/*
 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */

#include "precompiled.hpp"
#include "gc/z/zThreadLocalData.hpp"
#include "gc/z/zObjArrayAllocator.hpp"
#include "gc/z/zUtils.inline.hpp"
#include "oops/arrayKlass.hpp"
#include "runtime/interfaceSupport.inline.hpp"

ZObjArrayAllocator::ZObjArrayAllocator(Klass* klass, size_t word_size, int length, Thread* thread) :
    ObjArrayAllocator(klass, word_size, length, false /* do_zero */, thread) {}

oop ZObjArrayAllocator::finish(HeapWord* mem) const {
  // Initialize object header and length field
  ObjArrayAllocator::finish(mem);

  // Keep the array alive across safepoints through an invisible
  // root. Invisible roots are not visited by the heap itarator
  // and the marking logic will not attempt to follow its elements.
  ZThreadLocalData::set_invisible_root(_thread, (oop*)&mem);

  // A max segment size of 64K was chosen because microbenchmarking
  // suggested that it offered a good trade-off between allocation
  // time and time-to-safepoint
  const size_t segment_max = ZUtils::bytes_to_words(64 * K);
  const size_t skip = arrayOopDesc::header_size(ArrayKlass::cast(_klass)->element_type());
  size_t remaining = _word_size - skip;

  while (remaining > 0) {
    // Clear segment
    const size_t segment = MIN2(remaining, segment_max);
    Copy::zero_to_words(mem + (_word_size - remaining), segment);
    remaining -= segment;

    if (remaining > 0) {
      // Safepoint
      ThreadBlockInVM tbivm((JavaThread*)_thread);
    }
  }

  ZThreadLocalData::clear_invisible_root(_thread);

  return oop(mem);
}