RFR Backport: 8166607: G1 needs klass_or_null_acquire

[Yangfei (Felix)]

Hi,

As mentioned in [1], JDK-8160369 have not been backported to JDK8u. This is necessary for RMO architectures like aarch64.

JDK- 8166607 is a subtask of JDK-8160369.
Original bug: https://bugs.openjdk.java.net/browse/JDK-8166607 
Original patch: http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/1a33f585a889 
Original RFR thread: https://mail.openjdk.java.net/pipermail/hotspot-dev/2016-September/024687.html 

The original patch for JDK- 8166607 does not apply cleanly to jdk8u-dev due to path and code refactoring work in jdk9+.

Webrev for 8u:
    http://cr.openjdk.java.net/~fyang/8166607-8u/webrev.00/

Except for path adaption, two extra changes are needed here:
1. Use hr->isHumongous() instead of hr->is_humongous(). Function name for isHumongous() and friends are normalized by 8058495.
2. Wrap error messages used in assertion using err_msg.

Performed full jtreg test with release build both on aarch64-linux and x86_64-linux platforms.

OK to backport?

Thanks,
Felix

[1] https://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2020-July/030313.html