RFR: 8279063: Consolidate push and push_if_necessary in PreservedMarks

[Albert Mingkun Yang]

On Tue, 21 Dec 2021 13:36:04 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> Simple change of cleaning up `PreservedMarks` API.
>> 
>> Test: hotspot_gc
>
> src/hotspot/share/gc/g1/g1FullGCMarker.inline.hpp line 57:
> 
>> 55: 
>> 56:   // Marked by us, preserve if needed.
>> 57:   if (_collector->is_compacting(obj)) {
> 
> I wonder if is_compacting() is actually used (returning false) by any collector. Sounds like it might be a left-over from CMS.

`is_compacting()` returns info in `G1FullCollector::_region_attr_table`. (If I put `assert(false)` inside this `if`, I get an assert failure.)

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PR: https://git.openjdk.java.net/jdk/pull/6909