lib/Analysis/PostDominators.cpp - llvm - Git at Google

 //===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // 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/PostDominators.h"
 #include "llvm/Instructions.h"
 #include "llvm/Support/CFG.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/SetOperations.h"
 using namespace llvm;

 //===----------------------------------------------------------------------===//
 //  PostDominatorTree Implementation
 //===----------------------------------------------------------------------===//

 char PostDominatorTree::ID = 0;
 char PostDominanceFrontier::ID = 0;
 char PostETForest::ID = 0;
 static RegisterPass<PostDominatorTree>
 F("postdomtree", "Post-Dominator Tree Construction", true);

 unsigned PostDominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
                                           unsigned N) {
   std::vector<std::pair<BasicBlock *, InfoRec *> > workStack;
   std::set<BasicBlock *> visited;
   workStack.push_back(std::make_pair(V, &VInfo));

   do {
     BasicBlock *currentBB = workStack.back().first;
     InfoRec *currentVInfo = workStack.back().second;

     // Visit each block only once.
     if (visited.count(currentBB) == 0) {

       visited.insert(currentBB);
       currentVInfo->Semi = ++N;
       currentVInfo->Label = currentBB;

       Vertex.push_back(currentBB);  // Vertex[n] = current;
       // Info[currentBB].Ancestor = 0;
       // Ancestor[n] = 0
       // Child[currentBB] = 0;
       currentVInfo->Size = 1;       // Size[currentBB] = 1
     }

     // Visit children
     bool visitChild = false;
     for (pred_iterator PI = pred_begin(currentBB), PE = pred_end(currentBB);
          PI != PE && !visitChild; ++PI) {
       InfoRec &SuccVInfo = Info[*PI];
       if (SuccVInfo.Semi == 0) {
         SuccVInfo.Parent = currentBB;
         if (visited.count (*PI) == 0) {
           workStack.push_back(std::make_pair(*PI, &SuccVInfo));
           visitChild = true;
         }
       }
     }

     // If all children are visited or if this block has no child then pop this
     // block out of workStack.
     if (!visitChild)
       workStack.pop_back();

   } while (!workStack.empty());

   return N;
 }

 void PostDominatorTree::Compress(BasicBlock *V, InfoRec &VInfo) {
   BasicBlock *VAncestor = VInfo.Ancestor;
   InfoRec &VAInfo = Info[VAncestor];
   if (VAInfo.Ancestor == 0)
     return;

   Compress(VAncestor, VAInfo);

   BasicBlock *VAncestorLabel = VAInfo.Label;
   BasicBlock *VLabel = VInfo.Label;
   if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
     VInfo.Label = VAncestorLabel;

   VInfo.Ancestor = VAInfo.Ancestor;
 }

 BasicBlock *PostDominatorTree::Eval(BasicBlock *V) {
   InfoRec &VInfo = Info[V];

   // Higher-complexity but faster implementation
   if (VInfo.Ancestor == 0)
     return V;
   Compress(V, VInfo);
   return VInfo.Label;
 }

 void PostDominatorTree::Link(BasicBlock *V, BasicBlock *W,
                                    InfoRec &WInfo) {
   // Higher-complexity but faster implementation
   WInfo.Ancestor = V;
 }

 void PostDominatorTree::calculate(Function &F) {
   // Step #0: Scan the function looking for the root nodes of the post-dominance
   // relationships.  These blocks, which have no successors, end with return and
   // unwind instructions.
   for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
     if (succ_begin(I) == succ_end(I))
       Roots.push_back(I);

   Vertex.push_back(0);

   // Step #1: Number blocks in depth-first order and initialize variables used
   // in later stages of the algorithm.
   unsigned N = 0;
   for (unsigned i = 0, e = Roots.size(); i != e; ++i)
     N = DFSPass(Roots[i], Info[Roots[i]], N);

   for (unsigned i = N; i >= 2; --i) {
     BasicBlock *W = Vertex[i];
     InfoRec &WInfo = Info[W];

     // Step #2: Calculate the semidominators of all vertices
     for (succ_iterator SI = succ_begin(W), SE = succ_end(W); SI != SE; ++SI)
       if (Info.count(*SI)) {  // Only if this predecessor is reachable!
         unsigned SemiU = Info[Eval(*SI)].Semi;
         if (SemiU < WInfo.Semi)
           WInfo.Semi = SemiU;
       }

     Info[Vertex[WInfo.Semi]].Bucket.push_back(W);

     BasicBlock *WParent = WInfo.Parent;
     Link(WParent, W, WInfo);

     // Step #3: Implicitly define the immediate dominator of vertices
     std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
     while (!WParentBucket.empty()) {
       BasicBlock *V = WParentBucket.back();
       WParentBucket.pop_back();
       BasicBlock *U = Eval(V);
       IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
     }
   }

