[llvm] [SystemZ] Add a SystemZ specific pre-RA scheduling strategy. (PR #135076)

[Jonas Paulsson via llvm-commits]

JonPsson1 wrote:

A patch with scripts that I have been working with as a tool for developing this strategy can be found here: https://github.com/llvm/llvm-project/pull/136483.

@atrick Any comments from you (and others ofc) would be very welcome before committing this. Are there any "no-no":s in this strategy - for instance related to compile time? This strategy is now at a good point, but that doesn't mean that things can get
  better. Do you have any ideas at this point that migh be worth trying?

@lhames 

https://github.com/llvm/llvm-project/pull/135076