDNode *CSTag = CS.getInstruction()->getMetadata(LLVMContext::MD_tbaa); for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end(); - AI != AE; ++AI) - if (!isNoAlias(Location(*AI), Loc)) { + AI != AE; ++AI) { + const Value *Arg = *AI; + if (!Arg->getType()->isPointerTy()) + continue; + Location CSLoc(Arg, UnknownSize, CSTag); + if (!isNoAlias(CSLoc, Loc)) { doesAlias = true; break; } - + } + } if (!doesAlias) return NoModRef; } @@ -132,13 +148,19 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) { // CS2's arguments. if (onlyAccessesArgPointees(CS2B)) { AliasAnalysis::ModRefResult R = NoModRef; - if (doesAccessArgPointees(CS2B)) + if (doesAccessArgPointees(CS2B)) { + MDNode *CS2Tag = CS2.getInstruction()->getMetadata(LLVMContext::MD_tbaa); for (ImmutableCallSite::arg_iterator I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) { - R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask); + const Value *Arg = *I; + if (!Arg->getType()->isPointerTy()) + continue; + Location CS2Loc(Arg, UnknownSize, CS2Tag); + R = ModRefResult((R | getModRefInfo(CS1, CS2Loc)) & Mask); if (R == Mask) break; } + } return R; } @@ -146,13 +168,20 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) { // any of the memory referenced by CS1's arguments. If not, return NoModRef. if (onlyAccessesArgPointees(CS1B)) { AliasAnalysis::ModRefResult R = NoModRef; - if (doesAccessArgPointees(CS1B)) + if (doesAccessArgPointees(CS1B)) { + MDNode *CS1Tag = CS1.getInstruction()->getMetadata(LLVMContext::MD_tbaa); for (ImmutableCallSite::arg_iterator - I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) - if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) { + I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) { + const Value *Arg = *I; + if (!Arg->getType()->isPointerTy()) + continue; + Location CS1Loc(Arg, UnknownSize, CS1Tag); + if (getModRefInfo(CS2, CS1Loc) != NoModRef) { R = Mask; break; } + } + } if (R == NoModRef) return R; } @@ -212,10 +241,52 @@ AliasAnalysis::Location AliasAnalysis::getLocation(const VAArgInst *VI) { VI->getMetadata(LLVMContext::MD_tbaa)); } +AliasAnalysis::Location +AliasAnalysis::getLocation(const AtomicCmpXchgInst *CXI) { + return Location(CXI->getPointerOperand(), + getTypeStoreSize(CXI->getCompareOperand()->getType()), + CXI->getMetadata(LLVMContext::MD_tbaa)); +} + +AliasAnalysis::Location +AliasAnalysis::getLocation(const AtomicRMWInst *RMWI) { + return Location(RMWI->getPointerOperand(), + getTypeStoreSize(RMWI->getValOperand()->getType()), + RMWI->getMetadata(LLVMContext::MD_tbaa)); +} + +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 TBAA tags. For memcpy, they apply + // to both the source and the destination. + MDNode *TBAATag = MTI->getMetadata(LLVMContext::MD_tbaa); + + return Location(MTI->getRawSource(), Size, TBAATag); +} + +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 TBAA tags. For memcpy, they apply + // to both the source and the destination. + MDNode *TBAATag = MTI->getMetadata(LLVMContext::MD_tbaa); + + return Location(MTI->getRawDest(), Size, TBAATag); +} + + + 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 @@ -229,8 +300,8 @@ 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 @@ -263,6 +334,150 @@ AliasAnalysis::getModRefInfo(const VAArgInst *V, const Location &Loc) { return ModRef; } +AliasAnalysis::ModRefResult +AliasAnalysis::getModRefInfo(const AtomicCmpXchgInst *CX, const Location &Loc) { + // Acquire/Release cmpxchg has properties that matter for arbitrary addresses. + if (CX->getOrdering() > 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; +} + +namespace { + // Conservatively return true. Return false, if there is a single path + // starting from "From" and the path does not reach "To". + static bool hasPath(const BasicBlock *From, const BasicBlock *To) { + const unsigned MaxCheck = 5; + const BasicBlock *Current = From; + for (unsigned I = 0; I < MaxCheck; I++) { + unsigned NumSuccs = Current->getTerminator()->getNumSuccessors(); + if (NumSuccs > 1) + return true; + if (NumSuccs == 0) + return false; + Current = Current->getTerminator()->getSuccessor(0); + if (Current == To) + return true; + } + return true; + } + + /// Only find pointer captures which happen before the given instruction. Uses + /// the dominator tree to determine whether one instruction is before another. + /// Only support the case where the Value is defined in the same basic block + /// as the given instruction and the use. + struct CapturesBefore : public CaptureTracker { + CapturesBefore(const Instruction *I, DominatorTree *DT) + : BeforeHere(I), DT(DT), Captured(false) {} + + void tooManyUses() { Captured = true; } + + bool shouldExplore(Use *U) { + Instruction *I = cast(U->getUser()); + BasicBlock *BB = I->getParent(); + // We explore this usage only if the usage can reach "BeforeHere". + // If use is not reachable from entry, there is no need to explore. + if (BeforeHere != I && !DT->isReachableFromEntry(BB)) + return false; + // If the value is defined in the same basic block as use and BeforeHere, + // there is no need to explore the use if BeforeHere dominates use. + // Check whether there is a path from I to BeforeHere. + if (BeforeHere != I && DT->dominates(BeforeHere, I) && + !hasPath(BB, BeforeHere->getParent())) + return false; + return true; + } + + bool captured(Use *U) { + Instruction *I = cast(U->getUser()); + BasicBlock *BB = I->getParent(); + // Same logic as in shouldExplore. + if (BeforeHere != I && !DT->isReachableFromEntry(BB)) + return false; + if (BeforeHere != I && DT->dominates(BeforeHere, I) && + !hasPath(BB, BeforeHere->getParent())) + return false; + Captured = true; + return true; + } + + const Instruction *BeforeHere; + DominatorTree *DT; + + bool Captured; + }; +} + +// 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 || !TD) return AliasAnalysis::ModRef; + + const Value *Object = GetUnderlyingObject(MemLoc.Ptr, TD); + if (!isIdentifiedObject(Object) || isa(Object) || + isa(Object)) + return AliasAnalysis::ModRef; + + ImmutableCallSite CS(I); + if (!CS.getInstruction() || CS.getInstruction() == Object) + return AliasAnalysis::ModRef; + + CapturesBefore CB(I, DT); + llvm::PointerMayBeCaptured(Object, &CB); + if (CB.Captured) + 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 // AliasAnalysis or else clients of the AliasAnalysis class may not depend on // the AliasAnalysis.o file in the current .a file, causing alias analysis @@ -274,7 +489,8 @@ AliasAnalysis::~AliasAnalysis() {} /// AliasAnalysis interface before any other methods are called. /// void AliasAnalysis::InitializeAliasAnalysis(Pass *P) { - TD = P->getAnalysisIfAvailable(); + TD = P->getAnalysisIfAvailable(); + TLI = P->getAnalysisIfAvailable(); AA = &P->getAnalysis(); } @@ -284,10 +500,10 @@ 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) { +uint64_t AliasAnalysis::getTypeStoreSize(Type *Ty) { return TD ? TD->getTypeStoreSize(Ty) : UnknownSize; } @@ -328,6 +544,15 @@ 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)