   // Step #4: Explicitly define the immediate dominator of each vertex
   for (unsigned i = 2; i <= N; ++i) {
     BasicBlock *W = Vertex[i];
     BasicBlock *&WIDom = IDoms[W];
     if (WIDom != Vertex[Info[W].Semi])
       WIDom = IDoms[WIDom];
   }

   if (Roots.empty()) return;

   // Add a node for the root.  This node might be the actual root, if there is
   // one exit block, or it may be the virtual exit (denoted by (BasicBlock *)0)
   // which postdominates all real exits if there are multiple exit blocks.
   BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
   Nodes[Root] = RootNode = new Node(Root, 0);

   // Loop over all of the reachable blocks in the function...
   for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
     if (BasicBlock *ImmPostDom = getIDom(I)) {  // Reachable block.
       Node *&BBNode = Nodes[I];
       if (!BBNode) {  // Haven't calculated this node yet?
                       // Get or calculate the node for the immediate dominator
         Node *IPDomNode = getNodeForBlock(ImmPostDom);

         // Add a new tree node for this BasicBlock, and link it as a child of
         // IDomNode
         BBNode = IPDomNode->addChild(new Node(I, IPDomNode));
       }
     }

   // Free temporary memory used to construct idom's
   IDoms.clear();
   Info.clear();
   std::vector<BasicBlock*>().swap(Vertex);
 }


 DominatorTreeBase::Node *PostDominatorTree::getNodeForBlock(BasicBlock *BB) {
   Node *&BBNode = Nodes[BB];
   if (BBNode) return BBNode;

   // Haven't calculated this node yet?  Get or calculate the node for the
   // immediate postdominator.
   BasicBlock *IPDom = getIDom(BB);
   Node *IPDomNode = getNodeForBlock(IPDom);

   // Add a new tree node for this BasicBlock, and link it as a child of
   // IDomNode
   return BBNode = IPDomNode->addChild(new Node(BB, IPDomNode));
 }

 //===----------------------------------------------------------------------===//
 // PostETForest Implementation
 //===----------------------------------------------------------------------===//

 static RegisterPass<PostETForest>
 G("postetforest", "Post-ET-Forest Construction", true);

 ETNode *PostETForest::getNodeForBlock(BasicBlock *BB) {
   ETNode *&BBNode = Nodes[BB];
   if (BBNode) return BBNode;

   // Haven't calculated this node yet?  Get or calculate the node for the
   // immediate dominator.
   PostDominatorTree::Node *node = getAnalysis<PostDominatorTree>().getNode(BB);

   // If we are unreachable, we may not have an immediate dominator.
   if (!node)
     return 0;
   else if (!node->getIDom())
     return BBNode = new ETNode(BB);
   else {
     ETNode *IDomNode = getNodeForBlock(node->getIDom()->getBlock());

     // Add a new tree node for this BasicBlock, and link it as a child of
     // IDomNode
     BBNode = new ETNode(BB);
     BBNode->setFather(IDomNode);
     return BBNode;
   }
 }

 void PostETForest::calculate(const PostDominatorTree &DT) {
   for (unsigned i = 0, e = Roots.size(); i != e; ++i)
     Nodes[Roots[i]] = new ETNode(Roots[i]); // Add a node for the root

   // Iterate over all nodes in inverse depth first order.
   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;
     ETNode *&BBNode = Nodes[BB];
     if (!BBNode) {
       ETNode *IDomNode =  NULL;
       PostDominatorTree::Node *node = DT.getNode(BB);
       if (node && node->getIDom())
         IDomNode = getNodeForBlock(node->getIDom()->getBlock());

       // Add a new ETNode for this BasicBlock, and set it's parent
       // to it's immediate dominator.
       BBNode = new ETNode(BB);
       if (IDomNode)
         BBNode->setFather(IDomNode);
     }
   }

   int dfsnum = 0;
   // Iterate over all nodes in depth first order...
   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) {
         if (!getNodeForBlock(*I)->hasFather())
           getNodeForBlock(*I)->assignDFSNumber(dfsnum);
     }
   DFSInfoValid = true;
 }

 //===----------------------------------------------------------------------===//
 //  PostDominanceFrontier Implementation
 //===----------------------------------------------------------------------===//

 static RegisterPass<PostDominanceFrontier>
 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->getBlock();
   DomSetType &S = Frontiers[BB];       // The new set to fill in...
   if (getRoots().empty()) return S;

   if (BB)
     for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
          SI != SE; ++SI) {
       // Does Node immediately dominate this predecessor?
       DominatorTree::Node *SINode = DT[*SI];
       if (SINode && SINode->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->properlyDominates(DT[*CDFI]))
         S.insert(*CDFI);
     }
   }

   return S;
 }

 // Ensure that this .cpp file gets linked when PostDominators.h is used.
 DEFINING_FILE_FOR(PostDominanceFrontier)
	//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// 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/PostDominators.h"
	#include "llvm/Instructions.h"
	#include "llvm/Support/CFG.h"
	#include "llvm/ADT/DepthFirstIterator.h"
	#include "llvm/ADT/SetOperations.h"
	using namespace llvm;

