[llvm] [LoadStoreVectorizer] Allow vectorization of partially overlapped vector-stores (PR #169946)

[Gang Chen via llvm-commits]

cmc-rep wrote:

I will put this PR on hold, and work on this one later. I think the clean way of solving this problem is that we can remove all the redundant part for store-chain during splitChainByContiguity. That takes some work. I need to attend to some other work right now. 

https://github.com/llvm/llvm-project/pull/169946