-//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
+//===- Dominators.cpp - Dominator Calculation -----------------------------===//
//
-// This file provides a simple class to calculate the dominator set of a
-// function.
+// 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/Transforms/UnifyMethodExitNodes.h"
-#include "llvm/Function.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Assembly/Writer.h"
#include "Support/DepthFirstIterator.h"
-#include "Support/STLExtras.h"
#include "Support/SetOperations.h"
-#include <algorithm>
-using std::set;
//===----------------------------------------------------------------------===//
// DominatorSet Implementation
//===----------------------------------------------------------------------===//
-AnalysisID cfg::DominatorSet::ID(AnalysisID::create<cfg::DominatorSet>());
-AnalysisID cfg::DominatorSet::PostDomID(AnalysisID::create<cfg::DominatorSet>());
+static RegisterAnalysis<DominatorSet>
+A("domset", "Dominator Set Construction", true);
-bool cfg::DominatorSet::runOnFunction(Function *F) {
- Doms.clear(); // Reset from the last time we were run...
-
- if (isPostDominator())
- calcPostDominatorSet(F);
- else
- calcForwardDominatorSet(F);
- return false;
+// dominates - Return true if A dominates B. This performs the special checks
+// necessary if A and B are in the same basic block.
+//
+bool DominatorSetBase::dominates(Instruction *A, Instruction *B) const {
+ BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
+ if (BBA != BBB) return dominates(BBA, BBB);
+
+ // Loop through the basic block until we find A or B.
+ BasicBlock::iterator I = BBA->begin();
+ for (; &*I != A && &*I != B; ++I) /*empty*/;
+
+ // A dominates B if it is found first in the basic block...
+ return &*I == A;
}
-// calcForwardDominatorSet - This method calculates the forward dominator sets
-// for the specified function.
-//
-void cfg::DominatorSet::calcForwardDominatorSet(Function *M) {
- Root = M->getEntryNode();
- assert(pred_begin(Root) == pred_end(Root) &&
- "Root node has predecessors in function!");
-
+void DominatorSet::calculateDominatorsFromBlock(BasicBlock *RootBB) {
bool Changed;
+ Doms[RootBB].insert(RootBB); // Root always dominates itself...
do {
Changed = false;
DomSetType WorkingSet;
- df_iterator<Function*> It = df_begin(M), End = df_end(M);
+ df_iterator<BasicBlock*> It = df_begin(RootBB), End = df_end(RootBB);
for ( ; It != End; ++It) {
- const BasicBlock *BB = *It;
- pred_const_iterator PI = pred_begin(BB), PEnd = pred_end(BB);
+ BasicBlock *BB = *It;
+ pred_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
+ // Loop until we get to a predecessor that has had its 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.
+ // traversing the graph in DFO and have handled start nodes specially,
+ // except when there are unreachable blocks.
//
- 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);
- }
+ while (PI != PEnd && Doms[*PI].empty()) ++PI;
+ if (PI != PEnd) { // Not unreachable code case?
+ WorkingSet = Doms[*PI];
+
+ // Intersect all of the predecessor sets
+ for (++PI; PI != PEnd; ++PI) {
+ DomSetType &PredSet = Doms[*PI];
+ if (PredSet.size())
+ set_intersect(WorkingSet, PredSet);
+ }
+ }
+ } else {
+ assert(Roots.size() == 1 && BB == Roots[0] &&
+ "We got into unreachable code somehow!");
}
WorkingSet.insert(BB); // A block always dominates itself
DomSetType &BBSet = Doms[BB];
if (BBSet != WorkingSet) {
+ //assert(WorkingSet.size() > BBSet.size() && "Must only grow sets!");
BBSet.swap(WorkingSet); // Constant time operation!
Changed = true; // The sets changed.
}
} while (Changed);
}
-// Postdominator set constructor. This ctor converts the specified function to
-// only have a single exit node (return stmt), then calculates the post
-// dominance sets for the function.
+
+
+// runOnFunction - This method calculates the forward dominator sets for the
+// specified function.
//
-void cfg::DominatorSet::calcPostDominatorSet(Function *M) {
- // Since we require that the unify all exit nodes pass has been run, we know
- // that there can be at most one return instruction in the function left.
- // Get it.
