[llvm] [VPlan] Run initial recipe simplification on VPlan0. (PR #176828)

[Ramkumar Ramachandra via llvm-commits]

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@@ -2173,6 +2185,11 @@ static bool
 sinkRecurrenceUsersAfterPrevious(VPFirstOrderRecurrencePHIRecipe *FOR,
                                  VPRecipeBase *Previous,
                                  VPDominatorTree &VPDT) {
+  // If Previous is a live-in (no defining recipe), it naturally dominates all
+  // recipes in the loop, so no sinking is needed.
+  if (!Previous)
+    return true;
+
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artagnon wrote:

Hm, how is this change related?

https://github.com/llvm/llvm-project/pull/176828