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 /*

  * Copyright (c) 1999, 2010, 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.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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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.

   // 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, return updated value

   inline static jint     add    (jint     add_value, volatile jint*     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

          static jlong    add    (jlong    add_value, volatile jlong*    dest);

   // Atomically increment location

   inline static void inc    (volatile jint*     dest);

          static void inc    (volatile jshort*   dest);

   inline static void inc_ptr(volatile intptr_t* dest);

   inline static void inc_ptr(volatile void*     dest);

   // Atomically decrement a location

   inline static void dec    (volatile jint*     dest);

          static void dec    (volatile jshort*    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.

   inline static jint         xchg(jint         exchange_value, volatile jint*         dest);

          static unsigned int xchg(unsigned int exchange_value, volatile unsigned int* dest);

   inline static intptr_t xchg_ptr(intptr_t exchange_value, volatile intptr_t* dest);

   inline static void*    xchg_ptr(void*    exchange_value, volatile void*   dest);

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

   // if the comparison succeeded.  Returns prior value of *dest.  Guarantees a two-way memory

   // barrier across the cmpxchg.  I.e., it's really a 'fence_cmpxchg_acquire'.

          static jbyte    cmpxchg    (jbyte    exchange_value, volatile jbyte*    dest, jbyte    compare_value);

   inline static jint     cmpxchg    (jint     exchange_value, volatile jint*     dest, jint     compare_value);

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

   inline static jlong    cmpxchg    (jlong    exchange_value, volatile jlong*    dest, jlong    compare_value);

          static unsigned int cmpxchg(unsigned int exchange_value,

                                      volatile unsigned int* dest,

                                      unsigned int compare_value);

   inline static intptr_t cmpxchg_ptr(intptr_t exchange_value, volatile intptr_t* dest, intptr_t compare_value);

   inline static void*    cmpxchg_ptr(void*    exchange_value, volatile void*     dest, void*    compare_value);

 };

 // 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