-//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
+//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
//
-// This file provides a simple class to calculate the dominator set of a method.
+// This file implements the post-dominator construction algorithms.
//
//===----------------------------------------------------------------------===//
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/Analysis/SimplifyCFG.h" // To get cfg::UnifyAllExitNodes
-#include "llvm/Support/DepthFirstIterator.h"
-#include "llvm/Support/STLExtras.h"
-#include "llvm/Method.h"
-#include <algorithm>
+#include "llvm/Analysis/PostDominators.h"
+#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
+#include "llvm/Support/CFG.h"
+#include "Support/DepthFirstIterator.h"
+#include "Support/SetOperations.h"
+using std::set;
//===----------------------------------------------------------------------===//
-// Helper Template
+// PostDominatorSet Implementation
//===----------------------------------------------------------------------===//
-// set_intersect - Identical to set_intersection, except that it works on
-// set<>'s and is nicer to use. Functionally, this iterates through S1,
-// removing elements that are not contained in S2.
-//
-template <class Ty, class Ty2>
-void set_intersect(set<Ty> &S1, const set<Ty2> &S2) {
- for (typename set<Ty>::iterator I = S1.begin(); I != S1.end();) {
- const Ty &E = *I;
- ++I;
- if (!S2.count(E)) S1.erase(E); // Erase element if not in S2
- }
-}
-
-//===----------------------------------------------------------------------===//
-// DominatorBase Implementation
-//===----------------------------------------------------------------------===//
-
-bool cfg::DominatorBase::isPostDominator() const {
- // Root can be null if there is no exit node from the CFG and is postdom set
- return Root == 0 || Root != Root->getParent()->front();
-}
+static RegisterAnalysis<PostDominatorSet>
+B("postdomset", "Post-Dominator Set Construction", true);
-
-//===----------------------------------------------------------------------===//
-// DominatorSet Implementation
-//===----------------------------------------------------------------------===//
-
-// DominatorSet ctor - Build either the dominator set or the post-dominator
-// set for a method...
+// 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.
//
-cfg::DominatorSet::DominatorSet(const Method *M) : DominatorBase(M->front()) {
- calcForwardDominatorSet(M);
-}
-
-// calcForwardDominatorSet - This method calculates the forward dominator sets
-// for the specified method.
-//
-void cfg::DominatorSet::calcForwardDominatorSet(const Method *M) {
- assert(Root && M && "Can't build dominator set of null method!");
- assert(Root->pred_begin() == Root->pred_end() &&
- "Root node has predecessors in method!");
-
- bool Changed;
- do {
- Changed = false;
-
- DomSetType WorkingSet;
- df_iterator<const Method*> It = df_begin(M), End = df_end(M);
- for ( ; It != End; ++It) {
- const BasicBlock *BB = *It;
- BasicBlock::pred_const_iterator PI = BB->pred_begin(),
- PEnd = BB->pred_end();
- 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);
-}
-
-// Postdominator set constructor. This ctor converts the specified method to
-// only have a single exit node (return stmt), then calculates the post
-// dominance sets for the method.
-//
-cfg::DominatorSet::DominatorSet(Method *M, bool PostDomSet)
- : DominatorBase(M->front()) {
- if (!PostDomSet) { calcForwardDominatorSet(M); return; }
+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();
- Root = cfg::UnifyAllExitNodes(M);
- if (Root == 0) { // No exit node for the method? Postdomsets are all empty
- for (Method::iterator MI = M->begin(), ME = M->end(); MI != ME; ++MI)
- Doms[*MI] = DomSetType();
- return;
+ 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;
set<const BasicBlock*> Visited;
DomSetType WorkingSet;
- idf_iterator<const BasicBlock*> It = idf_begin(Root), End = idf_end(Root);
+ idf_iterator<BasicBlock*> It = idf_begin(Root), End = idf_end(Root);
for ( ; It != End; ++It) {
- const BasicBlock *BB = *It;
- BasicBlock::succ_const_iterator PI = BB->succ_begin(),
- PEnd = BB->succ_end();
+ 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
if (PredSet.size())
set_intersect(WorkingSet, PredSet);
}
+ } else if (BB != Root) {
+ // If this isn't the root basic block and it has no successors, it must
+ // be an non-returning block. Fib a bit by saying that the root node
+ // postdominates this unreachable node. This isn't exactly true,
+ // because there is no path from this node to the root node, but it is
+ // sorta true because any paths to the exit node would have to go
+ // through this node.
