RFR: 8258382: Fix optimization-unstable code involving pointer overflow [v2]

[Hao Sun]

On Fri, 1 Jan 2021 03:49:16 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Marked as reviewed by kbarrett (Reviewer).
>
> Thanks for splitting up the changes.  The GC changes look good.

@kimbarrett thanks for your review.

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

PR: https://git.openjdk.java.net/jdk/pull/1886