/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_RUNTIME_READ_BARRIER_INL_H_
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#define ART_RUNTIME_READ_BARRIER_INL_H_
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#include "read_barrier.h"
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#include "gc/accounting/read_barrier_table.h"
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#include "gc/collector/concurrent_copying-inl.h"
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#include "gc/heap.h"
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#include "mirror/object-readbarrier-inl.h"
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#include "mirror/object_reference.h"
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#include "mirror/reference.h"
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#include "runtime.h"
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namespace art {
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// Disabled for performance reasons.
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static constexpr bool kCheckDebugDisallowReadBarrierCount = false;
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template <typename MirrorType, bool kIsVolatile, ReadBarrierOption kReadBarrierOption,
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bool kAlwaysUpdateField>
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inline MirrorType* ReadBarrier::Barrier(
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mirror::Object* obj, MemberOffset offset, mirror::HeapReference<MirrorType>* ref_addr) {
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constexpr bool with_read_barrier = kReadBarrierOption == kWithReadBarrier;
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if (kUseReadBarrier && with_read_barrier) {
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if (kCheckDebugDisallowReadBarrierCount) {
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Thread* const self = Thread::Current();
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if (self != nullptr) {
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CHECK_EQ(self->GetDebugDisallowReadBarrierCount(), 0u);
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}
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}
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if (kUseBakerReadBarrier) {
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// fake_address_dependency (must be zero) is used to create artificial data dependency from
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// the is_gray load to the ref field (ptr) load to avoid needing a load-load barrier between
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// the two.
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uintptr_t fake_address_dependency;
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bool is_gray = IsGray(obj, &fake_address_dependency);
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if (kEnableReadBarrierInvariantChecks) {
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CHECK_EQ(fake_address_dependency, 0U) << obj << " rb_state=" << obj->GetReadBarrierState();
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}
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ref_addr = reinterpret_cast<mirror::HeapReference<MirrorType>*>(
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fake_address_dependency | reinterpret_cast<uintptr_t>(ref_addr));
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MirrorType* ref = ref_addr->template AsMirrorPtr<kIsVolatile>();
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MirrorType* old_ref = ref;
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if (is_gray) {
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// Slow-path.
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ref = reinterpret_cast<MirrorType*>(Mark(ref));
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// If kAlwaysUpdateField is true, update the field atomically. This may fail if mutator
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// updates before us, but it's OK.
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if (kAlwaysUpdateField && ref != old_ref) {
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obj->CasFieldObjectWithoutWriteBarrier<false, false>(offset,
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old_ref,
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ref,
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CASMode::kStrong,
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std::memory_order_release);
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}
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}
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AssertToSpaceInvariant(obj, offset, ref);
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return ref;
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} else if (kUseBrooksReadBarrier) {
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// To be implemented.
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return ref_addr->template AsMirrorPtr<kIsVolatile>();
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} else if (kUseTableLookupReadBarrier) {
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MirrorType* ref = ref_addr->template AsMirrorPtr<kIsVolatile>();
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MirrorType* old_ref = ref;
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// The heap or the collector can be null at startup. TODO: avoid the need for this null check.
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gc::Heap* heap = Runtime::Current()->GetHeap();
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if (heap != nullptr && heap->GetReadBarrierTable()->IsSet(old_ref)) {
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ref = reinterpret_cast<MirrorType*>(Mark(old_ref));
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// Update the field atomically. This may fail if mutator updates before us, but it's ok.
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if (ref != old_ref) {
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obj->CasFieldObjectWithoutWriteBarrier<false, false>(offset,
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old_ref,
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ref,
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CASMode::kStrong,
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std::memory_order_release);
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}
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}
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AssertToSpaceInvariant(obj, offset, ref);
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return ref;
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} else {
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LOG(FATAL) << "Unexpected read barrier type";
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UNREACHABLE();
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}
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} else {
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// No read barrier.
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return ref_addr->template AsMirrorPtr<kIsVolatile>();
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}
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}
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template <typename MirrorType, ReadBarrierOption kReadBarrierOption>
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inline MirrorType* ReadBarrier::BarrierForRoot(MirrorType** root,
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GcRootSource* gc_root_source) {
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MirrorType* ref = *root;
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const bool with_read_barrier = kReadBarrierOption == kWithReadBarrier;
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if (kUseReadBarrier && with_read_barrier) {
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if (kIsDebugBuild) {
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Thread* const self = Thread::Current();
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if (self != nullptr) {
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CHECK_EQ(self->GetDebugDisallowReadBarrierCount(), 0u);
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}
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}
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if (kUseBakerReadBarrier) {
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// TODO: separate the read barrier code from the collector code more.
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Thread* self = Thread::Current();
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if (self != nullptr && self->GetIsGcMarking()) {
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ref = reinterpret_cast<MirrorType*>(Mark(ref));
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}
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AssertToSpaceInvariant(gc_root_source, ref);
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return ref;
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} else if (kUseBrooksReadBarrier) {
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// To be implemented.
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return ref;
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} else if (kUseTableLookupReadBarrier) {
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Thread* self = Thread::Current();
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if (self != nullptr &&
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self->GetIsGcMarking() &&
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Runtime::Current()->GetHeap()->GetReadBarrierTable()->IsSet(ref)) {
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MirrorType* old_ref = ref;
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ref = reinterpret_cast<MirrorType*>(Mark(old_ref));
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// Update the field atomically. This may fail if mutator updates before us, but it's ok.
