-//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
+//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
+//
+// The LLVM Compiler Infrastructure
//
-// This file provides a simple class to calculate the dominator set of a
-// function.
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the post-dominator construction algorithms.
//
//===----------------------------------------------------------------------===//
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
+#include "llvm/Analysis/PostDominators.h"
+#include "llvm/Instructions.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;
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SetOperations.h"
+using namespace llvm;
//===----------------------------------------------------------------------===//
-// DominatorSet Implementation
+// PostDominatorSet Implementation
//===----------------------------------------------------------------------===//
-static RegisterAnalysis<DominatorSet>
-A("domset", "Dominator Set Construction");
static RegisterAnalysis<PostDominatorSet>
-B("postdomset", "Post-Dominator Set Construction");
-
-AnalysisID DominatorSet::ID = A;
-AnalysisID PostDominatorSet::ID = B;
-
-// dominates - Return true if A dominates B. This performs the special checks
-// neccesary 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;
-}
-
-// 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!");
-
- bool Changed;
- do {
- Changed = false;
-
- DomSetType WorkingSet;
- df_iterator<Function*> It = df_begin(&F), End = df_end(&F);
- for ( ; It != End; ++It) {
- 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
- // 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 predecessor 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);
- return false;
-}
-
+B("postdomset", "Post-Dominator Set Construction", true);
// Postdominator set construction. This converts the specified function to only
// have a single exit node (return stmt), then calculates the post dominance
//
bool PostDominatorSet::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;
+ // Scan the function looking for the root nodes of the post-dominance
+ // relationships. These blocks end with return and unwind instructions.
+ // While we are iterating over the function, we also initialize all of the
+ // domsets to empty.
+ Roots.clear();
+ for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
+ Doms[I]; // Initialize to empty
+
+ if (succ_begin(I) == succ_end(I))
+ Roots.push_back(I);
}
+ // If there are no exit nodes for the function, postdomsets are all empty.
+ // This can happen if the function just contains an infinite loop, for
+ // example.
+ if (Roots.empty()) return false;
+
+ // If we have more than one root, we insert an artificial "null" exit, which
+ // has "virtual edges" to each of the real exit nodes.
+ if (Roots.size() > 1)
+ Doms[0].insert(0);
+
bool Changed;
do {
Changed = false;
- set<const BasicBlock*> Visited;
+ std::set<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];
-
- for (++PI; PI != PEnd; ++PI) { // Intersect all of the successor sets
- DomSetType &PredSet = Doms[*PI];
- if (PredSet.size())
- set_intersect(WorkingSet, PredSet);
- }
- }
+
+ for (unsigned i = 0, e = Roots.size(); i != e; ++i)
+ for (idf_ext_iterator<BasicBlock*> It = idf_ext_begin(Roots[i], Visited),
+ E = idf_ext_end(Roots[i], Visited); It != E; ++It) {
+ BasicBlock *BB = *It;
+ succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
+ if (SI != SE) { // Is there SOME successor?
+ // 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[*SI].size() == 0) ++SI;
+ WorkingSet = Doms[*SI];
+
+ for (++SI; SI != SE; ++SI) { // Intersect all of the successor sets
+ DomSetType &SuccSet = Doms[*SI];
+ if (SuccSet.size())
+ set_intersect(WorkingSet, SuccSet);
+ }
+ } else {
+ // If this node has no successors, it must be one of the root nodes.
+ // We will already take care of the notion that the node
+ // post-dominates itself. The only thing we have to add is that if
+ // there are multiple root nodes, we want to insert a special "null"
+ // exit node which dominates the roots as well.
+ if (Roots.size() > 1)
+ WorkingSet.insert(0);
+ }
- 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.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
}
- WorkingSet.clear(); // Clear out the set for next iteration
- }
} 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 ostream &operator<<(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
+// ImmediatePostDominators Implementation
//===----------------------------------------------------------------------===//
-static RegisterAnalysis<ImmediateDominators>
-C("idom", "Immediate Dominators Construction");
static RegisterAnalysis<ImmediatePostDominators>
-D("postidom", "Immediate Post-Dominators Construction");
+D("postidom", "Immediate Post-Dominators Construction", true);
-AnalysisID ImmediateDominators::ID = C;
-AnalysisID ImmediatePostDominators::ID = D;
// calcIDoms - Calculate the immediate dominator mapping, given a set of
// dominators for every basic block.
