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* Copyright (C) 2011 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include "array.h"
#include "art_field.h"
#include "art_method.h"
#include "class.h"
#include "dex_file_types.h"
#include "object.h"
#include "object_array.h"
namespace art {
struct DexCacheOffsets;
class DexFile;
class ImageWriter;
union JValue;
class LinearAlloc;
class Thread;
namespace mirror {
class MethodType;
class String;
template <typename T> struct PACKED(8) DexCachePair {
GcRoot<T> object;
uint32_t index;
// The array is initially [ {0,0}, {0,0}, {0,0} ... ]
// We maintain the invariant that once a dex cache entry is populated,
// the pointer is always non-0
// Any given entry would thus be:
// {non-0, non-0} OR {0,0}
// It's generally sufficiently enough then to check if the
// lookup index matches the stored index (for a >0 lookup index)
// because if it's true the pointer is also non-null.
// For the 0th entry which is a special case, the value is either
// {0,0} (initial state) or {non-0, 0} which indicates
// that a valid object is stored at that index for a dex section id of 0.
// As an optimization, we want to avoid branching on the object pointer since
// it's always non-null if the id branch succeeds (except for the 0th id).
// Set the initial state for the 0th entry to be {0,1} which is guaranteed to fail
// the lookup id == stored id branch.
DexCachePair(T* object, uint32_t index)
: object(object),
index(index) {}
DexCachePair() = default;
DexCachePair(const DexCachePair<T>&) = default;
DexCachePair& operator=(const DexCachePair<T>&) = default;
static void Initialize(std::atomic<DexCachePair<T>>* dex_cache) {
DexCachePair<T> first_elem;
first_elem.object = GcRoot<T>(nullptr);
first_elem.index = InvalidIndexForSlot(0);
dex_cache[0].store(first_elem, std::memory_order_relaxed);
static GcRoot<T> Lookup(std::atomic<DexCachePair<T>>* dex_cache,
uint32_t idx,
uint32_t cache_size) {
DCHECK_NE(cache_size, 0u);
DexCachePair<T> element = dex_cache[idx % cache_size].load(std::memory_order_relaxed);
if (idx != element.index) {
return GcRoot<T>(nullptr);
return element.object;
static void Assign(std::atomic<DexCachePair<T>>* dex_cache,
uint32_t idx,
T* object,
uint32_t cache_size) {
DCHECK_LT(idx % cache_size, cache_size);
dex_cache[idx % cache_size].store(
DexCachePair<T>(object, idx), std::memory_order_relaxed);
static uint32_t InvalidIndexForSlot(uint32_t slot) {
// Since the cache size is a power of two, 0 will always map to slot 0.
// Use 1 for slot 0 and 0 for all other slots.
return (slot == 0) ? 1u : 0u;
using StringDexCachePair = DexCachePair<mirror::String>;
using StringDexCacheType = std::atomic<StringDexCachePair>;
using MethodTypeDexCachePair = DexCachePair<mirror::MethodType>;
using MethodTypeDexCacheType = std::atomic<MethodTypeDexCachePair>;
// C++ mirror of java.lang.DexCache.
class MANAGED DexCache FINAL : public Object {
// Size of java.lang.DexCache.class.
static uint32_t ClassSize(PointerSize pointer_size);
// Size of string dex cache. Needs to be a power of 2 for entrypoint assumptions to hold.
static constexpr size_t kDexCacheStringCacheSize = 1024;
"String dex cache size is not a power of 2.");
// Size of method type dex cache. Needs to be a power of 2 for entrypoint assumptions
// to hold.
static constexpr size_t kDexCacheMethodTypeCacheSize = 1024;
"MethodType dex cache size is not a power of 2.");
static constexpr size_t StaticStringSize() {
return kDexCacheStringCacheSize;
static constexpr size_t StaticMethodTypeSize() {
return kDexCacheMethodTypeCacheSize;
// Size of an instance of java.lang.DexCache not including referenced values.
