-/// At this point, we're committed to promoting the alloca using IDF's, and the
-/// standard SSA construction algorithm. Determine which blocks need phi nodes
-/// and see if we can optimize out some work by avoiding insertion of dead phi
-/// nodes.
-void PromoteMem2Reg::DetermineInsertionPoint(AllocaInst *AI, unsigned AllocaNum,
- AllocaInfo &Info) {
- // Unique the set of defining blocks for efficient lookup.
- SmallPtrSet<BasicBlock *, 32> DefBlocks;
- DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end());
-
- // Determine which blocks the value is live in. These are blocks which lead
- // to uses.
- SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
- ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks);
-
- // Use a priority queue keyed on dominator tree level so that inserted nodes
- // are handled from the bottom of the dominator tree upwards.
- typedef std::pair<DomTreeNode *, unsigned> DomTreeNodePair;
- typedef std::priority_queue<DomTreeNodePair, SmallVector<DomTreeNodePair, 32>,
- less_second> IDFPriorityQueue;
- IDFPriorityQueue PQ;
-
- for (BasicBlock *BB : DefBlocks) {
- if (DomTreeNode *Node = DT.getNode(BB))
- PQ.push(std::make_pair(Node, DomLevels[Node]));
- }
-
- SmallVector<std::pair<unsigned, BasicBlock *>, 32> DFBlocks;
- SmallVector<DomTreeNode *, 32> Worklist;
- SmallPtrSet<DomTreeNode *, 32> VisitedPQ;
- SmallPtrSet<DomTreeNode *, 32> VisitedWorklist;
-
- while (!PQ.empty()) {
- DomTreeNodePair RootPair = PQ.top();
- PQ.pop();
- DomTreeNode *Root = RootPair.first;
- unsigned RootLevel = RootPair.second;
-
- // Walk all dominator tree children of Root, inspecting their CFG edges with
- // targets elsewhere on the dominator tree. Only targets whose level is at
- // most Root's level are added to the iterated dominance frontier of the
- // definition set.
-
- Worklist.clear();
- Worklist.push_back(Root);
- VisitedWorklist.insert(Root);
-
- while (!Worklist.empty()) {
- DomTreeNode *Node = Worklist.pop_back_val();
- BasicBlock *BB = Node->getBlock();
-
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
- ++SI) {
- DomTreeNode *SuccNode = DT.getNode(*SI);
-
- // Quickly skip all CFG edges that are also dominator tree edges instead
- // of catching them below.
- if (SuccNode->getIDom() == Node)
- continue;
-
- unsigned SuccLevel = DomLevels[SuccNode];
- if (SuccLevel > RootLevel)
- continue;
-
- if (!VisitedPQ.insert(SuccNode).second)
- continue;
-
- BasicBlock *SuccBB = SuccNode->getBlock();
- if (!LiveInBlocks.count(SuccBB))
- continue;
-
- DFBlocks.push_back(std::make_pair(BBNumbers[SuccBB], SuccBB));
- if (!DefBlocks.count(SuccBB))
- PQ.push(std::make_pair(SuccNode, SuccLevel));
- }
-
- for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end(); CI != CE;
- ++CI) {
- if (VisitedWorklist.insert(*CI).second)
- Worklist.push_back(*CI);
- }
- }
- }
-
- if (DFBlocks.size() > 1)
- std::sort(DFBlocks.begin(), DFBlocks.end());
-
- unsigned CurrentVersion = 0;
- for (unsigned i = 0, e = DFBlocks.size(); i != e; ++i)
- QueuePhiNode(DFBlocks[i].second, AllocaNum, CurrentVersion);
-}
-