1 //===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
3 // This file provides a simple class to calculate the dominator set of a method.
5 //===----------------------------------------------------------------------===//
7 #include "llvm/Analysis/Dominators.h"
8 #include "llvm/Transforms/UnifyMethodExitNodes.h"
9 #include "llvm/Method.h"
10 #include "Support/DepthFirstIterator.h"
11 #include "Support/STLExtras.h"
16 //===----------------------------------------------------------------------===//
18 //===----------------------------------------------------------------------===//
20 // set_intersect - Identical to set_intersection, except that it works on
21 // set<>'s and is nicer to use. Functionally, this iterates through S1,
22 // removing elements that are not contained in S2.
24 template <class Ty, class Ty2>
25 void set_intersect(set<Ty> &S1, const set<Ty2> &S2) {
26 for (typename set<Ty>::iterator I = S1.begin(); I != S1.end();) {
29 if (!S2.count(E)) S1.erase(E); // Erase element if not in S2
33 //===----------------------------------------------------------------------===//
34 // DominatorSet Implementation
35 //===----------------------------------------------------------------------===//
37 AnalysisID cfg::DominatorSet::ID(AnalysisID::create<cfg::DominatorSet>());
38 AnalysisID cfg::DominatorSet::PostDomID(AnalysisID::create<cfg::DominatorSet>());
40 bool cfg::DominatorSet::runOnMethod(Method *M) {
41 Doms.clear(); // Reset from the last time we were run...
43 if (isPostDominator())
44 calcPostDominatorSet(M);
46 calcForwardDominatorSet(M);
51 // calcForwardDominatorSet - This method calculates the forward dominator sets
52 // for the specified method.
54 void cfg::DominatorSet::calcForwardDominatorSet(Method *M) {
55 Root = M->getEntryNode();
56 assert(Root->pred_begin() == Root->pred_end() &&
57 "Root node has predecessors in method!");
63 DomSetType WorkingSet;
64 df_iterator<Method*> It = df_begin(M), End = df_end(M);
65 for ( ; It != End; ++It) {
66 const BasicBlock *BB = *It;
67 BasicBlock::pred_const_iterator PI = BB->pred_begin(),
68 PEnd = BB->pred_end();
69 if (PI != PEnd) { // Is there SOME predecessor?
70 // Loop until we get to a predecessor that has had it's dom set filled
71 // in at least once. We are guaranteed to have this because we are
72 // traversing the graph in DFO and have handled start nodes specially.
74 while (Doms[*PI].size() == 0) ++PI;
75 WorkingSet = Doms[*PI];
77 for (++PI; PI != PEnd; ++PI) { // Intersect all of the predecessor sets
78 DomSetType &PredSet = Doms[*PI];
80 set_intersect(WorkingSet, PredSet);
84 WorkingSet.insert(BB); // A block always dominates itself
85 DomSetType &BBSet = Doms[BB];
86 if (BBSet != WorkingSet) {
87 BBSet.swap(WorkingSet); // Constant time operation!
88 Changed = true; // The sets changed.
90 WorkingSet.clear(); // Clear out the set for next iteration
95 // Postdominator set constructor. This ctor converts the specified method to
96 // only have a single exit node (return stmt), then calculates the post
97 // dominance sets for the method.
99 void cfg::DominatorSet::calcPostDominatorSet(Method *M) {
100 // Since we require that the unify all exit nodes pass has been run, we know
101 // that there can be at most one return instruction in the method left.
104 Root = getAnalysis<UnifyMethodExitNodes>().getExitNode();
106 if (Root == 0) { // No exit node for the method? Postdomsets are all empty
107 for (Method::const_iterator MI = M->begin(), ME = M->end(); MI != ME; ++MI)
108 Doms[*MI] = DomSetType();
116 set<const BasicBlock*> Visited;
117 DomSetType WorkingSet;
118 idf_iterator<BasicBlock*> It = idf_begin(Root), End = idf_end(Root);
119 for ( ; It != End; ++It) {
120 const BasicBlock *BB = *It;
121 BasicBlock::succ_const_iterator PI = BB->succ_begin(),
122 PEnd = BB->succ_end();
123 if (PI != PEnd) { // Is there SOME predecessor?
124 // Loop until we get to a successor that has had it's dom set filled
125 // in at least once. We are guaranteed to have this because we are
126 // traversing the graph in DFO and have handled start nodes specially.
