/*

 * Copyright (c) 2015, 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

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 */

#ifndef SHARE_GC_Z_ZBARRIER_INLINE_HPP

#define SHARE_GC_Z_ZBARRIER_INLINE_HPP

#include "gc/z/zAddress.inline.hpp"

#include "gc/z/zBarrier.hpp"

#include "gc/z/zOop.inline.hpp"

#include "gc/z/zResurrection.inline.hpp"

#include "runtime/atomic.hpp"

template <ZBarrierFastPath fast_path, ZBarrierSlowPath slow_path>

inline oop ZBarrier::barrier(volatile oop* p, oop o) {

  uintptr_t addr = ZOop::to_address(o);

retry:

  // Fast path

  if (fast_path(addr)) {

    return ZOop::to_oop(addr);

  }

  // Slow path

  const uintptr_t good_addr = slow_path(addr);

  // Self heal, but only if the address was actually updated by the slow path,

  // which might not be the case, e.g. when marking through an already good oop.

  if (p != NULL && good_addr != addr) {

    const uintptr_t prev_addr = Atomic::cmpxchg(good_addr, (volatile uintptr_t*)p, addr);

    if (prev_addr != addr) {

      // Some other thread overwrote the oop. If this oop was updated by a

      // weak barrier the new oop might not be good, in which case we need

      // to re-apply this barrier.

      addr = prev_addr;

      goto retry;

    }

  }

  return ZOop::to_oop(good_addr);

}

template <ZBarrierFastPath fast_path, ZBarrierSlowPath slow_path>

inline oop ZBarrier::weak_barrier(volatile oop* p, oop o) {

  const uintptr_t addr = ZOop::to_address(o);

  // Fast path

  if (fast_path(addr)) {

    // Return the good address instead of the weak good address

    // to ensure that the currently active heap view is used.

    return ZOop::to_oop(ZAddress::good_or_null(addr));

  }

  // Slow path

  uintptr_t good_addr = slow_path(addr);

  // Self heal unless the address returned from the slow path is null,

  // in which case resurrection was blocked and we must let the reference

  // processor clear the oop. Mutators are not allowed to clear oops in

  // these cases, since that would be similar to calling Reference.clear(),

  // which would make the reference non-discoverable or silently dropped

  // by the reference processor.

  if (p != NULL && good_addr != 0) {

    // The slow path returns a good/marked address, but we never mark oops

    // in a weak load barrier so we always self heal with the remapped address.

    const uintptr_t weak_good_addr = ZAddress::remapped(good_addr);

    const uintptr_t prev_addr = Atomic::cmpxchg(weak_good_addr, (volatile uintptr_t*)p, addr);

    if (prev_addr != addr) {

      // Some other thread overwrote the oop. The new

      // oop is guaranteed to be weak good or null.

      assert(ZAddress::is_weak_good_or_null(prev_addr), "Bad weak overwrite");

      // Return the good address instead of the weak good address

      // to ensure that the currently active heap view is used.

      good_addr = ZAddress::good_or_null(prev_addr);

    }

  }

  return ZOop::to_oop(good_addr);

}

template <ZBarrierFastPath fast_path, ZBarrierSlowPath slow_path>

inline void ZBarrier::root_barrier(oop* p, oop o) {

  const uintptr_t addr = ZOop::to_address(o);

  // Fast path

  if (fast_path(addr)) {

    return;

  }

  // Slow path

  const uintptr_t good_addr = slow_path(addr);

  // Non-atomic healing helps speed up root scanning. This is safe to do

  // since we are always healing roots in a safepoint, which means we are

  // never racing with mutators modifying roots while we are healing them.

  // It's also safe in case multiple GC threads try to heal the same root,

  // since they would always heal the root in the same way and it does not

  // matter in which order it happens.

  *p = ZOop::to_oop(good_addr);

}

inline bool ZBarrier::is_null_fast_path(uintptr_t addr) {

  return ZAddress::is_null(addr);

}

inline bool ZBarrier::is_good_or_null_fast_path(uintptr_t addr) {

  return ZAddress::is_good_or_null(addr);

}

inline bool ZBarrier::is_weak_good_or_null_fast_path(uintptr_t addr) {

  return ZAddress::is_weak_good_or_null(addr);

}

inline bool ZBarrier::is_resurrection_blocked(volatile oop* p, oop* o) {

  const bool is_blocked = ZResurrection::is_blocked();

  // Reload oop after checking the resurrection blocked state. This is

  // done to prevent a race where we first load an oop, which is logically

  // null but not yet cleared, then this oop is cleared by the reference

  // processor and resurrection is unblocked. At this point the mutator

  // would see the unblocked state and pass this invalid oop through the

  // normal barrier path, which would incorrectly try to mark this oop.

  if (p != NULL) {

    // First assign to reloaded_o to avoid compiler warning about

    // implicit dereference of volatile oop.

    const oop reloaded_o = *p;

    *o = reloaded_o;

  }

  return is_blocked;

}

//

// Load barrier

//

inline oop ZBarrier::load_barrier_on_oop(oop o) {

  return load_barrier_on_oop_field_preloaded((oop*)NULL, o);

}

inline oop ZBarrier::load_barrier_on_oop_field(volatile oop* p) {

  const oop o = *p;

  return load_barrier_on_oop_field_preloaded(p, o);

}

inline oop ZBarrier::load_barrier_on_oop_field_preloaded(volatile oop* p, oop o) {

  return barrier<is_good_or_null_fast_path, load_barrier_on_oop_slow_path>(p, o);

