RFR: 8329331: Intrinsify Unsafe::setMemory [v6]

[Francesco Nigro]

On Sun, 7 Apr 2024 01:49:01 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Scott Gibbons has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Oops
>
> I went ahead and tried a pure-Java implementation, and it is faster for small sizes (up to 8) and only about 1.5x slower for larger sizes, so that might make for an interesting fallback if there is no customized assembler implementation available or if the size is known to me small.
> 
> Ideally, I think we would want C2 to be more aware of setMemory stores, so that it can remove redundant stores, like it does with InitializeNode.

@dean-long in my old PR I have done the same, choosing a (not yet) configurable cutoff value. 

See https://github.com/openjdk/jdk/pull/16760

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PR Comment: https://git.openjdk.org/jdk/pull/18555#issuecomment-2041314429