-//===----------------------------------------------------------------------===//
-// ImmediatePostDominators Implementation
-//===----------------------------------------------------------------------===//
-
-static RegisterPass<ImmediatePostDominators>
-D("postidom", "Immediate Post-Dominators Construction", true);
-
-unsigned ImmediatePostDominators::DFSPass(BasicBlock *V, InfoRec &VInfo,
- unsigned N) {
- std::vector<std::pair<BasicBlock *, InfoRec *> > workStack;
- std::set<BasicBlock *> visited;
- workStack.push_back(std::make_pair(V, &VInfo));
-
- do {
- BasicBlock *currentBB = workStack.back().first;
- InfoRec *currentVInfo = workStack.back().second;
-
- // Visit each block only once.
- if (visited.count(currentBB) == 0) {
-
- visited.insert(currentBB);
- currentVInfo->Semi = ++N;
- currentVInfo->Label = currentBB;
-
- Vertex.push_back(currentBB); // Vertex[n] = current;
- // Info[currentBB].Ancestor = 0;
- // Ancestor[n] = 0
- // Child[currentBB] = 0;
- currentVInfo->Size = 1; // Size[currentBB] = 1
- }
-
- // Visit children
- bool visitChild = false;
- for (pred_iterator PI = pred_begin(currentBB), PE = pred_end(currentBB);
- PI != PE && !visitChild; ++PI) {
- InfoRec &SuccVInfo = Info[*PI];
- if (SuccVInfo.Semi == 0) {
- SuccVInfo.Parent = currentBB;
- if (visited.count (*PI) == 0) {
- workStack.push_back(std::make_pair(*PI, &SuccVInfo));
- visitChild = true;
- }
- }
- }
-
- // If all children are visited or if this block has no child then pop this
- // block out of workStack.
- if (!visitChild)
- workStack.pop_back();
-
- } while (!workStack.empty());
-
- return N;
-}
-
-void ImmediatePostDominators::Compress(BasicBlock *V, InfoRec &VInfo) {
- BasicBlock *VAncestor = VInfo.Ancestor;
- InfoRec &VAInfo = Info[VAncestor];
- if (VAInfo.Ancestor == 0)
- return;
-
- Compress(VAncestor, VAInfo);
-
- BasicBlock *VAncestorLabel = VAInfo.Label;
- BasicBlock *VLabel = VInfo.Label;
- if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
- VInfo.Label = VAncestorLabel;
-
- VInfo.Ancestor = VAInfo.Ancestor;
-}
-
-BasicBlock *ImmediatePostDominators::Eval(BasicBlock *V) {
- InfoRec &VInfo = Info[V];
-
- // Higher-complexity but faster implementation
- if (VInfo.Ancestor == 0)
- return V;
- Compress(V, VInfo);
- return VInfo.Label;
-}
-
-void ImmediatePostDominators::Link(BasicBlock *V, BasicBlock *W,
- InfoRec &WInfo) {
- // Higher-complexity but faster implementation
- WInfo.Ancestor = V;
-}
-
-bool ImmediatePostDominators::runOnFunction(Function &F) {
- IDoms.clear(); // Reset from the last time we were run...
- Roots.clear();
-
- // Step #0: Scan the function looking for the root nodes of the post-dominance
- // relationships. These blocks, which have no successors, end with return and
- // unwind instructions.
- for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
- if (succ_begin(I) == succ_end(I))
- Roots.push_back(I);
-
- Vertex.push_back(0);
-
- // Step #1: Number blocks in depth-first order and initialize variables used
- // in later stages of the algorithm.
- unsigned N = 0;
- for (unsigned i = 0, e = Roots.size(); i != e; ++i)
- N = DFSPass(Roots[i], Info[Roots[i]], N);
-
- for (unsigned i = N; i >= 2; --i) {
- BasicBlock *W = Vertex[i];
- InfoRec &WInfo = Info[W];
-
- // Step #2: Calculate the semidominators of all vertices
- for (succ_iterator SI = succ_begin(W), SE = succ_end(W); SI != SE; ++SI)
- if (Info.count(*SI)) { // Only if this predecessor is reachable!
- unsigned SemiU = Info[Eval(*SI)].Semi;
- if (SemiU < WInfo.Semi)
- WInfo.Semi = SemiU;
- }
-
- Info[Vertex[WInfo.Semi]].Bucket.push_back(W);
-
- BasicBlock *WParent = WInfo.Parent;
- Link(WParent, W, WInfo);
-
- // Step #3: Implicitly define the immediate dominator of vertices
- std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
- while (!WParentBucket.empty()) {
- BasicBlock *V = WParentBucket.back();
- WParentBucket.pop_back();
- BasicBlock *U = Eval(V);
- IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
- }
- }
-
- // Step #4: Explicitly define the immediate dominator of each vertex
- for (unsigned i = 2; i <= N; ++i) {
- BasicBlock *W = Vertex[i];
- BasicBlock *&WIDom = IDoms[W];
- if (WIDom != Vertex[Info[W].Semi])
- WIDom = IDoms[WIDom];
- }
-
- // Free temporary memory used to construct idom's
- Info.clear();
- std::vector<BasicBlock*>().swap(Vertex);
-
- return false;
-}