src/hotspot/share/oops/access.hpp
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     1 /*
       
     2  * Copyright (c) 2017, 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
       
    21  * questions.
       
    22  *
       
    23  */
       
    24 
       
    25 #ifndef SHARE_VM_RUNTIME_ACCESS_HPP
       
    26 #define SHARE_VM_RUNTIME_ACCESS_HPP
       
    27 
       
    28 #include "memory/allocation.hpp"
       
    29 #include "metaprogramming/decay.hpp"
       
    30 #include "metaprogramming/integralConstant.hpp"
       
    31 #include "oops/oopsHierarchy.hpp"
       
    32 #include "utilities/debug.hpp"
       
    33 #include "utilities/globalDefinitions.hpp"
       
    34 
       
    35 // = GENERAL =
       
    36 // Access is an API for performing accesses with declarative semantics. Each access can have a number of "decorators".
       
    37 // A decorator is an attribute or property that affects the way a memory access is performed in some way.
       
    38 // There are different groups of decorators. Some have to do with memory ordering, others to do with,
       
    39 // e.g. strength of references, strength of GC barriers, or whether compression should be applied or not.
       
    40 // Some decorators are set at buildtime, such as whether primitives require GC barriers or not, others
       
    41 // at callsites such as whether an access is in the heap or not, and others are resolved at runtime
       
    42 // such as GC-specific barriers and encoding/decoding compressed oops.
       
    43 // By pipelining handling of these decorators, the design of the Access API allows separation of concern
       
    44 // over the different orthogonal concerns of decorators, while providing a powerful way of
       
    45 // expressing these orthogonal semantic properties in a unified way.
       
    46 
       
    47 // == OPERATIONS ==
       
    48 // * load: Load a value from an address.
       
    49 // * load_at: Load a value from an internal pointer relative to a base object.
       
    50 // * store: Store a value at an address.
       
    51 // * store_at: Store a value in an internal pointer relative to a base object.
       
    52 // * atomic_cmpxchg: Atomically compare-and-swap a new value at an address if previous value matched the compared value.
       
    53 // * atomic_cmpxchg_at: Atomically compare-and-swap a new value at an internal pointer address if previous value matched the compared value.
       
    54 // * atomic_xchg: Atomically swap a new value at an address if previous value matched the compared value.
       
    55 // * atomic_xchg_at: Atomically swap a new value at an internal pointer address if previous value matched the compared value.
       
    56 // * arraycopy: Copy data from one heap array to another heap array.
       
    57 // * clone: Clone the contents of an object to a newly allocated object.
       
    58 
       
    59 typedef uint64_t DecoratorSet;
       
    60 
       
    61 // == Internal Decorators - do not use ==
       
    62 // * INTERNAL_EMPTY: This is the name for the empty decorator set (in absence of other decorators).
       
    63 // * INTERNAL_CONVERT_COMPRESSED_OOPS: This is an oop access that will require converting an oop
       
    64 //   to a narrowOop or vice versa, if UseCompressedOops is known to be set.
       
    65 // * INTERNAL_VALUE_IS_OOP: Remember that the involved access is on oop rather than primitive.
       
    66 const DecoratorSet INTERNAL_EMPTY                    = UCONST64(0);
       
    67 const DecoratorSet INTERNAL_CONVERT_COMPRESSED_OOP   = UCONST64(1) << 1;
       
    68 const DecoratorSet INTERNAL_VALUE_IS_OOP             = UCONST64(1) << 2;
       
    69 
       
    70 // == Internal build-time Decorators ==
       
    71 // * INTERNAL_BT_BARRIER_ON_PRIMITIVES: This is set in the barrierSetConfig.hpp file.
       
    72 const DecoratorSet INTERNAL_BT_BARRIER_ON_PRIMITIVES = UCONST64(1) << 3;
       
    73 
       
    74 // == Internal run-time Decorators ==
       
    75 // * INTERNAL_RT_USE_COMPRESSED_OOPS: This decorator will be set in runtime resolved
       
    76 //   access backends iff UseCompressedOops is true.
       
