| //===- Dominators.cpp - Dominator Calculation -----------------------------===// |
| // |
| // 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/Support/CFG.h" |
| #include "llvm/Assembly/Writer.h" |
| #include "Support/DepthFirstIterator.h" |
| #include "Support/SetOperations.h" |
| |
| namespace llvm { |
| |
| //===----------------------------------------------------------------------===// |
| // DominatorSet Implementation |
| //===----------------------------------------------------------------------===// |
| |
| static RegisterAnalysis<DominatorSet> |
| A("domset", "Dominator Set Construction", 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 DominatorSetBase::dominates(Instruction *A, Instruction *B) const { |
| BasicBlock *BBA = A->getParent(), *BBB = B->getParent(); |
| if (BBA != BBB) return dominates(BBA, BBB); |
| |
| // Loop through the basic block until we find A or B. |
| BasicBlock::iterator I = BBA->begin(); |
| for (; &*I != A && &*I != B; ++I) /*empty*/; |
| |
| // A dominates B if it is found first in the basic block... |
| return &*I == A; |
| } |
| |
| |
| void DominatorSet::calculateDominatorsFromBlock(BasicBlock *RootBB) { |
| bool Changed; |
| Doms[RootBB].insert(RootBB); // Root always dominates itself... |
| do { |
| Changed = false; |
| |
| DomSetType WorkingSet; |
| df_iterator<BasicBlock*> It = df_begin(RootBB), End = df_end(RootBB); |
| 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 its 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, |
| // except when there are unreachable blocks. |
| // |
| while (PI != PEnd && Doms[*PI].empty()) ++PI; |
| if (PI != PEnd) { // Not unreachable code case? |
| WorkingSet = Doms[*PI]; |
| |
| // Intersect all of the predecessor sets |
| for (++PI; PI != PEnd; ++PI) { |
| DomSetType &PredSet = Doms[*PI]; |
| if (PredSet.size()) |
| set_intersect(WorkingSet, PredSet); |
| } |
| } |
| } else { |
| assert(Roots.size() == 1 && BB == Roots[0] && |
| "We got into unreachable code somehow!"); |
| } |
| |
| WorkingSet.insert(BB); // A block always dominates itself |
| DomSetType &BBSet = Doms[BB]; |
| if (BBSet != WorkingSet) { |
| //assert(WorkingSet.size() > BBSet.size() && "Must only grow sets!"); |
| BBSet.swap(WorkingSet); // Constant time operation! |
| Changed = true; // The sets changed. |
| } |
| WorkingSet.clear(); // Clear out the set for next iteration |
| } |
| } while (Changed); |
| } |
| |
| |
| |
| // runOnFunction - This method calculates the forward dominator sets for the |
| // specified function. |
| // |
| bool DominatorSet::runOnFunction(Function &F) { |
| BasicBlock *Root = &F.getEntryBlock(); |
| Roots.clear(); |
| Roots.push_back(Root); |
| assert(pred_begin(Root) == pred_end(Root) && |
| "Root node has predecessors in function!"); |
| recalculate(); |
| return false; |
| } |
| |
| void DominatorSet::recalculate() { |
| assert(Roots.size() == 1 && "DominatorSet should have single root block!"); |
| Doms.clear(); // Reset from the last time we were run... |
| |
| // Calculate dominator sets for the reachable basic blocks... |
| calculateDominatorsFromBlock(Roots[0]); |
| |
| |
| // Loop through the function, ensuring that every basic block has at least an |
| // empty set of nodes. This is important for the case when there is |
| // unreachable blocks. |
| Function *F = Roots[0]->getParent(); |
| for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) Doms[I]; |
| } |
| |
| |
| 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; |
| } |
| |
| void DominatorSetBase::print(std::ostream &o) const { |
| for (const_iterator I = begin(), E = end(); I != E; ++I) { |
| o << " DomSet For BB: "; |
| if (I->first) |
| WriteAsOperand(o, I->first, false); |
| else |
| o << " <<exit node>>"; |
| o << " is:\t" << I->second << "\n"; |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ImmediateDominators Implementation |
