//===- 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/Instructions.h" #include "llvm/IntrinsicInst.h" #include "llvm/Function.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/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" #include "llvm/Support/PredIteratorCache.h" #include "llvm/Support/Debug.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(); } bool MemoryDependenceAnalysis::runOnFunction(Function &) { AA = &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 = AA->getTypeStoreSize(S->getOperand(0)->getType()); } else if (VAArgInst *V = dyn_cast(Inst)) { Pointer = V->getOperand(0); PointerSize = AA->getTypeStoreSize(V->getType()); } else if (isFreeCall(Inst)) { Pointer = Inst->getOperand(1); // calls to free() erase the entire structure PointerSize = ~0ULL; } else if (isa(Inst) || isa(Inst)) { // Debug intrinsics don't cause dependences. if (isa(Inst)) continue; 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) { Value *InvariantTag = 0; // Walk backwards through the basic block, looking for dependencies. while (ScanIt != BB->begin()) { Instruction *Inst = --ScanIt; // If we're in an invariant region, no dependencies can be found before // we pass an invariant-begin marker. if (InvariantTag == Inst) { InvariantTag = 0; continue; } if (IntrinsicInst *II = dyn_cast(Inst)) { // Debug intrinsics don't cause dependences. if (isa(Inst)) continue; // If we pass an invariant-end marker, then we've just entered an // invariant region and can start ignoring dependencies. if (II->getIntrinsicID() == Intrinsic::invariant_end) { // 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. AliasAnalysis::AliasResult R = AA->alias(II->getOperand(3), ~0U, MemPtr, ~0U); if (R == AliasAnalysis::MustAlias) { InvariantTag = II->getOperand(1); continue; } // If we reach a lifetime begin or end marker, then the query ends here // because the value is undefined. } else 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. AliasAnalysis::AliasResult R = AA->alias(II->getOperand(2), ~0U, MemPtr, ~0U); if (R == AliasAnalysis::MustAlias) return MemDepResult::getDef(II); } } // If we're querying on a load and we're in an invariant region, we're done // at this point. Nothing a load depends on can live in an invariant region. if (isLoad && InvariantTag) 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(Inst)) { Value *Pointer = LI->getPointerOperand(); uint64_t PointerSize = AA->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)) { // There can't be stores to the value we care about inside an // invariant region. if (InvariantTag) continue; // 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, MemPtr, MemSize) == 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. Value *Pointer = SI->getPointerOperand(); uint64_t PointerSize = AA->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. // 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. if (isa(Inst) || (isa(Inst) && extractMallocCall(Inst))) { Value *AccessPtr = MemPtr->getUnderlyingObject(); if (AccessPtr == Inst || AA->alias(Inst, 1, AccessPtr, 1) == AliasAnalysis::MustAlias) return MemDepResult::getDef(Inst); 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::Mod: // If we're in an invariant region, we can ignore calls that ONLY // modify the pointer. if (InvariantTag) continue; 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 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 = AA->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 = AA->getTypeStoreSize(LI->getType()); } } else if (isFreeCall(QueryInst)) { MemPtr = QueryInst->getOperand(1); // calls to free() erase the entire structure, not just a field. MemSize = ~0UL; } else if (isa(QueryInst) || isa(QueryInst)) { int IntrinsicID = 0; // Intrinsic IDs start at 1. if (IntrinsicInst *II = dyn_cast(QueryInst)) IntrinsicID = II->getIntrinsicID(); switch (IntrinsicID) { case Intrinsic::lifetime_start: case Intrinsic::lifetime_end: case Intrinsic::invariant_start: MemPtr = QueryInst->getOperand(2); MemSize = cast(QueryInst->getOperand(1))->getZExtValue(); break; case Intrinsic::invariant_end: MemPtr = QueryInst->getOperand(3); MemSize = cast(QueryInst->getOperand(2))->getZExtValue(); break; default: CallSite QueryCS = CallSite::get(QueryInst); bool isReadOnly = AA->onlyReadsMemory(QueryCS); LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos, QueryParent); break; } } else { // Non-memory instruction. LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos)); } // If we need to do a pointer scan, make it happen. if (MemPtr) { bool isLoad = !QueryInst->mayWriteToMemory(); if (IntrinsicInst *II = dyn_cast(QueryInst)) { isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_end; } LocalCache = getPointerDependencyFrom(MemPtr, MemSize, isLoad, ScanPos, QueryParent); } // 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 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 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 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->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(Value *Pointer, bool isLoad, BasicBlock *FromBB, SmallVectorImpl &Result) { assert(Pointer->getType()->isPointerTy() && "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 = AA->getTypeStoreSize(EltTy); PHITransAddr Address(Pointer, 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 Visited; if (!getNonLocalPointerDepFromBB(Address, PointeeSize, isLoad, FromBB, Result, Visited, true)) return; Result.clear(); Result.push_back(NonLocalDepResult(FromBB, MemDepResult::getClobber(FromBB->begin()), Pointer)); } /// 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, 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(Pointer, isLoad); RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey); } 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->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.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); 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, uint64_t PointeeSize, bool isLoad, BasicBlock *StartBB, SmallVectorImpl &Result, DenseMap &Visited, bool SkipFirstBlock) { // Look up the cached info for Pointer. ValueIsLoadPair CacheKey(Pointer.getAddr(), 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)) { // 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::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()) 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->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(); 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(Pointer.getAddr(), 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(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; 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.getAddr())); 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.getAddr()) goto PredTranslationFailure; } 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; for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { BasicBlock *Pred = *PI; // Get the PHI translated pointer in this predecessor. This can fail if // not translatable, in which case the getAddr() returns null. PHITransAddr PredPointer(Pointer); PredPointer.PHITranslateValue(BB, Pred); 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::iterator, bool> InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal)); if (!InsertRes.second) { // 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. goto PredTranslationFailure; } // 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) { // Add the entry to the Result list. NonLocalDepResult Entry(Pred, MemDepResult::getClobber(Pred->getTerminator()), 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. NonLocalPointerDeps[CacheKey].first = BBSkipFirstBlockPair(); continue; } // 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 we have a problem phi translating, fall through to the code below // to handle the failure condition. if (getNonLocalPointerDepFromBB(PredPointer, PointeeSize, isLoad, Pred, Result, Visited)) goto PredTranslationFailure; } // Refresh the CacheInfo/Cache pointer so that it isn't invalidated. CacheInfo = &NonLocalPointerDeps[CacheKey]; Cache = &CacheInfo->second; 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->first = BBSkipFirstBlockPair(); SkipFirstBlock = false; continue; PredTranslationFailure: if (Cache == 0) { // Refresh the CacheInfo/Cache pointer if it got invalidated. CacheInfo = &NonLocalPointerDeps[CacheKey]; Cache = &CacheInfo->second; 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->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->getBB() != BB) continue; assert(I->getResult().isNonLocal() && "Should only be here with transparent block"); I->setResult(MemDepResult::getClobber(BB->begin())); ReverseNonLocalPtrDeps[BB->begin()].insert(CacheKey); 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.second; 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, 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->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 &Set = ReversePtrDepIt->second; SmallVector,8> ReversePtrDepsToAdd; for (SmallPtrSet::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].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->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.second; 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::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) && *II != ValueIsLoadPair(D, true) && "Inst occurs in ReverseNonLocalPtrDeps map"); } }