/*
* 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.JConstructor;
import com.google.gwt.dev.jjs.ast.JDeclaredType;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JMethod;
import com.google.gwt.dev.jjs.ast.JMethod.Specialization;
import com.google.gwt.dev.jjs.ast.JMethodBody;
import com.google.gwt.dev.jjs.ast.JMethodCall;
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.JThisRef;
import com.google.gwt.dev.jjs.ast.JType;
import com.google.gwt.dev.jjs.ast.JVisitor;
import com.google.gwt.dev.jjs.ast.RuntimeConstants;
import com.google.gwt.dev.jjs.ast.js.JMultiExpression;
import com.google.gwt.dev.jjs.ast.js.JsniMethodBody;
import com.google.gwt.dev.jjs.impl.codesplitter.CodeSplitter;
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 com.google.gwt.thirdparty.guava.common.annotations.VisibleForTesting;
import com.google.gwt.thirdparty.guava.common.collect.Lists;
import com.google.gwt.thirdparty.guava.common.collect.Maps;
import com.google.gwt.thirdparty.guava.common.collect.Sets;
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 static 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 JChangeTrackingVisitor {
private final JParameter thisParam;
private final Map<JParameter, JParameter> varMap;
public RewriteMethodBody(JParameter thisParam, Map<JParameter, JParameter> varMap,
OptimizerContext optimizerCtx) {
super(optimizerCtx);
this.thisParam = thisParam;
this.varMap = varMap;
}
@Override
public void endVisit(JParameterRef x, Context ctx) {
JParameter param = varMap.get(x.getTarget());
ctx.replaceMe(param.makeRef(x.getSourceInfo()));
}
@Override
public void endVisit(JThisRef x, Context ctx) {
ctx.replaceMe(thisParam.makeRef(x.getSourceInfo()));
}
}
private final JProgram program;
private final OptimizerContext optimizerCtx;
private CreateStaticImplsVisitor(JProgram program, OptimizerContext optimizerCtx) {
this.program = program;
this.optimizerCtx = optimizerCtx;
}
CreateStaticImplsVisitor(JProgram program) {
this.program = program;
this.optimizerCtx = null;
}
@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) {
assert !x.isJsNative() : "Native methods can not be devirtualized";
// Let's do it!
JDeclaredType enclosingType = 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 = getStaticMethodName(x);
/*
* 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.setInliningMode(x.getInliningMode());
newMethod.setHasSideEffects(x.hasSideEffects());
newMethod.setSynthetic();
newMethod.addThrownExceptions(x.getThrownExceptions());
if (x.isJsOverlay()) {
newMethod.setJsOverlay();
}
JType thisParameterType = enclosingType.strengthenToNonNull();
// Setup parameters; map from the old params to the new params
JParameter thisParam = newMethod.createThisParameter(sourceInfo, thisParameterType);
Map<JParameter, JParameter> varMap = Maps.newIdentityHashMap();
for (JParameter oldVar : x.getParams()) {
JParameter newVar = newMethod.cloneParameter(oldVar);
varMap.put(oldVar, newVar);
}
// Set the new original param types based on the old original param types
List<JType> originalParamTypes = Lists.newArrayList();
originalParamTypes.add(thisParameterType);
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(param.makeRef(sourceInfo));
}
newBody.getBlock().addStmt(JjsUtils.makeMethodEndStatement(returnType, newCall));
/*
* Rewrite the method body. Update all thisRefs to paramRefs. Update
* paramRefs and localRefs to target the params/locals in the new method.
*/
if (newMethod.isJsniMethod()) {
// 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, optimizerCtx);
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);
if (optimizerCtx != null) {
optimizerCtx.markModified(x);
optimizerCtx.markModified(newMethod);
}
return false;
}
public JMethod getOrCreateStaticImpl(JProgram program, JMethod method) {
assert !method.isStatic();
JMethod staticImpl = program.getStaticImpl(method);
if (staticImpl == null) {
accept(method);
staticImpl = program.getStaticImpl(method);
}
return staticImpl;
}
}
private static String getStaticMethodName(JMethod x) {
return "$" + x.getName();
}
/**
* 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 (shouldBeMadeStatic(x, method)) {
// Let's do it!
toBeMadeStatic.add(method);
if (method.getSpecialization() != null &&
shouldBeMadeStatic(x,
method.getSpecialization().getTargetMethod())) {
toBeMadeStatic.add(method.getSpecialization().getTargetMethod());
}
}
}
private boolean shouldBeMadeStatic(JMethodCall x, JMethod method) {
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 false;
}
if (!method.isDevirtualizationAllowed()) {
// Method has been specifically excluded from statification.
return false;
}
// Did we already do this one?
if (program.getStaticImpl(method) != null || toBeMadeStatic.contains(method)) {
return false;
}
// Must be instance and final
if (x.canBePolymorphic()) {
return false;
}
if (!method.needsDynamicDispatch()) {
return false;
}
if (method.isAbstract()) {
return false;
}
if (method.isJsNative()) {
return false;
}
if (method == program.getNullMethod()) {
// Special case: we don't make calls to this method static.
return false;
}
if (!method.getEnclosingType().getMethods().contains(method)) {
// The target method was already pruned (TypeTightener will fix this).
return false;
}
return true;
}
}
/**
* 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 JChangeTrackingVisitor {
private boolean currentMethodIsInitiallyLive;
private ControlFlowAnalyzer initiallyLive;
public RewriteCallSites(OptimizerContext optimizerCtx) {
super(optimizerCtx);
}
/**
* 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(converter.convertCall(x, newMethod));
}
@Override
public boolean enter(JMethod x, Context ctx) {
currentMethodIsInitiallyLive = initiallyLive.getLiveFieldsAndMethods().contains(x);
return true;
}
@Override
public boolean visit(JProgram x, Context ctx) {
// TODO(rluble): This needs to be abstracted out the CodeSplitter.
initiallyLive = CodeSplitter.computeInitiallyLive(x);
return true;
}
}
/**
* Converts instance method calls to equivalent static method calls.
