[llvm] [LoadStoreVectorizer] Postprocess and merge equivalence classes (PR #114501)

[Vyacheslav Klochkov via llvm-commits]

v-klochkov wrote:

> Can you add a case that's more representative? You can try llvm-reduce to get a sample

@arsenm - Matt - Please take a look at 1 extra LIT case here: https://github.com/llvm/llvm-project/pull/114501/commits/7b07f8cf1e9ad1345bcc97fe9c99d1bb7590d819

llvm-reduce is a great tool, I played with it; In this case though, it turned out to be easier to copy the interesting STOREs operations and minimally re-build missing IRs around them to show the idea of the context the STOREs in the original workload were placed into.
It is easy to get underlying objects that 1 indirection level apart from each other when the 1st store in a sequence is a store indexed by `index` and consequent stores indexed by `index` + `some_const`, which gives extra depth/level created by getelementptr `index + some_const`.

https://github.com/llvm/llvm-project/pull/114501