Slower loops for vector memory segment access (loop unrolling)

[Radosław Smogura]

Hi all,

I hope you have a good day!

During [1], I’ve noticed that directSegments benchmark is slower then arrayCopy one. However expected behavior is that both benchmarks should produce similar results.

I tracked it to int vs long loops - array copy produces same results when int loop is replaced by long counted loop.

I gathered generated graphs [2] where, first benchmark is unrolled 8 times, while 2nd one (with long loops) 4 times only.

For now I don’t know exact reasons while there’s such difference.

[1] Split foreign vector load and store by null or not null base by rsmogura · Pull Request #711 · openjdk/panama-foreign (github.com)<https://github.com/openjdk/panama-foreign/pull/711>
[2] https://drive.google.com/drive/folders/1gaNz4qwc0e1un6oy7WunTHnYdBdKMIAb?usp=sharing

Kind regards,
Radoslaw Smogura


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