RFR (S) 8227766: CheckUnhandledOops is broken in MemAllocator

[coleen.phillimore at oracle.com]

Due to some concerns about MemAllocator performance, and to only create 
handles when needed, I have retested smaller change:

open webrev at http://cr.openjdk.java.net/~coleenp/2019/8227766.02/webrev

Coleen

On 7/17/19 10:49 AM, coleen.phillimore at oracle.com wrote:
> Summary: Save oop created in handle more eagerly, so 
> CheckUnhandledOops doesn't bash it.
>
> Also added a test for the case that was failing.  There were a couple 
> of changes needed to compile CHECK_UNHANDLED_OOPS with slowdebug, but 
> I reverted the makefile changes for doing that because I don't think 
> we want it for slowdebug.
> Lastly, made some changes to make CheckUnhandledOops easier to debug, 
> and removed an unnecessary clearing, since it's also done in the 
> transition.
>
> Tested with hs-tier1-3 with -XX:+CheckUnhandledOops and without.
>
> open webrev at http://cr.openjdk.java.net/~coleenp/2019/8227766.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8227766
>
> Thanks,
> Coleen