/*

 * 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

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

 * questions.

 */

#include "precompiled.hpp"

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

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

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

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

#include "oops/oop.inline.hpp"

#include "runtime/safepoint.hpp"

#include "utilities/debug.hpp"

bool ZBarrier::during_mark() {

  return ZGlobalPhase == ZPhaseMark;

}

bool ZBarrier::during_relocate() {

  return ZGlobalPhase == ZPhaseRelocate;

}

template <bool finalizable>

bool ZBarrier::should_mark_through(uintptr_t addr) {

  // Finalizable marked oops can still exists on the heap after marking

  // has completed, in which case we just want to convert this into a

  // good oop and not push it on the mark stack.

  if (!during_mark()) {

    assert(ZAddress::is_marked(addr), "Should be marked");

    assert(ZAddress::is_finalizable(addr), "Should be finalizable");

    return false;

  }

  // During marking, we mark through already marked oops to avoid having

  // some large part of the object graph hidden behind a pushed, but not

  // yet flushed, entry on a mutator mark stack. Always marking through

  // allows the GC workers to proceed through the object graph even if a

  // mutator touched an oop first, which in turn will reduce the risk of

  // having to flush mark stacks multiple times to terminate marking.

  //

  // However, when doing finalizable marking we don't always want to mark

  // through. First, marking through an already strongly marked oop would

  // be wasteful, since we will then proceed to do finalizable marking on

  // an object which is, or will be, marked strongly. Second, marking

  // through an already finalizable marked oop would also be wasteful,

  // since such oops can never end up on a mutator mark stack and can

  // therefore not hide some part of the object graph from GC workers.

  if (finalizable) {

    return !ZAddress::is_marked(addr);

  }

  // Mark through

  return true;

}

template <bool finalizable, bool publish>

uintptr_t ZBarrier::mark(uintptr_t addr) {

  uintptr_t good_addr;

  if (ZAddress::is_marked(addr)) {

    // Already marked, but try to mark though anyway

    good_addr = ZAddress::good(addr);

  } else if (ZAddress::is_remapped(addr)) {

    // Already remapped, but also needs to be marked

    good_addr = ZAddress::good(addr);

  } else {

    // Needs to be both remapped and marked

    good_addr = remap(addr);

  }

  // Mark

  if (should_mark_through<finalizable>(addr)) {

    ZHeap::heap()->mark_object<finalizable, publish>(good_addr);

  }

  return good_addr;

}

uintptr_t ZBarrier::remap(uintptr_t addr) {

  assert(!ZAddress::is_good(addr), "Should not be good");

  assert(!ZAddress::is_weak_good(addr), "Should not be weak good");

  if (ZHeap::heap()->is_relocating(addr)) {

    // Forward

    return ZHeap::heap()->forward_object(addr);

  }

  // Remap

  return ZAddress::good(addr);

}

uintptr_t ZBarrier::relocate(uintptr_t addr) {

  assert(!ZAddress::is_good(addr), "Should not be good");

  assert(!ZAddress::is_weak_good(addr), "Should not be weak good");

  if (ZHeap::heap()->is_relocating(addr)) {

    // Relocate

    return ZHeap::heap()->relocate_object(addr);

  }

  // Remap

  return ZAddress::good(addr);

}

uintptr_t ZBarrier::relocate_or_mark(uintptr_t addr) {

  return during_relocate() ? relocate(addr) : mark<Strong, Publish>(addr);

}

uintptr_t ZBarrier::relocate_or_remap(uintptr_t addr) {

  return during_relocate() ? relocate(addr) : remap(addr);

}

//

// Load barrier

//

uintptr_t ZBarrier::load_barrier_on_oop_slow_path(uintptr_t addr) {

  return relocate_or_mark(addr);

}

void ZBarrier::load_barrier_on_oop_fields(oop o) {

  assert(ZOop::is_good(o), "Should be good");

  ZLoadBarrierOopClosure cl;

  o->oop_iterate(&cl);

}

//

// Weak load barrier

//

uintptr_t ZBarrier::weak_load_barrier_on_oop_slow_path(uintptr_t addr) {

  return ZAddress::is_weak_good(addr) ? ZAddress::good(addr) : relocate_or_remap(addr);

}

uintptr_t ZBarrier::weak_load_barrier_on_weak_oop_slow_path(uintptr_t addr) {

  const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr);

  if (ZHeap::heap()->is_object_strongly_live(good_addr)) {

    return good_addr;

  }

  // Not strongly live

  return 0;

}

uintptr_t ZBarrier::weak_load_barrier_on_phantom_oop_slow_path(uintptr_t addr) {

  const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr);

  if (ZHeap::heap()->is_object_live(good_addr)) {

    return good_addr;

  }

  // Not live

  return 0;

}

//

// Keep alive barrier

//

uintptr_t ZBarrier::keep_alive_barrier_on_weak_oop_slow_path(uintptr_t addr) {

  const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr);

  assert(ZHeap::heap()->is_object_strongly_live(good_addr), "Should be live");

  return good_addr;

}

uintptr_t ZBarrier::keep_alive_barrier_on_phantom_oop_slow_path(uintptr_t addr) {

  const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr);

  assert(ZHeap::heap()->is_object_live(good_addr), "Should be live");

  return good_addr;

}

//

// Mark barrier

//

uintptr_t ZBarrier::mark_barrier_on_oop_slow_path(uintptr_t addr) {

  return mark<Strong, Overflow>(addr);

}

uintptr_t ZBarrier::mark_barrier_on_finalizable_oop_slow_path(uintptr_t addr) {

  const uintptr_t good_addr = mark<Finalizable, Overflow>(addr);

  if (ZAddress::is_good(addr)) {

    // If the oop was already strongly marked/good, then we do

    // not want to downgrade it to finalizable marked/good.

    return good_addr;

  }

  // Make the oop finalizable marked/good, instead of normal marked/good.

  // This is needed because an object might first becomes finalizable

  // marked by the GC, and then loaded by a mutator thread. In this case,

  // the mutator thread must be able to tell that the object needs to be

  // strongly marked. The finalizable bit in the oop exists to make sure

  // that a load of a finalizable marked oop will fall into the barrier

  // slow path so that we can mark the object as strongly reachable.

  return ZAddress::finalizable_good(good_addr);

}

uintptr_t ZBarrier::mark_barrier_on_root_oop_slow_path(uintptr_t addr) {

  assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");

  assert(during_mark(), "Invalid phase");

  // Mark

  return mark<Strong, Publish>(addr);

}

//

// Relocate barrier

//

uintptr_t ZBarrier::relocate_barrier_on_root_oop_slow_path(uintptr_t addr) {

  assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");

  assert(during_relocate(), "Invalid phase");

  // Relocate

  return relocate(addr);

}

//

// Narrow oop variants, never used.

//

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

  ShouldNotReachHere();

  return NULL;

}

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

  ShouldNotReachHere();

  return NULL;

}

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

  ShouldNotReachHere();

}

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

  ShouldNotReachHere();

  return NULL;

}

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

  ShouldNotReachHere();

  return NULL;

}

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

  ShouldNotReachHere();

  return NULL;

}

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

  ShouldNotReachHere();

  return NULL;

}

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

  ShouldNotReachHere();

  return NULL;

}