-//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
+//===- Dominators.cpp - Dominator Calculation -----------------------------===//
//
-// This file provides a simple class to calculate the dominator set of a
-// function.
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements simple dominator construction algorithms for finding
+// forward dominators. Postdominators are available in libanalysis, but are not
+// included in libvmcore, because it's not needed. Forward dominators are
+// needed to support the Verifier pass.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/Dominators.h"
-#include "llvm/Transforms/Scalar/UnifyFunctionExitNodes.h"
#include "llvm/Support/CFG.h"
-#include "Support/DepthFirstIterator.h"
-#include "Support/STLExtras.h"
-#include "Support/SetOperations.h"
+#include "llvm/Assembly/Writer.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SetOperations.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Instructions.h"
+#include "llvm/Support/Streams.h"
#include <algorithm>
-using std::set;
+using namespace llvm;
+
+namespace llvm {
+static std::ostream &operator<<(std::ostream &o,
+ const std::set<BasicBlock*> &BBs) {
+ for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
+ I != E; ++I)
+ if (*I)
+ WriteAsOperand(o, *I, false);
+ else
+ o << " <<exit node>>";
+ return o;
+}
+}
//===----------------------------------------------------------------------===//
-// DominatorSet Implementation
+// DominatorTree Implementation
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
//===----------------------------------------------------------------------===//
-AnalysisID DominatorSet::ID(AnalysisID::create<DominatorSet>(), true);
-AnalysisID DominatorSet::PostDomID(AnalysisID::create<DominatorSet>(), true);
+char DominatorTree::ID = 0;
+static RegisterPass<DominatorTree>
+E("domtree", "Dominator Tree Construction", true);
-bool DominatorSet::runOnFunction(Function *F) {
- Doms.clear(); // Reset from the last time we were run...
+// NewBB is split and now it has one successor. Update dominator tree to
+// reflect this change.
+void DominatorTree::splitBlock(BasicBlock *NewBB) {
- if (isPostDominator())
- calcPostDominatorSet(F);
- else
- calcForwardDominatorSet(F);
- return false;
-}
+ assert(NewBB->getTerminator()->getNumSuccessors() == 1
+ && "NewBB should have a single successor!");
+ BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
+ std::vector<BasicBlock*> PredBlocks;
+ for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
+ PI != PE; ++PI)
+ PredBlocks.push_back(*PI);
-// calcForwardDominatorSet - This method calculates the forward dominator sets
-// for the specified function.
-//
-void DominatorSet::calcForwardDominatorSet(Function *M) {
- Root = M->getEntryNode();
- assert(pred_begin(Root) == pred_end(Root) &&
- "Root node has predecessors in function!");
+ assert(!PredBlocks.empty() && "No predblocks??");
- bool Changed;
- do {
- Changed = false;
-
- DomSetType WorkingSet;
- df_iterator<Function*> It = df_begin(M), End = df_end(M);
- for ( ; It != End; ++It) {
- BasicBlock *BB = *It;
- pred_iterator PI = pred_begin(BB), PEnd = pred_end(BB);
- if (PI != PEnd) { // Is there SOME predecessor?
- // Loop until we get to a predecessor that has had it's dom set filled
- // in at least once. We are guaranteed to have this because we are
- // traversing the graph in DFO and have handled start nodes specially.
- //
- while (Doms[*PI].size() == 0) ++PI;
- WorkingSet = Doms[*PI];
-
- for (++PI; PI != PEnd; ++PI) { // Intersect all of the predecessor sets
- DomSetType &PredSet = Doms[*PI];
- if (PredSet.size())
- set_intersect(WorkingSet, PredSet);
- }
+ // The newly inserted basic block will dominate existing basic blocks iff the
+ // PredBlocks dominate all of the non-pred blocks. If all predblocks dominate
+ // the non-pred blocks, then they all must be the same block!
+ //
+ bool NewBBDominatesNewBBSucc = true;
+ {
+ BasicBlock *OnePred = PredBlocks[0];
+ unsigned i = 1, e = PredBlocks.size();
+ for (i = 1; !isReachableFromEntry(OnePred); ++i) {
+ assert(i != e && "Didn't find reachable pred?");
+ OnePred = PredBlocks[i];
+ }
+
+ for (; i != e; ++i)
+ if (PredBlocks[i] != OnePred && isReachableFromEntry(OnePred)){
+ NewBBDominatesNewBBSucc = false;
+ break;
}
-
- WorkingSet.insert(BB); // A block always dominates itself
- DomSetType &BBSet = Doms[BB];
- if (BBSet != WorkingSet) {
- BBSet.swap(WorkingSet); // Constant time operation!
- Changed = true; // The sets changed.
+
+ if (NewBBDominatesNewBBSucc)
+ for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
+ PI != E; ++PI)
+ if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
+ NewBBDominatesNewBBSucc = false;
+ break;
+ }
+ }
+
+ // The other scenario where the new block can dominate its successors are when
+ // all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
+ // already.