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if (ref != old_ref) {
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Atomic<MirrorType*>* atomic_root = reinterpret_cast<Atomic<MirrorType*>*>(root);
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atomic_root->CompareAndSetStrongRelaxed(old_ref, ref);
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}
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}
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AssertToSpaceInvariant(gc_root_source, ref);
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return ref;
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} else {
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LOG(FATAL) << "Unexpected read barrier type";
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UNREACHABLE();
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}
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} else {
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return ref;
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}
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}
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// TODO: Reduce copy paste
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template <typename MirrorType, ReadBarrierOption kReadBarrierOption>
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inline MirrorType* ReadBarrier::BarrierForRoot(mirror::CompressedReference<MirrorType>* root,
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GcRootSource* gc_root_source) {
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MirrorType* ref = root->AsMirrorPtr();
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const bool with_read_barrier = kReadBarrierOption == kWithReadBarrier;
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if (with_read_barrier && kUseBakerReadBarrier) {
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// TODO: separate the read barrier code from the collector code more.
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Thread* self = Thread::Current();
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if (self != nullptr && self->GetIsGcMarking()) {
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ref = reinterpret_cast<MirrorType*>(Mark(ref));
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}
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AssertToSpaceInvariant(gc_root_source, ref);
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return ref;
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} else if (with_read_barrier && kUseBrooksReadBarrier) {
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// To be implemented.
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return ref;
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} else if (with_read_barrier && kUseTableLookupReadBarrier) {
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Thread* self = Thread::Current();
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if (self != nullptr &&
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self->GetIsGcMarking() &&
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Runtime::Current()->GetHeap()->GetReadBarrierTable()->IsSet(ref)) {
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auto old_ref = mirror::CompressedReference<MirrorType>::FromMirrorPtr(ref);
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ref = reinterpret_cast<MirrorType*>(Mark(ref));
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auto new_ref = mirror::CompressedReference<MirrorType>::FromMirrorPtr(ref);
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// Update the field atomically. This may fail if mutator updates before us, but it's ok.
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if (new_ref.AsMirrorPtr() != old_ref.AsMirrorPtr()) {
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auto* atomic_root =
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reinterpret_cast<Atomic<mirror::CompressedReference<MirrorType>>*>(root);
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atomic_root->CompareAndSetStrongRelaxed(old_ref, new_ref);
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}
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}
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AssertToSpaceInvariant(gc_root_source, ref);
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return ref;
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} else {
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return ref;
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}
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}
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template <typename MirrorType>
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inline MirrorType* ReadBarrier::IsMarked(MirrorType* ref) {
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// Only read-barrier configurations can have mutators run while
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// the GC is marking.
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if (!kUseReadBarrier) {
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return ref;
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}
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// IsMarked does not handle null, so handle it here.
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if (ref == nullptr) {
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return nullptr;
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}
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// IsMarked should only be called when the GC is marking.
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if (!Thread::Current()->GetIsGcMarking()) {
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return ref;
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}
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return reinterpret_cast<MirrorType*>(
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Runtime::Current()->GetHeap()->ConcurrentCopyingCollector()->IsMarked(ref));
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}
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inline bool ReadBarrier::IsDuringStartup() {
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gc::Heap* heap = Runtime::Current()->GetHeap();
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if (heap == nullptr) {
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// During startup, the heap can be null.
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return true;
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}
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if (heap->CurrentCollectorType() != gc::kCollectorTypeCC) {
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// CC isn't running.
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return true;
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}
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gc::collector::ConcurrentCopying* collector = heap->ConcurrentCopyingCollector();
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if (collector == nullptr) {
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// During startup, the collector can be null.
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return true;
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}
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return false;
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}
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inline void ReadBarrier::AssertToSpaceInvariant(mirror::Object* obj, MemberOffset offset,
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mirror::Object* ref) {
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if (kEnableToSpaceInvariantChecks) {
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if (ref == nullptr || IsDuringStartup()) {
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return;
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}
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Runtime::Current()->GetHeap()->ConcurrentCopyingCollector()->
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AssertToSpaceInvariant(obj, offset, ref);
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}
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}
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inline void ReadBarrier::AssertToSpaceInvariant(GcRootSource* gc_root_source,
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mirror::Object* ref) {
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if (kEnableToSpaceInvariantChecks) {
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if (ref == nullptr || IsDuringStartup()) {
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return;
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}
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Runtime::Current()->GetHeap()->ConcurrentCopyingCollector()->
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AssertToSpaceInvariant(gc_root_source, ref);
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}
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}
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inline mirror::Object* ReadBarrier::Mark(mirror::Object* obj) {
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return Runtime::Current()->GetHeap()->ConcurrentCopyingCollector()->MarkFromReadBarrier(obj);
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}
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inline bool ReadBarrier::IsGray(mirror::Object* obj, uintptr_t* fake_address_dependency) {
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return obj->GetReadBarrierState(fake_address_dependency) == kGrayState;
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}
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inline bool ReadBarrier::IsGray(mirror::Object* obj) {
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// Use a load-acquire to load the read barrier bit to avoid reordering with the subsequent load.
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// GetReadBarrierStateAcquire() has load-acquire semantics.
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return obj->GetReadBarrierStateAcquire() == kGrayState;
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}
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} // namespace art
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#endif // ART_RUNTIME_READ_BARRIER_INL_H_
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