src/objects/code.h

// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_OBJECTS_CODE_H_
#define V8_OBJECTS_CODE_H_

#include "src/contexts.h"
#include "src/handler-table.h"
#include "src/objects.h"
#include "src/objects/fixed-array.h"
#include "src/objects/heap-object.h"

// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"

namespace v8 {
namespace internal {

class ByteArray;
class BytecodeArray;
class CodeDataContainer;
class MaybeObject;

namespace interpreter {
class Register;
}

// Code describes objects with on-the-fly generated machine code.
class Code : public HeapObjectPtr {
 public:
  NEVER_READ_ONLY_SPACE
  // Opaque data type for encapsulating code flags like kind, inline
  // cache state, and arguments count.
  typedef uint32_t Flags;

#define CODE_KIND_LIST(V)   \
  V(OPTIMIZED_FUNCTION)     \
  V(BYTECODE_HANDLER)       \
  V(STUB)                   \
  V(BUILTIN)                \
  V(REGEXP)                 \
  V(WASM_FUNCTION)          \
  V(WASM_TO_JS_FUNCTION)    \
  V(JS_TO_WASM_FUNCTION)    \
  V(WASM_INTERPRETER_ENTRY) \
  V(C_WASM_ENTRY)

  enum Kind {
#define DEFINE_CODE_KIND_ENUM(name) name,
    CODE_KIND_LIST(DEFINE_CODE_KIND_ENUM)
#undef DEFINE_CODE_KIND_ENUM
        NUMBER_OF_KINDS
  };

  static const char* Kind2String(Kind kind);

#ifdef ENABLE_DISASSEMBLER
  const char* GetName(Isolate* isolate) const;
  void Disassemble(const char* name, std::ostream& os,
                   Address current_pc = kNullAddress);
#endif

  // [instruction_size]: Size of the native instructions, including embedded
  // data such as the safepoints table.
  inline int raw_instruction_size() const;
  inline void set_raw_instruction_size(int value);

  // Returns the size of the native instructions, including embedded
  // data such as the safepoints table. For off-heap code objects
  // this may from instruction_size in that this will return the size of the
  // off-heap instruction stream rather than the on-heap trampoline located
  // at instruction_start.
  inline int InstructionSize() const;
  int OffHeapInstructionSize() const;

  // [relocation_info]: Code relocation information
  DECL_ACCESSORS(relocation_info, ByteArray)

  // This function should be called only from GC.
  void ClearEmbeddedObjects(Heap* heap);

  // [deoptimization_data]: Array containing data for deopt.
  DECL_ACCESSORS(deoptimization_data, FixedArray)

  // [source_position_table]: ByteArray for the source positions table or
  // SourcePositionTableWithFrameCache.
  DECL_ACCESSORS(source_position_table, Object)
  inline ByteArray* SourcePositionTable() const;

  // [code_data_container]: A container indirection for all mutable fields.
  DECL_ACCESSORS(code_data_container, CodeDataContainer)

  // [stub_key]: The major/minor key of a code stub.
  inline uint32_t stub_key() const;
  inline void set_stub_key(uint32_t key);

  // [next_code_link]: Link for lists of optimized or deoptimized code.
  // Note that this field is stored in the {CodeDataContainer} to be mutable.
  inline Object* next_code_link() const;
  inline void set_next_code_link(Object* value);

  // [constant_pool offset]: Offset of the constant pool.
  // Valid for FLAG_enable_embedded_constant_pool only
  inline int constant_pool_offset() const;
  inline void set_constant_pool_offset(int offset);

  // Unchecked accessors to be used during GC.
  inline ByteArray* unchecked_relocation_info() const;

  inline int relocation_size() const;

  // [kind]: Access to specific code kind.
  inline Kind kind() const;

  inline bool is_stub() const;
  inline bool is_optimized_code() const;
  inline bool is_wasm_code() const;

  // Testers for interpreter builtins.
  inline bool is_interpreter_trampoline_builtin() const;

  // Tells whether the code checks the optimization marker in the function's
  // feedback vector.
  inline bool checks_optimization_marker() const;

  // Tells whether the outgoing parameters of this code are tagged pointers.
  inline bool has_tagged_params() const;

  // [is_turbofanned]: For kind STUB or OPTIMIZED_FUNCTION, tells whether the
  // code object was generated by the TurboFan optimizing compiler.
  inline bool is_turbofanned() const;

