/*

 * Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved.

 * Copyright 2007, 2008, 2011, 2015, Red Hat, Inc.

 * 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.

 *

 */

#ifndef OS_CPU_LINUX_ZERO_VM_ATOMIC_LINUX_ZERO_HPP

#define OS_CPU_LINUX_ZERO_VM_ATOMIC_LINUX_ZERO_HPP

#include "runtime/os.hpp"

// Implementation of class atomic

#ifdef ARM

/*

 * __kernel_cmpxchg

 *

 * Atomically store newval in *ptr if *ptr is equal to oldval for user space.

 * Return zero if *ptr was changed or non-zero if no exchange happened.

 * The C flag is also set if *ptr was changed to allow for assembly

 * optimization in the calling code.

 *

 */

typedef int (__kernel_cmpxchg_t)(int oldval, int newval, volatile int *ptr);

#define __kernel_cmpxchg (*(__kernel_cmpxchg_t *) 0xffff0fc0)

/* Perform an atomic compare and swap: if the current value of `*PTR'

   is OLDVAL, then write NEWVAL into `*PTR'.  Return the contents of

   `*PTR' before the operation.*/

static inline int arm_compare_and_swap(int newval,

                                       volatile int *ptr,

                                       int oldval) {

  for (;;) {

      int prev = *ptr;

      if (prev != oldval)

        return prev;

      if (__kernel_cmpxchg (prev, newval, ptr) == 0)

        // Success.

        return prev;

      // We failed even though prev == oldval.  Try again.

    }

}

/* Atomically add an int to memory.  */

static inline int arm_add_and_fetch(int add_value, volatile int *ptr) {

  for (;;) {

      // Loop until a __kernel_cmpxchg succeeds.

      int prev = *ptr;

      if (__kernel_cmpxchg (prev, prev + add_value, ptr) == 0)

        return prev + add_value;

    }

}

/* Atomically write VALUE into `*PTR' and returns the previous

   contents of `*PTR'.  */

static inline int arm_lock_test_and_set(int newval, volatile int *ptr) {

  for (;;) {

      // Loop until a __kernel_cmpxchg succeeds.

      int prev = *ptr;

      if (__kernel_cmpxchg (prev, newval, ptr) == 0)

        return prev;

    }

}

#endif // ARM

template<size_t byte_size>

struct Atomic::PlatformAdd

  : Atomic::AddAndFetch<Atomic::PlatformAdd<byte_size> >

{

  template<typename I, typename D>

  D add_and_fetch(I add_value, D volatile* dest) const;

};

template<>

template<typename I, typename D>

inline D Atomic::PlatformAdd<4>::add_and_fetch(I add_value, D volatile* dest) const {

  STATIC_ASSERT(4 == sizeof(I));

  STATIC_ASSERT(4 == sizeof(D));

#ifdef ARM

  return add_using_helper<int>(arm_add_and_fetch, add_value, dest);

#else

  return __sync_add_and_fetch(dest, add_value);

#endif // ARM

}

template<>

template<typename I, typename D>

inline D Atomic::PlatformAdd<8>::add_and_fetch(I add_value, D volatile* dest) const {

  STATIC_ASSERT(8 == sizeof(I));

  STATIC_ASSERT(8 == sizeof(D));

  return __sync_add_and_fetch(dest, add_value);

}

template<>

template<typename T>

inline T Atomic::PlatformXchg<4>::operator()(T exchange_value,

                                             T volatile* dest) const {

  STATIC_ASSERT(4 == sizeof(T));

#ifdef ARM

  return xchg_using_helper<int>(arm_lock_test_and_set, exchange_value, dest);

#else

  // __sync_lock_test_and_set is a bizarrely named atomic exchange

  // operation.  Note that some platforms only support this with the

  // limitation that the only valid value to store is the immediate

  // constant 1.  There is a test for this in JNI_CreateJavaVM().

  T result = __sync_lock_test_and_set (dest, exchange_value);

  // All atomic operations are expected to be full memory barriers

  // (see atomic.hpp). However, __sync_lock_test_and_set is not

  // a full memory barrier, but an acquire barrier. Hence, this added

  // barrier.

  __sync_synchronize();

  return result;

#endif // ARM

}

template<>

template<typename T>

inline T Atomic::PlatformXchg<8>::operator()(T exchange_value,

                                             T volatile* dest) const {

  STATIC_ASSERT(8 == sizeof(T));

  T result = __sync_lock_test_and_set (dest, exchange_value);

  __sync_synchronize();

  return result;

}

// No direct support for cmpxchg of bytes; emulate using int.

template<>

struct Atomic::PlatformCmpxchg<1> : Atomic::CmpxchgByteUsingInt {};

template<>

template<typename T>

inline T Atomic::PlatformCmpxchg<4>::operator()(T exchange_value,

                                                T volatile* dest,

                                                T compare_value,

                                                cmpxchg_memory_order order) const {

  STATIC_ASSERT(4 == sizeof(T));

#ifdef ARM

  return cmpxchg_using_helper<int>(arm_compare_and_swap, exchange_value, dest, compare_value);

#else

  return __sync_val_compare_and_swap(dest, compare_value, exchange_value);

#endif // ARM

}

template<>

template<typename T>

inline T Atomic::PlatformCmpxchg<8>::operator()(T exchange_value,

                                                T volatile* dest,

                                                T compare_value,

                                                cmpxchg_memory_order order) const {

  STATIC_ASSERT(8 == sizeof(T));

  return __sync_val_compare_and_swap(dest, compare_value, exchange_value);

}

template<>

template<typename T>

inline T Atomic::PlatformLoad<8>::operator()(T const volatile* src) const {

  STATIC_ASSERT(8 == sizeof(T));

  volatile jlong dest;

  os::atomic_copy64(reinterpret_cast<const volatile jlong*>(src), reinterpret_cast<volatile jlong*>(&dest));

  return PrimitiveConversions::cast<T>(dest);

}

template<>

template<typename T>

inline void Atomic::PlatformStore<8>::operator()(T store_value,

                                                 T volatile* dest) const {

  STATIC_ASSERT(8 == sizeof(T));

  os::atomic_copy64(reinterpret_cast<const volatile jlong*>(&store_value), reinterpret_cast<volatile jlong*>(dest));

}

#endif // OS_CPU_LINUX_ZERO_VM_ATOMIC_LINUX_ZERO_HPP