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313 lines
10 KiB
C++
313 lines
10 KiB
C++
//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the post-dominator construction algorithms.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/PostDominators.h"
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#include "llvm/Instructions.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SetOperations.h"
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// PostDominatorTree Implementation
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//===----------------------------------------------------------------------===//
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static RegisterPass<PostDominatorTree>
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F("postdomtree", "Post-Dominator Tree Construction", true);
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unsigned PostDominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
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unsigned N) {
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std::vector<std::pair<BasicBlock *, InfoRec *> > workStack;
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std::set<BasicBlock *> visited;
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workStack.push_back(std::make_pair(V, &VInfo));
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do {
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BasicBlock *currentBB = workStack.back().first;
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InfoRec *currentVInfo = workStack.back().second;
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// Visit each block only once.
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if (visited.count(currentBB) == 0) {
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visited.insert(currentBB);
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currentVInfo->Semi = ++N;
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currentVInfo->Label = currentBB;
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Vertex.push_back(currentBB); // Vertex[n] = current;
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// Info[currentBB].Ancestor = 0;
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// Ancestor[n] = 0
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// Child[currentBB] = 0;
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currentVInfo->Size = 1; // Size[currentBB] = 1
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}
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// Visit children
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bool visitChild = false;
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for (pred_iterator PI = pred_begin(currentBB), PE = pred_end(currentBB);
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PI != PE && !visitChild; ++PI) {
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InfoRec &SuccVInfo = Info[*PI];
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if (SuccVInfo.Semi == 0) {
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SuccVInfo.Parent = currentBB;
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if (visited.count (*PI) == 0) {
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workStack.push_back(std::make_pair(*PI, &SuccVInfo));
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visitChild = true;
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}
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}
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}
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// If all children are visited or if this block has no child then pop this
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// block out of workStack.
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if (!visitChild)
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workStack.pop_back();
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} while (!workStack.empty());
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return N;
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}
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void PostDominatorTree::Compress(BasicBlock *V, InfoRec &VInfo) {
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BasicBlock *VAncestor = VInfo.Ancestor;
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InfoRec &VAInfo = Info[VAncestor];
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if (VAInfo.Ancestor == 0)
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return;
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Compress(VAncestor, VAInfo);
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BasicBlock *VAncestorLabel = VAInfo.Label;
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BasicBlock *VLabel = VInfo.Label;
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if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
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VInfo.Label = VAncestorLabel;
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VInfo.Ancestor = VAInfo.Ancestor;
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}
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BasicBlock *PostDominatorTree::Eval(BasicBlock *V) {
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InfoRec &VInfo = Info[V];
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// Higher-complexity but faster implementation
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if (VInfo.Ancestor == 0)
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return V;
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Compress(V, VInfo);
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return VInfo.Label;
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}
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void PostDominatorTree::Link(BasicBlock *V, BasicBlock *W,
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InfoRec &WInfo) {
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// Higher-complexity but faster implementation
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WInfo.Ancestor = V;
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}
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void PostDominatorTree::calculate(Function &F) {
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// Step #0: Scan the function looking for the root nodes of the post-dominance
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// relationships. These blocks, which have no successors, end with return and
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// unwind instructions.
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (succ_begin(I) == succ_end(I))
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Roots.push_back(I);
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Vertex.push_back(0);
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// Step #1: Number blocks in depth-first order and initialize variables used
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// in later stages of the algorithm.
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unsigned N = 0;
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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N = DFSPass(Roots[i], Info[Roots[i]], N);
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for (unsigned i = N; i >= 2; --i) {
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BasicBlock *W = Vertex[i];
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InfoRec &WInfo = Info[W];
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// Step #2: Calculate the semidominators of all vertices
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for (succ_iterator SI = succ_begin(W), SE = succ_end(W); SI != SE; ++SI)
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if (Info.count(*SI)) { // Only if this predecessor is reachable!
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unsigned SemiU = Info[Eval(*SI)].Semi;
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if (SemiU < WInfo.Semi)
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WInfo.Semi = SemiU;
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}
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Info[Vertex[WInfo.Semi]].Bucket.push_back(W);
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BasicBlock *WParent = WInfo.Parent;
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Link(WParent, W, WInfo);
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// Step #3: Implicitly define the immediate dominator of vertices
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std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
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while (!WParentBucket.empty()) {
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BasicBlock *V = WParentBucket.back();
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WParentBucket.pop_back();
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BasicBlock *U = Eval(V);
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IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
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}
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}
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// Step #4: Explicitly define the immediate dominator of each vertex
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for (unsigned i = 2; i <= N; ++i) {
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BasicBlock *W = Vertex[i];
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BasicBlock *&WIDom = IDoms[W];
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if (WIDom != Vertex[Info[W].Semi])
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WIDom = IDoms[WIDom];
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}
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if (Roots.empty()) return;
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// Add a node for the root. This node might be the actual root, if there is
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// one exit block, or it may be the virtual exit (denoted by (BasicBlock *)0)
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// which postdominates all real exits if there are multiple exit blocks.
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BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
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Nodes[Root] = RootNode = new Node(Root, 0);
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// Loop over all of the reachable blocks in the function...
