1 //===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
3 // This file provides a simple class to calculate the dominator set of a
6 //===----------------------------------------------------------------------===//
8 #include "llvm/Analysis/Dominators.h"
9 #include "llvm/Transforms/UnifyMethodExitNodes.h"
10 #include "llvm/Function.h"
11 #include "llvm/Support/CFG.h"
12 #include "Support/DepthFirstIterator.h"
13 #include "Support/STLExtras.h"
14 #include "Support/SetOperations.h"
18 //===----------------------------------------------------------------------===//
19 // DominatorSet Implementation
20 //===----------------------------------------------------------------------===//
22 AnalysisID cfg::DominatorSet::ID(AnalysisID::create<cfg::DominatorSet>());
23 AnalysisID cfg::DominatorSet::PostDomID(AnalysisID::create<cfg::DominatorSet>());
25 bool cfg::DominatorSet::runOnFunction(Function *F) {
26 Doms.clear(); // Reset from the last time we were run...
28 if (isPostDominator())
29 calcPostDominatorSet(F);
31 calcForwardDominatorSet(F);
36 // calcForwardDominatorSet - This method calculates the forward dominator sets
37 // for the specified function.
39 void cfg::DominatorSet::calcForwardDominatorSet(Function *M) {
40 Root = M->getEntryNode();
41 assert(pred_begin(Root) == pred_end(Root) &&
42 "Root node has predecessors in function!");
48 DomSetType WorkingSet;
49 df_iterator<Function*> It = df_begin(M), End = df_end(M);
50 for ( ; It != End; ++It) {
51 const BasicBlock *BB = *It;
52 pred_const_iterator PI = pred_begin(BB), PEnd = pred_end(BB);
53 if (PI != PEnd) { // Is there SOME predecessor?
54 // Loop until we get to a predecessor that has had it's dom set filled
55 // in at least once. We are guaranteed to have this because we are
56 // traversing the graph in DFO and have handled start nodes specially.
58 while (Doms[*PI].size() == 0) ++PI;
59 WorkingSet = Doms[*PI];
61 for (++PI; PI != PEnd; ++PI) { // Intersect all of the predecessor sets
62 DomSetType &PredSet = Doms[*PI];
64 set_intersect(WorkingSet, PredSet);
68 WorkingSet.insert(BB); // A block always dominates itself
69 DomSetType &BBSet = Doms[BB];
70 if (BBSet != WorkingSet) {
71 BBSet.swap(WorkingSet); // Constant time operation!
72 Changed = true; // The sets changed.
74 WorkingSet.clear(); // Clear out the set for next iteration
79 // Postdominator set constructor. This ctor converts the specified function to
80 // only have a single exit node (return stmt), then calculates the post
81 // dominance sets for the function.
83 void cfg::DominatorSet::calcPostDominatorSet(Function *M) {
84 // Since we require that the unify all exit nodes pass has been run, we know
85 // that there can be at most one return instruction in the function left.
88 Root = getAnalysis<UnifyMethodExitNodes>().getExitNode();
90 if (Root == 0) { // No exit node for the function? Postdomsets are all empty
91 for (Function::const_iterator MI = M->begin(), ME = M->end(); MI!=ME; ++MI)
92 Doms[*MI] = DomSetType();
100 set<const BasicBlock*> Visited;
101 DomSetType WorkingSet;
102 idf_iterator<BasicBlock*> It = idf_begin(Root), End = idf_end(Root);
103 for ( ; It != End; ++It) {
104 const BasicBlock *BB = *It;
105 succ_const_iterator PI = succ_begin(BB), PEnd = succ_end(BB);
106 if (PI != PEnd) { // Is there SOME predecessor?
107 // Loop until we get to a successor that has had it's dom set filled
108 // in at least once. We are guaranteed to have this because we are
109 // traversing the graph in DFO and have handled start nodes specially.
111 while (Doms[*PI].size() == 0) ++PI;
112 WorkingSet = Doms[*PI];
114 for (++PI; PI != PEnd; ++PI) { // Intersect all of the successor sets
115 DomSetType &PredSet = Doms[*PI];
117 set_intersect(WorkingSet, PredSet);
