-//===- 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/Utils/UnifyFunctionExitNodes.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;
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
static RegisterAnalysis<DominatorSet>
-A("domset", "Dominator Set Construction");
-static RegisterAnalysis<PostDominatorSet>
-B("postdomset", "Post-Dominator Set Construction");
-
-AnalysisID DominatorSet::ID(AnalysisID::create<DominatorSet>(), true);
-AnalysisID PostDominatorSet::ID(AnalysisID::create<PostDominatorSet>(), true);
+A("domset", "Dominator Set Construction", true);
// dominates - Return true if A dominates B. This performs the special checks
// neccesary if A and B are in the same basic block.
return &*I == A;
}
-// runOnFunction - This method calculates the forward dominator sets for the
-// specified function.
-//
-bool DominatorSet::runOnFunction(Function &F) {
- Doms.clear(); // Reset from the last time we were run...
- Root = &F.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(&F), End = df_end(&F);
+ df_iterator<BasicBlock*> It = df_begin(RootBB), End = df_end(RootBB);
for ( ; It != End; ++It) {
BasicBlock *BB = *It;
pred_iterator PI = pred_begin(BB), PEnd = pred_end(BB);
// 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;
+ while (Doms[*PI].empty()) ++PI;
WorkingSet = Doms[*PI];
for (++PI; PI != PEnd; ++PI) { // Intersect all of the predecessor sets
WorkingSet.clear(); // Clear out the set for next iteration
}
} while (Changed);
- return false;
}
-// Postdominator set construction. This 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.
//
-bool PostDominatorSet::runOnFunction(Function &F) {
+bool DominatorSet::runOnFunction(Function &F) {
Doms.clear(); // Reset from the last time we were run...
- // 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<UnifyFunctionExitNodes>().getExitNode();
-
- if (Root == 0) { // No exit node for the function? Postdomsets are all empty
- for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
- Doms[FI] = DomSetType();
- return false;
- }
-
- bool Changed;
- do {
- Changed = false;
+ Root = &F.getEntryNode();
+ assert(pred_begin(Root) == pred_end(Root) &&
+ "Root node has predecessors in function!");
- set<const BasicBlock*> Visited;
- DomSetType WorkingSet;
- idf_iterator<BasicBlock*> It = idf_begin(Root), End = idf_end(Root);
- for ( ; It != End; ++It) {
- BasicBlock *BB = *It;
- succ_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];
+ // Calculate dominator sets for the reachable basic blocks...
+ calculateDominatorsFromBlock(Root);
- 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
+ // Every basic block in the function should at least dominate themselves, and
+ // thus every basic block should have an entry in Doms. The one case where we
+ // miss this is when a basic block is unreachable. To get these we now do an
+ // extra pass over the function, calculating dominator information for
+ // unreachable blocks.
+ //
+ for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
+ if (Doms[I].empty()) {
+ calculateDominatorsFromBlock(I);
}
- } while (Changed);
+
return false;
}
-// getAnalysisUsage - This obviously provides a post-dominator set, but it also
-// requires the UnifyFunctionExitNodes pass.
-//
-void PostDominatorSet::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesAll();
- AU.addProvided(ID);
- AU.addRequired(UnifyFunctionExitNodes::ID);
+
+static std::ostream &operator<<(std::ostream &o, const set<BasicBlock*> &BBs) {
+ for (set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
+ I != E; ++I) {
+ o << " ";
+ WriteAsOperand(o, *I, false);
+ o << "\n";
+ }
+ return o;
}
+void DominatorSetBase::print(std::ostream &o) const {
+ for (const_iterator I = begin(), E = end(); I != E; ++I)
+ o << "=============================--------------------------------\n"
+ << "\nDominator Set For Basic Block\n" << I->first
+ << "-------------------------------\n" << I->second << "\n";
+}
//===----------------------------------------------------------------------===//
// ImmediateDominators Implementation
//===----------------------------------------------------------------------===//
static RegisterAnalysis<ImmediateDominators>
-C("idom", "Immediate Dominators Construction");
-static RegisterAnalysis<ImmediatePostDominators>
-D("postidom", "Immediate Post-Dominators Construction");
-
-AnalysisID ImmediateDominators::ID(AnalysisID::create<ImmediateDominators>(), true);
-AnalysisID ImmediatePostDominators::ID(AnalysisID::create<ImmediatePostDominators>(), true);
+C("idom", "Immediate Dominators Construction", true);
// calcIDoms - Calculate the immediate dominator mapping, given a set of
// dominators for every basic block.
