-//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
+//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
//
-// This file provides a simple class to calculate the dominator set of a method.
+// The LLVM Compiler Infrastructure
//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/Analysis/SimplifyCFG.h" // To get cfg::UnifyAllExitNodes
-#include "llvm/CFG.h"
-#include "llvm/Tools/STLExtras.h"
-#include <algorithm>
-
-//===----------------------------------------------------------------------===//
-// Helper Template
-//===----------------------------------------------------------------------===//
-
-// set_intersect - Identical to set_intersection, except that it works on
-// set<>'s and is nicer to use. Functionally, this iterates through S1,
-// removing elements that are not contained in S2.
+// 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.
//
-template <class Ty, class Ty2>
-void set_intersect(set<Ty> &S1, const set<Ty2> &S2) {
- for (typename set<Ty>::iterator I = S1.begin(); I != S1.end();) {
- const Ty &E = *I;
- ++I;
- if (!S2.count(E)) S1.erase(E); // Erase element if not in S2
- }
-}
-
//===----------------------------------------------------------------------===//
-// DominatorBase Implementation
+//
+// This file implements the post-dominator construction algorithms.
+//
//===----------------------------------------------------------------------===//
-bool cfg::DominatorBase::isPostDominator() const {
- return Root != Root->getParent()->front();
-}
-
+#include "llvm/Analysis/PostDominators.h"
+#include "llvm/Instructions.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SetOperations.h"
+using namespace llvm;
//===----------------------------------------------------------------------===//
-// DominatorSet Implementation
+// PostDominatorTree Implementation
//===----------------------------------------------------------------------===//
-// DominatorSet ctor - Build either the dominator set or the post-dominator
-// set for a method...
-//
-cfg::DominatorSet::DominatorSet(const Method *M) : DominatorBase(M->front()) {
- calcForwardDominatorSet(M);
-}
-
-// calcForwardDominatorSet - This method calculates the forward dominator sets
-// for the specified method.
-//
-void cfg::DominatorSet::calcForwardDominatorSet(const Method *M) {
- assert(Root && M && "Can't build dominator set of null method!");
- bool Changed;
- do {
- Changed = false;
+char PostDominatorTree::ID = 0;
+char PostDominanceFrontier::ID = 0;
+static RegisterPass<PostDominatorTree>
+F("postdomtree", "Post-Dominator Tree Construction", true);
- DomSetType WorkingSet;
- df_const_iterator It = df_begin(M), End = df_end(M);
- for ( ; It != End; ++It) {
- const BasicBlock *BB = *It;
- pred_const_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];
+unsigned PostDominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
+ unsigned N) {
+ std::vector<std::pair<BasicBlock *, InfoRec *> > workStack;
+ std::set<BasicBlock *> visited;
+ workStack.push_back(std::make_pair(V, &VInfo));
- for (++PI; PI != PEnd; ++PI) { // Intersect all of the predecessor 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);
-}
-
-// Postdominator set constructor. This ctor converts the specified method to
-// only have a single exit node (return stmt), then calculates the post
-// dominance sets for the method.
-//
-cfg::DominatorSet::DominatorSet(Method *M, bool PostDomSet)
- : DominatorBase(M->front()) {
- if (!PostDomSet) { calcForwardDominatorSet(M); return; }
-
- Root = cfg::UnifyAllExitNodes(M);
- assert(Root && "TODO: Don't handle case where there are no exit nodes yet!");
-
- bool Changed;
do {
- Changed = false;
+ BasicBlock *currentBB = workStack.back().first;
+ InfoRec *currentVInfo = workStack.back().second;
- set<const BasicBlock*> Visited;
- DomSetType WorkingSet;
- idf_const_iterator It = idf_begin(Root), End = idf_end(Root);
- for ( ; It != End; ++It) {
- const BasicBlock *BB = *It;
- succ_const_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];
+ // Visit each block only once.
