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Put the Dominator improvements back in. They were not the cause of bootstrap miscomparisons.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123273 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -22,13 +22,9 @@
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// A Fast Algorithm for Finding Dominators in a Flowgraph
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// T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
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//
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// This implements both the O(n*ack(n)) and the O(n*log(n)) versions of EVAL and
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// LINK, but it turns out that the theoretically slower O(n*log(n))
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// implementation is actually faster than the "efficient" algorithm (even for
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// large CFGs) because the constant overheads are substantially smaller. The
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// lower-complexity version can be enabled with the following #define:
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//
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#define BALANCE_IDOM_TREE 0
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// This implements the O(n*log(n)) versions of EVAL and LINK, because it turns
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// out that the theoretically slower O(n*log(n)) implementation is actually
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// faster than the almost-linear O(n*alpha(n)) version, even for large CFGs.
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//
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//===----------------------------------------------------------------------===//
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@ -58,7 +54,7 @@ unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
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}
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}
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#else
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bool IsChilOfArtificialExit = (N != 0);
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bool IsChildOfArtificialExit = (N != 0);
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std::vector<std::pair<typename GraphT::NodeType*,
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typename GraphT::ChildIteratorType> > Worklist;
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@ -80,10 +76,10 @@ unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
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//BBInfo[V].Child = 0; // Child[v] = 0
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BBInfo.Size = 1; // Size[v] = 1
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if (IsChilOfArtificialExit)
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if (IsChildOfArtificialExit)
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BBInfo.Parent = 1;
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IsChilOfArtificialExit = false;
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IsChildOfArtificialExit = false;
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}
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// store the DFS number of the current BB - the reference to BBInfo might
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@ -157,75 +153,17 @@ Eval(DominatorTreeBase<typename GraphT::NodeType>& DT,
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typename GraphT::NodeType *V) {
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInfo =
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DT.Info[V];
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#if !BALANCE_IDOM_TREE
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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<GraphT>(DT, V);
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return VInfo.Label;
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#else
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// Lower-complexity but slower implementation
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if (VInfo.Ancestor == 0)
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return VInfo.Label;
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Compress<GraphT>(DT, V);
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GraphT::NodeType* VLabel = VInfo.Label;
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GraphT::NodeType* VAncestorLabel = DT.Info[VInfo.Ancestor].Label;
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if (DT.Info[VAncestorLabel].Semi >= DT.Info[VLabel].Semi)
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return VLabel;
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else
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return VAncestorLabel;
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#endif
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}
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template<class GraphT>
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void Link(DominatorTreeBase<typename GraphT::NodeType>& DT,
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unsigned DFSNumV, typename GraphT::NodeType* W,
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo) {
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#if !BALANCE_IDOM_TREE
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// Higher-complexity but faster implementation
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WInfo.Ancestor = DFSNumV;
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#else
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// Lower-complexity but slower implementation
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GraphT::NodeType* WLabel = WInfo.Label;
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unsigned WLabelSemi = DT.Info[WLabel].Semi;
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GraphT::NodeType* S = W;
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InfoRec *SInfo = &DT.Info[S];
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GraphT::NodeType* SChild = SInfo->Child;
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InfoRec *SChildInfo = &DT.Info[SChild];
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while (WLabelSemi < DT.Info[SChildInfo->Label].Semi) {
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GraphT::NodeType* SChildChild = SChildInfo->Child;
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if (SInfo->Size+DT.Info[SChildChild].Size >= 2*SChildInfo->Size) {
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SChildInfo->Ancestor = S;
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SInfo->Child = SChild = SChildChild;
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SChildInfo = &DT.Info[SChild];
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} else {
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SChildInfo->Size = SInfo->Size;
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S = SInfo->Ancestor = SChild;
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SInfo = SChildInfo;
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SChild = SChildChild;
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SChildInfo = &DT.Info[SChild];
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}
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}
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DominatorTreeBase::InfoRec &VInfo = DT.Info[V];
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SInfo->Label = WLabel;
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assert(V != W && "The optimization here will not work in this case!");
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unsigned WSize = WInfo.Size;
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unsigned VSize = (VInfo.Size += WSize);
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if (VSize < 2*WSize)
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std::swap(S, VInfo.Child);
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while (S) {
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SInfo = &DT.Info[S];
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SInfo->Ancestor = V;
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S = SInfo->Child;
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}
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#endif
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}
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template<class FuncT, class NodeT>
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@ -257,12 +195,34 @@ void Calculate(DominatorTreeBase<typename GraphTraits<NodeT>::NodeType>& DT,
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// infinite loops). In these cases an artificial exit node is required.
