-void PostDominatorTree::calculate(Function &F) {
- // 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)) {
- Instruction *Insn = I->getTerminator();
- // Unreachable block is not a root node.
- if (!isa<UnreachableInst>(Insn))
- 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];
- }
-
- if (Roots.empty()) return;
-
- // Add a node for the root. This node might be the actual root, if there is
- // one exit block, or it may be the virtual exit (denoted by (BasicBlock *)0)
- // which postdominates all real exits if there are multiple exit blocks.
- BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
- DomTreeNodes[Root] = RootNode = new DomTreeNode(Root, 0);
-
- // Loop over all of the reachable blocks in the function...
- for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
- if (BasicBlock *ImmPostDom = getIDom(I)) { // Reachable block.
- DomTreeNode *&BBNode = DomTreeNodes[I];
- if (!BBNode) { // Haven't calculated this node yet?
- // Get or calculate the node for the immediate dominator
- DomTreeNode *IPDomNode = getNodeForBlock(ImmPostDom);
-
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- DomTreeNode *C = new DomTreeNode(I, IPDomNode);
- DomTreeNodes[I] = C;
- BBNode = IPDomNode->addChild(C);
- }
- }
-
- // Free temporary memory used to construct idom's
- IDoms.clear();
- Info.clear();
- std::vector<BasicBlock*>().swap(Vertex);
-
- int dfsnum = 0;
- // Iterate over all nodes in depth first order...
- for (unsigned i = 0, e = Roots.size(); i != e; ++i)
- for (idf_iterator<BasicBlock*> I = idf_begin(Roots[i]),
- E = idf_end(Roots[i]); I != E; ++I) {
- if (!getNodeForBlock(*I)->getIDom())
- getNodeForBlock(*I)->assignDFSNumber(dfsnum);
- }
- DFSInfoValid = true;