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

[Vyacheslav Klochkov via llvm-commits]

v-klochkov wrote:

> @v-klochkov Reverting the change due to [a failure](https://lab.llvm.org/buildbot/#/builders/55/builds/4171). This may require some investigation. Here is the [reverting pull request](https://github.com/llvm/llvm-project/pull/119657).

@michalpaszkowski - Thank you for the quick revert of that patch.
I cherry-picked this patch and added extra fix for the memory error: https://github.com/llvm/llvm-project/pull/121861
Please see: https://github.com/llvm/llvm-project/pull/121861#issuecomment-257417626

The error is reproducible only with memory sanitizer. 
Is there a way to run one of post-commit CI bots before the commit there?


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