RFR: 8278482: G1: Improve HeapRegion::block_is_obj [v2]

[Thomas Schatzl]

On Sat, 11 Dec 2021 14:46:34 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Adding assertions to `HeapRegion::block_is_obj` and its callers, and removing some dead code based on the assertions.
>> 
>> Test: tier1-5
>
> Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review

Lgtm.

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Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6781