[llvm] [LV] Transform to handle exits in the scalar loop (PR #148626)

[Graham Hunter via llvm-commits]

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@@ -4182,6 +4182,14 @@ class VPlan {
   /// VPlan is destroyed.
   SmallVector<VPBlockBase *> CreatedBlocks;
 
+  /// The entry block in a vplan, which may be a check block that needs to
+  /// be wired up in the right place with existing check blocks.
+  std::optional<VPBasicBlock *> EarlyExitPreheader;
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huntergr-arm wrote:

Ok; I like being able to ensure a check for presence, but since C++ doesn't support optional<T&> yet we can't do it cleanly.

https://github.com/llvm/llvm-project/pull/148626