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/**********************************************************************
* This file is part of "Object Teams Development Tooling"-Software
*
* Copyright 2003, 2011 Fraunhofer Gesellschaft, Munich, Germany,
* for its Fraunhofer Institute for Computer Architecture and Software
* Technology (FIRST), Berlin, Germany and Technical University Berlin,
* Germany.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
* $Id: Lowering.java 23417 2010-02-03 20:13:55Z stephan $
*
* Please visit http://www.eclipse.org/objectteams for updates and contact.
*
* Contributors:
* Fraunhofer FIRST - Initial API and implementation
* Technical University Berlin - Initial API and implementation
**********************************************************************/
package org.eclipse.objectteams.otdt.internal.core.compiler.lifting;
import org.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.internal.compiler.ast.ASTNode;
import org.eclipse.jdt.internal.compiler.ast.AllocationExpression;
import org.eclipse.jdt.internal.compiler.ast.Assignment;
import org.eclipse.jdt.internal.compiler.ast.CastExpression;
import org.eclipse.jdt.internal.compiler.ast.ConditionalExpression;
import org.eclipse.jdt.internal.compiler.ast.Expression;
import org.eclipse.jdt.internal.compiler.ast.FieldReference;
import org.eclipse.jdt.internal.compiler.ast.LocalDeclaration;
import org.eclipse.jdt.internal.compiler.ast.MessageSend;
import org.eclipse.jdt.internal.compiler.ast.SingleNameReference;
import org.eclipse.jdt.internal.compiler.ast.ThisReference;
import org.eclipse.jdt.internal.compiler.ast.TypeReference;
import org.eclipse.jdt.internal.compiler.codegen.CodeStream;
import org.eclipse.jdt.internal.compiler.impl.Constant;
import org.eclipse.jdt.internal.compiler.lookup.Binding;
import org.eclipse.jdt.internal.compiler.lookup.BlockScope;
import org.eclipse.jdt.internal.compiler.lookup.LocalVariableBinding;
import org.eclipse.jdt.internal.compiler.lookup.ReferenceBinding;
import org.eclipse.jdt.internal.compiler.lookup.TypeBinding;
import org.eclipse.objectteams.otdt.core.compiler.IOTConstants;
import org.eclipse.objectteams.otdt.internal.core.compiler.lookup.RoleTypeBinding;
import org.eclipse.objectteams.otdt.internal.core.compiler.model.TeamModel;
import org.eclipse.objectteams.otdt.internal.core.compiler.statemachine.transformer.StandardElementGenerator;
import org.eclipse.objectteams.otdt.internal.core.compiler.util.AstGenerator;
/**
* Helper that generates the lowering statements necessary for the callout compiler-feature.
*
* Nested classes PushingExpression and PopExpression are used to store a value on
* the stack that must be evaluated only once but is first used for a null-check
* and later the same value is used for the actual translation.
*
* @author haebor
* @version $Id: Lowering.java 23417 2010-02-03 20:13:55Z stephan $
*/
public class Lowering implements IOTConstants {
/**
* This method generates a lowering translation for a given expression.
* We have three distinct alternatives:
* (1) arrays are translated via a method call (see ArrayLowering).
* (2) field access (applicable for same and sibling roles).
* (3) _OT$getBase() method (else).
*
* @param scope for lookup
* @param expression original
* @param unloweredType either a RoleTypeBinding or an ArrayBinding thereof.
* @param requiredType the base type (or ArrayBinding thereof).
* @param teamExpression can be used as a receiver for array lowering method calls
* @param needNullCheck if expression maybe null, a null-check is required at runtime.
* @return translation expression
*/
public Expression lowerExpression(
BlockScope scope,
final Expression expression,
TypeBinding unloweredType,
TypeBinding requiredType,
Expression teamExpression,
boolean needNullCheck)
{
// Note, this method is responsible for 'resolving' all AST nodes it generates!
int sourceStart = expression.sourceStart;
int sourceEnd = expression.sourceEnd;
AstGenerator gen = new AstGenerator(sourceStart, sourceEnd);
unloweredType = TeamModel.strengthenRoleType(scope.enclosingSourceType(), unloweredType);
Expression loweringExpr = null;
TypeBinding expressionType = expression.resolvedType;
// this assertion needed for pushing/casting using unchecked one-byte opcodes.