+ if (!NewBBDominatesNewBBSucc) {
+ NewBBDominatesNewBBSucc = true;
+ for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
+ PI != E; ++PI)
+ if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
+ NewBBDominatesNewBBSucc = false;
+ break;
}
- WorkingSet.clear(); // Clear out the set for next iteration
+ }
+
+
+ // Find NewBB's immediate dominator and create new dominator tree node for NewBB.
+ BasicBlock *NewBBIDom = 0;
+ unsigned i = 0;
+ for (i = 0; i < PredBlocks.size(); ++i)
+ if (isReachableFromEntry(PredBlocks[i])) {
+ NewBBIDom = PredBlocks[i];
+ break;
}
- } while (Changed);
+ assert(i != PredBlocks.size() && "No reachable preds?");
+ for (i = i + 1; i < PredBlocks.size(); ++i) {
+ if (isReachableFromEntry(PredBlocks[i]))
+ NewBBIDom = findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
+ }
+ assert(NewBBIDom && "No immediate dominator found??");
+
+ // Create the new dominator tree node... and set the idom of NewBB.
+ DomTreeNode *NewBBNode = addNewBlock(NewBB, NewBBIDom);
+
+ // If NewBB strictly dominates other blocks, then it is now the immediate
+ // dominator of NewBBSucc. Update the dominator tree as appropriate.
+ if (NewBBDominatesNewBBSucc) {
+ DomTreeNode *NewBBSuccNode = getNode(NewBBSucc);
+ changeImmediateDominator(NewBBSuccNode, NewBBNode);
+ }
}
-// Postdominator set constructor. This ctor converts the specified function to
-// only have a single exit node (return stmt), then calculates the post
-// dominance sets for the function.
-//
-void DominatorSet::calcPostDominatorSet(Function *F) {
- // Since we require that the unify all exit nodes pass has been run, we know
- // that there can be at most one return instruction in the function left.
- // Get it.
- //
- Root = getAnalysis<UnifyFunctionExitNodes>().getExitNode();
+unsigned DominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
+ 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
+ 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 = Info[*SI];
+ if (SuccVInfo.Semi == 0) {
+ SuccVInfo.Parent = V;
+ N = DFSPass(*SI, SuccVInfo, N);
+ }
+ }
+#else
+ std::vector<std::pair<BasicBlock*, unsigned> > Worklist;
+ Worklist.push_back(std::make_pair(V, 0U));
+ while (!Worklist.empty()) {
+ BasicBlock *BB = Worklist.back().first;
+ unsigned NextSucc = Worklist.back().second;
+
+ // First time we visited this BB?
+ if (NextSucc == 0) {
+ InfoRec &BBInfo = Info[BB];
+ BBInfo.Semi = ++N;
+ BBInfo.Label = BB;
+
+ 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 we are done with this block, remove it from the worklist.
+ if (NextSucc == BB->getTerminator()->getNumSuccessors()) {
+ Worklist.pop_back();
+ continue;
+ }
+
+ // Otherwise, 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.
+ BasicBlock *Succ = BB->getTerminator()->getSuccessor(NextSucc);
+
+ InfoRec &SuccVInfo = Info[Succ];
+ if (SuccVInfo.Semi == 0) {
+ SuccVInfo.Parent = BB;
+ Worklist.push_back(std::make_pair(Succ, 0U));
+ }
+ }
+#endif
+ return N;
+}
- if (Root == 0) { // No exit node for the function? Postdomsets are all empty
- for (Function::iterator FI = F->begin(), FE = F->end(); FI != FE; ++FI)
- Doms[*FI] = DomSetType();
- return;
+void DominatorTree::Compress(BasicBlock *VIn) {
+
+ std::vector<BasicBlock *> Work;
+ std::set<BasicBlock *> Visited;
+ InfoRec &VInInfo = Info[VIn];
+ BasicBlock *VInAncestor = VInInfo.Ancestor;
+ InfoRec &VInVAInfo = Info[VInAncestor];
+
+ if (VInVAInfo.Ancestor != 0)
+ Work.push_back(VIn);
+
+ while (!Work.empty()) {
+ BasicBlock *V = Work.back();
+ InfoRec &VInfo = Info[V];
+ BasicBlock *VAncestor = VInfo.Ancestor;
+ InfoRec &VAInfo = Info[VAncestor];
+
+ // Process Ancestor first
+ if (Visited.count(VAncestor) == 0 && VAInfo.Ancestor != 0) {
+ Work.push_back(VAncestor);
+ Visited.insert(VAncestor);
+ continue;
+ }
+ Work.pop_back();
+
+ // Update VINfo based on Ancestor info
+ if (VAInfo.Ancestor == 0)
+ continue;
+ BasicBlock *VAncestorLabel = VAInfo.Label;
+ BasicBlock *VLabel = VInfo.Label;
+ if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
+ VInfo.Label = VAncestorLabel;
+ VInfo.Ancestor = VAInfo.Ancestor;
}
+}
- bool Changed;
- do {
- Changed = false;
-
- set<const BasicBlock*> Visited;
- DomSetType WorkingSet;
- idf_iterator<BasicBlock*> It = idf_begin(Root), End = idf_end(Root);
- for ( ; It != End; ++It) {
- BasicBlock *BB = *It;
- succ_iterator PI = succ_begin(BB), PEnd = succ_end(BB);
- if (PI != PEnd) { // Is there SOME predecessor?