+ //
+ // This allows for postdominator properties to be built for code that
+ // doesn't return in a reasonable manner.
+ //
+ WorkingSet = Doms[Root];
}
WorkingSet.insert(BB); // A block always dominates itself
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.addRequired<UnifyFunctionExitNodes>();
+}
//===----------------------------------------------------------------------===//
-// ImmediateDominators Implementation
+// ImmediatePostDominators Implementation
//===----------------------------------------------------------------------===//
-// calcIDoms - Calculate the immediate dominator mapping, given a set of
-// dominators for every basic block.
-void cfg::ImmediateDominators::calcIDoms(const DominatorSet &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;
- const DominatorSet::DomSetType &Dominators = DI->second;
- 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!
- //
- 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) {
- IDoms[BB] = *I;
- break;
- }
- }
- }
-}
-
+static RegisterAnalysis<ImmediatePostDominators>
+D("postidom", "Immediate Post-Dominators Construction", true);
//===----------------------------------------------------------------------===//
-// DominatorTree Implementation
+// PostDominatorTree Implementation
//===----------------------------------------------------------------------===//
-// DominatorTree dtor - Free all of the tree node memory.
-//
-cfg::DominatorTree::~DominatorTree() {
- for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
- delete I->second;
-}
-
+static RegisterAnalysis<PostDominatorTree>
+F("postdomtree", "Post-Dominator Tree Construction", true);
-cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
- : DominatorBase(IDoms.getRoot()) {
- const Method *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 Method*> 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];
-
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
- }
- }
-}
-
-void cfg::DominatorTree::calculate(const DominatorSet &DS) {
+void PostDominatorTree::calculate(const PostDominatorSet &DS) {
Nodes[Root] = new Node(Root, 0); // Add a node for the root...
- if (!isPostDominator()) {
+ if (Root) {
// Iterate over all nodes in depth first order...
- for (df_iterator<const BasicBlock*> I = df_begin(Root), E = df_end(Root);
+ 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
-
- // 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
- // method.
- //
- 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<const BasicBlock*> I = idf_begin(Root), E = idf_end(Root);
- I != E; ++I) {
- const BasicBlock *BB = *I;
+ BasicBlock *BB = *I;
const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
unsigned DomSetSize = Dominators.size();
if (DomSetSize == 1) continue; // Root node... IDom = null
// 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 method.
+ // 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
+ // 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) {
}
}
-
-
//===----------------------------------------------------------------------===//
-// DominanceFrontier Implementation
+// PostDominanceFrontier Implementation
//===----------------------------------------------------------------------===//
-const cfg::DominanceFrontier::DomSetType &
-cfg::DominanceFrontier::calcDomFrontier(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...
-
- for (BasicBlock::succ_const_iterator SI = BB->succ_begin(),
- SE = BB->succ_end(); 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 = calcDomFrontier(DT, IDominee);
-
- DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
- for (; CDFI != CDFE; ++CDFI) {
- if (!Node->dominates(DT[*CDFI]))
- S.insert(*CDFI);
- }
- }
+static RegisterAnalysis<PostDominanceFrontier>
+H("postdomfrontier", "Post-Dominance Frontier Construction", true);
- return S;
-}
-
-const cfg::DominanceFrontier::DomSetType &
-cfg::DominanceFrontier::calcPostDomFrontier(const DominatorTree &DT,
- const DominatorTree::Node *Node) {
+const DominanceFrontier::DomSetType &
+PostDominanceFrontier::calculate(const PostDominatorTree &DT,
+ const DominatorTree::Node *Node) {
// Loop over CFG successors to calculate DFlocal[Node]
- const BasicBlock *BB = Node->getNode();
+ BasicBlock *BB = Node->getNode();
DomSetType &S = Frontiers[BB]; // The new set to fill in...
if (!Root) return S;
- for (BasicBlock::pred_const_iterator SI = BB->pred_begin(),
- SE = BB->pred_end(); SI != SE; ++SI) {
+ 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);
// 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) {
+ for (PostDominatorTree::Node::const_iterator
+ NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
DominatorTree::Node *IDominee = *NI;
- const DomSetType &ChildDF = calcPostDomFrontier(DT, IDominee);
+ const DomSetType &ChildDF = calculate(DT, IDominee);
DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
for (; CDFI != CDFE; ++CDFI) {
return S;
}
+
+// stub - a dummy function to make linking work ok.
+void PostDominanceFrontier::stub() {
+}
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