[llvm] [LoopInterchange] Stop performing unprofitable interchange (PR #127473)

[Sjoerd Meijer via llvm-commits]

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@@ -497,11 +498,13 @@ struct LoopInterchange {
     // indicates the loop should be placed as the innermost loop.
     //
     // For the old pass manager CacheCost would be null.
-    DenseMap<const Loop *, unsigned> CostMap;
+    std::optional<CostMapTy> CostMap = std::nullopt;
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sjoerdmeijer wrote:

You've also added a `CostMap` to the `LoopInterchangeProfitability` class, it's not yet clear to me if we need both.

https://github.com/llvm/llvm-project/pull/127473