Make objects embedded in optimized code weak.

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1290 matching lines @@
     array_buffers_list_ = object;
   }
   Object* array_buffers_list() { return array_buffers_list_; }
 
   void set_allocation_sites_list(Object* object) {
     allocation_sites_list_ = object;
   }
   Object* allocation_sites_list() { return allocation_sites_list_; }
   Object** allocation_sites_list_address() { return &allocation_sites_list_; }
 
+  Object* weak_object_to_code_table() { return weak_object_to_code_table_; }
+
   // Number of mark-sweeps.
   unsigned int ms_count() { return ms_count_; }
 
   // Iterates over all roots in the heap.
   void IterateRoots(ObjectVisitor* v, VisitMode mode);
   // Iterates over all strong roots in the heap.
   void IterateStrongRoots(ObjectVisitor* v, VisitMode mode);
   // Iterates over all the other roots in the heap.
   void IterateWeakRoots(ObjectVisitor* v, VisitMode mode);
 
@@ skipping 71 matching lines @@
   // Get address of native contexts list for serialization support.
   Object** native_contexts_list_address() {
     return &native_contexts_list_;
   }
 
 #ifdef VERIFY_HEAP
   // Verify the heap is in its normal state before or after a GC.
   void Verify();
 
 
-  bool weak_embedded_maps_verification_enabled() {
-    return no_weak_embedded_maps_verification_scope_depth_ == 0;
+  bool weak_embedded_objects_verification_enabled() {
+    return no_weak_object_verification_scope_depth_ == 0;
   }
 #endif
 
 #ifdef DEBUG
   void Print();
   void PrintHandles();
 
   void OldPointerSpaceCheckStoreBuffer();
   void MapSpaceCheckStoreBuffer();
   void LargeObjectSpaceCheckStoreBuffer();
@@ skipping 432 matching lines @@
 #ifdef DEBUG
     static bool IsLockedByOptimizerThread(Heap* heap) {
       return heap->relocation_mutex_locked_by_optimizer_thread_;
     }
 #endif  // DEBUG
 
    private:
     Heap* heap_;
   };
 
+  MaybeObject* AddWeakObjectToCodeDependency(Object* obj, DependentCode* dep);
+
+  DependentCode* LookupWeakObjectToCodeDependency(Object* obj);
+
+  void InitializeWeakObjectToCodeTable() {
+    set_weak_object_to_code_table(undefined_value());
+  }
+
+  void EnsureWeakObjectToCodeTable();
+
  private:
   Heap();
 
   // This can be calculated directly from a pointer to the heap; however, it is
   // more expedient to get at the isolate directly from within Heap methods.
   Isolate* isolate_;
 
   Object* roots_[kRootListLength];
 
   intptr_t code_range_size_;
@@ skipping 94 matching lines @@
   intptr_t amount_of_external_allocated_memory_;
 
   // Caches the amount of external memory registered at the last global gc.
   intptr_t amount_of_external_allocated_memory_at_last_global_gc_;
 
   // Indicates that an allocation has failed in the old generation since the
   // last GC.
   bool old_gen_exhausted_;
 
   // Weak list heads, threaded through the objects.
+  // List heads are initilized lazily and contain the undefined_value at start.
   Object* native_contexts_list_;
   Object* array_buffers_list_;
   Object* allocation_sites_list_;
 
+  // WeakHashTable that maps objects embedded in optimized code to dependent
+  // code list. It is initilized lazily and contains the undefined_value at
+  // start.
+  Object* weak_object_to_code_table_;
+
   StoreBufferRebuilder store_buffer_rebuilder_;
 
   struct StringTypeTable {
     InstanceType type;
     int size;
     RootListIndex index;
   };
 
   struct ConstantStringTable {
     const char* contents;
@@ skipping 288 matching lines @@
     return heap_size_mb / kMbPerMs;
   }
 
   // Returns true if no more GC work is left.
   bool IdleGlobalGC();
 
   void AdvanceIdleIncrementalMarking(intptr_t step_size);
 
   void ClearObjectStats(bool clear_last_time_stats = false);
 
+  void set_weak_object_to_code_table(Object* value) {
+    ASSERT(!InNewSpace(value));
+    weak_object_to_code_table_ = value;
+  }
+
+  Object** weak_object_to_code_table_address() {
+    return &weak_object_to_code_table_;
+  }
+
   static const int kInitialStringTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
   static const int kInitialNumberStringCacheSize = 256;
 
   // Object counts and used memory by InstanceType
   size_t object_counts_[OBJECT_STATS_COUNT];
   size_t object_counts_last_time_[OBJECT_STATS_COUNT];
   size_t object_sizes_[OBJECT_STATS_COUNT];
   size_t object_sizes_last_time_[OBJECT_STATS_COUNT];
 
@@ skipping 35 matching lines @@
   int mark_sweeps_since_idle_round_started_;
   unsigned int gc_count_at_last_idle_gc_;
   int scavenges_since_last_idle_round_;
 
   // If the --deopt_every_n_garbage_collections flag is set to a positive value,
   // this variable holds the number of garbage collections since the last
   // deoptimization triggered by garbage collection.
   int gcs_since_last_deopt_;
 
 #ifdef VERIFY_HEAP
-  int no_weak_embedded_maps_verification_scope_depth_;
+  int no_weak_object_verification_scope_depth_;
 #endif
 
   static const int kMaxMarkSweepsInIdleRound = 7;
   static const int kIdleScavengeThreshold = 5;
 
   // Shared state read by the scavenge collector and set by ScavengeObject.
   PromotionQueue promotion_queue_;
 
   // Flag is set when the heap has been configured.  The heap can be repeatedly
   // configured through the API until it is set up.
@@ skipping 13 matching lines @@
   friend class Factory;
   friend class GCTracer;
   friend class DisallowAllocationFailure;
   friend class AlwaysAllocateScope;
   friend class Page;
   friend class Isolate;
   friend class MarkCompactCollector;
   friend class MarkCompactMarkingVisitor;
   friend class MapCompact;
 #ifdef VERIFY_HEAP
-  friend class NoWeakEmbeddedMapsVerificationScope;
+  friend class NoWeakObjectVerificationScope;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(Heap);
 };
 
 
 class HeapStats {
  public:
   static const int kStartMarker = 0xDECADE00;
   static const int kEndMarker = 0xDECADE01;
@@ skipping 44 matching lines @@
  public:
   inline AlwaysAllocateScope();
   inline ~AlwaysAllocateScope();
 
  private:
   // Implicitly disable artificial allocation failures.
   DisallowAllocationFailure disallow_allocation_failure_;
 };
 
 #ifdef VERIFY_HEAP
-class NoWeakEmbeddedMapsVerificationScope {
+class NoWeakObjectVerificationScope {
  public:
-  inline NoWeakEmbeddedMapsVerificationScope();
-  inline ~NoWeakEmbeddedMapsVerificationScope();
+  inline NoWeakObjectVerificationScope();
+  inline ~NoWeakObjectVerificationScope();
 };
 #endif
 
 
 // Visitor class to verify interior pointers in spaces that do not contain
 // or care about intergenerational references. 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 {
@@ skipping 583 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_