Add "has fast elements" bit to maps and use it in inlined keyed loads.

src/objects-debug.cc

 // 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 521 matching lines @@
 
 
 void JSObject::JSObjectVerify() {
   VerifyHeapPointer(properties());
   VerifyHeapPointer(elements());
   if (HasFastProperties()) {
     CHECK_EQ(map()->unused_property_fields(),
              (map()->inobject_properties() + properties()->length() -
               map()->NextFreePropertyIndex()));
   }
+  ASSERT(map()->has_fast_elements() ==
+         (elements()->map() == Heap::fixed_array_map()));
+  ASSERT(map()->has_fast_elements() == HasFastElements());
 }
 
 
 static const char* TypeToString(InstanceType type) {
   switch (type) {
     case INVALID_TYPE: return "INVALID";
     case MAP_TYPE: return "MAP";
     case HEAP_NUMBER_TYPE: return "HEAP_NUMBER";
     case SYMBOL_TYPE: return "SYMBOL";
     case ASCII_SYMBOL_TYPE: return "ASCII_SYMBOL";
@@ skipping 801 matching lines @@
       ASSERT(get(i)->IsTheHole());
       get(i)->Verify();
     }
   }
 }
 
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal