/*
* 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.codesplitter;
import com.google.gwt.dev.jjs.SourceInfo;
import com.google.gwt.dev.jjs.ast.JClassType;
import com.google.gwt.dev.jjs.ast.JConstructor;
import com.google.gwt.dev.jjs.ast.JField;
import com.google.gwt.dev.jjs.ast.JMethod;
import com.google.gwt.dev.jjs.ast.JProgram;
import com.google.gwt.dev.jjs.impl.JavaToJavaScriptMap;
import com.google.gwt.dev.js.JsHoister.Cloner;
import com.google.gwt.dev.js.ast.JsBinaryOperation;
import com.google.gwt.dev.js.ast.JsBinaryOperator;
import com.google.gwt.dev.js.ast.JsContext;
import com.google.gwt.dev.js.ast.JsEmpty;
import com.google.gwt.dev.js.ast.JsExprStmt;
import com.google.gwt.dev.js.ast.JsExpression;
import com.google.gwt.dev.js.ast.JsFunction;
import com.google.gwt.dev.js.ast.JsInvocation;
import com.google.gwt.dev.js.ast.JsModVisitor;
import com.google.gwt.dev.js.ast.JsName;
import com.google.gwt.dev.js.ast.JsNameRef;
import com.google.gwt.dev.js.ast.JsNumberLiteral;
import com.google.gwt.dev.js.ast.JsProgram;
import com.google.gwt.dev.js.ast.JsStatement;
import com.google.gwt.dev.js.ast.JsVars;
import com.google.gwt.dev.js.ast.JsVars.JsVar;
import com.google.gwt.dev.js.ast.JsVisitable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* Extracts multiple JS statements (called a fragment) out of the complete JS program based on
* supplied type/method/field/string liveness conditions.
*
* <p>
* <b>Liveness as defined here is not an intuitive concept.</b> A type or method (note that
* constructors are methods) is considered live for the current fragment when that type can only be
* instantiated or method executed when the current fragment has already been loaded. That does not
* always mean that it was caused by direct execution of the current fragment. It may instead mean
* that direction execution of some other fragment has been affected by the loading of the current
* fragment in a way that results in the instantiation of the type or execution of the method. It is
* this second case that can lead to seemingly contradictory but valid situations like having a type
* which is not currently live but which has a currently live constructor. For example it might be
* possible to instantiate type Foo even with fragment Bar being loaded (i.e. Foo is not live for
* Bar) but the loading of fragment Bar might be required to reach a particular one of Bar's
* multiple constructor (i.e. that constructor is live for Bar).
* </p>
*/
public class FragmentExtractor {
/**
* A logger for statements that the fragment extractor encounters. Install one using
* {@link FragmentExtractor#setStatementLogger(StatementLogger)} .
*/
public static interface StatementLogger {
void log(JsStatement statement, boolean include);
}
/**
* Mutates the provided defineClass statement to remove references to constructors which have not
* been made live by the current fragment. It also counts the constructor references that
* were not removed.
*/
private class DefineClassMinimizerVisitor extends JsModVisitor {
private final LivenessPredicate alreadyLoadedPredicate;
private final LivenessPredicate livenessPredicate;
private int liveConstructorCount;
private DefineClassMinimizerVisitor(
LivenessPredicate alreadyLoadedPredicate, LivenessPredicate livenessPredicate) {
this.alreadyLoadedPredicate = alreadyLoadedPredicate;
this.livenessPredicate = livenessPredicate;
}
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
JMethod method = map.nameToMethod(x.getName());
if (!(method instanceof JConstructor)) {
return;
}
// Only examines references to constructor methods.
JConstructor constructor = (JConstructor) method;
boolean fragmentExpandsConstructorLiveness =
!alreadyLoadedPredicate.isLive(constructor) && livenessPredicate.isLive(constructor);
if (fragmentExpandsConstructorLiveness) {
// Counts kept references to live constructors.
liveConstructorCount++;
} else {
// Removes references to dead constructors.
ctx.removeMe();
}
}
/**
* Enables varargs mutation.
