| //===- MemoryDependenceAnalysis.cpp - Mem Deps Implementation --*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements an analysis that determines, for a given memory |
| // operation, what preceding memory operations it depends on. It builds on |
| // alias analysis information, and tries to provide a lazy, caching interface to |
| // a common kind of alias information query. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "memdep" |
| #include "llvm/Analysis/MemoryDependenceAnalysis.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/MemoryBuiltins.h" |
| #include "llvm/Analysis/PHITransAddr.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/DataLayout.h" |
| #include "llvm/Function.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/LLVMContext.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/PredIteratorCache.h" |
| using namespace llvm; |
| |
| STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses"); |
| STATISTIC(NumCacheDirtyNonLocal, "Number of dirty cached non-local responses"); |
| STATISTIC(NumUncacheNonLocal, "Number of uncached non-local responses"); |
| |
| STATISTIC(NumCacheNonLocalPtr, |
| "Number of fully cached non-local ptr responses"); |
| STATISTIC(NumCacheDirtyNonLocalPtr, |
| "Number of cached, but dirty, non-local ptr responses"); |
| STATISTIC(NumUncacheNonLocalPtr, |
| "Number of uncached non-local ptr responses"); |
| STATISTIC(NumCacheCompleteNonLocalPtr, |
| "Number of block queries that were completely cached"); |
| |
| // Limit for the number of instructions to scan in a block. |
| // FIXME: Figure out what a sane value is for this. |
| // (500 is relatively insane.) |
| static const int BlockScanLimit = 500; |
| |
| char MemoryDependenceAnalysis::ID = 0; |
| |
| // Register this pass... |
| INITIALIZE_PASS_BEGIN(MemoryDependenceAnalysis, "memdep", |
| "Memory Dependence Analysis", false, true) |
| INITIALIZE_AG_DEPENDENCY(AliasAnalysis) |
| INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep", |
| "Memory Dependence Analysis", false, true) |
| |
| MemoryDependenceAnalysis::MemoryDependenceAnalysis() |
| : FunctionPass(ID), PredCache(0) { |
| initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry()); |
| } |
| MemoryDependenceAnalysis::~MemoryDependenceAnalysis() { |
| } |
| |
| /// Clean up memory in between runs |
| void MemoryDependenceAnalysis::releaseMemory() { |
| LocalDeps.clear(); |
| NonLocalDeps.clear(); |
| NonLocalPointerDeps.clear(); |
| ReverseLocalDeps.clear(); |
| ReverseNonLocalDeps.clear(); |
| ReverseNonLocalPtrDeps.clear(); |
| PredCache->clear(); |
| } |
| |
| |
| |
| /// getAnalysisUsage - Does not modify anything. It uses Alias Analysis. |
| /// |
| void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesAll(); |
| AU.addRequiredTransitive<AliasAnalysis>(); |
| } |
| |
| bool MemoryDependenceAnalysis::runOnFunction(Function &) { |
| AA = &getAnalysis<AliasAnalysis>(); |
| TD = getAnalysisIfAvailable<DataLayout>(); |
| DT = getAnalysisIfAvailable<DominatorTree>(); |
| if (PredCache == 0) |
| PredCache.reset(new PredIteratorCache()); |
| return false; |
| } |
| |
| /// RemoveFromReverseMap - This is a helper function that removes Val from |
| /// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry. |
| template <typename KeyTy> |
| static void RemoveFromReverseMap(DenseMap<Instruction*, |
| SmallPtrSet<KeyTy, 4> > &ReverseMap, |
| Instruction *Inst, KeyTy Val) { |
| typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator |
| InstIt = ReverseMap.find(Inst); |
| assert(InstIt != ReverseMap.end() && "Reverse map out of sync?"); |
| bool Found = InstIt->second.erase(Val); |
| assert(Found && "Invalid reverse map!"); (void)Found; |
| if (InstIt->second.empty()) |
| ReverseMap.erase(InstIt); |
| } |
| |
| /// GetLocation - If the given instruction references a specific memory |
| /// location, fill in Loc with the details, otherwise set Loc.Ptr to null. |
| /// Return a ModRefInfo value describing the general behavior of the |
| /// instruction. |
| static |
| AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst, |
| AliasAnalysis::Location &Loc, |
| AliasAnalysis *AA) { |
| if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) { |
| if (LI->isUnordered()) { |
| Loc = AA->getLocation(LI); |
| return AliasAnalysis::Ref; |
| } else if (LI->getOrdering() == Monotonic) { |
| Loc = AA->getLocation(LI); |
| return AliasAnalysis::ModRef; |
| } |
| Loc = AliasAnalysis::Location(); |
| return AliasAnalysis::ModRef; |
| } |
| |
| if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { |
| if (SI->isUnordered()) { |
| Loc = AA->getLocation(SI); |
| return AliasAnalysis::Mod; |
| } else if (SI->getOrdering() == Monotonic) { |
| Loc = AA->getLocation(SI); |
| return AliasAnalysis::ModRef; |
| } |
| Loc = AliasAnalysis::Location(); |
| return AliasAnalysis::ModRef; |
| } |
| |
| if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) { |
| Loc = AA->getLocation(V); |
| return AliasAnalysis::ModRef; |
| } |
| |
| if (const CallInst *CI = isFreeCall(Inst, AA->getTargetLibraryInfo())) { |
| // calls to free() deallocate the entire structure |
| Loc = AliasAnalysis::Location(CI->getArgOperand(0)); |
| return AliasAnalysis::Mod; |
| } |
| |
| if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) |
| switch (II->getIntrinsicID()) { |
| case Intrinsic::lifetime_start: |
| case Intrinsic::lifetime_end: |
| case Intrinsic::invariant_start: |
| Loc = AliasAnalysis::Location(II->getArgOperand(1), |
| cast<ConstantInt>(II->getArgOperand(0)) |
| ->getZExtValue(), |
| II->getMetadata(LLVMContext::MD_tbaa)); |
| // These intrinsics don't really modify the memory, but returning Mod |
| // will allow them to be handled conservatively. |
| return AliasAnalysis::Mod; |
| case Intrinsic::invariant_end: |
| Loc = AliasAnalysis::Location(II->getArgOperand(2), |
| cast<ConstantInt>(II->getArgOperand(1)) |
| ->getZExtValue(), |
| II->getMetadata(LLVMContext::MD_tbaa)); |
| // These intrinsics don't really modify the memory, but returning Mod |
| // will allow them to be handled conservatively. |
| return AliasAnalysis::Mod; |
| default: |
| break; |
| } |
| |
| // Otherwise, just do the coarse-grained thing that always works. |
| if (Inst->mayWriteToMemory()) |
| return AliasAnalysis::ModRef; |
| if (Inst->mayReadFromMemory()) |
| return AliasAnalysis::Ref; |
| return AliasAnalysis::NoModRef; |
| } |
| |
| /// getCallSiteDependencyFrom - Private helper for finding the local |
| /// dependencies of a call site. |
| MemDepResult MemoryDependenceAnalysis:: |
| getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall, |
| BasicBlock::iterator ScanIt, BasicBlock *BB) { |
| unsigned Limit = BlockScanLimit; |
| |
| // Walk backwards through the block, looking for dependencies |
| while (ScanIt != BB->begin()) { |
| // Limit the amount of scanning we do so we don't end up with quadratic |
| // running time on extreme testcases. |
| --Limit; |
| if (!Limit) |
| return MemDepResult::getUnknown(); |
| |
| Instruction *Inst = --ScanIt; |
| |
| // If this inst is a memory op, get the pointer it accessed |
| AliasAnalysis::Location Loc; |
| AliasAnalysis::ModRefResult MR = GetLocation(Inst, Loc, AA); |
| if (Loc.Ptr) { |
| // A simple instruction. |
| if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef) |
| return MemDepResult::getClobber(Inst); |
| continue; |
| } |
| |
| if (CallSite InstCS = cast<Value>(Inst)) { |
| // Debug intrinsics don't cause dependences. |
