/*

 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 * 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.

 *

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#ifndef SHARE_OOPS_COMPRESSEDOOPS_HPP

#define SHARE_OOPS_COMPRESSEDOOPS_HPP

#include "memory/allocation.hpp"

#include "oops/oopsHierarchy.hpp"

#include "utilities/globalDefinitions.hpp"

class outputStream;

struct NarrowPtrStruct {

  // Base address for oop-within-java-object materialization.

  // NULL if using wide oops or zero based narrow oops.

  address _base;

  // Number of shift bits for encoding/decoding narrow ptrs.

  // 0 if using wide ptrs or zero based unscaled narrow ptrs,

  // LogMinObjAlignmentInBytes/LogKlassAlignmentInBytes otherwise.

  int     _shift;

  // Generate code with implicit null checks for narrow ptrs.

  bool    _use_implicit_null_checks;

};

class CompressedOops : public AllStatic {

  friend class VMStructs;

  // For UseCompressedOops.

  static NarrowPtrStruct _narrow_oop;

  static address _narrow_ptrs_base;

public:

  // For UseCompressedOops

  // Narrow Oop encoding mode:

  // 0 - Use 32-bits oops without encoding when

  //     NarrowOopHeapBaseMin + heap_size < 4Gb

  // 1 - Use zero based compressed oops with encoding when

  //     NarrowOopHeapBaseMin + heap_size < 32Gb

  // 2 - Use compressed oops with disjoint heap base if

  //     base is 32G-aligned and base > 0. This allows certain

  //     optimizations in encoding/decoding.

  //     Disjoint: Bits used in base are disjoint from bits used

  //     for oops ==> oop = (cOop << 3) | base.  One can disjoint

  //     the bits of an oop into base and compressed oop.

  // 3 - Use compressed oops with heap base + encoding.

  enum Mode {

    UnscaledNarrowOop  = 0,

    ZeroBasedNarrowOop = 1,

    DisjointBaseNarrowOop = 2,

    HeapBasedNarrowOop = 3,

    AnyNarrowOopMode = 4

  };

  static void initialize();

  static void set_base(address base);

  static void set_shift(int shift);

  static void set_use_implicit_null_checks(bool use);

  static void set_ptrs_base(address addr);

  static address  base()                     { return  _narrow_oop._base; }

  static bool     is_base(void* addr)        { return (base() == (address)addr); }

  static int      shift()                    { return  _narrow_oop._shift; }

  static bool     use_implicit_null_checks() { return  _narrow_oop._use_implicit_null_checks; }

  static address* ptrs_base_addr()           { return &_narrow_ptrs_base; }

  static address  ptrs_base()                { return _narrow_ptrs_base; }

  static Mode mode();

  static const char* mode_to_string(Mode mode);

  // Test whether bits of addr and possible offsets into the heap overlap.

  static bool     is_disjoint_heap_base_address(address addr);

  // Check for disjoint base compressed oops.

  static bool     base_disjoint();

  // Check for real heapbased compressed oops.

  // We must subtract the base as the bits overlap.

  // If we negate above function, we also get unscaled and zerobased.

  static bool     base_overlaps();

  static void     print_mode(outputStream* st);

  static bool is_null(oop v)       { return v == NULL; }

  static bool is_null(narrowOop v) { return v == 0; }

  static inline oop decode_raw(narrowOop v);

  static inline oop decode_not_null(narrowOop v);

  static inline oop decode(narrowOop v);

  static inline narrowOop encode_not_null(oop v);

  static inline narrowOop encode(oop v);

  // No conversions needed for these overloads

  static oop decode_not_null(oop v)             { return v; }

  static oop decode(oop v)                      { return v; }

  static narrowOop encode_not_null(narrowOop v) { return v; }

  static narrowOop encode(narrowOop v)          { return v; }

};

// For UseCompressedClassPointers.

class CompressedKlassPointers : public AllStatic {

  friend class VMStructs;

  static NarrowPtrStruct _narrow_klass;

  // CompressedClassSpaceSize set to 1GB, but appear 3GB away from _narrow_ptrs_base during CDS dump.

  static uint64_t _narrow_klass_range;

public:

  static void set_base(address base);

  static void set_shift(int shift);

  static void set_range(uint64_t range);

  static address  base()               { return  _narrow_klass._base; }

  static uint64_t range()              { return  _narrow_klass_range; }

  static int      shift()              { return  _narrow_klass._shift; }

  static bool is_null(Klass* v)      { return v == NULL; }

  static bool is_null(narrowKlass v) { return v == 0; }

  static inline Klass* decode_raw(narrowKlass v);

  static inline Klass* decode_not_null(narrowKlass v);

  static inline Klass* decode(narrowKlass v);

  static inline narrowKlass encode_not_null(Klass* v);

  static inline narrowKlass encode(Klass* v);

};

#endif // SHARE_OOPS_COMPRESSEDOOPS_HPP