/*
* 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.SourceInfo;
import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.JArrayLength;
import com.google.gwt.dev.jjs.ast.JArrayRef;
import com.google.gwt.dev.jjs.ast.JArrayType;
import com.google.gwt.dev.jjs.ast.JBinaryOperation;
import com.google.gwt.dev.jjs.ast.JBinaryOperator;
import com.google.gwt.dev.jjs.ast.JBlock;
import com.google.gwt.dev.jjs.ast.JDeclarationStatement;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JForStatement;
import com.google.gwt.dev.jjs.ast.JIntLiteral;
import com.google.gwt.dev.jjs.ast.JLocal;
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.JNewArray;
import com.google.gwt.dev.jjs.ast.JParameter;
import com.google.gwt.dev.jjs.ast.JParameterRef;
import com.google.gwt.dev.jjs.ast.JPostfixOperation;
import com.google.gwt.dev.jjs.ast.JPrimitiveType;
import com.google.gwt.dev.jjs.ast.JProgram;
import com.google.gwt.dev.jjs.ast.JStatement;
import com.google.gwt.dev.jjs.ast.JUnaryOperation;
import com.google.gwt.dev.jjs.ast.JUnaryOperator;
import com.google.gwt.dev.jjs.ast.JVariableRef;
import com.google.gwt.dev.jjs.ast.JVisitor;
import com.google.gwt.dev.jjs.ast.RuntimeConstants;
import com.google.gwt.thirdparty.guava.common.collect.Iterables;
import java.util.Collections;
/**
* Implements JavaScript varargs calling convention by rewriting varargs calls and adding a
* prolog to varargs JsMethods.
* <p>
* At the calls sites, inline array creation is replaced by array literals, which in turn will be
* unwrapped as individual parameters at generation time.
* <p>
* To implement varargs methods, we analyze the usage of the varargs parameter to determine whether
* it can be accessed directly (with possibly an offset in the index) or it has to be copied.
*/
public class ImplementJsVarargs {
/**
* Analyzes a method body to check whether the varargs parameter can be used directly or not.
* <p>
* The arguments variable cannot be used directly if is referenced without indexing or accessing
* its length, or if it is written to.
*/
private class NeedsArgumentsCopyAnalyzer extends JVisitor {
private VarargsProcessingResult result = VarargsProcessingResult.SIMPLE_ACCESS;
private JParameter varargsParameter;
private int varargsParameterIndex;
private NeedsArgumentsCopyAnalyzer(JMethod method) {
assert method.isJsMethodVarargs();
this.varargsParameter = Iterables.getLast(method.getParams());
this.varargsParameterIndex = method.getParams().size() - 1;
if (varargsParameterIndex != 0) {
upgradeResult(VarargsProcessingResult.OFFSET_ACCESS);
}
}
@Override
public void endVisit(JParameterRef x, Context ctx) {
// Any reference that is not .length or indexed means that we need to copy the varargs array.
if (isVarargsReference(x)) {
upgradeResult(VarargsProcessingResult.GENERAL_ACCESS);
}
}
@Override
public boolean visit(JArrayLength x, Context ctx) {
if (isVarargsReference(x.getInstance())) {
// This is a safe reference.
return false;
}
return true;
}
@Override
public boolean visit(JArrayRef x, Context ctx) {
if (isVarargsReference(x.getInstance())) {
// This is a safe reference, so only check the index expression.
accept(x.getIndexExpr());
return false;
}
return true;
}
@Override
public boolean visit(JBinaryOperation x, Context ctx) {
if (isModifyingVarargs(x)) {
// The varargs parameter is written to, so upgrade to copy.
upgradeResult(VarargsProcessingResult.GENERAL_ACCESS);
return false;
}
return true;
}
@Override
public boolean visit(JUnaryOperation x, Context ctx) {
if (isModifyingVarargs(x)) {
// The varargs parameter is written to, so upgrade to copy.
upgradeResult(VarargsProcessingResult.GENERAL_ACCESS);
return false;
}
return true;
}
@Override
public boolean visit(JMethodCall x, Context ctx) {
// Allow
if (x.getTarget().isJsMethodVarargs() && x.getArgs().size() == 1
&& isVarargsReference(x.getArgs().get(0))) {
// The varargs parameter is passed directly and it is the only parameter, so if it is the
// only parameter in the current method it can be passed directly.
