/*

 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.

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

 *

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 *

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 * 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_VM_RUNTIME_ACCESS_HPP

#define SHARE_VM_RUNTIME_ACCESS_HPP

#include "memory/allocation.hpp"

#include "metaprogramming/decay.hpp"

#include "metaprogramming/integralConstant.hpp"

#include "oops/oopsHierarchy.hpp"

#include "utilities/debug.hpp"

#include "utilities/globalDefinitions.hpp"

// = GENERAL =

// Access is an API for performing accesses with declarative semantics. Each access can have a number of "decorators".

// A decorator is an attribute or property that affects the way a memory access is performed in some way.

// There are different groups of decorators. Some have to do with memory ordering, others to do with,

// e.g. strength of references, strength of GC barriers, or whether compression should be applied or not.

// Some decorators are set at buildtime, such as whether primitives require GC barriers or not, others

// at callsites such as whether an access is in the heap or not, and others are resolved at runtime

// such as GC-specific barriers and encoding/decoding compressed oops.

// By pipelining handling of these decorators, the design of the Access API allows separation of concern

// over the different orthogonal concerns of decorators, while providing a powerful way of

// expressing these orthogonal semantic properties in a unified way.

// == OPERATIONS ==

// * load: Load a value from an address.

// * load_at: Load a value from an internal pointer relative to a base object.

// * store: Store a value at an address.

// * store_at: Store a value in an internal pointer relative to a base object.

// * atomic_cmpxchg: Atomically compare-and-swap a new value at an address if previous value matched the compared value.

// * atomic_cmpxchg_at: Atomically compare-and-swap a new value at an internal pointer address if previous value matched the compared value.

// * atomic_xchg: Atomically swap a new value at an address if previous value matched the compared value.

// * atomic_xchg_at: Atomically swap a new value at an internal pointer address if previous value matched the compared value.

// * arraycopy: Copy data from one heap array to another heap array.

// * clone: Clone the contents of an object to a newly allocated object.

// * resolve: Resolve a stable to-space invariant oop that is guaranteed not to relocate its payload until a subsequent thread transition.

typedef uint64_t DecoratorSet;

// == Internal Decorators - do not use ==

// * INTERNAL_EMPTY: This is the name for the empty decorator set (in absence of other decorators).

// * INTERNAL_CONVERT_COMPRESSED_OOPS: This is an oop access that will require converting an oop

//   to a narrowOop or vice versa, if UseCompressedOops is known to be set.

// * INTERNAL_VALUE_IS_OOP: Remember that the involved access is on oop rather than primitive.

const DecoratorSet INTERNAL_EMPTY                    = UCONST64(0);

const DecoratorSet INTERNAL_CONVERT_COMPRESSED_OOP   = UCONST64(1) << 1;

const DecoratorSet INTERNAL_VALUE_IS_OOP             = UCONST64(1) << 2;

// == Internal build-time Decorators ==

// * INTERNAL_BT_BARRIER_ON_PRIMITIVES: This is set in the barrierSetConfig.hpp file.

// * INTERNAL_BT_TO_SPACE_INVARIANT: This is set in the barrierSetConfig.hpp file iff

//   no GC is bundled in the build that is to-space invariant.

const DecoratorSet INTERNAL_BT_BARRIER_ON_PRIMITIVES = UCONST64(1) << 3;

const DecoratorSet INTERNAL_BT_TO_SPACE_INVARIANT    = UCONST64(1) << 4;

// == Internal run-time Decorators ==

// * INTERNAL_RT_USE_COMPRESSED_OOPS: This decorator will be set in runtime resolved

//   access backends iff UseCompressedOops is true.

const DecoratorSet INTERNAL_RT_USE_COMPRESSED_OOPS   = UCONST64(1) << 5;

const DecoratorSet INTERNAL_DECORATOR_MASK           = INTERNAL_CONVERT_COMPRESSED_OOP | INTERNAL_VALUE_IS_OOP |

                                                       INTERNAL_BT_BARRIER_ON_PRIMITIVES | INTERNAL_RT_USE_COMPRESSED_OOPS;

// == Memory Ordering Decorators ==

// The memory ordering decorators can be described in the following way:

// === Decorator Rules ===

// The different types of memory ordering guarantees have a strict order of strength.

