RFR: 8329331: Intrinsify Unsafe::setMemory [v9]

[Scott Gibbons]

On Thu, 11 Apr 2024 18:17:01 GMT, Scott Gibbons <sgibbons at openjdk.org> wrote:

>> This code makes an intrinsic stub for `Unsafe::setMemory` for x86_64.  See [this PR](https://github.com/openjdk/jdk/pull/16760) for discussion around this change.
>> 
>> Overall, making this an intrinsic improves overall performance of `Unsafe::setMemory` by up to 4x for all buffer sizes.
>> 
>> Tested with tier-1 (and full CI).  I've added a table of the before and after numbers for the JMH I ran (`MemorySegmentZeroUnsafe`).
>> 
>> [setMemoryBM.txt](https://github.com/openjdk/jdk/files/14808974/setMemoryBM.txt)
>
> Scott Gibbons has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Set memory test (#16)
>   
>   Add framework for other platforms.  Moved fill_to_memory_atomic back to the .cpp from the .hpp in order to get 32-bit fixed.

I added the framework for setting unsafe access marks within all platforms, and fixed a bug with the Linux 32-bit runtime tests.  Adding stub intrinsic for setMemory0 for other platforms should be easier now.

Passes CI testing.

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PR Comment: https://git.openjdk.org/jdk/pull/18555#issuecomment-2050267842