//===- 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/Constants.h" #include "llvm/Instructions.h" #include "llvm/Function.h" #include "llvm/Analysis/AliasAnalysis.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" #include "llvm/Support/PredIteratorCache.h" #include "llvm/Support/Debug.h" #include "llvm/Target/TargetData.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"); char MemoryDependenceAnalysis::ID = 0; // Register this pass... static RegisterPass X("memdep", "Memory Dependence Analysis", false, true); MemoryDependenceAnalysis::MemoryDependenceAnalysis() : FunctionPass(&ID), PredCache(0) { } 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(); AU.addRequiredTransitive(); } bool MemoryDependenceAnalysis::runOnFunction(Function &) { AA = &getAnalysis(); TD = &getAnalysis(); 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 static void RemoveFromReverseMap(DenseMap > &ReverseMap, Instruction *Inst, KeyTy *Val) { typename DenseMap >::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!"); Found=Found; if (InstIt->second.empty()) ReverseMap.erase(InstIt); } /// getCallSiteDependencyFrom - Private helper for finding the local /// dependencies of a call site. MemDepResult MemoryDependenceAnalysis:: getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall, BasicBlock::iterator ScanIt, BasicBlock *BB) { // Walk backwards through the block, looking for dependencies while (ScanIt != BB->begin()) { Instruction *Inst = --ScanIt; // If this inst is a memory op, get the pointer it accessed Value *Pointer = 0; uint64_t PointerSize = 0; if (StoreInst *S = dyn_cast(Inst)) { Pointer = S->getPointerOperand(); PointerSize = TD->getTypeStoreSize(S->getOperand(0)->getType()); } else if (VAArgInst *V = dyn_cast(Inst)) { Pointer = V->getOperand(0); PointerSize = TD->getTypeStoreSize(V->getType()); } else if (FreeInst *F = dyn_cast(Inst)) { Pointer = F->getPointerOperand(); // FreeInsts erase the entire structure PointerSize = ~0ULL; } else if (isa(Inst) || isa(Inst)) { CallSite InstCS = CallSite::get(Inst); // If these two calls do not interfere, look past it. switch (AA->getModRefInfo(CS, InstCS)) { case AliasAnalysis::NoModRef: // If the two calls don't interact (e.g. InstCS is readnone) keep // scanning. continue; case AliasAnalysis::Ref: // If the two calls read the same memory locations and CS is a readonly // function, then we have two cases: 1) the calls may not interfere with // each other at all. 2) the calls may produce the same value. In case // #1 we want to ignore the values, in case #2, we want to return Inst // as a Def dependence. This allows us to CSE in cases like: // X = strlen(P); // memchr(...); // Y = strlen(P); // Y = X if (isReadOnlyCall) { if (CS.getCalledFunction() != 0 && CS.getCalledFunction() == InstCS.getCalledFunction()) return MemDepResult::getDef(Inst); // Ignore unrelated read/read call dependences. continue; } // FALL THROUGH default: return MemDepResult::getClobber(Inst); } } else { // Non-memory instruction. continue; } if (AA->getModRefInfo(CS, Pointer, PointerSize) != AliasAnalysis::NoModRef) return MemDepResult::getClobber(Inst); } // No dependence found. If this is the entry block of the function, it is a // clobber, otherwise it is non-local. if (BB != &BB->getParent()->getEntryBlock()) return MemDepResult::getNonLocal(); return MemDepResult::getClobber(ScanIt); } /// getPointerDependencyFrom - Return the instruction on which a memory /// location depends. If isLoad is true, this routine ignore may-aliases with /// read-only operations. MemDepResult MemoryDependenceAnalysis:: getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad, BasicBlock::iterator ScanIt, BasicBlock *BB) { // Walk backwards through the basic block, looking for dependencies. while (ScanIt != BB->begin()) { Instruction *Inst = --ScanIt; // 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(Inst)) { Value *Pointer = LI->getPointerOperand(); uint64_t PointerSize = TD->getTypeStoreSize(LI->getType()); // If we found a pointer, check if it could be the same as our pointer. AliasAnalysis::AliasResult R = AA->alias(Pointer, PointerSize, MemPtr, MemSize); if (R == AliasAnalysis::NoAlias) continue; // May-alias loads don't depend on each other without a dependence. if (isLoad && R == AliasAnalysis::MayAlias) continue; // Stores depend on may and must aliased loads, loads depend on must-alias // loads. return MemDepResult::getDef(Inst); } if (StoreInst *SI = dyn_cast(Inst)) { Value *Pointer = SI->getPointerOperand(); uint64_t PointerSize = TD->getTypeStoreSize(SI->getOperand(0)->getType()); // If we found a pointer, check if it could be the same as our pointer. AliasAnalysis::AliasResult R = AA->alias(Pointer, PointerSize, MemPtr, MemSize); if (R == AliasAnalysis::NoAlias) continue; if (R == AliasAnalysis::MayAlias) return MemDepResult::getClobber(Inst); return MemDepResult::getDef(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. if (AllocationInst *AI = dyn_cast(Inst)) { Value *AccessPtr = MemPtr->getUnderlyingObject(); if (AccessPtr == AI || AA->alias(AI, 1, AccessPtr, 1) == AliasAnalysis::MustAlias) return MemDepResult::getDef(AI); continue; } // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer. switch (AA->getModRefInfo(Inst, MemPtr, MemSize)) { case AliasAnalysis::NoModRef: // If the call has no effect on the queried pointer, just ignore it. continue; 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; // FALL THROUGH. 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 a // clobber, otherwise it is non-local. if (BB != &BB->getParent()->getEntryBlock()) return MemDepResult::getNonLocal(); return MemDepResult::getClobber(ScanIt); } /// 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(); Value *MemPtr = 0; uint64_t MemSize = 0; // Do the scan. if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) { // No dependence found. If this is the entry block of the function, it is a // clobber, otherwise it is non-local. if (QueryParent != &QueryParent->getParent()->getEntryBlock()) LocalCache = MemDepResult::getNonLocal(); else LocalCache = MemDepResult::getClobber(QueryInst); } else if (StoreInst *SI = dyn_cast(QueryInst)) { // If this is a volatile store, don't mess around with it. Just return the // previous instruction as a clobber. if (SI->isVolatile()) LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos)); else { MemPtr = SI->getPointerOperand(); MemSize = TD->getTypeStoreSize(SI->getOperand(0)->getType()); } } else if (LoadInst *LI = dyn_cast(QueryInst)) { // If this is a volatile load, don't mess around with it. Just return the // previous instruction as a clobber. if (LI->isVolatile()) LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos)); else { MemPtr = LI->getPointerOperand(); MemSize = TD->getTypeStoreSize(LI->getType()); } } else if (isa(QueryInst) || isa(QueryInst)) { CallSite QueryCS = CallSite::get(QueryInst); bool isReadOnly = AA->onlyReadsMemory(QueryCS); LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos, QueryParent); } else if (FreeInst *FI = dyn_cast(QueryInst)) { MemPtr = FI->getPointerOperand(); // FreeInsts erase the entire structure, not just a field. MemSize = ~0UL; } else { // Non-memory instruction. LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos)); } // If we need to do a pointer scan, make it happen. if (MemPtr) LocalCache = getPointerDependencyFrom(MemPtr, MemSize, isa(QueryInst), ScanPos, QueryParent); // Remember the result! if (Instruction *I = LocalCache.getInst()) ReverseLocalDeps[I].insert(QueryInst); return LocalCache; } /// 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 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->second.isDirty()) DirtyBlocks.push_back(I->first); // 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 Visited; unsigned NumSortedEntries = Cache.size(); // 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. NonLocalDepInfo::iterator Entry = std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries, std::make_pair(DirtyBB, MemDepResult())); if (Entry != Cache.begin() && prior(Entry)->first == DirtyBB) --Entry; MemDepResult *ExistingResult = 0; if (Entry != Cache.begin()+NumSortedEntries && Entry->first == DirtyBB) { // If we already have an entry, and if it isn't already dirty, the block // is done. if (!Entry->second.isDirty()) continue; // Otherwise, remember this slot so we can update the value. ExistingResult = &Entry->second; } // 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->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 non-local. Dep = MemDepResult::getNonLocal(); } else { Dep = MemDepResult::getClobber(ScanPos); } // If we had a dirty entry for the block, update it. Otherwise, just add // a new entry. if (ExistingResult) *ExistingResult = Dep; else Cache.push_back(std::make_pair(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(Value *Pointer, bool isLoad, BasicBlock *FromBB, SmallVectorImpl &Result) { assert(isa(Pointer->getType()) && "Can't get pointer deps of a non-pointer!"); Result.clear(); // We know that the pointer value is live into FromBB find the def/clobbers // from presecessors. const Type *EltTy = cast(Pointer->getType())->getElementType(); uint64_t PointeeSize = TD->getTypeStoreSize(EltTy); // 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 Visited; if (!getNonLocalPointerDepFromBB(Pointer, PointeeSize, isLoad, FromBB, Result, Visited, true)) return; Result.push_back(std::make_pair(FromBB, MemDepResult::getClobber(FromBB->begin()))); } /// 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(Value *Pointer, uint64_t PointeeSize, 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, std::make_pair(BB, MemDepResult())); if (Entry != Cache->begin() && prior(Entry)->first == BB) --Entry; MemDepResult *ExistingResult = 0; if (Entry != Cache->begin()+NumSortedEntries && Entry->first == BB) ExistingResult = &Entry->second; // If we have a cached entry, and it is non-dirty, use it as the value for // this dependency. if (ExistingResult && !ExistingResult->isDirty()) { ++NumCacheNonLocalPtr; return *ExistingResult; } // 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->getInst()) { assert(ExistingResult->getInst()->getParent() == BB && "Instruction invalidated?"); ++NumCacheDirtyNonLocalPtr; ScanPos = ExistingResult->getInst(); // Eliminating the dirty entry from 'Cache', so update the reverse info. ValueIsLoadPair CacheKey(Pointer, isLoad); RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey.getOpaqueValue()); } else { ++NumUncacheNonLocalPtr; } // Scan the block for the dependency. MemDepResult Dep = getPointerDependencyFrom(Pointer, PointeeSize, isLoad, ScanPos, BB); // If we had a dirty entry for the block, update it. Otherwise, just add // a new entry. if (ExistingResult) *ExistingResult = Dep; else Cache->push_back(std::make_pair(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.isNonLocal()) 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(Pointer, isLoad); ReverseNonLocalPtrDeps[Inst].insert(CacheKey.getOpaqueValue()); return Dep; } /// 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(Value *Pointer, uint64_t PointeeSize, bool isLoad, BasicBlock *StartBB, SmallVectorImpl &Result, DenseMap &Visited, bool SkipFirstBlock) { // Look up the cached info for Pointer. ValueIsLoadPair CacheKey(Pointer, isLoad); std::pair *CacheInfo = &NonLocalPointerDeps[CacheKey]; NonLocalDepInfo *Cache = &CacheInfo->second; // If we have valid cached information for exactly the block we are // investigating, just return it with no recomputation. if (CacheInfo->first == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) { for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); I != E; ++I) if (!I->second.isNonLocal()) Result.push_back(*I); ++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->first = BBSkipFirstBlockPair(StartBB, SkipFirstBlock); else CacheInfo->first = BBSkipFirstBlockPair(); SmallVector Worklist; Worklist.push_back(StartBB); // 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(); 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. MemDepResult Dep = GetNonLocalInfoForBlock(Pointer, PointeeSize, isLoad, BB, Cache, NumSortedEntries); // If we got a Def or Clobber, add this to the list of results. if (!Dep.isNonLocal()) { Result.push_back(NonLocalDepEntry(BB, Dep)); 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 phi translation fails, then we can't continue dependence analysis. Instruction *PtrInst = dyn_cast(Pointer); bool NeedsPHITranslation = PtrInst && PtrInst->getParent() == BB; // If no PHI translation is needed, just add all the predecessors of this // block to scan them as well. if (!NeedsPHITranslation) { SkipFirstBlock = false; for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { // Verify that we haven't looked at this block yet. std::pair::iterator, bool> InsertRes = Visited.insert(std::make_pair(*PI, Pointer)); if (InsertRes.second) { // First time we've looked at *PI. Worklist.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) goto PredTranslationFailure; } continue; } // If we do need to do phi translation, then there are a bunch of different // cases, because we have to find a Value* live in the predecessor block. We // know that PtrInst is defined in this block at least. // If this is directly a PHI node, just use the incoming values for each // pred as the phi translated version. if (PHINode *PtrPHI = dyn_cast(PtrInst)) { for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI){ BasicBlock *Pred = *PI; Value *PredPtr = PtrPHI->getIncomingValueForBlock(Pred); // 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::iterator, bool> InsertRes = Visited.insert(std::make_pair(Pred, PredPtr)); if (!InsertRes.second) { // If the predecessor was visited with PredPtr, then we already did // the analysis and can ignore it. if (InsertRes.first->second == PredPtr) 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. goto PredTranslationFailure; } // If we have a problem phi translating, fall through to the code below // to handle the failure condition. if (getNonLocalPointerDepFromBB(PredPtr, PointeeSize, isLoad, Pred, Result, Visited)) goto PredTranslationFailure; } // Refresh the CacheInfo/Cache pointer so that it isn't invalidated. CacheInfo = &NonLocalPointerDeps[CacheKey]; Cache = &CacheInfo->second; // 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->first = BBSkipFirstBlockPair(); SkipFirstBlock = false; continue; } // TODO: BITCAST, GEP. // cerr << "MEMDEP: Could not PHI translate: " << *Pointer; // if (isa(PtrInst) || isa(PtrInst)) // cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0); PredTranslationFailure: // Refresh the CacheInfo/Cache pointer so that it isn't invalidated. CacheInfo = &NonLocalPointerDeps[CacheKey]; Cache = &CacheInfo->second; // 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->first = BBSkipFirstBlockPair(); // If *nothing* works, mark the pointer as being clobbered by the first // instruction in this block. // // 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->first != BB) continue; assert(I->second.isNonLocal() && "Should only be here with transparent block"); I->second = MemDepResult::getClobber(BB->begin()); ReverseNonLocalPtrDeps[BB->begin()].insert(CacheKey.getOpaqueValue()); Result.push_back(*I); break; } } // Okay, we're done now. If we added new values to the cache, re-sort it. 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(); 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(); 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()); } 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.second; for (unsigned i = 0, e = PInfo.size(); i != e; ++i) { Instruction *Target = PInfo[i].second.getInst(); if (Target == 0) continue; // Ignore non-local dep results. assert(Target->getParent() == PInfo[i].first); // Eliminating the dirty entry from 'Cache', so update the reverse info. RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P.getOpaqueValue()); } // 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 (!isa(Ptr->getType())) return; // Flush store info for the pointer. RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false)); // Flush load info for the pointer. RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true)); } /// 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->second.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 (isa(RemInst->getType())) { RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false)); RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true)); } // Loop over all of the things that depend on the instruction we're removing. // SmallVector, 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 &ReverseDeps = ReverseDepIt->second; // RemInst can't be the terminator if it has local stuff depending on it. assert(!ReverseDeps.empty() && !isa(RemInst) && "Nothing can locally depend on a terminator"); for (SmallPtrSet::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 &Set = ReverseDepIt->second; for (SmallPtrSet::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->second.getInst() != RemInst) continue; // Convert to a dirty entry for the subsequent instruction. DI->second = 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 &Set = ReversePtrDepIt->second; SmallVector,8> ReversePtrDepsToAdd; for (SmallPtrSet::iterator I = Set.begin(), E = Set.end(); I != E; ++I) { ValueIsLoadPair P; P.setFromOpaqueValue(*I); assert(P.getPointer() != RemInst && "Already removed NonLocalPointerDeps info for RemInst"); NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].second; // The cache is not valid for any specific block anymore. NonLocalPointerDeps[P].first = 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->second.getInst() != RemInst) continue; // Convert to a dirty entry for the subsequent instruction. DI->second = NewDirtyVal; if (Instruction *NewDirtyInst = NewDirtyVal.getInst()) ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P)); } } ReverseNonLocalPtrDeps.erase(ReversePtrDepIt); while (!ReversePtrDepsToAdd.empty()) { ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first] .insert(ReversePtrDepsToAdd.back().second.getOpaqueValue()); 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.second; for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end(); II != E; ++II) assert(II->second.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->second.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::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::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::const_iterator II = I->second.begin(), E = I->second.end(); II != E; ++II) assert(*II != ValueIsLoadPair(D, false).getOpaqueValue() && *II != ValueIsLoadPair(D, true).getOpaqueValue() && "Inst occurs in ReverseNonLocalPtrDeps map"); } }