upgradeResult(VarargsProcessingResult.PASS_WHOLE);
if (x.getInstance() != null) {
accept(x.getInstance());
}
for (JExpression arg : x.getArgs().subList(1, x.getArgs().size())) {
accept(arg);
}
return false;
}
return true;
}
private boolean isModifyingVarargs(JBinaryOperation x) {
if (!x.getOp().isAssignment()) {
return false;
}
if (!(x.getLhs() instanceof JArrayRef)) {
return false;
}
JArrayRef arrayRef = (JArrayRef) x.getLhs();
JExpression instance = arrayRef.getInstance();
return isVarargsReference(instance);
}
private boolean isModifyingVarargs(JUnaryOperation x) {
if (!x.getOp().isModifying()) {
return false;
}
if (!(x.getArg() instanceof JArrayRef)) {
return false;
}
JArrayRef arrayRef = (JArrayRef) x.getArg();
JExpression instance = arrayRef.getInstance();
return isVarargsReference(instance);
}
private boolean isVarargsReference(JExpression instance) {
if (!(instance instanceof JParameterRef)) {
return false;
}
return (((JParameterRef) instance).getTarget() == varargsParameter);
}
private void upgradeResult(VarargsProcessingResult upgradeTo) {
result = VarargsProcessingResult.join(result, upgradeTo);
}
}
// Defines the analysis lattice
// SIMPLE_ACCESS (only arguments[i] or arguments.length, no writing)
// / \
// (complete passing of / \
// arguments) PASS_WHOLE OFFSET_ACCESS (Simple access but needs to offset index)
// \ /
// \ /
// GENERAL_ACCESS
//
private enum VarargsProcessingResult {
SIMPLE_ACCESS, PASS_WHOLE, OFFSET_ACCESS, GENERAL_ACCESS;
private static VarargsProcessingResult join(
VarargsProcessingResult thisResult, VarargsProcessingResult thatResult) {
if (thisResult.ordinal() > thatResult.ordinal()) {
VarargsProcessingResult swap = thisResult;
thisResult = thatResult;
thatResult = swap;
}
if ((thisResult == PASS_WHOLE && thatResult == OFFSET_ACCESS)) {
return GENERAL_ACCESS;
}
return thatResult;
}
}
private VarargsProcessingResult needsVarargsProcessing(JMethod method) {
NeedsArgumentsCopyAnalyzer analyzer = new NeedsArgumentsCopyAnalyzer(method);
analyzer.accept(method);
return analyzer.result;
}
private abstract class VarargsReplacer {
abstract JExpression replace(JParameterRef expression);
JExpression replace(JArrayRef expression) {
return new JArrayRef(expression.getSourceInfo(),
replace((JParameterRef) expression.getInstance()),
expression.getIndexExpr());
}
JExpression replace(JArrayLength expression) {
return new JArrayLength(expression.getSourceInfo(),
replace((JParameterRef) expression.getInstance()));
}
}
/**
* Replaces varargs parameter accesses with accesses to the copy.
*/
private class ReplaceVarargsVariable extends VarargsReplacer {
private JLocal localVariable;
ReplaceVarargsVariable(JLocal localVariable) {
this.localVariable = localVariable;
}
@Override
public JExpression replace(JParameterRef expression) {
return localVariable.createRef(expression.getSourceInfo());
}
}
/**
* Fixes this indexing of vararg accesses.
