/*
* Copyright 2008 Google Inc.
*
* 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.google.gwt.dev.jjs.impl;
import com.google.gwt.dev.jjs.InternalCompilerException;
import com.google.gwt.dev.jjs.SourceInfo;
import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.JAbstractMethodBody;
import com.google.gwt.dev.jjs.ast.JClassType;
import com.google.gwt.dev.jjs.ast.JConstructor;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JMethod;
import com.google.gwt.dev.jjs.ast.JMethodBody;
import com.google.gwt.dev.jjs.ast.JMethodCall;
import com.google.gwt.dev.jjs.ast.JModVisitor;
import com.google.gwt.dev.jjs.ast.JParameter;
import com.google.gwt.dev.jjs.ast.JParameterRef;
import com.google.gwt.dev.jjs.ast.JProgram;
import com.google.gwt.dev.jjs.ast.JReturnStatement;
import com.google.gwt.dev.jjs.ast.JStatement;
import com.google.gwt.dev.jjs.ast.JThisRef;
import com.google.gwt.dev.jjs.ast.JType;
import com.google.gwt.dev.jjs.ast.JVisitor;
import com.google.gwt.dev.jjs.ast.js.JMultiExpression;
import com.google.gwt.dev.jjs.ast.js.JsniMethodBody;
import com.google.gwt.dev.js.ast.JsContext;
import com.google.gwt.dev.js.ast.JsFunction;
import com.google.gwt.dev.js.ast.JsModVisitor;
import com.google.gwt.dev.js.ast.JsName;
import com.google.gwt.dev.js.ast.JsParameter;
import com.google.gwt.dev.js.ast.JsThisRef;
import com.google.gwt.dev.util.log.speedtracer.CompilerEventType;
import com.google.gwt.dev.util.log.speedtracer.SpeedTracerLogger;
import com.google.gwt.dev.util.log.speedtracer.SpeedTracerLogger.Event;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
/**
* This is an interesting "optimization". It's not really an optimization in and
* of itself, but it opens the door to other optimizations. The basic idea is
* that you look for calls to instance methods that are not actually
* polymorphic. In other words, the target method is (effectively) final, not
* overridden anywhere in the compilation. We rewrite the single instance method
* as a static method that contains the implementation plus an instance method
* that delegates to the static method. Then we update any call sites to call
* the static method instead. This opens the door to further optimizations,
* reduces use of the long "this" keyword in the resulting JavaScript, and in
* most cases the polymorphic version can be pruned later.
*/
public class MakeCallsStatic {
/**
* For all methods that should be made static, move the contents of the method
* to a new static method, and have the original (instance) method delegate to
* it. Sometimes the instance method can be pruned later since we update all
* non-polymorphic call sites.
*/
static class CreateStaticImplsVisitor extends JVisitor {
/**
* When code is moved from an instance method to a static method, all
* thisRefs must be replaced with paramRefs to the synthetic this param.
*/
private class RewriteJsniMethodBody extends JsModVisitor {
private final JsName thisParam;
public RewriteJsniMethodBody(JsName thisParam) {
this.thisParam = thisParam;
}
@Override
public void endVisit(JsThisRef x, JsContext ctx) {
ctx.replaceMe(thisParam.makeRef(x.getSourceInfo()));
}
@Override
public boolean visit(JsFunction x, JsContext ctx) {
// Don't recurse into nested functions!
return false;
}
}
/**
* When code is moved from an instance method to a static method, all
* thisRefs must be replaced with paramRefs to the synthetic this param.
* ParameterRefs also need to be targeted to the params in the new method.
*/
private class RewriteMethodBody extends JModVisitor {
private final JParameter thisParam;
private final Map<JParameter, JParameter> varMap;
public RewriteMethodBody(JParameter thisParam, Map<JParameter, JParameter> varMap) {
this.thisParam = thisParam;
this.varMap = varMap;
}
@Override
public void endVisit(JParameterRef x, Context ctx) {
JParameter param = varMap.get(x.getTarget());
JParameterRef paramRef = new JParameterRef(x.getSourceInfo(), param);
ctx.replaceMe(paramRef);
}
@Override
public void endVisit(JThisRef x, Context ctx) {
JParameterRef paramRef = new JParameterRef(x.getSourceInfo(), thisParam);
ctx.replaceMe(paramRef);
}
}
private final JProgram program;
CreateStaticImplsVisitor(JProgram program) {
this.program = program;
}
@Override
public boolean visit(JConstructor x, Context ctx) {
throw new InternalCompilerException("Should not try to staticify constructors");
}
@Override
public boolean visit(JMethod x, Context ctx) {
// Let's do it!