}

inline void ZBarrier::load_barrier_on_oop_array(volatile oop* p, size_t length) {

  for (volatile const oop* const end = p + length; p < end; p++) {

    load_barrier_on_oop_field(p);

  }

}

inline oop ZBarrier::load_barrier_on_weak_oop_field_preloaded(volatile oop* p, oop o) {

  if (is_resurrection_blocked(p, &o)) {

    return weak_barrier<is_good_or_null_fast_path, weak_load_barrier_on_weak_oop_slow_path>(p, o);

  }

  return load_barrier_on_oop_field_preloaded(p, o);

}

inline oop ZBarrier::load_barrier_on_phantom_oop_field_preloaded(volatile oop* p, oop o) {

  if (is_resurrection_blocked(p, &o)) {

    return weak_barrier<is_good_or_null_fast_path, weak_load_barrier_on_phantom_oop_slow_path>(p, o);

  }

  return load_barrier_on_oop_field_preloaded(p, o);

}

//

// Weak load barrier

//

inline oop ZBarrier::weak_load_barrier_on_oop_field_preloaded(volatile oop* p, oop o) {

  return weak_barrier<is_weak_good_or_null_fast_path, weak_load_barrier_on_oop_slow_path>(p, o);

}

inline oop ZBarrier::weak_load_barrier_on_weak_oop(oop o) {

  return weak_load_barrier_on_weak_oop_field_preloaded((oop*)NULL, o);

}

inline oop ZBarrier::weak_load_barrier_on_weak_oop_field(volatile oop* p) {

  const oop o = *p;

  return weak_load_barrier_on_weak_oop_field_preloaded(p, o);

}

inline oop ZBarrier::weak_load_barrier_on_weak_oop_field_preloaded(volatile oop* p, oop o) {

  if (is_resurrection_blocked(p, &o)) {

    return weak_barrier<is_good_or_null_fast_path, weak_load_barrier_on_weak_oop_slow_path>(p, o);

  }

  return weak_load_barrier_on_oop_field_preloaded(p, o);

}

inline oop ZBarrier::weak_load_barrier_on_phantom_oop(oop o) {

  return weak_load_barrier_on_phantom_oop_field_preloaded((oop*)NULL, o);

}

inline oop ZBarrier::weak_load_barrier_on_phantom_oop_field(volatile oop* p) {

  const oop o = *p;

  return weak_load_barrier_on_phantom_oop_field_preloaded(p, o);

}

inline oop ZBarrier::weak_load_barrier_on_phantom_oop_field_preloaded(volatile oop* p, oop o) {

  if (is_resurrection_blocked(p, &o)) {

    return weak_barrier<is_good_or_null_fast_path, weak_load_barrier_on_phantom_oop_slow_path>(p, o);

  }

  return weak_load_barrier_on_oop_field_preloaded(p, o);

}

//

// Is alive barrier

//

inline bool ZBarrier::is_alive_barrier_on_weak_oop(oop o) {

  // Check if oop is logically non-null. This operation

  // is only valid when resurrection is blocked.

  assert(ZResurrection::is_blocked(), "Invalid phase");

  return weak_load_barrier_on_weak_oop(o) != NULL;

}

inline bool ZBarrier::is_alive_barrier_on_phantom_oop(oop o) {

  // Check if oop is logically non-null. This operation

  // is only valid when resurrection is blocked.

  assert(ZResurrection::is_blocked(), "Invalid phase");

  return weak_load_barrier_on_phantom_oop(o) != NULL;

}

//

// Keep alive barrier

//

inline void ZBarrier::keep_alive_barrier_on_weak_oop_field(volatile oop* p) {

  // This operation is only valid when resurrection is blocked.

  assert(ZResurrection::is_blocked(), "Invalid phase");

  const oop o = *p;

  barrier<is_good_or_null_fast_path, keep_alive_barrier_on_weak_oop_slow_path>(p, o);

}

inline void ZBarrier::keep_alive_barrier_on_phantom_oop_field(volatile oop* p) {

  // This operation is only valid when resurrection is blocked.

  assert(ZResurrection::is_blocked(), "Invalid phase");

  const oop o = *p;

  barrier<is_good_or_null_fast_path, keep_alive_barrier_on_phantom_oop_slow_path>(p, o);

}

//

// Mark barrier

//

inline void ZBarrier::mark_barrier_on_oop_field(volatile oop* p, bool finalizable) {

  // The fast path only checks for null since the GC worker

  // threads doing marking wants to mark through good oops.

  const oop o = *p;

  if (finalizable) {

    barrier<is_null_fast_path, mark_barrier_on_finalizable_oop_slow_path>(p, o);

  } else {

    barrier<is_null_fast_path, mark_barrier_on_oop_slow_path>(p, o);

  }

}

inline void ZBarrier::mark_barrier_on_oop_array(volatile oop* p, size_t length, bool finalizable) {

  for (volatile const oop* const end = p + length; p < end; p++) {

    mark_barrier_on_oop_field(p, finalizable);

  }

}

inline void ZBarrier::mark_barrier_on_root_oop_field(oop* p) {

  const oop o = *p;

  root_barrier<is_good_or_null_fast_path, mark_barrier_on_root_oop_slow_path>(p, o);

}

//

// Relocate barrier

//

inline void ZBarrier::relocate_barrier_on_root_oop_field(oop* p) {

  const oop o = *p;

  root_barrier<is_good_or_null_fast_path, relocate_barrier_on_root_oop_slow_path>(p, o);

}

#endif // SHARE_GC_Z_ZBARRIER_INLINE_HPP