[llvm] [AArch64][MachinePipeliner] Add pipeliner support for AArch64 (PR #79589)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

Hello. I agree that so long as it is disabled by default this would be good to get into trunk. It sounds like there are still a number of issues, both performance and correctness, but having the ability to test and adjust it as we go should be useful.

Can I suggest that instead of the option controlling whether enableMachinePipeliner returns true that instead it changes whether the pass is added to the pass pipeline. That should hopefully remove the changes from the pass pipeline, and mean we don't need to pay for the extra analyses when the pass is disabled.

https://github.com/llvm/llvm-project/pull/79589