// Explicitly specifying the stronger ordering implies that the guarantees of the weaker

// property holds too. The names come from the C++11 atomic operations, and typically

// have a JMM equivalent property.

// The equivalence may be viewed like this:

// MO_UNORDERED is equivalent to JMM plain.

// MO_VOLATILE has no equivalence in JMM, because it's a C++ thing.

// MO_RELAXED is equivalent to JMM opaque.

// MO_ACQUIRE is equivalent to JMM acquire.

// MO_RELEASE is equivalent to JMM release.

// MO_SEQ_CST is equivalent to JMM volatile.

//

// === Stores ===

//  * MO_UNORDERED (Default): No guarantees.

//    - The compiler and hardware are free to reorder aggressively. And they will.

//  * MO_VOLATILE: Volatile stores (in the C++ sense).

//    - The stores are not reordered by the compiler (but possibly the HW) w.r.t. other

//      volatile accesses in program order (but possibly non-volatile accesses).

//  * MO_RELAXED: Relaxed atomic stores.

//    - The stores are atomic.

//    - Guarantees from volatile stores hold.

//  * MO_RELEASE: Releasing stores.

//    - The releasing store will make its preceding memory accesses observable to memory accesses

//      subsequent to an acquiring load observing this releasing store.

//    - Guarantees from relaxed stores hold.

//  * MO_SEQ_CST: Sequentially consistent stores.

//    - The stores are observed in the same order by MO_SEQ_CST loads on other processors

//    - Preceding loads and stores in program order are not reordered with subsequent loads and stores in program order.

//    - Guarantees from releasing stores hold.

// === Loads ===

//  * MO_UNORDERED (Default): No guarantees

//    - The compiler and hardware are free to reorder aggressively. And they will.

//  * MO_VOLATILE: Volatile loads (in the C++ sense).

//    - The loads are not reordered by the compiler (but possibly the HW) w.r.t. other

//      volatile accesses in program order (but possibly non-volatile accesses).

//  * MO_RELAXED: Relaxed atomic loads.

//    - The stores are atomic.

//    - Guarantees from volatile loads hold.

//  * MO_ACQUIRE: Acquiring loads.

//    - An acquiring load will make subsequent memory accesses observe the memory accesses

//      preceding the releasing store that the acquiring load observed.

//    - Guarantees from relaxed loads hold.

//  * MO_SEQ_CST: Sequentially consistent loads.

//    - These loads observe MO_SEQ_CST stores in the same order on other processors

//    - Preceding loads and stores in program order are not reordered with subsequent loads and stores in program order.

//    - Guarantees from acquiring loads hold.

// === Atomic Cmpxchg ===

//  * MO_RELAXED: Atomic but relaxed cmpxchg.

//    - Guarantees from MO_RELAXED loads and MO_RELAXED stores hold unconditionally.

//  * MO_SEQ_CST: Sequentially consistent cmpxchg.

//    - Guarantees from MO_SEQ_CST loads and MO_SEQ_CST stores hold unconditionally.

// === Atomic Xchg ===

//  * MO_RELAXED: Atomic but relaxed atomic xchg.

//    - Guarantees from MO_RELAXED loads and MO_RELAXED stores hold.

//  * MO_SEQ_CST: Sequentially consistent xchg.

//    - Guarantees from MO_SEQ_CST loads and MO_SEQ_CST stores hold.

const DecoratorSet MO_UNORDERED      = UCONST64(1) << 6;

const DecoratorSet MO_VOLATILE       = UCONST64(1) << 7;

const DecoratorSet MO_RELAXED        = UCONST64(1) << 8;

const DecoratorSet MO_ACQUIRE        = UCONST64(1) << 9;

const DecoratorSet MO_RELEASE        = UCONST64(1) << 10;

const DecoratorSet MO_SEQ_CST        = UCONST64(1) << 11;

const DecoratorSet MO_DECORATOR_MASK = MO_UNORDERED | MO_VOLATILE | MO_RELAXED |

                                       MO_ACQUIRE | MO_RELEASE | MO_SEQ_CST;

// === Barrier Strength Decorators ===

// * AS_RAW: The access will translate into a raw memory access, hence ignoring all semantic concerns

//   except memory ordering and compressed oops. This will bypass runtime function pointer dispatching

//   in the pipeline and hardwire to raw accesses without going trough the GC access barriers.

