RFR: 8255495: Support CDS Archived Heap for uncompressed oops [v3]

[Thomas Schatzl]

On Mon, 31 Jan 2022 23:57:57 GMT, Calvin Cheung <ccheung at openjdk.org> wrote:

>> This proposed change adds support for uncompressed oops for CDS archived heap. It is needed
>> for supporting archived heap for ZGC in the future. For now, only G1GC is supported with this change.
>> During dump time with compressed oops disabled, the MaxHeapSize is set to 4GB. This is to ensure
>> the offset of any object in the heap from the bottom of the heap is always a 32-bit integer.
>> 
>> Passed CI tiers 1 - 4 and hs-tier7-rt tests.
>> 
>> Preliminary HelloWorld startup perf. improvement:
>> 
>> instr delta =    -68813432    -49.7140%
>> time  delta =      -14.720 ms -20.3599%
>
> Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:
> 
>   code cleanup and added a test case

GC changes look good to me.

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Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/7223