| if (isa<DbgInfoIntrinsic>(Inst)) continue; |
| // If these two calls do not interfere, look past it. |
| switch (AA->getModRefInfo(CS, InstCS)) { |
| case AliasAnalysis::NoModRef: |
| // If the two calls are the same, return InstCS as a Def, so that |
| // CS can be found redundant and eliminated. |
| if (isReadOnlyCall && !(MR & AliasAnalysis::Mod) && |
| CS.getInstruction()->isIdenticalToWhenDefined(Inst)) |
| return MemDepResult::getDef(Inst); |
| |
| // Otherwise if the two calls don't interact (e.g. InstCS is readnone) |
| // keep scanning. |
| continue; |
| default: |
| return MemDepResult::getClobber(Inst); |
| } |
| } |
| |
| // If we could not obtain a pointer for the instruction and the instruction |
| // touches memory then assume that this is a dependency. |
| if (MR != AliasAnalysis::NoModRef) |
| return MemDepResult::getClobber(Inst); |
| } |
| |
| // No dependence found. If this is the entry block of the function, it is |
| // unknown, otherwise it is non-local. |
| if (BB != &BB->getParent()->getEntryBlock()) |
| return MemDepResult::getNonLocal(); |
| return MemDepResult::getNonFuncLocal(); |
| } |
| |
| /// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that |
| /// would fully overlap MemLoc if done as a wider legal integer load. |
| /// |
| /// MemLocBase, MemLocOffset are lazily computed here the first time the |
| /// base/offs of memloc is needed. |
| static bool |
| isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc, |
| const Value *&MemLocBase, |
| int64_t &MemLocOffs, |
| const LoadInst *LI, |
| const DataLayout *TD) { |
| // If we have no target data, we can't do this. |
| if (TD == 0) return false; |
| |
| // If we haven't already computed the base/offset of MemLoc, do so now. |
| if (MemLocBase == 0) |
| MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, *TD); |
| |
| unsigned Size = MemoryDependenceAnalysis:: |
| getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size, |
| LI, *TD); |
| return Size != 0; |
| } |
| |
| /// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that |
| /// looks at a memory location for a load (specified by MemLocBase, Offs, |
| /// and Size) and compares it against a load. If the specified load could |
| /// be safely widened to a larger integer load that is 1) still efficient, |
| /// 2) safe for the target, and 3) would provide the specified memory |
| /// location value, then this function returns the size in bytes of the |
| /// load width to use. If not, this returns zero. |
| unsigned MemoryDependenceAnalysis:: |
| getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs, |
| unsigned MemLocSize, const LoadInst *LI, |
| const DataLayout &TD) { |
| // We can only extend simple integer loads. |
| if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0; |
| |
| // Get the base of this load. |
| int64_t LIOffs = 0; |
| const Value *LIBase = |
| GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, TD); |
| |
| // If the two pointers are not based on the same pointer, we can't tell that |
| // they are related. |
| if (LIBase != MemLocBase) return 0; |
| |
| // Okay, the two values are based on the same pointer, but returned as |
| // no-alias. This happens when we have things like two byte loads at "P+1" |
| // and "P+3". Check to see if increasing the size of the "LI" load up to its |
| // alignment (or the largest native integer type) will allow us to load all |
| // the bits required by MemLoc. |
| |
| // If MemLoc is before LI, then no widening of LI will help us out. |
| if (MemLocOffs < LIOffs) return 0; |
| |
| // Get the alignment of the load in bytes. We assume that it is safe to load |
| // any legal integer up to this size without a problem. For example, if we're |
| // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can |
| // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it |
| // to i16. |
| unsigned LoadAlign = LI->getAlignment(); |
| |
| int64_t MemLocEnd = MemLocOffs+MemLocSize; |
| |
| // If no amount of rounding up will let MemLoc fit into LI, then bail out. |
| if (LIOffs+LoadAlign < MemLocEnd) return 0; |
| |
| // This is the size of the load to try. Start with the next larger power of |
| // two. |
| unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U; |
| NewLoadByteSize = NextPowerOf2(NewLoadByteSize); |
| |
| while (1) { |
| // If this load size is bigger than our known alignment or would not fit |
| // into a native integer register, then we fail. |
| if (NewLoadByteSize > LoadAlign || |
| !TD.fitsInLegalInteger(NewLoadByteSize*8)) |
| return 0; |
| |
| if (LIOffs+NewLoadByteSize > MemLocEnd && |
| LI->getParent()->getParent()->getAttributes(). |
| hasAttribute(AttributeSet::FunctionIndex, Attribute::AddressSafety)) |
| // We will be reading past the location accessed by the original program. |
| // While this is safe in a regular build, Address Safety analysis tools |
| // may start reporting false warnings. So, don't do widening. |
| return 0; |
| |
| // If a load of this width would include all of MemLoc, then we succeed. |
| if (LIOffs+NewLoadByteSize >= MemLocEnd) |
| return NewLoadByteSize; |
| |
| NewLoadByteSize <<= 1; |
| } |
| } |
| |
| /// getPointerDependencyFrom - Return the instruction on which a memory |
| /// location depends. If isLoad is true, this routine ignores may-aliases with |
| /// read-only operations. If isLoad is false, this routine ignores may-aliases |
| /// with reads from read-only locations. |
| MemDepResult MemoryDependenceAnalysis:: |
| getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad, |
| BasicBlock::iterator ScanIt, BasicBlock *BB) { |
| |
| const Value *MemLocBase = 0; |
| int64_t MemLocOffset = 0; |
| |
| unsigned Limit = BlockScanLimit; |
| |
| // Walk backwards through the basic block, looking for dependencies. |
| while (ScanIt != BB->begin()) { |
| // Limit the amount of scanning we do so we don't end up with quadratic |
| // running time on extreme testcases. |
| --Limit; |
| if (!Limit) |
| return MemDepResult::getUnknown(); |
| |
| Instruction *Inst = --ScanIt; |
| |
| if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { |
| // Debug intrinsics don't (and can't) cause dependences. |
| if (isa<DbgInfoIntrinsic>(II)) continue; |
| |
| // If we reach a lifetime begin or end marker, then the query ends here |
| // because the value is undefined. |
| if (II->getIntrinsicID() == Intrinsic::lifetime_start) { |
| // FIXME: This only considers queries directly on the invariant-tagged |
| // pointer, not on query pointers that are indexed off of them. It'd |
| // be nice to handle that at some point (the right approach is to use |
| // GetPointerBaseWithConstantOffset). |
| if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)), |
| MemLoc)) |
| return MemDepResult::getDef(II); |
| continue; |
| } |
| } |
| |
| // Values depend on loads if the pointers are must aliased. This means that |
| // a load depends on another must aliased load from the same value. |
| if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) { |
| // Atomic loads have complications involved. |
| // FIXME: This is overly conservative. |
| if (!LI->isUnordered()) |
| return MemDepResult::getClobber(LI); |
| |
| AliasAnalysis::Location LoadLoc = AA->getLocation(LI); |
| |
| // If we found a pointer, check if it could be the same as our pointer. |
| AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc); |
| |
| if (isLoad) { |
| if (R == AliasAnalysis::NoAlias) { |
| // If this is an over-aligned integer load (for example, |
