[llvm] [SLP] More OOP to simplify vectorizeStores() (NFC) (PR #134605)

[Gaëtan Bossu via llvm-commits]

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@@ -20694,52 +20735,34 @@ bool SLPVectorizerPass::vectorizeStores(
   // dependencies and no need to waste compile time to try to vectorize them.
   // - Try to vectorize the sequence {1, {1, 0}, {3, 2}}.
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gbossu wrote:

Now that `FillStoresSet()` is more concise and has simpler control flow, I'm wondering if this long comment on top of it could be shortened. What do you think @alexey-bataev?

https://github.com/llvm/llvm-project/pull/134605