*/
private class ReindexAccess extends VarargsReplacer {
private int varargsIndex;
ReindexAccess(int varargsIndex) {
this.varargsIndex = varargsIndex;
}
@Override
public JExpression replace(JParameterRef expression) {
return expression;
}
JExpression replace(JArrayRef expression) {
SourceInfo sourceInfo = expression.getSourceInfo();
return new JArrayRef(expression.getSourceInfo(),
expression.getInstance(),
new JBinaryOperation(sourceInfo, JPrimitiveType.INT, JBinaryOperator.ADD,
expression.getIndexExpr(), new JIntLiteral(sourceInfo, varargsIndex)));
}
JExpression replace(JArrayLength expression) {
SourceInfo sourceInfo = expression.getSourceInfo();
return new JBinaryOperation(sourceInfo, JPrimitiveType.INT, JBinaryOperator.SUB,
expression, new JIntLiteral(sourceInfo, varargsIndex));
}
}
private class VarargsMethodNormalizer extends JModVisitor {
private JParameter varargsParameter;
private int varargsIndex;
private VarargsReplacer replacer;
private JLocal argumentsCopyVariable;
@Override
public boolean visit(JMethod x, Context ctx) {
if (!x.isJsMethodVarargs()) {
return false;
}
varargsParameter = Iterables.getLast(x.getParams());
varargsIndex = x.getParams().size() - 1;
// JsVarargs parameter can be assumend not null in the implementing method
varargsParameter.setType(varargsParameter.getType().strengthenToNonNull());
argumentsCopyVariable = null;
switch (needsVarargsProcessing(x)) {
case GENERAL_ACCESS:
argumentsCopyVariable = JProgram.createLocal(varargsParameter.getSourceInfo(),
varargsParameter.getName(), varargsParameter.getType(), false,
(JMethodBody) x.getBody());
replacer = new ReplaceVarargsVariable(argumentsCopyVariable);
return true;
case OFFSET_ACCESS:
replacer = new ReindexAccess(varargsIndex);
return true;
default:
return false;
}
}
@Override
public void endVisit(JParameterRef x, Context ctx) {
if (x.getTarget() == varargsParameter) {
maybeReplace(x, replacer.replace(x), ctx);
}
}
@Override
public void endVisit(JArrayRef x, Context ctx) {
if (x.getInstance() instanceof JParameterRef
&& ((JParameterRef) x.getInstance()).getTarget() == varargsParameter) {
maybeReplace(x, replacer.replace(x), ctx);
}
}
@Override
public void endVisit(JArrayLength x, Context ctx) {
if (x.getInstance() instanceof JParameterRef
&& ((JParameterRef) x.getInstance()).getTarget() == varargsParameter) {
maybeReplace(x, replacer.replace(x), ctx);
}
}
@Override
public void endVisit(JMethod x, Context ctx) {
if (!x.isJsMethodVarargs()) {
return;
}
// rename the varargs variable to _arguments_.
varargsParameter.setName("_arguments_");
}
private void maybeReplace(JExpression x, JExpression replacement, Context ctx) {
if (replacement != x) {
ctx.replaceMe(replacement);
}
}
@Override
public void endVisit(JMethodBody x, Context ctx) {
if (argumentsCopyVariable == null) {
return;
}
// Needs to populate the copy; add preamble.
//
// {
// <Type>[] args = new <Type>[arguments.length - offset];
// for (int $i = 0; $i < arguments.length - offset; i++) {
// args[i] = arguments[i + offset];
// }
// }
SourceInfo sourceInfo = varargsParameter.getSourceInfo();
JBlock preamble = new JBlock(sourceInfo);
JArrayType varargsArrayType = (JArrayType) varargsParameter.getType().getUnderlyingType();
// (1) varargs_ = new VarArgsType[varargs.length - varArgsParameterIndex]
JExpression lengthMinusVarargsIndex = varargsIndex == 0
? new JArrayLength(sourceInfo, varargsParameter.createRef(sourceInfo))
: new JBinaryOperation(sourceInfo, JPrimitiveType.INT, JBinaryOperator.SUB,
new JArrayLength(sourceInfo, varargsParameter.createRef(sourceInfo)),
new JIntLiteral(sourceInfo, varargsIndex));
JNewArray arrayVariable = JNewArray.createArrayWithDimensionExpressions(sourceInfo,
varargsArrayType, Collections.singletonList(lengthMinusVarargsIndex));
arrayVariable.getLeafTypeClassLiteral().setField(
program.getClassLiteralField(varargsArrayType.getLeafType()));
preamble.addStmt(new JDeclarationStatement(
sourceInfo, argumentsCopyVariable.createRef(sourceInfo), arrayVariable));
