RFR: Bulk backports to sh/jdk11 2020-04-20

[Roman Kennke]

>> This backports the following changes from jdk/jdk:
>>
>>   8242316: Shenandoah: Turn NULL-check into assert in SATB slow-path entry
>>   8242301: Shenandoah: Inline LRB runtime call
>>   8242273: Shenandoah: accept either SATB or IU barriers, but not both
>>   8242271: Shenandoah: add test to verify GC mode unlock
>>   8242054: Shenandoah: New incremental-update mode
>>   8242217: Shenandoah: Enable GC mode to be diagnostic/experimental and
>> have a name
>>   8242130: Shenandoah: Simplify arraycopy-barrier dispatching
>>   8241700: Shenandoah: Fold ShenandoahKeepAliveBarrier flag into
>> ShenandoahSATBBarrier
>>   8241675: Shenandoah: assert(n->outcnt() > 0) at
>> shenandoahSupport.cpp:2858 with
>> java/util/Collections/FindSubList.java
>>
>>
>> http://cr.openjdk.java.net/~rkennke/backport-shjdk11-2020-04-20/webrev.00/
> 
> Looks good!
> 
> Please make sure to include 8243008.

Right. Added here:
http://cr.openjdk.java.net/~rkennke/backport-shjdk11-2020-04-20/webrev.01.diff/

Full webrev:
http://cr.openjdk.java.net/~rkennke/backport-shjdk11-2020-04-20/webrev.01/

> Also, build without PCH and on AArch64?

yes. Both are looking fine.

Roman