Opt-in for trivial native method calls

[Felix Cravic]

Hello, coming here after a recommendation from reddit [0] I want to pitch my wish for the Linker API to support "trival" native function.
My benchmark showed an average latency of around 6ns when calling a native method, which is more than fine most of the time, but fall short for inexpensive calls.

To give a relevant example that could take advantage of such feature, my current toy project [1] involve making the JVM version of Unity's burst compiler [2] which consist in JIT compiling JVM bytecode using LLVM with the hope of getting better performance for highly specialized code (custom intrinsics, stack allocation, value class without valhalla, other fanciness...). And while the calling latency does not make it impossible, it does make it inefficient for taking advantage of specialized instructions (that may not be available in the JDK api) and relatively small methods that could still outperform hotspot equivalent.

I definitely agree that my situation is not the most common (I am responsible for all the native methods, generate class dynamically to create the static method handles) but giving access to low-level tweaks seem like a great solution to me. I am also not sure of what are the tradeoffs of these trivial methods (is it only a matter of safepoint?) so I would be happy to get more technical details.

Thanks!

[0] - https://www.reddit.com/r/java/comments/v33d44/panama_foreign_function_overhead_how_can_it_be/
[1] - https://github.com/TheMode/Spe
[2] - https://docs.unity3d.com/Packages/com.unity.burst@0.2-preview.20/manual/index.html