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package soot.dexpler;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 2012 Michael Markert, Frank Hartmann
*
* (c) 2012 University of Luxembourg - Interdisciplinary Centre for
* Security Reliability and Trust (SnT) - All rights reserved
* Alexandre Bartel
*
* %%
* 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.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import soot.Body;
import soot.Trap;
import soot.Unit;
import soot.UnitBox;
import soot.jimple.GotoStmt;
import soot.jimple.IfStmt;
import soot.jimple.ReturnStmt;
import soot.jimple.ReturnVoidStmt;
import soot.jimple.Stmt;
/**
* BodyTransformer to inline jumps to return statements. Take the following code: a = b goto label1
*
* label1: return a We inline this to produce a = b return b
*
* @author Steven Arzt
*/
public class DexReturnInliner extends DexTransformer {
public static DexReturnInliner v() {
return new DexReturnInliner();
}
private boolean isInstanceofReturn(Unit u) {
if (u instanceof ReturnStmt || u instanceof ReturnVoidStmt) {
return true;
}
return false;
}
private boolean isInstanceofFlowChange(Unit u) {
if (u instanceof GotoStmt || isInstanceofReturn(u)) {
return true;
}
return false;
}
@Override
protected void internalTransform(final Body body, String phaseName, Map<String, String> options) {
Set<Unit> duplicateIfTargets = getFallThroughReturns(body);
Iterator<Unit> it = body.getUnits().snapshotIterator();
boolean mayBeMore = false;
Unit last = null;
do {
mayBeMore = false;
while (it.hasNext()) {
Unit u = it.next();
if (u instanceof GotoStmt) {
GotoStmt gtStmt = (GotoStmt) u;
if (isInstanceofReturn(gtStmt.getTarget())) {
Stmt stmt = (Stmt) gtStmt.getTarget().clone();
for (Trap t : body.getTraps()) {
for (UnitBox ubox : t.getUnitBoxes()) {
if (ubox.getUnit() == u) {
ubox.setUnit(stmt);
}
}
}
while (!u.getBoxesPointingToThis().isEmpty()) {
u.getBoxesPointingToThis().get(0).setUnit(stmt);
}
// the cloned return stmt gets the tags of u
stmt.addAllTagsOf(u);
body.getUnits().swapWith(u, stmt);
mayBeMore = true;
}
} else if (u instanceof IfStmt) {
IfStmt ifstmt = (IfStmt) u;
Unit t = ifstmt.getTarget();
if (isInstanceofReturn(t)) {
// We only copy this return if it is used more than
// once, otherwise we will end up with unused copies
if (duplicateIfTargets == null) {
duplicateIfTargets = new HashSet<Unit>();
}
if (!duplicateIfTargets.add(t)) {
Unit newTarget = (Unit) t.clone();
body.getUnits().addLast(newTarget);
ifstmt.setTarget(newTarget);
}
}
} else if (isInstanceofReturn(u)) {
// the original return stmt gets the tags of its predecessor
if (last != null) {
u.removeAllTags();
u.addAllTagsOf(last);
}
}
last = u;
}
} while (mayBeMore);
}
/**
* Gets the set of return statements that can be reached via fall-throughs, i.e. normal sequential code execution. Dually,
* these are the statements that can be reached without jumping there.
*
* @param body
* The method body
* @return The set of fall-through return statements
*/
private Set<Unit> getFallThroughReturns(Body body) {
Set<Unit> fallThroughReturns = null;
Unit lastUnit = null;
for (Unit u : body.getUnits()) {
if (lastUnit != null && isInstanceofReturn(u) && !isInstanceofFlowChange(lastUnit)) {
if (fallThroughReturns == null) {
fallThroughReturns = new HashSet<Unit>();
}
fallThroughReturns.add(u);
}
lastUnit = u;
}
return fallThroughReturns;
}
}