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24dcbaf756
Nodes that had children outside of the post dominator tree (infinite loops) where removed from the post dominator tree. This seems to be wrong. Leave them in the tree. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93633 91177308-0d34-0410-b5e6-96231b3b80d8
345 lines
12 KiB
C++
345 lines
12 KiB
C++
//=== llvm/Analysis/DominatorInternals.h - Dominator Calculation -*- C++ -*-==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_DOMINATOR_INTERNALS_H
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#define LLVM_ANALYSIS_DOMINATOR_INTERNALS_H
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/ADT/SmallPtrSet.h"
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//===----------------------------------------------------------------------===//
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//
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// DominatorTree construction - This pass constructs immediate dominator
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// information for a flow-graph based on the algorithm described in this
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// document:
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//
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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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//
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//===----------------------------------------------------------------------===//
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namespace llvm {
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template<class GraphT>
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unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
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typename GraphT::NodeType* V, unsigned N) {
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// This is more understandable as a recursive algorithm, but we can't use the
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// recursive algorithm due to stack depth issues. Keep it here for
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// documentation purposes.
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#if 0
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InfoRec &VInfo = DT.Info[DT.Roots[i]];
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VInfo.DFSNum = VInfo.Semi = ++N;
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VInfo.Label = V;
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Vertex.push_back(V); // Vertex[n] = V;
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//Info[V].Ancestor = 0; // Ancestor[n] = 0
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//Info[V].Child = 0; // Child[v] = 0
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VInfo.Size = 1; // Size[v] = 1
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for (succ_iterator SI = succ_begin(V), E = succ_end(V); SI != E; ++SI) {
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InfoRec &SuccVInfo = DT.Info[*SI];
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if (SuccVInfo.Semi == 0) {
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SuccVInfo.Parent = V;
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N = DTDFSPass(DT, *SI, N);
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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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std::vector<std::pair<typename GraphT::NodeType*,
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typename GraphT::ChildIteratorType> > Worklist;
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Worklist.push_back(std::make_pair(V, GraphT::child_begin(V)));
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while (!Worklist.empty()) {
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typename GraphT::NodeType* BB = Worklist.back().first;
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typename GraphT::ChildIteratorType NextSucc = Worklist.back().second;
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &BBInfo =
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DT.Info[BB];
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// First time we visited this BB?
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if (NextSucc == GraphT::child_begin(BB)) {
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BBInfo.DFSNum = BBInfo.Semi = ++N;
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BBInfo.Label = BB;
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DT.Vertex.push_back(BB); // Vertex[n] = V;
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//BBInfo[V].Ancestor = 0; // Ancestor[n] = 0
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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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BBInfo.Parent = 1;
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IsChilOfArtificialExit = 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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// get invalidated when processing the successors.
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unsigned BBDFSNum = BBInfo.DFSNum;
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// If we are done with this block, remove it from the worklist.
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if (NextSucc == GraphT::child_end(BB)) {
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Worklist.pop_back();
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continue;
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}
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// Increment the successor number for the next time we get to it.
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++Worklist.back().second;
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// Visit the successor next, if it isn't already visited.
