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/*
* Fernflower - The Analytical Java Decompiler
* http://www.reversed-java.com
*
* (C) 2008 - 2010, Stiver
*
* This software is NEITHER public domain NOR free software
* as per GNU License. See license.txt for more details.
*
* This software is distributed WITHOUT ANY WARRANTY; without
* even the implied warranty of MERCHANTABILITY or FITNESS FOR
* A PARTICULAR PURPOSE.
*/
package de.fernflower.modules.decompiler.decompose;
import java.util.List;
import java.util.Set;
import de.fernflower.util.VBStyleCollection;
public class GenericDominatorEngine {
private IGraph graph;
private VBStyleCollection<IGraphNode, IGraphNode> colOrderedIDoms = new VBStyleCollection<IGraphNode, IGraphNode>();
private Set<? extends IGraphNode> setRoots;
public GenericDominatorEngine(IGraph graph) {
this.graph = graph;
}
public void initialize() {
calcIDoms();
}
private void orderNodes() {
setRoots = graph.getRoots();
for(IGraphNode node : graph.getReversePostOrderList()) {
colOrderedIDoms.addWithKey(null, node);
}
}
private IGraphNode getCommonIDom(IGraphNode node1, IGraphNode node2, VBStyleCollection<IGraphNode, IGraphNode> orderedIDoms) {
IGraphNode nodeOld;
if(node1 == null) {
return node2;
} else if(node2 == null) {
return node1;
}
int index1 = orderedIDoms.getIndexByKey(node1);
int index2 = orderedIDoms.getIndexByKey(node2);
while(index1 != index2) {
if(index1 > index2) {
nodeOld = node1;
node1 = orderedIDoms.getWithKey(node1);
if(nodeOld == node1) { // no idom - root or merging point
return null;
}
index1 = orderedIDoms.getIndexByKey(node1);
} else {
nodeOld = node2;
node2 = orderedIDoms.getWithKey(node2);
if(nodeOld == node2) { // no idom - root or merging point
return null;
}
index2 = orderedIDoms.getIndexByKey(node2);
}
}
return node1;
}
private void calcIDoms() {
orderNodes();
List<IGraphNode> lstNodes = colOrderedIDoms.getLstKeys();
for(;;) {
boolean changed = false;
for(IGraphNode node : lstNodes) {
IGraphNode idom = null;
if(!setRoots.contains(node)) {
for(IGraphNode pred : node.getPredecessors()) {
if(colOrderedIDoms.getWithKey(pred) != null) {
idom = getCommonIDom(idom, pred, colOrderedIDoms);
if(idom == null) {
break; // no idom found: merging point of two trees
}
}
}
}
if(idom == null) {
idom = node;
}
IGraphNode oldidom = colOrderedIDoms.putWithKey(idom, node);
if(!idom.equals(oldidom)) { // oldidom is null iff the node is touched for the first time
changed = true;
}
}
if(!changed) {
break;
}
}
}
public VBStyleCollection<IGraphNode, IGraphNode> getOrderedIDoms() {
return colOrderedIDoms;
}
public boolean isDominator(IGraphNode node, IGraphNode dom) {
while(!node.equals(dom)) {
IGraphNode idom = colOrderedIDoms.getWithKey(node);
if(idom == node) {
return false; // root node or merging point
} else if(idom == null) {
throw new RuntimeException("Inconsistent idom sequence discovered!");
} else {
node = idom;
}
}
return true;
}
}
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