/*
 * 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.impl.gflow.Analysis;
import com.google.gwt.dev.jjs.impl.gflow.AssumptionMap;
import com.google.gwt.dev.jjs.impl.gflow.FlowFunction;
import com.google.gwt.dev.jjs.impl.gflow.IntegratedAnalysis;
import com.google.gwt.dev.jjs.impl.gflow.IntegratedFlowFunction;
import com.google.gwt.dev.jjs.impl.gflow.cfg.Cfg;
import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgEdge;
import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgNode;
import com.google.gwt.dev.jjs.impl.gflow.cfg.CfgTransformer;

/**
 * Analysis which detects when variable is not used after the assignment,
 * and eliminates assignment.
 */
public class LivenessAnalysis implements Analysis<CfgNode<?>, CfgEdge, Cfg,
    LivenessAssumption>, IntegratedAnalysis<CfgNode<?>, CfgEdge, CfgTransformer,
    Cfg, LivenessAssumption> {
  private static final LivenessFlowFunction FLOW_FUNCTION =
    new LivenessFlowFunction();
  private static final LivenessIntegratedFlowFunction INTEGRATED_FLOW_FUNCTION =
    new LivenessIntegratedFlowFunction();

  @Override
  public FlowFunction<CfgNode<?>, CfgEdge, Cfg, LivenessAssumption> getFlowFunction() {
    return FLOW_FUNCTION;
  }

  @Override
  public IntegratedFlowFunction<CfgNode<?>, CfgEdge, CfgTransformer, Cfg,
                                LivenessAssumption>
  getIntegratedFlowFunction() {
    return INTEGRATED_FLOW_FUNCTION;
  }

  @Override
  public void setInitialGraphAssumptions(Cfg graph,
      AssumptionMap<CfgEdge, LivenessAssumption> assumptionMap) {
    // bottom assumptions.
  }
}
