sootup.java.bytecode.interceptors.LocalLivenessAnalyser Maven / Gradle / Ivy
package sootup.java.bytecode.interceptors;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 1997 - 2021 Raja Vallee-Rai, Zun Wang
* %%
* 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 sootup.core.graph.StmtGraph;
import sootup.core.jimple.basic.Local;
import sootup.core.jimple.basic.Value;
import sootup.core.jimple.common.stmt.Stmt;
/** @author Zun Wang */
public class LocalLivenessAnalyser {
// Each stmt(node) has out-edges and in-edges
// A local is live-in at a node if it is live on any its in-edges
private final Map> liveIn = new HashMap<>();
// A local is live-out at a node if it is live on any of its out-edges.
// e.g: a = b + c; live-in={b,c} live-out={a,b,c}
private final Map> liveOut = new HashMap<>();
public LocalLivenessAnalyser(@Nonnull StmtGraph graph) {
// initial liveIn and liveOut
List startingStmts = new ArrayList<>();
for (Stmt stmt : graph.getNodes()) {
liveIn.put(stmt, Collections.emptySet());
liveOut.put(stmt, Collections.emptySet());
if (graph.successors(stmt).isEmpty() && graph.exceptionalSuccessors(stmt).isEmpty()) {
startingStmts.add(stmt);
}
}
boolean fixed = false;
while (!fixed) {
fixed = true;
Deque queue = new ArrayDeque<>(startingStmts);
HashSet visitedStmts = new HashSet<>();
while (!queue.isEmpty()) {
Stmt stmt = queue.removeFirst();
visitedStmts.add(stmt);
Set out = new HashSet<>(liveOut.get(stmt));
for (Stmt succ : graph.successors(stmt)) {
out = merge(out, liveIn.get(succ));
}
for (Stmt esucc : graph.exceptionalSuccessors(stmt).values()) {
out = merge(out, liveIn.get(esucc));
}
if (isNotEqual(out, liveOut.get(stmt))) {
fixed = false;
liveOut.put(stmt, new HashSet<>(out));
}
Set in = new HashSet<>();
for (Value use : stmt.getUses()) {
if (use instanceof Local) {
in.add((Local) use);
}
}
final List defs = stmt.getDefs();
if (!defs.isEmpty()) {
final Value value = defs.get(0);
if (value instanceof Local) {
out.remove(value);
}
}
in = merge(in, out);
if (isNotEqual(in, liveIn.get(stmt))) {
fixed = false;
liveIn.put(stmt, in);
}
for (Stmt pred : graph.predecessors(stmt)) {
if (!visitedStmts.contains(pred)) {
queue.addLast(pred);
}
}
for (Stmt epred : graph.exceptionalPredecessors(stmt)) {
if (!visitedStmts.contains(epred)) {
queue.addLast(epred);
}
}
}
}
}
/** Get all live locals before the given stmt. */
@Nonnull
public Set getLiveLocalsBeforeStmt(@Nonnull Stmt stmt) {
if (!liveIn.containsKey(stmt)) {
throw new RuntimeException("Stmt: " + stmt + " is not in StmtGraph!");
}
return liveIn.get(stmt);
}
/** Get all live locals after the given stmt. */
@Nonnull
public Set getLiveLocalsAfterStmt(@Nonnull Stmt stmt) {
if (!liveOut.containsKey(stmt)) {
throw new RuntimeException("Stmt: " + stmt + " is not in StmtGraph!");
}
return liveOut.get(stmt);
}
/**
* Merge two local sets into one set.
*
* @return a merged local set
*/
@Nonnull
private Set merge(@Nonnull Set set1, @Nonnull Set set2) {
if (set1.isEmpty()) {
return set2;
} else {
set1.addAll(set2);
return set1;
}
}
/**
* Check whether two sets contains same locals.
*
* @return if same return true, else return false;
*/
private boolean isNotEqual(@Nonnull Set set1, @Nonnull Set set2) {
if (set1.size() != set2.size()) {
return true;
} else {
for (Local local : set1) {
if (!set2.contains(local)) {
return true;
}
}
}
return false;
}
}