}
}
+void ImmediateDominatorsBase::print(std::ostream &o) const {
+ for (const_iterator I = begin(), E = end(); I != E; ++I)
+ o << "=============================--------------------------------\n"
+ << "\nImmediate Dominator For Basic Block\n" << *I->first
+ << "is: \n" << *I->second << "\n";
+}
+
//===----------------------------------------------------------------------===//
// DominatorTree Implementation
//===----------------------------------------------------------------------===//
static RegisterAnalysis<DominatorTree>
-E("domtree", "Dominator Tree Construction");
-static RegisterAnalysis<PostDominatorTree>
-F("postdomtree", "Post-Dominator Tree Construction");
-
-AnalysisID DominatorTree::ID(AnalysisID::create<DominatorTree>(), true);
-AnalysisID PostDominatorTree::ID(AnalysisID::create<PostDominatorTree>(), true);
+E("domtree", "Dominator Tree Construction", true);
// DominatorTreeBase::reset - Free all of the tree node memory.
//
}
-void PostDominatorTree::calculate(const PostDominatorSet &DS) {
- Nodes[Root] = new Node(Root, 0); // Add a node for the root...
+static std::ostream &operator<<(std::ostream &o,
+ const DominatorTreeBase::Node *Node) {
+ return o << Node->getNode()
+ << "\n------------------------------------------\n";
+}
- 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) {
- 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;
- }
- }
- }
+static void PrintDomTree(const DominatorTreeBase::Node *N, std::ostream &o,
+ unsigned Lev) {
+ o << "Level #" << 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(Nodes.find(getRoot())->second, o, 1);
+}
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
static RegisterAnalysis<DominanceFrontier>
-G("domfrontier", "Dominance Frontier Construction");
-static RegisterAnalysis<PostDominanceFrontier>
-H("postdomfrontier", "Post-Dominance Frontier Construction");
-
-AnalysisID DominanceFrontier::ID(AnalysisID::create<DominanceFrontier>(), true);
-AnalysisID PostDominanceFrontier::ID(AnalysisID::create<PostDominanceFrontier>(), true);
+G("domfrontier", "Dominance Frontier Construction", true);
const DominanceFrontier::DomSetType &
DominanceFrontier::calculate(const DominatorTree &DT,
return S;
}
-const DominanceFrontier::DomSetType &
-PostDominanceFrontier::calculate(const PostDominatorTree &DT,
- const DominatorTree::Node *Node) {
- // Loop over CFG successors to calculate DFlocal[Node]
- BasicBlock *BB = Node->getNode();
- DomSetType &S = Frontiers[BB]; // The new set to fill in...
- if (!Root) return S;
-
- for (pred_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);
- }
-
- // 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 (PostDominatorTree::Node::const_iterator
- NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
- DominatorTree::Node *IDominee = *NI;
- const DomSetType &ChildDF = calculate(DT, IDominee);
-
- DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
- for (; CDFI != CDFE; ++CDFI) {
- if (!Node->dominates(DT[*CDFI]))
- S.insert(*CDFI);
- }
+void DominanceFrontierBase::print(std::ostream &o) const {
+ for (const_iterator I = begin(), E = end(); I != E; ++I) {
+ o << "=============================--------------------------------\n"
+ << "\nDominance Frontier For Basic Block\n";
+ WriteAsOperand(o, I->first, false);
+ o << " is: \n" << I->second << "\n";
}
-
- return S;
}
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