Make the performance of the VM more predictable by not letting the hash seed

src/hashmap.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 41 matching lines @@
                       AllocationPolicy allocator = AllocationPolicy());
 
   ~TemplateHashMapImpl();
 
   // HashMap entries are (key, value, hash) triplets.
   // Some clients may not need to use the value slot
   // (e.g. implementers of sets, where the key is the value).
   struct Entry {
     void* key;
     void* value;
-    uint32_t hash;  // the full hash value for key
+    uint32_t hash;  // The full hash value for key
+    int order;  // If you never remove entries this is the insertion order.
   };
 
   // If an entry with matching key is found, Lookup()
   // returns that entry. If no matching entry is found,
   // but insert is set, a new entry is inserted with
   // corresponding key, key hash, and NULL value.
   // Otherwise, NULL is returned.
   Entry* Lookup(void* key, uint32_t hash, bool insert,
                 AllocationPolicy allocator = AllocationPolicy());
 
@@ skipping 60 matching lines @@
   Entry* p = Probe(key, hash);
   if (p->key != NULL) {
     return p;
   }
 
   // No entry found; insert one if necessary.
   if (insert) {
     p->key = key;
     p->value = NULL;
     p->hash = hash;
+    p->order = occupancy_;
     occupancy_++;
 
     // Grow the map if we reached >= 80% occupancy.
     if (occupancy_ + occupancy_/4 >= capacity_) {
       Resize(allocator);
       p = Probe(key, hash);
     }
 
     return p;
   }
@@ skipping 137 matching lines @@
 void TemplateHashMapImpl<AllocationPolicy>::Resize(AllocationPolicy allocator) {
   Entry* map = map_;
   uint32_t n = occupancy_;
 
   // Allocate larger map.
   Initialize(capacity_ * 2, allocator);
 
   // Rehash all current entries.
   for (Entry* p = map; n > 0; p++) {
     if (p->key != NULL) {
-      Lookup(p->key, p->hash, true, allocator)->value = p->value;
+      Entry* entry = Lookup(p->key, p->hash, true, allocator);
+      entry->value = p->value;
+      entry->order = p->order;
       n--;
     }
   }
 
   // Delete old map.
   AllocationPolicy::Delete(map);
 }
 
 
 // A hash map for pointer keys and values with an STL-like interface.
@@ skipping 40 matching lines @@
   Iterator end() const { return Iterator(this, NULL); }
   Iterator find(Key* key, bool insert = false,
                 AllocationPolicy allocator = AllocationPolicy()) {
     return Iterator(this, this->Lookup(key, key->Hash(), insert, allocator));
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HASHMAP_H_