//  - Accesses on oop* translate to raw memory accesses without runtime checks

//  - Accesses on narrowOop* translate to encoded/decoded memory accesses without runtime checks

//  - Accesses on HeapWord* translate to a runtime check choosing one of the above

//  - Accesses on other types translate to raw memory accesses without runtime checks

// * AS_DEST_NOT_INITIALIZED: This property can be important to e.g. SATB barriers by

//   marking that the previous value is uninitialized nonsense rather than a real value.

// * AS_NO_KEEPALIVE: The barrier is used only on oop references and will not keep any involved objects

//   alive, regardless of the type of reference being accessed. It will however perform the memory access

//   in a consistent way w.r.t. e.g. concurrent compaction, so that the right field is being accessed,

//   or maintain, e.g. intergenerational or interregional pointers if applicable. This should be used with

//   extreme caution in isolated scopes.

// * AS_NORMAL: The accesses will be resolved to an accessor on the BarrierSet class, giving the

//   responsibility of performing the access and what barriers to be performed to the GC. This is the default.

//   Note that primitive accesses will only be resolved on the barrier set if the appropriate build-time

//   decorator for enabling primitive barriers is enabled for the build.

const DecoratorSet AS_RAW                  = UCONST64(1) << 12;

const DecoratorSet AS_DEST_NOT_INITIALIZED = UCONST64(1) << 13;

const DecoratorSet AS_NO_KEEPALIVE         = UCONST64(1) << 14;

const DecoratorSet AS_NORMAL               = UCONST64(1) << 15;

const DecoratorSet AS_DECORATOR_MASK       = AS_RAW | AS_DEST_NOT_INITIALIZED |

                                             AS_NO_KEEPALIVE | AS_NORMAL;

// === Reference Strength Decorators ===

// These decorators only apply to accesses on oop-like types (oop/narrowOop).

// * ON_STRONG_OOP_REF: Memory access is performed on a strongly reachable reference.

// * ON_WEAK_OOP_REF: The memory access is performed on a weakly reachable reference.

// * ON_PHANTOM_OOP_REF: The memory access is performed on a phantomly reachable reference.

//   This is the same ring of strength as jweak and weak oops in the VM.

// * ON_UNKNOWN_OOP_REF: The memory access is performed on a reference of unknown strength.

//   This could for example come from the unsafe API.

// * Default (no explicit reference strength specified): ON_STRONG_OOP_REF

const DecoratorSet ON_STRONG_OOP_REF  = UCONST64(1) << 16;

const DecoratorSet ON_WEAK_OOP_REF    = UCONST64(1) << 17;

const DecoratorSet ON_PHANTOM_OOP_REF = UCONST64(1) << 18;

const DecoratorSet ON_UNKNOWN_OOP_REF = UCONST64(1) << 19;

const DecoratorSet ON_DECORATOR_MASK  = ON_STRONG_OOP_REF | ON_WEAK_OOP_REF |

                                        ON_PHANTOM_OOP_REF | ON_UNKNOWN_OOP_REF;

// === Access Location ===

// Accesses can take place in, e.g. the heap, old or young generation and different native roots.

// The location is important to the GC as it may imply different actions. The following decorators are used:

// * IN_HEAP: The access is performed in the heap. Many barriers such as card marking will

//   be omitted if this decorator is not set.

// * IN_HEAP_ARRAY: The access is performed on a heap allocated array. This is sometimes a special case

//   for some GCs, and implies that it is an IN_HEAP.

// * IN_ROOT: The access is performed in an off-heap data structure pointing into the Java heap.

// * IN_CONCURRENT_ROOT: The access is performed in an off-heap data structure pointing into the Java heap,

//   but is notably not scanned during safepoints. This is sometimes a special case for some GCs and

//   implies that it is also an IN_ROOT.

const DecoratorSet IN_HEAP            = UCONST64(1) << 20;

const DecoratorSet IN_HEAP_ARRAY      = UCONST64(1) << 21;

const DecoratorSet IN_ROOT            = UCONST64(1) << 22;

const DecoratorSet IN_CONCURRENT_ROOT = UCONST64(1) << 23;

const DecoratorSet IN_ARCHIVE_ROOT    = UCONST64(1) << 24;

const DecoratorSet IN_DECORATOR_MASK  = IN_HEAP | IN_HEAP_ARRAY |

                                        IN_ROOT | IN_CONCURRENT_ROOT |

                                        IN_ARCHIVE_ROOT;