| // "load i8* %P, align 4") see if it would obviously overlap with the |
| // queried location if widened to a larger load (e.g. if the queried |
| // location is 1 byte at P+1). If so, return it as a load/load |
| // clobber result, allowing the client to decide to widen the load if |
| // it wants to. |
| if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) |
| if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() && |
| isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase, |
| MemLocOffset, LI, TD)) |
| return MemDepResult::getClobber(Inst); |
| |
| continue; |
| } |
| |
| // Must aliased loads are defs of each other. |
| if (R == AliasAnalysis::MustAlias) |
| return MemDepResult::getDef(Inst); |
| |
| #if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads |
| // in terms of clobbering loads, but since it does this by looking |
| // at the clobbering load directly, it doesn't know about any |
| // phi translation that may have happened along the way. |
| |
| // If we have a partial alias, then return this as a clobber for the |
| // client to handle. |
| if (R == AliasAnalysis::PartialAlias) |
| return MemDepResult::getClobber(Inst); |
| #endif |
| |
| // Random may-alias loads don't depend on each other without a |
| // dependence. |
| continue; |
| } |
| |
| // Stores don't depend on other no-aliased accesses. |
| if (R == AliasAnalysis::NoAlias) |
| continue; |
| |
| // Stores don't alias loads from read-only memory. |
| if (AA->pointsToConstantMemory(LoadLoc)) |
| continue; |
| |
| // Stores depend on may/must aliased loads. |
| return MemDepResult::getDef(Inst); |
| } |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { |
| // Atomic stores have complications involved. |
| // FIXME: This is overly conservative. |
| if (!SI->isUnordered()) |
| return MemDepResult::getClobber(SI); |
| |
| // If alias analysis can tell that this store is guaranteed to not modify |
| // the query pointer, ignore it. Use getModRefInfo to handle cases where |
| // the query pointer points to constant memory etc. |
| if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef) |
| continue; |
| |
| // Ok, this store might clobber the query pointer. Check to see if it is |
| // a must alias: in this case, we want to return this as a def. |
| AliasAnalysis::Location StoreLoc = AA->getLocation(SI); |
| |
| // If we found a pointer, check if it could be the same as our pointer. |
| AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc); |
| |
| if (R == AliasAnalysis::NoAlias) |
| continue; |
| if (R == AliasAnalysis::MustAlias) |
| return MemDepResult::getDef(Inst); |
| return MemDepResult::getClobber(Inst); |
| } |
| |
| // If this is an allocation, and if we know that the accessed pointer is to |
| // the allocation, return Def. This means that there is no dependence and |
| // the access can be optimized based on that. For example, a load could |
| // turn into undef. |
| // Note: Only determine this to be a malloc if Inst is the malloc call, not |
| // a subsequent bitcast of the malloc call result. There can be stores to |
| // the malloced memory between the malloc call and its bitcast uses, and we |
| // need to continue scanning until the malloc call. |
| const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo(); |
| if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) { |
| const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD); |
| |
| if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr)) |
| return MemDepResult::getDef(Inst); |
| // Be conservative if the accessed pointer may alias the allocation. |
| if (AA->alias(Inst, AccessPtr) != AliasAnalysis::NoAlias) |
| return MemDepResult::getClobber(Inst); |
| // If the allocation is not aliased and does not read memory (like |
| // strdup), it is safe to ignore. |
| if (isa<AllocaInst>(Inst) || |
| isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI)) |
| continue; |
| } |
| |
| // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer. |
| AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc); |
| // If necessary, perform additional analysis. |
| if (MR == AliasAnalysis::ModRef) |
| MR = AA->callCapturesBefore(Inst, MemLoc, DT); |
| switch (MR) { |
| case AliasAnalysis::NoModRef: |
| // If the call has no effect on the queried pointer, just ignore it. |
| continue; |
| case AliasAnalysis::Mod: |
| return MemDepResult::getClobber(Inst); |
| case AliasAnalysis::Ref: |
| // If the call is known to never store to the pointer, and if this is a |
| // load query, we can safely ignore it (scan past it). |
| if (isLoad) |
| continue; |
| default: |
| // Otherwise, there is a potential dependence. Return a clobber. |
| return MemDepResult::getClobber(Inst); |
| } |
| } |
| |
| // No dependence found. If this is the entry block of the function, it is |
| // unknown, otherwise it is non-local. |
| if (BB != &BB->getParent()->getEntryBlock()) |
| return MemDepResult::getNonLocal(); |
| return MemDepResult::getNonFuncLocal(); |
| } |
| |
| /// getDependency - Return the instruction on which a memory operation |
| /// depends. |
| MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) { |
| Instruction *ScanPos = QueryInst; |
| |
| // Check for a cached result |
| MemDepResult &LocalCache = LocalDeps[QueryInst]; |
| |
| // If the cached entry is non-dirty, just return it. Note that this depends |
| // on MemDepResult's default constructing to 'dirty'. |
| if (!LocalCache.isDirty()) |
| return LocalCache; |
| |
| // Otherwise, if we have a dirty entry, we know we can start the scan at that |
| // instruction, which may save us some work. |
| if (Instruction *Inst = LocalCache.getInst()) { |
| ScanPos = Inst; |
| |
| RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst); |
| } |
| |
| BasicBlock *QueryParent = QueryInst->getParent(); |
| |
| // Do the scan. |
| if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) { |
| // No dependence found. If this is the entry block of the function, it is |
| // unknown, otherwise it is non-local. |
| if (QueryParent != &QueryParent->getParent()->getEntryBlock()) |
| LocalCache = MemDepResult::getNonLocal(); |
| else |
| LocalCache = MemDepResult::getNonFuncLocal(); |
| } else { |
| AliasAnalysis::Location MemLoc; |
| AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA); |
| if (MemLoc.Ptr) { |
| // If we can do a pointer scan, make it happen. |
| bool isLoad = !(MR & AliasAnalysis::Mod); |
| if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst)) |
| isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start; |
| |
| LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos, |
| QueryParent); |
| } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) { |
| CallSite QueryCS(QueryInst); |
| bool isReadOnly = AA->onlyReadsMemory(QueryCS); |
| LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos, |
| QueryParent); |
| } else |
| // Non-memory instruction. |
| LocalCache = MemDepResult::getUnknown(); |
| } |
| |
| // Remember the result! |
| if (Instruction *I = LocalCache.getInst()) |
| ReverseLocalDeps[I].insert(QueryInst); |
| |
| return LocalCache; |
| } |
| |
| #ifndef NDEBUG |
| /// AssertSorted - This method is used when -debug is specified to verify that |
| /// cache arrays are properly kept sorted. |
| static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache, |
| int Count = -1) { |
| if (Count == -1) Count = Cache.size(); |
| if (Count == 0) return; |
| |
| for (unsigned i = 1; i != unsigned(Count); ++i) |
| assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!"); |
| } |
| #endif |
| |
| /// getNonLocalCallDependency - Perform a full dependency query for the |
| /// specified call, returning the set of blocks that the value is |
| /// potentially live across. The returned set of results will include a |
| /// "NonLocal" result for all blocks where the value is live across. |
| /// |
| /// This method assumes the instruction returns a "NonLocal" dependency |
| /// within its own block. |
| /// |
| /// This returns a reference to an internal data structure that may be |
| /// invalidated on the next non-local query or when an instruction is |
| /// removed. Clients must copy this data if they want it around longer than |
| /// that. |
| const MemoryDependenceAnalysis::NonLocalDepInfo & |
| MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) { |
| assert(getDependency(QueryCS.getInstruction()).isNonLocal() && |
| "getNonLocalCallDependency should only be used on calls with non-local deps!"); |
| PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()]; |
| NonLocalDepInfo &Cache = CacheP.first; |
| |
| /// DirtyBlocks - This is the set of blocks that need to be recomputed. In |
| /// the cached case, this can happen due to instructions being deleted etc. In |
| /// the uncached case, this starts out as the set of predecessors we care |
| /// about. |
| SmallVector<BasicBlock*, 32> DirtyBlocks; |
| |
| if (!Cache.empty()) { |
| // Okay, we have a cache entry. If we know it is not dirty, just return it |
| // with no computation. |
| if (!CacheP.second) { |
| ++NumCacheNonLocal; |
| return Cache; |
| } |
| |
| // If we already have a partially computed set of results, scan them to |
| // determine what is dirty, seeding our initial DirtyBlocks worklist. |
| for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end(); |
| I != E; ++I) |
| if (I->getResult().isDirty()) |
| DirtyBlocks.push_back(I->getBB()); |
| |
| // Sort the cache so that we can do fast binary search lookups below. |
| std::sort(Cache.begin(), Cache.end()); |
| |
| ++NumCacheDirtyNonLocal; |
| //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: " |
| // << Cache.size() << " cached: " << *QueryInst; |
| } else { |
| // Seed DirtyBlocks with each of the preds of QueryInst's block. |
| BasicBlock *QueryBB = QueryCS.getInstruction()->getParent(); |
| for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI) |
| DirtyBlocks.push_back(*PI); |
| ++NumUncacheNonLocal; |
| } |
| |
| // isReadonlyCall - If this is a read-only call, we can be more aggressive. |
| bool isReadonlyCall = AA->onlyReadsMemory(QueryCS); |
| |
| SmallPtrSet<BasicBlock*, 64> Visited; |
| |
| unsigned NumSortedEntries = Cache.size(); |
| DEBUG(AssertSorted(Cache)); |
| |
| // Iterate while we still have blocks to update. |
| while (!DirtyBlocks.empty()) { |
| BasicBlock *DirtyBB = DirtyBlocks.back(); |
| DirtyBlocks.pop_back(); |
| |
| // Already processed this block? |
| if (!Visited.insert(DirtyBB)) |
| continue; |
| |
| // Do a binary search to see if we already have an entry for this block in |
| // the cache set. If so, find it. |
| DEBUG(AssertSorted(Cache, NumSortedEntries)); |
| NonLocalDepInfo::iterator Entry = |
| std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries, |
| NonLocalDepEntry(DirtyBB)); |
| if (Entry != Cache.begin() && prior(Entry)->getBB() == DirtyBB) |
| --Entry; |
| |
| NonLocalDepEntry *ExistingResult = 0; |
| if (Entry != Cache.begin()+NumSortedEntries && |
| Entry->getBB() == DirtyBB) { |
| // If we already have an entry, and if it isn't already dirty, the block |
| // is done. |
| if (!Entry->getResult().isDirty()) |
| continue; |
| |
| // Otherwise, remember this slot so we can update the value. |
| ExistingResult = &*Entry; |
| } |
| |
| // If the dirty entry has a pointer, start scanning from it so we don't have |
| // to rescan the entire block. |
| BasicBlock::iterator ScanPos = DirtyBB->end(); |
| if (ExistingResult) { |
| if (Instruction *Inst = ExistingResult->getResult().getInst()) { |
| ScanPos = Inst; |
| // We're removing QueryInst's use of Inst. |
| RemoveFromReverseMap(ReverseNonLocalDeps, Inst, |
| QueryCS.getInstruction()); |
| } |
| } |
| |
| // Find out if this block has a local dependency for QueryInst. |
| MemDepResult Dep; |
| |
| if (ScanPos != DirtyBB->begin()) { |
| Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB); |
| } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) { |
| // No dependence found. If this is the entry block of the function, it is |
| // a clobber, otherwise it is unknown. |
| Dep = MemDepResult::getNonLocal(); |
| } else { |
| Dep = MemDepResult::getNonFuncLocal(); |
| } |
| |
| // If we had a dirty entry for the block, update it. Otherwise, just add |
| // a new entry. |
| if (ExistingResult) |
| ExistingResult->setResult(Dep); |
| else |
| Cache.push_back(NonLocalDepEntry(DirtyBB, Dep)); |
| |
| // If the block has a dependency (i.e. it isn't completely transparent to |
| // the value), remember the association! |
| if (!Dep.isNonLocal()) { |
| // Keep the ReverseNonLocalDeps map up to date so we can efficiently |
| // update this when we remove instructions. |
| if (Instruction *Inst = Dep.getInst()) |
| ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction()); |
| } else { |
| |
| // If the block *is* completely transparent to the load, we need to check |
| // the predecessors of this block. Add them to our worklist. |
| for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI) |
| DirtyBlocks.push_back(*PI); |
| } |
| } |
| |
| return Cache; |
| } |
| |
| /// getNonLocalPointerDependency - Perform a full dependency query for an |
| /// access to the specified (non-volatile) memory location, returning the |
| /// set of instructions that either define or clobber the value. |
| /// |
| /// This method assumes the pointer has a "NonLocal" dependency within its |
| /// own block. |
| /// |
| void MemoryDependenceAnalysis:: |
| getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad, |
| BasicBlock *FromBB, |
| SmallVectorImpl<NonLocalDepResult> &Result) { |
| assert(Loc.Ptr->getType()->isPointerTy() && |
| "Can't get pointer deps of a non-pointer!"); |
| Result.clear(); |
| |
| PHITransAddr Address(const_cast<Value *>(Loc.Ptr), TD); |
| |
| // This is the set of blocks we've inspected, and the pointer we consider in |
| // each block. Because of critical edges, we currently bail out if querying |
| // a block with multiple different pointers. This can happen during PHI |
| // translation. |
| DenseMap<BasicBlock*, Value*> Visited; |
| if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB, |
| Result, Visited, true)) |
| return; |
| Result.clear(); |
| Result.push_back(NonLocalDepResult(FromBB, |
| MemDepResult::getUnknown(), |
| const_cast<Value *>(Loc.Ptr))); |
| } |
| |
| /// GetNonLocalInfoForBlock - Compute the memdep value for BB with |
| /// Pointer/PointeeSize using either cached information in Cache or by doing a |
| /// lookup (which may use dirty cache info if available). If we do a lookup, |
| /// add the result to the cache. |
| MemDepResult MemoryDependenceAnalysis:: |
| GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc, |
| bool isLoad, BasicBlock *BB, |
| NonLocalDepInfo *Cache, unsigned NumSortedEntries) { |
| |
| // Do a binary search to see if we already have an entry for this block in |
| // the cache set. If so, find it. |
| NonLocalDepInfo::iterator Entry = |
