I am currently working on Jikes and performance is a concern for me. I realize that there is an O3 level out there but by default being disabled. Could some experts comment on why this decision is made? Is this because O3 is too costly, at its early age, or something else? And if I may ask, do other commercial JVM, like Hotspot, do those O3 opts, like SSA and loop-related stuff by default? By the way, I tried to enable O3 but then failed in building the VM. Is this a known issue?

Thank you.

- Lei