RFR(XS): 8143897 :Weblogic12medrec assert(handler_address == SharedRuntime::compute_compiled_exc_handler(nm, pc, exception, force_unwind, true)) failed: Must be the same

[Jamsheed C m]

Hi,

Please review the fix made for issue

bug url: https://bugs.openjdk.java.net/browse/JDK-8143897
web rev: http://cr.openjdk.java.net/~thartmann/8143897/webrev.00/

Unit tests: As its hard, none

Other tests: jprt.

Description of the issue:
A valid pc match in exception cache returning an invalid handler makes 
assert to fail.
This happens as  ExceptionCache reads are lock free access.

As a fix for this i have put a storestore mem barrier before the count 
is updated.

Best Regards,
Jamsheed