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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#ifndef RUNTIME_VM_CLASS_TABLE_H_
#define RUNTIME_VM_CLASS_TABLE_H_
#include <memory>
#include "platform/assert.h"
#include "platform/atomic.h"
#include "platform/utils.h"
#include "vm/bitfield.h"
#include "vm/class_id.h"
#include "vm/flags.h"
#include "vm/globals.h"
#include "vm/tagged_pointer.h"
namespace dart {
class Class;
class ClassTable;
class Isolate;
class IsolateGroup;
class IsolateGroupReloadContext;
class IsolateReloadContext;
class JSONArray;
class JSONObject;
class JSONStream;
template <typename T>
class MallocGrowableArray;
class ObjectPointerVisitor;
// Wraps a 64-bit integer to represent the bitmap of unboxed fields
// stored in the shared class table.
class UnboxedFieldBitmap {
public:
UnboxedFieldBitmap() : bitmap_(0) {}
explicit UnboxedFieldBitmap(uint64_t bitmap) : bitmap_(bitmap) {}
UnboxedFieldBitmap(const UnboxedFieldBitmap&) = default;
UnboxedFieldBitmap& operator=(const UnboxedFieldBitmap&) = default;
DART_FORCE_INLINE bool Get(intptr_t position) const {
if (position >= Length()) return false;
return Utils::TestBit(bitmap_, position);
}
DART_FORCE_INLINE void Set(intptr_t position) {
ASSERT(position < Length());
bitmap_ |= Utils::Bit<decltype(bitmap_)>(position);
}
DART_FORCE_INLINE uint64_t Value() const { return bitmap_; }
DART_FORCE_INLINE bool IsEmpty() const { return bitmap_ == 0; }
DART_FORCE_INLINE void Reset() { bitmap_ = 0; }
DART_FORCE_INLINE static constexpr intptr_t Length() {
return sizeof(decltype(bitmap_)) * kBitsPerByte;
}
private:
uint64_t bitmap_;
};
// Registry of all known classes and their sizes.
//
// The GC will only need the information in this shared class table to scan
// object pointers.
class SharedClassTable {
public:
SharedClassTable();
~SharedClassTable();
// Thread-safe.
intptr_t SizeAt(intptr_t index) const {
ASSERT(IsValidIndex(index));
return table_.load()[index];
}
bool HasValidClassAt(intptr_t index) const {
ASSERT(IsValidIndex(index));
ASSERT(table_.load()[index] >= 0);
return table_.load()[index] != 0;
}
void SetSizeAt(intptr_t index, intptr_t size) {
ASSERT(IsValidIndex(index));
// Ensure we never change size for a given cid from one non-zero size to
// another non-zero size.
intptr_t old_size = 0;
if (!table_.load()[index].compare_exchange_strong(old_size, size)) {
RELEASE_ASSERT(old_size == size);
}
}
bool IsValidIndex(intptr_t index) const { return index > 0 && index < top_; }
intptr_t NumCids() const { return top_; }
intptr_t Capacity() const { return capacity_; }
UnboxedFieldBitmap GetUnboxedFieldsMapAt(intptr_t index) const {
ASSERT(IsValidIndex(index));
return FLAG_precompiled_mode ? unboxed_fields_map_[index]
: UnboxedFieldBitmap();
}
void SetUnboxedFieldsMapAt(intptr_t index,
UnboxedFieldBitmap unboxed_fields_map) {
ASSERT(IsValidIndex(index));
ASSERT(unboxed_fields_map_[index].IsEmpty());
unboxed_fields_map_[index] = unboxed_fields_map;
}
// Used to drop recently added classes.
void SetNumCids(intptr_t num_cids) {
ASSERT(num_cids <= top_);
top_ = num_cids;
}
#if !defined(PRODUCT)
void SetTraceAllocationFor(intptr_t cid, bool trace) {
ASSERT(cid > 0);
ASSERT(cid < top_);
trace_allocation_table_.load()[cid] = trace ? 1 : 0;
}
bool TraceAllocationFor(intptr_t cid);
#endif // !defined(PRODUCT)
void CopyBeforeHotReload(intptr_t** copy, intptr_t* copy_num_cids) {
// The [IsolateGroupReloadContext] will need to maintain a copy of the old
// class table until instances have been morphed.
