Implement aging of maps embedded in optimized code.

src/objects.h

 // Copyright 2012 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_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 976 matching lines @@
   V(JSGlobalObject)                \
   V(JSBuiltinsObject)              \
   V(JSGlobalProxy)                 \
   V(UndetectableObject)            \
   V(AccessCheckNeeded)             \
   V(Cell)                          \
   V(PropertyCell)                  \
   V(WeakCell)                      \
   V(ObjectHashTable)               \
   V(WeakHashTable)                 \
+  V(EmbeddedMapCache)              \
   V(OrderedHashTable)
 
 // Object is the abstract superclass for all classes in the
 // object hierarchy.
 // Object does not use any virtual functions to avoid the
 // allocation of the C++ vtable.
 // Since both Smi and HeapObject are subclasses of Object no
 // data members can be present in Object.
 class Object {
  public:
@@ skipping 2982 matching lines @@
   Object* ValueAt(int entry) {
     return get(EntryToIndex(entry) + kValueOffset);
   }
 
  private:
   static const int kValueOffset = 1;
 };
 
 
 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);
   static inline uint32_t HashForObject(Handle<Object> key, Object* object);
   static inline Handle<Object> AsHandle(Isolate* isolate, Handle<Object> key);
   static const int kPrefixSize = 0;
   static const int kEntrySize = entrysize;
 };
 
 
 // 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)
 
   // Looks up the value associated with the given key. The hole value is
   // returned in case the key is not present.
   Object* Lookup(Handle<Object> key);
 
   // Adds (or overwrites) the value associated with the given key. Mapping a
   // key to the hole value causes removal of the whole entry.
   MUST_USE_RESULT static Handle<WeakHashTable> Put(Handle<WeakHashTable> table,
@@ skipping 13 matching lines @@
   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;
   }
 };
 
 

[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
 //   [1]: finger index
 //   [2]: current cache size
 //   [3]: dummy field.
 // The rest of array are key/value pairs.
 class JSFunctionResultCache: public FixedArray {
  public:
   static const int kFactoryIndex = 0;
@@ skipping 6875 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_