Further robustify the keyed lookup cache against unlucky hash

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 2117 matching lines @@
  public:
   // Lookup field offset for (map, name). If absent, -1 is returned.
   int Lookup(Map* map, String* name);
 
   // Update an element in the cache.
   void Update(Map* map, String* name, int field_offset);
 
   // Clear the cache.
   void Clear();
 
-  static const int kLength = 128;
+  static const int kLength = 256;
   static const int kCapacityMask = kLength - 1;
   static const int kMapHashShift = 5;
-  static const int kHashMask = -2;  // Zero the last bit.
-  static const int kEntriesPerBucket = 2;
+  static const int kHashMask = -4;  // Zero the last two bits.
+  static const int kEntriesPerBucket = 4;

[Yang, 2012/01/23 15:53:31]

Maybe add assertions such as
STATIC_ASSERT(IS_POWER_OF_TWO(kEntriesPerBucket));
STATIC_ASSERT(kHashMask == -kEntriesPerBucket)

   static const int kNotFound = -1;
 
  private:
   KeyedLookupCache() {
     for (int i = 0; i < kLength; ++i) {
       keys_[i].map = NULL;
       keys_[i].name = NULL;
       field_offsets_[i] = kNotFound;
     }
   }
@@ skipping 465 matching lines @@
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #undef HEAP
 
 #endif  // V8_HEAP_H_