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/*
* LoopsAndConditions.java
*
* Copyright (c) 2013 Mike Strobel
*
* This source code is based on Mono.Cecil from Jb Evain, Copyright (c) Jb Evain;
* and ILSpy/ICSharpCode from SharpDevelop, Copyright (c) AlphaSierraPapa.
*
* This source code is subject to terms and conditions of the Apache License, Version 2.0.
* A copy of the license can be found in the License.html file at the root of this distribution.
* By using this source code in any fashion, you are agreeing to be bound by the terms of the
* Apache License, Version 2.0.
*
* You must not remove this notice, or any other, from this software.
*/
package com.strobel.decompiler.ast;
import com.strobel.annotations.NotNull;
import com.strobel.assembler.flowanalysis.ControlFlowEdge;
import com.strobel.assembler.flowanalysis.ControlFlowGraph;
import com.strobel.assembler.flowanalysis.ControlFlowNode;
import com.strobel.assembler.flowanalysis.ControlFlowNodeType;
import com.strobel.assembler.flowanalysis.JumpType;
import com.strobel.assembler.metadata.SwitchInfo;
import com.strobel.core.ArrayUtilities;
import com.strobel.core.Pair;
import com.strobel.core.Predicate;
import com.strobel.core.StrongBox;
import com.strobel.decompiler.DecompilerContext;
import java.util.*;
import static com.strobel.core.CollectionUtilities.*;
import static com.strobel.decompiler.ast.AstOptimizer.*;
import static com.strobel.decompiler.ast.PatternMatching.*;
final class LoopsAndConditions {
private final Map labelsToNodes = new IdentityHashMap<>();
@SuppressWarnings({ "FieldCanBeLocal", "UnusedDeclaration" })
private final DecompilerContext context;
private int _nextLabelIndex;
LoopsAndConditions(final DecompilerContext context) {
this.context = context;
}
public final void findConditions(final Block block) {
final List body = block.getBody();
if (body.isEmpty() || block.getEntryGoto() == null) {
return;
}
final ControlFlowGraph graph = buildGraph(body, (Label) block.getEntryGoto().getOperand());
graph.computeDominance();
graph.computeDominanceFrontier();
final Set cfNodes = new LinkedHashSet<>();
final List graphNodes = graph.getNodes();
for (int i = 3; i < graphNodes.size(); i++) {
cfNodes.add(graphNodes.get(i));
}
final List newBody = findConditions(cfNodes, graph.getEntryPoint());
block.getBody().clear();
block.getBody().addAll(newBody);
}
public final void findLoops(final Block block) {
final List body = block.getBody();
if (body.isEmpty() || block.getEntryGoto() == null) {
return;
}
final ControlFlowGraph graph = buildGraph(body, (Label) block.getEntryGoto().getOperand());
graph.computeDominance();
graph.computeDominanceFrontier();
final Set cfNodes = new LinkedHashSet<>();
final List graphNodes = graph.getNodes();
for (int i = 3; i < graphNodes.size(); i++) {
cfNodes.add(graphNodes.get(i));
}
final List newBody = findLoops(cfNodes, graph.getEntryPoint(), false);
block.getBody().clear();
block.getBody().addAll(newBody);
}
private ControlFlowGraph buildGraph(final List nodes, final Label entryLabel) {
int index = 0;
final List cfNodes = new ArrayList<>();
final ControlFlowNode entryPoint = new ControlFlowNode(index++, 0, ControlFlowNodeType.EntryPoint);
final ControlFlowNode regularExit = new ControlFlowNode(index++, -1, ControlFlowNodeType.RegularExit);
final ControlFlowNode exceptionalExit = new ControlFlowNode(index++, -1, ControlFlowNodeType.ExceptionalExit);
cfNodes.add(entryPoint);
cfNodes.add(regularExit);
cfNodes.add(exceptionalExit);
//
// Create graph nodes.
//
labelsToNodes.clear();
final Map astNodesToControlFlowNodes = new IdentityHashMap<>();
for (final Node node : nodes) {
final ControlFlowNode cfNode = new ControlFlowNode(index++, -1, ControlFlowNodeType.Normal);
cfNodes.add(cfNode);
astNodesToControlFlowNodes.put(node, cfNode);
cfNode.setUserData(node);
//
// Find all contained labels.
