RFR: 8324649: Shenandoah: replace implementation of free set [v53]

[Kelvin Nilsen]

On Fri, 3 May 2024 16:07:43 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> Kelvin Nilsen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 114 commits:
>> 
>>  - Merge remote-tracking branch 'origin/master' into restructure-free-set
>>  - Merge branch 'openjdk:master' into master
>>  - Merge branch 'openjdk:master' into master
>>  - Remove unnecessary call to update_watermark
>>  - Assert progress on find_next and find_prev
>>  - Simplify partition_membership_name by code reuse
>>  - Simplify by combining implemnetations of shrink_interval functions
>>  - Fix NumPartition type
>>    
>>    Beautify the code by changing type of NumPartitions and adding Int and
>>    UInt forms of NumPartitions.
>>  - Refinements to support zero-build compiles
>>  - Fix whitespace
>>  - ... and 104 more: https://git.openjdk.org/jdk/compare/a863ef5d...d6e3546c
>
> src/hotspot/share/gc/shenandoah/shenandoahSimpleBitMap.cpp line 52:
> 
>> 50:   if ((element_bits & mask) == mask) {
>> 51:     size_t counted_ones = BitsPerWord - bit_number;
>> 52:     return counted_ones + count_leading_ones(start_idx - counted_ones);
> 
> If you have a long string of 1s, then recursively calling itself might blow up the stack. I guess writing it in an iterative way might be better (and perhaps perform better).

Thanks.  Replacing recursion with iteration.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/17561#discussion_r1591600333