- // Loop until we get to a successor that has had it's dom set filled
- // in at least once. We are guaranteed to have this because we are
- // traversing the graph in DFO and have handled start nodes specially.
- //
- while (Doms[*PI].size() == 0) ++PI;
- WorkingSet = Doms[*PI];
-
- for (++PI; PI != PEnd; ++PI) { // Intersect all of the successor sets
- DomSetType &PredSet = Doms[*PI];
- if (PredSet.size())
- set_intersect(WorkingSet, PredSet);
- }
- }
-
- WorkingSet.insert(BB); // A block always dominates itself
- DomSetType &BBSet = Doms[BB];
- if (BBSet != WorkingSet) {
- BBSet.swap(WorkingSet); // Constant time operation!
- Changed = true; // The sets changed.
- }
- WorkingSet.clear(); // Clear out the set for next iteration
- }
- } while (Changed);
+BasicBlock *DominatorTree::Eval(BasicBlock *V) {
+ InfoRec &VInfo = Info[V];
+#if !BALANCE_IDOM_TREE
+ // Higher-complexity but faster implementation
+ if (VInfo.Ancestor == 0)
+ return V;
+ Compress(V);
+ return VInfo.Label;
+#else
+ // Lower-complexity but slower implementation
+ if (VInfo.Ancestor == 0)
+ return VInfo.Label;
+ Compress(V);
+ BasicBlock *VLabel = VInfo.Label;
+
+ BasicBlock *VAncestorLabel = Info[VInfo.Ancestor].Label;
+ if (Info[VAncestorLabel].Semi >= Info[VLabel].Semi)
+ return VLabel;
+ else
+ return VAncestorLabel;
+#endif
}
-// getAnalysisUsage - This obviously provides a dominator set, but it also
-// uses the UnifyFunctionExitNodes pass if building post-dominators
-//
-void DominatorSet::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesAll();
- if (isPostDominator()) {
- AU.addProvided(PostDomID);
- AU.addRequired(UnifyFunctionExitNodes::ID);
- } else {
- AU.addProvided(ID);
+void DominatorTree::Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo){
+#if !BALANCE_IDOM_TREE
+ // Higher-complexity but faster implementation
+ WInfo.Ancestor = V;
+#else
+ // Lower-complexity but slower implementation
+ BasicBlock *WLabel = WInfo.Label;
+ unsigned WLabelSemi = Info[WLabel].Semi;
+ BasicBlock *S = W;
+ InfoRec *SInfo = &Info[S];
+
+ BasicBlock *SChild = SInfo->Child;
+ InfoRec *SChildInfo = &Info[SChild];
+
+ while (WLabelSemi < Info[SChildInfo->Label].Semi) {
+ BasicBlock *SChildChild = SChildInfo->Child;
+ if (SInfo->Size+Info[SChildChild].Size >= 2*SChildInfo->Size) {
+ SChildInfo->Ancestor = S;
+ SInfo->Child = SChild = SChildChild;
+ SChildInfo = &Info[SChild];
+ } else {
+ SChildInfo->Size = SInfo->Size;
+ S = SInfo->Ancestor = SChild;
+ SInfo = SChildInfo;
+ SChild = SChildChild;
+ SChildInfo = &Info[SChild];
+ }
}
+
+ InfoRec &VInfo = 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 = &Info[S];
+ SInfo->Ancestor = V;
+ S = SInfo->Child;
+ }
+#endif
}
+void DominatorTree::calculate(Function& F) {
+ BasicBlock* Root = Roots[0];
-//===----------------------------------------------------------------------===//
-// ImmediateDominators Implementation
-//===----------------------------------------------------------------------===//
+ // Add a node for the root...
+ DomTreeNodes[Root] = RootNode = new DomTreeNode(Root, 0);
-AnalysisID ImmediateDominators::ID(AnalysisID::create<ImmediateDominators>(), true);
-AnalysisID ImmediateDominators::PostDomID(AnalysisID::create<ImmediateDominators>(), true);
+ Vertex.push_back(0);
-// calcIDoms - Calculate the immediate dominator mapping, given a set of
-// dominators for every basic block.
-void ImmediateDominators::calcIDoms(const DominatorSet &DS) {
- // Loop over all of the nodes that have dominators... figuring out the IDOM
- // for each node...
- //
- for (DominatorSet::const_iterator DI = DS.begin(), DEnd = DS.end();
- DI != DEnd; ++DI) {
- BasicBlock *BB = DI->first;
- const DominatorSet::DomSetType &Dominators = DI->second;
- unsigned DomSetSize = Dominators.size();
- if (DomSetSize == 1) continue; // Root node... IDom = null
-
- // Loop over all dominators of this node. This corresponds to looping over
- // nodes in the dominator chain, looking for a node whose dominator set is
- // equal to the current nodes, except that the current node does not exist
- // in it. This means that it is one level higher in the dom chain than the
- // current node, and it is our idom!