    77 const DecoratorSet INTERNAL_RT_USE_COMPRESSED_OOPS   = UCONST64(1) << 4;
       
    78 
       
    79 const DecoratorSet INTERNAL_DECORATOR_MASK           = INTERNAL_CONVERT_COMPRESSED_OOP | INTERNAL_VALUE_IS_OOP |
       
    80                                                        INTERNAL_BT_BARRIER_ON_PRIMITIVES | INTERNAL_RT_USE_COMPRESSED_OOPS;
       
    81 
       
    82 // == Memory Ordering Decorators ==
       
    83 // The memory ordering decorators can be described in the following way:
       
    84 // === Decorator Rules ===
       
    85 // The different types of memory ordering guarantees have a strict order of strength.
       
    86 // Explicitly specifying the stronger ordering implies that the guarantees of the weaker
       
    87 // property holds too. The names come from the C++11 atomic operations, and typically
       
    88 // have a JMM equivalent property.
       
    89 // The equivalence may be viewed like this:
       
    90 // MO_UNORDERED is equivalent to JMM plain.
       
    91 // MO_VOLATILE has no equivalence in JMM, because it's a C++ thing.
       
    92 // MO_RELAXED is equivalent to JMM opaque.
       
    93 // MO_ACQUIRE is equivalent to JMM acquire.
       
    94 // MO_RELEASE is equivalent to JMM release.
       
    95 // MO_SEQ_CST is equivalent to JMM volatile.
       
    96 //
       
    97 // === Stores ===
       
    98 //  * MO_UNORDERED (Default): No guarantees.
       
    99 //    - The compiler and hardware are free to reorder aggressively. And they will.
       
   100 //  * MO_VOLATILE: Volatile stores (in the C++ sense).
       
   101 //    - The stores are not reordered by the compiler (but possibly the HW) w.r.t. other
       
   102 //      volatile accesses in program order (but possibly non-volatile accesses).
       
   103 //  * MO_RELAXED: Relaxed atomic stores.
       
   104 //    - The stores are atomic.
       
   105 //    - Guarantees from volatile stores hold.
       
   106 //  * MO_RELEASE: Releasing stores.
       
   107 //    - The releasing store will make its preceding memory accesses observable to memory accesses
       
   108 //      subsequent to an acquiring load observing this releasing store.
       
   109 //    - Guarantees from relaxed stores hold.
       
   110 //  * MO_SEQ_CST: Sequentially consistent stores.
       
   111 //    - The stores are observed in the same order by MO_SEQ_CST loads on other processors
       
   112 //    - Preceding loads and stores in program order are not reordered with subsequent loads and stores in program order.
       
   113 //    - Guarantees from releasing stores hold.
       
   114 // === Loads ===
       
   115 //  * MO_UNORDERED (Default): No guarantees
       
   116 //    - The compiler and hardware are free to reorder aggressively. And they will.
       
   117 //  * MO_VOLATILE: Volatile loads (in the C++ sense).
       
   118 //    - The loads are not reordered by the compiler (but possibly the HW) w.r.t. other
       
   119 //      volatile accesses in program order (but possibly non-volatile accesses).
       
   120 //  * MO_RELAXED: Relaxed atomic loads.
       
   121 //    - The stores are atomic.
       
   122 //    - Guarantees from volatile loads hold.
       
   123 //  * MO_ACQUIRE: Acquiring loads.
       
   124 //    - An acquiring load will make subsequent memory accesses observe the memory accesses
       
   125 //      preceding the releasing store that the acquiring load observed.
       
   126 //    - Guarantees from relaxed loads hold.
       
   127 //  * MO_SEQ_CST: Sequentially consistent loads.
       
   128 //    - These loads observe MO_SEQ_CST stores in the same order on other processors
       
   129 //    - Preceding loads and stores in program order are not reordered with subsequent loads and stores in program order.
       
   130 //    - Guarantees from acquiring loads hold.
       
   131 // === Atomic Cmpxchg ===
       
   132 //  * MO_RELAXED: Atomic but relaxed cmpxchg.
       