| std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries, |
| NonLocalDepEntry(BB)); |
| if (Entry != Cache->begin() && (Entry-1)->getBB() == BB) |
| --Entry; |
| |
| NonLocalDepEntry *ExistingResult = 0; |
| if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB) |
| ExistingResult = &*Entry; |
| |
| // If we have a cached entry, and it is non-dirty, use it as the value for |
| // this dependency. |
| if (ExistingResult && !ExistingResult->getResult().isDirty()) { |
| ++NumCacheNonLocalPtr; |
| return ExistingResult->getResult(); |
| } |
| |
| // Otherwise, we have to scan for the value. If we have a dirty cache |
| // entry, start scanning from its position, otherwise we scan from the end |
| // of the block. |
| BasicBlock::iterator ScanPos = BB->end(); |
| if (ExistingResult && ExistingResult->getResult().getInst()) { |
| assert(ExistingResult->getResult().getInst()->getParent() == BB && |
| "Instruction invalidated?"); |
| ++NumCacheDirtyNonLocalPtr; |
| ScanPos = ExistingResult->getResult().getInst(); |
| |
| // Eliminating the dirty entry from 'Cache', so update the reverse info. |
| ValueIsLoadPair CacheKey(Loc.Ptr, isLoad); |
| RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey); |
| } else { |
| ++NumUncacheNonLocalPtr; |
| } |
| |
| // Scan the block for the dependency. |
| MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB); |
| |
| // If we had a dirty entry for the block, update it. Otherwise, just add |
| // a new entry. |
| if (ExistingResult) |
| ExistingResult->setResult(Dep); |
| else |
| Cache->push_back(NonLocalDepEntry(BB, Dep)); |
| |
| // If the block has a dependency (i.e. it isn't completely transparent to |
| // the value), remember the reverse association because we just added it |
| // to Cache! |
| if (!Dep.isDef() && !Dep.isClobber()) |
| return Dep; |
| |
| // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently |
| // update MemDep when we remove instructions. |
| Instruction *Inst = Dep.getInst(); |
| assert(Inst && "Didn't depend on anything?"); |
| ValueIsLoadPair CacheKey(Loc.Ptr, isLoad); |
| ReverseNonLocalPtrDeps[Inst].insert(CacheKey); |
| return Dep; |
| } |
| |
| /// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain |
| /// number of elements in the array that are already properly ordered. This is |
| /// optimized for the case when only a few entries are added. |
| static void |
| SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache, |
| unsigned NumSortedEntries) { |
| switch (Cache.size() - NumSortedEntries) { |
| case 0: |
| // done, no new entries. |
| break; |
| case 2: { |
| // Two new entries, insert the last one into place. |
| NonLocalDepEntry Val = Cache.back(); |
| Cache.pop_back(); |
| MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry = |
| std::upper_bound(Cache.begin(), Cache.end()-1, Val); |
| Cache.insert(Entry, Val); |
| // FALL THROUGH. |
| } |
| case 1: |
| // One new entry, Just insert the new value at the appropriate position. |
| if (Cache.size() != 1) { |
| NonLocalDepEntry Val = Cache.back(); |
| Cache.pop_back(); |
| MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry = |
| std::upper_bound(Cache.begin(), Cache.end(), Val); |
| Cache.insert(Entry, Val); |
| } |
| break; |
| default: |
| // Added many values, do a full scale sort. |
| std::sort(Cache.begin(), Cache.end()); |
| break; |
| } |
| } |
| |
| /// getNonLocalPointerDepFromBB - Perform a dependency query based on |
| /// pointer/pointeesize starting at the end of StartBB. Add any clobber/def |
| /// results to the results vector and keep track of which blocks are visited in |
| /// 'Visited'. |
| /// |
| /// This has special behavior for the first block queries (when SkipFirstBlock |
| /// is true). In this special case, it ignores the contents of the specified |
| /// block and starts returning dependence info for its predecessors. |
| /// |
| /// This function returns false on success, or true to indicate that it could |
| /// not compute dependence information for some reason. This should be treated |
| /// as a clobber dependence on the first instruction in the predecessor block. |
| bool MemoryDependenceAnalysis:: |
| getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, |
| const AliasAnalysis::Location &Loc, |
| bool isLoad, BasicBlock *StartBB, |
| SmallVectorImpl<NonLocalDepResult> &Result, |
| DenseMap<BasicBlock*, Value*> &Visited, |
| bool SkipFirstBlock) { |
| |
| // Look up the cached info for Pointer. |
| ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad); |
| |
| // Set up a temporary NLPI value. If the map doesn't yet have an entry for |
| // CacheKey, this value will be inserted as the associated value. Otherwise, |
| // it'll be ignored, and we'll have to check to see if the cached size and |
| // tbaa tag are consistent with the current query. |
| NonLocalPointerInfo InitialNLPI; |
| InitialNLPI.Size = Loc.Size; |
| InitialNLPI.TBAATag = Loc.TBAATag; |
| |
| // Get the NLPI for CacheKey, inserting one into the map if it doesn't |
| // already have one. |
| std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair = |
| NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI)); |
| NonLocalPointerInfo *CacheInfo = &Pair.first->second; |
| |
| // If we already have a cache entry for this CacheKey, we may need to do some |
| // work to reconcile the cache entry and the current query. |
| if (!Pair.second) { |
| if (CacheInfo->Size < Loc.Size) { |
| // The query's Size is greater than the cached one. Throw out the |
| // cached data and proceed with the query at the greater size. |
| CacheInfo->Pair = BBSkipFirstBlockPair(); |
| CacheInfo->Size = Loc.Size; |
| for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(), |
| DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI) |
| if (Instruction *Inst = DI->getResult().getInst()) |
| RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey); |
| CacheInfo->NonLocalDeps.clear(); |
| } else if (CacheInfo->Size > Loc.Size) { |
| // This query's Size is less than the cached one. Conservatively restart |
| // the query using the greater size. |
| return getNonLocalPointerDepFromBB(Pointer, |
| Loc.getWithNewSize(CacheInfo->Size), |
| isLoad, StartBB, Result, Visited, |
| SkipFirstBlock); |
| } |
| |
| // If the query's TBAATag is inconsistent with the cached one, |
| // conservatively throw out the cached data and restart the query with |
| // no tag if needed. |
| if (CacheInfo->TBAATag != Loc.TBAATag) { |
| if (CacheInfo->TBAATag) { |
| CacheInfo->Pair = BBSkipFirstBlockPair(); |
| CacheInfo->TBAATag = 0; |
| for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(), |
| DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI) |
| if (Instruction *Inst = DI->getResult().getInst()) |
| RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey); |
| CacheInfo->NonLocalDeps.clear(); |
| } |
| if (Loc.TBAATag) |
| return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(), |
| isLoad, StartBB, Result, Visited, |
| SkipFirstBlock); |
| } |
| } |
| |
| NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps; |
| |
| // If we have valid cached information for exactly the block we are |
| // investigating, just return it with no recomputation. |
| if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) { |
| // We have a fully cached result for this query then we can just return the |
| // cached results and populate the visited set. However, we have to verify |
| // that we don't already have conflicting results for these blocks. Check |
