view src/share/vm/oops/objArrayOop.hpp @ 1091:6aa7255741f3

6906727: UseCompressedOops: some card-marking fixes related to object arrays Summary: Introduced a new write_ref_array(HeapWords* start, size_t count) method that does the requisite MemRegion range calculation so (some of the) clients of the erstwhile write_ref_array(MemRegion mr) do not need to worry. This removed all external uses of array_size(), which was also simplified and made private. Asserts were added to catch other possible issues. Further, less essential, fixes stemming from this investigation are deferred to CR 6904516 (to follow shortly in hs17). Reviewed-by: kvn, coleenp, jmasa
author ysr
date Thu, 03 Dec 2009 15:01:57 -0800
parents 89e0543e1737
children 7bfd295ec074
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 * Copyright 1997-2009 Sun Microsystems, Inc.  All Rights Reserved.
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit if you need additional information or
 * have any questions.

// An objArrayOop is an array containing oops.
// Evaluating "String arg[10]" will create an objArrayOop.

class objArrayOopDesc : public arrayOopDesc {
  friend class objArrayKlass;
  friend class Runtime1;
  friend class psPromotionManager;
  friend class CSMarkOopClosure;
  friend class G1ParScanPartialArrayClosure;

  template <class T> T* obj_at_addr(int index) const {
    assert(is_within_bounds(index), "index out of bounds");
    return &((T*)base())[index];

  // Give size of objArrayOop in HeapWords minus the header
  static int array_size(int length) {
    const int OopsPerHeapWord = HeapWordSize/heapOopSize;
    assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
           "Else the following (new) computation would be in error");
#ifdef ASSERT
    // The old code is left in for sanity-checking; it'll
    // go away pretty soon. XXX
    // Without UseCompressedOops, this is simply:
    // oop->length() * HeapWordsPerOop;
    // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
    // The oop elements are aligned up to wordSize
    const int HeapWordsPerOop = heapOopSize/HeapWordSize;
    int old_res;
    if (HeapWordsPerOop > 0) {
      old_res = length * HeapWordsPerOop;
    } else {
      old_res = align_size_up(length, OopsPerHeapWord)/OopsPerHeapWord;
#endif  // ASSERT
    int res = (length + OopsPerHeapWord - 1)/OopsPerHeapWord;
    assert(res == old_res, "Inconsistency between old and new.");
    return res;

  // Returns the offset of the first element.
  static int base_offset_in_bytes() {
    return arrayOopDesc::base_offset_in_bytes(T_OBJECT);

  // base is the address following the header.
  HeapWord* base() const      { return (HeapWord*) arrayOopDesc::base(T_OBJECT); }

  // Accessing
  oop obj_at(int index) const {
    // With UseCompressedOops decode the narrow oop in the objArray to an
    // uncompressed oop.  Otherwise this is simply a "*" operator.
    if (UseCompressedOops) {
      return load_decode_heap_oop(obj_at_addr<narrowOop>(index));
    } else {
      return load_decode_heap_oop(obj_at_addr<oop>(index));

  void obj_at_put(int index, oop value) {
    if (UseCompressedOops) {
      oop_store(obj_at_addr<narrowOop>(index), value);
    } else {
      oop_store(obj_at_addr<oop>(index), value);
  // Sizing
  static int header_size()    { return arrayOopDesc::header_size(T_OBJECT); }
  int object_size()           { return object_size(length()); }

  static int object_size(int length) {
    // This returns the object size in HeapWords.
    return align_object_size(header_size() + array_size(length));

  // special iterators for index ranges, returns size of object
#define ObjArrayOop_OOP_ITERATE_DECL(OopClosureType, nv_suffix)     \
  int oop_iterate_range(OopClosureType* blk, int start, int end);