   133 //    - Guarantees from MO_RELAXED loads and MO_RELAXED stores hold unconditionally.
       
   134 //  * MO_SEQ_CST: Sequentially consistent cmpxchg.
       
   135 //    - Guarantees from MO_SEQ_CST loads and MO_SEQ_CST stores hold unconditionally.
       
   136 // === Atomic Xchg ===
       
   137 //  * MO_RELAXED: Atomic but relaxed atomic xchg.
       
   138 //    - Guarantees from MO_RELAXED loads and MO_RELAXED stores hold.
       
   139 //  * MO_SEQ_CST: Sequentially consistent xchg.
       
   140 //    - Guarantees from MO_SEQ_CST loads and MO_SEQ_CST stores hold.
       
   141 const DecoratorSet MO_UNORDERED      = UCONST64(1) << 5;
       
   142 const DecoratorSet MO_VOLATILE       = UCONST64(1) << 6;
       
   143 const DecoratorSet MO_RELAXED        = UCONST64(1) << 7;
       
   144 const DecoratorSet MO_ACQUIRE        = UCONST64(1) << 8;
       
   145 const DecoratorSet MO_RELEASE        = UCONST64(1) << 9;
       
   146 const DecoratorSet MO_SEQ_CST        = UCONST64(1) << 10;
       
   147 const DecoratorSet MO_DECORATOR_MASK = MO_UNORDERED | MO_VOLATILE | MO_RELAXED |
       
   148                                        MO_ACQUIRE | MO_RELEASE | MO_SEQ_CST;
       
   149 
       
   150 // === Barrier Strength Decorators ===
       
   151 // * AS_RAW: The access will translate into a raw memory access, hence ignoring all semantic concerns
       
   152 //   except memory ordering and compressed oops. This will bypass runtime function pointer dispatching
       
   153 //   in the pipeline and hardwire to raw accesses without going trough the GC access barriers.
       
   154 //  - Accesses on oop* translate to raw memory accesses without runtime checks
       
   155 //  - Accesses on narrowOop* translate to encoded/decoded memory accesses without runtime checks
       
   156 //  - Accesses on HeapWord* translate to a runtime check choosing one of the above
       
   157 //  - Accesses on other types translate to raw memory accesses without runtime checks
       
   158 // * AS_NO_KEEPALIVE: The barrier is used only on oop references and will not keep any involved objects
       
   159 //   alive, regardless of the type of reference being accessed. It will however perform the memory access
       
   160 //   in a consistent way w.r.t. e.g. concurrent compaction, so that the right field is being accessed,
       
   161 //   or maintain, e.g. intergenerational or interregional pointers if applicable. This should be used with
       
   162 //   extreme caution in isolated scopes.
       
   163 // * AS_NORMAL: The accesses will be resolved to an accessor on the BarrierSet class, giving the
       
   164 //   responsibility of performing the access and what barriers to be performed to the GC. This is the default.
       
   165 //   Note that primitive accesses will only be resolved on the barrier set if the appropriate build-time
       
   166 //   decorator for enabling primitive barriers is enabled for the build.
       
   167 const DecoratorSet AS_RAW            = UCONST64(1) << 11;
       
   168 const DecoratorSet AS_NO_KEEPALIVE   = UCONST64(1) << 12;
       
   169 const DecoratorSet AS_NORMAL         = UCONST64(1) << 13;
       
   170 const DecoratorSet AS_DECORATOR_MASK = AS_RAW | AS_NO_KEEPALIVE | AS_NORMAL;
       
   171 
       
   172 // === Reference Strength Decorators ===
       
   173 // These decorators only apply to accesses on oop-like types (oop/narrowOop).
       
   174 // * ON_STRONG_OOP_REF: Memory access is performed on a strongly reachable reference.
       
   175 // * ON_WEAK_OOP_REF: The memory access is performed on a weakly reachable reference.
       
   176 // * ON_PHANTOM_OOP_REF: The memory access is performed on a phantomly reachable reference.
       
