Import LLVM, at r72732.

1 files changed, 363 insertions, 0 deletions

diff --git a/include/llvm/Analysis/DominatorInternals.h b/include/llvm/Analysis/DominatorInternals.h
new file mode 100644
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+++ b/include/llvm/Analysis/DominatorInternals.h
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+//=== llvm/Analysis/DominatorInternals.h - Dominator Calculation -*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_DOMINATOR_INTERNALS_H
+#define LLVM_ANALYSIS_DOMINATOR_INTERNALS_H
+
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/ADT/SmallPtrSet.h"
+
+//===----------------------------------------------------------------------===//
+//
+// DominatorTree construction - This pass constructs immediate dominator
+// information for a flow-graph based on the algorithm described in this
+// document:
+//
+//   A Fast Algorithm for Finding Dominators in a Flowgraph
+//   T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
+//
+// This implements both the O(n*ack(n)) and the O(n*log(n)) versions of EVAL and
+// LINK, but it turns out that the theoretically slower O(n*log(n))
+// implementation is actually faster than the "efficient" algorithm (even for
+// large CFGs) because the constant overheads are substantially smaller.  The
+// lower-complexity version can be enabled with the following #define:
+//
+#define BALANCE_IDOM_TREE 0
+//
+//===----------------------------------------------------------------------===//
+
+namespace llvm {
+
+template<class GraphT>
+unsigned DFSPass(DominatorTreeBase<typename GraphT::NodeType>& DT,
+                 typename GraphT::NodeType* V, unsigned N) {
+  // This is more understandable as a recursive algorithm, but we can't use the
+  // recursive algorithm due to stack depth issues.  Keep it here for
+  // documentation purposes.
+#if 0
+  InfoRec &VInfo = DT.Info[DT.Roots[i]];
+  VInfo.DFSNum = VInfo.Semi = ++N;
+  VInfo.Label = V;
+
+  Vertex.push_back(V);        // Vertex[n] = V;
+  //Info[V].Ancestor = 0;     // Ancestor[n] = 0
+  //Info[V].Child = 0;        // Child[v] = 0
+  VInfo.Size = 1;             // Size[v] = 1
+
+  for (succ_iterator SI = succ_begin(V), E = succ_end(V); SI != E; ++SI) {
+    InfoRec &SuccVInfo = DT.Info[*SI];
+    if (SuccVInfo.Semi == 0) {
+      SuccVInfo.Parent = V;
+      N = DTDFSPass(DT, *SI, N);
+    }
+  }
+#else
+  bool IsChilOfArtificialExit = (N != 0);
+
+  std::vector<std::pair<typename GraphT::NodeType*,
+                        typename GraphT::ChildIteratorType> > Worklist;
+  Worklist.push_back(std::make_pair(V, GraphT::child_begin(V)));
+  while (!Worklist.empty()) {
+    typename GraphT::NodeType* BB = Worklist.back().first;
+    typename GraphT::ChildIteratorType NextSucc = Worklist.back().second;
+
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &BBInfo =
+                                                                    DT.Info[BB];
+
+    // First time we visited this BB?
+    if (NextSucc == GraphT::child_begin(BB)) {
+      BBInfo.DFSNum = BBInfo.Semi = ++N;
+      BBInfo.Label = BB;
+
+      DT.Vertex.push_back(BB);       // Vertex[n] = V;
+      //BBInfo[V].Ancestor = 0;   // Ancestor[n] = 0
+      //BBInfo[V].Child = 0;      // Child[v] = 0
+      BBInfo.Size = 1;            // Size[v] = 1
+
+      if (IsChilOfArtificialExit)
+        BBInfo.Parent = 1;
+
+      IsChilOfArtificialExit = false;
+    }
+
+    // store the DFS number of the current BB - the reference to BBInfo might
+    // get invalidated when processing the successors.
+    unsigned BBDFSNum = BBInfo.DFSNum;
+
+    // If we are done with this block, remove it from the worklist.
+    if (NextSucc == GraphT::child_end(BB)) {
+      Worklist.pop_back();
+      continue;
+    }
+
+    // Increment the successor number for the next time we get to it.
+    ++Worklist.back().second;
+    
+    // Visit the successor next, if it isn't already visited.
