hotspot/src/share/vm/oops/instanceOop.hpp
author coleenp
Sun, 13 Apr 2008 17:43:42 -0400
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permissions -rw-r--r--
6420645: Create a vm that uses compressed oops for up to 32gb heapsizes Summary: Compressed oops in instances, arrays, and headers. Code contributors are coleenp, phh, never, swamyv Reviewed-by: jmasa, kamg, acorn, tbell, kvn, rasbold
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/*
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 * Copyright 1997-2000 Sun Microsystems, Inc.  All Rights Reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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 * CA 95054 USA or visit www.sun.com if you need additional information or
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 * have any questions.
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 *
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 */
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// An instanceOop is an instance of a Java Class
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// Evaluating "new HashTable()" will create an instanceOop.
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class instanceOopDesc : public oopDesc {
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 public:
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  // aligned header size.
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  static int header_size() { return sizeof(instanceOopDesc)/HeapWordSize; }
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  // If compressed, the offset of the fields of the instance may not be aligned.
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  static int base_offset_in_bytes() {
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    return UseCompressedOops ?
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             klass_gap_offset_in_bytes() :
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             sizeof(instanceOopDesc);
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  }
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  static bool contains_field_offset(int offset, int nonstatic_field_size) {
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    int base_in_bytes = base_offset_in_bytes();
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    if (UseCompressedOops) {
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      return (offset >= base_in_bytes &&
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              // field can be embedded in header, or is after header.
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              (offset < (int)sizeof(instanceOopDesc) ||
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              (offset-(int)sizeof(instanceOopDesc))/wordSize < nonstatic_field_size));
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    } else {
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      return (offset >= base_in_bytes &&
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              (offset-base_in_bytes)/wordSize < nonstatic_field_size);
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    }
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  }
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};