- //
- DominatorSet::DomSetType::const_iterator I = Dominators.begin();
- DominatorSet::DomSetType::const_iterator End = Dominators.end();
- for (; I != End; ++I) { // Iterate over dominators...
- // All of our dominators should form a chain, where the number of elements
- // in the dominator set indicates what level the node is at in the chain.
- // We want the node immediately above us, so it will have an identical
- // dominator set, except that BB will not dominate it... therefore it's
- // dominator set size will be one less than BB's...
- //
- if (DS.getDominators(*I).size() == DomSetSize - 1) {
- IDoms[BB] = *I;
- break;
+ // Step #1: Number blocks in depth-first order and initialize variables used
+ // in later stages of the algorithm.
+ unsigned N = 0;
+ for (unsigned i = 0, e = Roots.size(); i != e; ++i)
+ N = DFSPass(Roots[i], Info[Roots[i]], 0);
+
+ for (unsigned i = N; i >= 2; --i) {
+ BasicBlock *W = Vertex[i];
+ InfoRec &WInfo = Info[W];
+
+ // Step #2: Calculate the semidominators of all vertices
+ for (pred_iterator PI = pred_begin(W), E = pred_end(W); PI != E; ++PI)
+ if (Info.count(*PI)) { // Only if this predecessor is reachable!
+ unsigned SemiU = Info[Eval(*PI)].Semi;
+ if (SemiU < WInfo.Semi)
+ WInfo.Semi = SemiU;
}
+
+ Info[Vertex[WInfo.Semi]].Bucket.push_back(W);
+
+ BasicBlock *WParent = WInfo.Parent;
+ Link(WParent, W, WInfo);
+
+ // Step #3: Implicitly define the immediate dominator of vertices
+ std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
+ while (!WParentBucket.empty()) {
+ BasicBlock *V = WParentBucket.back();
+ WParentBucket.pop_back();
+ BasicBlock *U = Eval(V);
+ IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
}
}
+
+ // Step #4: Explicitly define the immediate dominator of each vertex
+ for (unsigned i = 2; i <= N; ++i) {
+ BasicBlock *W = Vertex[i];
+ BasicBlock *&WIDom = IDoms[W];
+ if (WIDom != Vertex[Info[W].Semi])
+ WIDom = IDoms[WIDom];
+ }
+
+ // Loop over all of the reachable blocks in the function...
+ for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
+ if (BasicBlock *ImmDom = getIDom(I)) { // Reachable block.
+ DomTreeNode *&BBNode = DomTreeNodes[I];
+ if (!BBNode) { // Haven't calculated this node yet?
+ // Get or calculate the node for the immediate dominator
+ DomTreeNode *IDomNode = getNodeForBlock(ImmDom);
+
+ // Add a new tree node for this BasicBlock, and link it as a child of
+ // IDomNode
+ DomTreeNode *C = new DomTreeNode(I, IDomNode);
+ DomTreeNodes[I] = C;
+ BBNode = IDomNode->addChild(C);
+ }
+ }
+
+ // Free temporary memory used to construct idom's
+ Info.clear();
+ IDoms.clear();
+ std::vector<BasicBlock*>().swap(Vertex);
+
+ updateDFSNumbers();
}
+void DominatorTreeBase::updateDFSNumbers()
+{
+ int dfsnum = 0;
+ // Iterate over all nodes in depth first order.
+ for (unsigned i = 0, e = Roots.size(); i != e; ++i)
+ for (df_iterator<BasicBlock*> I = df_begin(Roots[i]),
+ E = df_end(Roots[i]); I != E; ++I) {
+ BasicBlock *BB = *I;
+ DomTreeNode *BBNode = getNode(BB);
+ if (BBNode) {
+ if (!BBNode->getIDom())
+ BBNode->assignDFSNumber(dfsnum);
+ }
+ }
+ SlowQueries = 0;
+ DFSInfoValid = true;
+}
-//===----------------------------------------------------------------------===//
-// DominatorTree Implementation
-//===----------------------------------------------------------------------===//
+/// isReachableFromEntry - Return true if A is dominated by the entry
+/// block of the function containing it.
+const bool DominatorTreeBase::isReachableFromEntry(BasicBlock* A) {
+ assert (!isPostDominator()
+ && "This is not implemented for post dominators");
+ return dominates(&A->getParent()->getEntryBlock(), A);
+}
-AnalysisID DominatorTree::ID(AnalysisID::create<DominatorTree>(), true);
-AnalysisID DominatorTree::PostDomID(AnalysisID::create<DominatorTree>(), true);
+// dominates - Return true if A dominates B. THis performs the
+// special checks necessary if A and B are in the same basic block.
+bool DominatorTreeBase::dominates(Instruction *A, Instruction *B) {
+ BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
+ if (BBA != BBB) return dominates(BBA, BBB);
+
+ // It is not possible to determine dominance between two PHI nodes
+ // based on their ordering.
+ if (isa<PHINode>(A) && isa<PHINode>(B))
+ return false;
+
+ // Loop through the basic block until we find A or B.
