Switch optimisation

[XmiliaH]

I would like to add an optimisation to the switch statement that makes the test for the constant cases O(log n) instead of the current O(n).

This would include adding a new upvalue (switch-caches) (name up for debate but should be not accessible from the script) to the chunk.
When a switch is executed for the first time a lookup table is generated and cached under some key in this upvalue table. This lookup table maps values to case-ids and allows to generate a binary search to jump to the cases. In case no constant case matched all the dynamic cases are tested.

Would this be something that is of interest?

[Sainan]

Absolutely. I think my comments in #858 explain pretty well that I am very much in favour of switch blocks being optimised as long as it's Lua bytecode compatible.