[llvm] [KeyInstr] Fully support mixed key/non-key inlining modes (PR #144103)

[Jeremy Morse via llvm-commits]

https://github.com/jmorse commented:

Is it not feasible to check the optimisation mode here, avoiding the performance hit to O0? While there may be frontend/LTO reasons why key-and-non-key instructions could be mixed, one of the major reasons why KIs is needed is due to instruction-schedulers shuffling instructions around, which doesn't happen at O0. We could reasonably say "Key instruction is off at O0 anyway, we're not honouring it if you managed to convince something to be inlined into an optnone function".

If that's not alright, IMO it's OK to once again let O0 pay the price -- it's increasing from a low base anyway. Plus, the MC-layer optimisations we're getting up shortly gives it a 1.2% speedup.

https://github.com/llvm/llvm-project/pull/144103