+namespace {
+ /// LVIValueHandle - A callback value handle updates the cache when
+ /// values are erased.
+ class LazyValueInfoCache;
+ struct LVIValueHandle : public CallbackVH {
+ LazyValueInfoCache *Parent;
+
+ LVIValueHandle(Value *V, LazyValueInfoCache *P)
+ : CallbackVH(V), Parent(P) { }
+
+ void deleted() override;
+ void allUsesReplacedWith(Value *V) override {
+ deleted();
+ }
+ };
+}
+
+namespace {
+ /// LazyValueInfoCache - This is the cache kept by LazyValueInfo which
+ /// maintains information about queries across the clients' queries.
+ class LazyValueInfoCache {
+ /// ValueCacheEntryTy - This is all of the cached block information for
+ /// exactly one Value*. The entries are sorted by the BasicBlock* of the
+ /// entries, allowing us to do a lookup with a binary search.
+ typedef std::map<AssertingVH<BasicBlock>, LVILatticeVal> ValueCacheEntryTy;
+
+ /// ValueCache - This is all of the cached information for all values,
+ /// mapped from Value* to key information.
+ std::map<LVIValueHandle, ValueCacheEntryTy> ValueCache;
+
+ /// OverDefinedCache - This tracks, on a per-block basis, the set of
+ /// values that are over-defined at the end of that block. This is required
+ /// for cache updating.
+ typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
+ DenseSet<OverDefinedPairTy> OverDefinedCache;
+
+ /// SeenBlocks - Keep track of all blocks that we have ever seen, so we
+ /// don't spend time removing unused blocks from our caches.
+ DenseSet<AssertingVH<BasicBlock> > SeenBlocks;
+
+ /// BlockValueStack - This stack holds the state of the value solver
+ /// during a query. It basically emulates the callstack of the naive
+ /// recursive value lookup process.
+ std::stack<std::pair<BasicBlock*, Value*> > BlockValueStack;
+
+ friend struct LVIValueHandle;
+
+ /// OverDefinedCacheUpdater - A helper object that ensures that the
+ /// OverDefinedCache is updated whenever solveBlockValue returns.
+ struct OverDefinedCacheUpdater {
+ LazyValueInfoCache *Parent;
+ Value *Val;
+ BasicBlock *BB;
+ LVILatticeVal &BBLV;
+
+ OverDefinedCacheUpdater(Value *V, BasicBlock *B, LVILatticeVal &LV,
+ LazyValueInfoCache *P)
+ : Parent(P), Val(V), BB(B), BBLV(LV) { }
+
+ bool markResult(bool changed) {
+ if (changed && BBLV.isOverdefined())
+ Parent->OverDefinedCache.insert(std::make_pair(BB, Val));
+ return changed;
+ }
+ };
+
+
+
+ LVILatticeVal getBlockValue(Value *Val, BasicBlock *BB);
+ bool getEdgeValue(Value *V, BasicBlock *F, BasicBlock *T,
+ LVILatticeVal &Result);
+ bool hasBlockValue(Value *Val, BasicBlock *BB);
+
+ // These methods process one work item and may add more. A false value
+ // returned means that the work item was not completely processed and must
+ // be revisited after going through the new items.
+ bool solveBlockValue(Value *Val, BasicBlock *BB);
+ bool solveBlockValueNonLocal(LVILatticeVal &BBLV,
+ Value *Val, BasicBlock *BB);
+ bool solveBlockValuePHINode(LVILatticeVal &BBLV,
+ PHINode *PN, BasicBlock *BB);
+ bool solveBlockValueConstantRange(LVILatticeVal &BBLV,
+ Instruction *BBI, BasicBlock *BB);
+
+ void solve();
+
+ ValueCacheEntryTy &lookup(Value *V) {
+ return ValueCache[LVIValueHandle(V, this)];
+ }
+
+ public:
+ /// getValueInBlock - This is the query interface to determine the lattice
+ /// value for the specified Value* at the end of the specified block.
+ LVILatticeVal getValueInBlock(Value *V, BasicBlock *BB);
+
+ /// getValueOnEdge - This is the query interface to determine the lattice
+ /// value for the specified Value* that is true on the specified edge.