| // to ensure that if a block in the results set is in the visited set that |
| // it was for the same pointer query. |
| if (!Visited.empty()) { |
| for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); |
| I != E; ++I) { |
| DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB()); |
| if (VI == Visited.end() || VI->second == Pointer.getAddr()) |
| continue; |
| |
| // We have a pointer mismatch in a block. Just return clobber, saying |
| // that something was clobbered in this result. We could also do a |
| // non-fully cached query, but there is little point in doing this. |
| return true; |
| } |
| } |
| |
| Value *Addr = Pointer.getAddr(); |
| for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); |
| I != E; ++I) { |
| Visited.insert(std::make_pair(I->getBB(), Addr)); |
| if (!I->getResult().isNonLocal() && DT->isReachableFromEntry(I->getBB())) |
| Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr)); |
| } |
| ++NumCacheCompleteNonLocalPtr; |
| return false; |
| } |
| |
| // Otherwise, either this is a new block, a block with an invalid cache |
| // pointer or one that we're about to invalidate by putting more info into it |
| // than its valid cache info. If empty, the result will be valid cache info, |
| // otherwise it isn't. |
| if (Cache->empty()) |
| CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock); |
| else |
| CacheInfo->Pair = BBSkipFirstBlockPair(); |
| |
| SmallVector<BasicBlock*, 32> Worklist; |
| Worklist.push_back(StartBB); |
| |
| // PredList used inside loop. |
| SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList; |
| |
| // Keep track of the entries that we know are sorted. Previously cached |
| // entries will all be sorted. The entries we add we only sort on demand (we |
| // don't insert every element into its sorted position). We know that we |
| // won't get any reuse from currently inserted values, because we don't |
| // revisit blocks after we insert info for them. |
| unsigned NumSortedEntries = Cache->size(); |
| DEBUG(AssertSorted(*Cache)); |
| |
| while (!Worklist.empty()) { |
| BasicBlock *BB = Worklist.pop_back_val(); |
| |
| // Skip the first block if we have it. |
| if (!SkipFirstBlock) { |
| // Analyze the dependency of *Pointer in FromBB. See if we already have |
| // been here. |
| assert(Visited.count(BB) && "Should check 'visited' before adding to WL"); |
| |
| // Get the dependency info for Pointer in BB. If we have cached |
| // information, we will use it, otherwise we compute it. |
| DEBUG(AssertSorted(*Cache, NumSortedEntries)); |
| MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache, |
| NumSortedEntries); |
| |
| // If we got a Def or Clobber, add this to the list of results. |
| if (!Dep.isNonLocal() && DT->isReachableFromEntry(BB)) { |
| Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr())); |
| continue; |
| } |
| } |
| |
| // If 'Pointer' is an instruction defined in this block, then we need to do |
| // phi translation to change it into a value live in the predecessor block. |
| // If not, we just add the predecessors to the worklist and scan them with |
| // the same Pointer. |
| if (!Pointer.NeedsPHITranslationFromBlock(BB)) { |
| SkipFirstBlock = false; |
| SmallVector<BasicBlock*, 16> NewBlocks; |
| for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { |
| // Verify that we haven't looked at this block yet. |
| std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool> |
| InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr())); |
| if (InsertRes.second) { |
| // First time we've looked at *PI. |
| NewBlocks.push_back(*PI); |
| continue; |
| } |
| |
| // If we have seen this block before, but it was with a different |
| // pointer then we have a phi translation failure and we have to treat |
| // this as a clobber. |
| if (InsertRes.first->second != Pointer.getAddr()) { |
| // Make sure to clean up the Visited map before continuing on to |
| // PredTranslationFailure. |
| for (unsigned i = 0; i < NewBlocks.size(); i++) |
| Visited.erase(NewBlocks[i]); |
| goto PredTranslationFailure; |
| } |
| } |
| Worklist.append(NewBlocks.begin(), NewBlocks.end()); |
| continue; |
| } |
| |
| // We do need to do phi translation, if we know ahead of time we can't phi |
| // translate this value, don't even try. |
| if (!Pointer.IsPotentiallyPHITranslatable()) |
| goto PredTranslationFailure; |
| |
| // We may have added values to the cache list before this PHI translation. |
| // If so, we haven't done anything to ensure that the cache remains sorted. |
| // Sort it now (if needed) so that recursive invocations of |
| // getNonLocalPointerDepFromBB and other routines that could reuse the cache |
| // value will only see properly sorted cache arrays. |
| if (Cache && NumSortedEntries != Cache->size()) { |
| SortNonLocalDepInfoCache(*Cache, NumSortedEntries); |
| NumSortedEntries = Cache->size(); |
| } |
| Cache = 0; |
| |
| PredList.clear(); |
| for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { |
| BasicBlock *Pred = *PI; |
| PredList.push_back(std::make_pair(Pred, Pointer)); |
| |
| // Get the PHI translated pointer in this predecessor. This can fail if |
| // not translatable, in which case the getAddr() returns null. |
| PHITransAddr &PredPointer = PredList.back().second; |
| PredPointer.PHITranslateValue(BB, Pred, 0); |
| |
| Value *PredPtrVal = PredPointer.getAddr(); |
| |
| // Check to see if we have already visited this pred block with another |
| // pointer. If so, we can't do this lookup. This failure can occur |
| // with PHI translation when a critical edge exists and the PHI node in |
| // the successor translates to a pointer value different than the |
| // pointer the block was first analyzed with. |
| std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool> |
| InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal)); |
| |
| if (!InsertRes.second) { |
| // We found the pred; take it off the list of preds to visit. |
| PredList.pop_back(); |
| |
| // If the predecessor was visited with PredPtr, then we already did |
| // the analysis and can ignore it. |
| if (InsertRes.first->second == PredPtrVal) |
| continue; |
| |
| // Otherwise, the block was previously analyzed with a different |
| // pointer. We can't represent the result of this case, so we just |
| // treat this as a phi translation failure. |
| |
| // Make sure to clean up the Visited map before continuing on to |
| // PredTranslationFailure. |
| for (unsigned i = 0; i < PredList.size(); i++) |
| Visited.erase(PredList[i].first); |
| |
| goto PredTranslationFailure; |
| } |
| } |
| |
| // Actually process results here; this need to be a separate loop to avoid |
| // calling getNonLocalPointerDepFromBB for blocks we don't want to return |
| // any results for. (getNonLocalPointerDepFromBB will modify our |
| // datastructures in ways the code after the PredTranslationFailure label |
| // doesn't expect.) |
| for (unsigned i = 0; i < PredList.size(); i++) { |
| BasicBlock *Pred = PredList[i].first; |
| PHITransAddr &PredPointer = PredList[i].second; |
| Value *PredPtrVal = PredPointer.getAddr(); |
| |
| bool CanTranslate = true; |
| // If PHI translation was unable to find an available pointer in this |
| // predecessor, then we have to assume that the pointer is clobbered in |
| // that predecessor. We can still do PRE of the load, which would insert |
| // a computation of the pointer in this predecessor. |
| if (PredPtrVal == 0) |
