-//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
+//===- Dominators.cpp - Dominator Calculation -----------------------------===//
//
-// This file provides a simple class to calculate the dominator set of a method.
+// The LLVM Compiler Infrastructure
+//
+// This file 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/CFG.h"
-#include "llvm/Tools/STLExtras.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SetOperations.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Analysis/DominatorInternals.h"
+#include "llvm/Instructions.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/CommandLine.h"
#include <algorithm>
+using namespace llvm;
+
+// Always verify dominfo if expensive checking is enabled.
+#ifdef XDEBUG
+static bool VerifyDomInfo = true;
+#else
+static bool VerifyDomInfo = false;
+#endif
+static cl::opt<bool,true>
+VerifyDomInfoX("verify-dom-info", cl::location(VerifyDomInfo),
+ cl::desc("Verify dominator info (time consuming)"));
//===----------------------------------------------------------------------===//
-// Helper Template
+// DominatorTree Implementation
//===----------------------------------------------------------------------===//
-
-// 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.
//
-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
- }
-}
-
-
-//===----------------------------------------------------------------------===//
-// DominatorSet Implementation
+// Provide public access to DominatorTree information. Implementation details
+// can be found in DominatorCalculation.h.
+//
//===----------------------------------------------------------------------===//
-// DominatorSet ctor - Build either the dominator set or the post-dominator
-// set for a method...
-//
-cfg::DominatorSet::DominatorSet(const Method *M, bool PostDomSet)
- : Root(M->front()) {
- assert(Root && M && "Can't build dominator set of null method!");
- bool Changed;
- do {
- Changed = false;
-
- 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];
-
- 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);
+TEMPLATE_INSTANTIATION(class llvm::DomTreeNodeBase<BasicBlock>);
+TEMPLATE_INSTANTIATION(class llvm::DominatorTreeBase<BasicBlock>);
+
+char DominatorTree::ID = 0;
+INITIALIZE_PASS(DominatorTree, "domtree",
+ "Dominator Tree Construction", true, true);
+bool DominatorTree::runOnFunction(Function &F) {
+ DT->recalculate(F);
+ return false;
}
+void DominatorTree::verifyAnalysis() const {
+ if (!VerifyDomInfo) return;
-//===----------------------------------------------------------------------===//
-// ImmediateDominators Implementation
-//===----------------------------------------------------------------------===//
+ Function &F = *getRoot()->getParent();
-// 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;
- }
- }
- }
+ DominatorTree OtherDT;
+ OtherDT.getBase().recalculate(F);
+ assert(!compare(OtherDT) && "Invalid DominatorTree info!");
+}
+
+void DominatorTree::print(raw_ostream &OS, const Module *) const {
+ DT->print(OS);
+}
+
+// dominates - Return true if A dominates a use in B. This performs the
+// special checks necessary if A and B are in the same basic block.
+bool DominatorTree::dominates(const Instruction *A, const Instruction *B) const{
+ const BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
+
+ // If A is an invoke instruction, its value is only available in this normal
+ // successor block.
+ if (const InvokeInst *II = dyn_cast<InvokeInst>(A))
+ BBA = II->getNormalDest();
+
+ 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::const_iterator I = BBA->begin();
+ for (; &*I != A && &*I != B; ++I)
+ /*empty*/;
+
+ return &*I == A;
}
+
//===----------------------------------------------------------------------===//
-// DominatorTree Implementation
+// DominanceFrontier Implementation
//===----------------------------------------------------------------------===//
-// 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;
-}
+char DominanceFrontier::ID = 0;
+INITIALIZE_PASS(DominanceFrontier, "domfrontier",
+ "Dominance Frontier Construction", true, true);
+void DominanceFrontier::verifyAnalysis() const {
+ if (!VerifyDomInfo) return;
-cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
- : Root(IDoms.getRoot()) {
- assert(Root && Root->getParent() && "No method for IDoms?");
- const Method *M = Root->getParent();
+ DominatorTree &DT = getAnalysis<DominatorTree>();
- Nodes[Root] = new Node(Root, 0); // Add a node for the root...