121 WorkingSet.insert(BB); // A block always dominates itself
122 DomSetType &BBSet = Doms[BB];
123 if (BBSet != WorkingSet) {
124 BBSet.swap(WorkingSet); // Constant time operation!
125 Changed = true; // The sets changed.
127 WorkingSet.clear(); // Clear out the set for next iteration
132 // getAnalysisUsage - This obviously provides a dominator set, but it also
133 // uses the UnifyFunctionExitNodes pass if building post-dominators
135 void cfg::DominatorSet::getAnalysisUsage(AnalysisUsage &AU) const {
136 AU.setPreservesAll();
137 if (isPostDominator()) {
138 AU.addProvided(PostDomID);
139 AU.addRequired(UnifyMethodExitNodes::ID);
146 //===----------------------------------------------------------------------===//
147 // ImmediateDominators Implementation
148 //===----------------------------------------------------------------------===//
150 AnalysisID cfg::ImmediateDominators::ID(AnalysisID::create<cfg::ImmediateDominators>());
151 AnalysisID cfg::ImmediateDominators::PostDomID(AnalysisID::create<cfg::ImmediateDominators>());
153 // calcIDoms - Calculate the immediate dominator mapping, given a set of
154 // dominators for every basic block.
155 void cfg::ImmediateDominators::calcIDoms(const DominatorSet &DS) {
156 // Loop over all of the nodes that have dominators... figuring out the IDOM
159 for (DominatorSet::const_iterator DI = DS.begin(), DEnd = DS.end();
161 const BasicBlock *BB = DI->first;
162 const DominatorSet::DomSetType &Dominators = DI->second;
163 unsigned DomSetSize = Dominators.size();
164 if (DomSetSize == 1) continue; // Root node... IDom = null
166 // Loop over all dominators of this node. This corresponds to looping over
167 // nodes in the dominator chain, looking for a node whose dominator set is
168 // equal to the current nodes, except that the current node does not exist
169 // in it. This means that it is one level higher in the dom chain than the
170 // current node, and it is our idom!
172 DominatorSet::DomSetType::const_iterator I = Dominators.begin();
173 DominatorSet::DomSetType::const_iterator End = Dominators.end();
174 for (; I != End; ++I) { // Iterate over dominators...
175 // All of our dominators should form a chain, where the number of elements
176 // in the dominator set indicates what level the node is at in the chain.
177 // We want the node immediately above us, so it will have an identical
178 // dominator set, except that BB will not dominate it... therefore it's
179 // dominator set size will be one less than BB's...
181 if (DS.getDominators(*I).size() == DomSetSize - 1) {
190 //===----------------------------------------------------------------------===//
191 // DominatorTree Implementation
192 //===----------------------------------------------------------------------===//
194 AnalysisID cfg::DominatorTree::ID(AnalysisID::create<cfg::DominatorTree>());
195 AnalysisID cfg::DominatorTree::PostDomID(AnalysisID::create<cfg::DominatorTree>());
197 // DominatorTree::reset - Free all of the tree node memory.
199 void cfg::DominatorTree::reset() {
200 for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
207 // Given immediate dominators, we can also calculate the dominator tree
208 cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
209 : DominatorBase(IDoms.getRoot()) {
210 const Function *M = Root->getParent();
212 Nodes[Root] = new Node(Root, 0); // Add a node for the root...
214 // Iterate over all nodes in depth first order...
215 for (df_iterator<const Function*> I = df_begin(M), E = df_end(M); I!=E; ++I) {
216 const BasicBlock *BB = *I, *IDom = IDoms[*I];
218 if (IDom != 0) { // Ignore the root node and other nasty nodes
219 // We know that the immediate dominator should already have a node,
220 // because we are traversing the CFG in depth first order!
222 assert(Nodes[IDom] && "No node for IDOM?");
223 Node *IDomNode = Nodes[IDom];
225 // Add a new tree node for this BasicBlock, and link it as a child of
227 Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
233 void cfg::DominatorTree::calculate(const DominatorSet &DS) {
234 Nodes[Root] = new Node(Root, 0); // Add a node for the root...
236 if (!isPostDominator()) {
237 // Iterate over all nodes in depth first order...
238 for (df_iterator<BasicBlock*> I = df_begin(Root), E = df_end(Root);
240 const BasicBlock *BB = *I;
241 const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
242 unsigned DomSetSize = Dominators.size();
243 if (DomSetSize == 1) continue; // Root node... IDom = null
245 // Loop over all dominators of this node. This corresponds to looping over
246 // nodes in the dominator chain, looking for a node whose dominator set is
247 // equal to the current nodes, except that the current node does not exist
248 // in it. This means that it is one level higher in the dom chain than the
249 // current node, and it is our idom! We know that we have already added
250 // a DominatorTree node for our idom, because the idom must be a
251 // predecessor in the depth first order that we are iterating through the
254 DominatorSet::DomSetType::const_iterator I = Dominators.begin();
255 DominatorSet::DomSetType::const_iterator End = Dominators.end();
256 for (; I != End; ++I) { // Iterate over dominators...
