001/*
002 * Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.
008 *
009 * This code is distributed in the hope that it will be useful, but WITHOUT
010 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
011 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
012 * version 2 for more details (a copy is included in the LICENSE file that
013 * accompanied this code).
014 *
015 * You should have received a copy of the GNU General Public License version
016 * 2 along with this work; if not, write to the Free Software Foundation,
017 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
018 *
019 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
020 * or visit www.oracle.com if you need additional information or have any
021 * questions.
022 */
023package com.oracle.graal.lir.dfa;
024
025import java.util.*;
026
027import com.oracle.graal.compiler.common.cfg.*;
028
029/**
030 * Ensures that an element is only in the worklist once.
031 *
032 * @param <T>
033 */
034class UniqueWorkList<T extends AbstractBlockBase<T>> extends ArrayDeque<T> {
035    private static final long serialVersionUID = 8009554570990975712L;
036    BitSet valid;
037
038    public UniqueWorkList(int size) {
039        this.valid = new BitSet(size);
040    }
041
042    @Override
043    public T poll() {
044        T result = super.poll();
045        if (result != null) {
046            valid.set(result.getId(), false);
047        }
048        return result;
049    }
050
051    @Override
052    public boolean add(T pred) {
053        if (!valid.get(pred.getId())) {
054            valid.set(pred.getId(), true);
055            return super.add(pred);
056        }
057        return false;
058    }
059
060    @Override
061    public boolean addAll(Collection<? extends T> collection) {
062        boolean changed = false;
063        for (T element : collection) {
064            if (!valid.get(element.getId())) {
065                valid.set(element.getId(), true);
066                super.add(element);
067                changed = true;
068            }
069        }
070        return changed;
071    }
072}