[llvm] [VPlan] Simplify Plan's entry in removeBranchOnConst. (PR #154510)

[Florian Hahn via llvm-commits]

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@@ -7220,6 +7223,12 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
   VPlanTransforms::optimizeForVFAndUF(BestVPlan, BestVF, BestUF, PSE);
   VPlanTransforms::simplifyRecipes(BestVPlan);
   VPlanTransforms::removeBranchOnConst(BestVPlan);
+  if (BestVPlan.getEntry()->getSingleSuccessor() ==
+      BestVPlan.getScalarPreheader()) {
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fhahn wrote:

Yep, added an analysis remark. I am not sure if missed-vectorization would be accurate, because this is for cases where we would create a dead vector loop and should not even try to vectorize.

https://github.com/llvm/llvm-project/pull/154510