// == Value Decorators ==

// * OOP_NOT_NULL: This property can make certain barriers faster such as compressing oops.

const DecoratorSet OOP_NOT_NULL       = UCONST64(1) << 25;

const DecoratorSet OOP_DECORATOR_MASK = OOP_NOT_NULL;

// == Arraycopy Decorators ==

// * ARRAYCOPY_CHECKCAST: This property means that the class of the objects in source

//   are not guaranteed to be subclasses of the class of the destination array. This requires

//   a check-cast barrier during the copying operation. If this is not set, it is assumed

//   that the array is covariant: (the source array type is-a destination array type)

// * ARRAYCOPY_DISJOINT: This property means that it is known that the two array ranges

//   are disjoint.

// * ARRAYCOPY_ARRAYOF: The copy is in the arrayof form.

// * ARRAYCOPY_ATOMIC: The accesses have to be atomic over the size of its elements.

// * ARRAYCOPY_ALIGNED: The accesses have to be aligned on a HeapWord.

const DecoratorSet ARRAYCOPY_CHECKCAST            = UCONST64(1) << 26;

const DecoratorSet ARRAYCOPY_DISJOINT             = UCONST64(1) << 27;

const DecoratorSet ARRAYCOPY_ARRAYOF              = UCONST64(1) << 28;

const DecoratorSet ARRAYCOPY_ATOMIC               = UCONST64(1) << 29;

const DecoratorSet ARRAYCOPY_ALIGNED              = UCONST64(1) << 30;

const DecoratorSet ARRAYCOPY_DECORATOR_MASK       = ARRAYCOPY_CHECKCAST | ARRAYCOPY_DISJOINT |

                                                    ARRAYCOPY_DISJOINT | ARRAYCOPY_ARRAYOF |

                                                    ARRAYCOPY_ATOMIC | ARRAYCOPY_ALIGNED;

// The HasDecorator trait can help at compile-time determining whether a decorator set

// has an intersection with a certain other decorator set

template <DecoratorSet decorators, DecoratorSet decorator>

struct HasDecorator: public IntegralConstant<bool, (decorators & decorator) != 0> {};

namespace AccessInternal {

  template <typename T>

  struct OopOrNarrowOopInternal: AllStatic {

    typedef oop type;

  };

  template <>

  struct OopOrNarrowOopInternal<narrowOop>: AllStatic {

    typedef narrowOop type;

  };

  // This metafunction returns a canonicalized oop/narrowOop type for a passed

  // in oop-like types passed in from oop_* overloads where the user has sworn

  // that the passed in values should be oop-like (e.g. oop, oopDesc*, arrayOop,

  // narrowOoop, instanceOopDesc*, and random other things).

  // In the oop_* overloads, it must hold that if the passed in type T is not

  // narrowOop, then it by contract has to be one of many oop-like types implicitly

  // convertible to oop, and hence returns oop as the canonical oop type.

  // If it turns out it was not, then the implicit conversion to oop will fail

  // to compile, as desired.

  template <typename T>

  struct OopOrNarrowOop: AllStatic {

    typedef typename OopOrNarrowOopInternal<typename Decay<T>::type>::type type;

  };

  inline void* field_addr(oop base, ptrdiff_t byte_offset) {

    return reinterpret_cast<void*>(reinterpret_cast<intptr_t>((void*)base) + byte_offset);

  }

  template <DecoratorSet decorators, typename T>

  void store_at(oop base, ptrdiff_t offset, T value);

  template <DecoratorSet decorators, typename T>

  T load_at(oop base, ptrdiff_t offset);

  template <DecoratorSet decorators, typename T>

  T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value);

  template <DecoratorSet decorators, typename T>

  T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset);

  template <DecoratorSet decorators, typename P, typename T>

  void store(P* addr, T value);

  template <DecoratorSet decorators, typename P, typename T>

  T load(P* addr);

  template <DecoratorSet decorators, typename P, typename T>

  T atomic_cmpxchg(T new_value, P* addr, T compare_value);

  template <DecoratorSet decorators, typename P, typename T>

  T atomic_xchg(T new_value, P* addr);

  template <DecoratorSet decorators, typename T>

  bool arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length);

  template <DecoratorSet decorators>

  void clone(oop src, oop dst, size_t size);

  template <DecoratorSet decorators>

  oop resolve(oop src);

