[llvm] [AArch64] Initial Olympus scheduling model. (PR #171607)

[Sjoerd Meijer via llvm-commits]

https://github.com/sjoerdmeijer commented:

Sharing a first high level question about the AArch64 changes while I am now looking at the actual sched model...

https://github.com/llvm/llvm-project/pull/171607