+ LVILatticeVal getValueOnEdge(Value *V, BasicBlock *FromBB,BasicBlock *ToBB);
+
+ /// threadEdge - This is the update interface to inform the cache that an
+ /// edge from PredBB to OldSucc has been threaded to be from PredBB to
+ /// NewSucc.
+ void threadEdge(BasicBlock *PredBB,BasicBlock *OldSucc,BasicBlock *NewSucc);
+
+ /// eraseBlock - This is part of the update interface to inform the cache
+ /// that a block has been deleted.
+ void eraseBlock(BasicBlock *BB);
+
+ /// clear - Empty the cache.
+ void clear() {
+ SeenBlocks.clear();
+ ValueCache.clear();
+ OverDefinedCache.clear();
+ }
+ };
+} // end anonymous namespace
+
+void LVIValueHandle::deleted() {
+ typedef std::pair<AssertingVH<BasicBlock>, Value*> OverDefinedPairTy;
+
+ SmallVector<OverDefinedPairTy, 4> ToErase;
+ for (DenseSet<OverDefinedPairTy>::iterator
+ I = Parent->OverDefinedCache.begin(),
+ E = Parent->OverDefinedCache.end();
+ I != E; ++I) {
+ if (I->second == getValPtr())
+ ToErase.push_back(*I);
+ }
+
+ for (SmallVectorImpl<OverDefinedPairTy>::iterator I = ToErase.begin(),
+ E = ToErase.end(); I != E; ++I)
+ Parent->OverDefinedCache.erase(*I);
+
+ // This erasure deallocates *this, so it MUST happen after we're done
+ // using any and all members of *this.
+ Parent->ValueCache.erase(*this);
+}
+
+void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
+ // Shortcut if we have never seen this block.
+ DenseSet<AssertingVH<BasicBlock> >::iterator I = SeenBlocks.find(BB);
+ if (I == SeenBlocks.end())
+ return;
+ SeenBlocks.erase(I);
+
+ SmallVector<OverDefinedPairTy, 4> ToErase;
+ for (DenseSet<OverDefinedPairTy>::iterator I = OverDefinedCache.begin(),
+ E = OverDefinedCache.end(); I != E; ++I) {
+ if (I->first == BB)
+ ToErase.push_back(*I);
+ }
+
+ for (SmallVectorImpl<OverDefinedPairTy>::iterator I = ToErase.begin(),
+ E = ToErase.end(); I != E; ++I)
+ OverDefinedCache.erase(*I);
+
+ for (std::map<LVIValueHandle, ValueCacheEntryTy>::iterator
+ I = ValueCache.begin(), E = ValueCache.end(); I != E; ++I)
+ I->second.erase(BB);
+}
+
+void LazyValueInfoCache::solve() {
+ while (!BlockValueStack.empty()) {
+ std::pair<BasicBlock*, Value*> &e = BlockValueStack.top();
+ if (solveBlockValue(e.second, e.first)) {
+ assert(BlockValueStack.top() == e);
+ BlockValueStack.pop();
+ }
+ }
+}
+
+bool LazyValueInfoCache::hasBlockValue(Value *Val, BasicBlock *BB) {
+ // If already a constant, there is nothing to compute.
+ if (isa<Constant>(Val))
+ return true;
+
+ LVIValueHandle ValHandle(Val, this);
+ std::map<LVIValueHandle, ValueCacheEntryTy>::iterator I =
+ ValueCache.find(ValHandle);
+ if (I == ValueCache.end()) return false;
+ return I->second.count(BB);
+}
+
+LVILatticeVal LazyValueInfoCache::getBlockValue(Value *Val, BasicBlock *BB) {
+ // If already a constant, there is nothing to compute.
+ if (Constant *VC = dyn_cast<Constant>(Val))
+ return LVILatticeVal::get(VC);
+
+ SeenBlocks.insert(BB);
+ return lookup(Val)[BB];
+}
+
+bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
+ if (isa<Constant>(Val))
+ return true;
+
+ ValueCacheEntryTy &Cache = lookup(Val);
+ SeenBlocks.insert(BB);
+ LVILatticeVal &BBLV = Cache[BB];
+
+ // OverDefinedCacheUpdater is a helper object that will update
+ // the OverDefinedCache for us when this method exits. Make sure to
+ // call markResult on it as we exist, passing a bool to indicate if the
+ // cache needs updating, i.e. if we have solve a new value or not.
