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

[via llvm-commits]

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@@ -8957,7 +8941,14 @@ static void addLiveOutsForFirstOrderRecurrences(
         VPInstruction::ResumePhi, {Resume, FOR->getStartValue()}, {},
         "scalar.recur.init");
     auto *FORPhi = cast<PHINode>(FOR->getUnderlyingInstr());
-    Plan.addLiveOut(FORPhi, ResumePhiRecipe);
+    for (VPRecipeBase &R :
+         *cast<VPIRBasicBlock>(ScalarPHVPBB->getSingleSuccessor())) {
+      auto *IRI = cast<VPIRInstruction>(&R);
+      if (&IRI->getInstruction() == FORPhi) {
+        IRI->addOperand(ResumePhiRecipe);
+        break;
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ayalz wrote:

Worth asserting this took place, say by having the loop set IRI which is added an operand afterwards?

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