heap.h.svn-base

Google浏览器V8内核代码

  // corresponding to the range of allocated pointers
  // [object_start, object_end).
  static void IterateRSetRange(Address object_start,
                               Address object_end,
                               Address rset_start,
                               ObjectSlotCallback copy_object_func);

  // Returns whether the object resides in new space.
  static inline bool InNewSpace(Object* object);
  static inline bool InFromSpace(Object* object);
  static inline bool InToSpace(Object* object);

  // Checks whether an address/object in the heap (including auxiliary
  // area and unused area).
  static bool Contains(Address addr);
  static bool Contains(HeapObject* value);

  // Checks whether an address/object in a space.
  // Currently used by tests and heap verification only.
  static bool InSpace(Address addr, AllocationSpace space);
  static bool InSpace(HeapObject* value, AllocationSpace space);

  // Finds out which space an object should get promoted to based on its type.
  static inline OldSpace* TargetSpace(HeapObject* object);

  // Sets the stub_cache_ (only used when expanding the dictionary).
  static void set_code_stubs(Dictionary* value) { code_stubs_ = value; }

  // Sets the non_monomorphic_cache_ (only used when expanding the dictionary).
  static void set_non_monomorphic_cache(Dictionary* value) {
    non_monomorphic_cache_ = value;
  }

#ifdef DEBUG
  static void Print();
  static void PrintHandles();

  // Verify the heap is in its normal state before or after a GC.
  static void Verify();

  // Report heap statistics.
  static void ReportHeapStatistics(const char* title);
  static void ReportCodeStatistics(const char* title);

  // Fill in bogus values in from space
  static void ZapFromSpace();
#endif

  // Makes a new symbol object
  // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
  // failed.
  // Please note this function does not perform a garbage collection.
  static Object* CreateSymbol(const char* str, int length, int hash);
  static Object* CreateSymbol(String* str);

  // Write barrier support for address[offset] = o.
  inline static void RecordWrite(Address address, int offset);

  // Given an address occupied by a live code object, return that object.
  static Object* FindCodeObject(Address a);

  // Invoke Shrink on shrinkable spaces.
  static void Shrink();

  enum HeapState { NOT_IN_GC, SCAVENGE, MARK_COMPACT };
  static inline HeapState gc_state() { return gc_state_; }

#ifdef DEBUG
  static bool IsAllocationAllowed() { return allocation_allowed_; }
  static inline bool allow_allocation(bool enable);

  static bool disallow_allocation_failure() {
    return disallow_allocation_failure_;
  }

  static void TracePathToObject();
  static void TracePathToGlobal();
#endif

  // Callback function pased to Heap::Iterate etc.  Copies an object if
  // necessary, the object might be promoted to an old space.  The caller must
  // ensure the precondition that the object is (a) a heap object and (b) in
  // the heap's from space.
  static void CopyObject(HeapObject** p);

  // Clear a range of remembered set addresses corresponding to the object
  // area address 'start' with size 'size_in_bytes', eg, when adding blocks
  // to the free list.
  static void ClearRSetRange(Address start, int size_in_bytes);

  // Rebuild remembered set in old and map spaces.
  static void RebuildRSets();

  //
  // Support for the API.
  //

  static bool CreateApiObjects();

  // Attempt to find the number in a small cache.  If we finds it, return
  // the string representation of the number.  Otherwise return undefined.
  static Object* GetNumberStringCache(Object* number);

  // Update the cache with a new number-string pair.
  static void SetNumberStringCache(Object* number, String* str);

  // Entries in the cache.  Must be a power of 2.
  static const int kNumberStringCacheSize = 64;

  // Adjusts the amount of registered external memory.
  // Returns the adjusted value.
  static int AdjustAmountOfExternalAllocatedMemory(int change_in_bytes) {
    int amount = amount_of_external_allocated_memory_ + change_in_bytes;
    if (change_in_bytes >= 0) {
      // Avoid overflow.
      if (amount > amount_of_external_allocated_memory_) {
        amount_of_external_allocated_memory_ = amount;
      }
    } else {
      // Avoid underflow.
      if (amount >= 0) {
        amount_of_external_allocated_memory_ = amount;
      }
    }
    ASSERT(amount_of_external_allocated_memory_ >= 0);
    return amount_of_external_allocated_memory_;
  }

 private:
  static int semispace_size_;
  static int initial_semispace_size_;
  static int young_generation_size_;
  static int old_generation_size_;

  static int new_space_growth_limit_;
  static int scavenge_count_;

  static const int kMaxMapSpaceSize = 8*MB;

  static NewSpace* new_space_;
  static OldSpace* old_pointer_space_;
  static OldSpace* old_data_space_;
  static OldSpace* code_space_;
  static MapSpace* map_space_;
  static LargeObjectSpace* lo_space_;
  static HeapState gc_state_;

  // Returns the size of object residing in non new spaces.
  static int PromotedSpaceSize();