128 while (Doms[*PI].size() == 0) ++PI;
129 WorkingSet = Doms[*PI];
131 for (++PI; PI != PEnd; ++PI) { // Intersect all of the successor sets
132 DomSetType &PredSet = Doms[*PI];
134 set_intersect(WorkingSet, PredSet);
138 WorkingSet.insert(BB); // A block always dominates itself
139 DomSetType &BBSet = Doms[BB];
140 if (BBSet != WorkingSet) {
141 BBSet.swap(WorkingSet); // Constant time operation!
142 Changed = true; // The sets changed.
144 WorkingSet.clear(); // Clear out the set for next iteration
149 // getAnalysisUsageInfo - This obviously provides a dominator set, but it also
150 // uses the UnifyMethodExitNodes pass if building post-dominators
152 void cfg::DominatorSet::getAnalysisUsageInfo(Pass::AnalysisSet &Requires,
153 Pass::AnalysisSet &Destroyed,
154 Pass::AnalysisSet &Provided) {
155 if (isPostDominator()) {
156 Provided.push_back(PostDomID);
157 Requires.push_back(UnifyMethodExitNodes::ID);
159 Provided.push_back(ID);
164 //===----------------------------------------------------------------------===//
165 // ImmediateDominators Implementation
166 //===----------------------------------------------------------------------===//
168 AnalysisID cfg::ImmediateDominators::ID(AnalysisID::create<cfg::ImmediateDominators>());
169 AnalysisID cfg::ImmediateDominators::PostDomID(AnalysisID::create<cfg::ImmediateDominators>());
171 // calcIDoms - Calculate the immediate dominator mapping, given a set of
172 // dominators for every basic block.
173 void cfg::ImmediateDominators::calcIDoms(const DominatorSet &DS) {
174 // Loop over all of the nodes that have dominators... figuring out the IDOM
177 for (DominatorSet::const_iterator DI = DS.begin(), DEnd = DS.end();
179 const BasicBlock *BB = DI->first;
180 const DominatorSet::DomSetType &Dominators = DI->second;
181 unsigned DomSetSize = Dominators.size();
182 if (DomSetSize == 1) continue; // Root node... IDom = null
184 // Loop over all dominators of this node. This corresponds to looping over
185 // nodes in the dominator chain, looking for a node whose dominator set is
186 // equal to the current nodes, except that the current node does not exist
187 // in it. This means that it is one level higher in the dom chain than the
188 // current node, and it is our idom!
190 DominatorSet::DomSetType::const_iterator I = Dominators.begin();
191 DominatorSet::DomSetType::const_iterator End = Dominators.end();
192 for (; I != End; ++I) { // Iterate over dominators...
193 // All of our dominators should form a chain, where the number of elements
194 // in the dominator set indicates what level the node is at in the chain.
195 // We want the node immediately above us, so it will have an identical
196 // dominator set, except that BB will not dominate it... therefore it's
197 // dominator set size will be one less than BB's...
199 if (DS.getDominators(*I).size() == DomSetSize - 1) {
208 //===----------------------------------------------------------------------===//
209 // DominatorTree Implementation
210 //===----------------------------------------------------------------------===//
212 AnalysisID cfg::DominatorTree::ID(AnalysisID::create<cfg::DominatorTree>());
213 AnalysisID cfg::DominatorTree::PostDomID(AnalysisID::create<cfg::DominatorTree>());
215 // DominatorTree::reset - Free all of the tree node memory.
217 void cfg::DominatorTree::reset() {
218 for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
225 // Given immediate dominators, we can also calculate the dominator tree
226 cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
227 : DominatorBase(IDoms.getRoot()) {
228 const Method *M = Root->getParent();
230 Nodes[Root] = new Node(Root, 0); // Add a node for the root...
232 // Iterate over all nodes in depth first order...
233 for (df_iterator<const Method*> I = df_begin(M), E = df_end(M); I != E; ++I) {
234 const BasicBlock *BB = *I, *IDom = IDoms[*I];
236 if (IDom != 0) { // Ignore the root node and other nasty nodes
237 // We know that the immediate dominator should already have a node,
238 // because we are traversing the CFG in depth first order!
240 assert(Nodes[IDom] && "No node for IDOM?");
241 Node *IDomNode = Nodes[IDom];
243 // Add a new tree node for this BasicBlock, and link it as a child of
245 Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
251 void cfg::DominatorTree::calculate(const DominatorSet &DS) {
252 Nodes[Root] = new Node(Root, 0); // Add a node for the root...
254 if (!isPostDominator()) {
255 // Iterate over all nodes in depth first order...
256 for (df_iterator<BasicBlock*> I = df_begin(Root), E = df_end(Root);
258 const BasicBlock *BB = *I;
259 const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
260 unsigned DomSetSize = Dominators.size();
261 if (DomSetSize == 1) continue; // Root node... IDom = null
263 // Loop over all dominators of this node. This corresponds to looping over
264 // nodes in the dominator chain, looking for a node whose dominator set is
265 // equal to the current nodes, except that the current node does not exist
266 // in it. This means that it is one level higher in the dom chain than the
267 // current node, and it is our idom! We know that we have already added
268 // a DominatorTree node for our idom, because the idom must be a
269 // predecessor in the depth first order that we are iterating through the
272 DominatorSet::DomSetType::const_iterator I = Dominators.begin();
273 DominatorSet::DomSetType::const_iterator End = Dominators.end();
274 for (; I != End; ++I) { // Iterate over dominators...
275 // All of our dominators should form a chain, where the number of
276 // elements in the dominator set indicates what level the node is at in
277 // the chain. We want the node immediately above us, so it will have
278 // an identical dominator set, except that BB will not dominate it...
279 // therefore it's dominator set size will be one less than BB's...
281 if (DS.getDominators(*I).size() == DomSetSize - 1) {
282 // We know that the immediate dominator should already have a node,
283 // because we are traversing the CFG in depth first order!
285 Node *IDomNode = Nodes[*I];
286 assert(IDomNode && "No node for IDOM?");
288 // Add a new tree node for this BasicBlock, and link it as a child of
290 Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
296 // Iterate over all nodes in depth first order...
297 for (idf_iterator<BasicBlock*> I = idf_begin(Root), E = idf_end(Root);
299 const BasicBlock *BB = *I;
300 const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
301 unsigned DomSetSize = Dominators.size();
302 if (DomSetSize == 1) continue; // Root node... IDom = null
304 // Loop over all dominators of this node. This corresponds to looping
305 // over nodes in the dominator chain, looking for a node whose dominator
306 // set is equal to the current nodes, except that the current node does
307 // not exist in it. This means that it is one level higher in the dom
308 // chain than the current node, and it is our idom! We know that we have
309 // already added a DominatorTree node for our idom, because the idom must
310 // be a predecessor in the depth first order that we are iterating through
313 DominatorSet::DomSetType::const_iterator I = Dominators.begin();
314 DominatorSet::DomSetType::const_iterator End = Dominators.end();
315 for (; I != End; ++I) { // Iterate over dominators...
316 // All of our dominators should form a chain, where the number
317 // of elements in the dominator set indicates what level the
318 // node is at in the chain. We want the node immediately
319 // above us, so it will have an identical dominator set,
320 // except that BB will not dominate it... therefore it's
321 // dominator set size will be one less than BB's...
323 if (DS.getDominators(*I).size() == DomSetSize - 1) {
324 // We know that the immediate dominator should already have a node,
325 // because we are traversing the CFG in depth first order!
327 Node *IDomNode = Nodes[*I];
328 assert(IDomNode && "No node for IDOM?");
330 // Add a new tree node for this BasicBlock, and link it as a child of
332 Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
342 //===----------------------------------------------------------------------===//
343 // DominanceFrontier Implementation
344 //===----------------------------------------------------------------------===//
346 AnalysisID cfg::DominanceFrontier::ID(AnalysisID::create<cfg::DominanceFrontier>());
347 AnalysisID cfg::DominanceFrontier::PostDomID(AnalysisID::create<cfg::DominanceFrontier>());
349 const cfg::DominanceFrontier::DomSetType &
350 cfg::DominanceFrontier::calcDomFrontier(const DominatorTree &DT,
351 const DominatorTree::Node *Node) {
352 // Loop over CFG successors to calculate DFlocal[Node]
353 const BasicBlock *BB = Node->getNode();
354 DomSetType &S = Frontiers[BB]; // The new set to fill in...
356 for (BasicBlock::succ_const_iterator SI = BB->succ_begin(),
357 SE = BB->succ_end(); SI != SE; ++SI) {
358 // Does Node immediately dominate this successor?
359 if (DT[*SI]->getIDom() != Node)
363 // At this point, S is DFlocal. Now we union in DFup's of our children...
364 // Loop through and visit the nodes that Node immediately dominates (Node's
365 // children in the IDomTree)
367 for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
369 DominatorTree::Node *IDominee = *NI;
370 const DomSetType &ChildDF = calcDomFrontier(DT, IDominee);
372 DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
373 for (; CDFI != CDFE; ++CDFI) {
374 if (!Node->dominates(DT[*CDFI]))
382 const cfg::DominanceFrontier::DomSetType &
383 cfg::DominanceFrontier::calcPostDomFrontier(const DominatorTree &DT,
384 const DominatorTree::Node *Node) {
385 // Loop over CFG successors to calculate DFlocal[Node]
386 const BasicBlock *BB = Node->getNode();
387 DomSetType &S = Frontiers[BB]; // The new set to fill in...
390 for (BasicBlock::pred_const_iterator SI = BB->pred_begin(),
391 SE = BB->pred_end(); SI != SE; ++SI) {
392 // Does Node immediately dominate this predeccessor?
393 if (DT[*SI]->getIDom() != Node)
397 // At this point, S is DFlocal. Now we union in DFup's of our children...
398 // Loop through and visit the nodes that Node immediately dominates (Node's
399 // children in the IDomTree)
401 for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
403 DominatorTree::Node *IDominee = *NI;
404 const DomSetType &ChildDF = calcPostDomFrontier(DT, IDominee);
406 DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
407 for (; CDFI != CDFE; ++CDFI) {
408 if (!Node->dominates(DT[*CDFI]))