  // [can_have_weak_objects]: For kind OPTIMIZED_FUNCTION, tells whether the
  // embedded objects in code should be treated weakly.
  inline bool can_have_weak_objects() const;
  inline void set_can_have_weak_objects(bool value);

  // [is_construct_stub]: For kind BUILTIN, tells whether the code object
  // represents a hand-written construct stub
  // (e.g., NumberConstructor_ConstructStub).
  inline bool is_construct_stub() const;
  inline void set_is_construct_stub(bool value);

  // [builtin_index]: For builtins, tells which builtin index the code object
  // has. The builtin index is a non-negative integer for builtins, and -1
  // otherwise.
  inline int builtin_index() const;
  inline void set_builtin_index(int id);
  inline bool is_builtin() const;

  inline bool has_safepoint_info() const;

  // [stack_slots]: If {has_safepoint_info()}, the number of stack slots
  // reserved in the code prologue.
  inline int stack_slots() const;

  // [safepoint_table_offset]: If {has_safepoint_info()}, the offset in the
  // instruction stream where the safepoint table starts.
  inline int safepoint_table_offset() const;
  inline void set_safepoint_table_offset(int offset);

  // [handler_table_offset]: The offset in the instruction stream where the
  // exception handler table starts.
  inline int handler_table_offset() const;
  inline void set_handler_table_offset(int offset);

  // [marked_for_deoptimization]: For kind OPTIMIZED_FUNCTION tells whether
  // the code is going to be deoptimized.
  inline bool marked_for_deoptimization() const;
  inline void set_marked_for_deoptimization(bool flag);

  // [embedded_objects_cleared]: For kind OPTIMIZED_FUNCTION tells whether
  // the embedded objects in the code marked for deoptimization were cleared.
  // Note that embedded_objects_cleared() implies marked_for_deoptimization().
  inline bool embedded_objects_cleared() const;
  inline void set_embedded_objects_cleared(bool flag);

  // [deopt_already_counted]: For kind OPTIMIZED_FUNCTION tells whether
  // the code was already deoptimized.
  inline bool deopt_already_counted() const;
  inline void set_deopt_already_counted(bool flag);

  // [is_promise_rejection]: For kind BUILTIN tells whether the
  // exception thrown by the code will lead to promise rejection or
  // uncaught if both this and is_exception_caught is set.
  // Use GetBuiltinCatchPrediction to access this.
  inline void set_is_promise_rejection(bool flag);

  // [is_exception_caught]: For kind BUILTIN tells whether the
  // exception thrown by the code will be caught internally or
  // uncaught if both this and is_promise_rejection is set.
  // Use GetBuiltinCatchPrediction to access this.
  inline void set_is_exception_caught(bool flag);

  // [is_off_heap_trampoline]: For kind BUILTIN tells whether
  // this is a trampoline to an off-heap builtin.
  inline bool is_off_heap_trampoline() const;

  // [constant_pool]: The constant pool for this function.
  inline Address constant_pool() const;

  // Get the safepoint entry for the given pc.
  SafepointEntry GetSafepointEntry(Address pc);

  // The entire code object including its header is copied verbatim to the
  // snapshot so that it can be written in one, fast, memcpy during
  // deserialization. The deserializer will overwrite some pointers, rather
  // like a runtime linker, but the random allocation addresses used in the
  // mksnapshot process would still be present in the unlinked snapshot data,
  // which would make snapshot production non-reproducible. This method wipes
  // out the to-be-overwritten header data for reproducible snapshots.
  inline void WipeOutHeader();

  // Clear uninitialized padding space. This ensures that the snapshot content
  // is deterministic.
  inline void clear_padding();
  // Initialize the flags field. Similar to clear_padding above this ensure that
  // the snapshot content is deterministic.
  inline void initialize_flags(Kind kind, bool has_unwinding_info,
                               bool is_turbofanned, int stack_slots,
                               bool is_off_heap_trampoline);

  // Convert a target address into a code object.
  static inline Code GetCodeFromTargetAddress(Address address);

  // Convert an entry address into an object.
  static inline Object* GetObjectFromEntryAddress(Address location_of_address);

  // Convert a code entry into an object.
  static inline Object* GetObjectFromCodeEntry(Address code_entry);

  // Returns the address of the first instruction.
  inline Address raw_instruction_start() const;

  // Returns the address of the first instruction. For off-heap code objects
  // this differs from instruction_start (which would point to the off-heap
  // trampoline instead).
  inline Address InstructionStart() const;
  Address OffHeapInstructionStart() const;

