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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_READ_BARRIER_H_
#define ART_RUNTIME_READ_BARRIER_H_
#include <android-base/logging.h>
#include "base/logging.h" // For DECLARE_RUNTIME_DEBUG_FLAG.
#include "base/macros.h"
#include "base/mutex.h"
#include "gc_root.h"
#include "jni.h"
#include "mirror/object_reference.h"
#include "offsets.h"
#include "read_barrier_config.h"
namespace art {
namespace mirror {
class Object;
template<typename MirrorType> class HeapReference;
} // namespace mirror
class ArtMethod;
class ReadBarrier {
public:
// Enable the to-space invariant checks. This is slow and happens very often. Do not enable in
// fast-debug environment.
DECLARE_RUNTIME_DEBUG_FLAG(kEnableToSpaceInvariantChecks);
// Enable the read barrier checks. This is slow and happens very often. Do not enable in
// fast-debug environment.
DECLARE_RUNTIME_DEBUG_FLAG(kEnableReadBarrierInvariantChecks);
// Return the reference at ref_addr, invoking read barrier as appropriate.
// Ref_addr is an address within obj.
// It's up to the implementation whether the given field gets updated whereas the return value
// must be an updated reference unless kAlwaysUpdateField is true.
template <typename MirrorType,
bool kIsVolatile,
ReadBarrierOption kReadBarrierOption = kWithReadBarrier,
bool kAlwaysUpdateField = false>
ALWAYS_INLINE static MirrorType* Barrier(
mirror::Object* obj, MemberOffset offset, mirror::HeapReference<MirrorType>* ref_addr)
REQUIRES_SHARED(Locks::mutator_lock_);
// It's up to the implementation whether the given root gets updated
// whereas the return value must be an updated reference.
template <typename MirrorType, ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
ALWAYS_INLINE static MirrorType* BarrierForRoot(MirrorType** root,
GcRootSource* gc_root_source = nullptr)
REQUIRES_SHARED(Locks::mutator_lock_);
// It's up to the implementation whether the given root gets updated
// whereas the return value must be an updated reference.
template <typename MirrorType, ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
ALWAYS_INLINE static MirrorType* BarrierForRoot(mirror::CompressedReference<MirrorType>* root,
GcRootSource* gc_root_source = nullptr)
REQUIRES_SHARED(Locks::mutator_lock_);
// Return the mirror Object if it is marked, or null if not.
template <typename MirrorType>
ALWAYS_INLINE static MirrorType* IsMarked(MirrorType* ref)
REQUIRES_SHARED(Locks::mutator_lock_);
static bool IsDuringStartup();
// Without the holder object.
static void AssertToSpaceInvariant(mirror::Object* ref)
REQUIRES_SHARED(Locks::mutator_lock_) {
AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
}
// With the holder object.
static void AssertToSpaceInvariant(mirror::Object* obj, MemberOffset offset,
mirror::Object* ref)
REQUIRES_SHARED(Locks::mutator_lock_);
// With GcRootSource.
static void AssertToSpaceInvariant(GcRootSource* gc_root_source, mirror::Object* ref)
REQUIRES_SHARED(Locks::mutator_lock_);
// Without the holder object, and only with the read barrier configuration (no-op otherwise).
static void MaybeAssertToSpaceInvariant(mirror::Object* ref)
REQUIRES_SHARED(Locks::mutator_lock_) {
if (kUseReadBarrier) {
AssertToSpaceInvariant(ref);
}
}
// ALWAYS_INLINE on this caused a performance regression b/26744236.
static mirror::Object* Mark(mirror::Object* obj) REQUIRES_SHARED(Locks::mutator_lock_);
static constexpr uint32_t WhiteState() {
return white_state_;
}
static constexpr uint32_t GrayState() {
return gray_state_;
}
// fake_address_dependency will be zero which should be bitwise-or'ed with the address of the
// subsequent load to prevent the reordering of the read barrier bit load and the subsequent
// object reference load (from one of `obj`'s fields).
// *fake_address_dependency will be set to 0.
ALWAYS_INLINE static bool IsGray(mirror::Object* obj, uintptr_t* fake_address_dependency)
REQUIRES_SHARED(Locks::mutator_lock_);
// This uses a load-acquire to load the read barrier bit internally to prevent the reordering of
// the read barrier bit load and the subsequent load.
ALWAYS_INLINE static bool IsGray(mirror::Object* obj)
REQUIRES_SHARED(Locks::mutator_lock_);
static bool IsValidReadBarrierState(uint32_t rb_state) {
return rb_state == white_state_ || rb_state == gray_state_;
}
static constexpr uint32_t white_state_ = 0x0; // Not marked.
static constexpr uint32_t gray_state_ = 0x1; // Marked, but not marked through. On mark stack.
static constexpr uint32_t rb_state_mask_ = 0x1; // The low bits for white|gray.
};
} // namespace art
#endif // ART_RUNTIME_READ_BARRIER_H_
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