| CanTranslate = false; |
| |
| // FIXME: it is entirely possible that PHI translating will end up with |
| // the same value. Consider PHI translating something like: |
| // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need* |
| // to recurse here, pedantically speaking. |
| |
| // If getNonLocalPointerDepFromBB fails here, that means the cached |
| // result conflicted with the Visited list; we have to conservatively |
| // assume it is unknown, but this also does not block PRE of the load. |
| if (!CanTranslate || |
| getNonLocalPointerDepFromBB(PredPointer, |
| Loc.getWithNewPtr(PredPtrVal), |
| isLoad, Pred, |
| Result, Visited)) { |
| // Add the entry to the Result list. |
| NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal); |
| Result.push_back(Entry); |
| |
| // Since we had a phi translation failure, the cache for CacheKey won't |
| // include all of the entries that we need to immediately satisfy future |
| // queries. Mark this in NonLocalPointerDeps by setting the |
| // BBSkipFirstBlockPair pointer to null. This requires reuse of the |
| // cached value to do more work but not miss the phi trans failure. |
| NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey]; |
| NLPI.Pair = BBSkipFirstBlockPair(); |
| continue; |
| } |
| } |
| |
| // Refresh the CacheInfo/Cache pointer so that it isn't invalidated. |
| CacheInfo = &NonLocalPointerDeps[CacheKey]; |
| Cache = &CacheInfo->NonLocalDeps; |
| NumSortedEntries = Cache->size(); |
| |
| // Since we did phi translation, the "Cache" set won't contain all of the |
| // results for the query. This is ok (we can still use it to accelerate |
| // specific block queries) but we can't do the fastpath "return all |
| // results from the set" Clear out the indicator for this. |
| CacheInfo->Pair = BBSkipFirstBlockPair(); |
| SkipFirstBlock = false; |
| continue; |
| |
| PredTranslationFailure: |
| // The following code is "failure"; we can't produce a sane translation |
| // for the given block. It assumes that we haven't modified any of |
| // our datastructures while processing the current block. |
| |
| if (Cache == 0) { |
| // Refresh the CacheInfo/Cache pointer if it got invalidated. |
| CacheInfo = &NonLocalPointerDeps[CacheKey]; |
| Cache = &CacheInfo->NonLocalDeps; |
| NumSortedEntries = Cache->size(); |
| } |
| |
| // Since we failed phi translation, the "Cache" set won't contain all of the |
| // results for the query. This is ok (we can still use it to accelerate |
| // specific block queries) but we can't do the fastpath "return all |
| // results from the set". Clear out the indicator for this. |
| CacheInfo->Pair = BBSkipFirstBlockPair(); |
| |
| // If *nothing* works, mark the pointer as unknown. |
| // |
| // If this is the magic first block, return this as a clobber of the whole |
| // incoming value. Since we can't phi translate to one of the predecessors, |
| // we have to bail out. |
| if (SkipFirstBlock) |
| return true; |
| |
| for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) { |
| assert(I != Cache->rend() && "Didn't find current block??"); |
| if (I->getBB() != BB) |
| continue; |
| |
| assert(I->getResult().isNonLocal() && |
| "Should only be here with transparent block"); |
| I->setResult(MemDepResult::getUnknown()); |
| Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), |
| Pointer.getAddr())); |
| break; |
| } |
| } |
| |
| // Okay, we're done now. If we added new values to the cache, re-sort it. |
| SortNonLocalDepInfoCache(*Cache, NumSortedEntries); |
| DEBUG(AssertSorted(*Cache)); |
| return false; |
| } |
| |
| /// RemoveCachedNonLocalPointerDependencies - If P exists in |
| /// CachedNonLocalPointerInfo, remove it. |
| void MemoryDependenceAnalysis:: |
| RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) { |
| CachedNonLocalPointerInfo::iterator It = |
| NonLocalPointerDeps.find(P); |
| if (It == NonLocalPointerDeps.end()) return; |
| |
| // Remove all of the entries in the BB->val map. This involves removing |
| // instructions from the reverse map. |
| NonLocalDepInfo &PInfo = It->second.NonLocalDeps; |
| |
| for (unsigned i = 0, e = PInfo.size(); i != e; ++i) { |
| Instruction *Target = PInfo[i].getResult().getInst(); |
| if (Target == 0) continue; // Ignore non-local dep results. |
| assert(Target->getParent() == PInfo[i].getBB()); |
| |
| // Eliminating the dirty entry from 'Cache', so update the reverse info. |
| RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P); |
| } |
| |
| // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo). |
| NonLocalPointerDeps.erase(It); |
| } |
| |
| |
| /// invalidateCachedPointerInfo - This method is used to invalidate cached |
| /// information about the specified pointer, because it may be too |
| /// conservative in memdep. This is an optional call that can be used when |
| /// the client detects an equivalence between the pointer and some other |
| /// value and replaces the other value with ptr. This can make Ptr available |
| /// in more places that cached info does not necessarily keep. |
| void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) { |
| // If Ptr isn't really a pointer, just ignore it. |
| if (!Ptr->getType()->isPointerTy()) return; |
| // Flush store info for the pointer. |
| RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false)); |
| // Flush load info for the pointer. |
| RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true)); |
| } |
| |
| /// invalidateCachedPredecessors - Clear the PredIteratorCache info. |
| /// This needs to be done when the CFG changes, e.g., due to splitting |
| /// critical edges. |
| void MemoryDependenceAnalysis::invalidateCachedPredecessors() { |
| PredCache->clear(); |
| } |
| |
| /// removeInstruction - Remove an instruction from the dependence analysis, |
| /// updating the dependence of instructions that previously depended on it. |
| /// This method attempts to keep the cache coherent using the reverse map. |
| void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) { |
| // Walk through the Non-local dependencies, removing this one as the value |
| // for any cached queries. |
| NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst); |
| if (NLDI != NonLocalDeps.end()) { |
| NonLocalDepInfo &BlockMap = NLDI->second.first; |
| for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end(); |
| DI != DE; ++DI) |
| if (Instruction *Inst = DI->getResult().getInst()) |
| RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst); |
| NonLocalDeps.erase(NLDI); |
| } |
| |
| // If we have a cached local dependence query for this instruction, remove it. |
| // |
| LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst); |
| if (LocalDepEntry != LocalDeps.end()) { |
| // Remove us from DepInst's reverse set now that the local dep info is gone. |
| if (Instruction *Inst = LocalDepEntry->second.getInst()) |
| RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst); |
| |
| // Remove this local dependency info. |
| LocalDeps.erase(LocalDepEntry); |
| } |
| |
| // If we have any cached pointer dependencies on this instruction, remove |
| // them. If the instruction has non-pointer type, then it can't be a pointer |
| // base. |
| |
| // Remove it from both the load info and the store info. The instruction |
| // can't be in either of these maps if it is non-pointer. |
| if (RemInst->getType()->isPointerTy()) { |
| RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false)); |
| RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true)); |
| } |
| |
| // Loop over all of the things that depend on the instruction we're removing. |
| // |
| SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd; |
| |
| // If we find RemInst as a clobber or Def in any of the maps for other values, |
| // we need to replace its entry with a dirty version of the instruction after |
| // it. If RemInst is a terminator, we use a null dirty value. |
| // |
| // Using a dirty version of the instruction after RemInst saves having to scan |
| // the entire block to get to this point. |
| MemDepResult NewDirtyVal; |
| if (!RemInst->isTerminator()) |
| NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst)); |
| |
| ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst); |
| if (ReverseDepIt != ReverseLocalDeps.end()) { |
| SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second; |
| // RemInst can't be the terminator if it has local stuff depending on it. |
| assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) && |
| "Nothing can locally depend on a terminator"); |
| |
| for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(), |
| E = ReverseDeps.end(); I != E; ++I) { |
| Instruction *InstDependingOnRemInst = *I; |
| assert(InstDependingOnRemInst != RemInst && |
| "Already removed our local dep info"); |
| |
| LocalDeps[InstDependingOnRemInst] = NewDirtyVal; |
| |
| // Make sure to remember that new things depend on NewDepInst. |
| assert(NewDirtyVal.getInst() && "There is no way something else can have " |
| "a local dep on this if it is a terminator!"); |
| ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(), |
| InstDependingOnRemInst)); |
| } |
| |
| ReverseLocalDeps.erase(ReverseDepIt); |
| |
| // Add new reverse deps after scanning the set, to avoid invalidating the |
| // 'ReverseDeps' reference. |
| while (!ReverseDepsToAdd.empty()) { |
| ReverseLocalDeps[ReverseDepsToAdd.back().first] |
| .insert(ReverseDepsToAdd.back().second); |
| ReverseDepsToAdd.pop_back(); |
| } |
| } |
| |
| ReverseDepIt = ReverseNonLocalDeps.find(RemInst); |
| if (ReverseDepIt != ReverseNonLocalDeps.end()) { |
| SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second; |
| for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end(); |
| I != E; ++I) { |
| assert(*I != RemInst && "Already removed NonLocalDep info for RemInst"); |
| |
| PerInstNLInfo &INLD = NonLocalDeps[*I]; |
| // The information is now dirty! |
| INLD.second = true; |
| |
| for (NonLocalDepInfo::iterator DI = INLD.first.begin(), |
| DE = INLD.first.end(); DI != DE; ++DI) { |
| if (DI->getResult().getInst() != RemInst) continue; |
| |
| // Convert to a dirty entry for the subsequent instruction. |
| DI->setResult(NewDirtyVal); |
| |
| if (Instruction *NextI = NewDirtyVal.getInst()) |
| ReverseDepsToAdd.push_back(std::make_pair(NextI, *I)); |
| } |
| } |
| |
| ReverseNonLocalDeps.erase(ReverseDepIt); |
| |
| // Add new reverse deps after scanning the set, to avoid invalidating 'Set' |
| while (!ReverseDepsToAdd.empty()) { |
| ReverseNonLocalDeps[ReverseDepsToAdd.back().first] |
| .insert(ReverseDepsToAdd.back().second); |
| ReverseDepsToAdd.pop_back(); |
| } |
| } |
| |
| // If the instruction is in ReverseNonLocalPtrDeps then it appears as a |
| // value in the NonLocalPointerDeps info. |
| ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt = |
| ReverseNonLocalPtrDeps.find(RemInst); |
| if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) { |
| SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second; |
| SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd; |
| |
| for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(), |
| E = Set.end(); I != E; ++I) { |
| ValueIsLoadPair P = *I; |
| assert(P.getPointer() != RemInst && |
| "Already removed NonLocalPointerDeps info for RemInst"); |
| |
| NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps; |
| |
| // The cache is not valid for any specific block anymore. |
| NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair(); |
| |
| // Update any entries for RemInst to use the instruction after it. |
| for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end(); |
| DI != DE; ++DI) { |
| if (DI->getResult().getInst() != RemInst) continue; |
| |
| // Convert to a dirty entry for the subsequent instruction. |
| DI->setResult(NewDirtyVal); |
| |
| if (Instruction *NewDirtyInst = NewDirtyVal.getInst()) |
| ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P)); |
| } |
| |
| // Re-sort the NonLocalDepInfo. Changing the dirty entry to its |
| // subsequent value may invalidate the sortedness. |
| std::sort(NLPDI.begin(), NLPDI.end()); |
| } |
| |
| ReverseNonLocalPtrDeps.erase(ReversePtrDepIt); |
| |
| while (!ReversePtrDepsToAdd.empty()) { |
| ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first] |
| .insert(ReversePtrDepsToAdd.back().second); |
| ReversePtrDepsToAdd.pop_back(); |
| } |
| } |
| |
| |
| assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?"); |
| AA->deleteValue(RemInst); |
| DEBUG(verifyRemoved(RemInst)); |
| } |
| /// verifyRemoved - Verify that the specified instruction does not occur |
| /// in our internal data structures. |
| void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const { |
| for (LocalDepMapType::const_iterator I = LocalDeps.begin(), |
| E = LocalDeps.end(); I != E; ++I) { |
| assert(I->first != D && "Inst occurs in data structures"); |
| assert(I->second.getInst() != D && |
| "Inst occurs in data structures"); |
| } |
| |
| for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(), |
| E = NonLocalPointerDeps.end(); I != E; ++I) { |
| assert(I->first.getPointer() != D && "Inst occurs in NLPD map key"); |
| const NonLocalDepInfo &Val = I->second.NonLocalDeps; |
| for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end(); |
| II != E; ++II) |
| assert(II->getResult().getInst() != D && "Inst occurs as NLPD value"); |
| } |
| |
| for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(), |
| E = NonLocalDeps.end(); I != E; ++I) { |
| assert(I->first != D && "Inst occurs in data structures"); |
| const PerInstNLInfo &INLD = I->second; |
| for (NonLocalDepInfo::const_iterator II = INLD.first.begin(), |
| EE = INLD.first.end(); II != EE; ++II) |
| assert(II->getResult().getInst() != D && "Inst occurs in data structures"); |
| } |
| |
| for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(), |
| E = ReverseLocalDeps.end(); I != E; ++I) { |
| assert(I->first != D && "Inst occurs in data structures"); |
| for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(), |
| EE = I->second.end(); II != EE; ++II) |
| assert(*II != D && "Inst occurs in data structures"); |
| } |
| |
| for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(), |
| E = ReverseNonLocalDeps.end(); |
| I != E; ++I) { |
| assert(I->first != D && "Inst occurs in data structures"); |
| for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(), |
| EE = I->second.end(); II != EE; ++II) |
| assert(*II != D && "Inst occurs in data structures"); |
| } |
| |
| for (ReverseNonLocalPtrDepTy::const_iterator |
| I = ReverseNonLocalPtrDeps.begin(), |
| E = ReverseNonLocalPtrDeps.end(); I != E; ++I) { |
| assert(I->first != D && "Inst occurs in rev NLPD map"); |
| |
| for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(), |
| E = I->second.end(); II != E; ++II) |
| assert(*II != ValueIsLoadPair(D, false) && |
| *II != ValueIsLoadPair(D, true) && |
| "Inst occurs in ReverseNonLocalPtrDeps map"); |
| } |
| |
| } |