+    typename GraphT::NodeType* Succ = *NextSucc;
+
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &SuccVInfo =
+                                                                  DT.Info[Succ];
+    if (SuccVInfo.Semi == 0) {
+      SuccVInfo.Parent = BBDFSNum;
+      Worklist.push_back(std::make_pair(Succ, GraphT::child_begin(Succ)));
+    }
+  }
+#endif
+    return N;
+}
+
+template<class GraphT>
+void Compress(DominatorTreeBase<typename GraphT::NodeType>& DT,
+              typename GraphT::NodeType *VIn) {
+  std::vector<typename GraphT::NodeType*> Work;
+  SmallPtrSet<typename GraphT::NodeType*, 32> Visited;
+  typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInVAInfo =
+                                      DT.Info[DT.Vertex[DT.Info[VIn].Ancestor]];
+
+  if (VInVAInfo.Ancestor != 0)
+    Work.push_back(VIn);
+  
+  while (!Work.empty()) {
+    typename GraphT::NodeType* V = Work.back();
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInfo =
+                                                                     DT.Info[V];
+    typename GraphT::NodeType* VAncestor = DT.Vertex[VInfo.Ancestor];
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VAInfo =
+                                                             DT.Info[VAncestor];
+
+    // Process Ancestor first
+    if (Visited.insert(VAncestor) &&
+        VAInfo.Ancestor != 0) {
+      Work.push_back(VAncestor);
+      continue;
+    } 
+    Work.pop_back(); 
+
+    // Update VInfo based on Ancestor info
+    if (VAInfo.Ancestor == 0)
+      continue;
+    typename GraphT::NodeType* VAncestorLabel = VAInfo.Label;
+    typename GraphT::NodeType* VLabel = VInfo.Label;
+    if (DT.Info[VAncestorLabel].Semi < DT.Info[VLabel].Semi)
+      VInfo.Label = VAncestorLabel;
+    VInfo.Ancestor = VAInfo.Ancestor;
+  }
+}
+
+template<class GraphT>
+typename GraphT::NodeType* Eval(DominatorTreeBase<typename GraphT::NodeType>& DT,
+                                typename GraphT::NodeType *V) {
+  typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInfo =
+                                                                     DT.Info[V];
+#if !BALANCE_IDOM_TREE
+  // Higher-complexity but faster implementation
+  if (VInfo.Ancestor == 0)
+    return V;
+  Compress<GraphT>(DT, V);
+  return VInfo.Label;
+#else
+  // Lower-complexity but slower implementation
+  if (VInfo.Ancestor == 0)
+    return VInfo.Label;
+  Compress<GraphT>(DT, V);
+  GraphT::NodeType* VLabel = VInfo.Label;
+
+  GraphT::NodeType* VAncestorLabel = DT.Info[VInfo.Ancestor].Label;
+  if (DT.Info[VAncestorLabel].Semi >= DT.Info[VLabel].Semi)
+    return VLabel;
+  else
+    return VAncestorLabel;
+#endif
+}
+
+template<class GraphT>
+void Link(DominatorTreeBase<typename GraphT::NodeType>& DT,
+          unsigned DFSNumV, typename GraphT::NodeType* W,
+        typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo) {
+#if !BALANCE_IDOM_TREE
+  // Higher-complexity but faster implementation
+  WInfo.Ancestor = DFSNumV;
+#else
+  // Lower-complexity but slower implementation
+  GraphT::NodeType* WLabel = WInfo.Label;
+  unsigned WLabelSemi = DT.Info[WLabel].Semi;
+  GraphT::NodeType* S = W;
+  InfoRec *SInfo = &DT.Info[S];
+
+  GraphT::NodeType* SChild = SInfo->Child;
+  InfoRec *SChildInfo = &DT.Info[SChild];
+
+  while (WLabelSemi < DT.Info[SChildInfo->Label].Semi) {
+    GraphT::NodeType* SChildChild = SChildInfo->Child;
+    if (SInfo->Size+DT.Info[SChildChild].Size >= 2*SChildInfo->Size) {
+      SChildInfo->Ancestor = S;
+      SInfo->Child = SChild = SChildChild;
+      SChildInfo = &DT.Info[SChild];
+    } else {
+      SChildInfo->Size = SInfo->Size;
+      S = SInfo->Ancestor = SChild;
+      SInfo = SChildInfo;
+      SChild = SChildChild;
+      SChildInfo = &DT.Info[SChild];
+    }
+  }
+
+  DominatorTreeBase::InfoRec &VInfo = DT.Info[V];
+  SInfo->Label = WLabel;
+
+  assert(V != W && "The optimization here will not work in this case!");
+  unsigned WSize = WInfo.Size;
+  unsigned VSize = (VInfo.Size += WSize);
+
+  if (VSize < 2*WSize)
+    std::swap(S, VInfo.Child);
+
+  while (S) {
+    SInfo = &DT.Info[S];
+    SInfo->Ancestor = V;
+    S = SInfo->Child;
+  }
+#endif
+}
+
+template<class FuncT, class NodeT>
+void Calculate(DominatorTreeBase<typename GraphTraits<NodeT>::NodeType>& DT,
+               FuncT& F) {
+  typedef GraphTraits<NodeT> GraphT;
+
+  unsigned N = 0;
+  bool MultipleRoots = (DT.Roots.size() > 1);
+  if (MultipleRoots) {
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &BBInfo =
+        DT.Info[NULL];
+    BBInfo.DFSNum = BBInfo.Semi = ++N;
+    BBInfo.Label = NULL;
+
+    DT.Vertex.push_back(NULL);       // Vertex[n] = V;
+      //BBInfo[V].Ancestor = 0;   // Ancestor[n] = 0
+      //BBInfo[V].Child = 0;      // Child[v] = 0
+    BBInfo.Size = 1;            // Size[v] = 1
+  }
+
+  // Step #1: Number blocks in depth-first order and initialize variables used
+  // in later stages of the algorithm.