JClassType enclosingType = (JClassType) x.getEnclosingType();
JType returnType = x.getType();
SourceInfo sourceInfo = x.getSourceInfo().makeChild();
int myIndexInClass = enclosingType.getMethods().indexOf(x);
assert (myIndexInClass > 0);
// Create the new static method
String newName = "$" + x.getName();
/*
* Don't use the JProgram helper because it auto-adds the new method to
* its enclosing class.
*/
JMethod newMethod =
new JMethod(sourceInfo, newName, enclosingType, returnType, false, true, true, x
.getAccess());
newMethod.setSynthetic();
newMethod.addThrownExceptions(x.getThrownExceptions());
// Setup parameters; map from the old params to the new params
JParameter thisParam =
JParameter.create(sourceInfo, "this$static", enclosingType.getNonNull(), true, true,
newMethod);
Map<JParameter, JParameter> varMap = new IdentityHashMap<JParameter, JParameter>();
for (int i = 0; i < x.getParams().size(); ++i) {
JParameter oldVar = x.getParams().get(i);
JParameter newVar =
JParameter.create(oldVar.getSourceInfo(), oldVar.getName(), oldVar.getType(), oldVar
.isFinal(), false, newMethod);
varMap.put(oldVar, newVar);
}
// Set the new original param types based on the old original param types
List<JType> originalParamTypes = new ArrayList<JType>();
originalParamTypes.add(enclosingType.getNonNull());
originalParamTypes.addAll(x.getOriginalParamTypes());
newMethod.setOriginalTypes(x.getOriginalReturnType(), originalParamTypes);
// Move the body of the instance method to the static method
JAbstractMethodBody movedBody = x.getBody();
newMethod.setBody(movedBody);
JMethodBody newBody = new JMethodBody(sourceInfo);
x.setBody(newBody);
JMethodCall newCall = new JMethodCall(sourceInfo, null, newMethod);
newCall.addArg(new JThisRef(sourceInfo, enclosingType));
for (int i = 0; i < x.getParams().size(); ++i) {
JParameter param = x.getParams().get(i);
newCall.addArg(new JParameterRef(sourceInfo, param));
}
JStatement statement;
if (returnType == program.getTypeVoid()) {
statement = newCall.makeStatement();
} else {
statement = new JReturnStatement(sourceInfo, newCall);
}
newBody.getBlock().addStmt(statement);
/*
* Rewrite the method body. Update all thisRefs to paramRefs. Update
* paramRefs and localRefs to target the params/locals in the new method.
*/
if (newMethod.isNative()) {
// For natives, we also need to create the JsParameter for this$static,
// because the jsFunc already has parameters.
// TODO: Do we really need to do that in BuildTypeMap?
JsFunction jsFunc = ((JsniMethodBody) movedBody).getFunc();
JsName paramName = jsFunc.getScope().declareName("this$static");
jsFunc.getParameters().add(0, new JsParameter(sourceInfo, paramName));
RewriteJsniMethodBody rewriter = new RewriteJsniMethodBody(paramName);
// Accept the body to avoid the recursion blocker.
rewriter.accept(jsFunc.getBody());
} else {
RewriteMethodBody rewriter = new RewriteMethodBody(thisParam, varMap);
rewriter.accept(movedBody);
}
// Add the new method as a static impl of the old method
program.putStaticImpl(x, newMethod);
enclosingType.getMethods().add(myIndexInClass + 1, newMethod);
return false;
}
}
/**
* Look for any places where instance methods are called in a static manner.
* Record this fact so we can create static dispatch implementations.
*/
private class FindStaticDispatchSitesVisitor extends JVisitor {
@Override
public void endVisit(JMethodCall x, Context ctx) {
JMethod method = x.getTarget();
if (method.isExternal()) {
// Staticifying a method requires modifying the type, which we can't
// do for external types. Theoretically we could put the static method
// in some generated code, but what does that really buy us?
return;
}
// Did we already do this one?
if (program.getStaticImpl(method) != null || toBeMadeStatic.contains(method)) {
return;
}
// Must be instance and final
if (x.canBePolymorphic()) {
return;
}
if (!method.needsVtable()) {
return;
}
if (method.isAbstract()) {
return;
}
if (method == program.getNullMethod()) {
// Special case: we don't make calls to this method static.
return;
}
if (!method.getEnclosingType().getMethods().contains(method)) {
// The target method was already pruned (TypeTightener will fix this).
return;
}
// Let's do it!
toBeMadeStatic.add(method);
}
}
/**
* For any method calls to methods we updated during
* CreateStaticMethodVisitor, go and rewrite the call sites to call the static
* method instead.
*/
private class RewriteCallSites extends JModVisitor {
private boolean currentMethodIsInitiallyLive;
private ControlFlowAnalyzer initiallyLive;
/**
* In cases where callers are directly referencing (effectively) final
* instance methods, rewrite the call site to reference the newly-generated
* static method instead.
*/
@Override
public void endVisit(JMethodCall x, Context ctx) {
JMethod oldMethod = x.getTarget();
JMethod newMethod = program.getStaticImpl(oldMethod);
if (newMethod == null || x.canBePolymorphic()) {
return;
}
if (currentMethodIsInitiallyLive
&& !initiallyLive.getLiveFieldsAndMethods().contains(x.getTarget())) {
/*
* Don't devirtualize calls from initial code to non-initial code.
*
* TODO(spoon): similar prevention when the callee is exclusive to some
* split point and the caller is not.
*/
return;
}
ctx.replaceMe(makeStaticCall(x, newMethod));
}
@Override
public boolean visit(JMethod x, Context ctx) {
currentMethodIsInitiallyLive = initiallyLive.getLiveFieldsAndMethods().contains(x);
return true;
}
@Override
public boolean visit(JProgram x, Context ctx) {
initiallyLive = CodeSplitter.computeInitiallyLive(x);
return true;
}
}
private static final String NAME = MakeCallsStatic.class.getSimpleName();
public static OptimizerStats exec(JProgram program) {
Event optimizeEvent = SpeedTracerLogger.start(CompilerEventType.OPTIMIZE, "optimizer", NAME);
OptimizerStats stats = new MakeCallsStatic(program).execImpl();
optimizeEvent.end("didChange", "" + stats.didChange());
return stats;
}
static JExpression makeStaticCall(JMethodCall x, JMethod newMethod) {
// Update the call site
JMethodCall newCall = new JMethodCall(x.getSourceInfo(), null, newMethod);
/*
* If the qualifier is a JMultiExpression, invoke on the last value. This
* ensures that clinits maintain the same execution order relative to
* parameters in deeply-inlined scenarios.
*/
// (a, b).foo() --> (a, foo(b))
if (x.getInstance() instanceof JMultiExpression) {
JMultiExpression multi = (JMultiExpression) x.getInstance();
int lastIndex = multi.exprs.size() - 1;
newCall.addArg(multi.exprs.get(lastIndex));
newCall.addArgs(x.getArgs());
multi.exprs.set(lastIndex, newCall);
return multi;
} else {
// The qualifier becomes the first arg
// a.foo(b) --> foo(a,b)
newCall.addArg(x.getInstance());
newCall.addArgs(x.getArgs());
return newCall;
}
}
protected Set<JMethod> toBeMadeStatic = new HashSet<JMethod>();
private final JProgram program;
private MakeCallsStatic(JProgram program) {
this.program = program;
}
private OptimizerStats execImpl() {
OptimizerStats stats = new OptimizerStats(NAME);
FindStaticDispatchSitesVisitor finder = new FindStaticDispatchSitesVisitor();
finder.accept(program);
CreateStaticImplsVisitor creator = new CreateStaticImplsVisitor(program);
for (JMethod method : toBeMadeStatic) {
creator.accept(method);
}
/*
* Run the rewriter even if we didn't make any new static methods; other
* optimizations can unlock devirtualizations even if no more static impls
* are created.
*/
RewriteCallSites rewriter = new RewriteCallSites();
rewriter.accept(program);
stats.recordModified(rewriter.getNumMods());
assert (rewriter.didChange() || toBeMadeStatic.isEmpty());
return stats;
}
}