[vectorIntrinsics] RFR: Optimize mem barriers for ByteBuffer cases [v6]

[Radoslaw Smogura]

On Tue, 3 Aug 2021 18:52:15 GMT, Radoslaw Smogura <github.com+7535718+rsmogura at openjdk.org> wrote:

>> # Description
>> This change tries to remove mem bars for byte buffer cases.
>> 
>> Previously mem bars were inserted almost unconditionally if attemp to native memory acees where detected. This patch tries to follow up inline_unsafe_access and insert bar only if can't determine if it's heap or off-heap (type missmatch cases are not ported).
>> 
>> # Testing
>> Memory tests should include rollbacking JDK changes, and leaving only hotspot, as intrinsics should be well guarded
>> 
>> # Notes
>> Polluted cases to be addressed later
>> 
>> # Benchmarks
>> 
>> Benchmark                                (size)  Mode  Cnt    Score   Error  Units
>> ByteBufferVectorAccess.arrays              1024  avgt   10   12.585 ? 0.409  ns/op
>> ByteBufferVectorAccess.directBuffers       1024  avgt   10   19.962 ? 0.080  ns/op
>> ByteBufferVectorAccess.heapBuffers         1024  avgt   10   15.878 ? 0.187  ns/op
>> ByteBufferVectorAccess.pollutedBuffers2    1024  avgt   10  123.702 ? 0.723  ns/op
>> ByteBufferVectorAccess.pollutedBuffers3    1024  avgt   10  223.928 ? 1.906  ns/op
>> 
>> Before
>> 
>> Benchmark                                (size)  Mode  Cnt    Score   Error  Units
>> ByteBufferVectorAccess.arrays              1024  avgt   10   14.730 ? 0.061  ns/op
>> ByteBufferVectorAccess.directBuffers       1024  avgt   10   77.707 ? 4.867  ns/op
>> ByteBufferVectorAccess.heapBuffers         1024  avgt   10   76.530 ? 1.076  ns/op
>> ByteBufferVectorAccess.pollutedBuffers2    1024  avgt   10  143.331 ? 1.096  ns/op
>> ByteBufferVectorAccess.pollutedBuffers3    1024  avgt   10  286.645 ? 3.444  ns/op
>
> Radoslaw Smogura has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Benchamk fixes

Hi all, I think that for this PR, I rather don't want to push more changes. It already stepped out from the original concern of optimizing mem-bars, to optimizing polluted cases.

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PR: https://git.openjdk.java.net/panama-vector/pull/104