+ if (visited.count(currentBB) == 0) {
- 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
+ visited.insert(currentBB);
+ currentVInfo->Semi = ++N;
+ currentVInfo->Label = currentBB;
+
+ Vertex.push_back(currentBB); // Vertex[n] = current;
+ // Info[currentBB].Ancestor = 0;
+ // Ancestor[n] = 0
+ // Child[currentBB] = 0;
+ currentVInfo->Size = 1; // Size[currentBB] = 1
}
- } while (Changed);
-}
-
-//===----------------------------------------------------------------------===//
-// ImmediateDominators Implementation
-//===----------------------------------------------------------------------===//
-
-// calcIDoms - Calculate the immediate dominator mapping, given a set of
-// dominators for every basic block.
-void cfg::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) {
- const 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;
+ // Visit children
+ bool visitChild = false;
+ for (pred_iterator PI = pred_begin(currentBB), PE = pred_end(currentBB);
+ PI != PE && !visitChild; ++PI) {
+ InfoRec &SuccVInfo = Info[*PI];
+ if (SuccVInfo.Semi == 0) {
+ SuccVInfo.Parent = currentBB;
+ if (visited.count (*PI) == 0) {
+ workStack.push_back(std::make_pair(*PI, &SuccVInfo));
+ visitChild = true;
+ }
}
}
- }
-}
+ // If all children are visited or if this block has no child then pop this
+ // block out of workStack.
+ if (!visitChild)
+ workStack.pop_back();
-//===----------------------------------------------------------------------===//
-// DominatorTree Implementation
-//===----------------------------------------------------------------------===//
+ } while (!workStack.empty());
-// DominatorTree dtor - Free all of the tree node memory.
-//
-cfg::DominatorTree::~DominatorTree() {
- for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
- delete I->second;
+ return N;
}
+void PostDominatorTree::Compress(BasicBlock *V, InfoRec &VInfo) {
+ BasicBlock *VAncestor = VInfo.Ancestor;
+ InfoRec &VAInfo = Info[VAncestor];
+ if (VAInfo.Ancestor == 0)
+ return;
+
+ Compress(VAncestor, VAInfo);
+
+ BasicBlock *VAncestorLabel = VAInfo.Label;
+ BasicBlock *VLabel = VInfo.Label;
+ if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
+ VInfo.Label = VAncestorLabel;
+
+ VInfo.Ancestor = VAInfo.Ancestor;
+}
-cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
- : DominatorBase(IDoms.getRoot()) {
- const Method *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_const_iterator 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];
+BasicBlock *PostDominatorTree::Eval(BasicBlock *V) {
+ InfoRec &VInfo = Info[V];
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
- }
- }
+ // Higher-complexity but faster implementation
+ if (VInfo.Ancestor == 0)
+ return V;
+ Compress(V, VInfo);
+ return VInfo.Label;
}
-void cfg::DominatorTree::calculate(const DominatorSet &DS) {
- Nodes[Root] = new Node(Root, 0); // Add a node for the root...
+void PostDominatorTree::Link(BasicBlock *V, BasicBlock *W,
+ InfoRec &WInfo) {
+ // Higher-complexity but faster implementation
+ WInfo.Ancestor = V;
+}
- if (!isPostDominator()) {
- // Iterate over all nodes in depth first order...
- for (df_const_iterator I = df_begin(Root), E = df_end(Root); I != E; ++I) {
- const 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
- // method.
- //
- 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;
- }
- }
+void PostDominatorTree::calculate(Function &F) {
+ // Step #0: Scan the function looking for the root nodes of the post-dominance
+ // relationships. These blocks, which have no successors, end with return and
+ // unwind instructions.
+ for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
+ if (succ_begin(I) == succ_end(I)) {
+ Instruction *Insn = I->getTerminator();
+ // Unreachable block is not a root node.
+ if (!isa<UnreachableInst>(Insn))
+ Roots.push_back(I);
}
- } else {
- // Iterate over all nodes in depth first order...
- for (idf_const_iterator I = idf_begin(Root), E = idf_end(Root); I != E; ++I) {
- const 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
- // method.
- //
- 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;
- }
+
+ Vertex.push_back(0);
+
+ // 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]], N);
+
+ for (unsigned i = N; i >= 2; --i) {
+ BasicBlock *W = Vertex[i];
+ InfoRec &WInfo = Info[W];
+
+ // Step #2: Calculate the semidominators of all vertices
+ for (succ_iterator SI = succ_begin(W), SE = succ_end(W); SI != SE; ++SI)
+ if (Info.count(*SI)) { // Only if this predecessor is reachable!