  // Returns the address right after the last instruction.
  inline Address raw_instruction_end() const;

  // Returns the address right after the last instruction. For off-heap code
  // objects this differs from instruction_end (which would point to the
  // off-heap trampoline instead).
  inline Address InstructionEnd() const;
  Address OffHeapInstructionEnd() const;

  // Returns the size of the instructions, padding, relocation and unwinding
  // information.
  inline int body_size() const;

  // Returns the size of code and its metadata. This includes the size of code
  // relocation information, deoptimization data and handler table.
  inline int SizeIncludingMetadata() const;

  // Returns the address of the first relocation info (read backwards!).
  inline byte* relocation_start() const;

  // Returns the address right after the relocation info (read backwards!).
  inline byte* relocation_end() const;

  // [has_unwinding_info]: Whether this code object has unwinding information.
  // If it doesn't, unwinding_information_start() will point to invalid data.
  //
  // The body of all code objects has the following layout.
  //
  //  +--------------------------+  <-- raw_instruction_start()
  //  |       instructions       |
  //  |           ...            |
  //  +--------------------------+
  //  |      relocation info     |
  //  |           ...            |
  //  +--------------------------+  <-- raw_instruction_end()
  //
  // If has_unwinding_info() is false, raw_instruction_end() points to the first
  // memory location after the end of the code object. Otherwise, the body
  // continues as follows:
  //
  //  +--------------------------+
  //  |    padding to the next   |
  //  |  8-byte aligned address  |
  //  +--------------------------+  <-- raw_instruction_end()
  //  |   [unwinding_info_size]  |
  //  |        as uint64_t       |
  //  +--------------------------+  <-- unwinding_info_start()
  //  |       unwinding info     |
  //  |            ...           |
  //  +--------------------------+  <-- unwinding_info_end()
  //
  // and unwinding_info_end() points to the first memory location after the end
  // of the code object.
  //
  inline bool has_unwinding_info() const;

  // [unwinding_info_size]: Size of the unwinding information.
  inline int unwinding_info_size() const;
  inline void set_unwinding_info_size(int value);

  // Returns the address of the unwinding information, if any.
  inline Address unwinding_info_start() const;

  // Returns the address right after the end of the unwinding information.
  inline Address unwinding_info_end() const;

  // Code entry point.
  inline Address entry() const;

  // Returns true if pc is inside this object's instructions.
  inline bool contains(Address pc);

  // Relocate the code by delta bytes. Called to signal that this code
  // object has been moved by delta bytes.
  void Relocate(intptr_t delta);

  // Migrate code from desc without flushing the instruction cache.
  void CopyFromNoFlush(Heap* heap, const CodeDesc& desc);

  // Copy the RelocInfo portion of |desc| to |dest|. The ByteArray must be
  // exactly the same size as the RelocInfo in |desc|.
  static inline void CopyRelocInfoToByteArray(ByteArray* dest,
                                              const CodeDesc& desc);

  // Flushes the instruction cache for the executable instructions of this code
  // object.
  void FlushICache() const;

  // Returns the object size for a given body (used for allocation).
  static int SizeFor(int body_size) {
    DCHECK_SIZE_TAG_ALIGNED(body_size);
    return RoundUp(kHeaderSize + body_size, kCodeAlignment);
  }

  // Calculate the size of the code object to report for log events. This takes
  // the layout of the code object into account.
  inline int ExecutableSize() const;

  DECL_CAST2(Code)

  // Dispatched behavior.
  inline int CodeSize() const;

  DECL_PRINTER(Code)
  DECL_VERIFIER(Code)

  void PrintDeoptLocation(FILE* out, const char* str, Address pc);
  bool CanDeoptAt(Address pc);

  void SetMarkedForDeoptimization(const char* reason);

  inline HandlerTable::CatchPrediction GetBuiltinCatchPrediction();

#ifdef DEBUG
  enum VerifyMode { kNoContextSpecificPointers, kNoContextRetainingPointers };
  void VerifyEmbeddedObjects(Isolate* isolate,
                             VerifyMode mode = kNoContextRetainingPointers);
#endif  // DEBUG

  bool IsIsolateIndependent(Isolate* isolate);

  inline bool CanContainWeakObjects();

  inline bool IsWeakObject(HeapObject* object);

  static inline bool IsWeakObjectInOptimizedCode(HeapObject* object);

