[llvm] [CycleInfo] Store blocks using Euler tour representation (PR #208614)

[Jay Foad via llvm-commits]

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@@ -79,13 +82,16 @@ template <typename ContextT> class GenericCycle {
   ///       always have the same depth.
   unsigned Depth = 0;
 
+  /// The cycle info that owns this cycle. Used by contains(BlockT*).
+  const GenericCycleInfo<ContextT> *CI = nullptr;
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jayfoad wrote:

Do we really need this? Maybe we could force callers to pass in CI instead, or make them call a method on CI instead of a method on Cycle?

https://github.com/llvm/llvm-project/pull/208614