   177 //   This is the same ring of strength as jweak and weak oops in the VM.
       
   178 // * ON_UNKNOWN_OOP_REF: The memory access is performed on a reference of unknown strength.
       
   179 //   This could for example come from the unsafe API.
       
   180 // * Default (no explicit reference strength specified): ON_STRONG_OOP_REF
       
   181 const DecoratorSet ON_STRONG_OOP_REF  = UCONST64(1) << 14;
       
   182 const DecoratorSet ON_WEAK_OOP_REF    = UCONST64(1) << 15;
       
   183 const DecoratorSet ON_PHANTOM_OOP_REF = UCONST64(1) << 16;
       
   184 const DecoratorSet ON_UNKNOWN_OOP_REF = UCONST64(1) << 17;
       
   185 const DecoratorSet ON_DECORATOR_MASK  = ON_STRONG_OOP_REF | ON_WEAK_OOP_REF |
       
   186                                         ON_PHANTOM_OOP_REF | ON_UNKNOWN_OOP_REF;
       
   187 
       
   188 // === Access Location ===
       
   189 // Accesses can take place in, e.g. the heap, old or young generation and different native roots.
       
   190 // The location is important to the GC as it may imply different actions. The following decorators are used:
       
   191 // * IN_HEAP: The access is performed in the heap. Many barriers such as card marking will
       
   192 //   be omitted if this decorator is not set.
       
   193 // * IN_HEAP_ARRAY: The access is performed on a heap allocated array. This is sometimes a special case
       
   194 //   for some GCs, and implies that it is an IN_HEAP.
       
   195 // * IN_ROOT: The access is performed in an off-heap data structure pointing into the Java heap.
       
   196 // * IN_CONCURRENT_ROOT: The access is performed in an off-heap data structure pointing into the Java heap,
       
   197 //   but is notably not scanned during safepoints. This is sometimes a special case for some GCs and
       
   198 //   implies that it is also an IN_ROOT.
       
   199 const DecoratorSet IN_HEAP            = UCONST64(1) << 18;
       
   200 const DecoratorSet IN_HEAP_ARRAY      = UCONST64(1) << 19;
       
   201 const DecoratorSet IN_ROOT            = UCONST64(1) << 20;
       
   202 const DecoratorSet IN_CONCURRENT_ROOT = UCONST64(1) << 21;
       
   203 const DecoratorSet IN_DECORATOR_MASK  = IN_HEAP | IN_HEAP_ARRAY |
       
   204                                         IN_ROOT | IN_CONCURRENT_ROOT;
       
   205 
       
   206 // == Value Decorators ==
       
   207 // * OOP_NOT_NULL: This property can make certain barriers faster such as compressing oops.
       
   208 const DecoratorSet OOP_NOT_NULL       = UCONST64(1) << 22;
       
   209 const DecoratorSet OOP_DECORATOR_MASK = OOP_NOT_NULL;
       
   210 
       
   211 // == Arraycopy Decorators ==
       
   212 // * ARRAYCOPY_DEST_NOT_INITIALIZED: This property can be important to e.g. SATB barriers by
       
   213 //   marking that the previous value uninitialized nonsense rather than a real value.
       
   214 // * ARRAYCOPY_CHECKCAST: This property means that the class of the objects in source
       
   215 //   are not guaranteed to be subclasses of the class of the destination array. This requires
       
   216 //   a check-cast barrier during the copying operation. If this is not set, it is assumed
       
   217 //   that the array is covariant: (the source array type is-a destination array type)
       
   218 // * ARRAYCOPY_DISJOINT: This property means that it is known that the two array ranges
       
   219 //   are disjoint.
       
   220 // * ARRAYCOPY_ARRAYOF: The copy is in the arrayof form.
       
   221 // * ARRAYCOPY_ATOMIC: The accesses have to be atomic over the size of its elements.
       
   222 // * ARRAYCOPY_ALIGNED: The accesses have to be aligned on a HeapWord.
       
