/*
* 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.CanBeStatic;
import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.HasEnclosingType;
import com.google.gwt.dev.jjs.ast.HasName;
import com.google.gwt.dev.jjs.ast.JBinaryOperation;
import com.google.gwt.dev.jjs.ast.JBinaryOperator;
import com.google.gwt.dev.jjs.ast.JClassType;
import com.google.gwt.dev.jjs.ast.JDeclarationStatement;
import com.google.gwt.dev.jjs.ast.JDeclaredType;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JField;
import com.google.gwt.dev.jjs.ast.JFieldRef;
import com.google.gwt.dev.jjs.ast.JInterfaceType;
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.JNameOf;
import com.google.gwt.dev.jjs.ast.JNode;
import com.google.gwt.dev.jjs.ast.JParameter;
import com.google.gwt.dev.jjs.ast.JPrimitiveType;
import com.google.gwt.dev.jjs.ast.JProgram;
import com.google.gwt.dev.jjs.ast.JReferenceType;
import com.google.gwt.dev.jjs.ast.JType;
import com.google.gwt.dev.jjs.ast.JVariable;
import com.google.gwt.dev.jjs.ast.JVariableRef;
import com.google.gwt.dev.jjs.ast.js.JMultiExpression;
import com.google.gwt.dev.jjs.ast.js.JsniFieldRef;
import com.google.gwt.dev.jjs.ast.js.JsniMethodBody;
import com.google.gwt.dev.jjs.ast.js.JsniMethodRef;
import com.google.gwt.dev.js.ast.JsFunction;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Stack;
/**
* Remove globally unreferenced classes, interfaces, methods, parameters, and
* fields from the AST. This algorithm is based on having known "entry points"
* into the application which serve as the root(s) from which reachability is
* determined and everything else is rescued. Pruner determines reachability at
* a global level based on method calls and new operations; it does not perform
* any local code flow analysis. But, a local code flow optimization pass that
* can eliminate method calls would allow Pruner to prune additional nodes.
*
* Note: references to pruned types may still exist in the tree after this pass
* runs, however, it should only be in contexts that do not rely on any code
* generation for the pruned type. For example, it's legal to have a variable of
* a pruned type, or to try to cast to a pruned type. These will cause natural
* failures at run time; or later optimizations might be able to hard-code
* failures at compile time.
*
* Note: this class is limited to pruning parameters of static methods only.
*/
public class Pruner {
/**
* Remove assignments to pruned fields, locals and params. Nullify the return
* type of methods declared to return a globally uninstantiable type. Replace
* references to pruned variables and methods by references to the null field
* and null method, and drop assignments to pruned variables.
*/
private class CleanupRefsVisitor extends JModVisitor {
private Stack<JExpression> lValues = new Stack<JExpression>();
private final Map<JMethod, ArrayList<JParameter>> methodToOriginalParamsMap;
private final Set<? extends JNode> referencedNonTypes;
{
// Initialize a sentinel value to avoid having to check for empty stack.
lValues.push(null);
}
public CleanupRefsVisitor(Set<? extends JNode> referencedNodes,
Map<JMethod, ArrayList<JParameter>> methodToOriginalParamsMap) {
this.referencedNonTypes = referencedNodes;
this.methodToOriginalParamsMap = methodToOriginalParamsMap;
}
@Override
public void endVisit(JBinaryOperation x, Context ctx) {
// The LHS of assignments may have been pruned.
if (x.getOp() == JBinaryOperator.ASG) {
lValues.pop();
JExpression lhs = x.getLhs();
if (lhs instanceof JVariableRef) {
JVariableRef variableRef = (JVariableRef) lhs;
if (isVariablePruned(variableRef.getTarget())) {
// TODO: better null tracking; we might be missing some NPEs here.