JLocal index = JProgram.createLocal(sourceInfo, "$i", JPrimitiveType.INT, false, x);
// (2) (copy loop body) varargs_[i] = varargs[i + varargsIndex];
JExpression iPlusVarargsIndex = varargsIndex == 0 ? index.createRef(sourceInfo)
: new JBinaryOperation(sourceInfo, JPrimitiveType.INT, JBinaryOperator.ADD,
index.createRef(sourceInfo), new JIntLiteral(sourceInfo, varargsIndex));
JBlock block = new JBlock(sourceInfo);
block.addStmt(new JBinaryOperation(
sourceInfo,
varargsArrayType.getElementType(),
JBinaryOperator.ASG,
new JArrayRef(sourceInfo, replacer.replace(varargsParameter.createRef(sourceInfo)),
index.createRef(sourceInfo)),
new JArrayRef(sourceInfo, varargsParameter.createRef(sourceInfo), iPlusVarargsIndex))
.makeStatement());
// (3) for (int $i = 0 ; i < arguments.length - index; i++) {
// varargs_[i] = varargs[i + varargsIndex];
// }
preamble.addStmt(new JForStatement(sourceInfo, Collections.<JStatement>singletonList(
new JDeclarationStatement(sourceInfo, index.createRef(sourceInfo), JIntLiteral.ZERO)),
new JBinaryOperation(sourceInfo, JPrimitiveType.INT,JBinaryOperator.LT,
index.createRef(sourceInfo),
new CloneExpressionVisitor().cloneExpression(lengthMinusVarargsIndex)),
new JPostfixOperation(sourceInfo, JUnaryOperator.INC, index.createRef(sourceInfo)),
block));
x.getStatements().add(0, preamble);
}
}
// Normalizes JsVarargsCalls so that
// (1) inline new array expressions resulting from a "regular" varargs invocation are replaced
// by plain array literals.
// (2) side effecting instances in JsVarargs instance method calls with array calling convention
// are hoited into temporary variables.
private class VarargsCallsNormalizer extends JModVisitor {
private JMethodBody currentMethodBody;
@Override
public boolean visit(JMethodBody x, Context ctx) {
currentMethodBody = x;
return true;
}
@Override
public void endVisit(JMethodBody x, Context ctx) {
currentMethodBody = null;
}
@Override
public void endVisit(JMethodCall x, Context ctx) {
JMethod method = x.getTarget();
if (!method.isJsMethodVarargs()) {
return;
}
int varargIndex = method.getParams().size() - 1;
JExpression varargArgument = x.getArgs().get(varargIndex);
if (varargArgument instanceof JNewArray) {
JNewArray varargArray = (JNewArray) varargArgument;
if (varargArray.getInitializers() != null) {
x.setArg(varargIndex, ArrayNormalizer.getInitializerArray(varargArray));
madeChanges();
return;
}
}
SourceInfo varargsArgumentsourceInfo = varargArgument.getSourceInfo();
if (varargArgument.getType().canBeNull()) {
// varargsArgument => Array.ensureNotNull(varargsArgument)
x.setArg(varargIndex, new JMethodCall(varargsArgumentsourceInfo, null,
program.getIndexedMethod(RuntimeConstants.ARRAY_ENSURE_NOT_NULL), varargArgument));
}
// Passed as an array to varargs method will result in an apply call, in which case hoist the
// qualifier to make sure it is only evaluated once.
JExpression instance = x.getInstance();
if (x.getTarget().needsDynamicDispatch() && !x.isStaticDispatchOnly()
&& instance != null && !(instance instanceof JVariableRef)) {
// Move the potentially sideffecting qualifier to a temporary variable so that
// the code generation for calls that need .apply don't need to hande the case.
SourceInfo sourceInfo = x.getSourceInfo();
JLocal tempInstance = JProgram.createLocal(sourceInfo, "$instance",
instance.getType(), false, currentMethodBody);
// (tempInstance = instance,
// tempInstance.method(pars);
ctx.replaceMe(JjsUtils.createOptimizedMultiExpression(
new JBinaryOperation(sourceInfo, instance.getType(),
JBinaryOperator.ASG, tempInstance.createRef(sourceInfo), instance),
new JMethodCall(x, tempInstance.createRef(sourceInfo), x.getArgs())));
}
}
}
public static void exec(JProgram program) {
new ImplementJsVarargs(program).execImpl();
}
private final JProgram program;
private ImplementJsVarargs(JProgram program) {
this.program = program;
}
private void execImpl() {
new VarargsMethodNormalizer().accept(program);
new VarargsCallsNormalizer().accept(program);
}
}