+ BasicBlock::iterator I = BBA->begin();
+ for (; &*I != A && &*I != B; ++I) /*empty*/;
+
+ if(!IsPostDominators) {
+ // A dominates B if it is found first in the basic block.
+ return &*I == A;
+ } else {
+ // A post-dominates B if B is found first in the basic block.
+ return &*I == B;
+ }
+}
-// DominatorTree::reset - Free all of the tree node memory.
+// DominatorTreeBase::reset - Free all of the tree node memory.
//
-void DominatorTree::reset() {
- for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
+void DominatorTreeBase::reset() {
+ for (DomTreeNodeMapType::iterator I = DomTreeNodes.begin(),
+ E = DomTreeNodes.end(); I != E; ++I)
delete I->second;
- Nodes.clear();
+ DomTreeNodes.clear();
+ IDoms.clear();
+ Roots.clear();
+ Vertex.clear();
+ RootNode = 0;
}
+/// findNearestCommonDominator - Find nearest common dominator basic block
+/// for basic block A and B. If there is no such block then return NULL.
+BasicBlock *DominatorTreeBase::findNearestCommonDominator(BasicBlock *A,
+ BasicBlock *B) {
+
+ assert (!isPostDominator()
+ && "This is not implemented for post dominators");
+ assert (A->getParent() == B->getParent()
+ && "Two blocks are not in same function");
+
+ // If either A or B is a entry block then it is nearest common dominator.
+ BasicBlock &Entry = A->getParent()->getEntryBlock();
+ if (A == &Entry || B == &Entry)
+ return &Entry;
+
+ // If B dominates A then B is nearest common dominator.
+ if (dominates(B,A))
+ return B;
+
+ // If A dominates B then A is nearest common dominator.
+ if (dominates(A,B))
+ return A;
+
+ DomTreeNode *NodeA = getNode(A);
+ DomTreeNode *NodeB = getNode(B);
+
+ // Collect NodeA dominators set.
+ SmallPtrSet<DomTreeNode*, 16> NodeADoms;
+ NodeADoms.insert(NodeA);
+ DomTreeNode *IDomA = NodeA->getIDom();
+ while(IDomA) {
+ NodeADoms.insert(IDomA);
+ IDomA = IDomA->getIDom();
+ }
-#if 0
-// Given immediate dominators, we can also calculate the dominator tree
-DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
- : DominatorBase(IDoms.getRoot()) {
- const Function *M = Root->getParent();
-
- Nodes[Root] = new Node(Root, 0); // Add a node for the root...
-
- // Iterate over all nodes in depth first order...
- for (df_iterator<const Function*> I = df_begin(M), E = df_end(M); I!=E; ++I) {
- const BasicBlock *BB = *I, *IDom = IDoms[*I];
-
- if (IDom != 0) { // Ignore the root node and other nasty nodes
- // We know that the immediate dominator should already have a node,
- // because we are traversing the CFG in depth first order!
- //
- assert(Nodes[IDom] && "No node for IDOM?");
- Node *IDomNode = Nodes[IDom];
-
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
- }
+ // Walk NodeB immediate dominators chain and find common dominator node.
+ DomTreeNode *IDomB = NodeB->getIDom();
+ while(IDomB) {
+ if (NodeADoms.count(IDomB) != 0)
+ return IDomB->getBlock();
+
+ IDomB = IDomB->getIDom();
}
-}
-#endif
-void DominatorTree::calculate(const DominatorSet &DS) {
- Nodes[Root] = new Node(Root, 0); // Add a node for the root...
+ return NULL;
+}
- if (!isPostDominator()) {
- // Iterate over all nodes in depth first order...
- for (df_iterator<BasicBlock*> I = df_begin(Root), E = df_end(Root);
- I != E; ++I) {
- BasicBlock *BB = *I;
- const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
- unsigned DomSetSize = Dominators.size();
- if (DomSetSize == 1) continue; // Root node... IDom = null
-
- // Loop over all dominators of this node. This corresponds to looping over
- // nodes in the dominator chain, looking for a node whose dominator set is
- // equal to the current nodes, except that the current node does not exist
- // in it. This means that it is one level higher in the dom chain than the
- // current node, and it is our idom! We know that we have already added
- // a DominatorTree node for our idom, because the idom must be a
- // predecessor in the depth first order that we are iterating through the
- // function.
- //
- DominatorSet::DomSetType::const_iterator I = Dominators.begin();
- DominatorSet::DomSetType::const_iterator End = Dominators.end();
- for (; I != End; ++I) { // Iterate over dominators...
- // All of our dominators should form a chain, where the number of
- // elements in the dominator set indicates what level the node is at in
- // the chain. We want the node immediately above us, so it will have
- // an identical dominator set, except that BB will not dominate it...
- // therefore it's dominator set size will be one less than BB's...
- //
- if (DS.getDominators(*I).size() == DomSetSize - 1) {
- // We know that the immediate dominator should already have a node,
- // because we are traversing the CFG in depth first order!
- //
- Node *IDomNode = Nodes[*I];
- assert(IDomNode && "No node for IDOM?");
-
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
- break;
- }
+/// assignDFSNumber - Assign In and Out numbers while walking dominator tree
+/// in dfs order.
+void DomTreeNode::assignDFSNumber(int num) {
+ std::vector<DomTreeNode *> workStack;
+ std::set<DomTreeNode *> visitedNodes;
+
+ workStack.push_back(this);
+ visitedNodes.insert(this);
+ this->DFSNumIn = num++;
+
+ while (!workStack.empty()) {
+ DomTreeNode *Node = workStack.back();
+
+ bool visitChild = false;
+ for (std::vector<DomTreeNode*>::iterator DI = Node->begin(),
+ E = Node->end(); DI != E && !visitChild; ++DI) {
+ DomTreeNode *Child = *DI;
+ if (visitedNodes.count(Child) == 0) {
+ visitChild = true;
+ Child->DFSNumIn = num++;
+ workStack.push_back(Child);
+ visitedNodes.insert(Child);
}
}
- } else if (Root) {
- // Iterate over all nodes in depth first order...
- for (idf_iterator<BasicBlock*> I = idf_begin(Root), E = idf_end(Root);
- I != E; ++I) {
- BasicBlock *BB = *I;
- const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
- unsigned DomSetSize = Dominators.size();
- if (DomSetSize == 1) continue; // Root node... IDom = null
-
- // Loop over all dominators of this node. This corresponds to looping
- // over nodes in the dominator chain, looking for a node whose dominator
- // set is equal to the current nodes, except that the current node does
- // not exist in it. This means that it is one level higher in the dom
- // chain than the current node, and it is our idom! We know that we have
- // already added a DominatorTree node for our idom, because the idom must
- // be a predecessor in the depth first order that we are iterating through
- // the function.
- //
- DominatorSet::DomSetType::const_iterator I = Dominators.begin();
- DominatorSet::DomSetType::const_iterator End = Dominators.end();
- for (; I != End; ++I) { // Iterate over dominators...
- // All of our dominators should form a chain, where the number
- // of elements in the dominator set indicates what level the
- // node is at in the chain. We want the node immediately
- // above us, so it will have an identical dominator set,
- // except that BB will not dominate it... therefore it's
- // dominator set size will be one less than BB's...
- //
- if (DS.getDominators(*I).size() == DomSetSize - 1) {
- // We know that the immediate dominator should already have a node,
- // because we are traversing the CFG in depth first order!
- //
- Node *IDomNode = Nodes[*I];
- assert(IDomNode && "No node for IDOM?");
-
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
- break;
- }
- }
+ if (!visitChild) {
+ // If we reach here means all children are visited
+ Node->DFSNumOut = num++;
+ workStack.pop_back();
}
}
}
+void DomTreeNode::setIDom(DomTreeNode *NewIDom) {
+ assert(IDom && "No immediate dominator?");
+ if (IDom != NewIDom) {
+ std::vector<DomTreeNode*>::iterator I =
+ std::find(IDom->Children.begin(), IDom->Children.end(), this);
+ assert(I != IDom->Children.end() &&
+ "Not in immediate dominator children set!");
+ // I am no longer your child...
+ IDom->Children.erase(I);
+
+ // Switch to new dominator
+ IDom = NewIDom;
+ IDom->Children.push_back(this);
+ }
+}
+
+DomTreeNode *DominatorTree::getNodeForBlock(BasicBlock *BB) {
+ DomTreeNode *&BBNode = DomTreeNodes[BB];
+ if (BBNode) return BBNode;
+
+ // Haven't calculated this node yet? Get or calculate the node for the
+ // immediate dominator.
+ BasicBlock *IDom = getIDom(BB);
+ DomTreeNode *IDomNode = getNodeForBlock(IDom);
+
+ // Add a new tree node for this BasicBlock, and link it as a child of
+ // IDomNode
+ DomTreeNode *C = new DomTreeNode(BB, IDomNode);
+ DomTreeNodes[BB] = C;
+ return BBNode = IDomNode->addChild(C);
+}
+
+static std::ostream &operator<<(std::ostream &o,
+ const DomTreeNode *Node) {
+ if (Node->getBlock())
+ WriteAsOperand(o, Node->getBlock(), false);
+ else
+ o << " <<exit node>>";
+ return o << "\n";
+}
+
+static void PrintDomTree(const DomTreeNode *N, std::ostream &o,
+ unsigned Lev) {
+ o << std::string(2*Lev, ' ') << "[" << Lev << "] " << N;
+ for (DomTreeNode::const_iterator I = N->begin(), E = N->end();
+ I != E; ++I)
+ PrintDomTree(*I, o, Lev+1);
+}
+
+void DominatorTreeBase::print(std::ostream &o, const Module* ) const {
+ o << "=============================--------------------------------\n"
+ << "Inorder Dominator Tree:\n";
+ PrintDomTree(getRootNode(), o, 1);
+}
+
+void DominatorTreeBase::dump() {
+ print (llvm::cerr);
+}
+bool DominatorTree::runOnFunction(Function &F) {
+ reset(); // Reset from the last time we were run...
