Split-If is quite complex and it would benefit to add "TraceSplitIf" flag to get more information about the optimisation. Note that JDK-8330469 removed the "PrintOpto && VerifyLoopOptimizations" flag combination guarding some logging information in Split-If as this flag combination is not used in practice.

Interesting things to log (not an exclusive list):
- If node which is split through
- Nodes being cloned up (split_up())
- Nodes being cloned down (clone_*_down())