  // Return true if the function is inlined in the code.
  bool Inlines(SharedFunctionInfo* sfi);

  class OptimizedCodeIterator;

  // Layout description.
#define CODE_FIELDS(V)                                                      \
  V(kRelocationInfoOffset, kTaggedSize)                                     \
  V(kDeoptimizationDataOffset, kTaggedSize)                                 \
  V(kSourcePositionTableOffset, kTaggedSize)                                \
  V(kCodeDataContainerOffset, kTaggedSize)                                  \
  /* Data or code not directly visited by GC directly starts here. */       \
  /* The serializer needs to copy bytes starting from here verbatim. */     \
  /* Objects embedded into code is visited via reloc info. */               \
  V(kDataStart, 0)                                                          \
  V(kInstructionSizeOffset, kIntSize)                                       \
  V(kFlagsOffset, kIntSize)                                                 \
  V(kSafepointTableOffsetOffset, kIntSize)                                  \
  V(kHandlerTableOffsetOffset, kIntSize)                                    \
  V(kStubKeyOffset, kIntSize)                                               \
  V(kConstantPoolOffset, FLAG_enable_embedded_constant_pool ? kIntSize : 0) \
  V(kBuiltinIndexOffset, kIntSize)                                          \
  /* Add padding to align the instruction start following right after */    \
  /* the Code object header. */                                             \
  V(kHeaderPaddingStart, CODE_POINTER_PADDING(kHeaderPaddingStart))         \
  V(kHeaderSize, 0)

  DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize, CODE_FIELDS)
#undef CODE_FIELDS

  inline int GetUnwindingInfoSizeOffset() const;

  class BodyDescriptor;

  // Flags layout.  BitField<type, shift, size>.
#define CODE_FLAGS_BIT_FIELDS(V, _)    \
  V(HasUnwindingInfoField, bool, 1, _) \
  V(KindField, Kind, 5, _)             \
  V(IsTurbofannedField, bool, 1, _)    \
  V(StackSlotsField, int, 24, _)       \
  V(IsOffHeapTrampoline, bool, 1, _)
  DEFINE_BIT_FIELDS(CODE_FLAGS_BIT_FIELDS)
#undef CODE_FLAGS_BIT_FIELDS
  static_assert(NUMBER_OF_KINDS <= KindField::kMax, "Code::KindField size");
  static_assert(IsOffHeapTrampoline::kNext <= 32,
                "Code::flags field exhausted");

  // KindSpecificFlags layout (STUB, BUILTIN and OPTIMIZED_FUNCTION)
#define CODE_KIND_SPECIFIC_FLAGS_BIT_FIELDS(V, _) \
  V(MarkedForDeoptimizationField, bool, 1, _)     \
  V(EmbeddedObjectsClearedField, bool, 1, _)      \
  V(DeoptAlreadyCountedField, bool, 1, _)         \
  V(CanHaveWeakObjectsField, bool, 1, _)          \
  V(IsConstructStubField, bool, 1, _)             \
  V(IsPromiseRejectionField, bool, 1, _)          \
  V(IsExceptionCaughtField, bool, 1, _)
  DEFINE_BIT_FIELDS(CODE_KIND_SPECIFIC_FLAGS_BIT_FIELDS)
#undef CODE_KIND_SPECIFIC_FLAGS_BIT_FIELDS
  static_assert(IsExceptionCaughtField::kNext <= 32, "KindSpecificFlags full");

  // The {marked_for_deoptimization} field is accessed from generated code.
  static const int kMarkedForDeoptimizationBit =
      MarkedForDeoptimizationField::kShift;

  static const int kArgumentsBits = 16;
  // Reserve one argument count value as the "don't adapt arguments" sentinel.
  static const int kMaxArguments = (1 << kArgumentsBits) - 2;

 private:
  friend class RelocIterator;

  bool is_promise_rejection() const;
  bool is_exception_caught() const;

  OBJECT_CONSTRUCTORS(Code, HeapObjectPtr);
};

class Code::OptimizedCodeIterator {
 public:
  explicit OptimizedCodeIterator(Isolate* isolate);
  Code Next();

 private:
  Context next_context_;
  Code current_code_;
  Isolate* isolate_;

  DISALLOW_HEAP_ALLOCATION(no_gc);
  DISALLOW_COPY_AND_ASSIGN(OptimizedCodeIterator)
};