assert expressionType == null || expressionType.leafComponentType() instanceof ReferenceBinding;
LocalVariableBinding localVar = null;
Expression unloweredExpression = expression;
if (expression instanceof ThisReference || expression instanceof AllocationExpression)
needNullCheck = false;
if (needNullCheck) {
localVar = makeNewLocal(scope, unloweredType, sourceStart, sourceEnd);
SingleNameReference varRef = gen.singleNameReference(localVar.name);
varRef.binding = localVar;
varRef.bits = Binding.LOCAL;
varRef.constant = Constant.NotAConstant;
varRef.resolvedType = unloweredType;
unloweredExpression = varRef;
}
if(unloweredType.isArrayType())
{
// (1) array translation:
ArrayLowering trans = new ArrayLowering(teamExpression);
loweringExpr = trans.lowerArray(
scope,
unloweredExpression,
unloweredType,
requiredType);
}
else
{
RoleTypeBinding roleType = (RoleTypeBinding)unloweredType;
boolean needMethod = roleType.isRegularInterface()
|| !roleType.isSiblingRole(scope.enclosingSourceType());
if (needMethod) {
// (3) translation using _OT$.getBase() method:
MessageSend callLower = gen.messageSend(
unloweredExpression,
IOTConstants._OT_GETBASE,
new Expression[0]);
// manual resolving:
callLower.actualReceiverType = unloweredType;
callLower.constant = Constant.NotAConstant;
callLower.resolvedType = roleType.baseclass();
callLower.binding =
StandardElementGenerator.getGetBaseMethod(
scope,
roleType.roleModel,
roleType.baseclass());
loweringExpr = callLower;
} else {
// (2) translation using field _OT$base:
FieldReference invokeBaseOnRole =
new FieldReference(IOTConstants._OT_BASE, (((long)sourceStart) << 32) + sourceEnd);
ReferenceBinding roleClass = roleType.roleModel.getClassPartBinding();
TypeReference classRef = gen.typeReference(roleClass);
if (classRef != null) {
// field access needs cast to the role-class.
// FIXME(SH): use synthetic role field accessor instead!
CastExpression unloweredExpr;
unloweredExpr = new CastExpression(unloweredExpression, classRef, CastExpression.NEED_CLASS);
unloweredExpr.constant = Constant.NotAConstant;
unloweredExpr.resolvedType = roleClass;
unloweredExpr.bits |= ASTNode.GenerateCheckcast;
invokeBaseOnRole.receiver = unloweredExpr;
} else {
invokeBaseOnRole.receiver = unloweredExpression;
}
invokeBaseOnRole.actualReceiverType = roleClass;
invokeBaseOnRole.resolvedType = roleClass.baseclass();
invokeBaseOnRole.binding = scope.findField(
roleClass,
IOTConstants._OT_BASE,
invokeBaseOnRole,
true);
invokeBaseOnRole.constant = Constant.NotAConstant;
loweringExpr = invokeBaseOnRole;
}
}
if (needNullCheck) {
// ((local = (expression)) == null) ? (RequiredType)local : lower(local));
@SuppressWarnings("null") // needNullCheck => localVar != null
SingleNameReference lhs = gen.singleNameReference(localVar.name);
lhs.binding = localVar;
lhs.resolvedType = unloweredType;
lhs.bits = Binding.LOCAL|ASTNode.FirstAssignmentToLocal;
Assignment assignment = gen.assignment(lhs, expression);
assignment.constant = Constant.NotAConstant;
loweringExpr = new CheckedLoweringExpression(expression, gen.nullCheck(assignment), gen.nullLiteral(), loweringExpr, localVar);
loweringExpr.constant = Constant.NotAConstant;
loweringExpr.resolvedType = requiredType;
}
return loweringExpr;
}
@NonNull LocalVariableBinding makeNewLocal(BlockScope scope, TypeBinding variableType, int sourceStart, int sourceEnd) {
char[] name = ("_OT$unlowered$"+sourceStart).toCharArray(); //$NON-NLS-1$
LocalVariableBinding varBinding = new LocalVariableBinding(name, variableType, 0, false);
varBinding.declaration = new LocalDeclaration(name, sourceStart, sourceEnd); // needed for BlockScope.computeLocalVariablePositions() -> CodeStream.record()
scope.addLocalVariable(varBinding);
varBinding.setConstant(Constant.NotAConstant);
varBinding.useFlag = LocalVariableBinding.USED;
return varBinding;
}
/** A conditional expression that checks for null before performing the actual lowering. */
static class CheckedLoweringExpression extends ConditionalExpression {
private final LocalVariableBinding localVar;
Expression origExpression;
CheckedLoweringExpression(Expression origExpression,
Expression condition,
Expression valueIfTrue,
Expression valueIfFalse,
LocalVariableBinding localVar)
{
super(condition, valueIfTrue, valueIfFalse);
this.localVar = localVar;
this.origExpression = origExpression;
}
@Override
public void generateCode(BlockScope currentScope, CodeStream codeStream, boolean valueRequired) {
codeStream.addVisibleLocalVariable(this.localVar);
super.generateCode(currentScope, codeStream, valueRequired);
}
}
public static boolean isLoweringConditional(Expression expr) {
return expr instanceof CheckedLoweringExpression;
}
/**
* Extract the actual value, considering wrapping by CheckedLoweringExpression.
*
* @param expression
* @return the actual value to be lowered
*/
public static Expression unwrapExpression(Expression expression) {
if (expression instanceof CheckedLoweringExpression)
return ((CheckedLoweringExpression)expression).origExpression;
return null;
}
}
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