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T. J. Watson Libraries for Analysis

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/*
 * Copyright (c) 2002 - 2006 IBM Corporation.
 * 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
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 */
package com.ibm.wala.util.graph.dominators;

import com.ibm.wala.util.graph.NumberedGraph;
import org.jspecify.annotations.Nullable;

/**
 * Calculate dominators using Langauer and Tarjan's fastest algorithm. TOPLAS 1(1), July 1979. This
 * implementation uses path compression and results in a O(e * alpha(e,n)) complexity, where e is
 * the number of edges in the CFG and n is the number of nodes.
 *
 * Sources: TOPLAS article, Muchnick book
 */
public class NumberedDominators extends Dominators {

  public NumberedDominators(NumberedGraph G, T root) throws IllegalArgumentException {
    super(G, root);

    this.infoMap = new Object[G.getMaxNumber() + 1];
    for (T n : G) {
      infoMap[G.getNumber(n)] = new DominatorInfo(n);
    }

    analyze();
  }

  /*
   * Look-aside table for DominatorInfo objects
   */
  private final Object[] infoMap;

  @SuppressWarnings("unchecked")
  @Override
  protected final DominatorInfo getInfo(@Nullable T node) {
    assert node != null;
    return (DominatorInfo) infoMap[((NumberedGraph) G).getNumber(node)];
  }
}