   223 const DecoratorSet ARRAYCOPY_DEST_NOT_INITIALIZED = UCONST64(1) << 24;
       
   224 const DecoratorSet ARRAYCOPY_CHECKCAST            = UCONST64(1) << 25;
       
   225 const DecoratorSet ARRAYCOPY_DISJOINT             = UCONST64(1) << 26;
       
   226 const DecoratorSet ARRAYCOPY_ARRAYOF              = UCONST64(1) << 27;
       
   227 const DecoratorSet ARRAYCOPY_ATOMIC               = UCONST64(1) << 28;
       
   228 const DecoratorSet ARRAYCOPY_ALIGNED              = UCONST64(1) << 29;
       
   229 const DecoratorSet ARRAYCOPY_DECORATOR_MASK       = ARRAYCOPY_DEST_NOT_INITIALIZED |
       
   230                                                     ARRAYCOPY_CHECKCAST | ARRAYCOPY_DISJOINT |
       
   231                                                     ARRAYCOPY_DISJOINT | ARRAYCOPY_ARRAYOF |
       
   232                                                     ARRAYCOPY_ATOMIC | ARRAYCOPY_ALIGNED;
       
   233 
       
   234 // The HasDecorator trait can help at compile-time determining whether a decorator set
       
   235 // has an intersection with a certain other decorator set
       
   236 template <DecoratorSet decorators, DecoratorSet decorator>
       
   237 struct HasDecorator: public IntegralConstant<bool, (decorators & decorator) != 0> {};
       
   238 
       
   239 namespace AccessInternal {
       
   240   template <typename T>
       
   241   struct OopOrNarrowOopInternal: AllStatic {
       
   242     typedef oop type;
       
   243   };
       
   244 
       
   245   template <>
       
   246   struct OopOrNarrowOopInternal<narrowOop>: AllStatic {
       
   247     typedef narrowOop type;
       
   248   };
       
   249 
       
   250   // This metafunction returns a canonicalized oop/narrowOop type for a passed
       
   251   // in oop-like types passed in from oop_* overloads where the user has sworn
       
   252   // that the passed in values should be oop-like (e.g. oop, oopDesc*, arrayOop,
       
   253   // narrowOoop, instanceOopDesc*, and random other things).
       
   254   // In the oop_* overloads, it must hold that if the passed in type T is not
       
   255   // narrowOop, then it by contract has to be one of many oop-like types implicitly
       
   256   // convertible to oop, and hence returns oop as the canonical oop type.
       
   257   // If it turns out it was not, then the implicit conversion to oop will fail
       
   258   // to compile, as desired.
       
   259   template <typename T>
       
   260   struct OopOrNarrowOop: AllStatic {
       
   261     typedef typename OopOrNarrowOopInternal<typename Decay<T>::type>::type type;
       
   262   };
       
   263 
       
   264   inline void* field_addr(oop base, ptrdiff_t byte_offset) {
       
   265     return reinterpret_cast<void*>(reinterpret_cast<intptr_t>((void*)base) + byte_offset);
       
   266   }
       
   267 
       
   268   template <DecoratorSet decorators, typename T>
       
   269   void store_at(oop base, ptrdiff_t offset, T value);
       
   270 
       
   271   template <DecoratorSet decorators, typename T>
       
   272   T load_at(oop base, ptrdiff_t offset);
       
   273 
       
   274   template <DecoratorSet decorators, typename T>
       
   275   T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value);
       
   276 
       
   277   template <DecoratorSet decorators, typename T>
       
   278   T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset);
       
   279 
       
   280   template <DecoratorSet decorators, typename P, typename T>
       
   281   void store(P* addr, T value);
       
   282 
       
   283   template <DecoratorSet decorators, typename P, typename T>
       
   284   T load(P* addr);
       
   285 
       
   286   template <DecoratorSet decorators, typename P, typename T>
       
   287   T atomic_cmpxchg(T new_value, P* addr, T compare_value);
       
   288 
       
   289   template <DecoratorSet decorators, typename P, typename T>
       
   290   T atomic_xchg(T new_value, P* addr);
       
   291 
       
   292   template <DecoratorSet decorators, typename T>
       
   293   bool arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length);
       
   294 
       
   295   template <DecoratorSet decorators>
       
   296   void clone(oop src, oop dst, size_t size);
       
   297 
       
   298   // Infer the type that should be returned from a load.
       
