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/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.jack.optimizations;
import com.android.jack.Options;
import com.android.jack.analysis.DefinitionMarker;
import com.android.jack.analysis.UseDefsMarker;
import com.android.jack.cfg.BasicBlock;
import com.android.jack.cfg.ControlFlowGraph;
import com.android.jack.ir.ast.JArrayRef;
import com.android.jack.ir.ast.JAsgOperation;
import com.android.jack.ir.ast.JBinaryOperation;
import com.android.jack.ir.ast.JExceptionRuntimeValue;
import com.android.jack.ir.ast.JExpression;
import com.android.jack.ir.ast.JFieldRef;
import com.android.jack.ir.ast.JIfStatement;
import com.android.jack.ir.ast.JMethod;
import com.android.jack.ir.ast.JNode;
import com.android.jack.ir.ast.JStatement;
import com.android.jack.ir.ast.JSwitchStatement;
import com.android.jack.ir.ast.JVariableRef;
import com.android.jack.ir.ast.JVisitor;
import com.android.jack.transformations.ast.RefAsStatement;
import com.android.jack.transformations.request.Remove;
import com.android.jack.transformations.request.TransformationRequest;
import com.android.jack.transformations.threeaddresscode.ThreeAddressCodeForm;
import com.android.jack.util.filter.Filter;
import com.android.sched.item.Description;
import com.android.sched.schedulable.Constraint;
import com.android.sched.schedulable.RunnableSchedulable;
import com.android.sched.schedulable.Transform;
import com.android.sched.util.config.ThreadConfig;
import java.util.List;
import javax.annotation.Nonnull;
/**
* Remove unused definition.
*/
@Description("Remove useless variable copies.")
@Constraint(need = {DefinitionMarker.class, UseDefsMarker.class, ThreeAddressCodeForm.class,
ControlFlowGraph.class})
@Transform(add = {RefAsStatement.class})
public class UnusedDefinitionRemover implements RunnableSchedulable<JMethod> {
@Nonnull
private final Filter<JMethod> filter = ThreadConfig.get(Options.METHOD_FILTER);
private static class Visitor extends JVisitor {
@Nonnull
private final TransformationRequest tr;
public Visitor(@Nonnull TransformationRequest tr) {
this.tr = tr;
}
@Override
public boolean visit(@Nonnull JBinaryOperation binary) {
JExpression rhs = binary.getRhs();
if (binary instanceof JAsgOperation
&& !(rhs instanceof JExceptionRuntimeValue)
&& !rhs.canThrow()) {
DefinitionMarker dm = binary.getMarker(DefinitionMarker.class);
if (dm != null && dm.isUnused() && dm.getDefinedVariable().isSynthetic()) {
assert !(binary.getLhs() instanceof JFieldRef || binary.getLhs() instanceof JArrayRef);
removeUnusedDefinition((JAsgOperation) binary);
}
}
return super.visit(binary);
}
private void removeUnusedDefinition(@Nonnull JAsgOperation binary) {
assert !(binary.getRhs() instanceof JExceptionRuntimeValue);
tr.append(new Remove(binary.getParent()));
if (binary.getRhs() instanceof JVariableRef) {
UseDefsMarker udm = ((JVariableRef) binary.getRhs()).getMarker(UseDefsMarker.class);
assert udm != null;
List<DefinitionMarker> previouslyUsedDef = udm.getDefs();
udm.removeAllUsedDefinitions((JVariableRef) binary.getRhs());
// Check if previous used definition are again useful or not.
for (DefinitionMarker dmUsed : previouslyUsedDef) {
JNode definition = dmUsed.getDefinition();
if (dmUsed.isUnused() && dmUsed.hasValue()) {
JExpression expr = dmUsed.getValue();
if (!(expr instanceof JExceptionRuntimeValue) && !expr.canThrow()) {
removeUnusedDefinition((JAsgOperation) definition);
}
}
}
}
}
@Override
public boolean visit(@Nonnull JIfStatement ifStmt) {
super.visit(ifStmt);
this.accept(ifStmt.getIfExpr());
return false;
}
@Override
public boolean visit(@Nonnull JSwitchStatement switchStmt) {
super.visit(switchStmt);
this.accept(switchStmt.getExpr());
return false;
}
}
@Override
public void run(@Nonnull JMethod method) throws Exception {
if (method.getEnclosingType().isExternal() || method.isNative() || method.isAbstract()
|| !filter.accept(this.getClass(), method)) {
return;
}
ControlFlowGraph cfg = method.getMarker(ControlFlowGraph.class);
assert cfg != null;
TransformationRequest tr = new TransformationRequest(method);
for (BasicBlock bb : cfg.getNodes()) {
for (JStatement stmt : bb.getStatements()) {
Visitor visitor = new Visitor(tr);
visitor.accept(stmt);
}
}
tr.commit();
}
}
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