1 /*
   2  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_OOPS_OBJARRAYOOP_HPP
  26 #define SHARE_VM_OOPS_OBJARRAYOOP_HPP
  27 
  28 #include "memory/barrierSet.hpp"
  29 #include "oops/arrayOop.hpp"
  30 
  31 #if INCLUDE_ALL_GCS
  32 #include "gc_implementation/shenandoah/shenandoahBarrierSet.hpp"
  33 #endif
  34 
  35 // An objArrayOop is an array containing oops.
  36 // Evaluating "String arg[10]" will create an objArrayOop.
  37 
  38 class objArrayOopDesc : public arrayOopDesc {
  39   friend class ObjArrayKlass;
  40   friend class Runtime1;
  41   friend class psPromotionManager;
  42   friend class CSetMarkOopClosure;
  43   friend class G1ParScanPartialArrayClosure;
  44 
  45   template <class T> T* obj_at_addr(int index) const {
  46     assert(is_within_bounds(index), "index out of bounds");
  47     return &((T*)base())[index];
  48   }
  49 
  50 private:
  51   // Give size of objArrayOop in HeapWords minus the header
  52   static int array_size(int length) {
  53     const uint OopsPerHeapWord = HeapWordSize/heapOopSize;
  54     assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
  55            "Else the following (new) computation would be in error");
  56     uint res = ((uint)length + OopsPerHeapWord - 1)/OopsPerHeapWord;
  57 #ifdef ASSERT
  58     // The old code is left in for sanity-checking; it'll
  59     // go away pretty soon. XXX
  60     // Without UseCompressedOops, this is simply:
  61     // oop->length() * HeapWordsPerOop;
  62     // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
  63     // The oop elements are aligned up to wordSize
  64     const uint HeapWordsPerOop = heapOopSize/HeapWordSize;
  65     uint old_res;
  66     if (HeapWordsPerOop > 0) {
  67       old_res = length * HeapWordsPerOop;
  68     } else {
  69       old_res = align_size_up((uint)length, OopsPerHeapWord)/OopsPerHeapWord;
  70     }
  71     assert(res == old_res, "Inconsistency between old and new.");
  72 #endif  // ASSERT
  73     return res;
  74   }
  75 
  76  public:
  77   // Returns the offset of the first element.
  78   static int base_offset_in_bytes() {
  79     return arrayOopDesc::base_offset_in_bytes(T_OBJECT);
  80   }
  81 
  82   // base is the address following the header.
  83   HeapWord* base() const      { return (HeapWord*) arrayOopDesc::base(T_OBJECT); }
  84 
  85   // Accessing
  86   oop obj_at(int index) const {
  87     oop obj;
  88     // With UseCompressedOops decode the narrow oop in the objArray to an
  89     // uncompressed oop.  Otherwise this is simply a "*" operator.
  90     if (UseCompressedOops) {
  91       obj = load_decode_heap_oop(obj_at_addr<narrowOop>(index));
  92     } else {
  93       obj = load_decode_heap_oop(obj_at_addr<oop>(index));
  94     }
  95 #if INCLUDE_ALL_GCS
  96     if (UseShenandoahGC) {
  97       obj = ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
  98     }
  99 #endif
 100     return obj;
 101   }
 102 
 103   void obj_at_put(int index, oop value) {
 104     if (UseCompressedOops) {
 105       oop_store(obj_at_addr<narrowOop>(index), value);
 106     } else {
 107       oop_store(obj_at_addr<oop>(index), value);
 108     }
 109   }
 110   // Sizing
 111   static int header_size()    { return arrayOopDesc::header_size(T_OBJECT); }
 112   int object_size()           { return object_size(length()); }
 113 
 114   static int object_size(int length) {
 115     // This returns the object size in HeapWords.
 116     uint asz = array_size(length);
 117     uint osz = align_object_size(header_size() + asz);
 118     assert(osz >= asz,   "no overflow");
 119     assert((int)osz > 0, "no overflow");
 120     return (int)osz;
 121   }
 122 
 123   // special iterators for index ranges, returns size of object
 124 #define ObjArrayOop_OOP_ITERATE_DECL(OopClosureType, nv_suffix)     \
 125   int oop_iterate_range(OopClosureType* blk, int start, int end);
 126 
 127   ALL_OOP_OOP_ITERATE_CLOSURES_1(ObjArrayOop_OOP_ITERATE_DECL)
 128   ALL_OOP_OOP_ITERATE_CLOSURES_2(ObjArrayOop_OOP_ITERATE_DECL)
 129 };
 130 
 131 #endif // SHARE_VM_OOPS_OBJARRAYOOP_HPP
--- EOF ---