- //
- Root = getAnalysis<UnifyMethodExitNodes>().getExitNode();
+bool DominatorSet::runOnFunction(Function &F) {
+ BasicBlock *Root = &F.getEntryBlock();
+ Roots.clear();
+ Roots.push_back(Root);
+ assert(pred_begin(Root) == pred_end(Root) &&
+ "Root node has predecessors in function!");
+ recalculate();
+ return false;
+}
- if (Root == 0) { // No exit node for the function? Postdomsets are all empty
- for (Function::const_iterator MI = M->begin(), ME = M->end(); MI!=ME; ++MI)
- Doms[*MI] = DomSetType();
- return;
- }
+void DominatorSet::recalculate() {
+ assert(Roots.size() == 1 && "DominatorSet should have single root block!");
+ Doms.clear(); // Reset from the last time we were run...
- bool Changed;
- do {
- Changed = false;
+ // Calculate dominator sets for the reachable basic blocks...
+ calculateDominatorsFromBlock(Roots[0]);
- set<const BasicBlock*> Visited;
- DomSetType WorkingSet;
- idf_iterator<BasicBlock*> 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];
-
- 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
- }
- } while (Changed);
+
+ // Loop through the function, ensuring that every basic block has at least an
+ // empty set of nodes. This is important for the case when there is
+ // unreachable blocks.
+ Function *F = Roots[0]->getParent();
+ for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) Doms[I];
}
-// getAnalysisUsage - This obviously provides a dominator set, but it also
-// uses the UnifyFunctionExitNodes pass if building post-dominators
-//
-void cfg::DominatorSet::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesAll();
- if (isPostDominator()) {
- AU.addProvided(PostDomID);
- AU.addRequired(UnifyMethodExitNodes::ID);
- } else {
- AU.addProvided(ID);
- }
+
+static std::ostream &operator<<(std::ostream &o,
+ const std::set<BasicBlock*> &BBs) {
+ for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
+ I != E; ++I)
+ if (*I)
+ WriteAsOperand(o, *I, false);
+ else
+ o << " <<exit node>>";
+ return o;
}
+void DominatorSetBase::print(std::ostream &o) const {
+ for (const_iterator I = begin(), E = end(); I != E; ++I) {
+ o << " DomSet For BB: ";
+ if (I->first)
+ WriteAsOperand(o, I->first, false);
+ else
+ o << " <<exit node>>";
+ o << " is:\t" << I->second << "\n";
+ }
+}
//===----------------------------------------------------------------------===//
// ImmediateDominators Implementation
//===----------------------------------------------------------------------===//
-AnalysisID cfg::ImmediateDominators::ID(AnalysisID::create<cfg::ImmediateDominators>());
-AnalysisID cfg::ImmediateDominators::PostDomID(AnalysisID::create<cfg::ImmediateDominators>());
+static RegisterAnalysis<ImmediateDominators>
+C("idom", "Immediate Dominators Construction", true);
// calcIDoms - Calculate the immediate dominator mapping, given a set of
// dominators for every basic block.
-void cfg::ImmediateDominators::calcIDoms(const DominatorSet &DS) {
+void ImmediateDominatorsBase::calcIDoms(const DominatorSetBase &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;
+ BasicBlock *BB = DI->first;
const DominatorSet::DomSetType &Dominators = DI->second;
unsigned DomSetSize = Dominators.size();
if (DomSetSize == 1) continue; // Root node... IDom = null
}
}
+void ImmediateDominatorsBase::print(std::ostream &o) const {
+ for (const_iterator I = begin(), E = end(); I != E; ++I) {
+ o << " Immediate Dominator For Basic Block:";
+ if (I->first)
+ WriteAsOperand(o, I->first, false);
+ else
+ o << " <<exit node>>";
+ o << " is:";
+ if (I->second)
+ WriteAsOperand(o, I->second, false);
+ else
+ o << " <<exit node>>";
+ o << "\n";
+ }
+ o << "\n";
+}
+
//===----------------------------------------------------------------------===//
// DominatorTree Implementation
//===----------------------------------------------------------------------===//
-AnalysisID cfg::DominatorTree::ID(AnalysisID::create<cfg::DominatorTree>());
-AnalysisID cfg::DominatorTree::PostDomID(AnalysisID::create<cfg::DominatorTree>());
+static RegisterAnalysis<DominatorTree>
+E("domtree", "Dominator Tree Construction", true);
-// DominatorTree::reset - Free all of the tree node memory.
+// DominatorTreeBase::reset - Free all of the tree node memory.
//
-void cfg::DominatorTree::reset() {
+void DominatorTreeBase::reset() {
for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
delete I->second;
Nodes.clear();
+ RootNode = 0;
}
+void DominatorTreeBase::Node::setIDom(Node *NewIDom) {
+ assert(IDom && "No immediate dominator?");
+ if (IDom != NewIDom) {
+ std::vector<Node*>::iterator I =
+ std::find(IDom->Children.begin(), IDom->Children.end(), this);
+ assert(I != IDom->Children.end() &&
+ "Not in immediate dominator children set!");
+ // I am no longer your child...