  // Returns the amount of external memory registered since last global gc.
  static int PromotedExternalMemorySize();

  static int mc_count_;  // how many mark-compact collections happened
  static int gc_count_;  // how many gc happened

#ifdef DEBUG
  static bool allocation_allowed_;

  // If the --gc-interval flag is set to a positive value, this
  // variable holds the value indicating the number of allocations
  // remain until the next failure and garbage collection.
  static int allocation_timeout_;

  // Do we expect to be able to handle allocation failure at this
  // time?
  static bool disallow_allocation_failure_;
#endif  // DEBUG

  // Promotion limit that trigger a global GC
  static int promoted_space_limit_;

  // The amount of external memory registered through the API kept alive
  // by global handles
  static int amount_of_external_allocated_memory_;

  // Caches the amount of external memory registered at the last global gc.
  static int amount_of_external_allocated_memory_at_last_global_gc_;

  // Indicates that an allocation has failed in the old generation since the
  // last GC.
  static int old_gen_exhausted_;

  // Declare all the roots
#define ROOT_DECLARATION(type, name) static type* name##_;
  ROOT_LIST(ROOT_DECLARATION)
#undef ROOT_DECLARATION

// Utility type maps
#define DECLARE_STRUCT_MAP(NAME, Name, name) static Map* name##_map_;
  STRUCT_LIST(DECLARE_STRUCT_MAP)
#undef DECLARE_STRUCT_MAP

#define SYMBOL_DECLARATION(name, str) static String* name##_;
  SYMBOL_LIST(SYMBOL_DECLARATION)
#undef SYMBOL_DECLARATION

  // GC callback function, called before and after mark-compact GC.
  // Allocations in the callback function are disallowed.
  static GCCallback global_gc_prologue_callback_;
  static GCCallback global_gc_epilogue_callback_;

  // Checks whether a global GC is necessary
  static GarbageCollector SelectGarbageCollector(AllocationSpace space);

  // Performs garbage collection
  static void PerformGarbageCollection(AllocationSpace space,
                                       GarbageCollector collector,
                                       GCTracer* tracer);

  // Returns either a Smi or a Number object from 'value'. If 'new_object'
  // is false, it may return a preallocated immutable object.
  static Object* SmiOrNumberFromDouble(double value,
                                       bool new_object,
                                       PretenureFlag pretenure = NOT_TENURED);

  // Allocate an uninitialized object in map space.  The behavior is identical
  // to Heap::AllocateRaw(size_in_bytes, MAP_SPACE), except that (a) it doesn't
  // have to test the allocation space argument and (b) can reduce code size
  // (since both AllocateRaw and AllocateRawMap are inlined).
  static inline Object* AllocateRawMap(int size_in_bytes);


  // Initializes a JSObject based on its map.
  static void InitializeJSObjectFromMap(JSObject* obj,
                                        FixedArray* properties,
                                        Map* map);

  static bool CreateInitialMaps();
  static bool CreateInitialObjects();
  static void CreateFixedStubs();
  static Object* CreateOddball(Map* map,
                               const char* to_string,
                               Object* to_number);

  // Allocate empty fixed array.
  static Object* AllocateEmptyFixedArray();

  // Performs a minor collection in new generation.
  static void Scavenge();

  // Performs a major collection in the whole heap.
  static void MarkCompact(GCTracer* tracer);

  // Code to be run before and after mark-compact.
  static void MarkCompactPrologue();
  static void MarkCompactEpilogue();

  // Helper function used by CopyObject to copy a source object to an
  // allocated target object and update the forwarding pointer in the source
  // object.  Returns the target object.
  static HeapObject* MigrateObject(HeapObject** source_p,
                                   HeapObject* target,
                                   int size);

  // Helper function that governs the promotion policy from new space to
  // old.  If the object's old address lies below the new space's age
  // mark or if we've already filled the bottom 1/16th of the to space,
  // we try to promote this object.
  static inline bool ShouldBePromoted(Address old_address, int object_size);
#if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
  // Record the copy of an object in the NewSpace's statistics.
  static void RecordCopiedObject(HeapObject* obj);

  // Record statistics before and after garbage collection.
  static void ReportStatisticsBeforeGC();
  static void ReportStatisticsAfterGC();
#endif

  // Update an old object's remembered set
  static int UpdateRSet(HeapObject* obj);

  // Rebuild remembered set in an old space.
  static void RebuildRSets(PagedSpace* space);

  // Rebuild remembered set in the large object space.
  static void RebuildRSets(LargeObjectSpace* space);

  static const int kInitialSymbolTableSize = 2048;
  static const int kInitialEvalCacheSize = 64;

  friend class Factory;
  friend class DisallowAllocationFailure;
};


#ifdef DEBUG
// Visitor class to verify interior pointers that do not have remembered set
// bits.  All heap object pointers have to point into the heap to a location
// that has a map pointer at its first word.  Caveat: Heap::Contains is an
// approximation because it can return true for objects in a heap space but
// above the allocation pointer.
class VerifyPointersVisitor: public ObjectVisitor {
 public: