[llvm] [CodeGen] Adjust global-split remat heuristic to match LICM (PR #160709)

[Philip Reames via llvm-commits]

preames wrote:

@lukel97 You appear to have good infrastructure for looking at spill/fill impacts, would you mind sanity checking this one just to make sure there's no unexpected negative interactions?  Not expecting any, but well, RegAlloc is famous for the unexpected.  

https://github.com/llvm/llvm-project/pull/160709