*/
@Override
protected <T extends JsVisitable> void doAcceptList(List<T> collection) {
doAcceptWithInsertRemove(collection);
}
}
private static class MinimalDefineClassResult {
private int liveConstructorCount;
private JsExprStmt statement;
public MinimalDefineClassResult(JsExprStmt statement, int liveConstructorCount) {
this.statement = statement;
this.liveConstructorCount = liveConstructorCount;
}
}
private static class NullStatementLogger implements StatementLogger {
@Override
public void log(JsStatement statement, boolean include) {
}
}
/**
* Return the Java method corresponding to <code>stat</code>, or
* <code>null</code> if there isn't one. It recognizes JavaScript of the form
* <code>function foo(...) { ...}</code>, where <code>foo</code> is the name
* of the JavaScript translation of a Java method.
*/
public static JMethod methodFor(JsStatement stat, JavaToJavaScriptMap map) {
if (stat instanceof JsExprStmt) {
JsExpression exp = ((JsExprStmt) stat).getExpression();
if (exp instanceof JsFunction) {
JsFunction func = (JsFunction) exp;
if (func.getName() != null) {
JMethod method = map.nameToMethod(func.getName());
if (method != null) {
return method;
}
}
}
}
return map.vtableInitToMethod(stat);
}
private static JsExprStmt createDefineClassClone(JsExprStmt defineClassStatement) {
Cloner cloner = new Cloner();
cloner.accept(defineClassStatement.getExpression());
JsExprStmt minimalDefineClassStatement = cloner.getExpression().makeStmt();
return minimalDefineClassStatement;
}
private final JProgram jprogram;
private final JsProgram jsprogram;
private final JavaToJavaScriptMap map;
private StatementLogger statementLogger = new NullStatementLogger();
public FragmentExtractor(JProgram jprogram, JsProgram jsprogram, JavaToJavaScriptMap map) {
this.jprogram = jprogram;
this.jsprogram = jsprogram;
this.map = map;
}
/**
* Create a call to {@link AsyncFragmentLoader#onLoad}.
*/
public List<JsStatement> createOnLoadedCall(int fragmentId) {
JMethod loadMethod = jprogram.getIndexedMethod("AsyncFragmentLoader.onLoad");
JsName loadMethodName = map.nameForMethod(loadMethod);
SourceInfo sourceInfo = jsprogram.getSourceInfo();
JsInvocation call = new JsInvocation(sourceInfo);
call.setQualifier(wrapWithEntry(loadMethodName.makeRef(sourceInfo)));
call.getArguments().add(new JsNumberLiteral(sourceInfo, fragmentId));
List<JsStatement> newStats = Collections.<JsStatement> singletonList(call.makeStmt());
return newStats;
}
/**
* Assume that all code described by <code>alreadyLoadedPredicate</code> has
* been downloaded. Extract enough JavaScript statements that the code
* described by <code>livenessPredicate</code> can also run. The caller should
* ensure that <code>livenessPredicate</code> includes strictly more live code
* than <code>alreadyLoadedPredicate</code>.
*/
public List<JsStatement> extractStatements(
LivenessPredicate livenessPredicate, LivenessPredicate alreadyLoadedPredicate) {
List<JsStatement> extractedStats = new ArrayList<JsStatement>();
/**
* The type whose vtables can currently be installed.
*/
JClassType currentVtableType = null;
JClassType pendingVtableType = null;
JsExprStmt pendingDefineClass = null;
List<JsStatement> statements = jsprogram.getGlobalBlock().getStatements();
for (JsStatement statement : statements) {
boolean keep;
JClassType vtableTypeAssigned = vtableTypeAssigned(statement);
if (vtableTypeAssigned != null) {
// Keeps defineClass statements of live types or types with a live constructor.
MinimalDefineClassResult minimalDefineClassResult = createMinimalDefineClass(
livenessPredicate, alreadyLoadedPredicate, (JsExprStmt) statement);
boolean liveType = !alreadyLoadedPredicate.isLive(vtableTypeAssigned)
&& livenessPredicate.isLive(vtableTypeAssigned);
boolean liveConstructors = minimalDefineClassResult.liveConstructorCount > 0;
if (liveConstructors || liveType) {
statement = minimalDefineClassResult.statement;
keep = true;
} else {
pendingDefineClass = minimalDefineClassResult.statement;
pendingVtableType = vtableTypeAssigned;
keep = false;
}
} else if (containsRemovableVars(statement)) {
statement = removeSomeVars((JsVars) statement, livenessPredicate, alreadyLoadedPredicate);
keep = !(statement instanceof JsEmpty);
} else {
keep = isLive(statement, livenessPredicate) && !isLive(statement, alreadyLoadedPredicate);
}
statementLogger.log(statement, keep);
if (keep) {
if (vtableTypeAssigned != null) {
currentVtableType = vtableTypeAssigned;
}
JClassType vtableType = vtableTypeNeeded(statement);
if (vtableType != null && vtableType != currentVtableType) {
assert pendingVtableType == vtableType;
extractedStats.add(pendingDefineClass);
currentVtableType = pendingVtableType;
pendingDefineClass = null;
pendingVtableType = null;
}
extractedStats.add(statement);
}
}
return extractedStats;
}
/**
* Find all Java methods that still exist in the resulting JavaScript, even
* after JavaScript inlining and pruning.
