[llvm] [VPlan] Add exit phi operands during initial construction (NFC). (PR #136455)

[via llvm-commits]

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@@ -9421,7 +9417,7 @@ addUsersInExitBlocks(VPlan &Plan,
            ExitIRI->getParent()->getSinglePredecessor() == MiddleVPBB &&
            "exit values from early exits must be fixed when branch to "
            "early-exit is added");
-    ExitIRI->extractLastLaneOfOperand(B);
+    ExitIRI->extractLastLaneOfFirstOperand(B);
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ayalz wrote:

Independent: `addUsersInExitBlocks()` --> `addExtractsToExitUsers()`? This method introduces extracts for exit users of a single (latch) exit block, which are expected to be single operand VPIRPhi's, rather than adds users in multiple/all exit blocks. Drop "Add exit values to \p Plan."?

https://github.com/llvm/llvm-project/pull/136455