  // Infer the type that should be returned from a load.

  template <typename P, DecoratorSet decorators>

  class LoadProxy: public StackObj {

  private:

    P *const _addr;

  public:

    LoadProxy(P* addr) : _addr(addr) {}

    template <typename T>

    inline operator T() {

      return load<decorators, P, T>(_addr);

    }

    inline operator P() {

      return load<decorators, P, P>(_addr);

    }

  };

  // Infer the type that should be returned from a load_at.

  template <DecoratorSet decorators>

  class LoadAtProxy: public StackObj {

  private:

    const oop _base;

    const ptrdiff_t _offset;

  public:

    LoadAtProxy(oop base, ptrdiff_t offset) : _base(base), _offset(offset) {}

    template <typename T>

    inline operator T() const {

      return load_at<decorators, T>(_base, _offset);

    }

  };

}

template <DecoratorSet decorators = INTERNAL_EMPTY>

class Access: public AllStatic {

  // This function asserts that if an access gets passed in a decorator outside

  // of the expected_decorators, then something is wrong. It additionally checks

  // the consistency of the decorators so that supposedly disjoint decorators are indeed

  // disjoint. For example, an access can not be both in heap and on root at the

  // same time.

  template <DecoratorSet expected_decorators>

  static void verify_decorators();

  template <DecoratorSet expected_mo_decorators>

  static void verify_primitive_decorators() {

    const DecoratorSet primitive_decorators = (AS_DECORATOR_MASK ^ AS_NO_KEEPALIVE ^ AS_DEST_NOT_INITIALIZED) |

                                              IN_HEAP | IN_HEAP_ARRAY;

    verify_decorators<expected_mo_decorators | primitive_decorators>();

  }

  template <DecoratorSet expected_mo_decorators>

  static void verify_oop_decorators() {

    const DecoratorSet oop_decorators = AS_DECORATOR_MASK | IN_DECORATOR_MASK |

                                        (ON_DECORATOR_MASK ^ ON_UNKNOWN_OOP_REF) | // no unknown oop refs outside of the heap

                                        OOP_DECORATOR_MASK;

    verify_decorators<expected_mo_decorators | oop_decorators>();

  }

  template <DecoratorSet expected_mo_decorators>

  static void verify_heap_oop_decorators() {

    const DecoratorSet heap_oop_decorators = AS_DECORATOR_MASK | ON_DECORATOR_MASK |

                                             OOP_DECORATOR_MASK | (IN_DECORATOR_MASK ^

                                                                   (IN_ROOT | IN_CONCURRENT_ROOT)); // no root accesses in the heap

    verify_decorators<expected_mo_decorators | heap_oop_decorators>();

  }

  static const DecoratorSet load_mo_decorators = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | MO_ACQUIRE | MO_SEQ_CST;

  static const DecoratorSet store_mo_decorators = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | MO_RELEASE | MO_SEQ_CST;

  static const DecoratorSet atomic_xchg_mo_decorators = MO_SEQ_CST;

  static const DecoratorSet atomic_cmpxchg_mo_decorators = MO_RELAXED | MO_SEQ_CST;

public:

  // Primitive heap accesses

  static inline AccessInternal::LoadAtProxy<decorators> load_at(oop base, ptrdiff_t offset) {

    verify_primitive_decorators<load_mo_decorators>();

    return AccessInternal::LoadAtProxy<decorators>(base, offset);

  }

  template <typename T>

  static inline void store_at(oop base, ptrdiff_t offset, T value) {

    verify_primitive_decorators<store_mo_decorators>();

    AccessInternal::store_at<decorators>(base, offset, value);

  }

  template <typename T>

  static inline T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {

    verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();

    return AccessInternal::atomic_cmpxchg_at<decorators>(new_value, base, offset, compare_value);

  }

  template <typename T>

  static inline T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {

    verify_primitive_decorators<atomic_xchg_mo_decorators>();

    return AccessInternal::atomic_xchg_at<decorators>(new_value, base, offset);

  }

  template <typename T>

    verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP |

                      AS_DECORATOR_MASK>();