*/
public Set<JMethod> findAllMethodsInJavaScript() {
Set<JMethod> methodsInJs = new HashSet<JMethod>();
for (int frag = 0; frag < jsprogram.getFragmentCount(); frag++) {
List<JsStatement> stats = jsprogram.getFragmentBlock(frag).getStatements();
for (JsStatement stat : stats) {
JMethod method = methodFor(stat);
if (method != null) {
methodsInJs.add(method);
}
}
}
return methodsInJs;
}
public void setStatementLogger(StatementLogger logger) {
statementLogger = logger;
}
/**
* Check whether this statement is a {@link JsVars} that contains individual vars that could be
* removed. If it does, then {@link #removeSomeVars(JsVars, LivenessPredicate, LivenessPredicate)}
* is sensible for this statement and should be used instead of
* {@link #isLive(JsStatement, LivenessPredicate)} .
*/
private boolean containsRemovableVars(JsStatement stat) {
if (stat instanceof JsVars) {
for (JsVar var : (JsVars) stat) {
JField field = map.nameToField(var.getName());
if (field != null) {
return true;
}
}
}
return false;
}
/**
* DefineClass calls mark the existence of a class and associate a castMaps with the class's
* various constructors. These multiple constructors are provided as JsNameRef varargs to the
* defineClass call but only the constructors that are live in the current fragment should be
* included.
*
* <p>
* This function strips out the dead constructors and returns the modified defineClass call. The
* stripped constructors will be kept by other defineClass calls in other fragments at other times.
* </p>
*/
private MinimalDefineClassResult createMinimalDefineClass(LivenessPredicate livenessPredicate,
LivenessPredicate alreadyLoadedPredicate, JsExprStmt defineClassStatement) {
DefineClassMinimizerVisitor defineClassMinimizerVisitor =
new DefineClassMinimizerVisitor(alreadyLoadedPredicate, livenessPredicate);
JsExprStmt minimalDefineClassStatement = createDefineClassClone(defineClassStatement);
defineClassMinimizerVisitor.accept(minimalDefineClassStatement);
return new MinimalDefineClassResult(
minimalDefineClassStatement, defineClassMinimizerVisitor.liveConstructorCount);
}
private boolean isLive(JsStatement stat, LivenessPredicate livenessPredicate) {
JClassType type = map.typeForStatement(stat);
if (type != null) {
// This is part of the code only needed once a type is instantiable
return livenessPredicate.isLive(type);
}
JMethod meth = methodFor(stat);
if (meth != null) {
/*
* This statement either defines a method or installs it in a vtable.
*/
if (!livenessPredicate.isLive(meth)) {
// The method is not live. Skip it.
return false;
}
// The method is live. Check that its enclosing type is instantiable.
// TODO(spoon): this check should not be needed once the CFA is updated
return !meth.needsVtable() || livenessPredicate.isLive(meth.getEnclosingType());
}
return livenessPredicate.miscellaneousStatementsAreLive();
}
/**
* Check whether a variable is needed. If the variable is an intern variable,
* then return whether the interned value is live. If the variable corresponds
* to a Java field, then return whether the Java field is live. Otherwise,
* assume the variable is needed and return <code>true</code>.
*
* Whenever this method is updated, also look at
* {@link #containsRemovableVars(JsStatement)}.
*/
private boolean isLive(JsVar var, LivenessPredicate livenessPredicate) {
JField field = map.nameToField(var.getName());
if (field != null) {
// It's a field
return livenessPredicate.isLive(field);
}
// It's not an intern variable at all
return livenessPredicate.miscellaneousStatementsAreLive();
}
/**
* Return the Java method corresponding to <code>stat</code>, or
* <code>null</code> if there isn't one. It recognizes JavaScript of the form
* <code>function foo(...) { ...}</code>, where <code>foo</code> is the name
* of the JavaScript translation of a Java method.
*/
private JMethod methodFor(JsStatement stat) {
return methodFor(stat, map);
}
/**
* If stat is a {@link JsVars} that initializes a bunch of intern vars, return
* a modified statement that skips any vars are needed by
* <code>currentLivenessPredicate</code> but not by
* <code>alreadyLoadedPredicate</code>.
*/
private JsStatement removeSomeVars(JsVars stat, LivenessPredicate currentLivenessPredicate,
LivenessPredicate alreadyLoadedPredicate) {
JsVars newVars = new JsVars(stat.getSourceInfo());
for (JsVar var : stat) {
if (isLive(var, currentLivenessPredicate) && !isLive(var, alreadyLoadedPredicate)) {
newVars.add(var);
}
}
if (newVars.getNumVars() == stat.getNumVars()) {
// no change
return stat;
}
if (newVars.iterator().hasNext()) {
/*
* The new variables are non-empty; return them.
*/
return newVars;
} else {
/*
* An empty JsVars seems possibly surprising; return a true empty
* statement instead.
*/
return new JsEmpty(stat.getSourceInfo());
}
}
/**
* If <code>state</code> is of the form <code>_ = String.prototype</code>,
* then return <code>String</code>. If the form is
* <code>defineClass(id, superId, cTM, ctor1, ctor2, ...)</code> return the type
* corresponding to that id. Otherwise return <code>null</code>.
*/
private JClassType vtableTypeAssigned(JsStatement stat) {
if (!(stat instanceof JsExprStmt)) {
return null;
}
JsExprStmt expr = (JsExprStmt) stat;
if (expr.getExpression() instanceof JsInvocation) {
// Handle a defineClass call.
JsInvocation call = (JsInvocation) expr.getExpression();
if (!(call.getQualifier() instanceof JsNameRef)) {
return null;
}
JsNameRef func = (JsNameRef) call.getQualifier();
JsFunction defineClassJsFunc =
jsprogram.getIndexedFunction("JavaClassHierarchySetupUtil.defineClass");
JsFunction defineClassJsProtoFunc =
jsprogram.getIndexedFunction(
"JavaClassHierarchySetupUtil.defineClassWithPrototype");
if (func.getName() != defineClassJsFunc.getName() && func.getName() !=
defineClassJsProtoFunc.getName()) {
return null;
}
return map.typeForStatement(stat);
}
// Handle String.
if (!(expr.getExpression() instanceof JsBinaryOperation)) {
return null;
}
JsBinaryOperation binExpr = (JsBinaryOperation) expr.getExpression();
if (binExpr.getOperator() != JsBinaryOperator.ASG) {
return null;
}
if (!(binExpr.getArg1() instanceof JsNameRef)) {
return null;
}
JsNameRef lhs = (JsNameRef) binExpr.getArg1();
JsName underBar = jsprogram.getScope().findExistingName("_");
assert underBar != null;
if (lhs.getName() != underBar) {
return null;
}
if (!(binExpr.getArg2() instanceof JsNameRef)) {
return null;
}
JsNameRef rhsRef = (JsNameRef) binExpr.getArg2();
if (!(rhsRef.getQualifier() instanceof JsNameRef)) {
return null;
}
if (!((JsNameRef) rhsRef.getQualifier()).getShortIdent().equals("String")) {
return null;
}
if (!rhsRef.getName().getShortIdent().equals("prototype")) {
return null;
}
return map.typeForStatement(stat);
}
private JClassType vtableTypeNeeded(JsStatement stat) {
JMethod meth = map.vtableInitToMethod(stat);
if (meth != null) {
if (meth.needsVtable()) {
return (JClassType) meth.getEnclosingType();
}
}
return null;
}
/**
* Wrap an expression with a call to $entry.
*/
private JsInvocation wrapWithEntry(JsExpression exp) {
SourceInfo sourceInfo = exp.getSourceInfo();
JsInvocation call = new JsInvocation(sourceInfo,
jsprogram.getScope().findExistingName("$entry").makeRef(sourceInfo), exp);
return call;
}
}