001/*
002 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
003 *
004 *  This file is licensed to You under the Eclipse Public License (EPL);
005 *  You may not use this file except in compliance with the License. You
006 *  may obtain a copy of the License at
007 *
008 *      http://www.opensource.org/licenses/eclipse-1.0.php
009 *
010 *  See the COPYRIGHT.txt file distributed with this work for information
011 *  regarding copyright ownership.
012 */
013package org.jikesrvm.mm.mminterface;
014
015import static org.jikesrvm.runtime.UnboxedSizeConstants.LOG_BYTES_IN_WORD;
016
017
018/**
019 * This class merely exposes the MMTk constants into the Jikes RVM
020 * package space so that they can be accessed by the VM in an
021 * MM-neutral way.  It is separate from MemoryManager to break
022 * cyclic class-loading dependencies.
023 */
024public class MemoryManagerConstants {
025  /** {@code true} if the selected plan needs support for linearly scanning the heap */
026  public static final boolean NEEDS_LINEAR_SCAN = Selected.Constraints.get().needsLinearScan();
027  /** Number of bits in the GC header required by the selected plan */
028  public static final int GC_HEADER_BITS = Selected.Constraints.get().gcHeaderBits();
029  /** Number of additional bytes required in the header by the selected plan */
030  public static final int GC_HEADER_BYTES = Selected.Constraints.get().gcHeaderWords() << LOG_BYTES_IN_WORD;
031  /** {@code true} if the selected plan requires concurrent worker threads */
032  public static final boolean NEEDS_CONCURRENT_WORKERS = Selected.Constraints.get().needsConcurrentWorkers();
033  /** {@code true} if the selected plan needs support for generating a GC trace */
034  public static final boolean GENERATE_GC_TRACE = Selected.Constraints.get().generateGCTrace();
035  /** {@code true} if the selected plan may move objects */
036  public static final boolean MOVES_OBJECTS = Selected.Constraints.get().movesObjects();
037  /** {@code true} if the selected plan moves TIB objects */
038  public static final boolean MOVES_TIBS = false;
039  /** {@code true} if the selected plan moves code */
040  public static final boolean MOVES_CODE = false;
041}
042