RFR: 8170455: C2: Access to [].clone from interfaces fails

[Jamsheed C m]

Hi,

Vladimir Ivanov suggested a few changes in webrev.00

1)  to move class accessibility check in lookup inside assert, as it is 
already being done by caller once.

2)  to remove changes in resolve_invoke as it is not really required.

revised webrev: http://cr.openjdk.java.net/~jcm/8170455/webrev.01/

Thanks a lot for detailed review Vladimir.

Best Regards,

Jamsheed


On 1/31/2017 3:55 PM, Jamsheed C m wrote:
> Hi,
>
> Array type are treated as Object type in Compiler  (see [1]) and 
> lookup happens in Object Class in compiler interface. This used to 
> work before default method got introduced. with default methods 
> protected Object methods are inaccessible from interface , so lookup 
> fails,   caller method always deopt as unloaded and decompile in C2. 
> This causes considerable degradation in performance.
>
> Fix: array types are directly passed to lookup code(fix), all other 
> code is kept as it is.
>
> bug id: https://bugs.openjdk.java.net/browse/JDK-8170455
>
> webrev:  http://cr.openjdk.java.net/~jcm/8170455/webrev.00/
>
> Best Regards,
>
> Jamsheed
>
> [1]
>
> ciInstanceKlass* 
> ciEnv::get_instance_klass_for_declared_method_holder(ciKlass* 
> method_holder) {
>   // For the case of <array>.clone(), the method holder can be a 
> ciArrayKlass
>   // instead of a ciInstanceKlass.  For that case simply pretend that the
>   // declared holder is Object.clone since that's where the call will 
> bottom out.
>   // A more correct fix would trickle out through many interfaces in CI,
>   // requiring ciInstanceKlass* to become ciKlass* and many more 
> places would
>   // require checks to make sure the expected type was found. Given 
> that this
>   // only occurs for clone() the more extensive fix seems like 
> overkill so
>   // instead we simply smear the array type into Object.
>
>
>
>
>