| /* |
| * 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.dev.util.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(); |
| } |
| |
| 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); |
| } |
| } |