JExpression replacement = makeReplacementForAssignment(
x.getSourceInfo(), variableRef, x.getRhs());
ctx.replaceMe(replacement);
}
}
}
}
@Override
public void endVisit(JDeclarationStatement x, Context ctx) {
lValues.pop();
// The variable may have been pruned.
if (isVariablePruned(x.getVariableRef().getTarget())) {
JExpression replacement = makeReplacementForAssignment(
x.getSourceInfo(), x.getVariableRef(), x.getInitializer());
ctx.replaceMe(replacement.makeStatement());
}
}
@Override
public void endVisit(JFieldRef x, Context ctx) {
// Handle l-values at a higher level.
if (lValues.peek() == x) {
return;
}
if (isPruned(x.getField())) {
// The field is gone; replace x by a null field reference.
JFieldRef fieldRef = transformToNullFieldRef(x, program);
ctx.replaceMe(fieldRef);
}
}
@Override
public void endVisit(JNameOf x, Context ctx) {
HasName node = x.getNode();
boolean pruned;
if (node instanceof JField) {
pruned = isPruned((JField) node);
} else if (node instanceof JMethod) {
pruned = isPruned((JMethod) node);
} else if (node instanceof JReferenceType) {
pruned = !program.typeOracle.isInstantiatedType((JReferenceType) node);
} else {
throw new InternalCompilerException("Unhandled JNameOf node: " + node);
}
if (pruned) {
ctx.replaceMe(program.getLiteralNull());
}
}
@Override
public void endVisit(JMethod x, Context ctx) {
JType type = x.getType();
if (type instanceof JReferenceType) {
if (!program.typeOracle.isInstantiatedType((JReferenceType) type)) {
x.setType(program.getTypeNull());
}
}
}
@Override
public void endVisit(JMethodCall x, Context ctx) {
JMethod method = x.getTarget();
// Is the method pruned entirely?
if (isPruned(method)) {
/*
* We assert that method must be non-static, otherwise it would have
* been rescued.
*/
ctx.replaceMe(transformToNullMethodCall(x, program));
return;
}
// Did we prune the parameters of the method we're calling?
if (methodToOriginalParamsMap.containsKey(method)) {
// This must be a static method
assert method.isStatic();
JMethodCall newCall = new JMethodCall(x, x.getInstance());
List<JParameter> originalParams = methodToOriginalParamsMap.get(method);
JMultiExpression currentMulti = null;
for (int i = 0, c = x.getArgs().size(); i < c; ++i) {
JExpression arg = x.getArgs().get(i);
JParameter param = null;
if (i < originalParams.size()) {
param = originalParams.get(i);
}
if (param != null && referencedNonTypes.contains(param)) {
// If there is an existing multi, terminate it.
if (currentMulti != null) {
currentMulti.exprs.add(arg);
newCall.addArg(currentMulti);
currentMulti = null;
} else {
newCall.addArg(arg);
}
} else if (arg.hasSideEffects()) {
// The argument is only needed for side effects, add it to a multi.
if (currentMulti == null) {
currentMulti = new JMultiExpression(x.getSourceInfo());
}
currentMulti.exprs.add(arg);
}
}
// Add any orphaned parameters on the end. Extra params are OK.
if (currentMulti != null) {
newCall.addArg(currentMulti);
}
ctx.replaceMe(newCall);
}
}
@Override
public void endVisit(JsniFieldRef x, Context ctx) {
if (isPruned(x.getField())) {
String ident = x.getIdent();
JField nullField = program.getNullField();
program.jsniMap.put(ident, nullField);
JsniFieldRef nullFieldRef = new JsniFieldRef(x.getSourceInfo(), ident,
nullField, x.getEnclosingType(), x.isLvalue());
ctx.replaceMe(nullFieldRef);
}
}
@Override
public void endVisit(JsniMethodRef x, Context ctx) {
// Redirect JSNI refs to uninstantiable types to the null method.
