Former Azul employee here

Absolutely correct that LLVM is a fair amount slower than C1 or C2. Azul augmented our JITs with a compilation recording & replay mechanism to combat the general start-up problems posed by JITs (including Falcon).

For those who are curious, here's my presentation on the topic: https://2018.jpoint.ru/en/talks/63npsyjpokmukqsag80oia/.

That’s not really accurate. It has strict requirements about stack traversal required to appropriately trace memory roots. This is incidental to JIT vs AOT.