[llvm] [VPlan] Introduce scalar loop header in plan, remove VPLiveOut. (PR #109975)

[via llvm-commits]

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@@ -1054,6 +1064,8 @@ void VPlan::execute(VPTransformState *State) {
   BrInst->insertBefore(MiddleBB->getTerminator());
   MiddleBB->getTerminator()->eraseFromParent();
   State->CFG.DTU.applyUpdates({{DominatorTree::Delete, MiddleBB, ScalarPh}});
+  State->CFG.DTU.applyUpdates(
+      {{DominatorTree::Delete, ScalarPh, ScalarPh->getSingleSuccessor()}});
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ayalz wrote:

Fine, perhaps worth noting that this is the reason for **temporarily** disconnecting scalar preheader from its successor.

https://github.com/llvm/llvm-project/pull/109975