+++ /dev/null
-//=== 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/ADT/SmallPtrSet.h"
-#include "llvm/Analysis/Dominators.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 the O(n*log(n)) versions of EVAL and LINK, because it turns
-// out that the theoretically slower O(n*log(n)) implementation is actually
-// faster than the almost-linear O(n*alpha(n)) version, even for large CFGs.
-//
-//===----------------------------------------------------------------------===//
-
-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;
-
- 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 IsChildOfArtificialExit = (N != 0);
-
- SmallVector<std::pair<typename GraphT::NodeType*,
- typename GraphT::ChildIteratorType>, 32> 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;
-
- if (IsChildOfArtificialExit)
- BBInfo.Parent = 1;
-
- IsChildOfArtificialExit = 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>
-typename GraphT::NodeType*
-Eval(DominatorTreeBase<typename GraphT::NodeType>& DT,
- typename GraphT::NodeType *VIn, unsigned LastLinked) {
- typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VInInfo =
- DT.Info[VIn];
- if (VInInfo.DFSNum < LastLinked)
- return VIn;
-
- SmallVector<typename GraphT::NodeType*, 32> Work;
- SmallPtrSet<typename GraphT::NodeType*, 32> Visited;
-
- if (VInInfo.Parent >= LastLinked)
- 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.Parent];
-
- // Process Ancestor first
- if (Visited.insert(VAncestor) && VInfo.Parent >= LastLinked) {
- Work.push_back(VAncestor);
- continue;
- }
- Work.pop_back();
-
- // Update VInfo based on Ancestor info
- if (VInfo.Parent < LastLinked)
- continue;
-
- typename DominatorTreeBase<typename GraphT::NodeType>::InfoRec &VAInfo =
- DT.Info[VAncestor];
- 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.Parent = VAInfo.Parent;
- }
-
- return VInInfo.Label;
-}
-
-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;
- }
-
- // 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 != GraphTraits<FuncT*>::size(&F));
-
- // When naively implemented, the Lengauer-Tarjan algorithm requires a separate
- // bucket for each vertex. However, this is unnecessary, because each vertex
- // is only placed into a single bucket (that of its semidominator), and each
- // vertex's bucket is processed before it is added to any bucket itself.
- //
- // Instead of using a bucket per vertex, we use a single array Buckets that
- // has two purposes. Before the vertex V with preorder number i is processed,
- // Buckets[i] stores the index of the first element in V's bucket. After V's
- // bucket is processed, Buckets[i] stores the index of the next element in the
- // bucket containing V, if any.
- SmallVector<unsigned, 32> Buckets;
- Buckets.resize(N + 1);
- for (unsigned i = 1; i <= N; ++i)
- Buckets[i] = i;
-
- 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: Implicitly define the immediate dominator of vertices
- for (unsigned j = i; Buckets[j] != i; j = Buckets[j]) {
- typename GraphT::NodeType* V = DT.Vertex[Buckets[j]];
- typename GraphT::NodeType* U = Eval<GraphT>(DT, V, i + 1);
- DT.IDoms[V] = DT.Info[U].Semi < i ? U : W;
- }
-
- // Step #3: Calculate the semidominators of all vertices
-
- // initialize the semi dominator to point to the parent node
- WInfo.Semi = WInfo.Parent;
- typedef GraphTraits<Inverse<NodeT> > InvTraits;
- for (typename InvTraits::ChildIteratorType CI =
- InvTraits::child_begin(W),
- E = InvTraits::child_end(W); CI != E; ++CI) {
- typename InvTraits::NodeType *N = *CI;
- if (DT.Info.count(N)) { // Only if this predecessor is reachable!
- unsigned SemiU = DT.Info[Eval<GraphT>(DT, N, i + 1)].Semi;
- if (SemiU < WInfo.Semi)
- WInfo.Semi = SemiU;
- }
- }
-
- // If V is a non-root vertex and sdom(V) = parent(V), then idom(V) is
- // necessarily parent(V). In this case, set idom(V) here and avoid placing
- // V into a bucket.
- if (WInfo.Semi == WInfo.Parent) {
- DT.IDoms[W] = DT.Vertex[WInfo.Parent];
- } else {
- Buckets[i] = Buckets[WInfo.Semi];
- Buckets[WInfo.Semi] = i;
- }
- }
-
- if (N >= 1) {
- typename GraphT::NodeType* Root = DT.Vertex[1];
- for (unsigned j = 1; Buckets[j] != 1; j = Buckets[j]) {
- typename GraphT::NodeType* V = DT.Vertex[Buckets[j]];
- DT.IDoms[V] = Root;
- }
- }
-
- // 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);
-
- DT.updateDFSNumbers();
-}
-
-}
-
-#endif
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