+ Roots.push_back(&F.getEntryBlock());
+ calculate(F);
+ return false;
+}
//===----------------------------------------------------------------------===//
// DominanceFrontier Implementation
//===----------------------------------------------------------------------===//
-AnalysisID DominanceFrontier::ID(AnalysisID::create<DominanceFrontier>(), true);
-AnalysisID DominanceFrontier::PostDomID(AnalysisID::create<DominanceFrontier>(), true);
-
-const DominanceFrontier::DomSetType &
-DominanceFrontier::calcDomFrontier(const DominatorTree &DT,
- const DominatorTree::Node *Node) {
- // Loop over CFG successors to calculate DFlocal[Node]
- BasicBlock *BB = Node->getNode();
- DomSetType &S = Frontiers[BB]; // The new set to fill in...
-
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
- SI != SE; ++SI) {
- // Does Node immediately dominate this successor?
- if (DT[*SI]->getIDom() != Node)
- S.insert(*SI);
+char DominanceFrontier::ID = 0;
+static RegisterPass<DominanceFrontier>
+G("domfrontier", "Dominance Frontier Construction", true);
+
+// NewBB is split and now it has one successor. Update dominace frontier to
+// reflect this change.
+void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
+
+ assert(NewBB->getTerminator()->getNumSuccessors() == 1
+ && "NewBB should have a single successor!");
+ BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
+
+ std::vector<BasicBlock*> PredBlocks;
+ for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
+ PI != PE; ++PI)
+ PredBlocks.push_back(*PI);
+
+ assert(!PredBlocks.empty() && "No predblocks??");
+
+ DominatorTree &DT = getAnalysis<DominatorTree>();
+ bool NewBBDominatesNewBBSucc = true;
+ if (!DT.dominates(NewBB, NewBBSucc))
+ NewBBDominatesNewBBSucc = false;
+
+ // If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
+ // DF(PredBlocks[0]) without the stuff that the new block does not dominate
+ // a predecessor of.
+ if (NewBBDominatesNewBBSucc) {
+ DominanceFrontier::iterator DFI = find(PredBlocks[0]);
+ if (DFI != end()) {
+ DominanceFrontier::DomSetType Set = DFI->second;
+ // Filter out stuff in Set that we do not dominate a predecessor of.
+ for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
+ E = Set.end(); SetI != E;) {
+ bool DominatesPred = false;
+ for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
+ PI != E; ++PI)
+ if (DT.dominates(NewBB, *PI))
+ DominatesPred = true;
+ if (!DominatesPred)
+ Set.erase(SetI++);
+ else
+ ++SetI;
+ }
+
+ addBasicBlock(NewBB, Set);
+ }
+
+ } else {
+ // DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
+ // NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
+ // NewBBSucc)). NewBBSucc is the single successor of NewBB.
+ DominanceFrontier::DomSetType NewDFSet;
+ NewDFSet.insert(NewBBSucc);
+ addBasicBlock(NewBB, NewDFSet);
}
-
- // At this point, S is DFlocal. Now we union in DFup's of our children...
- // Loop through and visit the nodes that Node immediately dominates (Node's
- // children in the IDomTree)
+
+ // Now we must loop over all of the dominance frontiers in the function,
+ // replacing occurrences of NewBBSucc with NewBB in some cases. All
+ // blocks that dominate a block in PredBlocks and contained NewBBSucc in
+ // their dominance frontier must be updated to contain NewBB instead.
//
- for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
- NI != NE; ++NI) {
- DominatorTree::Node *IDominee = *NI;
- const DomSetType &ChildDF = calcDomFrontier(DT, IDominee);
-
- DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
- for (; CDFI != CDFE; ++CDFI) {
- if (!Node->dominates(DT[*CDFI]))
- S.insert(*CDFI);
+ for (Function::iterator FI = NewBB->getParent()->begin(),
+ FE = NewBB->getParent()->end(); FI != FE; ++FI) {
+ DominanceFrontier::iterator DFI = find(FI);
+ if (DFI == end()) continue; // unreachable block.
+
+ // Only consider dominators of NewBBSucc
+ if (!DFI->second.count(NewBBSucc)) continue;
+
+ bool BlockDominatesAny = false;
+ for (std::vector<BasicBlock*>::const_iterator BI = PredBlocks.begin(),
+ BE = PredBlocks.end(); BI != BE; ++BI) {
+ if (DT.dominates(FI, *BI)) {
+ BlockDominatesAny = true;
+ break;
+ }
+ }
+
+ if (BlockDominatesAny) {
+ // If NewBBSucc should not stay in our dominator frontier, remove it.
+ // We remove it unless there is a predecessor of NewBBSucc that we
+ // dominate, but we don't strictly dominate NewBBSucc.
+ bool ShouldRemove = true;
+ if ((BasicBlock*)FI == NewBBSucc
+ || !DT.dominates(FI, NewBBSucc)) {
+ // Okay, we know that PredDom does not strictly dominate NewBBSucc.
+ // Check to see if it dominates any predecessors of NewBBSucc.
