/*

 * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.

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

 *

 * This code is free software; you can redistribute it and/or modify it

 * 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_VM_RUNTIME_ATOMIC_HPP

#define SHARE_VM_RUNTIME_ATOMIC_HPP

#include "memory/allocation.hpp"

class Atomic : AllStatic {

 public:

  // Atomic operations on jlong types are not available on all 32-bit

  // platforms. If atomic ops on jlongs are defined here they must only

  // be used from code that verifies they are available at runtime and

  // can provide an alternative action if not - see supports_cx8() for

  // a means to test availability.

  // The memory operations that are mentioned with each of the atomic

  // function families come from src/share/vm/runtime/orderAccess.hpp,

  // e.g., <fence> is described in that file and is implemented by the

  // OrderAccess::fence() function. See that file for the gory details

  // on the Memory Access Ordering Model.

  // All of the atomic operations that imply a read-modify-write action

  // guarantee a two-way memory barrier across that operation. Historically

  // these semantics reflect the strength of atomic operations that are

  // provided on SPARC/X86. We assume that strength is necessary unless

  // we can prove that a weaker form is sufficiently safe.

  // Atomically store to a location

  inline static void store    (jbyte    store_value, jbyte*    dest);

  inline static void store    (jshort   store_value, jshort*   dest);

  inline static void store    (jint     store_value, jint*     dest);

  // See comment above about using jlong atomics on 32-bit platforms

  inline static void store    (jlong    store_value, jlong*    dest);

  inline static void store_ptr(intptr_t store_value, intptr_t* dest);

  inline static void store_ptr(void*    store_value, void*     dest);

  inline static void store    (jbyte    store_value, volatile jbyte*    dest);

  inline static void store    (jshort   store_value, volatile jshort*   dest);

  inline static void store    (jint     store_value, volatile jint*     dest);

  // See comment above about using jlong atomics on 32-bit platforms

  inline static void store    (jlong    store_value, volatile jlong*    dest);

  inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest);

  inline static void store_ptr(void*    store_value, volatile void*     dest);

  // See comment above about using jlong atomics on 32-bit platforms

  inline static jlong load(volatile jlong* src);

  // Atomically add to a location. Returns updated value. add*() provide:

  // <fence> add-value-to-dest <membar StoreLoad|StoreStore>

  inline static jint     add    (jint     add_value, volatile jint*     dest);

  inline static size_t   add    (size_t   add_value, volatile size_t*   dest);

  inline static intptr_t add_ptr(intptr_t add_value, volatile intptr_t* dest);

  inline static void*    add_ptr(intptr_t add_value, volatile void*     dest);

  // See comment above about using jlong atomics on 32-bit platforms

  // Atomically increment location. inc*() provide:

  // <fence> increment-dest <membar StoreLoad|StoreStore>

  inline static void inc    (volatile jint*     dest);

  inline static void inc    (volatile size_t*   dest);

  inline static void inc_ptr(volatile intptr_t* dest);

  inline static void inc_ptr(volatile void*     dest);

  // Atomically decrement a location. dec*() provide:

  // <fence> decrement-dest <membar StoreLoad|StoreStore>

  inline static void dec    (volatile jint*     dest);

  inline static void dec    (volatile size_t*   dest);

  inline static void dec_ptr(volatile intptr_t* dest);

  inline static void dec_ptr(volatile void*     dest);

  // Performs atomic exchange of *dest with exchange_value. Returns old

  // prior value of *dest. xchg*() provide:

  // <fence> exchange-value-with-dest <membar StoreLoad|StoreStore>

  // Performs atomic compare of *dest and compare_value, and exchanges

  // *dest with exchange_value if the comparison succeeded. Returns prior

  // value of *dest. cmpxchg*() provide:

  // <fence> compare-and-exchange <membar StoreLoad|StoreStore>

  // See comment above about using jlong atomics on 32-bit platforms

};

// To use Atomic::inc(jshort* dest) and Atomic::dec(jshort* dest), the address must be specially

// aligned, such that (*dest) occupies the upper 16 bits of an aligned 32-bit word. The best way to

// achieve is to place your short value next to another short value, which doesn't need atomic ops.

//

// Example

//  ATOMIC_SHORT_PAIR(

//    volatile short _refcount,  // needs atomic operation

//    unsigned short _length     // number of UTF8 characters in the symbol (does not need atomic op)

//  );

#ifdef VM_LITTLE_ENDIAN

  #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl)  \

    non_atomic_decl;                                       \

    atomic_decl

#else

  #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl)  \

    atomic_decl;                                           \

    non_atomic_decl

#endif

#endif // SHARE_VM_RUNTIME_ATOMIC_HPP