const intptr_t num_cids = NumCids();
const intptr_t bytes = sizeof(intptr_t) * num_cids;
auto size_table = static_cast<intptr_t*>(malloc(bytes));
auto table = table_.load();
for (intptr_t i = 0; i < num_cids; i++) {
// Don't use memmove, which changes this from a relaxed atomic operation
// to a non-atomic operation.
size_table[i] = table[i];
}
*copy_num_cids = num_cids;
*copy = size_table;
}
void ResetBeforeHotReload() {
// The [IsolateReloadContext] is now source-of-truth for GC.
auto table = table_.load();
for (intptr_t i = 0; i < top_; i++) {
// Don't use memset, which changes this from a relaxed atomic operation
// to a non-atomic operation.
table[i] = 0;
}
}
void ResetAfterHotReload(intptr_t* old_table,
intptr_t num_old_cids,
bool is_rollback) {
// The [IsolateReloadContext] is no longer source-of-truth for GC after we
// return, so we restore size information for all classes.
if (is_rollback) {
SetNumCids(num_old_cids);
auto table = table_.load();
for (intptr_t i = 0; i < num_old_cids; i++) {
// Don't use memmove, which changes this from a relaxed atomic operation
// to a non-atomic operation.
table[i] = old_table[i];
}
}
// Can't free this table immediately as another thread (e.g., concurrent
// marker or sweeper) may be between loading the table pointer and loading
// the table element. The table will be freed at the next major GC or
// isolate shutdown.
AddOldTable(old_table);
}
// Deallocates table copies. Do not call during concurrent access to table.
void FreeOldTables();
// Deallocates bitmap copies. Do not call during concurrent access to table.
void FreeOldUnboxedFieldsMaps();
#if !defined(DART_PRECOMPILED_RUNTIME)
bool IsReloading() const { return reload_context_ != nullptr; }
IsolateGroupReloadContext* reload_context() { return reload_context_; }
#endif // !defined(DART_PRECOMPILED_RUNTIME)
// Returns the newly allocated cid.
//
// [index] is kIllegalCid or a predefined cid.
intptr_t Register(intptr_t index, intptr_t size);
void AllocateIndex(intptr_t index);
void Unregister(intptr_t index);
void Remap(intptr_t* old_to_new_cids);
// Used by the generated code.
#ifndef PRODUCT
static intptr_t class_heap_stats_table_offset() {
return OFFSET_OF(SharedClassTable, trace_allocation_table_);
}
#endif
// Used by the generated code.
static intptr_t ClassOffsetFor(intptr_t cid);
static const int kInitialCapacity = 512;
static const int kCapacityIncrement = 256;
private:
friend class ClassTable;
friend class GCMarker;
friend class MarkingWeakVisitor;
friend class Scavenger;
friend class ScavengerWeakVisitor;
static bool ShouldUpdateSizeForClassId(intptr_t cid);
#ifndef PRODUCT
// Copy-on-write is used for trace_allocation_table_, with old copies stored
// in old_tables_.
AcqRelAtomic<uint8_t*> trace_allocation_table_ = {nullptr};
#endif // !PRODUCT
void AddOldTable(intptr_t* old_table);
void Grow(intptr_t new_capacity);
intptr_t top_;
intptr_t capacity_;
// Copy-on-write is used for table_, with old copies stored in old_tables_.
// Maps the cid to the instance size.
