X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FMemoryDependenceAnalysis.cpp;h=f7180aae69edcfa789fa9263e888a8973e0873ef;hb=3666e7f4c161c50e5f6dcb0e015ca16bf69fb941;hp=5c481fb446fa3651494420de42698ef07bc0790d;hpb=d628f19f5df9e4033adce5af969049e90a90ae5d;p=oota-llvm.git diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp index 5c481fb446f..f7180aae69e 100644 --- a/lib/Analysis/MemoryDependenceAnalysis.cpp +++ b/lib/Analysis/MemoryDependenceAnalysis.cpp @@ -14,7 +14,6 @@ // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "memdep" #include "llvm/Analysis/MemoryDependenceAnalysis.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/Statistic.h" @@ -29,10 +28,12 @@ #include "llvm/IR/Instructions.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/IR/LLVMContext.h" +#include "llvm/IR/PredIteratorCache.h" #include "llvm/Support/Debug.h" -#include "llvm/Support/PredIteratorCache.h" using namespace llvm; +#define DEBUG_TYPE "memdep" + 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"); @@ -59,7 +60,7 @@ INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep", "Memory Dependence Analysis", false, true) MemoryDependenceAnalysis::MemoryDependenceAnalysis() -: FunctionPass(ID), PredCache(0) { + : FunctionPass(ID), PredCache() { initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry()); } MemoryDependenceAnalysis::~MemoryDependenceAnalysis() { @@ -88,10 +89,10 @@ void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { bool MemoryDependenceAnalysis::runOnFunction(Function &) { AA = &getAnalysis(); DataLayoutPass *DLP = getAnalysisIfAvailable(); - DL = DLP ? &DLP->getDataLayout() : 0; + DL = DLP ? &DLP->getDataLayout() : nullptr; DominatorTreeWrapperPass *DTWP = getAnalysisIfAvailable(); - DT = DTWP ? &DTWP->getDomTree() : 0; + DT = DTWP ? &DTWP->getDomTree() : nullptr; if (!PredCache) PredCache.reset(new PredIteratorCache()); return false; @@ -157,29 +158,32 @@ AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst, return AliasAnalysis::Mod; } - if (const IntrinsicInst *II = dyn_cast(Inst)) + if (const IntrinsicInst *II = dyn_cast(Inst)) { + AAMDNodes AAInfo; + switch (II->getIntrinsicID()) { case Intrinsic::lifetime_start: case Intrinsic::lifetime_end: case Intrinsic::invariant_start: + II->getAAMetadata(AAInfo); Loc = AliasAnalysis::Location(II->getArgOperand(1), cast(II->getArgOperand(0)) - ->getZExtValue(), - II->getMetadata(LLVMContext::MD_tbaa)); + ->getZExtValue(), AAInfo); // 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: + II->getAAMetadata(AAInfo); Loc = AliasAnalysis::Location(II->getArgOperand(2), cast(II->getArgOperand(1)) - ->getZExtValue(), - II->getMetadata(LLVMContext::MD_tbaa)); + ->getZExtValue(), AAInfo); // 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()) @@ -261,10 +265,10 @@ isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc, const LoadInst *LI, const DataLayout *DL) { // If we have no target data, we can't do this. - if (DL == 0) return false; + if (!DL) return false; // If we haven't already computed the base/offset of MemLoc, do so now. - if (MemLocBase == 0) + if (!MemLocBase) MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, DL); unsigned Size = MemoryDependenceAnalysis:: @@ -362,13 +366,43 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad, BasicBlock::iterator ScanIt, BasicBlock *BB, Instruction *QueryInst) { - const Value *MemLocBase = 0; + const Value *MemLocBase = nullptr; int64_t MemLocOffset = 0; unsigned Limit = BlockScanLimit; bool isInvariantLoad = false; + + // We must be careful with atomic accesses, as they may allow another thread + // to touch this location, cloberring it. We are conservative: if the + // QueryInst is not a simple (non-atomic) memory access, we automatically + // return getClobber. + // If it is simple, we know based on the results of + // "Compiler testing via a theory of sound optimisations in the C11/C++11 + // memory model" in PLDI 2013, that a non-atomic location can only be + // clobbered between a pair of a release and an acquire action, with no + // access to the location in between. + // Here is an example for giving the general intuition behind this rule. + // In the following code: + // store x 0; + // release action; [1] + // acquire action; [4] + // %val = load x; + // It is unsafe to replace %val by 0 because another thread may be running: + // acquire action; [2] + // store x 42; + // release action; [3] + // with synchronization from 1 to 2 and from 3 to 4, resulting in %val + // being 42. A key property of this program however is that if either + // 1 or 4 were missing, there would be a race between the store of 42 + // either the store of 0 or the load (making the whole progam racy). + // The paper mentionned above shows that the same property is respected + // by every program that can detect any optimisation of that kind: either + // it is racy (undefined) or there is a release followed by an acquire + // between the pair of accesses under consideration. + bool HasSeenAcquire = false; + if (isLoad && QueryInst) { LoadInst *LI = dyn_cast(QueryInst); - if (LI && LI->getMetadata(LLVMContext::MD_invariant_load) != 0) + if (LI && LI->getMetadata(LLVMContext::MD_invariant_load) != nullptr) isInvariantLoad = true; } @@ -403,10 +437,37 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad, // 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. + // One exception is atomic loads: a value can depend on an atomic load that it + // does not alias with when this atomic load indicates that another thread may + // be accessing the location. if (LoadInst *LI = dyn_cast(Inst)) { // Atomic loads have complications involved. + // A Monotonic (or higher) load is OK if the query inst is itself not atomic. + // An Acquire (or higher) load sets the HasSeenAcquire flag, so that any + // release store will know to return getClobber. // FIXME: This is overly conservative. - if (!LI->isUnordered()) + if (!LI->isUnordered()) { + if (!QueryInst) + return MemDepResult::getClobber(LI); + if (auto *QueryLI = dyn_cast(QueryInst)) { + if (!QueryLI->isSimple()) + return MemDepResult::getClobber(LI); + } else if (auto *QuerySI = dyn_cast(QueryInst)) { + if (!QuerySI->isSimple()) + return MemDepResult::getClobber(LI); + } else if (QueryInst->mayReadOrWriteMemory()) { + return MemDepResult::getClobber(LI); + } + + if (isAtLeastAcquire(LI->getOrdering())) + HasSeenAcquire = true; + } + + // FIXME: this is overly conservative. + // While volatile access cannot be eliminated, they do not have to clobber + // non-aliasing locations, as normal accesses can for example be reordered + // with volatile accesses. + if (LI->isVolatile()) return MemDepResult::getClobber(LI); AliasAnalysis::Location LoadLoc = AA->getLocation(LI); @@ -465,8 +526,32 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad, if (StoreInst *SI = dyn_cast(Inst)) { // Atomic stores have complications involved. + // A Monotonic store is OK if the query inst is itself not atomic. + // A Release (or higher) store further requires that no acquire load + // has been seen. // FIXME: This is overly conservative. - if (!SI->isUnordered()) + if (!SI->isUnordered()) { + if (!QueryInst) + return MemDepResult::getClobber(SI); + if (auto *QueryLI = dyn_cast(QueryInst)) { + if (!QueryLI->isSimple()) + return MemDepResult::getClobber(SI); + } else if (auto *QuerySI = dyn_cast(QueryInst)) { + if (!QuerySI->isSimple()) + return MemDepResult::getClobber(SI); + } else if (QueryInst->mayReadOrWriteMemory()) { + return MemDepResult::getClobber(SI); + } + + if (HasSeenAcquire && isAtLeastRelease(SI->getOrdering())) + return MemDepResult::getClobber(SI); + } + + // FIXME: this is overly conservative. + // While volatile access cannot be eliminated, they do not have to clobber + // non-aliasing locations, as normal accesses can for example be reordered + // with volatile accesses. + if (SI->isVolatile()) return MemDepResult::getClobber(SI); // If alias analysis can tell that this store is guaranteed to not modify @@ -696,7 +781,7 @@ MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) { if (Entry != Cache.begin() && std::prev(Entry)->getBB() == DirtyBB) --Entry; - NonLocalDepEntry *ExistingResult = 0; + NonLocalDepEntry *ExistingResult = nullptr; if (Entry != Cache.begin()+NumSortedEntries && Entry->getBB() == DirtyBB) { // If we already have an entry, and if it isn't already dirty, the block @@ -807,7 +892,7 @@ GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc, if (Entry != Cache->begin() && (Entry-1)->getBB() == BB) --Entry; - NonLocalDepEntry *ExistingResult = 0; + NonLocalDepEntry *ExistingResult = nullptr; if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB) ExistingResult = &*Entry; @@ -860,7 +945,7 @@ GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc, return Dep; } -/// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain +/// SortNonLocalDepInfoCache - Sort the 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 @@ -921,10 +1006,10 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, // 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. + // aa tags are consistent with the current query. NonLocalPointerInfo InitialNLPI; InitialNLPI.Size = Loc.Size; - InitialNLPI.TBAATag = Loc.TBAATag; + InitialNLPI.AATags = Loc.AATags; // Get the NLPI for CacheKey, inserting one into the map if it doesn't // already have one. @@ -954,21 +1039,21 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, SkipFirstBlock); } - // If the query's TBAATag is inconsistent with the cached one, + // If the query's AATags are 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) { + if (CacheInfo->AATags != Loc.AATags) { + if (CacheInfo->AATags) { CacheInfo->Pair = BBSkipFirstBlockPair(); - CacheInfo->TBAATag = 0; + CacheInfo->AATags = AAMDNodes(); 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(), + if (Loc.AATags) + return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutAATags(), isLoad, StartBB, Result, Visited, SkipFirstBlock); } @@ -1116,7 +1201,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, SortNonLocalDepInfoCache(*Cache, NumSortedEntries); NumSortedEntries = Cache->size(); } - Cache = 0; + Cache = nullptr; PredList.clear(); for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { @@ -1126,7 +1211,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &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); + PredPointer.PHITranslateValue(BB, Pred, nullptr); Value *PredPtrVal = PredPointer.getAddr(); @@ -1175,7 +1260,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, // 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) + if (!PredPtrVal) CanTranslate = false; // FIXME: it is entirely possible that PHI translating will end up with @@ -1224,7 +1309,7 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, // for the given block. It assumes that we haven't modified any of // our datastructures while processing the current block. - if (Cache == 0) { + if (!Cache) { // Refresh the CacheInfo/Cache pointer if it got invalidated. CacheInfo = &NonLocalPointerDeps[CacheKey]; Cache = &CacheInfo->NonLocalDeps; @@ -1279,7 +1364,7 @@ RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) { 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. + if (!Target) continue; // Ignore non-local dep results. assert(Target->getParent() == PInfo[i].getBB()); // Eliminating the dirty entry from 'Cache', so update the reverse info. @@ -1368,14 +1453,11 @@ void MemoryDependenceAnalysis::removeInstruction(Instruction *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) && + assert(!ReverseDepIt->second.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; + for (Instruction *InstDependingOnRemInst : ReverseDepIt->second) { assert(InstDependingOnRemInst != RemInst && "Already removed our local dep info"); @@ -1401,12 +1483,10 @@ void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) { 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"); + for (Instruction *I : ReverseDepIt->second) { + assert(I != RemInst && "Already removed NonLocalDep info for RemInst"); - PerInstNLInfo &INLD = NonLocalDeps[*I]; + PerInstNLInfo &INLD = NonLocalDeps[I]; // The information is now dirty! INLD.second = true; @@ -1418,7 +1498,7 @@ void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) { DI->setResult(NewDirtyVal); if (Instruction *NextI = NewDirtyVal.getInst()) - ReverseDepsToAdd.push_back(std::make_pair(NextI, *I)); + ReverseDepsToAdd.push_back(std::make_pair(NextI, I)); } } @@ -1437,12 +1517,9 @@ void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) { 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; + for (ValueIsLoadPair P : ReversePtrDepIt->second) { assert(P.getPointer() != RemInst && "Already removed NonLocalPointerDeps info for RemInst"); @@ -1483,8 +1560,10 @@ void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) { DEBUG(verifyRemoved(RemInst)); } /// verifyRemoved - Verify that the specified instruction does not occur -/// in our internal data structures. +/// in our internal data structures. This function verifies by asserting in +/// debug builds. void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const { +#ifndef NDEBUG for (LocalDepMapType::const_iterator I = LocalDeps.begin(), E = LocalDeps.end(); I != E; ++I) { assert(I->first != D && "Inst occurs in data structures"); @@ -1513,18 +1592,16 @@ void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const { 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 (Instruction *Inst : I->second) + assert(Inst != 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 (Instruction *Inst : I->second) + assert(Inst != D && "Inst occurs in data structures"); } for (ReverseNonLocalPtrDepTy::const_iterator @@ -1532,11 +1609,10 @@ void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const { 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) && + for (ValueIsLoadPair P : I->second) + assert(P != ValueIsLoadPair(D, false) && + P != ValueIsLoadPair(D, true) && "Inst occurs in ReverseNonLocalPtrDeps map"); } - +#endif }