RFR: 8177086: java.lang.reflect.AccessibleObject::canAccess should share access cache with internal method ::checkAccess

[Peter Levart]

Hi,

Module system implementation refresh 2017/2 (JDK-8173393) introduced new 
API method AccessibleObject::canAccess which can be used to test if the 
caller has access to the reflected member (with possible target object 
argument for instance members). The implementation of this method, after 
some parameter validation checks, delegates directly to 
jdk.internal.reflect.Reflection::verifyMemberAccess. This is 
sub-optimal. Co-located internal method AccessibleObject::checkAccess 
also delegates to Reflection::verifyMemberAccess, but it also uses a 
one-element cache of access-check decision, which greatly speeds up 
repeated calls by the same caller to the same reflected member. The 
cache could be shared between those two methods which would improve 
performance of code idioms like this:

if (member.canAccess(target) || member.trySetAccessible()) {
   member.invoke(....);
     ...
} else {
    ...
}

Here's a proposed patch to improve this new method's performance:

http://cr.openjdk.java.net/~plevart/jdk9-dev/8177086_AccessibleObject.canAccess.cache/webrev.01/

The corresponding jira issue is:

https://bugs.openjdk.java.net/browse/JDK-8177086


I don't know whether this should go to jdk9 or perhaps later to jdk9u, 
since this is new API that only came into existence 1 month ago and this 
patch improves its implementation. Should It perhaps go to jake repo 
1st? Presented patch is made against current jdk9/jdk repo.


Regards, Peter