| /* |
| * 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.liveness; |
| |
| import com.google.gwt.dev.jjs.ast.Context; |
| import com.google.gwt.dev.jjs.ast.JBinaryOperation; |
| import com.google.gwt.dev.jjs.ast.JDeclarationStatement; |
| import com.google.gwt.dev.jjs.ast.JExpression; |
| import com.google.gwt.dev.jjs.ast.JExpressionStatement; |
| import com.google.gwt.dev.jjs.ast.JModVisitor; |
| import com.google.gwt.dev.jjs.ast.JNode; |
| import com.google.gwt.dev.jjs.impl.gflow.TransformationFunction.Transformation; |
| 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.CfgNopNode; |
| import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgTransformer; |
| import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgUtil; |
| import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgWriteNode; |
| import com.google.gwt.dev.util.Preconditions; |
| |
| /** |
| * Kill assignment. Leave rhs expression evaluation if it has side effects. |
| */ |
| public class LivenessTransformation implements |
| Transformation<CfgTransformer, Cfg> { |
| private final Cfg graph; |
| private final CfgWriteNode writeToKill; |
| |
| public LivenessTransformation(Cfg cfg, CfgWriteNode writeToKill) { |
| this.graph = cfg; |
| this.writeToKill = writeToKill; |
| } |
| |
| public CfgTransformer getGraphTransformer() { |
| return new CfgTransformer() { |
| public boolean transform(CfgNode<?> node, Cfg cfgGraph) { |
| JModVisitor visitor = new JModVisitor() { |
| @Override |
| public void endVisit(JBinaryOperation x, Context ctx) { |
| if (!shouldKill(x)) { |
| return; |
| } |
| |
| ctx.replaceMe(x.getRhs()); |
| } |
| |
| @Override |
| public void endVisit(JDeclarationStatement x, Context ctx) { |
| if (writeToKill.getValue() != x.getInitializer() || |
| x != writeToKill.getJNode()) { |
| return; |
| } |
| |
| if (x.getInitializer().hasSideEffects()) { |
| ctx.insertBefore(x.getInitializer().makeStatement()); |
| } |
| |
| x.initializer = null; |
| madeChanges(); |
| } |
| |
| @Override |
| public boolean visit(JExpressionStatement x, Context ctx) { |
| JExpression expr = x.getExpr(); |
| if (expr instanceof JBinaryOperation) { |
| JBinaryOperation binop = (JBinaryOperation) expr; |
| if (shouldKill(binop) && |
| !binop.getRhs().hasSideEffects()) { |
| ctx.removeMe(); |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| private boolean shouldKill(JBinaryOperation x) { |
| return writeToKill.getJNode() == x; |
| } |
| }; |
| |
| CfgNode<?> parentNode = CfgUtil.findParentOfContainingStatement(node); |
| Preconditions.checkNotNull(parentNode, |
| "Can't find parent of stmt of %s", node); |
| JNode parentJNode = parentNode.getJNode(); |
| visitor.accept(parentJNode); |
| Preconditions.checkState(visitor.didChange(), |
| "Can't remove write in %s", node.getJNode()); |
| return visitor.didChange(); |
| } |
| }; |
| } |
| |
| public Cfg getNewSubgraph() { |
| CfgNode<?> newNode = new CfgNopNode(writeToKill.getParent(), |
| writeToKill.getJNode()); |
| return CfgUtil.createSingleNodeReplacementGraph(graph, writeToKill, |
| newNode); |
| } |
| } |