1 /*
   2  * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  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
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  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
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  23 
  24 #ifndef SHARE_GC_SHARED_GCTHREADLOCALDATA_HPP
  25 #define SHARE_GC_SHARED_GCTHREADLOCALDATA_HPP
  26 
  27 #include "utilities/globalDefinitions.hpp"
  28 
  29 // Thread local data area for GC-specific information. Each GC
  30 // is free to decide the internal structure and contents of this
  31 // area. It is represented as a 64-bit aligned opaque blob to
  32 // avoid circular dependencies between Thread and all GCs. For
  33 // the same reason, the size of the data area is hard coded to
  34 // provide enough space for all current GCs. Adjust the size if
  35 // needed, but avoid making it excessively large as it adds to
  36 // the memory overhead of creating a thread.
  37 //
  38 // Use Thread::gc_data<T>() to access the data, where T is the
  39 // GC-specific type describing the structure of the data. GCs
  40 // should consider placing frequently accessed fields first in
  41 // T, so that field offsets relative to Thread are small, which
  42 // often allows for a more compact instruction encoding.
  43 typedef uint64_t GCThreadLocalData[19]; // 152 bytes
  44 
  45 #endif // SHARE_GC_SHARED_GCTHREADLOCALDATA_HPP