	//===----------------------------------------------------------------------===//
	// PostDominatorTree Implementation
	//===----------------------------------------------------------------------===//

	char PostDominatorTree::ID = 0;
	char PostDominanceFrontier::ID = 0;
	char PostETForest::ID = 0;
	static RegisterPass<PostDominatorTree>
	F("postdomtree", "Post-Dominator Tree Construction", true);

	unsigned PostDominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
	unsigned N) {
	std::vector<std::pair<BasicBlock , InfoRec > > workStack;
	std::set<BasicBlock *> visited;
	workStack.push_back(std::make_pair(V, &VInfo));

	do {
	BasicBlock *currentBB = workStack.back().first;
	InfoRec *currentVInfo = workStack.back().second;

	// Visit each block only once.
	if (visited.count(currentBB) == 0) {

	visited.insert(currentBB);
	currentVInfo->Semi = ++N;
	currentVInfo->Label = currentBB;

	Vertex.push_back(currentBB); // Vertex[n] = current;
	// Info[currentBB].Ancestor = 0;
	// Ancestor[n] = 0
	// Child[currentBB] = 0;
	currentVInfo->Size = 1; // Size[currentBB] = 1
	}

	// Visit children
	bool visitChild = false;
	for (pred_iterator PI = pred_begin(currentBB), PE = pred_end(currentBB);
	PI != PE && !visitChild; ++PI) {
	InfoRec &SuccVInfo = Info[*PI];
	if (SuccVInfo.Semi == 0) {
	SuccVInfo.Parent = currentBB;
	if (visited.count (*PI) == 0) {
	workStack.push_back(std::make_pair(*PI, &SuccVInfo));
	visitChild = true;
	}
	}
	}

	// If all children are visited or if this block has no child then pop this
	// block out of workStack.
	if (!visitChild)
	workStack.pop_back();

	} while (!workStack.empty());

	return N;
	}

	void PostDominatorTree::Compress(BasicBlock *V, InfoRec &VInfo) {
	BasicBlock *VAncestor = VInfo.Ancestor;
	InfoRec &VAInfo = Info[VAncestor];
	if (VAInfo.Ancestor == 0)
	return;

	Compress(VAncestor, VAInfo);

	BasicBlock *VAncestorLabel = VAInfo.Label;
	BasicBlock *VLabel = VInfo.Label;
	if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
	VInfo.Label = VAncestorLabel;

	VInfo.Ancestor = VAInfo.Ancestor;
	}

	BasicBlock PostDominatorTree::Eval(BasicBlock V) {
	InfoRec &VInfo = Info[V];

	// Higher-complexity but faster implementation
	if (VInfo.Ancestor == 0)
	return V;
	Compress(V, VInfo);
	return VInfo.Label;
	}

	void PostDominatorTree::Link(BasicBlock V, BasicBlock W,
	InfoRec &WInfo) {
	// Higher-complexity but faster implementation
	WInfo.Ancestor = V;
	}

	void PostDominatorTree::calculate(Function &F) {
	// Step #0: Scan the function looking for the root nodes of the post-dominance
	// relationships. These blocks, which have no successors, end with return and
	// unwind instructions.
	for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
	if (succ_begin(I) == succ_end(I))
	Roots.push_back(I);

	Vertex.push_back(0);

	// Step #1: Number blocks in depth-first order and initialize variables used
	// in later stages of the algorithm.
	unsigned N = 0;
	for (unsigned i = 0, e = Roots.size(); i != e; ++i)
	N = DFSPass(Roots[i], Info[Roots[i]], N);

	for (unsigned i = N; i >= 2; --i) {
	BasicBlock *W = Vertex[i];
	InfoRec &WInfo = Info[W];

	// Step #2: Calculate the semidominators of all vertices
	for (succ_iterator SI = succ_begin(W), SE = succ_end(W); SI != SE; ++SI)
	if (Info.count(*SI)) { // Only if this predecessor is reachable!
	unsigned SemiU = Info[Eval(*SI)].Semi;
	if (SemiU < WInfo.Semi)
	WInfo.Semi = SemiU;
	}

	Info[Vertex[WInfo.Semi]].Bucket.push_back(W);

	BasicBlock *WParent = WInfo.Parent;
	Link(WParent, W, WInfo);

	// Step #3: Implicitly define the immediate dominator of vertices
	std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
	while (!WParentBucket.empty()) {
	BasicBlock *V = WParentBucket.back();
	WParentBucket.pop_back();
	BasicBlock *U = Eval(V);
	IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
	}
	}

