RFR: 8324649: Shenandoah: replace implementation of free set [v14]

[Kelvin Nilsen]

On Wed, 10 Apr 2024 11:44:12 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> I'm going to add the following comment at the top of shenandoahFreeSet.hpp:
>> 
>> // The API and internal implementation of ShenandoahSimpleBitMap and ShenandoahRegionPartitions use ssize_t to                      
>> // represent index, even though index is "inherently" unsigned.  There are two reasons for this choice:                             
>> //  1. We use -1 as a sentinel value to represent empty partitions.  This same value may be used to represent                       
>> //     failure to find a previous set bit or previous range of set bits.                                                            
>> //  2. Certain loops are written most naturally if the iterator, which may hold the sentinel -1 value, can be                       
>> //     declared as signed and the terminating condition can be < 0.
>
> Please use types, method signatures and keep structure similar to bitMap.hpp, which use idx_t, which is a size_t (see e.g. BitMap::count_one_bits()).

I am using idx_t, defined here to be ssize_t, as discussed in comments.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17561#discussion_r1599095492