   299   template <typename P, DecoratorSet decorators>
       
   300   class LoadProxy: public StackObj {
       
   301   private:
       
   302     P *const _addr;
       
   303   public:
       
   304     LoadProxy(P* addr) : _addr(addr) {}
       
   305 
       
   306     template <typename T>
       
   307     inline operator T() {
       
   308       return load<decorators, P, T>(_addr);
       
   309     }
       
   310 
       
   311     inline operator P() {
       
   312       return load<decorators, P, P>(_addr);
       
   313     }
       
   314   };
       
   315 
       
   316   // Infer the type that should be returned from a load_at.
       
   317   template <DecoratorSet decorators>
       
   318   class LoadAtProxy: public StackObj {
       
   319   private:
       
   320     const oop _base;
       
   321     const ptrdiff_t _offset;
       
   322   public:
       
   323     LoadAtProxy(oop base, ptrdiff_t offset) : _base(base), _offset(offset) {}
       
   324 
       
   325     template <typename T>
       
   326     inline operator T() const {
       
   327       return load_at<decorators, T>(_base, _offset);
       
   328     }
       
   329   };
       
   330 }
       
   331 
       
   332 template <DecoratorSet decorators = INTERNAL_EMPTY>
       
   333 class Access: public AllStatic {
       
   334   // This function asserts that if an access gets passed in a decorator outside
       
   335   // of the expected_decorators, then something is wrong. It additionally checks
       
   336   // the consistency of the decorators so that supposedly disjoint decorators are indeed
       
   337   // disjoint. For example, an access can not be both in heap and on root at the
       
   338   // same time.
       
   339   template <DecoratorSet expected_decorators>
       
   340   static void verify_decorators();
       
   341 
       
   342   template <DecoratorSet expected_mo_decorators>
       
   343   static void verify_primitive_decorators() {
       
   344     const DecoratorSet primitive_decorators = (AS_DECORATOR_MASK ^ AS_NO_KEEPALIVE) | IN_HEAP |
       
   345                                                IN_HEAP_ARRAY | MO_DECORATOR_MASK;
       
   346     verify_decorators<expected_mo_decorators | primitive_decorators>();
       
   347   }
       
   348 
       
   349   template <DecoratorSet expected_mo_decorators>
       
   350   static void verify_oop_decorators() {
       
   351     const DecoratorSet oop_decorators = AS_DECORATOR_MASK | IN_DECORATOR_MASK |
       
   352                                         (ON_DECORATOR_MASK ^ ON_UNKNOWN_OOP_REF) | // no unknown oop refs outside of the heap
       
   353                                         OOP_DECORATOR_MASK | MO_DECORATOR_MASK;
       
   354     verify_decorators<expected_mo_decorators | oop_decorators>();
       
   355   }
       
   356 
       
   357   template <DecoratorSet expected_mo_decorators>
       
   358   static void verify_heap_oop_decorators() {
       
   359     const DecoratorSet heap_oop_decorators = AS_DECORATOR_MASK | ON_DECORATOR_MASK |
       
   360                                              OOP_DECORATOR_MASK | (IN_DECORATOR_MASK ^
       
   361                                                                   (IN_ROOT ^ IN_CONCURRENT_ROOT)) | // no root accesses in the heap
       
   362                                              MO_DECORATOR_MASK;
       
   363     verify_decorators<expected_mo_decorators | heap_oop_decorators>();
       
   364   }
       
   365 
       
   366   static const DecoratorSet load_mo_decorators = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | MO_ACQUIRE | MO_SEQ_CST;
       
   367   static const DecoratorSet store_mo_decorators = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | MO_RELEASE | MO_SEQ_CST;
       
   368   static const DecoratorSet atomic_xchg_mo_decorators = MO_SEQ_CST;
       