static constexpr uint32_t InstanceSize() {
return sizeof(DexCache);
static void InitializeDexCache(Thread* self,
ObjPtr<mirror::DexCache> dex_cache,
ObjPtr<mirror::String> location,
const DexFile* dex_file,
LinearAlloc* linear_alloc,
PointerSize image_pointer_size)
void Fixup(ArtMethod* trampoline, PointerSize pointer_size)
template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier, typename Visitor>
void FixupStrings(StringDexCacheType* dest, const Visitor& visitor)
template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier, typename Visitor>
void FixupResolvedTypes(GcRoot<mirror::Class>* dest, const Visitor& visitor)
template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier, typename Visitor>
void FixupResolvedMethodTypes(MethodTypeDexCacheType* dest, const Visitor& visitor)
String* GetLocation() REQUIRES_SHARED(Locks::mutator_lock_) {
return GetFieldObject<String>(OFFSET_OF_OBJECT_MEMBER(DexCache, location_));
static MemberOffset DexOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, dex_);
static MemberOffset StringsOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, strings_);
static MemberOffset ResolvedTypesOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, resolved_types_);
static MemberOffset ResolvedFieldsOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, resolved_fields_);
static MemberOffset ResolvedMethodsOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, resolved_methods_);
static MemberOffset ResolvedMethodTypesOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, resolved_method_types_);
static MemberOffset NumStringsOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, num_strings_);
static MemberOffset NumResolvedTypesOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, num_resolved_types_);
static MemberOffset NumResolvedFieldsOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, num_resolved_fields_);
static MemberOffset NumResolvedMethodsOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, num_resolved_methods_);
static MemberOffset NumResolvedMethodTypesOffset() {
return OFFSET_OF_OBJECT_MEMBER(DexCache, num_resolved_method_types_);
mirror::String* GetResolvedString(dex::StringIndex string_idx) ALWAYS_INLINE
void SetResolvedString(dex::StringIndex string_idx, ObjPtr<mirror::String> resolved) ALWAYS_INLINE
// Clear a string for a string_idx, used to undo string intern transactions to make sure
// the string isn't kept live.
void ClearString(dex::StringIndex string_idx) REQUIRES_SHARED(Locks::mutator_lock_);
Class* GetResolvedType(dex::TypeIndex type_idx) REQUIRES_SHARED(Locks::mutator_lock_);
void SetResolvedType(dex::TypeIndex type_idx, ObjPtr<Class> resolved)
ALWAYS_INLINE ArtMethod* GetResolvedMethod(uint32_t method_idx, PointerSize ptr_size)
ALWAYS_INLINE void SetResolvedMethod(uint32_t method_idx,
ArtMethod* resolved,
PointerSize ptr_size)
// Pointer sized variant, used for patching.
ALWAYS_INLINE ArtField* GetResolvedField(uint32_t idx, PointerSize ptr_size)
// Pointer sized variant, used for patching.
ALWAYS_INLINE void SetResolvedField(uint32_t idx, ArtField* field, PointerSize ptr_size)
MethodType* GetResolvedMethodType(uint32_t proto_idx) REQUIRES_SHARED(Locks::mutator_lock_);
void SetResolvedMethodType(uint32_t proto_idx, MethodType* resolved) REQUIRES_SHARED(Locks::mutator_lock_);
StringDexCacheType* GetStrings() ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
return GetFieldPtr64<StringDexCacheType*>(StringsOffset());
void SetStrings(StringDexCacheType* strings) ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
SetFieldPtr<false>(StringsOffset(), strings);
GcRoot<Class>* GetResolvedTypes() ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
return GetFieldPtr<GcRoot<Class>*>(ResolvedTypesOffset());
void SetResolvedTypes(GcRoot<Class>* resolved_types)
REQUIRES_SHARED(Locks::mutator_lock_) {
SetFieldPtr<false>(ResolvedTypesOffset(), resolved_types);
ArtMethod** GetResolvedMethods() ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
return GetFieldPtr<ArtMethod**>(ResolvedMethodsOffset());
void SetResolvedMethods(ArtMethod** resolved_methods)
