/*

 * Copyright (c) 2008, 2017, 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.

 *

 */

#ifndef OS_CPU_LINUX_ARM_VM_ATOMIC_LINUX_ARM_HPP

#define OS_CPU_LINUX_ARM_VM_ATOMIC_LINUX_ARM_HPP

#include "runtime/os.hpp"

#include "vm_version_arm.hpp"

// Implementation of class atomic

/*

 * Atomic long operations on 32-bit ARM

 * ARM v7 supports LDREXD/STREXD synchronization instructions so no problem.

 * ARM < v7 does not have explicit 64 atomic load/store capability.

 * However, gcc emits LDRD/STRD instructions on v5te and LDM/STM on v5t

 * when loading/storing 64 bits.

 * For non-MP machines (which is all we support for ARM < v7)

 * under current Linux distros these instructions appear atomic.

 * See section A3.5.3 of ARM Architecture Reference Manual for ARM v7.

 * Also, for cmpxchg64, if ARM < v7 we check for cmpxchg64 support in the

 * Linux kernel using _kuser_helper_version. See entry-armv.S in the Linux

 * kernel source or kernel_user_helpers.txt in Linux Doc.

 */

}

#endif

// As per atomic.hpp all read-modify-write operations have to provide two-way

// barriers semantics. For AARCH64 we are using load-acquire-with-reservation and

// store-release-with-reservation. While load-acquire combined with store-release

// do not generally form two-way barriers, their use with reservations does - the

// ARMv8 architecture manual Section F "Barrier Litmus Tests" indicates they

// provide sequentially consistent semantics. All we need to add is an explicit

// barrier in the failure path of the cmpxchg operations (as these don't execute

// the store) - arguably this may be overly cautious as there is a very low

// likelihood that the hardware would pull loads/stores into the region guarded

// by the reservation.

//

// For ARMv7 we add explicit barriers in the stubs.

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 AARCH64

  D val;

  int tmp;

  __asm__ volatile(

    "1:\n\t"

    " ldaxr %w[val], [%[dest]]\n\t"

    " add %w[val], %w[val], %w[add_val]\n\t"

    " stlxr %w[tmp], %w[val], [%[dest]]\n\t"

    " cbnz %w[tmp], 1b\n\t"

    : [val] "=&r" (val), [tmp] "=&r" (tmp)

    : [add_val] "r" (add_value), [dest] "r" (dest)

    : "memory");

  return val;

#else

  return add_using_helper<jint>(os::atomic_add_func, add_value, dest);

#endif

}

#ifdef AARCH64

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));

  D val;

  int tmp;

  __asm__ volatile(

    "1:\n\t"

    " ldaxr %[val], [%[dest]]\n\t"

    " add %[val], %[val], %[add_val]\n\t"

    " stlxr %w[tmp], %[val], [%[dest]]\n\t"

    " cbnz %w[tmp], 1b\n\t"

    : [val] "=&r" (val), [tmp] "=&r" (tmp)

    : [add_val] "r" (add_value), [dest] "r" (dest)

    : "memory");

  return val;

}

#endif

template<>

template<typename T>

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

                                             T volatile* dest) const {

  STATIC_ASSERT(4 == sizeof(T));

#ifdef AARCH64

  T old_val;

  int tmp;

  __asm__ volatile(

    "1:\n\t"

    " ldaxr %w[old_val], [%[dest]]\n\t"

    " stlxr %w[tmp], %w[new_val], [%[dest]]\n\t"

    " cbnz %w[tmp], 1b\n\t"

    : [old_val] "=&r" (old_val), [tmp] "=&r" (tmp)

    : [new_val] "r" (exchange_value), [dest] "r" (dest)

    : "memory");

  return old_val;

#else

  return xchg_using_helper<jint>(os::atomic_xchg_func, exchange_value, dest);

#endif

}

#ifdef AARCH64

template<>

template<typename T>

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

                                             T volatile* dest) const {

  STATIC_ASSERT(8 == sizeof(T));

  T old_val;

  int tmp;

  __asm__ volatile(

    "1:\n\t"

    " ldaxr %[old_val], [%[dest]]\n\t"

    " stlxr %w[tmp], %[new_val], [%[dest]]\n\t"

    " cbnz %w[tmp], 1b\n\t"

    : [old_val] "=&r" (old_val), [tmp] "=&r" (tmp)

    : [new_val] "r" (exchange_value), [dest] "r" (dest)

    : "memory");

  return old_val;

}

#endif // AARCH64

// The memory_order parameter is ignored - we always provide the strongest/most-conservative ordering

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

template<>

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

#ifndef AARCH64

inline jint reorder_cmpxchg_func(jint exchange_value,

                                 jint volatile* dest,

                                 jint compare_value) {

  // Warning:  Arguments are swapped to avoid moving them for kernel call

  return (*os::atomic_cmpxchg_func)(compare_value, exchange_value, dest);

}

inline jlong reorder_cmpxchg_long_func(jlong exchange_value,

                                       jlong volatile* dest,

                                       jlong compare_value) {

  assert(VM_Version::supports_cx8(), "Atomic compare and exchange jlong not supported on this architecture!");

  // Warning:  Arguments are swapped to avoid moving them for kernel call

  return (*os::atomic_cmpxchg_long_func)(compare_value, exchange_value, dest);

}

#endif // !AARCH64

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 AARCH64

  T rv;

  int tmp;

  __asm__ volatile(

    "1:\n\t"

    " ldaxr %w[rv], [%[dest]]\n\t"

    " cmp %w[rv], %w[cv]\n\t"

    " b.ne 2f\n\t"

    " stlxr %w[tmp], %w[ev], [%[dest]]\n\t"

    " cbnz %w[tmp], 1b\n\t"

    " b 3f\n\t"

    "2:\n\t"

    " dmb sy\n\t"

    "3:\n\t"

    : [rv] "=&r" (rv), [tmp] "=&r" (tmp)

    : [ev] "r" (exchange_value), [dest] "r" (dest), [cv] "r" (compare_value)

    : "memory");

  return rv;

#else

  return cmpxchg_using_helper<jint>(reorder_cmpxchg_func, exchange_value, dest, compare_value);

#endif

}

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));

#ifdef AARCH64

  T rv;

  int tmp;

  __asm__ volatile(

    "1:\n\t"

    " ldaxr %[rv], [%[dest]]\n\t"

    " cmp %[rv], %[cv]\n\t"

    " b.ne 2f\n\t"

    " stlxr %w[tmp], %[ev], [%[dest]]\n\t"

    " cbnz %w[tmp], 1b\n\t"

    " b 3f\n\t"

    "2:\n\t"

    " dmb sy\n\t"

    "3:\n\t"

    : [rv] "=&r" (rv), [tmp] "=&r" (tmp)

    : [ev] "r" (exchange_value), [dest] "r" (dest), [cv] "r" (compare_value)

    : "memory");

  return rv;

#else

  return cmpxchg_using_helper<jlong>(reorder_cmpxchg_long_func, exchange_value, dest, compare_value);

#endif

}

#endif // OS_CPU_LINUX_ARM_VM_ATOMIC_LINUX_ARM_HPP