+ IDom->Children.erase(I);
+
+ // Switch to new dominator
+ IDom = NewIDom;
+ IDom->Children.push_back(this);
+ }
+}
-#if 0
-// Given immediate dominators, we can also calculate the dominator tree
-cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
- : DominatorBase(IDoms.getRoot()) {
- const Function *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_iterator<const Function*> 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];
+void DominatorTree::calculate(const DominatorSet &DS) {
+ assert(Roots.size() == 1 && "DominatorTree should have 1 root block!");
+ BasicBlock *Root = Roots[0];
+ Nodes[Root] = RootNode = new Node(Root, 0); // Add a node for the root...
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
- }
- }
-}
-#endif
-
-void cfg::DominatorTree::calculate(const DominatorSet &DS) {
- Nodes[Root] = new Node(Root, 0); // Add a node for the root...
-
- if (!isPostDominator()) {
- // Iterate over all nodes in depth first order...
- for (df_iterator<BasicBlock*> 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
- // function.
- //
- 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;
- }
- }
- }
- } else if (Root) {
- // Iterate over all nodes in depth first order...
- for (idf_iterator<BasicBlock*> 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
+ // Iterate over all nodes in depth first order...
+ for (df_iterator<BasicBlock*> I = df_begin(Root), E = df_end(Root);
+ I != E; ++I) {
+ 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 function.
+ // 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
+ // function.
+ //
+ 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...
//
- 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;
- }
+ 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;
}
}
}
}
+static std::ostream &operator<<(std::ostream &o,
+ const DominatorTreeBase::Node *Node) {
+ if (Node->getBlock())
+ WriteAsOperand(o, Node->getBlock(), false);
+ else
+ o << " <<exit node>>";
+ return o << "\n";
+}
+
+static void PrintDomTree(const DominatorTreeBase::Node *N, std::ostream &o,
+ unsigned Lev) {
+ o << std::string(2*Lev, ' ') << "[" << Lev << "] " << N;
+ for (DominatorTreeBase::Node::const_iterator I = N->begin(), E = N->end();
+ I != E; ++I)
+ PrintDomTree(*I, o, Lev+1);
+}
+
+void DominatorTreeBase::print(std::ostream &o) const {
+ o << "=============================--------------------------------\n"
+ << "Inorder Dominator Tree:\n";
+ PrintDomTree(getRootNode(), o, 1);
+}
+
//===----------------------------------------------------------------------===//
// DominanceFrontier Implementation
//===----------------------------------------------------------------------===//
-AnalysisID cfg::DominanceFrontier::ID(AnalysisID::create<cfg::DominanceFrontier>());
-AnalysisID cfg::DominanceFrontier::PostDomID(AnalysisID::create<cfg::DominanceFrontier>());
+static RegisterAnalysis<DominanceFrontier>
+G("domfrontier", "Dominance Frontier Construction", true);
-const cfg::DominanceFrontier::DomSetType &
-cfg::DominanceFrontier::calcDomFrontier(const DominatorTree &DT,
- const DominatorTree::Node *Node) {
+const DominanceFrontier::DomSetType &
+DominanceFrontier::calculate(const DominatorTree &DT,
+ const DominatorTree::Node *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 (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB);
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
SI != SE; ++SI) {
// Does Node immediately dominate this successor?
if (DT[*SI]->getIDom() != Node)
for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
NI != NE; ++NI) {
DominatorTree::Node *IDominee = *NI;
- const DomSetType &ChildDF = calcDomFrontier(DT, IDominee);
+ const DomSetType &ChildDF = calculate(DT, IDominee);
DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
for (; CDFI != CDFE; ++CDFI) {
return S;
}
-const cfg::DominanceFrontier::DomSetType &
-cfg::DominanceFrontier::calcPostDomFrontier(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...
- if (!Root) return S;
-
- 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);
+void DominanceFrontierBase::print(std::ostream &o) const {
+ for (const_iterator I = begin(), E = end(); I != E; ++I) {
+ o << " DomFrontier for BB";
+ if (I->first)
+ WriteAsOperand(o, I->first, false);
+ else
+ o << " <<exit node>>";
+ o << " is:\t" << I->second << "\n";
}
-
- // 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 = calcPostDomFrontier(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;
}
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