AcqRelAtomic<RelaxedAtomic<intptr_t>*> table_ = {nullptr};
MallocGrowableArray<void*>* old_tables_;
IsolateGroupReloadContext* reload_context_ = nullptr;
// Stores a 64-bit bitmap for each class. There is one bit for each word in an
// instance of the class. A 0 bit indicates that the word contains a pointer
// the GC has to scan, a 1 indicates that the word is part of e.g. an unboxed
// double and does not need to be scanned. (see Class::Calculate...() where
// the bitmap is constructed)
UnboxedFieldBitmap* unboxed_fields_map_ = nullptr;
DISALLOW_COPY_AND_ASSIGN(SharedClassTable);
};
class ClassTable {
public:
explicit ClassTable(SharedClassTable* shared_class_table_);
~ClassTable();
SharedClassTable* shared_class_table() const { return shared_class_table_; }
void CopyBeforeHotReload(ClassPtr** copy,
ClassPtr** tlc_copy,
intptr_t* copy_num_cids,
intptr_t* copy_num_tlc_cids) {
// The [IsolateReloadContext] will need to maintain a copy of the old class
// table until instances have been morphed.
const intptr_t num_cids = NumCids();
const intptr_t num_tlc_cids = NumTopLevelCids();
auto class_table =
static_cast<ClassPtr*>(malloc(sizeof(ClassPtr) * num_cids));
auto tlc_class_table =
static_cast<ClassPtr*>(malloc(sizeof(ClassPtr) * num_tlc_cids));
// Don't use memmove, which changes this from a relaxed atomic operation
// to a non-atomic operation.
auto table = table_.load();
for (intptr_t i = 0; i < num_cids; i++) {
class_table[i] = table[i];
}
auto tlc_table = tlc_table_.load();
for (intptr_t i = 0; i < num_tlc_cids; i++) {
tlc_class_table[i] = tlc_table[i];
}
*copy = class_table;
*tlc_copy = tlc_class_table;
*copy_num_cids = num_cids;
*copy_num_tlc_cids = num_tlc_cids;
}
void ResetBeforeHotReload() {
// We cannot clear out the class pointers, because a hot-reload
// contains only a diff: If e.g. a class included in the hot-reload has a
// super class not included in the diff, it will look up in this class table
// to find the super class (e.g. `cls.SuperClass` will cause us to come
// here).
}
void ResetAfterHotReload(ClassPtr* old_table,
ClassPtr* old_tlc_table,
intptr_t num_old_cids,
intptr_t num_old_tlc_cids,
bool is_rollback) {
// The [IsolateReloadContext] is no longer source-of-truth for GC after we
// return, so we restore size information for all classes.
if (is_rollback) {
SetNumCids(num_old_cids, num_old_tlc_cids);
// Don't use memmove, which changes this from a relaxed atomic operation
// to a non-atomic operation.
auto table = table_.load();
for (intptr_t i = 0; i < num_old_cids; i++) {
table[i] = old_table[i];
}
auto tlc_table = tlc_table_.load();
for (intptr_t i = 0; i < num_old_tlc_cids; i++) {
tlc_table[i] = old_tlc_table[i];
}
} else {
CopySizesFromClassObjects();
}
// Can't free these tables immediately as another thread (e.g., concurrent
// marker or sweeper) may be between loading the table pointer and loading
// the table element. The table will be freed at the next major GC or
// isolate shutdown.
AddOldTable(old_table);
AddOldTable(old_tlc_table);
}
// Thread-safe.
