/*

 * Copyright (c) 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 "accessBackend.inline.hpp"

#include "gc/shared/collectedHeap.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/vm_version.hpp"

#include "utilities/copy.hpp"

namespace AccessInternal {

  // VM_Version::supports_cx8() is a surrogate for 'supports atomic long memory ops'.

  //

  // On platforms which do not support atomic compare-and-swap of jlong (8 byte)

  // values we have to use a lock-based scheme to enforce atomicity. This has to be

  // applied to all Unsafe operations that set the value of a jlong field. Even so

  // the compareAndSwapLong operation will not be atomic with respect to direct stores

  // to the field from Java code. It is important therefore that any Java code that

  // utilizes these Unsafe jlong operations does not perform direct stores. To permit

  // direct loads of the field from Java code we must also use Atomic::store within the

  // locked regions. And for good measure, in case there are direct stores, we also

  // employ Atomic::load within those regions. Note that the field in question must be

  // volatile and so must have atomic load/store accesses applied at the Java level.

  //

  // The locking scheme could utilize a range of strategies for controlling the locking

  // granularity: from a lock per-field through to a single global lock. The latter is

  // the simplest and is used for the current implementation. Note that the Java object

  // that contains the field, can not, in general, be used for locking. To do so can lead

  // to deadlocks as we may introduce locking into what appears to the Java code to be a

  // lock-free path.

  //

  // As all the locked-regions are very short and themselves non-blocking we can treat

  // them as leaf routines and elide safepoint checks (ie we don't perform any thread

  // state transitions even when blocking for the lock). Note that if we do choose to

  // add safepoint checks and thread state transitions, we must ensure that we calculate

  // the address of the field _after_ we have acquired the lock, else the object may have

  // been moved by the GC

#ifndef SUPPORTS_NATIVE_CX8

  // This is intentionally in the cpp file rather than the .inline.hpp file. It seems

  // desirable to trade faster JDK build times (not propagating vm_version.hpp)

  // for slightly worse runtime atomic jlong performance on 32 bit machines with

  // support for 64 bit atomics.

  bool wide_atomic_needs_locking() {

    return !VM_Version::supports_cx8();

  }

  AccessLocker::AccessLocker() {

    assert(!VM_Version::supports_cx8(), "why else?");

    UnsafeJlong_lock->lock_without_safepoint_check();

  }

  AccessLocker::~AccessLocker() {

    UnsafeJlong_lock->unlock();

  }

#endif

// These forward copying calls to Copy without exposing the Copy type in headers unnecessarily

  void arraycopy_arrayof_conjoint_oops(void* src, void* dst, size_t length) {

    Copy::arrayof_conjoint_oops(reinterpret_cast<HeapWord*>(src),

                                reinterpret_cast<HeapWord*>(dst), length);

  }

  void arraycopy_conjoint_oops(oop* src, oop* dst, size_t length) {

    Copy::conjoint_oops_atomic(src, dst, length);

  }

  void arraycopy_conjoint_oops(narrowOop* src, narrowOop* dst, size_t length) {

    Copy::conjoint_oops_atomic(src, dst, length);

  }

  void arraycopy_disjoint_words(void* src, void* dst, size_t length) {

    Copy::disjoint_words(reinterpret_cast<HeapWord*>(src),

                         reinterpret_cast<HeapWord*>(dst), length);

  }

  void arraycopy_disjoint_words_atomic(void* src, void* dst, size_t length) {

    Copy::disjoint_words_atomic(reinterpret_cast<HeapWord*>(src),

                                reinterpret_cast<HeapWord*>(dst), length);

  }

  template<>

  void arraycopy_conjoint<jbyte>(jbyte* src, jbyte* dst, size_t length) {

    Copy::conjoint_jbytes(src, dst, length);

  }

  template<>

  void arraycopy_conjoint<jshort>(jshort* src, jshort* dst, size_t length) {

    Copy::conjoint_jshorts_atomic(src, dst, length);

  }

  template<>

  void arraycopy_conjoint<jint>(jint* src, jint* dst, size_t length) {

    Copy::conjoint_jints_atomic(src, dst, length);

  }

  template<>

  void arraycopy_conjoint<jlong>(jlong* src, jlong* dst, size_t length) {

    Copy::conjoint_jlongs_atomic(src, dst, length);

  }

  template<>

  void arraycopy_arrayof_conjoint<jbyte>(jbyte* src, jbyte* dst, size_t length) {

    Copy::arrayof_conjoint_jbytes(reinterpret_cast<HeapWord*>(src),

                                  reinterpret_cast<HeapWord*>(dst),

                                  length);

  }

  template<>

  void arraycopy_arrayof_conjoint<jshort>(jshort* src, jshort* dst, size_t length) {

    Copy::arrayof_conjoint_jshorts(reinterpret_cast<HeapWord*>(src),

                                   reinterpret_cast<HeapWord*>(dst),

                                   length);

  }

  template<>

  void arraycopy_arrayof_conjoint<jint>(jint* src, jint* dst, size_t length) {

    Copy::arrayof_conjoint_jints(reinterpret_cast<HeapWord*>(src),

                                 reinterpret_cast<HeapWord*>(dst),

                                 length);

  }

  template<>

  void arraycopy_arrayof_conjoint<jlong>(jlong* src, jlong* dst, size_t length) {

    Copy::arrayof_conjoint_jlongs(reinterpret_cast<HeapWord*>(src),

                                  reinterpret_cast<HeapWord*>(dst),

                                  length);

  }

  template<>

  void arraycopy_conjoint_atomic<jbyte>(jbyte* src, jbyte* dst, size_t length) {

    Copy::conjoint_jbytes_atomic(src, dst, length);

  }

  template<>

  void arraycopy_conjoint_atomic<jshort>(jshort* src, jshort* dst, size_t length) {

    Copy::conjoint_jshorts_atomic(src, dst, length);

  }

  template<>

  void arraycopy_conjoint_atomic<jint>(jint* src, jint* dst, size_t length) {

    Copy::conjoint_jints_atomic(src, dst, length);

  }

  template<>

  void arraycopy_conjoint_atomic<jlong>(jlong* src, jlong* dst, size_t length) {

    Copy::conjoint_jlongs_atomic(src, dst, length);

  }

}

template void AccessInternal::arraycopy_conjoint<jbyte>(jbyte* src, jbyte* dst, size_t length);

template void AccessInternal::arraycopy_conjoint<jshort>(jshort* src, jshort* dst, size_t length);

template void AccessInternal::arraycopy_conjoint<jint>(jint* src, jint* dst, size_t length);

template void AccessInternal::arraycopy_conjoint<jlong>(jlong* src, jlong* dst, size_t length);

template void AccessInternal::arraycopy_arrayof_conjoint<jbyte>(jbyte* src, jbyte* dst, size_t length);

template void AccessInternal::arraycopy_arrayof_conjoint<jshort>(jshort* src, jshort* dst, size_t length);

template void AccessInternal::arraycopy_arrayof_conjoint<jint>(jint* src, jint* dst, size_t length);

template void AccessInternal::arraycopy_arrayof_conjoint<jlong>(jlong* src, jlong* dst, size_t length);

template void AccessInternal::arraycopy_conjoint_atomic<jbyte>(jbyte* src, jbyte* dst, size_t length);

template void AccessInternal::arraycopy_conjoint_atomic<jshort>(jshort* src, jshort* dst, size_t length);

template void AccessInternal::arraycopy_conjoint_atomic<jint>(jint* src, jint* dst, size_t length);

template void AccessInternal::arraycopy_conjoint_atomic<jlong>(jlong* src, jlong* dst, size_t length);