Request for review 7177409: Perf regression in JVM_GetClassDeclaredFields after generic signature changes

[Jiangli Zhou]

Hi,

Please review the following webrev that address the performance 
regression in JVM_GetClassDeclaredFields with very large class.

   http://cr.openjdk.java.net/~jiangli/7177409/webrev.00/

In fieldDescriptor::generic_signature(), it now returns NULL immediately 
if the access_flags indicates the field has no generic signature. This 
avoids iterating though the fields unnecessarily. Mikael Gerdin has 
confirmed the change resolves the performance issue for  
JVM_GetClassDeclaredFields (thanks, Mikael!).

Thanks,

Jiangli