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.

     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

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    22  */

    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[14]; // 112 bytes

    44 

    45 #endif // SHARE_GC_SHARED_GCTHREADLOCALDATA_HPP