[llvm] [Sched] Skip MemOp with unknown size when clustering (PR #118443)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

Code that will generate unknown size `LocationSize`:
https://github.com/llvm/llvm-project/blob/c1ad064dd3b9a1bf503bb8cd6d0d0418a05d10e8/llvm/lib/CodeGen/ModuloSchedule.cpp#L962-L994

https://github.com/llvm/llvm-project/pull/118443