-void ImmediateDominatorsBase::calcIDoms(const DominatorSetBase &DS) {
+void ImmediatePostDominators::calcIDoms(const DominatorSetBase &DS) {
// Loop over all of the nodes that have dominators... figuring out the IDOM
// for each node...
//
}
}
-void ImmediateDominatorsBase::print(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
+// PostDominatorTree Implementation
//===----------------------------------------------------------------------===//
-static RegisterAnalysis<DominatorTree>
-E("domtree", "Dominator Tree Construction");
static RegisterAnalysis<PostDominatorTree>
-F("postdomtree", "Post-Dominator Tree Construction");
-
-AnalysisID DominatorTree::ID = E;
-AnalysisID PostDominatorTree::ID = F;
-
-// DominatorTreeBase::reset - Free all of the tree node memory.
-//
-void DominatorTreeBase::reset() {
- for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
- delete I->second;
- Nodes.clear();
-}
+F("postdomtree", "Post-Dominator Tree Construction", true);
+void PostDominatorTree::calculate(const PostDominatorSet &DS) {
+ if (Roots.empty()) return;
+ BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
-void DominatorTree::calculate(const DominatorSet &DS) {
- Nodes[Root] = new Node(Root, 0); // Add a node for the root...
+ Nodes[Root] = RootNode = new Node(Root, 0); // Add a node for the root...
// 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.
- //
- 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;
- }
- }
- }
-}
-
-
-void PostDominatorTree::calculate(const PostDominatorSet &DS) {
- Nodes[Root] = new Node(Root, 0); // Add a node for the root...
-
- 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) {
+ for (unsigned i = 0, e = Roots.size(); i != e; ++i)
+ for (idf_iterator<BasicBlock*> I = idf_begin(Roots[i]),
+ E = idf_end(Roots[i]); 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
-
+
+ // If we have already computed the immediate dominator for this node,
+ // don't revisit. This can happen due to nodes reachable from multiple
+ // roots, but which the idf_iterator doesn't know about.
+ if (Nodes.find(BB) != Nodes.end()) continue;
+
// 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
// 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?");
+ for (DominatorSet::DomSetType::const_iterator I = Dominators.begin(),
+ E = Dominators.end(); I != E; ++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;
- }
+ // 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 ostream &operator<<(ostream &o, const DominatorTreeBase::Node *Node) {
- return o << Node->getNode()
- << "\n------------------------------------------\n";
-}
-
-static void PrintDomTree(const DominatorTreeBase::Node *N, 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);
-}
-
-
//===----------------------------------------------------------------------===//
-// DominanceFrontier Implementation
+// PostDominanceFrontier Implementation
//===----------------------------------------------------------------------===//
-static RegisterAnalysis<DominanceFrontier>
-G("domfrontier", "Dominance Frontier Construction");
static RegisterAnalysis<PostDominanceFrontier>
-H("postdomfrontier", "Post-Dominance Frontier Construction");
-
-AnalysisID DominanceFrontier::ID = G;
-AnalysisID PostDominanceFrontier::ID = H;
-
-const DominanceFrontier::DomSetType &
-DominanceFrontier::calculate(const DominatorTree &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...
-
- 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)
- 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 (DominatorTree::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);
- }
- }
-
- return S;
-}
+H("postdomfrontier", "Post-Dominance Frontier Construction", true);
const DominanceFrontier::DomSetType &
PostDominanceFrontier::calculate(const PostDominatorTree &DT,
const DominatorTree::Node *Node) {
// Loop over CFG successors to calculate DFlocal[Node]
- BasicBlock *BB = Node->getNode();
+ BasicBlock *BB = Node->getBlock();
DomSetType &S = Frontiers[BB]; // The new set to fill in...
- if (!Root) return S;
+ if (getRoots().empty()) 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);
- }
+ if (BB)
+ for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
+ SI != SE; ++SI)
+ // Does Node immediately dominate this predecessor?
+ 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
return S;
}
-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";
- }
+// stub - a dummy function to make linking work ok.
+void PostDominanceFrontier::stub() {
}
+
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