[llvm] [MCA] Enable customization of individual instructions (PR #155420)

[Min-Yih Hsu via llvm-commits]

https://github.com/mshockwave commented:

Could you add another new callback in `InstrumentManager` to implement the customizer, and move the parsing logics of `LLVM-MCA-LATENCY` from CodeRegionGenerator.* to InstrumentManager (either putting it in X86's custom behavior or in InstrumentManager's base implementation) because InstrumentManager was created exactly for supporting custom annotations like `LLVM-MCA-LATENCY`.

https://github.com/llvm/llvm-project/pull/155420