ClassPtr At(intptr_t cid) const {
ASSERT(IsValidIndex(cid));
if (IsTopLevelCid(cid)) {
return tlc_table_.load()[IndexFromTopLevelCid(cid)];
}
return table_.load()[cid];
}
intptr_t SizeAt(intptr_t index) const {
if (IsTopLevelCid(index)) {
return 0;
}
return shared_class_table_->SizeAt(index);
}
void SetAt(intptr_t index, ClassPtr raw_cls);
bool IsValidIndex(intptr_t cid) const {
if (IsTopLevelCid(cid)) {
return IndexFromTopLevelCid(cid) < tlc_top_;
}
return shared_class_table_->IsValidIndex(cid);
}
bool HasValidClassAt(intptr_t cid) const {
ASSERT(IsValidIndex(cid));
if (IsTopLevelCid(cid)) {
return tlc_table_.load()[IndexFromTopLevelCid(cid)] != nullptr;
}
return table_.load()[cid] != nullptr;
}
intptr_t NumCids() const { return shared_class_table_->NumCids(); }
intptr_t NumTopLevelCids() const { return tlc_top_; }
intptr_t Capacity() const { return shared_class_table_->Capacity(); }
void Register(const Class& cls);
void RegisterTopLevel(const Class& cls);
void AllocateIndex(intptr_t index);
void Unregister(intptr_t index);
void UnregisterTopLevel(intptr_t index);
void Remap(intptr_t* old_to_new_cids);
void VisitObjectPointers(ObjectPointerVisitor* visitor);
// If a snapshot reader has populated the class table then the
// sizes in the class table are not correct. Iterates through the
// table, updating the sizes.
void CopySizesFromClassObjects();
void Validate();
void Print();
#ifndef PRODUCT
// Describes layout of heap stats for code generation. See offset_extractor.cc
struct ArrayTraits {
static intptr_t elements_start_offset() { return 0; }
static constexpr intptr_t kElementSize = sizeof(uint8_t);
};
#endif
#ifndef PRODUCT
void AllocationProfilePrintJSON(JSONStream* stream, bool internal);
void PrintToJSONObject(JSONObject* object);
#endif // !PRODUCT
// Deallocates table copies. Do not call during concurrent access to table.
void FreeOldTables();
static bool IsTopLevelCid(intptr_t cid) { return cid >= kTopLevelCidOffset; }
static intptr_t IndexFromTopLevelCid(intptr_t cid) {
ASSERT(IsTopLevelCid(cid));
return cid - kTopLevelCidOffset;
}
static intptr_t CidFromTopLevelIndex(intptr_t index) {
return kTopLevelCidOffset + index;
}
private:
friend class GCMarker;
friend class MarkingWeakVisitor;
friend class Scavenger;
friend class ScavengerWeakVisitor;
friend class Dart;
friend Isolate* CreateWithinExistingIsolateGroup(IsolateGroup* group,
const char* name,
char** error);
friend class Isolate; // for table()
static const int kInitialCapacity = SharedClassTable::kInitialCapacity;
static const int kCapacityIncrement = SharedClassTable::kCapacityIncrement;
static const intptr_t kTopLevelCidOffset = (1 << 16);
void AddOldTable(ClassPtr* old_table);
void AllocateTopLevelIndex(intptr_t index);
void Grow(intptr_t index);
void GrowTopLevel(intptr_t index);
ClassPtr* table() { return table_.load(); }
void set_table(ClassPtr* table);
// Used to drop recently added classes.
void SetNumCids(intptr_t num_cids, intptr_t num_tlc_cids) {
shared_class_table_->SetNumCids(num_cids);
ASSERT(num_cids <= top_);
top_ = num_cids;
ASSERT(num_tlc_cids <= tlc_top_);
tlc_top_ = num_tlc_cids;
}
intptr_t top_;
intptr_t capacity_;
intptr_t tlc_top_;
intptr_t tlc_capacity_;
// Copy-on-write is used for table_, with old copies stored in
// old_class_tables_.
AcqRelAtomic<ClassPtr*> table_;
AcqRelAtomic<ClassPtr*> tlc_table_;
MallocGrowableArray<ClassPtr*>* old_class_tables_;
SharedClassTable* shared_class_table_;
DISALLOW_COPY_AND_ASSIGN(ClassTable);
};
#if !defined(PRODUCT)
DART_FORCE_INLINE bool SharedClassTable::TraceAllocationFor(intptr_t cid) {
ASSERT(cid > 0);
if (ClassTable::IsTopLevelCid(cid)) {
return false;
}
ASSERT(cid < top_);
return trace_allocation_table_.load()[cid] != 0;
}
#endif // !defined(PRODUCT)
} // namespace dart
#endif // RUNTIME_VM_CLASS_TABLE_H_