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typename GraphT::NodeType* Succ = *NextSucc;
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &SuccVInfo =
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DT.Info[Succ];
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if (SuccVInfo.Semi == 0) {
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SuccVInfo.Parent = BBDFSNum;
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Worklist.push_back(std::make_pair(Succ, GraphT::child_begin(Succ)));
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}
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}
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#endif
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return N;
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}
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template<class GraphT>
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void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT,
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typename GraphT::NodeType *VIn) {
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std::vector<typename GraphT::NodeType*> Work;
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SmallPtrSet<typename GraphT::NodeType*, 32> Visited;
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInVAInfo =
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DT.Info[DT.Vertex[DT.Info[VIn].Ancestor]];
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if (VInVAInfo.Ancestor != 0)
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Work.push_back(VIn);
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while (!Work.empty()) {
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typename GraphT::NodeType* V = Work.back();
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInfo =
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DT.Info[V];
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typename GraphT::NodeType* VAncestor = DT.Vertex[VInfo.Ancestor];
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VAInfo =
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DT.Info[VAncestor];
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// Process Ancestor first
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if (Visited.insert(VAncestor) &&
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VAInfo.Ancestor != 0) {
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Work.push_back(VAncestor);
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continue;
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}
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Work.pop_back();
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// Update VInfo based on Ancestor info
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if (VAInfo.Ancestor == 0)
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continue;
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typename GraphT::NodeType* VAncestorLabel = VAInfo.Label;
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typename GraphT::NodeType* VLabel = VInfo.Label;
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if (DT.Info[VAncestorLabel].Semi < DT.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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}
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template<class GraphT>
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typename GraphT::NodeType* 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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void Calculate(DominatorTreeBase<typename GraphTraits<NodeT>::NodeType>& DT,
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FuncT& F) {
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typedef GraphTraits<NodeT> GraphT;
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unsigned N = 0;
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bool MultipleRoots = (DT.Roots.size() > 1);
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if (MultipleRoots) {
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typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &BBInfo =
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DT.Info[NULL];
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BBInfo.DFSNum = BBInfo.Semi = ++N;
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BBInfo.Label = NULL;
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DT.Vertex.push_back(NULL); // Vertex[n] = V;
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//BBInfo[V].Ancestor = 0; // Ancestor[n] = 0
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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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}
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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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for (unsigned i = 0, e = static_cast<unsigned>(DT.Roots.size());
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i != e; ++i)
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N = DFSPass<GraphT>(DT, DT.Roots[i], N);
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// it might be that some blocks did not get a DFS number (e.g., blocks of
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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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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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// initialize the semi dominator to point to the parent node
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WInfo.Semi = WInfo.Parent;
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for (typename GraphTraits<Inverse<NodeT> >::ChildIteratorType CI =
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GraphTraits<Inverse<NodeT> >::child_begin(W),
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E = GraphTraits<Inverse<NodeT> >::child_end(W); CI != E; ++CI)
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if (DT.Info.count(*CI)) { // Only if this predecessor is reachable!
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unsigned SemiU = DT.Info[Eval<GraphT>(DT, *CI)].Semi;
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if (SemiU < WInfo.Semi)
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WInfo.Semi = SemiU;
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}
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DT.Info[DT.Vertex[WInfo.Semi]].Bucket.push_back(W);
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typename GraphT::NodeType* WParent = DT.Vertex[WInfo.Parent];
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Link<GraphT>(DT, WInfo.Parent, W, WInfo);
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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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}
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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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typename GraphT::NodeType* W = DT.Vertex[i];
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typename GraphT::NodeType*& WIDom = DT.IDoms[W];
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if (WIDom != DT.Vertex[DT.Info[W].Semi])
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WIDom = DT.IDoms[WIDom];
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}
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if (DT.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, or
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// an infinite loop.
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typename GraphT::NodeType* Root = !MultipleRoots ? DT.Roots[0] : 0;
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DT.DomTreeNodes[Root] = DT.RootNode =
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new DomTreeNodeBase<typename GraphT::NodeType>(Root, 0);
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// Loop over all of the reachable blocks in the function...
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for (unsigned i = 2; i <= N; ++i) {
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typename GraphT::NodeType* W = DT.Vertex[i];
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DomTreeNodeBase<typename GraphT::NodeType> *BBNode = DT.DomTreeNodes[W];
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if (BBNode) continue; // Haven't calculated this node yet?
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typename GraphT::NodeType* ImmDom = DT.getIDom(W);
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assert(ImmDom || DT.DomTreeNodes[NULL]);
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// Get or calculate the node for the immediate dominator
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DomTreeNodeBase<typename GraphT::NodeType> *IDomNode =
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DT.getNodeForBlock(ImmDom);
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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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DomTreeNodeBase<typename GraphT::NodeType> *C =
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new DomTreeNodeBase<typename GraphT::NodeType>(W, IDomNode);
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DT.DomTreeNodes[W] = IDomNode->addChild(C);
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}
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// Free temporary memory used to construct idom's
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DT.IDoms.clear();
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DT.Info.clear();
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std::vector<typename GraphT::NodeType*>().swap(DT.Vertex);
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DT.updateDFSNumbers();
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}
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}
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#endif
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