//
for (final Label label : node.getSelfAndChildrenRecursive(Label.class)) {
labelsToNodes.put(label, cfNode);
}
}
final ControlFlowNode entryNode = labelsToNodes.get(entryLabel);
final ControlFlowEdge entryEdge = new ControlFlowEdge(entryPoint, entryNode, JumpType.Normal);
entryPoint.getOutgoing().add(entryEdge);
entryNode.getIncoming().add(entryEdge);
//
// Create edges.
//
for (final Node node : nodes) {
final ControlFlowNode source = astNodesToControlFlowNodes.get(node);
//
// Find all branches.
//
for (final Expression e : node.getSelfAndChildrenRecursive(Expression.class)) {
if (!e.isBranch()) {
continue;
}
for (final Label target : e.getBranchTargets()) {
final ControlFlowNode destination = labelsToNodes.get(target);
if (destination != null &&
(destination != source || canBeSelfContainedLoop((BasicBlock) node, e, target))) {
final ControlFlowEdge edge = new ControlFlowEdge(source, destination, JumpType.Normal);
if (!source.getOutgoing().contains(edge)) {
source.getOutgoing().add(edge);
}
if (!destination.getIncoming().contains(edge)) {
destination.getIncoming().add(edge);
}
}
}
}
}
return new ControlFlowGraph(cfNodes.toArray(new ControlFlowNode[cfNodes.size()]));
}
private boolean canBeSelfContainedLoop(final BasicBlock node, final Expression branch, final Label target) {
final List nodeBody = node.getBody();
if (target == null || nodeBody.isEmpty()) {
return false;
}
if (target == nodeBody.get(0)) {
return true;
}
final Node secondNode = getOrDefault(nodeBody, 1);
if (secondNode instanceof TryCatchBlock) {
final Node next = getOrDefault(nodeBody, 2);
if (next != branch) {
return false;
}
final TryCatchBlock tryCatch = (TryCatchBlock) secondNode;
final Block tryBlock = tryCatch.getTryBlock();
final Predicate labelMatch = new Predicate() {
@Override
public boolean test(final Expression e) {
return e != tryBlock.getEntryGoto() && e.getBranchTargets().contains(target);
}
};
/*
if (tryBlock != null) {
final Node firstInTryBody = firstOrDefault(tryBlock.getBody());
if (!(firstInTryBody instanceof BasicBlock &&
target == firstOrDefault(((BasicBlock) firstInTryBody).getBody()))) {
return false;
}
final boolean branchInTry = any(tryBlock.getSelfAndChildrenRecursive(Expression.class), labelMatch);
if (branchInTry) {
return false;
}
}
*/
for (final CatchBlock catchBlock : tryCatch.getCatchBlocks()) {
if (any(catchBlock.getSelfAndChildrenRecursive(Expression.class), labelMatch)) {
return true;
}
}
if (tryCatch.getFinallyBlock() != null &&
any(tryCatch.getFinallyBlock().getSelfAndChildrenRecursive(Expression.class), labelMatch)) {
return true;
}
return true;
}
return false;
}
@SuppressWarnings("ConstantConditions")
private List findLoops(final Set scopeNodes, final ControlFlowNode entryPoint, final boolean excludeEntryPoint) {
final List result = new ArrayList<>();
final StrongBox switchLabels = new StrongBox<>();
final Set scope = new LinkedHashSet<>(scopeNodes);
final ArrayDeque agenda = new ArrayDeque<>();
agenda.addLast(entryPoint);
while (!agenda.isEmpty()) {
final ControlFlowNode node = agenda.pollFirst();
//
// If the node is a loop header...
//
if (scope.contains(node) &&
node.getDominanceFrontier().contains(node) &&
(node != entryPoint || !excludeEntryPoint)) {
final Set loopContents = findLoopContents(scope, node);
//
// If the first or last expression is a loop condition...
//
final BasicBlock basicBlock = (BasicBlock) node.getUserData();
final StrongBox condition = new StrongBox<>();
final StrongBox
