sootup.java.bytecode.interceptors.LocalSplitter Maven / Gradle / Ivy
package sootup.java.bytecode.interceptors;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 1997-2020 Raja Vallée-Rai, Christian Brüggemann
* %%
* 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
* .
* #L%
*/
import java.util.*;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import sootup.core.graph.StmtGraph;
import sootup.core.jimple.basic.LValue;
import sootup.core.jimple.basic.Local;
import sootup.core.jimple.basic.Value;
import sootup.core.jimple.common.ref.JCaughtExceptionRef;
import sootup.core.jimple.common.stmt.AbstractDefinitionStmt;
import sootup.core.jimple.common.stmt.JIdentityStmt;
import sootup.core.jimple.common.stmt.Stmt;
import sootup.core.model.Body;
import sootup.core.model.Body.BodyBuilder;
import sootup.core.transform.BodyInterceptor;
import sootup.core.types.ClassType;
import sootup.core.views.View;
/**
* A BodyInterceptor that attempts to identify and separate uses of a local variable (definition)
* that are independent of each other.
*
* For example the code:
*
*
* l0 := @this Test
* l1 = 0
* l2 = 1
* l1 = l1 + 1
* l2 = l2 + 1
* return
*
*
* to:
*
*
* l0 := @this Test
* l1#1 = 0
* l2#2 = 1
* l1#3 = l1#1 + 1
* l2#4 = l2#2 + 1
* return
*
*
* @author Zun Wang
*/
public class LocalSplitter implements BodyInterceptor {
// FIXME: [ms] assumes that names of Locals do not contain a '#' already -> could lead to problems
// TODO: [ms] check equivTo()'s - I guess they can be equals()'s - or even: '=='s
@Override
public void interceptBody(@Nonnull Body.BodyBuilder builder, @Nonnull View view) {
// Find all Locals that must be split
// If a local as a definition appears two or more times, then this local must be split
List stmts = builder.getStmts();
Set visitedLocals = new LinkedHashSet<>();
Set toSplitLocals = new LinkedHashSet<>();
for (Stmt stmt : stmts) {
final List defs = stmt.getDefs();
if (!defs.isEmpty()) {
Value def = defs.get(0);
if (def instanceof Local) {
if (visitedLocals.contains(def)) {
toSplitLocals.add((Local) def);
}
visitedLocals.add((Local) def);
}
}
}
StmtGraph graph = builder.getStmtGraph();
// Create a new Local-Set for the modified new body.
Set newLocals = new LinkedHashSet<>(builder.getLocals());
int localIndex = 1;
// iterate stmts
while (!stmts.isEmpty()) {
Stmt currentStmt = stmts.remove(0);
// At first Check the definition(left side) of the currentStmt is a local which must be split:
final List defs = currentStmt.getDefs();
if (!defs.isEmpty() && defs.get(0) instanceof Local && toSplitLocals.contains(defs.get(0))) {
// then assign a new name to the oriLocal to get a new local which is called newLocal
Local oriLocal = (Local) defs.get(0);
Local newLocal = oriLocal.withName(oriLocal.getName() + "#" + localIndex);
newLocals.add(newLocal);
localIndex++;
// create newStmt whose definition is replaced with the newLocal,
Stmt newStmt = ((AbstractDefinitionStmt) currentStmt).withNewDef(newLocal);
// replace corresponding oldStmt with newStmt in builder
replaceStmtInBuilder(builder, stmts, currentStmt, newStmt);
// Build the forwardsQueue which is used to iterate all Stmts before the orilocal is defined
// again.
// The direction of iteration is from root of the StmtGraph to leafs. So the successors of
// the newStmt are added into the forwardsQueue.
Deque forwardsQueue = new ArrayDeque<>(graph.successors(newStmt));
// Create the visitedStmt to store the visited Stmts for the forwardsQueue, to avoid, a
// Stmt is added twice into the forwardQueue.
Set visitedStmts = new HashSet<>();
while (!forwardsQueue.isEmpty()) {
Stmt head = forwardsQueue.remove();
visitedStmts.add(head);
// 1.case: if useList of head contains oriLocal, then replace the oriLocal with
// newLocal.
if (head.getUses().contains(oriLocal)) {
Stmt newHead = head.withNewUse(oriLocal, newLocal);
replaceStmtInBuilder(builder, stmts, head, newHead);
// if head doesn't define the the oriLocal again, then add all successors which are
// not in forwardsQueue and visitedUsesStmt, into the forwardsQueue.
if (newHead.getDefs().isEmpty() || !newHead.getDefs().get(0).equivTo(oriLocal)) {
for (Stmt succ : graph.successors(newHead)) {
if (!visitedStmts.contains(succ) && !forwardsQueue.contains(succ)) {
forwardsQueue.addLast(succ);
}
}
}
}
// 2.case: if uses of head contains the modified orilocal, so a conflict maybe arise,
// then trace the StmtGraph backwards to resolve the conflict.
else if (hasModifiedUse(head, oriLocal)) {
Local modifiedLocal = getModifiedUse(head, oriLocal);
if (modifiedLocal == null) {
throw new IllegalStateException("Modified Use is not found.");
}
// if modifed name is not same as the newLocal's name then -> conflict arises -> trace
// backwards
if (!modifiedLocal.getName().equals(newLocal.getName())) {
localIndex--;
// Build the backwardsQueue which is used to iterate all Stmts between head and the
// Stmts which define the oriLocal in last time.