// CodeDataContainer is a container for all mutable fields associated with its
// referencing {Code} object. Since {Code} objects reside on write-protected
// pages within the heap, its header fields need to be immutable. There always
// is a 1-to-1 relation between {Code} and {CodeDataContainer}, the referencing
// field {Code::code_data_container} itself is immutable.
class CodeDataContainer : public HeapObject, public NeverReadOnlySpaceObject {
 public:
  DECL_ACCESSORS(next_code_link, Object)
  DECL_INT_ACCESSORS(kind_specific_flags)

  // Clear uninitialized padding space. This ensures that the snapshot content
  // is deterministic.
  inline void clear_padding();

  DECL_CAST(CodeDataContainer)

  // Dispatched behavior.
  DECL_PRINTER(CodeDataContainer)
  DECL_VERIFIER(CodeDataContainer)

// Layout description.
#define CODE_DATA_FIELDS(V)                                 \
  /* Weak pointer fields. */                                \
  V(kPointerFieldsStrongEndOffset, 0)                       \
  V(kNextCodeLinkOffset, kTaggedSize)                       \
  V(kPointerFieldsWeakEndOffset, 0)                         \
  /* Raw data fields. */                                    \
  V(kKindSpecificFlagsOffset, kIntSize)                     \
  V(kUnalignedSize, OBJECT_POINTER_PADDING(kUnalignedSize)) \
  /* Total size. */                                         \
  V(kSize, 0)

  DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize, CODE_DATA_FIELDS)
#undef CODE_DATA_FIELDS

  class BodyDescriptor;

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(CodeDataContainer);
};

class AbstractCode : public HeapObject, public NeverReadOnlySpaceObject {
 public:
  // All code kinds and INTERPRETED_FUNCTION.
  enum Kind {
#define DEFINE_CODE_KIND_ENUM(name) name,
    CODE_KIND_LIST(DEFINE_CODE_KIND_ENUM)
#undef DEFINE_CODE_KIND_ENUM
        INTERPRETED_FUNCTION,
    NUMBER_OF_KINDS
  };

  static const char* Kind2String(Kind kind);

  int SourcePosition(int offset);
  int SourceStatementPosition(int offset);

  // Returns the address of the first instruction.
  inline Address raw_instruction_start();

  // Returns the address of the first instruction. For off-heap code objects
  // this differs from instruction_start (which would point to the off-heap
  // trampoline instead).
  inline Address InstructionStart();

  // Returns the address right after the last instruction.
  inline Address raw_instruction_end();

  // Returns the address right after the last instruction. For off-heap code
  // objects this differs from instruction_end (which would point to the
  // off-heap trampoline instead).
  inline Address InstructionEnd();

  // Returns the size of the code instructions.
  inline int raw_instruction_size();

  // Returns the size of the native instructions, including embedded
  // data such as the safepoints table. For off-heap code objects
  // this may from instruction_size in that this will return the size of the
  // off-heap instruction stream rather than the on-heap trampoline located
  // at instruction_start.
  inline int InstructionSize();

  // Return the source position table.
  inline ByteArray* source_position_table();

  inline Object* stack_frame_cache();
  static void SetStackFrameCache(Handle<AbstractCode> abstract_code,
                                 Handle<SimpleNumberDictionary> cache);
  void DropStackFrameCache();

  // Returns the size of instructions and the metadata.
  inline int SizeIncludingMetadata();

  // Returns true if pc is inside this object's instructions.
  inline bool contains(Address pc);

  // Returns the AbstractCode::Kind of the code.
  inline Kind kind();

  // Calculate the size of the code object to report for log events. This takes
  // the layout of the code object into account.
  inline int ExecutableSize();

  DECL_CAST(AbstractCode)
  inline Code GetCode();
  inline BytecodeArray* GetBytecodeArray();

  // Max loop nesting marker used to postpose OSR. We don't take loop
  // nesting that is deeper than 5 levels into account.
  static const int kMaxLoopNestingMarker = 6;
};

// Dependent code is a singly linked list of weak fixed arrays. Each array
// contains weak pointers to code objects for one dependent group. The suffix of
// the array can be filled with the undefined value if the number of codes is
// less than the length of the array.
//
// +------+-----------------+--------+--------+-----+--------+-----------+-----+
// | next | count & group 1 | code 1 | code 2 | ... | code n | undefined | ... |
// +------+-----------------+--------+--------+-----+--------+-----------+-----+
//    |
//    V
// +------+-----------------+--------+--------+-----+--------+-----------+-----+
// | next | count & group 2 | code 1 | code 2 | ... | code m | undefined | ... |
// +------+-----------------+--------+--------+-----+--------+-----------+-----+
//    |
//    V
// empty_weak_fixed_array()
//
// The list of weak fixed arrays is ordered by dependency groups.