| //===----------------------------------------------------------------------===// |
| |
| static RegisterAnalysis<ImmediateDominators> |
| C("idom", "Immediate Dominators Construction", true); |
| |
| // calcIDoms - Calculate the immediate dominator mapping, given a set of |
| // dominators for every basic block. |
| void ImmediateDominatorsBase::calcIDoms(const DominatorSetBase &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; |
| } |
| } |
| } |
| } |
| |
| void ImmediateDominatorsBase::print(std::ostream &o) const { |
| for (const_iterator I = begin(), E = end(); I != E; ++I) { |
| o << " Immediate Dominator For Basic Block:"; |
| if (I->first) |
| WriteAsOperand(o, I->first, false); |
| else |
| o << " <<exit node>>"; |
| o << " is:"; |
| if (I->second) |
| WriteAsOperand(o, I->second, false); |
| else |
| o << " <<exit node>>"; |
| o << "\n"; |
| } |
| o << "\n"; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // DominatorTree Implementation |
| //===----------------------------------------------------------------------===// |
| |
| static RegisterAnalysis<DominatorTree> |
| E("domtree", "Dominator Tree Construction", true); |
| |
| // DominatorTreeBase::reset - Free all of the tree node memory. |
| // |
| void DominatorTreeBase::reset() { |
| for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) |
| delete I->second; |
| Nodes.clear(); |
| RootNode = 0; |
| } |
| |
| void DominatorTreeBase::Node::setIDom(Node *NewIDom) { |
| assert(IDom && "No immediate dominator?"); |
| if (IDom != NewIDom) { |
| std::vector<Node*>::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); |
| } |
| } |
| |
| |
| |
| void DominatorTree::calculate(const DominatorSet &DS) { |
| assert(Roots.size() == 1 && "DominatorTree should have 1 root block!"); |
| BasicBlock *Root = Roots[0]; |
| Nodes[Root] = RootNode = new Node(Root, 0); // Add a node for the root... |
| |
| // 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; |
| } |
| } |
| } |
| } |
| |
| |
| static std::ostream &operator<<(std::ostream &o, |
| const DominatorTreeBase::Node *Node) { |
| if (Node->getBlock()) |
| WriteAsOperand(o, Node->getBlock(), false); |
| else |
| o << " <<exit node>>"; |
| return o << "\n"; |
| } |
| |
| static void PrintDomTree(const DominatorTreeBase::Node *N, std::ostream &o, |
| unsigned Lev) { |
| o << std::string(2*Lev, ' ') << "[" << Lev << "] " << N; |
| for (DominatorTreeBase::Node::const_iterator I = N->begin(), E = N->end(); |
| I != E; ++I) |
| PrintDomTree(*I, o, Lev+1); |
| } |
| |
| void DominatorTreeBase::print(std::ostream &o) const { |
| o << "=============================--------------------------------\n" |
| << "Inorder Dominator Tree:\n"; |
| PrintDomTree(getRootNode(), o, 1); |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // DominanceFrontier Implementation |
| //===----------------------------------------------------------------------===// |
| |
| static RegisterAnalysis<DominanceFrontier> |
| G("domfrontier", "Dominance Frontier Construction", true); |
| |
| const DominanceFrontier::DomSetType & |
| DominanceFrontier::calculate(const DominatorTree &DT, |
| const DominatorTree::Node *Node) { |
| // Loop over CFG successors to calculate DFlocal[Node] |
| BasicBlock *BB = Node->getBlock(); |
| 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); |
| } |
| |
| // 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 = calculate(DT, IDominee); |
| |
| DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end(); |
| for (; CDFI != CDFE; ++CDFI) { |
| if (!Node->dominates(DT[*CDFI])) |
| S.insert(*CDFI); |
| } |
| } |
| |
| return S; |
| } |
| |
| void DominanceFrontierBase::print(std::ostream &o) 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"; |
| } |
| } |
| |
| } // End llvm namespace |