if (isPruned(x.getTarget())) {
String ident = x.getIdent();
JMethod nullMethod = program.getNullMethod();
program.jsniMap.put(ident, nullMethod);
JsniMethodRef nullMethodRef = new JsniMethodRef(x.getSourceInfo(),
ident, nullMethod, program.getJavaScriptObject());
ctx.replaceMe(nullMethodRef);
}
}
@Override
public boolean visit(JBinaryOperation x, Context ctx) {
if (x.getOp() == JBinaryOperator.ASG) {
lValues.push(x.getLhs());
}
return true;
}
@Override
public boolean visit(JDeclarationStatement x, Context ctx) {
lValues.push(x.getVariableRef());
return true;
}
private <T extends HasEnclosingType & CanBeStatic> boolean isPruned(T node) {
if (!referencedNonTypes.contains(node)) {
return true;
}
JReferenceType enclosingType = node.getEnclosingType();
return !node.isStatic() && enclosingType != null
&& !program.typeOracle.isInstantiatedType(enclosingType);
}
private boolean isVariablePruned(JVariable variable) {
if (variable instanceof JField) {
return isPruned((JField) variable);
}
return !referencedNonTypes.contains(variable);
}
private JExpression makeReplacementForAssignment(SourceInfo info,
JVariableRef variableRef, JExpression rhs) {
// Replace with a multi, which may wind up empty.
JMultiExpression multi = new JMultiExpression(info);
// If the lhs is a field ref, evaluate it first.
if (variableRef instanceof JFieldRef) {
JFieldRef fieldRef = (JFieldRef) variableRef;
JExpression instance = fieldRef.getInstance();
if (instance != null) {
multi.exprs.add(instance);
}
}
// If there is an rhs, evaluate it second.
if (rhs != null) {
multi.exprs.add(rhs);
}
if (multi.exprs.size() == 1) {
return multi.exprs.get(0);
} else {
return multi;
}
}
}
/**
* Remove any unreferenced classes and interfaces from JProgram. Remove any
* unreferenced methods and fields from their containing classes.
*/
private class PruneVisitor extends JModVisitor {
private boolean didChange = false;
private final Map<JMethod, ArrayList<JParameter>> methodToOriginalParamsMap = new HashMap<JMethod, ArrayList<JParameter>>();
private final Set<? extends JNode> referencedNonTypes;
private final Set<? extends JReferenceType> referencedTypes;
public PruneVisitor(Set<? extends JReferenceType> referencedTypes,
Set<? extends JNode> referencedNodes) {
this.referencedTypes = referencedTypes;
this.referencedNonTypes = referencedNodes;
}
@Override
public boolean didChange() {
return didChange;
}
public Map<JMethod, ArrayList<JParameter>> getMethodToOriginalParamsMap() {
return methodToOriginalParamsMap;
}
@Override
public boolean visit(JClassType type, Context ctx) {
assert (referencedTypes.contains(type));
boolean isInstantiated = program.typeOracle.isInstantiatedType(type);
for (int i = 0; i < type.getFields().size(); ++i) {
JField field = type.getFields().get(i);
if (!referencedNonTypes.contains(field)
|| pruneViaNoninstantiability(isInstantiated, field)) {
type.removeField(i);
didChange = true;
--i;
}
}
for (int i = 0; i < type.getMethods().size(); ++i) {
JMethod method = type.getMethods().get(i);
if (!methodIsReferenced(method)
|| pruneViaNoninstantiability(isInstantiated, method)) {
type.removeMethod(i);
didChange = true;
--i;
} else {
accept(method);
}
}
return false;
}
@Override
public boolean visit(JInterfaceType type, Context ctx) {
boolean isReferenced = referencedTypes.contains(type);
boolean isInstantiated = program.typeOracle.isInstantiatedType(type);
for (int i = 0; i < type.getFields().size(); ++i) {
JField field = type.getFields().get(i);
// all interface fields are static and final
if (!isReferenced || !referencedNonTypes.contains(field)) {
type.removeField(i);
didChange = true;
--i;
}
}
// Start at index 1; never prune clinit directly out of the interface.
for (int i = 1; i < type.getMethods().size(); ++i) {
JMethod method = type.getMethods().get(i);
// all other interface methods are instance and abstract
if (!isInstantiated || !methodIsReferenced(method)) {
type.removeMethod(i);
didChange = true;
--i;
}
}
return false;
}
@Override
public boolean visit(JMethod x, Context ctx) {
if (x.isStatic()) {
/*
* Don't prune parameters on unreferenced methods. The methods might not
* be reachable through the current method traversal routines, but might
* be used or checked elsewhere.
