X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FPostDominators.cpp;h=4f9d1d160696f336866748311c1cdbf7642ad835;hb=1c51c6ac13b5e68b099605021784c7f552dcce3c;hp=8b66ff6cad12f38cb872aadc465e432c97e9c61e;hpb=a69fd903585a665c031d5aa3fdfb8dc919b44bef;p=oota-llvm.git diff --git a/lib/Analysis/PostDominators.cpp b/lib/Analysis/PostDominators.cpp index 8b66ff6cad1..4f9d1d16069 100644 --- a/lib/Analysis/PostDominators.cpp +++ b/lib/Analysis/PostDominators.cpp @@ -1,15 +1,22 @@ //===- 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/Transforms/Utils/UnifyFunctionExitNodes.h" +#include "llvm/Instructions.h" #include "llvm/Support/CFG.h" -#include "Support/DepthFirstIterator.h" -#include "Support/SetOperations.h" -using std::set; +#include "llvm/ADT/DepthFirstIterator.h" +#include "llvm/ADT/SetOperations.h" +using namespace llvm; //===----------------------------------------------------------------------===// // PostDominatorSet Implementation @@ -24,63 +31,76 @@ B("postdomset", "Post-Dominator Set Construction", true); // 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().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 Visited; + std::set Visited; DomSetType WorkingSet; - idf_iterator 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 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.addRequired(); -} - //===----------------------------------------------------------------------===// // ImmediatePostDominators Implementation //===----------------------------------------------------------------------===// @@ -88,6 +108,43 @@ void PostDominatorSet::getAnalysisUsage(AnalysisUsage &AU) const { static RegisterAnalysis D("postidom", "Immediate Post-Dominators Construction", true); + +// calcIDoms - Calculate the immediate dominator mapping, given a set of +// dominators for every basic block. +void ImmediatePostDominators::calcIDoms(const DominatorSetBase &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) { + 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; + } + } + } +} + //===----------------------------------------------------------------------===// // PostDominatorTree Implementation //===----------------------------------------------------------------------===// @@ -96,17 +153,25 @@ static RegisterAnalysis 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 (Roots.empty()) return; + BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0; - if (Root) { - // Iterate over all nodes in depth first order... - for (idf_iterator I = idf_begin(Root), E = idf_end(Root); - I != E; ++I) { + Nodes[Root] = RootNode = new Node(Root, 0); // Add a node for the root... + + // Iterate over all nodes in depth first order... + for (unsigned i = 0, e = Roots.size(); i != e; ++i) + for (idf_iterator 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 @@ -116,31 +181,29 @@ void PostDominatorTree::calculate(const PostDominatorSet &DS) { // 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; + } } } - } } //===----------------------------------------------------------------------===// @@ -154,16 +217,16 @@ 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 @@ -187,3 +250,4 @@ PostDominanceFrontier::calculate(const PostDominatorTree &DT, // stub - a dummy function to make linking work ok. void PostDominanceFrontier::stub() { } +