/*
* 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.gflow.constants;
import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.JModVisitor;
import com.google.gwt.dev.jjs.ast.JNode;
import com.google.gwt.dev.jjs.ast.JValueLiteral;
import com.google.gwt.dev.jjs.ast.JVariable;
import com.google.gwt.dev.jjs.ast.JVariableRef;
import com.google.gwt.dev.jjs.impl.CloneExpressionVisitor;
import com.google.gwt.dev.jjs.impl.gflow.cfg.Cfg;
import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgNode;
import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgReadNode;
import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgTransformer;
import com.google.gwt.thirdparty.guava.common.base.Preconditions;
/**
* Replace variable read by its constant value.
*/
final class FoldConstantTransformer implements CfgTransformer {
private final ConstantsAssumption assumption;
private CloneExpressionVisitor cloner;
private final CfgReadNode nodeToFold;
public FoldConstantTransformer(ConstantsAssumption assumptions,
CfgReadNode nodeToFold) {
this.assumption = assumptions;
this.nodeToFold = nodeToFold;
cloner = new CloneExpressionVisitor();
}
@Override
public boolean transform(CfgNode<?> node, Cfg cfgGraph) {
Preconditions.checkArgument(nodeToFold == node);
JModVisitor visitor = new JModVisitor() {
@Override
public boolean visit(JVariableRef x, Context ctx) {
JNode newNode = transform(x);
if (newNode != null) {
ctx.replaceMe(newNode);
return false;
}
return true;
}
};
CfgNode<?> parentNode = nodeToFold.getParent();
JNode jnode = parentNode.getJNode();
Preconditions.checkNotNull(jnode);
visitor.accept(jnode);
Preconditions.checkState(visitor.didChange());
return true;
}
private JNode transform(JVariableRef ref) {
if (nodeToFold.getJNode() != ref) {
return null;
}
JVariable var = ref.getTarget();
JValueLiteral literal = assumption.get(var);
Preconditions.checkNotNull(literal);
return cloner.cloneExpression(literal);
}
}