Exclude the bit-field bits from string hash codes. String hash codes...

src/stub-cache.h

 // Copyright 2006-2008 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 180 matching lines @@
 
  private:
   friend class SCTableReference;
   static const int kPrimaryTableSize = 2048;
   static const int kSecondaryTableSize = 512;
   static Entry primary_[];
   static Entry secondary_[];
 
   // Computes the hashed offsets for primary and secondary caches.
   static int PrimaryOffset(String* name, Code::Flags flags, Map* map) {
+    // This works well because the heap object tag size and the hash
+    // shift are equal.  Shifting down the length field to get the
+    // hash code would effectively throw away two bits of the hash
+    // code.
+    ASSERT(kHeapObjectTagSize == kHashShift);
     // Compute the hash of the name (use entire length field).
-    uint32_t name_hash = name->length_field();
-    ASSERT(name_hash & String::kHashComputedMask);
+    ASSERT(name->HasHashCode());
+    uint32_t field = name->length_field();
     // Base the offset on a simple combination of name, flags, and map.
-    uint32_t key = (reinterpret_cast<uint32_t>(map) + name_hash) ^ flags;
+    uint32_t key = (reinterpret_cast<uint32_t>(map) + field) ^ flags;
     return key & ((kPrimaryTableSize - 1) << kHeapObjectTagSize);
   }
 
   static int SecondaryOffset(String* name, Code::Flags flags, int seed) {
     // Use the seed from the primary cache in the secondary cache.
     uint32_t key = seed - reinterpret_cast<uint32_t>(name) + flags;
     return key & ((kSecondaryTableSize - 1) << kHeapObjectTagSize);
   }
 
   // Compute the entry for a given offset in exactly the same way as
@@ skipping 246 matching lines @@
 
   const ParameterCount& arguments() { return arguments_; }
 
   Object* GetCode(PropertyType type);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_STUB_CACHE_H_