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (BasicBlock *ImmPostDom = getIDom(I)) { // Reachable block.
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Node *&BBNode = Nodes[I];
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if (!BBNode) { // Haven't calculated this node yet?
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// Get or calculate the node for the immediate dominator
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Node *IPDomNode = getNodeForBlock(ImmPostDom);
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// Add a new tree node for this BasicBlock, and link it as a child of
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// IDomNode
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BBNode = IPDomNode->addChild(new Node(I, IPDomNode));
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}
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}
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// Free temporary memory used to construct idom's
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IDoms.clear();
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Info.clear();
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std::vector<BasicBlock*>().swap(Vertex);
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}
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DominatorTreeBase::Node *PostDominatorTree::getNodeForBlock(BasicBlock *BB) {
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Node *&BBNode = Nodes[BB];
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if (BBNode) return BBNode;
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// Haven't calculated this node yet? Get or calculate the node for the
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// immediate postdominator.
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BasicBlock *IPDom = getIDom(BB);
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Node *IPDomNode = getNodeForBlock(IPDom);
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// Add a new tree node for this BasicBlock, and link it as a child of
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// IDomNode
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return BBNode = IPDomNode->addChild(new Node(BB, IPDomNode));
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}
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//===----------------------------------------------------------------------===//
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// PostETForest Implementation
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//===----------------------------------------------------------------------===//
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static RegisterPass<PostETForest>
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G("postetforest", "Post-ET-Forest Construction", true);
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ETNode *PostETForest::getNodeForBlock(BasicBlock *BB) {
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ETNode *&BBNode = Nodes[BB];
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if (BBNode) return BBNode;
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// Haven't calculated this node yet? Get or calculate the node for the
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// immediate dominator.
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PostDominatorTree::Node *node = getAnalysis<PostDominatorTree>().getNode(BB);
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// If we are unreachable, we may not have an immediate dominator.
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if (!node)
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return 0;
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else if (!node->getIDom())
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return BBNode = new ETNode(BB);
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else {
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ETNode *IDomNode = getNodeForBlock(node->getIDom()->getBlock());
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// Add a new tree node for this BasicBlock, and link it as a child of
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// IDomNode
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BBNode = new ETNode(BB);
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BBNode->setFather(IDomNode);
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return BBNode;
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}
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}
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void PostETForest::calculate(const PostDominatorTree &DT) {
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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Nodes[Roots[i]] = new ETNode(Roots[i]); // Add a node for the root
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// Iterate over all nodes in inverse depth first order.
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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for (idf_iterator<BasicBlock*> I = idf_begin(Roots[i]),
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E = idf_end(Roots[i]); I != E; ++I) {
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BasicBlock *BB = *I;
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ETNode *&BBNode = Nodes[BB];
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if (!BBNode) {
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ETNode *IDomNode = NULL;
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PostDominatorTree::Node *node = DT.getNode(BB);
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if (node && node->getIDom())
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IDomNode = getNodeForBlock(node->getIDom()->getBlock());
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// Add a new ETNode for this BasicBlock, and set it's parent
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// to it's immediate dominator.
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BBNode = new ETNode(BB);
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if (IDomNode)
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BBNode->setFather(IDomNode);
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}
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}
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int dfsnum = 0;
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// Iterate over all nodes in depth first order...
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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for (idf_iterator<BasicBlock*> I = idf_begin(Roots[i]),
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E = idf_end(Roots[i]); I != E; ++I) {
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if (!getNodeForBlock(*I)->hasFather())
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getNodeForBlock(*I)->assignDFSNumber(dfsnum);
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}
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DFSInfoValid = true;
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}
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//===----------------------------------------------------------------------===//
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// PostDominanceFrontier Implementation
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//===----------------------------------------------------------------------===//
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static RegisterPass<PostDominanceFrontier>
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H("postdomfrontier", "Post-Dominance Frontier Construction", true);
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const DominanceFrontier::DomSetType &
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PostDominanceFrontier::calculate(const PostDominatorTree &DT,
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const DominatorTree::Node *Node) {
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// Loop over CFG successors to calculate DFlocal[Node]
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BasicBlock *BB = Node->getBlock();
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DomSetType &S = Frontiers[BB]; // The new set to fill in...
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if (getRoots().empty()) return S;
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if (BB)
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for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
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SI != SE; ++SI) {
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// Does Node immediately dominate this predecessor?
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DominatorTree::Node *SINode = DT[*SI];
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if (SINode && SINode->getIDom() != Node)
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S.insert(*SI);
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}
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// At this point, S is DFlocal. Now we union in DFup's of our children...
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// Loop through and visit the nodes that Node immediately dominates (Node's
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// children in the IDomTree)
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//
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for (PostDominatorTree::Node::const_iterator
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NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
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DominatorTree::Node *IDominee = *NI;
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const DomSetType &ChildDF = calculate(DT, IDominee);
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DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
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for (; CDFI != CDFE; ++CDFI) {
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if (!Node->properlyDominates(DT[*CDFI]))
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S.insert(*CDFI);
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}
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}
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return S;
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}
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// Ensure that this .cpp file gets linked when PostDominators.h is used.
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DEFINING_FILE_FOR(PostDominanceFrontier)
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