  }

  // Oop heap accesses

  static inline AccessInternal::LoadAtProxy<decorators | INTERNAL_VALUE_IS_OOP> oop_load_at(oop base, ptrdiff_t offset) {

    verify_heap_oop_decorators<load_mo_decorators>();

    return AccessInternal::LoadAtProxy<decorators | INTERNAL_VALUE_IS_OOP>(base, offset);

  }

  template <typename T>

  static inline void oop_store_at(oop base, ptrdiff_t offset, T value) {

    verify_heap_oop_decorators<store_mo_decorators>();

    typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;

    OopType oop_value = value;

    AccessInternal::store_at<decorators | INTERNAL_VALUE_IS_OOP>(base, offset, oop_value);

  }

  template <typename T>

  static inline T oop_atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {

    verify_heap_oop_decorators<atomic_cmpxchg_mo_decorators>();

    typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;

    OopType new_oop_value = new_value;

    OopType compare_oop_value = compare_value;

    return AccessInternal::atomic_cmpxchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset, compare_oop_value);

  }

  template <typename T>

  static inline T oop_atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {

    verify_heap_oop_decorators<atomic_xchg_mo_decorators>();

    typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;

    OopType new_oop_value = new_value;

    return AccessInternal::atomic_xchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset);

  }

  template <typename T>

  static inline bool oop_arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length) {

    verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP | AS_DECORATOR_MASK>();

    return AccessInternal::arraycopy<decorators | INTERNAL_VALUE_IS_OOP>(src_obj, dst_obj, src, dst, length);

  }

  // Clone an object from src to dst

  static inline void clone(oop src, oop dst, size_t size) {

    verify_decorators<IN_HEAP>();

    AccessInternal::clone<decorators>(src, dst, size);

  }

  // Primitive accesses

  template <typename P>

  static inline P load(P* addr) {

    verify_primitive_decorators<load_mo_decorators>();

    return AccessInternal::load<decorators, P, P>(addr);

  }

  template <typename P, typename T>

  static inline void store(P* addr, T value) {

    verify_primitive_decorators<store_mo_decorators>();

    AccessInternal::store<decorators>(addr, value);

  }

  template <typename P, typename T>

  static inline T atomic_cmpxchg(T new_value, P* addr, T compare_value) {

    verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();

    return AccessInternal::atomic_cmpxchg<decorators>(new_value, addr, compare_value);

  }

  template <typename P, typename T>

  static inline T atomic_xchg(T new_value, P* addr) {

    verify_primitive_decorators<atomic_xchg_mo_decorators>();

    return AccessInternal::atomic_xchg<decorators>(new_value, addr);

  }

  // Oop accesses

  template <typename P>

  static inline AccessInternal::LoadProxy<P, decorators | INTERNAL_VALUE_IS_OOP> oop_load(P* addr) {

    verify_oop_decorators<load_mo_decorators>();

    return AccessInternal::LoadProxy<P, decorators | INTERNAL_VALUE_IS_OOP>(addr);

  }

  template <typename P, typename T>

  static inline void oop_store(P* addr, T value) {

    verify_oop_decorators<store_mo_decorators>();

    typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;

    OopType oop_value = value;

    AccessInternal::store<decorators | INTERNAL_VALUE_IS_OOP>(addr, oop_value);

  }

  template <typename P, typename T>

  static inline T oop_atomic_cmpxchg(T new_value, P* addr, T compare_value) {

    verify_oop_decorators<atomic_cmpxchg_mo_decorators>();

    typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;

    OopType new_oop_value = new_value;

    OopType compare_oop_value = compare_value;

    return AccessInternal::atomic_cmpxchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr, compare_oop_value);

  }

  template <typename P, typename T>

  static inline T oop_atomic_xchg(T new_value, P* addr) {

    verify_oop_decorators<atomic_xchg_mo_decorators>();

    typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;

    OopType new_oop_value = new_value;

    return AccessInternal::atomic_xchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr);

  }

  static oop resolve(oop obj) {

    verify_decorators<INTERNAL_EMPTY>();

    return AccessInternal::resolve<decorators>(obj);

  }

};

// Helper for performing raw accesses (knows only of memory ordering

// atomicity decorators as well as compressed oops)

template <DecoratorSet decorators = INTERNAL_EMPTY>

class RawAccess: public Access<AS_RAW | decorators> {};

// Helper for performing normal accesses on the heap. These accesses