[llvm] [VPlan] Manage Sentinel value for FindLastIV in VPlan. (PR #142291)

[via llvm-commits]

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@@ -9235,9 +9237,11 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
     if (RecurrenceDescriptor::isFindLastIVRecurrenceKind(
             RdxDesc.getRecurrenceKind())) {
       VPValue *Start = PhiR->getStartValue();
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ayalz wrote:

`VPValue *Sentinel = ...`

https://github.com/llvm/llvm-project/pull/142291