*
* Basically, if we never actually checked if the method parameters were
* used or not, don't prune them. Doing so would leave a number of
* dangling JParameterRefs that blow up in later optimizations.
*/
if (!referencedNonTypes.contains(x)) {
return true;
}
/*
* We cannot prune parameters from staticImpls that still have a live
* instance method, because doing so would screw up any subsequent
* devirtualizations. If the instance method has been pruned, then it's
* okay. Also, it's okay on the final pass since no more
* devirtualizations will occur.
*/
JMethod staticImplFor = program.staticImplFor(x);
// Unless the instance method has already been pruned, of course.
if (saveCodeGenTypes
&& staticImplFor != null
&& staticImplFor.getEnclosingType().getMethods().contains(
staticImplFor)) {
// instance method is still live
return true;
}
JsFunction func = x.isNative()
? ((JsniMethodBody) x.getBody()).getFunc() : null;
ArrayList<JParameter> originalParams = new ArrayList<JParameter>(
x.getParams());
for (int i = 0; i < x.getParams().size(); ++i) {
JParameter param = x.getParams().get(i);
if (!referencedNonTypes.contains(param)) {
x.removeParam(i);
didChange = true;
// Remove the associated JSNI parameter
if (func != null) {
func.getParameters().remove(i);
}
--i;
methodToOriginalParamsMap.put(x, originalParams);
}
}
}
return true;
}
@Override
public boolean visit(JMethodBody x, Context ctx) {
for (int i = 0; i < x.getLocals().size(); ++i) {
if (!referencedNonTypes.contains(x.getLocals().get(i))) {
x.removeLocal(i--);
didChange = true;
}
}
return false;
}
@Override
public boolean visit(JProgram program, Context ctx) {
for (JMethod method : program.getAllEntryMethods()) {
accept(method);
}
for (Iterator<JDeclaredType> it = program.getDeclaredTypes().iterator(); it.hasNext();) {
JDeclaredType type = it.next();
if (referencedTypes.contains(type)
|| program.typeOracle.isInstantiatedType(type)) {
accept(type);
} else {
it.remove();
didChange = true;
}
}
return false;
}
/**
* Returns <code>true</code> if a method is referenced.
*/
private boolean methodIsReferenced(JMethod method) {
// Is the method directly referenced?
if (referencedNonTypes.contains(method)) {
return true;
}
/*
* Special case: if method is the static impl for a live instance method,
* don't prune it unless this is the final prune.
*
* In some cases, the staticImpl can be inlined into the instance method
* but still be needed at other call sites.
*/
JMethod staticImplFor = program.staticImplFor(method);
if (staticImplFor != null && referencedNonTypes.contains(staticImplFor)) {
if (saveCodeGenTypes) {
return true;
}
}
return false;
}
private boolean pruneViaNoninstantiability(boolean isInstantiated,
CanBeStatic it) {
return (!isInstantiated && !it.isStatic());
}
}
public static boolean exec(JProgram program, boolean noSpecialTypes) {
return new Pruner(program, noSpecialTypes).execImpl();
}
/**
* Transform a reference to a pruned instance field into a reference to the
* null field, which will be used to replace <code>x</code>.
*/
public static JFieldRef transformToNullFieldRef(JFieldRef x, JProgram program) {
JExpression instance = x.getInstance();
/*
* We assert that field must be non-static if it's an rvalue, otherwise it
* would have been rescued.
*/
// assert !x.getField().isStatic();
/*
* HACK HACK HACK: ControlFlowAnalyzer has special hacks for dealing with
* ClassLiterals, which causes the body of ClassLiteralHolder's clinit to
* never be rescured. This in turn causes invalid references to static
* methods, which violates otherwise good assumptions about compiler
* operation.
*
* TODO: Remove this when ControlFlowAnalyzer doesn't special-case
* CLH.clinit().