+ OverDefinedCacheUpdater ODCacheUpdater(Val, BB, BBLV, this);
+
+ // Once this BB is encountered, Val's value for this BB will not be Undefined
+ // any longer. When we encounter this BB again, if Val's value is Overdefined,
+ // we need to compute its value again.
+ //
+ // For example, considering this control flow,
+ // BB1->BB2, BB1->BB3, BB2->BB3, BB2->BB4
+ //
+ // Suppose we have "icmp slt %v, 0" in BB1, and "icmp sgt %v, 0" in BB3. At
+ // the very beginning, when analyzing edge BB2->BB3, we don't know %v's value
+ // in BB2, and the data flow algorithm tries to compute BB2's predecessors, so
+ // then we know %v has negative value on edge BB1->BB2. And then we return to
+ // check BB2 again, and at this moment BB2 has Overdefined value for %v in
+ // BB2. So we should have to follow data flow propagation algorithm to get the
+ // value on edge BB1->BB2 propagated to BB2, and finally %v on BB2 has a
+ // constant range describing a negative value.
+
+ if (!BBLV.isUndefined() && !BBLV.isOverdefined()) {
+ DEBUG(dbgs() << " reuse BB '" << BB->getName() << "' val=" << BBLV <<'\n');
+
+ // Since we're reusing a cached value here, we don't need to update the
+ // OverDefinedCahce. The cache will have been properly updated
+ // whenever the cached value was inserted.
+ ODCacheUpdater.markResult(false);
+ return true;
+ }
+
+ // Otherwise, this is the first time we're seeing this block. Reset the
+ // lattice value to overdefined, so that cycles will terminate and be
+ // conservatively correct.
+ BBLV.markOverdefined();
+
+ Instruction *BBI = dyn_cast<Instruction>(Val);
+ if (!BBI || BBI->getParent() != BB) {
+ return ODCacheUpdater.markResult(solveBlockValueNonLocal(BBLV, Val, BB));
+ }
+
+ if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
+ return ODCacheUpdater.markResult(solveBlockValuePHINode(BBLV, PN, BB));
+ }
+
+ if (AllocaInst *AI = dyn_cast<AllocaInst>(BBI)) {
+ BBLV = LVILatticeVal::getNot(ConstantPointerNull::get(AI->getType()));
+ return ODCacheUpdater.markResult(true);
+ }
+
+ // We can only analyze the definitions of certain classes of instructions
+ // (integral binops and casts at the moment), so bail if this isn't one.
+ LVILatticeVal Result;
+ if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
+ !BBI->getType()->isIntegerTy()) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because inst def found.\n");
+ BBLV.markOverdefined();
+ return ODCacheUpdater.markResult(true);
+ }
+
+ // FIXME: We're currently limited to binops with a constant RHS. This should
+ // be improved.
+ BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
+ if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
+ DEBUG(dbgs() << " compute BB '" << BB->getName()
+ << "' - overdefined because inst def found.\n");
+
+ BBLV.markOverdefined();
+ return ODCacheUpdater.markResult(true);
+ }
+
+ return ODCacheUpdater.markResult(solveBlockValueConstantRange(BBLV, BBI, BB));
+}
+
+static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
+ if (LoadInst *L = dyn_cast<LoadInst>(I)) {
+ return L->getPointerAddressSpace() == 0 &&
+ GetUnderlyingObject(L->getPointerOperand()) == Ptr;
+ }
+ if (StoreInst *S = dyn_cast<StoreInst>(I)) {
+ return S->getPointerAddressSpace() == 0 &&
+ GetUnderlyingObject(S->getPointerOperand()) == Ptr;
+ }
+ if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
+ if (MI->isVolatile()) return false;
+
+ // FIXME: check whether it has a valuerange that excludes zero?
+ ConstantInt *Len = dyn_cast<ConstantInt>(MI->getLength());
+ if (!Len || Len->isZero()) return false;
+
+ if (MI->getDestAddressSpace() == 0)
+ if (GetUnderlyingObject(MI->getRawDest()) == Ptr)
+ return true;
+ if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
+ if (MTI->getSourceAddressSpace() == 0)
+ if (GetUnderlyingObject(MTI->getRawSource()) == Ptr)
+ return true;
+ }