/*

 * Copyright (c) 2001, 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.

 *

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

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

 * questions.

 *

 */

#include "precompiled.hpp"

#include "runtime/atomic.inline.hpp"

/*

 * This is the default implementation of byte-sized cmpxchg. It emulates jbyte-sized cmpxchg

 * in terms of jint-sized cmpxchg. Platforms may override this by defining their own inline definition

 * as well as defining VM_HAS_SPECIALIZED_CMPXCHG_BYTE. This will cause the platform specific

 * implementation to be used instead.

 */

jbyte Atomic::cmpxchg_general(jbyte exchange_value, volatile jbyte* dest, jbyte compare_value) {

  assert(sizeof(jbyte) == 1, "assumption.");

  uintptr_t dest_addr = (uintptr_t)dest;

  uintptr_t offset = dest_addr % sizeof(jint);

  volatile jint* dest_int = (volatile jint*)(dest_addr - offset);

  jint cur = *dest_int;

  jbyte* cur_as_bytes = (jbyte*)(&cur);

  jint new_val = cur;

  jbyte* new_val_as_bytes = (jbyte*)(&new_val);

  new_val_as_bytes[offset] = exchange_value;

  while (cur_as_bytes[offset] == compare_value) {

    jint res = cmpxchg(new_val, dest_int, cur);

    if (res == cur) break;

    cur = res;

    new_val = cur;

    new_val_as_bytes[offset] = exchange_value;

  }

  return cur_as_bytes[offset];

}

unsigned Atomic::xchg(unsigned int exchange_value, volatile unsigned int* dest) {

  assert(sizeof(unsigned int) == sizeof(jint), "more work to do");

  return (unsigned int)Atomic::xchg((jint)exchange_value, (volatile jint*)dest);

}

unsigned Atomic::cmpxchg(unsigned int exchange_value,

                         volatile unsigned int* dest, unsigned int compare_value) {

  assert(sizeof(unsigned int) == sizeof(jint), "more work to do");

  return (unsigned int)Atomic::cmpxchg((jint)exchange_value, (volatile jint*)dest,

                                       (jint)compare_value);

}

jlong Atomic::add(jlong    add_value, volatile jlong*    dest) {

  jlong old = load(dest);

  jlong new_value = old + add_value;

  while (old != cmpxchg(new_value, dest, old)) {

    old = load(dest);

    new_value = old + add_value;

  }

  return old;

}

void Atomic::inc(volatile short* dest) {

  // Most platforms do not support atomic increment on a 2-byte value. However,

  // if the value occupies the most significant 16 bits of an aligned 32-bit

  // word, then we can do this with an atomic add of 0x10000 to the 32-bit word.

  //

  // The least significant parts of this 32-bit word will never be affected, even

  // in case of overflow/underflow.

  //

  // Use the ATOMIC_SHORT_PAIR macro to get the desired alignment.

#ifdef VM_LITTLE_ENDIAN

  assert((intx(dest) & 0x03) == 0x02, "wrong alignment");

  (void)Atomic::add(0x10000, (volatile int*)(dest-1));

#else

  assert((intx(dest) & 0x03) == 0x00, "wrong alignment");

  (void)Atomic::add(0x10000, (volatile int*)(dest));

#endif

}

void Atomic::dec(volatile short* dest) {

#ifdef VM_LITTLE_ENDIAN

  assert((intx(dest) & 0x03) == 0x02, "wrong alignment");

  (void)Atomic::add(-0x10000, (volatile int*)(dest-1));

#else

  assert((intx(dest) & 0x03) == 0x00, "wrong alignment");

  (void)Atomic::add(-0x10000, (volatile int*)(dest));

#endif

}