/*
 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
 *
 *  This file is licensed to You under the Eclipse Public License (EPL);
 *  You may not use this file except in compliance with the License. You
 *  may obtain a copy of the License at
 *
 *      http://www.opensource.org/licenses/eclipse-1.0.php
 *
 *  See the COPYRIGHT.txt file distributed with this work for information
 *  regarding copyright ownership.
 */
package org.mmtk.plan.generational;

import org.mmtk.plan.*;
import org.mmtk.policy.CopyLocal;
import org.mmtk.policy.Space;
import org.mmtk.utility.HeaderByte;
import org.mmtk.utility.deque.*;
import org.mmtk.utility.alloc.Allocator;
import org.mmtk.utility.statistics.Stats;
import org.mmtk.vm.VM;
import static org.mmtk.plan.generational.Gen.USE_OBJECT_BARRIER_FOR_AASTORE;
import static org.mmtk.plan.generational.Gen.USE_OBJECT_BARRIER_FOR_PUTFIELD;
import static org.mmtk.utility.Constants.*;

import org.vmmagic.pragma.*;
import org.vmmagic.unboxed.*;

/**
 * This abstract class implements <i>per-mutator thread</i> behavior
 * and state for <i>generational copying collectors</i>.<p>
 *
 * Specifically, this class defines mutator-time allocation into the nursery;
 * write barrier semantics, and per-mutator thread collection semantics
 * (flushing and restoring per-mutator allocator and remset state).
 *
 * @see Gen
 * @see GenCollector
 * @see StopTheWorldMutator
 * @see MutatorContext
 */
@Uninterruptible public class GenMutator extends StopTheWorldMutator {

  /*****************************************************************************
   *
   * Instance fields
   */

  /**
   *
   */
  protected final CopyLocal nursery = new CopyLocal(Gen.nurserySpace);

  private final ObjectReferenceDeque modbuf;    /* remember modified scalars */
  protected final WriteBuffer remset;           /* remember modified array fields */
  protected final AddressPairDeque arrayRemset; /* remember modified array ranges */

  /****************************************************************************
   *
   * Initialization
   */

  /**
   * Constructor<p>
   *
   * Note that each mutator is a producer of remsets, while each
   * collector is a consumer.  The <code>GenCollector</code> class
   * is responsible for construction of the consumer.
   * @see GenCollector
   */
  public GenMutator() {
    modbuf = new ObjectReferenceDeque("modbuf", global().modbufPool);
    remset = new WriteBuffer(global().remsetPool);
    arrayRemset = new AddressPairDeque(global().arrayRemsetPool);
  }

  /****************************************************************************
   *
   * Mutator-time allocation
   */

  /**
   * {@inheritDoc}
   */
  @Override
  @Inline
  public Address alloc(int bytes, int align, int offset, int allocator, int site) {
    if (allocator == Gen.ALLOC_NURSERY) {
      if (Stats.GATHER_MARK_CONS_STATS) Gen.nurseryCons.inc(bytes);
      return nursery.alloc(bytes, align, offset);
    }
    return super.alloc(bytes, align, offset, allocator, site);
  }

  @Override
  @Inline
  public void postAlloc(ObjectReference ref, ObjectReference typeRef,
      int bytes, int allocator) {
    if (allocator != Gen.ALLOC_NURSERY) {
      super.postAlloc(ref, typeRef, bytes, allocator);
    }
  }

  @Override
  public Allocator getAllocatorFromSpace(Space space) {
    if (space == Gen.nurserySpace) return nursery;
    return super.getAllocatorFromSpace(space);
  }

  /****************************************************************************
   *
   * Barriers
   */

  /**
   * Perform the write barrier fast path, which may involve remembering
   * a reference if necessary.
   *
   * @param src The object into which the new reference will be stored
   * @param slot The address into which the new reference will be
   * stored.
   * @param tgt The target of the new reference
   * @param mode The mode of the store (eg putfield, putstatic etc)
   */
  @Inline
  private void fastPath(ObjectReference src, Address slot, ObjectReference tgt, int mode) {
    if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbFast.inc();
    if ((mode == ARRAY_ELEMENT && USE_OBJECT_BARRIER_FOR_AASTORE) ||
        (mode == INSTANCE_FIELD && USE_OBJECT_BARRIER_FOR_PUTFIELD)) {
      if (HeaderByte.isUnlogged(src)) {
        if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbSlow.inc();
        HeaderByte.markAsLogged(src);
        modbuf.insert(src);
      }
    } else {
      if (!Gen.inNursery(slot) && Gen.inNursery(tgt)) {
        if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbSlow.inc();
        remset.insert(slot);
      }
    }
  }

