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

src/ia32/ic-ia32.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 295 matching lines @@
   // Is it a string?
   __ CmpObjectType(eax, FIRST_NONSTRING_TYPE, edx);
   __ j(above_equal, &slow);
   // Is the string an array index, with cached numeric value?
   __ mov(ebx, FieldOperand(eax, String::kHashFieldOffset));
   __ test(ebx, Immediate(String::kIsArrayIndexMask));
   __ j(not_zero, &index_string, not_taken);
 
   // Is the string a symbol?
   __ movzx_b(ebx, FieldOperand(edx, Map::kInstanceTypeOffset));
+  ASSERT(kSymbolTag != 0);
   __ test(ebx, Immediate(kIsSymbolMask));
   __ j(zero, &slow, not_taken);
 
   // If the receiver is a fast-case object, check the keyed lookup
   // cache. Otherwise probe the dictionary leaving result in ecx.
   __ mov(ebx, FieldOperand(ecx, JSObject::kPropertiesOffset));
   __ cmp(FieldOperand(ebx, HeapObject::kMapOffset),
          Immediate(Factory::hash_table_map()));
   __ j(equal, &probe_dictionary);
 
@@ skipping 1155 matching lines @@
 
   // Do tail-call to runtime routine.
   __ TailCallRuntime(
       ExternalReference(IC_Utility(kSharedStoreIC_ExtendStorage)), 3, 1);
 }
 
 #undef __
 
 
 } }  // namespace v8::internal