1 //===- Dominators.cpp - Dominator Calculation -----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements simple dominator construction algorithms for finding
11 // forward dominators. Postdominators are available in libanalysis, but are not
12 // included in libvmcore, because it's not needed. Forward dominators are
13 // needed to support the Verifier pass.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Analysis/DominanceFrontier.h"
18 #include "llvm/Support/CFG.h"
19 #include "llvm/Support/Compiler.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/ADT/DepthFirstIterator.h"
22 #include "llvm/ADT/SetOperations.h"
23 #include "llvm/ADT/SmallPtrSet.h"
24 #include "llvm/ADT/SmallVector.h"
25 #include "llvm/Analysis/DominatorInternals.h"
26 #include "llvm/Assembly/Writer.h"
27 #include "llvm/Instructions.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/Support/CommandLine.h"
33 // Always verify dominfo if expensive checking is enabled.
35 static bool VerifyDomInfo = true;
37 static bool VerifyDomInfo = false;
39 static cl::opt<bool,true>
40 VerifyDomInfoX("verify-dom-info", cl::location(VerifyDomInfo),
41 cl::desc("Verify dominator info (time consuming)"));
43 //===----------------------------------------------------------------------===//
44 // DominatorTree Implementation
45 //===----------------------------------------------------------------------===//
47 // Provide public access to DominatorTree information. Implementation details
48 // can be found in DominatorCalculation.h.
50 //===----------------------------------------------------------------------===//
52 TEMPLATE_INSTANTIATION(class llvm::DomTreeNodeBase<BasicBlock>);
53 TEMPLATE_INSTANTIATION(class llvm::DominatorTreeBase<BasicBlock>);
55 char DominatorTree::ID = 0;
56 INITIALIZE_PASS(DominatorTree, "domtree",
57 "Dominator Tree Construction", true, true)
59 bool DominatorTree::runOnFunction(Function &F) {
64 void DominatorTree::verifyAnalysis() const {
65 if (!VerifyDomInfo) return;
67 Function &F = *getRoot()->getParent();
69 DominatorTree OtherDT;
70 OtherDT.getBase().recalculate(F);
71 if (compare(OtherDT)) {
72 errs() << "DominatorTree is not up to date! Computed:\n";
75 errs() << "\nActual:\n";
76 OtherDT.print(errs());
81 void DominatorTree::print(raw_ostream &OS, const Module *) const {
85 // dominates - Return true if A dominates a use in B. This performs the
86 // special checks necessary if A and B are in the same basic block.
87 bool DominatorTree::dominates(const Instruction *A, const Instruction *B) const{
88 const BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
90 // If A is an invoke instruction, its value is only available in this normal
92 if (const InvokeInst *II = dyn_cast<InvokeInst>(A))
93 BBA = II->getNormalDest();
95 if (BBA != BBB) return dominates(BBA, BBB);
97 // It is not possible to determine dominance between two PHI nodes
98 // based on their ordering.
99 if (isa<PHINode>(A) && isa<PHINode>(B))
102 // Loop through the basic block until we find A or B.
103 BasicBlock::const_iterator I = BBA->begin();
104 for (; &*I != A && &*I != B; ++I)
112 //===----------------------------------------------------------------------===//
113 // DominanceFrontier Implementation
114 //===----------------------------------------------------------------------===//
116 char DominanceFrontier::ID = 0;
117 INITIALIZE_PASS_BEGIN(DominanceFrontier, "domfrontier",
118 "Dominance Frontier Construction", true, true)
119 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
120 INITIALIZE_PASS_END(DominanceFrontier, "domfrontier",
121 "Dominance Frontier Construction", true, true)
123 void DominanceFrontier::verifyAnalysis() const {
124 if (!VerifyDomInfo) return;
126 DominatorTree &DT = getAnalysis<DominatorTree>();
128 DominanceFrontier OtherDF;
129 const std::vector<BasicBlock*> &DTRoots = DT.getRoots();
130 OtherDF.calculate(DT, DT.getNode(DTRoots[0]));
131 assert(!compare(OtherDF) && "Invalid DominanceFrontier info!");
135 class DFCalculateWorkObject {
137 DFCalculateWorkObject(BasicBlock *B, BasicBlock *P,
138 const DomTreeNode *N,
139 const DomTreeNode *PN)
140 : currentBB(B), parentBB(P), Node(N), parentNode(PN) {}
141 BasicBlock *currentBB;
142 BasicBlock *parentBB;
143 const DomTreeNode *Node;
144 const DomTreeNode *parentNode;
148 const DominanceFrontier::DomSetType &
149 DominanceFrontier::calculate(const DominatorTree &DT,
150 const DomTreeNode *Node) {
151 BasicBlock *BB = Node->getBlock();
152 DomSetType *Result = NULL;
154 std::vector<DFCalculateWorkObject> workList;
155 SmallPtrSet<BasicBlock *, 32> visited;
157 workList.push_back(DFCalculateWorkObject(BB, NULL, Node, NULL));
159 DFCalculateWorkObject *currentW = &workList.back();
160 assert (currentW && "Missing work object.");
162 BasicBlock *currentBB = currentW->currentBB;
163 BasicBlock *parentBB = currentW->parentBB;
164 const DomTreeNode *currentNode = currentW->Node;
165 const DomTreeNode *parentNode = currentW->parentNode;
166 assert (currentBB && "Invalid work object. Missing current Basic Block");
167 assert (currentNode && "Invalid work object. Missing current Node");
168 DomSetType &S = Frontiers[currentBB];
170 // Visit each block only once.
171 if (visited.count(currentBB) == 0) {
172 visited.insert(currentBB);
174 // Loop over CFG successors to calculate DFlocal[currentNode]
175 for (succ_iterator SI = succ_begin(currentBB), SE = succ_end(currentBB);
177 // Does Node immediately dominate this successor?
178 if (DT[*SI]->getIDom() != currentNode)
183 // At this point, S is DFlocal. Now we union in DFup's of our children...
184 // Loop through and visit the nodes that Node immediately dominates (Node's
185 // children in the IDomTree)
186 bool visitChild = false;
187 for (DomTreeNode::const_iterator NI = currentNode->begin(),
188 NE = currentNode->end(); NI != NE; ++NI) {
189 DomTreeNode *IDominee = *NI;
190 BasicBlock *childBB = IDominee->getBlock();
191 if (visited.count(childBB) == 0) {
192 workList.push_back(DFCalculateWorkObject(childBB, currentBB,
193 IDominee, currentNode));
198 // If all children are visited or there is any child then pop this block
199 // from the workList.
207 DomSetType::const_iterator CDFI = S.begin(), CDFE = S.end();
208 DomSetType &parentSet = Frontiers[parentBB];
209 for (; CDFI != CDFE; ++CDFI) {
210 if (!DT.properlyDominates(parentNode, DT[*CDFI]))
211 parentSet.insert(*CDFI);
216 } while (!workList.empty());
221 void DominanceFrontierBase::print(raw_ostream &OS, const Module* ) const {
222 for (const_iterator I = begin(), E = end(); I != E; ++I) {
223 OS << " DomFrontier for BB ";
225 WriteAsOperand(OS, I->first, false);
227 OS << " <<exit node>>";
230 const std::set<BasicBlock*> &BBs = I->second;
232 for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
236 WriteAsOperand(OS, *I, false);
238 OS << "<<exit node>>";
244 void DominanceFrontierBase::dump() const {