* Optionally adds a null check on the former "this" parameter.
*/
static class StaticCallConverter {
private final JMethod checkNotNull;
StaticCallConverter(JProgram program, boolean addNullChecksForThis) {
if (addNullChecksForThis) {
checkNotNull = program.getIndexedMethod(RuntimeConstants.EXCEPTIONS_CHECK_NOT_NULL);
} else {
checkNotNull = null;
}
}
/**
* Converts an instance method call to the equivalent static method call.
* @param original the instance method call to convert
* @param newMethod the static method to call instead
*/
JExpression convertCall(JMethodCall original, JMethod newMethod) {
JMethodCall newCall = new JMethodCall(original.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))
// Or in checked mode:
// (a, b).foo() --> (a, foo(checkNotNull(b)))
if (original.getInstance() instanceof JMultiExpression) {
JMultiExpression multi = (JMultiExpression) original.getInstance();
int lastIndex = multi.getNumberOfExpressions() - 1;
newCall.addArg(makeNullCheck(multi.getExpression(lastIndex), original));
newCall.addArgs(original.getArgs());
multi.setExpression(lastIndex, newCall);
return multi;
} else {
// The qualifier becomes the first argument.
// a.foo(b) --> foo(a,b)
// or in checked mode:
// a.foo(b) --> foo(checkNotNull(a),b)
newCall.addArg(makeNullCheck(original.getInstance(), original));
newCall.addArgs(original.getArgs());
return newCall;
}
}
private JExpression makeNullCheck(JExpression x, JMethodCall call) {
if (checkNotNull == null) {
return x;
}
// Existing code plays tricks with JSO's, so don't add the null check.
if (isJso(call)) {
return x;
}
JMethodCall check = new JMethodCall(x.getSourceInfo(), null, checkNotNull);
check.addArg(x);
return check;
}
private boolean isJso(JMethodCall call) {
JDeclaredType type = call.getTarget().getEnclosingType();
return type != null && type.isJsoType();
}
}
private static final String NAME = MakeCallsStatic.class.getSimpleName();
public static OptimizerStats exec(JProgram program, boolean addRuntimeChecks,
OptimizerContext optimizerCtx) {
Event optimizeEvent = SpeedTracerLogger.start(CompilerEventType.OPTIMIZE, "optimizer", NAME);
OptimizerStats stats = new MakeCallsStatic(program, addRuntimeChecks).execImpl(optimizerCtx);
optimizerCtx.setLastStepFor(NAME, optimizerCtx.getOptimizationStep());
optimizerCtx.incOptimizationStep();
optimizeEvent.end("didChange", "" + stats.didChange());
return stats;
}
@VisibleForTesting
static OptimizerStats exec(JProgram program, boolean addRuntimeChecks) {
return exec(program, addRuntimeChecks, new FullOptimizerContext(program));
}
protected Set<JMethod> toBeMadeStatic = Sets.newLinkedHashSet();
private final JProgram program;
private final StaticCallConverter converter;
private MakeCallsStatic(JProgram program, boolean addRuntimeChecks) {
this.program = program;
this.converter = new StaticCallConverter(program, addRuntimeChecks);
}
private OptimizerStats execImpl(OptimizerContext optimizerCtx) {
OptimizerStats stats = new OptimizerStats(NAME);
FindStaticDispatchSitesVisitor finder = new FindStaticDispatchSitesVisitor();
Set<JMethod> modifiedMethods =
optimizerCtx.getModifiedMethodsSince(optimizerCtx.getLastStepFor(NAME));
Set<JMethod> affectedMethods = affectedMethods(modifiedMethods, optimizerCtx);
optimizerCtx.traverse(finder, affectedMethods);
CreateStaticImplsVisitor creator = new CreateStaticImplsVisitor(program, optimizerCtx);
for (JMethod method : toBeMadeStatic) {
creator.accept(method);
}
for (JMethod method : toBeMadeStatic) {
// if method has specialization, add it to the static method
Specialization specialization = method.getSpecialization();
if (specialization != null) {
JMethod staticMethod = program.getStaticImpl(method);
List<JType> params = Lists.newArrayList(specialization.getParams());
params.add(0, staticMethod.getParams().get(0).getType());
staticMethod.setSpecialization(params, specialization.getReturns(),
staticMethod.getName());
staticMethod.getSpecialization().resolve(params,
specialization.getReturns(), program.getStaticImpl(specialization
.getTargetMethod()));
}
}
/*
* 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(optimizerCtx);
rewriter.accept(program);
stats.recordModified(rewriter.getNumMods());
assert (rewriter.didChange() || toBeMadeStatic.isEmpty());
JavaAstVerifier.assertProgramIsConsistent(program);
return stats;
}
/**
* Return the set of methods affected (because they are or callers of) by the modifications to the
* given set functions.
*/
private Set<JMethod> affectedMethods(Set<JMethod> modifiedMethods,
OptimizerContext optimizerCtx) {
assert (modifiedMethods != null);
Set<JMethod> affectedMethods = Sets.newLinkedHashSet();
affectedMethods.addAll(modifiedMethods);
affectedMethods.addAll(optimizerCtx.getCallers(modifiedMethods));
return affectedMethods;
}
}