//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
//
+// The LLVM Compiler Infrastructure
+//
+// This file 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/Transforms/Utils/UnifyFunctionExitNodes.h"
-#include "llvm/Support/CFG.h"
-#include "Support/DepthFirstIterator.h"
-#include "Support/SetOperations.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SetOperations.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/GenericDomTreeConstruction.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "postdomtree"
//===----------------------------------------------------------------------===//
-// PostDominatorSet Implementation
+// PostDominatorTree Implementation
//===----------------------------------------------------------------------===//
-static RegisterAnalysis<PostDominatorSet>
-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
-// sets for the function.
-//
-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();
+char PostDominatorTree::ID = 0;
+INITIALIZE_PASS(PostDominatorTree, "postdomtree",
+ "Post-Dominator Tree Construction", true, true)
- 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;
-
- std::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];
-
- for (++PI; PI != PEnd; ++PI) { // Intersect all of the successor sets
- DomSetType &PredSet = Doms[*PI];
- 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
- 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);
+bool PostDominatorTree::runOnFunction(Function &F) {
+ DT->recalculate(F);
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>();
+PostDominatorTree::~PostDominatorTree() {
+ delete DT;
}
-//===----------------------------------------------------------------------===//
-// ImmediatePostDominators Implementation
-//===----------------------------------------------------------------------===//
-
-static RegisterAnalysis<ImmediatePostDominators>
-D("postidom", "Immediate Post-Dominators Construction", true);
-
-//===----------------------------------------------------------------------===//
-// PostDominatorTree Implementation
-//===----------------------------------------------------------------------===//
-
-static RegisterAnalysis<PostDominatorTree>
-F("postdomtree", "Post-Dominator Tree Construction", true);
-
-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) {
- 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::print(raw_ostream &OS, const Module *) const {
+ DT->print(OS);
}
-//===----------------------------------------------------------------------===//
-// PostDominanceFrontier Implementation
-//===----------------------------------------------------------------------===//
-
-static RegisterAnalysis<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->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);
- }
- }
-
- return S;
+FunctionPass* llvm::createPostDomTree() {
+ return new PostDominatorTree();
}
-// stub - a dummy function to make linking work ok.
-void PostDominanceFrontier::stub() {
-}
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