class DependentCode : public WeakFixedArray {
 public:
  DECL_CAST(DependentCode)

  enum DependencyGroup {
    // Group of code that embed a transition to this map, and depend on being
    // deoptimized when the transition is replaced by a new version.
    kTransitionGroup,
    // Group of code that omit run-time prototype checks for prototypes
    // described by this map. The group is deoptimized whenever an object
    // described by this map changes shape (and transitions to a new map),
    // possibly invalidating the assumptions embedded in the code.
    kPrototypeCheckGroup,
    // Group of code that depends on global property values in property cells
    // not being changed.
    kPropertyCellChangedGroup,
    // Group of code that omit run-time checks for field(s) introduced by
    // this map, i.e. for the field type.
    kFieldOwnerGroup,
    // Group of code that omit run-time type checks for initial maps of
    // constructors.
    kInitialMapChangedGroup,
    // Group of code that depends on tenuring information in AllocationSites
    // not being changed.
    kAllocationSiteTenuringChangedGroup,
    // Group of code that depends on element transition information in
    // AllocationSites not being changed.
    kAllocationSiteTransitionChangedGroup
  };

  // Register a code dependency of {cell} on {object}.
  static void InstallDependency(Isolate* isolate, const MaybeObjectHandle& code,
                                Handle<HeapObject> object,
                                DependencyGroup group);

  void DeoptimizeDependentCodeGroup(Isolate* isolate, DependencyGroup group);

  bool MarkCodeForDeoptimization(Isolate* isolate, DependencyGroup group);

  // The following low-level accessors are exposed only for tests.
  inline DependencyGroup group();
  inline MaybeObject object_at(int i);
  inline int count();
  inline DependentCode* next_link();

 private:
  static const char* DependencyGroupName(DependencyGroup group);

  // Get/Set {object}'s {DependentCode}.
  static DependentCode* GetDependentCode(Handle<HeapObject> object);
  static void SetDependentCode(Handle<HeapObject> object,
                               Handle<DependentCode> dep);

  static Handle<DependentCode> New(Isolate* isolate, DependencyGroup group,
                                   const MaybeObjectHandle& object,
                                   Handle<DependentCode> next);
  static Handle<DependentCode> EnsureSpace(Isolate* isolate,
                                           Handle<DependentCode> entries);
  static Handle<DependentCode> InsertWeakCode(Isolate* isolate,
                                              Handle<DependentCode> entries,
                                              DependencyGroup group,
                                              const MaybeObjectHandle& code);

  // Compact by removing cleared weak cells and return true if there was
  // any cleared weak cell.
  bool Compact();

  static int Grow(int number_of_entries) {
    if (number_of_entries < 5) return number_of_entries + 1;
    return number_of_entries * 5 / 4;
  }

  static const int kGroupCount = kAllocationSiteTransitionChangedGroup + 1;
  static const int kNextLinkIndex = 0;
  static const int kFlagsIndex = 1;
  static const int kCodesStartIndex = 2;

  inline void set_next_link(DependentCode* next);
  inline void set_count(int value);
  inline void set_object_at(int i, MaybeObject object);
  inline void clear_at(int i);
  inline void copy(int from, int to);

  inline int flags();
  inline void set_flags(int flags);
  class GroupField : public BitField<int, 0, 3> {};
  class CountField : public BitField<int, 3, 27> {};
  STATIC_ASSERT(kGroupCount <= GroupField::kMax + 1);
};

// BytecodeArray represents a sequence of interpreter bytecodes.
class BytecodeArray : public FixedArrayBase {
 public:
  enum Age {
    kNoAgeBytecodeAge = 0,
    kQuadragenarianBytecodeAge,
    kQuinquagenarianBytecodeAge,
    kSexagenarianBytecodeAge,
    kSeptuagenarianBytecodeAge,
    kOctogenarianBytecodeAge,
    kAfterLastBytecodeAge,
    kFirstBytecodeAge = kNoAgeBytecodeAge,
    kLastBytecodeAge = kAfterLastBytecodeAge - 1,
    kBytecodeAgeCount = kAfterLastBytecodeAge - kFirstBytecodeAge - 1,
    kIsOldBytecodeAge = kSexagenarianBytecodeAge
  };

  static int SizeFor(int length) {
    return OBJECT_POINTER_ALIGN(kHeaderSize + length);
  }