   369   static const DecoratorSet atomic_cmpxchg_mo_decorators = MO_RELAXED | MO_SEQ_CST;
       
   370 
       
   371 public:
       
   372   // Primitive heap accesses
       
   373   static inline AccessInternal::LoadAtProxy<decorators> load_at(oop base, ptrdiff_t offset) {
       
   374     verify_primitive_decorators<load_mo_decorators>();
       
   375     return AccessInternal::LoadAtProxy<decorators>(base, offset);
       
   376   }
       
   377 
       
   378   template <typename T>
       
   379   static inline void store_at(oop base, ptrdiff_t offset, T value) {
       
   380     verify_primitive_decorators<store_mo_decorators>();
       
   381     AccessInternal::store_at<decorators>(base, offset, value);
       
   382   }
       
   383 
       
   384   template <typename T>
       
   385   static inline T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {
       
   386     verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();
       
   387     return AccessInternal::atomic_cmpxchg_at<decorators>(new_value, base, offset, compare_value);
       
   388   }
       
   389 
       
   390   template <typename T>
       
   391   static inline T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {
       
   392     verify_primitive_decorators<atomic_xchg_mo_decorators>();
       
   393     return AccessInternal::atomic_xchg_at<decorators>(new_value, base, offset);
       
   394   }
       
   395 
       
   396   template <typename T>
       
   397   static inline bool arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length) {
       
   398     verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP |
       
   399                       AS_DECORATOR_MASK>();
       
   400     return AccessInternal::arraycopy<decorators>(src_obj, dst_obj, src, dst, length);
       
   401   }
       
   402 
       
   403   // Oop heap accesses
       
   404   static inline AccessInternal::LoadAtProxy<decorators | INTERNAL_VALUE_IS_OOP> oop_load_at(oop base, ptrdiff_t offset) {
       
   405     verify_heap_oop_decorators<load_mo_decorators>();
       
   406     return AccessInternal::LoadAtProxy<decorators | INTERNAL_VALUE_IS_OOP>(base, offset);
       
   407   }
       
   408 
       
   409   template <typename T>
       
   410   static inline void oop_store_at(oop base, ptrdiff_t offset, T value) {
       
   411     verify_heap_oop_decorators<store_mo_decorators>();
       
   412     typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
       
   413     OopType oop_value = value;
       
   414     AccessInternal::store_at<decorators | INTERNAL_VALUE_IS_OOP>(base, offset, oop_value);
       
   415   }
       
   416 
       
   417   template <typename T>
       
   418   static inline T oop_atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value) {
       
   419     verify_heap_oop_decorators<atomic_cmpxchg_mo_decorators>();
       
   420     typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
       
   421     OopType new_oop_value = new_value;
       
   422     OopType compare_oop_value = compare_value;
       
   423     return AccessInternal::atomic_cmpxchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset, compare_oop_value);
       
   424   }
       
   425 
       
   426   template <typename T>
       
   427   static inline T oop_atomic_xchg_at(T new_value, oop base, ptrdiff_t offset) {
       
   428     verify_heap_oop_decorators<atomic_xchg_mo_decorators>();
       
   429     typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
       
   430     OopType new_oop_value = new_value;
       
   431     return AccessInternal::atomic_xchg_at<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, base, offset);
       
   432   }
       
   433 
       
   434   template <typename T>
       
   435   static inline bool oop_arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length) {
       
   436     verify_decorators<ARRAYCOPY_DECORATOR_MASK | IN_HEAP | AS_DECORATOR_MASK>();
       
   437     return AccessInternal::arraycopy<decorators | INTERNAL_VALUE_IS_OOP>(src_obj, dst_obj, src, dst, length);
       
   438   }
       
   439 
       
   440   // Clone an object from src to dst
       
   441   static inline void clone(oop src, oop dst, size_t size) {
       
   442     verify_decorators<IN_HEAP>();
       
