Valhalla/MVT microbenchmarks (first benchmarks and first results)

[Roland Westrelin]

> Also such slow warmup can't be explained simply by slower 
> reachingcompilation thresholds.
> Derived value types (with counted loops) are ~3x-4x times slower than 
> boxed types analogues in the interpreter, but time to performance is 
> ~20x-40x times worse.

You're right. I found the slow down is related to changes to the calling
convention.
With -XX:-ValueTypePassFieldsAsArgs -XX:-ValueTypeReturnedAsFields, the
warmup is a lot faster. -XX:-ValueTypeReturnedAsFields is actually the
one that makes the biggest difference. I'm experimenting with ways to
speed things up.

Roland.