[llvm] [VPlan] Make CanIV part of region. (PR #144803)

[via llvm-commits]

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@@ -3766,6 +3747,9 @@ class LLVM_ABI_FOR_TEST VPRegionBlock : public VPBlockBase {
   /// instances of output IR corresponding to its VPBlockBases.
   bool IsReplicator;
 
+  /// Canonical IV of the (loop) region.
+  VPCanonicalIV *CanIV = nullptr;
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ayalz wrote:

Can a loop region have a null CanIV, or can CanIV indicate whether a region is loop or replicating?

https://github.com/llvm/llvm-project/pull/144803