// The direction of iteration is from leave of the StmtGraph to the root. So the
// predecessors of head are added into the BackwardsQueue.
Deque backwardsQueue = new ArrayDeque<>(graph.predecessors(head));
while (!backwardsQueue.isEmpty()) {
// Remove the first Stmt of backwardQueue, and name it as backStmt.
Stmt backStmt = backwardsQueue.remove();
// 2.1 case: if backStmt's definition is the modified and has a higher
// local-name-index than the modifiedLocal of head
// then replace the definition of backStmt with the modifiedLocal of head, and
// remove the corresponding Local(definition of backStmt) from the set: newLocals
if (hasModifiedDef(backStmt, oriLocal)) {
if (hasHigherLocalName((Local) backStmt.getDefs().get(0), modifiedLocal)) {
Stmt newBackStmt =
((AbstractDefinitionStmt) backStmt).withNewDef(modifiedLocal);
replaceStmtInBuilder(builder, stmts, backStmt, newBackStmt);
newLocals.remove(newLocal);
}
}
// 2.2 case: if backStmt's uses contains the modified oriLocal, and this
// modified oriLocal has a higher local-name-index that the modifiedLocal of head
// then replace the corresponding use of backStmt with modifiedLocal of head, and
// add all predecessors of the backStmt into the backwardsQueue.
else if (hasModifiedUse(backStmt, oriLocal)) {
Local modifiedUse = getModifiedUse(backStmt, oriLocal);
if (hasHigherLocalName(modifiedUse, modifiedLocal)) {
Stmt newBackStmt = backStmt.withNewUse(modifiedUse, modifiedLocal);
replaceStmtInBuilder(builder, stmts, backStmt, newBackStmt);
backwardsQueue.addAll(graph.predecessors(newBackStmt));
}
}
// 2.3 case: if there's no relationship between backStmt's defs/uses and
// oriLocal, then add all predecessors of the backStmt into the backwardsQueue.
else {
backwardsQueue.addAll(graph.predecessors(backStmt));
}
}
}
}
// 3.case: if uses of head contains neither orilocal nor the modified orilocal,
// then add all successors of head which are not in forwardsQueue and visitedStmts,
// into the forwardsQueue.
else {
final List headDefs = head.getDefs();
if (headDefs.isEmpty() || !headDefs.get(0).equivTo(oriLocal)) {
for (Stmt succ : graph.successors(head)) {
if (!visitedStmts.contains(succ) && !forwardsQueue.contains(succ)) {
forwardsQueue.addLast(succ);
}
}
}
}
}
// Then check the uses of currentStmt:
} else {
// For each Local(oriL) which is to be split, check whether it is used in currentStmt
// without definition before.
// We define a StmtGraph consists of a mainStmtGraph and none or more trapStmtGraphs.
// This situation could arise just in a trapStmtGraph.
for (Local oriLocal : toSplitLocals) {
// If so:
// 1.step: find out all trapStmtGraphs' root(handlerStmts) which contain currentStmt,
// namely a set of handlerStmts.
// 2.step: find out all stmts whose exceptional destination-traps are with the found
// handlerStmts.
// 3.step: iterate these stmts, find a modified oriL((Local) with a maximum name index.
