Allow a platform to indicate that some CPU features are always...

src/serialize.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 130 matching lines @@
   int roots() { return roots_; }
   int objects() { return objects_; }
 
 #ifdef DEBUG
   // insert "tag" into the serialized stream
   virtual void Synchronize(const char* tag);
 #endif
 
   static bool enabled() { return serialization_enabled_; }
 
-  static void Enable() { serialization_enabled_ = true; }
+  static void Enable() {
+    if (!serialization_enabled_) {
+      ASSERT(!too_late_to_enable_now_);
+    }
+    serialization_enabled_ = true;
+  }
+
   static void Disable() { serialization_enabled_ = false; }
+  // Call this when you have made use of the fact that there is no serialization
+  // going on.
+  static void TooLateToEnableNow() { too_late_to_enable_now_ = true; }
 
  private:
   friend class ReferenceUpdater;
 
   virtual void VisitPointers(Object** start, Object** end);
   virtual void VisitCodeTarget(RelocInfo* rinfo);
   bool IsVisited(HeapObject* obj);
 
   Address GetSavedAddress(HeapObject* obj);
 
@@ skipping 24 matching lines @@
   RelativeAddress Allocate(HeapObject* obj);
 
   void InitializeAllocators();
 
   SnapshotWriter* writer_;
   bool root_;  // serializing a root?
   int roots_;  // number of roots visited
   int objects_;  // number of objects serialized
 
   static bool serialization_enabled_;
+  // Did we already make use of the fact that serialization was not enabled?
+  static bool too_late_to_enable_now_;
 
   int flags_end_;  // The position right after the flags.
 
   // An array of per-space SimulatedHeapSpaces used as memory allocators.
   SimulatedHeapSpace* allocator_[LAST_SPACE+1];
   // A list of global handles at serialization time.
   List<Object**> global_handles_;
 
   ExternalReferenceEncoder* reference_encoder_;
 
@@ skipping 411 matching lines @@
 
   friend class ObjectSerializer;
   friend class Deserializer2;
 
   DISALLOW_COPY_AND_ASSIGN(Serializer2);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SERIALIZE_H_