	// Step #4: Explicitly define the immediate dominator of each vertex
	for (unsigned i = 2; i <= N; ++i) {
	BasicBlock *W = Vertex[i];
	BasicBlock *&WIDom = IDoms[W];
	if (WIDom != Vertex[Info[W].Semi])
	WIDom = IDoms[WIDom];
	}

	if (Roots.empty()) return;

	// Add a node for the root. This node might be the actual root, if there is
	// one exit block, or it may be the virtual exit (denoted by (BasicBlock *)0)
	// which postdominates all real exits if there are multiple exit blocks.
	BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
	Nodes[Root] = RootNode = new Node(Root, 0);

	// Loop over all of the reachable blocks in the function...
	for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
	if (BasicBlock *ImmPostDom = getIDom(I)) { // Reachable block.
	Node *&BBNode = Nodes[I];
	if (!BBNode) { // Haven't calculated this node yet?
	// Get or calculate the node for the immediate dominator
	Node *IPDomNode = getNodeForBlock(ImmPostDom);

	// Add a new tree node for this BasicBlock, and link it as a child of
	// IDomNode
	BBNode = IPDomNode->addChild(new Node(I, IPDomNode));
	}
	}

	// Free temporary memory used to construct idom's
	IDoms.clear();
	Info.clear();
	std::vector<BasicBlock*>().swap(Vertex);
	}


	DominatorTreeBase::Node PostDominatorTree::getNodeForBlock(BasicBlock BB) {
	Node *&BBNode = Nodes[BB];
	if (BBNode) return BBNode;

	// Haven't calculated this node yet? Get or calculate the node for the
	// immediate postdominator.
	BasicBlock *IPDom = getIDom(BB);
	Node *IPDomNode = getNodeForBlock(IPDom);

	// Add a new tree node for this BasicBlock, and link it as a child of
	// IDomNode
	return BBNode = IPDomNode->addChild(new Node(BB, IPDomNode));
	}

	//===----------------------------------------------------------------------===//
	// PostETForest Implementation
	//===----------------------------------------------------------------------===//

	static RegisterPass<PostETForest>
	G("postetforest", "Post-ET-Forest Construction", true);

	ETNode PostETForest::getNodeForBlock(BasicBlock BB) {
	ETNode *&BBNode = Nodes[BB];
	if (BBNode) return BBNode;

	// Haven't calculated this node yet? Get or calculate the node for the
	// immediate dominator.
	PostDominatorTree::Node *node = getAnalysis<PostDominatorTree>().getNode(BB);

	// If we are unreachable, we may not have an immediate dominator.
	if (!node)
	return 0;
	else if (!node->getIDom())
	return BBNode = new ETNode(BB);
	else {
	ETNode *IDomNode = getNodeForBlock(node->getIDom()->getBlock());

	// Add a new tree node for this BasicBlock, and link it as a child of
	// IDomNode
	BBNode = new ETNode(BB);
	BBNode->setFather(IDomNode);
	return BBNode;
	}
	}

	void PostETForest::calculate(const PostDominatorTree &DT) {
	for (unsigned i = 0, e = Roots.size(); i != e; ++i)
	Nodes[Roots[i]] = new ETNode(Roots[i]); // Add a node for the root

	// Iterate over all nodes in inverse depth first order.
	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;
	ETNode *&BBNode = Nodes[BB];
	if (!BBNode) {
	ETNode *IDomNode = NULL;
	PostDominatorTree::Node *node = DT.getNode(BB);
	if (node && node->getIDom())
	IDomNode = getNodeForBlock(node->getIDom()->getBlock());

	// Add a new ETNode for this BasicBlock, and set it's parent
	// to it's immediate dominator.
	BBNode = new ETNode(BB);
	if (IDomNode)
	BBNode->setFather(IDomNode);
	}
	}

	int dfsnum = 0;
	// Iterate over all nodes in depth first order...
	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) {
	if (!getNodeForBlock(*I)->hasFather())
	getNodeForBlock(*I)->assignDFSNumber(dfsnum);
	}
	DFSInfoValid = true;
	}

	//===----------------------------------------------------------------------===//
	// PostDominanceFrontier Implementation
	//===----------------------------------------------------------------------===//

	static RegisterPass<PostDominanceFrontier>
	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->getBlock();
	DomSetType &S = Frontiers[BB]; // The new set to fill in...
	if (getRoots().empty()) return S;

	if (BB)
	for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
	SI != SE; ++SI) {
	// Does Node immediately dominate this predecessor?
	DominatorTree::Node SINode = DT[SI];
	if (SINode && SINode->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->properlyDominates(DT[*CDFI]))
	S.insert(*CDFI);
	}
	}

	return S;
	}

	// Ensure that this .cpp file gets linked when PostDominators.h is used.
	DEFINING_FILE_FOR(PostDominanceFrontier)