[foreign-memaccess+abi] RFR: Add benchmarks to MemorySegmentVsBits [v2]

[Roland Westrelin]

On Wed, 4 Jan 2023 08:00:15 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> This PR proposes the addition of some benchmarks, for example using a LonBuffer and a VarHandle.
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Change to big endian for some variants

I've been looking at some of the performance anomalies with these benchmarks. I now have a collection of c2 changes, mostly tweaks, so they perform better. I filed a number of bugs for them:
https://bugs.openjdk.org/browse/JDK-8300256
https://bugs.openjdk.org/browse/JDK-8300257
https://bugs.openjdk.org/browse/JDK-8300258
https://bugs.openjdk.org/browse/JDK-8300262
https://bugs.openjdk.org/browse/JDK-8300263

I will work on getting them fixed.

I also filed a library bug:
https://bugs.openjdk.org/browse/JDK-8299982

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PR: https://git.openjdk.org/panama-foreign/pull/762