257 // All of our dominators should form a chain, where the number of
258 // elements in the dominator set indicates what level the node is at in
259 // the chain. We want the node immediately above us, so it will have
260 // an identical dominator set, except that BB will not dominate it...
261 // therefore it's dominator set size will be one less than BB's...
263 if (DS.getDominators(*I).size() == DomSetSize - 1) {
264 // We know that the immediate dominator should already have a node,
265 // because we are traversing the CFG in depth first order!
267 Node *IDomNode = Nodes[*I];
268 assert(IDomNode && "No node for IDOM?");
270 // Add a new tree node for this BasicBlock, and link it as a child of
272 Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
278 // Iterate over all nodes in depth first order...
279 for (idf_iterator<BasicBlock*> I = idf_begin(Root), E = idf_end(Root);
281 const BasicBlock *BB = *I;
282 const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
283 unsigned DomSetSize = Dominators.size();
284 if (DomSetSize == 1) continue; // Root node... IDom = null
286 // Loop over all dominators of this node. This corresponds to looping
287 // over nodes in the dominator chain, looking for a node whose dominator
288 // set is equal to the current nodes, except that the current node does
289 // not exist in it. This means that it is one level higher in the dom
290 // chain than the current node, and it is our idom! We know that we have
291 // already added a DominatorTree node for our idom, because the idom must
292 // be a predecessor in the depth first order that we are iterating through
295 DominatorSet::DomSetType::const_iterator I = Dominators.begin();
296 DominatorSet::DomSetType::const_iterator End = Dominators.end();
297 for (; I != End; ++I) { // Iterate over dominators...
298 // All of our dominators should form a chain, where the number
299 // of elements in the dominator set indicates what level the
300 // node is at in the chain. We want the node immediately
301 // above us, so it will have an identical dominator set,
302 // except that BB will not dominate it... therefore it's
303 // dominator set size will be one less than BB's...
305 if (DS.getDominators(*I).size() == DomSetSize - 1) {
306 // We know that the immediate dominator should already have a node,
307 // because we are traversing the CFG in depth first order!
309 Node *IDomNode = Nodes[*I];
310 assert(IDomNode && "No node for IDOM?");
312 // Add a new tree node for this BasicBlock, and link it as a child of
314 Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
324 //===----------------------------------------------------------------------===//
325 // DominanceFrontier Implementation
326 //===----------------------------------------------------------------------===//
328 AnalysisID cfg::DominanceFrontier::ID(AnalysisID::create<cfg::DominanceFrontier>());
329 AnalysisID cfg::DominanceFrontier::PostDomID(AnalysisID::create<cfg::DominanceFrontier>());
331 const cfg::DominanceFrontier::DomSetType &
332 cfg::DominanceFrontier::calcDomFrontier(const DominatorTree &DT,
333 const DominatorTree::Node *Node) {
334 // Loop over CFG successors to calculate DFlocal[Node]
335 const BasicBlock *BB = Node->getNode();
336 DomSetType &S = Frontiers[BB]; // The new set to fill in...
338 for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB);
340 // Does Node immediately dominate this successor?
341 if (DT[*SI]->getIDom() != Node)
345 // At this point, S is DFlocal. Now we union in DFup's of our children...
346 // Loop through and visit the nodes that Node immediately dominates (Node's
347 // children in the IDomTree)
349 for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
351 DominatorTree::Node *IDominee = *NI;
352 const DomSetType &ChildDF = calcDomFrontier(DT, IDominee);
354 DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
355 for (; CDFI != CDFE; ++CDFI) {
356 if (!Node->dominates(DT[*CDFI]))
364 const cfg::DominanceFrontier::DomSetType &
365 cfg::DominanceFrontier::calcPostDomFrontier(const DominatorTree &DT,
366 const DominatorTree::Node *Node) {
367 // Loop over CFG successors to calculate DFlocal[Node]
368 const BasicBlock *BB = Node->getNode();
369 DomSetType &S = Frontiers[BB]; // The new set to fill in...
372 for (pred_const_iterator SI = pred_begin(BB), SE = pred_end(BB);
374 // Does Node immediately dominate this predeccessor?
375 if (DT[*SI]->getIDom() != Node)
379 // At this point, S is DFlocal. Now we union in DFup's of our children...
380 // Loop through and visit the nodes that Node immediately dominates (Node's
381 // children in the IDomTree)
383 for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
385 DominatorTree::Node *IDominee = *NI;
386 const DomSetType &ChildDF = calcPostDomFrontier(DT, IDominee);
388 DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
389 for (; CDFI != CDFE; ++CDFI) {
390 if (!Node->dominates(DT[*CDFI]))