*/
if (x.getField().isStatic() && instance == null) {
instance = program.getLiteralNull();
}
assert instance != null;
if (!instance.hasSideEffects()) {
instance = program.getLiteralNull();
}
JFieldRef fieldRef = new JFieldRef(x.getSourceInfo(), instance,
program.getNullField(), x.getEnclosingType(), primitiveTypeOrNullType(
program, x.getType()));
return fieldRef;
}
/**
* Transform a call to a pruned instance method (or static impl) into a call
* to the null method, which will be used to replace <code>x</code>.
*/
public static JMethodCall transformToNullMethodCall(JMethodCall x,
JProgram program) {
JExpression instance = x.getInstance();
List<JExpression> args = x.getArgs();
if (program.isStaticImpl(x.getTarget())) {
instance = args.get(0);
args = args.subList(1, args.size());
} else {
/*
* We assert that method must be non-static, otherwise it would have been
* rescued.
*/
// assert !x.getTarget().isStatic();
/*
* HACK HACK HACK: ControlFlowAnalyzer has special hacks for dealing with
* ClassLiterals, which causes the body of ClassLiteralHolder's clinit to
* never be rescured. This in turn causes invalid references to static
* methods, which violates otherwise good assumptions about compiler
* operation.
*
* TODO: Remove this when ControlFlowAnalyzer doesn't special-case
* CLH.clinit().
*/
if (x.getTarget().isStatic() && instance == null) {
instance = program.getLiteralNull();
}
}
assert (instance != null);
if (!instance.hasSideEffects()) {
instance = program.getLiteralNull();
}
JMethodCall newCall = new JMethodCall(x.getSourceInfo(), instance,
program.getNullMethod(), primitiveTypeOrNullType(program, x.getType()));
// Retain the original arguments, they will be evaluated for side effects.
newCall.addArgs(args);
return newCall;
}
/**
* Return the smallest type that is is a subtype of the argument.
*/
static JType primitiveTypeOrNullType(JProgram program, JType type) {
if (type instanceof JPrimitiveType) {
return type;
}
return program.getTypeNull();
}
private final JProgram program;
private final boolean saveCodeGenTypes;
private Pruner(JProgram program, boolean saveCodeGenTypes) {
this.program = program;
this.saveCodeGenTypes = saveCodeGenTypes;
}
private boolean execImpl() {
boolean madeChanges = false;
while (true) {
ControlFlowAnalyzer livenessAnalyzer = new ControlFlowAnalyzer(program);
if (saveCodeGenTypes) {
/*
* SPECIAL: Some classes contain methods used by code generation later.
* Unless those transforms have already been performed, we must rescue
* all contained methods for later user.
*/
traverseFromCodeGenTypes(livenessAnalyzer);
}
for (JMethod method : program.getAllEntryMethods()) {
livenessAnalyzer.traverseFrom(method);
}
livenessAnalyzer.traverseFromLeftoversFragmentHasLoaded();
program.typeOracle.setInstantiatedTypes(livenessAnalyzer.getInstantiatedTypes());
PruneVisitor pruner = new PruneVisitor(
livenessAnalyzer.getReferencedTypes(),
livenessAnalyzer.getLiveFieldsAndMethods());
pruner.accept(program);
if (!pruner.didChange()) {
break;
}
CleanupRefsVisitor cleaner = new CleanupRefsVisitor(
livenessAnalyzer.getLiveFieldsAndMethods(),
pruner.getMethodToOriginalParamsMap());
cleaner.accept(program.getDeclaredTypes());
madeChanges = true;
}
return madeChanges;
}
/**
* Traverse from all methods in the program's code-gen types. See
* {@link JProgram#CODEGEN_TYPES_SET}.
*/
private void traverseFromCodeGenTypes(ControlFlowAnalyzer livenessAnalyzer) {
for (JClassType type : program.codeGenTypes) {
livenessAnalyzer.traverseFromReferenceTo(type);
for (JMethod method : type.getMethods()) {
livenessAnalyzer.traverseFrom(method);
}
}
}
}