/*
* 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.ast.Context;
import com.google.gwt.dev.jjs.ast.JBinaryOperation;
import com.google.gwt.dev.jjs.ast.JCastOperation;
import com.google.gwt.dev.jjs.ast.JClassType;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JModVisitor;
import com.google.gwt.dev.jjs.ast.JPostfixOperation;
import com.google.gwt.dev.jjs.ast.JPrefixOperation;
import com.google.gwt.dev.jjs.ast.JPrimitiveType;
import com.google.gwt.dev.jjs.ast.JProgram;
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;
/**
* Most autoboxing is handled by {@link GenerateJavaAST}. The only cases it does
* not handle are <code>++</code>, <code>--</code>, and compound assignment
* operations (<code>+=</code>, etc.) when applied to a boxed type. This class
* fixes such cases in two steps. First, an internal subclass of
* {@link CompoundAssignmentNormalizer} simplifies such expressions to a simple
* assignment expression. Second, this visitor replaces an assignment to an
* unboxing method (<code>unbox(x) = unbox(x) + 1</code>) with an assignment to
* the underlying box (<code>x = box(unbox(x) + 1)</code>).
*
* <p>
* Update: GenerateJavaAST can also leave invalid AST structures of the form
* <code>(Foo) x = foo</code> due to the way generics are handled. This can
* happen when assigning into a field of a generic type. We'll go ahead and
* resolve that case here as well.
* </p>
*/
public class FixAssignmentsToUnboxOrCast extends JModVisitor {
/**
* Normalize compound assignments where the lhs is an unbox operation.
*/
private static class CompoundAssignmentsToUnboxOrCastNormalizer
extends CompoundAssignmentNormalizer {
private final AutoboxUtils autoboxUtils;
protected CompoundAssignmentsToUnboxOrCastNormalizer(JProgram program) {
autoboxUtils = new AutoboxUtils(program);
}
/**
* If the lhs is an unbox operation, then return the box rather than the
* original value.
*/
@Override
protected JExpression expressionToReturn(JExpression lhs) {
JExpression boxed = autoboxUtils.undoUnbox(lhs);
if (boxed != null) {
return boxed;
}
return lhs;
}
@Override
protected boolean shouldBreakUp(JBinaryOperation x) {
return isUnboxOrCastExpression(x.getLhs());
}
@Override
protected boolean shouldBreakUp(JPostfixOperation x) {
return isUnboxOrCastExpression(x.getArg());
}
@Override
protected boolean shouldBreakUp(JPrefixOperation x) {
return isUnboxOrCastExpression(x.getArg());
}
private boolean isUnboxOrCastExpression(JExpression x) {
return (autoboxUtils.undoUnbox(x) != null) || x instanceof JCastOperation;
}
}
public static void exec(JProgram program) {
Event fixAssignmentToUnboxEvent =
SpeedTracerLogger.start(CompilerEventType.FIX_ASSIGNMENT_TO_UNBOX);
new CompoundAssignmentsToUnboxOrCastNormalizer(program).accept(program);
new FixAssignmentsToUnboxOrCast(program).accept(program);
fixAssignmentToUnboxEvent.end();
}
private final AutoboxUtils autoboxUtils;
private FixAssignmentsToUnboxOrCast(JProgram program) {
this.autoboxUtils = new AutoboxUtils(program);
}
private JBinaryOperation maybeFixLhsCast(JBinaryOperation x) {
if (!(x.getLhs() instanceof JCastOperation)) {
return x;
}
// Assignment-to-cast-operation, e.g.
// (Foo) x = foo -> x = foo
// (Foo) x += foo -> x += foo
JCastOperation cast = (JCastOperation) x.getLhs();
return new JBinaryOperation(x.getSourceInfo(), x.getType(), x.getOp(), cast.getExpr(),
x.getRhs());
}
private JBinaryOperation maybeUndoBox(JBinaryOperation x) {
JExpression lhs = x.getLhs();
JExpression boxed = autoboxUtils.undoUnbox(lhs);
if (boxed == null) {
return x;
}
// Assignment-to-unbox, e.g.
// unbox(x) = foo -> x = box(foo)
JClassType boxedType = (JClassType) boxed.getType();
return new JBinaryOperation(x.getSourceInfo(), boxedType, x.getOp(), boxed,
autoboxUtils.box(x.getRhs(), (JPrimitiveType) lhs.getType()));
}
@Override
public void endVisit(JBinaryOperation x, Context ctx) {
if (!x.isAssignment()) {
return;
}
JBinaryOperation result = maybeFixLhsCast(maybeUndoBox(x));
if (result != x) {
ctx.replaceMe(result);
}
}
}