dx/src/com/android/jack/dx/ssa/back/InterferenceGraph.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * 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.android.jack.dx.ssa.back;

import com.android.jack.dx.ssa.SetFactory;
import com.android.jack.dx.util.IntSet;

import java.util.ArrayList;

/**
 * A register interference graph
 */
public class InterferenceGraph {
  /**
   * {@code non-null;} interference graph, indexed by register in
   * both dimensions
   */
  private final ArrayList<IntSet> interference;

  /**
   * Creates a new graph.
   *
   * @param countRegs {@code >= 0;} the start count of registers in
   * the namespace. New registers can be added subsequently.
   */
  public InterferenceGraph(int countRegs) {
    interference = new ArrayList<IntSet>(countRegs);

    for (int i = 0; i < countRegs; i++) {
      interference.add(SetFactory.makeInterferenceSet(countRegs));
    }
  }

  /**
   * Adds a register pair to the interference/liveness graph. Parameter
   * order is insignificant.
   *
   * @param regV one register index
   * @param regW another register index
   */
  public void add(int regV, int regW) {
    ensureCapacity(Math.max(regV, regW) + 1);

    interference.get(regV).add(regW);
    interference.get(regW).add(regV);
  }

  /**
   * Dumps interference graph to stdout for debugging.
   */
  public void dumpToStdout() {
    int oldRegCount = interference.size();

    for (int i = 0; i < oldRegCount; i++) {
      StringBuilder sb = new StringBuilder();

      sb.append("Reg " + i + ":" + interference.get(i).toString());

      System.out.println(sb.toString());
    }
  }

  /**
   * Merges the interference set for a register into a given bit set
   *
   * @param reg {@code >= 0;} register
   * @param set {@code non-null;} interference set; will be merged
   * with set for given register
   */
  public void mergeInterferenceSet(int reg, IntSet set) {
    if (reg < interference.size()) {
      set.merge(interference.get(reg));
    }
  }

  /**
   * Ensures that the interference graph is appropriately sized.
   *
   * @param size requested minumum size
   */
  private void ensureCapacity(int size) {
    int countRegs = interference.size();

    interference.ensureCapacity(size);

    for (int i = countRegs; i < size; i++) {
      interference.add(SetFactory.makeInterferenceSet(size));
    }
  }
}