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MultipleRoots |= (DT.isPostDominator() && N != F.size());
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// When naively implemented, the Lengauer-Tarjan algorithm requires a separate
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// bucket for each vertex. However, this is unnecessary, because each vertex
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// is only placed into a single bucket (that of its semidominator), and each
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// vertex's bucket is processed before it is added to any bucket itself.
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//
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// Instead of using a bucket per vertex, we use a single array Buckets that
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// has two purposes. Before the vertex V with preorder number i is processed,
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// Buckets[i] stores the index of the first element in V's bucket. After V's
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// bucket is processed, Buckets[i] stores the index of the next element in the
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// bucket containing V, if any.
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std::vector<unsigned> Buckets;
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Buckets.resize(N + 1);
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for (unsigned i = 1; i <= N; ++i)
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Buckets[i] = i;
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for (unsigned i = N; i >= 2; --i) {
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typename GraphT::NodeType* W = DT.Vertex[i];
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo =
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DT.Info[W];
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// Step #2: Calculate the semidominators of all vertices
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// Step #2: Implicitly define the immediate dominator of vertices
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for (unsigned j = i; Buckets[j] != i; j = Buckets[j]) {
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typename GraphT::NodeType* V = DT.Vertex[Buckets[j]];
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typename GraphT::NodeType* U = Eval<GraphT>(DT, V);
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DT.IDoms[V] = DT.Info[U].Semi < i ? U : W;
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}
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// Step #3: Calculate the semidominators of all vertices
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// initialize the semi dominator to point to the parent node
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WInfo.Semi = WInfo.Parent;
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@ -278,26 +238,24 @@ void Calculate(DominatorTreeBase<typename GraphTraits<NodeT>::NodeType>& DT,
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}
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}
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typename GraphT::NodeType* WParent = DT.Vertex[WInfo.Parent];
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// If V is a non-root vertex and sdom(V) = parent(V), then idom(V) is
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// necessarily parent(V). In this case, set idom(V) here and avoid placing
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// V into a bucket.
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if (WInfo.Semi == WInfo.Parent)
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DT.IDoms[W] = WParent;
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else
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DT.Info[DT.Vertex[WInfo.Semi]].Bucket.push_back(W);
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if (WInfo.Semi == WInfo.Parent) {
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DT.IDoms[W] = DT.Vertex[WInfo.Parent];
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} else {
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Buckets[i] = Buckets[WInfo.Semi];
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Buckets[WInfo.Semi] = i;
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}
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Link<GraphT>(DT, WInfo.Parent, W, WInfo);
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}
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// Step #3: Implicitly define the immediate dominator of vertices
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std::vector<typename GraphT::NodeType*> &WParentBucket =
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DT.Info[WParent].Bucket;
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while (!WParentBucket.empty()) {
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typename GraphT::NodeType* V = WParentBucket.back();
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WParentBucket.pop_back();
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typename GraphT::NodeType* U = Eval<GraphT>(DT, V);
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DT.IDoms[V] = DT.Info[U].Semi < DT.Info[V].Semi ? U : WParent;
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if (N >= 1) {
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typename GraphT::NodeType* Root = DT.Vertex[1];
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for (unsigned j = 1; Buckets[j] != 1; j = Buckets[j]) {
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typename GraphT::NodeType* V = DT.Vertex[Buckets[j]];
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DT.IDoms[V] = Root;
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}
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}
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@ -200,8 +200,6 @@ protected:
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NodeT *Label, *Child;
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unsigned Parent, Ancestor;
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std::vector<NodeT*> Bucket;
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InfoRec() : DFSNum(0), Semi(0), Size(0), Label(0), Child(0), Parent(0),
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Ancestor(0) {}
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};
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@ -293,9 +291,6 @@ public:
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: DominatorBase<NodeT>(isPostDom), DFSInfoValid(false), SlowQueries(0) {}
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virtual ~DominatorTreeBase() { reset(); }
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// FIXME: Should remove this
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virtual bool runOnFunction(Function &F) { return false; }
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/// compare - Return false if the other dominator tree base matches this
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/// dominator tree base. Otherwise return true.
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bool compare(DominatorTreeBase &Other) const {
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