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

[via llvm-commits]

================
@@ -2501,35 +2501,41 @@ void VPlanTransforms::handleUncountableEarlyExit(
     if (!ExitIRI)
       break;
 
-    PHINode &ExitPhi = ExitIRI->getIRPhi();
-    VPValue *IncomingFromEarlyExit = RecipeBuilder.getVPValueOrAddLiveIn(
-        ExitPhi.getIncomingValueForBlock(UncountableExitingBlock));
-
+    unsigned EarlyExitIdx = 0;
----------------
ayalz wrote:

```suggestion
    // By default, assume early exit operand is first, e.g., when the two exit blocks are distinct - VPEarlyExitBlock has a single predecessor.
    unsigned EarlyExitIdx = 0;
```

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