[llvm] [SLP] Use named structs in vectorizeStores() (NFC) (PR #132781)

[Gaëtan Bossu via llvm-commits]

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@@ -19994,6 +19994,38 @@ static bool checkTreeSizes(ArrayRef<std::pair<unsigned, unsigned>> Sizes,
   return Dev * 96 / (Mean * Mean) == 0;
 }
 
+namespace {
+
+/// A group of instructions that we'll try to bundle together using vector ops.
+/// They are ordered using the signed distance of their address operand to the
+/// address of this group's BaseInstr.
+struct RelatedStoreInsts {
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gbossu wrote:

The reason I kept this public is to avoid mixing struct/class semantics, because the `Instrs` attribute will still be public. I had a WIP change locally to encapsulate more within `RelatedStoreInsts` and make it truly own its attributes. However, that requires a lot of reorganization and I'm not happy with the result I got at that point.

TLDR: I'll make at least `BaseInstrIdx` private, I agree it's better.

https://github.com/llvm/llvm-project/pull/132781