+  for (unsigned i = 0, e = static_cast<unsigned>(DT.Roots.size());
+       i != e; ++i)
+    N = DFSPass<GraphT>(DT, DT.Roots[i], N);
+
+  // it might be that some blocks did not get a DFS number (e.g., blocks of 
+  // infinite loops). In these cases an artificial exit node is required.
+  MultipleRoots |= (DT.isPostDominator() && N != F.size());
+
+  for (unsigned i = N; i >= 2; --i) {
+    typename GraphT::NodeType* W = DT.Vertex[i];
+    typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &WInfo =
+                                                                     DT.Info[W];
+
+    // Step #2: Calculate the semidominators of all vertices
+    bool HasChildOutsideDFS = false;
+
+    // initialize the semi dominator to point to the parent node
+    WInfo.Semi = WInfo.Parent;
+    for (typename GraphTraits<Inverse<NodeT> >::ChildIteratorType CI =
+         GraphTraits<Inverse<NodeT> >::child_begin(W),
+         E = GraphTraits<Inverse<NodeT> >::child_end(W); CI != E; ++CI) {
+      if (DT.Info.count(*CI)) {  // Only if this predecessor is reachable!
+        unsigned SemiU = DT.Info[Eval<GraphT>(DT, *CI)].Semi;
+        if (SemiU < WInfo.Semi)
+          WInfo.Semi = SemiU;
+      }
+      else {
+        // if the child has no DFS number it is not post-dominated by any exit, 
+        // and so is the current block.
+        HasChildOutsideDFS = true;
+      }
+    }
+
+    // if some child has no DFS number it is not post-dominated by any exit, 
+    // and so is the current block.
+    if (DT.isPostDominator() && HasChildOutsideDFS)
+      WInfo.Semi = 0;
+
+    DT.Info[DT.Vertex[WInfo.Semi]].Bucket.push_back(W);
+
+    typename GraphT::NodeType* WParent = DT.Vertex[WInfo.Parent];
+    Link<GraphT>(DT, WInfo.Parent, W, WInfo);
+
+    // Step #3: Implicitly define the immediate dominator of vertices
+    std::vector<typename GraphT::NodeType*> &WParentBucket =
+                                                        DT.Info[WParent].Bucket;
+    while (!WParentBucket.empty()) {
+      typename GraphT::NodeType* V = WParentBucket.back();
+      WParentBucket.pop_back();
+      typename GraphT::NodeType* U = Eval<GraphT>(DT, V);
+      DT.IDoms[V] = DT.Info[U].Semi < DT.Info[V].Semi ? U : WParent;
+    }
+  }
+
+  // Step #4: Explicitly define the immediate dominator of each vertex
+  for (unsigned i = 2; i <= N; ++i) {
+    typename GraphT::NodeType* W = DT.Vertex[i];
+    typename GraphT::NodeType*& WIDom = DT.IDoms[W];
+    if (WIDom != DT.Vertex[DT.Info[W].Semi])
+      WIDom = DT.IDoms[WIDom];
+  }
+
+  if (DT.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, or
+  // an infinite loop.
+  typename GraphT::NodeType* Root = !MultipleRoots ? DT.Roots[0] : 0;
+
+  DT.DomTreeNodes[Root] = DT.RootNode =
+                        new DomTreeNodeBase<typename GraphT::NodeType>(Root, 0);
+
+  // Loop over all of the reachable blocks in the function...
+  for (unsigned i = 2; i <= N; ++i) {
+    typename GraphT::NodeType* W = DT.Vertex[i];
+
+    DomTreeNodeBase<typename GraphT::NodeType> *BBNode = DT.DomTreeNodes[W];
+    if (BBNode) continue;  // Haven't calculated this node yet?
+
+    typename GraphT::NodeType* ImmDom = DT.getIDom(W);
+
+    assert(ImmDom || DT.DomTreeNodes[NULL]);
+
+    // Get or calculate the node for the immediate dominator
+    DomTreeNodeBase<typename GraphT::NodeType> *IDomNode =
+                                                     DT.getNodeForBlock(ImmDom);
+
+    // Add a new tree node for this BasicBlock, and link it as a child of
+    // IDomNode
+    DomTreeNodeBase<typename GraphT::NodeType> *C =
+                    new DomTreeNodeBase<typename GraphT::NodeType>(W, IDomNode);
+    DT.DomTreeNodes[W] = IDomNode->addChild(C);
+  }
+
+  // Free temporary memory used to construct idom's
+  DT.IDoms.clear();
+  DT.Info.clear();
+  std::vector<typename GraphT::NodeType*>().swap(DT.Vertex);
+  
+  // FIXME: This does not work on PostDomTrees.  It seems likely that this is
+  // due to an error in the algorithm for post-dominators.  This really should
+  // be investigated and fixed at some point.
+  // DT.updateDFSNumbers();
+
+  // Start out with the DFS numbers being invalid.  Let them be computed if
+  // demanded.
+  DT.DFSInfoValid = false;
+}
+
+}
+
+#endif