[llvm] Re-land [Transform][LoadStoreVectorizer] allow redundant in Chain (PR #168135)

[Alexander Kornienko via llvm-commits]

alexfh wrote:

> @cmc-rep this commit causes Clang timeouts compiling some of our code (specifically, compilation time growth from ~20s to more than 15 minutes, after which I gave up waiting, so I can't say whether it's an infinite loop or a superlinear algorithm).
> 
> I'll try to produce a test case, but for now maybe the perf report can give you some clues at what's happening:

Actually, ceba82f862b61396c2321613f544f925aefce015 seems to fix the problem.

https://github.com/llvm/llvm-project/pull/168135