+ DominanceFrontier OtherDF;
+ const std::vector<BasicBlock*> &DTRoots = DT.getRoots();
+ OtherDF.calculate(DT, DT.getNode(DTRoots[0]));
+ assert(!compare(OtherDF) && "Invalid DominanceFrontier info!");
+}
- // 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];
+// NewBB is split and now it has one successor. Update dominance 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);
+
+ SmallVector<BasicBlock*, 8> PredBlocks;
+ for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
+ PI != PE; ++PI)
+ PredBlocks.push_back(*PI);
+
+ if (PredBlocks.empty())
+ // If NewBB does not have any predecessors then it is a entry block.
+ // In this case, NewBB and its successor NewBBSucc dominates all
+ // other blocks.
+ return;
+
+ // NewBBSucc inherits original NewBB frontier.
+ DominanceFrontier::iterator NewBBI = find(NewBB);
+ if (NewBBI != end()) {
+ DominanceFrontier::DomSetType NewBBSet = NewBBI->second;
+ DominanceFrontier::DomSetType NewBBSuccSet;
+ NewBBSuccSet.insert(NewBBSet.begin(), NewBBSet.end());
+ addBasicBlock(NewBBSucc, NewBBSuccSet);
+ }
- 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];
+ // If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
+ // DF(NewBBSucc) without the stuff that the new block does not dominate
+ // a predecessor of.
+ DominatorTree &DT = getAnalysis<DominatorTree>();
+ if (DT.dominates(NewBB, NewBBSucc)) {
+ DominanceFrontier::iterator DFI = find(NewBBSucc);
+ 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;
+ }
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
+ if (NewBBI != end()) {
+ for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
+ E = Set.end(); SetI != E; ++SetI) {
+ BasicBlock *SB = *SetI;
+ addToFrontier(NewBBI, SB);
+ }
+ } else
+ 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);
}
-}
-
-void cfg::DominatorTree::calculate(const DominatorSet &DS) {
- Root = DS.getRoot();
- assert(Root && Root->getParent() && "No method for IDoms?");
- 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;
- 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(Nodes[*I] && "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;
+
+ // 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 (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 nodes that have NewBBSucc in their dominator frontier.
+ if (!DFI->second.count(NewBBSucc)) continue;
+
+ // Verify whether this block dominates a block in predblocks. If not, do
+ // not update it.
+ bool BlockDominatesAny = false;
+ for (SmallVectorImpl<BasicBlock*>::const_iterator BI = PredBlocks.begin(),
+ BE = PredBlocks.end(); BI != BE; ++BI) {
+ if (DT.dominates(FI, *BI)) {
+ BlockDominatesAny = true;
+ break;
}
}
+
+ // 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);
+ if (BlockDominatesAny && (&*FI == NewBB || !DT.dominates(FI, NewBB)))
+ addToFrontier(DFI, NewBB);
}
}
+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::calculate(const DominatorTree &DT,
+ const DomTreeNode *Node) {
+ BasicBlock *BB = Node->getBlock();
+ DomSetType *Result = NULL;
-//===----------------------------------------------------------------------===//
-// DominanceFrontier Implementation
-//===----------------------------------------------------------------------===//
+ std::vector<DFCalculateWorkObject> workList;
+ SmallPtrSet<BasicBlock *, 32> visited;
-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);
- }
+ 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)
- //
- 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);
+ // 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(raw_ostream &OS, const Module* ) const {
+ for (const_iterator I = begin(), E = end(); I != E; ++I) {
+ OS << " DomFrontier for BB ";
+ if (I->first)
+ WriteAsOperand(OS, I->first, false);
+ else
+ OS << " <<exit node>>";
+ OS << " is:\t";
+
+ const std::set<BasicBlock*> &BBs = I->second;
+
+ for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
+ I != E; ++I) {
+ OS << ' ';
+ if (*I)
+ WriteAsOperand(OS, *I, false);
+ else
+ OS << "<<exit node>>";
}
+ OS << "\n";
}
+}
- return S;
+void DominanceFrontierBase::dump() const {
+ print(dbgs());
}
+
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