[llvm] [LV] Use ExtractLane(LastActiveLane, V) live outs when tail-folding. (PR #149042)

[David Sherwood via llvm-commits]

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@@ -638,7 +638,12 @@ Value *VPInstruction::generate(VPTransformState &State) {
     llvm_unreachable("should be handled by VPPhi::execute");
   }
   case Instruction::Select: {
-    bool OnlyFirstLaneUsed = vputils::onlyFirstLaneUsed(this);
+    bool OnlyFirstLaneUsed =
+        vputils::onlyFirstLaneUsed(this) ||
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david-arm wrote:

Is this change worth submitting separately? Not sure if it has any effect outside this PR.

https://github.com/llvm/llvm-project/pull/149042