RFR: 8305896: Alternative full GC forwarding [v25]

[Roman Kennke]

On Wed, 3 May 2023 21:35:03 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix type narrowing
>
> src/hotspot/share/gc/shared/slidingForwarding.inline.hpp line 59:
> 
>> 57:     // Primary is free
>> 58:     _bases_table[base_idx] = to_region_base;
>> 59:   } else if (_bases_table[base_idx] == to_region_base) {
> 
> This probably won't help at all with performance, but I would kind of put the checks for the common cases where the table values are set (particularly the first one) first (I may be wrong about whether this is possible).
> The `UNUSED_BASE` values in the tables will be encountered exactly once...

I believe we can safely swap the UNUSED with the primary check. I'll do that.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13582#discussion_r1184573418