+ unsigned SemiU = Info[Eval(*SI)].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];
+ }
+
+ if (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.
+ BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
+ DomTreeNodes[Root] = RootNode = new DomTreeNode(Root, 0);
+
+ // Loop over all of the reachable blocks in the function...
+ for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
+ if (BasicBlock *ImmPostDom = 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 *IPDomNode = getNodeForBlock(ImmPostDom);
+
+ // Add a new tree node for this BasicBlock, and link it as a child of
+ // IDomNode
+ DomTreeNode *C = new DomTreeNode(I, IPDomNode);
+ DomTreeNodes[I] = C;
+ BBNode = IPDomNode->addChild(C);
+ }
+ }
+
+ // Free temporary memory used to construct idom's
+ IDoms.clear();
+ Info.clear();
+ std::vector<BasicBlock*>().swap(Vertex);
+
+ int dfsnum = 0;
+ // Iterate over all nodes in depth first order...
+ for (unsigned i = 0, e = Roots.size(); i != e; ++i)
+ for (idf_iterator<BasicBlock*> I = idf_begin(Roots[i]),
+ E = idf_end(Roots[i]); I != E; ++I) {
+ if (!getNodeForBlock(*I)->getIDom())
+ getNodeForBlock(*I)->assignDFSNumber(dfsnum);
+ }
+ DFSInfoValid = true;
}
+DomTreeNode *PostDominatorTree::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 postdominator.
+ BasicBlock *IPDom = getIDom(BB);
+ DomTreeNode *IPDomNode = getNodeForBlock(IPDom);
+
+ // Add a new tree node for this BasicBlock, and link it as a child of
+ // IDomNode
+ DomTreeNode *C = new DomTreeNode(BB, IPDomNode);
+ DomTreeNodes[BB] = C;
+ return BBNode = IPDomNode->addChild(C);
+}
//===----------------------------------------------------------------------===//
-// DominanceFrontier Implementation
+// PostDominanceFrontier Implementation
//===----------------------------------------------------------------------===//
-const cfg::DominanceFrontier::DomSetType &
-cfg::DominanceFrontier::calcDomFrontier(const DominatorTree &DT,
- const DominatorTree::Node *Node) {
- // Loop over CFG successors to calculate DFlocal[Node]
- const BasicBlock *BB = Node->getNode();
- DomSetType &S = Frontiers[BB]; // The new set to fill in...
-
- for (succ_const_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 = calcDomFrontier(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;
-}
+static RegisterPass<PostDominanceFrontier>
+H("postdomfrontier", "Post-Dominance Frontier Construction", true);
-const cfg::DominanceFrontier::DomSetType &
-cfg::DominanceFrontier::calcPostDomFrontier(const DominatorTree &DT,
- const DominatorTree::Node *Node) {
+const DominanceFrontier::DomSetType &
+PostDominanceFrontier::calculate(const PostDominatorTree &DT,
+ const DomTreeNode *Node) {
// Loop over CFG successors to calculate DFlocal[Node]
- const BasicBlock *BB = Node->getNode();
+ BasicBlock *BB = Node->getBlock();
DomSetType &S = Frontiers[BB]; // The new set to fill in...
-
- for (pred_const_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);
- }
+ if (getRoots().empty()) return S;
+
+ if (BB)
+ for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
+ SI != SE; ++SI) {
+ // Does Node immediately dominate this predecessor?
+ DomTreeNode *SINode = DT[*SI];
+ if (SINode && SINode->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 = calcDomFrontier(DT, IDominee);
+ for (DomTreeNode::const_iterator
+ NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
+ DomTreeNode *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);
+ if (!DT.properlyDominates(Node, DT[*CDFI]))
+ S.insert(*CDFI);
}
}
return S;
}
+
+// Ensure that this .cpp file gets linked when PostDominators.h is used.
+DEFINING_FILE_FOR(PostDominanceFrontier)
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