Make objects embedded in optimized code weak.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 4dfa076ebd7745c14e953cbf0deb3bd396eb5c5a..94ba4a0d6cc469693ce9bbe6ff5db8ddec494887 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1887,6 +1887,23 @@ class Heap {
     Heap* heap_;
   };
 

[Hannes Payer (out of office), 2013/10/01 13:13:50]

What about?
- Making weak_object_to_code, weak_object_to_code_address, and
set_weak_object_to_code private?
- Adding an InitializeWeakObjectToCodeTable which calls
set_weak_object_to_code(isolate_->heap()->undefined_value()).
- Creating the WeakHashtable when accessing the non-initialized hash table.

[ulan, 2013/10/01 14:50:29]

I moved these methods up to the methods of the existing weak lists (like
allocation_sites_list). We need these methods public because mark_compact
accesses the table.

+  Object* weak_object_to_code() {
+    return weak_object_to_code_;
+  }
+
+  Object** weak_object_to_code_address() {
+    return &weak_object_to_code_;
+  }
+
+  void set_weak_object_to_code(Object* value) {
+    ASSERT(!InNewSpace(value));
+    weak_object_to_code_ = value;
+  }
+
+  MaybeObject* AddWeakObjectToCodeDependency(Object* obj, DependentCode* dep);
+
+  DependentCode* LookupWeakObjectToCodeDependency(Object* obj);
+
  private:
   Heap();
 
@@ -2365,6 +2382,11 @@ class Heap {
   bool relocation_mutex_locked_by_optimizer_thread_;
 #endif  // DEBUG;
 
+  // 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_;

[Hannes Payer (out of office), 2013/10/01 13:13:50]

Can we move that up to the other weak list heads, after allocation_sites_list_?
Moreover, the comment about the initialization applies also to the other weak
lists, we could add it on top of the list heads. Aaand, can we change the name
to weak_object_to_code_table_.

[ulan, 2013/10/01 14:50:29]

Done.

+
   friend class Factory;
   friend class GCTracer;
   friend class DisallowAllocationFailure;