// 4.step: Use this modified oriL to modify the visitedStmt
if (currentStmt.getUses().contains(oriLocal)) {
// 1.step:
Set handlerStmts = traceHandlerStmts(graph, currentStmt);
// 2.step:
Set stmtsWithDests = new HashSet<>();
for (Stmt handlerStmt : handlerStmts) {
for (Stmt exceptionalPred : graph.predecessors(handlerStmt)) {
Map dests = graph.exceptionalSuccessors(exceptionalPred);
List destHandlerStmts = new ArrayList<>();
dests.forEach((key, dest) -> destHandlerStmts.add(dest));
if (destHandlerStmts.contains(handlerStmt)) {
stmtsWithDests.add(exceptionalPred);
}
}
}
// 3.step:
Local lastChange = null;
for (Stmt stmt : stmtsWithDests) {
if (hasModifiedDef(stmt, oriLocal)) {
Local modifiedLocal = (Local) stmt.getDefs().get(0);
if (lastChange == null || hasHigherLocalName(modifiedLocal, lastChange)) {
lastChange = modifiedLocal;
}
}
}
// 4.step:
if (lastChange != null) {
Stmt newStmt = currentStmt.withNewUse(oriLocal, lastChange);
replaceStmtInBuilder(builder, stmts, currentStmt, newStmt);
}
}
}
}
}
builder.setLocals(newLocals);
}
// ******************assist_functions*************************
/**
* Replace corresponding oldStmt with newStmt in BodyBuilder and visitList
*
* @param builder
* @param stmtIterationList
* @param oldStmt
* @param newStmt
*/
private void replaceStmtInBuilder(
@Nonnull BodyBuilder builder,
@Nonnull List stmtIterationList,
@Nonnull Stmt oldStmt,
@Nonnull Stmt newStmt) {
builder.replaceStmt(oldStmt, newStmt);
// adapt VisitList
final int index = stmtIterationList.indexOf(oldStmt);
if (index > -1) {
stmtIterationList.set(index, newStmt);
}
}
/**
* Check whether a Stmt's useList contains the given modified oriLocal.
*
* @param stmt: a stmt is to be checked
* @param oriLocal: a local is to be checked
* @return if so, return true, else return false
*/
private boolean hasModifiedUse(@Nonnull Stmt stmt, @Nonnull Local oriLocal) {
for (Value use : stmt.getUses()) {
return isLocalFromSameOrigin(oriLocal, use);
}
return false;
}
/**
* Get the modified Local if a Stmt's useList contains the given modified oriLocal
*
* @param stmt: a stmt is to be checked
* @param oriLocal: a local is to be checked.
* @return if so, return this modified local, else return null
*/
@Nullable
private Local getModifiedUse(@Nonnull Stmt stmt, @Nonnull Local oriLocal) {
if (hasModifiedUse(stmt, oriLocal)) {
List useList = stmt.getUses();
for (Value use : useList) {
if (isLocalFromSameOrigin(oriLocal, use)) {
return (Local) use;
}
}
}
return null;
}
/**
* Check whether a local is modified from the given oriLocal
*
* @param local: a local is to be checked
* @param oriLocal: the given oriLocal
* @return if so, return true, else return false.
*/
private boolean isLocalFromSameOrigin(@Nonnull Local oriLocal, Value local) {
if (local instanceof Local) {
final String name = ((Local) local).getName();
final String origName = oriLocal.getName();
final int origLength = origName.length();
return name.length() > origLength
&& name.startsWith(origName)
&& name.charAt(origLength) == '#';
}
return false;
}
/**
* Check whether a Stmt's def is the modified oriLocal
*
* @param stmt: a stmt is to be checked
* @param oriLocal: a local is to be checked
* @return if so, return true, else return false
*/
private boolean hasModifiedDef(@Nonnull Stmt stmt, @Nonnull Local oriLocal) {
final List defs = stmt.getDefs();
if (!defs.isEmpty() && defs.get(0) instanceof Local) {
return isLocalFromSameOrigin(oriLocal, defs.get(0));
}
return false;
}
/**
* Check whether leftLocal's name has higher index than rightLocal's.
*
* @param leftLocal: a local in form oriLocal#num1
* @param rightLocal: a local in form oriLocal#num2
* @return if so return true, else return false
*/
private boolean hasHigherLocalName(@Nonnull Local leftLocal, @Nonnull Local rightLocal) {
String leftName = leftLocal.getName();
String rightName = rightLocal.getName();
int lIdx = leftName.lastIndexOf('#');
int rIdx = rightName.lastIndexOf('#');
int leftNum = Integer.parseInt(leftName.substring(lIdx + 1));
int rightNum = Integer.parseInt(rightName.substring(rIdx + 1));
return leftNum > rightNum;
}
/**
* A given entryStmt may be in one or several trapStmtGraphs, return these trapStmtGraphs'
* handlerStmts
*
* @param entryStmt a given entryStmt which is in one or several trapStmtGraphs
* @param graph to trace handlerStmts
* @return a set of handlerStmts
*/
@Nonnull
private Set traceHandlerStmts(@Nonnull StmtGraph graph, @Nonnull Stmt entryStmt) {
Set handlerStmts = new HashSet<>();
Deque queue = new ArrayDeque<>();
queue.add(entryStmt);
while (!queue.isEmpty()) {
Stmt stmt = queue.removeFirst();
if (stmt instanceof JIdentityStmt
&& ((JIdentityStmt) stmt).getRightOp() instanceof JCaughtExceptionRef) {
handlerStmts.add(stmt);
} else {
final List predecessors = graph.predecessors(stmt);
queue.addAll(predecessors);
}
}
return handlerStmts;
}
}