   443     AccessInternal::clone<decorators>(src, dst, size);
       
   444   }
       
   445 
       
   446   // Primitive accesses
       
   447   template <typename P>
       
   448   static inline P load(P* addr) {
       
   449     verify_primitive_decorators<load_mo_decorators>();
       
   450     return AccessInternal::load<decorators, P, P>(addr);
       
   451   }
       
   452 
       
   453   template <typename P, typename T>
       
   454   static inline void store(P* addr, T value) {
       
   455     verify_primitive_decorators<store_mo_decorators>();
       
   456     AccessInternal::store<decorators>(addr, value);
       
   457   }
       
   458 
       
   459   template <typename P, typename T>
       
   460   static inline T atomic_cmpxchg(T new_value, P* addr, T compare_value) {
       
   461     verify_primitive_decorators<atomic_cmpxchg_mo_decorators>();
       
   462     return AccessInternal::atomic_cmpxchg<decorators>(new_value, addr, compare_value);
       
   463   }
       
   464 
       
   465   template <typename P, typename T>
       
   466   static inline T atomic_xchg(T new_value, P* addr) {
       
   467     verify_primitive_decorators<atomic_xchg_mo_decorators>();
       
   468     return AccessInternal::atomic_xchg<decorators>(new_value, addr);
       
   469   }
       
   470 
       
   471   // Oop accesses
       
   472   template <typename P>
       
   473   static inline AccessInternal::LoadProxy<P, decorators | INTERNAL_VALUE_IS_OOP> oop_load(P* addr) {
       
   474     verify_oop_decorators<load_mo_decorators>();
       
   475     return AccessInternal::LoadProxy<P, decorators | INTERNAL_VALUE_IS_OOP>(addr);
       
   476   }
       
   477 
       
   478   template <typename P, typename T>
       
   479   static inline void oop_store(P* addr, T value) {
       
   480     verify_oop_decorators<store_mo_decorators>();
       
   481     typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
       
   482     OopType oop_value = value;
       
   483     AccessInternal::store<decorators | INTERNAL_VALUE_IS_OOP>(addr, oop_value);
       
   484   }
       
   485 
       
   486   template <typename P, typename T>
       
   487   static inline T oop_atomic_cmpxchg(T new_value, P* addr, T compare_value) {
       
   488     verify_oop_decorators<atomic_cmpxchg_mo_decorators>();
       
   489     typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
       
   490     OopType new_oop_value = new_value;
       
   491     OopType compare_oop_value = compare_value;
       
   492     return AccessInternal::atomic_cmpxchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr, compare_oop_value);
       
   493   }
       
   494 
       
   495   template <typename P, typename T>
       
   496   static inline T oop_atomic_xchg(T new_value, P* addr) {
       
   497     verify_oop_decorators<atomic_xchg_mo_decorators>();
       
   498     typedef typename AccessInternal::OopOrNarrowOop<T>::type OopType;
       
   499     OopType new_oop_value = new_value;
       
   500     return AccessInternal::atomic_xchg<decorators | INTERNAL_VALUE_IS_OOP>(new_oop_value, addr);
       
   501   }
       
   502 };
       
   503 
       
   504 // Helper for performing raw accesses (knows only of memory ordering
       
   505 // atomicity decorators as well as compressed oops)
       
   506 template <DecoratorSet decorators = INTERNAL_EMPTY>
       
   507 class RawAccess: public Access<AS_RAW | decorators> {};
       
   508 
       
   509 // Helper for performing normal accesses on the heap. These accesses
       
   510 // may resolve an accessor on a GC barrier set
       
   511 template <DecoratorSet decorators = INTERNAL_EMPTY>
       
   512 class HeapAccess: public Access<IN_HEAP | decorators> {};
       
   513 
       
   514 // Helper for performing normal accesses in roots. These accesses
       
   515 // may resolve an accessor on a GC barrier set
       
   516 template <DecoratorSet decorators = INTERNAL_EMPTY>
       
   517 class RootAccess: public Access<IN_ROOT | decorators> {};
       
   518 
       
   519 #endif // SHARE_VM_RUNTIME_ACCESS_HPP