[llvm] Greedy: Make trySplitAroundHintReg try to match hints with subreg copies (PR #160294)

[Philip Reames via llvm-commits]

https://github.com/preames approved this pull request.

LGTM

For the record, not convinced the sub-reg handling is optimal here, but I think this is an improvement over the prior code, so I'm fine with that being addressed later on.  

https://github.com/llvm/llvm-project/pull/160294