RFR: 8327571: Parallel: Remove redundant operation in PSParallelCompact::clear_data_covering_space

[Albert Mingkun Yang]

On Thu, 7 Mar 2024 13:39:39 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> Simple removing redundant code.
>
> src/hotspot/share/gc/parallel/psParallelCompact.cpp line 901:
> 
>> 899: 
>> 900:   const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
>> 901:   const idx_t end_bit = _mark_bitmap.addr_to_bit(top);
> 
> The method `addr_to_bit` invokes the method `words_to_bits`, so the result is always aligned. Is my understanding right?

Don't think so. The alignment is about `#bits % BitsPerWord == 0`. `clear_range` does not require alignment. (You can try `assert(_mark_bitmap.align_range_end(end_bit) == end_bit, "inv");`, and that should fail.)

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PR Review Comment: https://git.openjdk.org/jdk/pull/18152#discussion_r1516186857