+ for (pred_iterator PI = pred_begin(NewBBSucc),
+ E = pred_end(NewBBSucc); PI != E; ++PI)
+ if (DT.dominates(FI, *PI)) {
+ ShouldRemove = false;
+ break;
+ }
+
+ if (ShouldRemove)
+ removeFromFrontier(DFI, NewBBSucc);
+ addToFrontier(DFI, NewBB);
+
+ break;
+ }
}
}
+}
- return S;
+namespace {
+ class DFCalculateWorkObject {
+ public:
+ DFCalculateWorkObject(BasicBlock *B, BasicBlock *P,
+ const DomTreeNode *N,
+ const DomTreeNode *PN)
+ : currentBB(B), parentBB(P), Node(N), parentNode(PN) {}
+ BasicBlock *currentBB;
+ BasicBlock *parentBB;
+ const DomTreeNode *Node;
+ const DomTreeNode *parentNode;
+ };
}
const DominanceFrontier::DomSetType &
-DominanceFrontier::calcPostDomFrontier(const DominatorTree &DT,
- const DominatorTree::Node *Node) {
- // Loop over CFG successors to calculate DFlocal[Node]
- BasicBlock *BB = Node->getNode();
- DomSetType &S = Frontiers[BB]; // The new set to fill in...
- if (!Root) return S;
-
- for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
- SI != SE; ++SI) {
- // Does Node immediately dominate this predeccessor?
- if (DT[*SI]->getIDom() != Node)
- S.insert(*SI);
- }
+DominanceFrontier::calculate(const DominatorTree &DT,
+ const DomTreeNode *Node) {
+ BasicBlock *BB = Node->getBlock();
+ DomSetType *Result = NULL;
- // At this point, S is DFlocal. Now we union in DFup's of our children...
- // Loop through and visit the nodes that Node immediately dominates (Node's
- // children in the IDomTree)
- //
- for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
- NI != NE; ++NI) {
- DominatorTree::Node *IDominee = *NI;
- const DomSetType &ChildDF = calcPostDomFrontier(DT, IDominee);
-
- DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
- for (; CDFI != CDFE; ++CDFI) {
- if (!Node->dominates(DT[*CDFI]))
- S.insert(*CDFI);
+ std::vector<DFCalculateWorkObject> workList;
+ SmallPtrSet<BasicBlock *, 32> visited;
+
+ workList.push_back(DFCalculateWorkObject(BB, NULL, Node, NULL));
+ do {
+ DFCalculateWorkObject *currentW = &workList.back();
+ assert (currentW && "Missing work object.");
+
+ BasicBlock *currentBB = currentW->currentBB;
+ BasicBlock *parentBB = currentW->parentBB;
+ const DomTreeNode *currentNode = currentW->Node;
+ const DomTreeNode *parentNode = currentW->parentNode;
+ assert (currentBB && "Invalid work object. Missing current Basic Block");
+ assert (currentNode && "Invalid work object. Missing current Node");
+ DomSetType &S = Frontiers[currentBB];
+
+ // Visit each block only once.
+ if (visited.count(currentBB) == 0) {
+ visited.insert(currentBB);
+
+ // Loop over CFG successors to calculate DFlocal[currentNode]
+ for (succ_iterator SI = succ_begin(currentBB), SE = succ_end(currentBB);
+ SI != SE; ++SI) {
+ // Does Node immediately dominate this successor?
+ if (DT[*SI]->getIDom() != currentNode)
+ S.insert(*SI);
+ }
}
+
+ // At this point, S is DFlocal. Now we union in DFup's of our children...
+ // Loop through and visit the nodes that Node immediately dominates (Node's
+ // children in the IDomTree)
+ bool visitChild = false;
+ for (DomTreeNode::const_iterator NI = currentNode->begin(),
+ NE = currentNode->end(); NI != NE; ++NI) {
+ DomTreeNode *IDominee = *NI;
+ BasicBlock *childBB = IDominee->getBlock();
+ if (visited.count(childBB) == 0) {
+ workList.push_back(DFCalculateWorkObject(childBB, currentBB,
+ IDominee, currentNode));
+ visitChild = true;
+ }
+ }
+
+ // If all children are visited or there is any child then pop this block
+ // from the workList.
+ if (!visitChild) {
+
+ if (!parentBB) {
+ Result = &S;
+ break;
+ }
+
+ DomSetType::const_iterator CDFI = S.begin(), CDFE = S.end();
+ DomSetType &parentSet = Frontiers[parentBB];
+ for (; CDFI != CDFE; ++CDFI) {
+ if (!DT.properlyDominates(parentNode, DT[*CDFI]))
+ parentSet.insert(*CDFI);
+ }
+ workList.pop_back();
+ }
+
+ } while (!workList.empty());
+
+ return *Result;
+}
+
+void DominanceFrontierBase::print(std::ostream &o, const Module* ) const {
+ for (const_iterator I = begin(), E = end(); I != E; ++I) {
+ o << " DomFrontier for BB";
+ if (I->first)
+ WriteAsOperand(o, I->first, false);
+ else
+ o << " <<exit node>>";
+ o << " is:\t" << I->second << "\n";
}
+}
- return S;
+void DominanceFrontierBase::dump() {
+ print (llvm::cerr);
}
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