[llvm] [VPlan] Create header phi recipes after initial scalar optimizations. (PR #200920)

[Ramkumar Ramachandra via llvm-commits]

================
@@ -962,6 +966,9 @@ bool VPlanTransforms::createHeaderPhiRecipes(
   if (!tryToSinkOrHoistRecurrenceUsers(HeaderVPBB, VPDT))
     return false;
 
+  if (range_size(HeaderVPBB->phis()) !=
+      range_size(Plan.getScalarPreheader()->phis()))
+    return true;
----------------
artagnon wrote:

Could you kindly explain when this happens?

https://github.com/llvm/llvm-project/pull/200920