  /**
   * {@inheritDoc}<p>
   *
   * In this case, we remember the address of the source of the
   * pointer if the new reference points into the nursery from
   * non-nursery space.
   */
  @Override
  @Inline
  public final void objectReferenceWrite(ObjectReference src, Address slot,
      ObjectReference tgt, Word metaDataA,
      Word metaDataB, int mode) {
    fastPath(src, slot, tgt, mode);
    VM.barriers.objectReferenceWrite(src, tgt, metaDataA, metaDataB, mode);
  }


  /**
   * Perform the root write barrier fast path, which may involve remembering
   * a reference if necessary.
   *
   * @param slot The address into which the new reference will be
   * stored.
   * @param tgt The target of the new reference
   */
  @Inline
  private void fastPath(Address slot, ObjectReference tgt) {
    if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbFast.inc();
    if (Gen.inNursery(tgt)) {
      if (Gen.GATHER_WRITE_BARRIER_STATS) Gen.wbSlow.inc();
      remset.insert(slot);
    }
  }

  /**
   * {@inheritDoc}<p>
   *
   * In this case, we remember the address of the source of the
   * pointer if the new reference points into the nursery from
   * non-nursery space.
   */
  @Override
  @Inline
  public final void objectReferenceNonHeapWrite(Address slot, ObjectReference tgt,
      Word metaDataA, Word metaDataB) {
    fastPath(slot, tgt);
    VM.barriers.objectReferenceNonHeapWrite(slot, tgt, metaDataA, metaDataB);
  }

  /**
   * {@inheritDoc}<p>
   *
   * In this case, we remember the address of the source of the
   * pointer if the new reference points into the nursery from
   * non-nursery space.
   */
  @Override
  @Inline
  public boolean objectReferenceTryCompareAndSwap(ObjectReference src, Address slot, ObjectReference old, ObjectReference tgt,
      Word metaDataA, Word metaDataB, int mode) {
    boolean result = VM.barriers.objectReferenceTryCompareAndSwap(src, old, tgt, metaDataA, metaDataB, mode);
    if (result)
      fastPath(src, slot, tgt, mode);
    return result;
  }

  /**
   * {@inheritDoc}<p>
   *
   * In this case, we remember the mutated source address range and
   * will scan that address range at GC time.
   */
  @Inline
  @Override
  public final boolean objectReferenceBulkCopy(ObjectReference src, Offset srcOffset, ObjectReference dst, Offset dstOffset, int bytes) {
    if (!Gen.inNursery(dst)) {
      Address start = dst.toAddress().plus(dstOffset);
      arrayRemset.insert(start, start.plus(bytes));
    }
    return false;
  }

  @Override
  public final void flushRememberedSets() {
    modbuf.flushLocal();
    remset.flushLocal();
    arrayRemset.flushLocal();
    assertRemsetsFlushed();
  }

  @Override
  public final void assertRemsetsFlushed() {
    if (VM.VERIFY_ASSERTIONS) {
      VM.assertions._assert(modbuf.isFlushed());
      VM.assertions._assert(remset.isFlushed());
      VM.assertions._assert(arrayRemset.isFlushed());
    }
  }

  /****************************************************************************
   *
   * Collection
   */

  /**
   * {@inheritDoc}
   */
  @Override
  @NoInline
  public void collectionPhase(short phaseId, boolean primary) {

    if (phaseId == Gen.PREPARE) {
      nursery.reset();
      if (global().traceFullHeap()) {
        super.collectionPhase(phaseId, primary);
        modbuf.flushLocal();
        remset.flushLocal();
        arrayRemset.flushLocal();
      } else {
        flushRememberedSets();
      }
      return;
    }

    if (phaseId == Gen.RELEASE) {
      if (global().traceFullHeap()) {
        super.collectionPhase(phaseId, primary);
      }
      assertRemsetsFlushed();
      return;
    }

    super.collectionPhase(phaseId, primary);
  }

  /****************************************************************************
   *
   * Miscellaneous
   */

  /** @return The active global plan as a <code>Gen</code> instance. */
  @Inline
  private static Gen global() {
    return (Gen) VM.activePlan.global();
  }
}