[llvm] [SandboxVec][BottomUpVec] Add cost estimation and tr-accept-or-revert pass (PR #124620)

[Jorge Gorbe Moya via llvm-commits]

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@@ -92,11 +92,14 @@ class Region {
   /// All the instructions in the Region. Only new instructions generated during
   /// vectorization are part of the Region.
   SetVector<Instruction *> Insts;
+  /// An auxiliary sequence of Instruction-Index pairs.
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slackito wrote:

This needs a better explanation IMHO. Why is an auxiliary sequence needed/useful? At least it should explain what's the initial intended use by the seed collector (described in passing in the commit message for 077d28fbc814fac7ae940f21c010b9ff8d4f40c2), and if you have other examples in mind where it could be useful, it would be nice to mention them here as well.

https://github.com/llvm/llvm-project/pull/124620