  // Setter and getter
  inline byte get(int index);
  inline void set(int index, byte value);

  // Returns data start address.
  inline Address GetFirstBytecodeAddress();

  // Accessors for frame size.
  inline int frame_size() const;
  inline void set_frame_size(int frame_size);

  // Accessor for register count (derived from frame_size).
  inline int register_count() const;

  // Accessors for parameter count (including implicit 'this' receiver).
  inline int parameter_count() const;
  inline void set_parameter_count(int number_of_parameters);

  // Register used to pass the incoming new.target or generator object from the
  // fucntion call.
  inline interpreter::Register incoming_new_target_or_generator_register()
      const;
  inline void set_incoming_new_target_or_generator_register(
      interpreter::Register incoming_new_target_or_generator_register);

  // Accessors for profiling count.
  inline int interrupt_budget() const;
  inline void set_interrupt_budget(int interrupt_budget);

  // Accessors for OSR loop nesting level.
  inline int osr_loop_nesting_level() const;
  inline void set_osr_loop_nesting_level(int depth);

  // Accessors for bytecode's code age.
  inline Age bytecode_age() const;
  inline void set_bytecode_age(Age age);

  // Accessors for the constant pool.
  DECL_ACCESSORS(constant_pool, FixedArray)

  // Accessors for handler table containing offsets of exception handlers.
  DECL_ACCESSORS(handler_table, ByteArray)

  // Accessors for source position table containing mappings between byte code
  // offset and source position or SourcePositionTableWithFrameCache.
  DECL_ACCESSORS(source_position_table, Object)

  inline ByteArray* SourcePositionTable();
  inline void ClearFrameCacheFromSourcePositionTable();

  DECL_CAST(BytecodeArray)

  // Dispatched behavior.
  inline int BytecodeArraySize();

  inline int raw_instruction_size();

  // Returns the size of bytecode and its metadata. This includes the size of
  // bytecode, constant pool, source position table, and handler table.
  inline int SizeIncludingMetadata();

  int SourcePosition(int offset);
  int SourceStatementPosition(int offset);

  DECL_PRINTER(BytecodeArray)
  DECL_VERIFIER(BytecodeArray)

  void Disassemble(std::ostream& os);

  void CopyBytecodesTo(BytecodeArray* to);

  // Bytecode aging
  bool IsOld() const;
  void MakeOlder();

  // Clear uninitialized padding space. This ensures that the snapshot content
  // is deterministic.
  inline void clear_padding();

// Layout description.
#define BYTECODE_ARRAY_FIELDS(V)                           \
  /* Pointer fields. */                                    \
  V(kConstantPoolOffset, kTaggedSize)                      \
  V(kHandlerTableOffset, kTaggedSize)                      \
  V(kSourcePositionTableOffset, kTaggedSize)               \
  V(kFrameSizeOffset, kIntSize)                            \
  V(kParameterSizeOffset, kIntSize)                        \
  V(kIncomingNewTargetOrGeneratorRegisterOffset, kIntSize) \
  V(kInterruptBudgetOffset, kIntSize)                      \
  V(kOSRNestingLevelOffset, kCharSize)                     \
  V(kBytecodeAgeOffset, kCharSize)                         \
  /* Total size. */                                        \
  V(kHeaderSize, 0)

  DEFINE_FIELD_OFFSET_CONSTANTS(FixedArrayBase::kHeaderSize,
                                BYTECODE_ARRAY_FIELDS)
#undef BYTECODE_ARRAY_FIELDS

  // Maximal memory consumption for a single BytecodeArray.
  static const int kMaxSize = 512 * MB;
  // Maximal length of a single BytecodeArray.
  static const int kMaxLength = kMaxSize - kHeaderSize;

  class BodyDescriptor;

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(BytecodeArray);
};

