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DexReturnPacker.java
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package soot.dexpler;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 1997 - 2018 Raja Vallée-Rai and others
* %%
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 2.1 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Lesser Public License for more details.
*
* You should have received a copy of the GNU General Lesser Public
* License along with this program. If not, see
* <http://www.gnu.org/licenses/lgpl-2.1.html>.
* #L%
*/
import java.util.Iterator;
import java.util.Map;
import soot.Body;
import soot.BodyTransformer;
import soot.Unit;
import soot.jimple.ReturnStmt;
import soot.jimple.ReturnVoidStmt;
/**
* This transformer is the inverse of the DexReturnInliner. It looks for unnecessary duplicates of return statements and
* removes them.
*
* @author Steven Arzt
*
*/
public class DexReturnPacker extends BodyTransformer {
public static DexReturnPacker v() {
return new DexReturnPacker();
}
@Override
protected void internalTransform(Body b, String phaseName, Map<String, String> options) {
// Look for consecutive return statements
Unit lastUnit = null;
for (Iterator<Unit> unitIt = b.getUnits().iterator(); unitIt.hasNext();) {
Unit curUnit = unitIt.next();
if (curUnit instanceof ReturnStmt || curUnit instanceof ReturnVoidStmt) {
// Check for duplicates
if (lastUnit != null && isEqual(lastUnit, curUnit)) {
curUnit.redirectJumpsToThisTo(lastUnit);
unitIt.remove();
} else {
lastUnit = curUnit;
}
} else {
// Start over
lastUnit = null;
}
}
}
/**
* Checks whether the two given units are semantically equal
*
* @param unit1
* The first unit
* @param unit2
* The second unit
* @return True if the two given units are semantically equal, otherwise false
*/
private boolean isEqual(Unit unit1, Unit unit2) {
// Trivial case
if (unit1 == unit2 || unit1.equals(unit2)) {
return true;
}
// Semantic check
if (unit1.getClass() == unit2.getClass()) {
if (unit1 instanceof ReturnVoidStmt) {
return true;
} else if (unit1 instanceof ReturnStmt) {
return ((ReturnStmt) unit1).getOp() == ((ReturnStmt) unit2).getOp();
}
}
return false;
}
}