Implement aging of maps embedded in optimized code.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index d025b2482339da3cef73acefe2b4d2507be05a5e..04657af4ad570676b750272a28d9cedbd4f046b3 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -994,6 +994,7 @@ template <class C> inline bool Is(Object* obj);
   V(WeakCell)                      \
   V(ObjectHashTable)               \
   V(WeakHashTable)                 \
+  V(EmbeddedMapCache)              \
   V(OrderedHashTable)
 
 // Object is the abstract superclass for all classes in the
@@ -3996,7 +3997,7 @@ class OrderedHashMap:public OrderedHashTable<
 
 
 template <int entrysize>
-class WeakHashTableShape : public BaseShape<Handle<Object> > {
+class HeapPointerShape : public BaseShape<Handle<Object> > {

[Hannes Payer (out of office), 2014/11/17 17:34:33]

Why is that a good name?

  public:
   static inline bool IsMatch(Handle<Object> key, Object* other);
   static inline uint32_t Hash(Handle<Object> key);
@@ -4010,11 +4011,11 @@ class WeakHashTableShape : public BaseShape<Handle<Object> > {
 // WeakHashTable maps keys that are arbitrary objects to object values.
 // It is used for the global weak hash table that maps objects
 // embedded in optimized code to dependent code lists.
-class WeakHashTable: public HashTable<WeakHashTable,
-                                      WeakHashTableShape<2>,
-                                      Handle<Object> > {
-  typedef HashTable<
-      WeakHashTable, WeakHashTableShape<2>, Handle<Object> > DerivedHashTable;
+class WeakHashTable
+    : public HashTable<WeakHashTable, HeapPointerShape<2>, Handle<Object> > {
+  typedef HashTable<WeakHashTable, HeapPointerShape<2>, Handle<Object> >
+      DerivedHashTable;
+
  public:
   DECLARE_CAST(WeakHashTable)
 
@@ -4049,6 +4050,33 @@ class WeakHashTable: public HashTable<WeakHashTable,
 };
 
 

[Hannes Payer (out of office), 2014/11/17 17:34:33]

Please add a detailed description about what the EmbeddedMapCache is and what it
motivation is.

+class EmbeddedMapCache
+    : public HashTable<EmbeddedMapCache, HeapPointerShape<2>, Handle<Object> > {
+  typedef HashTable<EmbeddedMapCache, HeapPointerShape<2>, Handle<Object> >
+      DerivedHashTable;
+
+ public:
+  DECLARE_CAST(EmbeddedMapCache)
+
+  MUST_USE_RESULT static Handle<EmbeddedMapCache> Put(
+      Handle<EmbeddedMapCache> table, Handle<Map> key);
+
+  void Age();
+
+ private:
+  static const int kMaxAge = 5;
+
+  friend class MarkCompactCollector;
+
+  void AddEntry(int entry, Handle<Object> key, Handle<Object> value);
+
+  // Returns the index to the value of an entry.
+  static inline int EntryToValueIndex(int entry) {
+    return EntryToIndex(entry) + 1;
+  }
+};
+
+
 // JSFunctionResultCache caches results of some JSFunction invocation.
 // It is a fixed array with fixed structure:
 //   [0]: factory function