// DeoptimizationData is a fixed array used to hold the deoptimization data for
// optimized code.  It also contains information about functions that were
// inlined.  If N different functions were inlined then the first N elements of
// the literal array will contain these functions.
//
// It can be empty.
class DeoptimizationData : public FixedArrayPtr {
 public:
  // Layout description.  Indices in the array.
  static const int kTranslationByteArrayIndex = 0;
  static const int kInlinedFunctionCountIndex = 1;
  static const int kLiteralArrayIndex = 2;
  static const int kOsrBytecodeOffsetIndex = 3;
  static const int kOsrPcOffsetIndex = 4;
  static const int kOptimizationIdIndex = 5;
  static const int kSharedFunctionInfoIndex = 6;
  static const int kInliningPositionsIndex = 7;
  static const int kFirstDeoptEntryIndex = 8;

  // Offsets of deopt entry elements relative to the start of the entry.
  static const int kBytecodeOffsetRawOffset = 0;
  static const int kTranslationIndexOffset = 1;
  static const int kPcOffset = 2;
  static const int kDeoptEntrySize = 3;

// Simple element accessors.
#define DECL_ELEMENT_ACCESSORS(name, type) \
  inline type name() const;                \
  inline void Set##name(type value);

  DECL_ELEMENT_ACCESSORS(TranslationByteArray, ByteArray*)
  DECL_ELEMENT_ACCESSORS(InlinedFunctionCount, Smi)
  DECL_ELEMENT_ACCESSORS(LiteralArray, FixedArray*)
  DECL_ELEMENT_ACCESSORS(OsrBytecodeOffset, Smi)
  DECL_ELEMENT_ACCESSORS(OsrPcOffset, Smi)
  DECL_ELEMENT_ACCESSORS(OptimizationId, Smi)
  DECL_ELEMENT_ACCESSORS(SharedFunctionInfo, Object*)
  DECL_ELEMENT_ACCESSORS(InliningPositions, PodArray<InliningPosition>*)

#undef DECL_ELEMENT_ACCESSORS

// Accessors for elements of the ith deoptimization entry.
#define DECL_ENTRY_ACCESSORS(name, type) \
  inline type name(int i) const;         \
  inline void Set##name(int i, type value);

  DECL_ENTRY_ACCESSORS(BytecodeOffsetRaw, Smi)
  DECL_ENTRY_ACCESSORS(TranslationIndex, Smi)
  DECL_ENTRY_ACCESSORS(Pc, Smi)

#undef DECL_ENTRY_ACCESSORS

  inline BailoutId BytecodeOffset(int i);

  inline void SetBytecodeOffset(int i, BailoutId value);

  inline int DeoptCount();

  static const int kNotInlinedIndex = -1;

  // Returns the inlined function at the given position in LiteralArray, or the
  // outer function if index == kNotInlinedIndex.
  class SharedFunctionInfo* GetInlinedFunction(int index);

  // Allocates a DeoptimizationData.
  static Handle<DeoptimizationData> New(Isolate* isolate, int deopt_entry_count,
                                        PretenureFlag pretenure);

  // Return an empty DeoptimizationData.
  static Handle<DeoptimizationData> Empty(Isolate* isolate);

  DECL_CAST2(DeoptimizationData)

#ifdef ENABLE_DISASSEMBLER
  void DeoptimizationDataPrint(std::ostream& os);  // NOLINT
#endif

 private:
  static int IndexForEntry(int i) {
    return kFirstDeoptEntryIndex + (i * kDeoptEntrySize);
  }

  static int LengthFor(int entry_count) { return IndexForEntry(entry_count); }

  OBJECT_CONSTRUCTORS(DeoptimizationData, FixedArrayPtr)
};

class SourcePositionTableWithFrameCache : public Tuple2 {
 public:
  DECL_ACCESSORS(source_position_table, ByteArray)
  DECL_ACCESSORS2(stack_frame_cache, SimpleNumberDictionary)

  DECL_CAST(SourcePositionTableWithFrameCache)

// Layout description.
#define SOURCE_POSITION_TABLE_WITH_FRAME_FIELDS(V) \
  V(kSourcePositionTableIndex, kTaggedSize)        \
  V(kStackFrameCacheIndex, kTaggedSize)            \
  /* Total size. */                                \
  V(kSize, 0)

  DEFINE_FIELD_OFFSET_CONSTANTS(Struct::kHeaderSize,
                                SOURCE_POSITION_TABLE_WITH_FRAME_FIELDS)
#undef SOURCE_POSITION_TABLE_WITH_FRAME_FIELDS

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(SourcePositionTableWithFrameCache);
};

}  // namespace internal
}  // namespace v8

#include "src/objects/object-macros-undef.h"

#endif  // V8_OBJECTS_CODE_H_