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

[via llvm-commits]

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@@ -10293,11 +10315,15 @@ bool LoopVectorizePass::processLoop(Loop *L) {
     // rarely used is not worth unrolling.
     if (!Checks.hasChecks() && !VF.Width.isScalar())
       DisableRuntimeUnroll = true;
+    LoopRemoved = BestPlan.getScalarPreheader()->getNumPredecessors() == 0;
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ayalz wrote:

This is recorded here instead of asking if BestPlan reaches the scalar loop below (next to early exiting if it doesn't), because it's relevant when vectorizing the main loop only? When also vectorizing the epilog loop, should the we check if BestEpiPlan reaches the scalar loop instead?

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