[llvm] [SROA] Pre-split overlapping move slices within a partition (PR #210061)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic approved this pull request.

I'm a little concerned that the slicing could get out of control in some cases, but I guess the fact that we only do this specifically for load/store ops limits the risk of that.  (If we try to split, for example, `memmove(&a, &a+1, 1000)`, that could become a problem.)

LGTM

https://github.com/llvm/llvm-project/pull/210061