Speed up compares with characters ie single-character strings....

src/ia32/virtual-frame-ia32.h

 // Copyright 2009 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 377 matching lines @@
   // Push an element on the virtual frame.
   void Push(Register reg);
   void Push(Handle<Object> value);
   void Push(Smi* value) {
     Push(Handle<Object> (value));
   }
 
   // Pushing a result invalidates it (its contents become owned by the
   // frame).
   void Push(Result* result) {
+    // This assert will trigger if you try to push the same value twice.
+    ASSERT(result->is_valid());
     if (result->is_register()) {
       Push(result->reg());
     } else {
       ASSERT(result->is_constant());
       Push(result->handle());
     }
     result->Unuse();
   }
 
   // Nip removes zero or more elements from immediately below the top
@@ skipping 161 matching lines @@
   bool Equals(VirtualFrame* other);
 
   // Classes that need raw access to the elements_ array.
   friend class DeferredCode;
   friend class JumpTarget;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_VIRTUAL_FRAME_IA32_H_