REQUIRES_SHARED(Locks::mutator_lock_) {
SetFieldPtr<false>(ResolvedMethodsOffset(), resolved_methods);
ArtField** GetResolvedFields() ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
return GetFieldPtr<ArtField**>(ResolvedFieldsOffset());
void SetResolvedFields(ArtField** resolved_fields)
REQUIRES_SHARED(Locks::mutator_lock_) {
SetFieldPtr<false>(ResolvedFieldsOffset(), resolved_fields);
MethodTypeDexCacheType* GetResolvedMethodTypes()
return GetFieldPtr64<MethodTypeDexCacheType*>(ResolvedMethodTypesOffset());
void SetResolvedMethodTypes(MethodTypeDexCacheType* resolved_method_types)
REQUIRES_SHARED(Locks::mutator_lock_) {
SetFieldPtr<false>(ResolvedMethodTypesOffset(), resolved_method_types);
size_t NumStrings() REQUIRES_SHARED(Locks::mutator_lock_) {
return GetField32(NumStringsOffset());
size_t NumResolvedTypes() REQUIRES_SHARED(Locks::mutator_lock_) {
return GetField32(NumResolvedTypesOffset());
size_t NumResolvedMethods() REQUIRES_SHARED(Locks::mutator_lock_) {
return GetField32(NumResolvedMethodsOffset());
size_t NumResolvedFields() REQUIRES_SHARED(Locks::mutator_lock_) {
return GetField32(NumResolvedFieldsOffset());
size_t NumResolvedMethodTypes() REQUIRES_SHARED(Locks::mutator_lock_) {
return GetField32(NumResolvedMethodTypesOffset());
const DexFile* GetDexFile() ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
return GetFieldPtr<const DexFile*>(OFFSET_OF_OBJECT_MEMBER(DexCache, dex_file_));
void SetDexFile(const DexFile* dex_file) REQUIRES_SHARED(Locks::mutator_lock_) {
SetFieldPtr<false>(OFFSET_OF_OBJECT_MEMBER(DexCache, dex_file_), dex_file);
void SetLocation(ObjPtr<mirror::String> location) REQUIRES_SHARED(Locks::mutator_lock_);
// NOTE: Get/SetElementPtrSize() are intended for working with ArtMethod** and ArtField**
// provided by GetResolvedMethods/Fields() and ArtMethod::GetDexCacheResolvedMethods(),
// so they need to be public.
template <typename PtrType>
static PtrType GetElementPtrSize(PtrType* ptr_array, size_t idx, PointerSize ptr_size);
template <typename PtrType>
static void SetElementPtrSize(PtrType* ptr_array, size_t idx, PtrType ptr, PointerSize ptr_size);
void Init(const DexFile* dex_file,
ObjPtr<String> location,
StringDexCacheType* strings,
uint32_t num_strings,
GcRoot<Class>* resolved_types,
uint32_t num_resolved_types,
ArtMethod** resolved_methods,
uint32_t num_resolved_methods,
ArtField** resolved_fields,
uint32_t num_resolved_fields,
MethodTypeDexCacheType* resolved_methodtypes,
uint32_t num_resolved_methodtypes,
PointerSize pointer_size)
// Visit instance fields of the dex cache as well as its associated arrays.
template <bool kVisitNativeRoots,
VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags,
ReadBarrierOption kReadBarrierOption = kWithReadBarrier,
typename Visitor>
void VisitReferences(ObjPtr<mirror::Class> klass, const Visitor& visitor)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(Locks::heap_bitmap_lock_);
HeapReference<Object> dex_;
HeapReference<String> location_;
uint64_t dex_file_; // const DexFile*
uint64_t resolved_fields_; // ArtField*, array with num_resolved_fields_ elements.
uint64_t resolved_method_types_; // std::atomic<MethodTypeDexCachePair>* array with
// num_resolved_method_types_ elements.
uint64_t resolved_methods_; // ArtMethod*, array with num_resolved_methods_ elements.
uint64_t resolved_types_; // GcRoot<Class>*, array with num_resolved_types_ elements.
uint64_t strings_; // std::atomic<StringDexCachePair>*, array with num_strings_
// elements.
uint32_t num_resolved_fields_; // Number of elements in the resolved_fields_ array.
uint32_t num_resolved_method_types_; // Number of elements in the resolved_method_types_ array.
uint32_t num_resolved_methods_; // Number of elements in the resolved_methods_ array.
uint32_t num_resolved_types_; // Number of elements in the resolved_types_ array.
uint32_t num_strings_; // Number of elements in the strings_ array.
friend struct art::DexCacheOffsets; // for verifying offset information
friend class Object; // For VisitReferences
} // namespace mirror
} // namespace art