[jdk11u] RFR: 8229258: Backport patch from JDK 14 to allow building with Clang 13

[VVD]

On Sun, 19 Dec 2021 02:55:01 GMT, Campbell Jones <duke at openjdk.org> wrote:

> This patch backports changes from JDK14 commit ae5615c6142a4dc0d9033462f4880d7b3c127e26. It does not rename the class to markWord as the original patch does, but instead converts markOop to a markWord equivalent in-place. This patch allows the JDK to be built with Clang 13, as it avoids undefined behavior. 
> 
> See the following for more information:
> - https://bugs.openjdk.java.net/browse/JDK-8229258
> - https://urldefense.com/v3/__https://bugs.gentoo.org/817995__;!!ACWV5N9M2RV99hQ!JeKuzOUjUKcqK2KjicutvUnTeA97j6y_ggz6TKOMM5lwjMyvZgcXSOXUUWODwU4sCBdfOPLbASQeVSakpR-Abvs$ 
> - https://mail.openjdk.java.net/pipermail/hotspot-dev/2019-July/038704.html
> - https://mail.openjdk.java.net/pipermail/hotspot-dev/2019-July/038712.html
> - https://urldefense.com/v3/__https://reviews.llvm.org/D99790*2678384__;Iw!!ACWV5N9M2RV99hQ!JeKuzOUjUKcqK2KjicutvUnTeA97j6y_ggz6TKOMM5lwjMyvZgcXSOXUUWODwU4sCBdfOPLbASQeVSakLSpnqXc$ 

Check this patch, please: https://urldefense.com/v3/__https://github.com/battleblow/jdk11u/commit/305a68a90c722aa7a7b75589e24d5b5d554c96c1__;!!ACWV5N9M2RV99hQ!JeKuzOUjUKcqK2KjicutvUnTeA97j6y_ggz6TKOMM5lwjMyvZgcXSOXUUWODwU4sCBdfOPLbASQeVSaktgtAaec$ 

-------------

PR: https://git.openjdk.org/jdk11u/pull/23