[llvm] [VPlan] Retain exit conditions and edges in initial VPlan (NFC). (PR #137709)

[via llvm-commits]

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@@ -447,19 +424,21 @@ static void createLoopRegion(VPlan &Plan, VPBlockBase *HeaderVPB) {
   VPBlockBase *Succ = LatchVPBB->getSingleSuccessor();
   assert(LatchVPBB->getNumSuccessors() <= 1 &&
          "Latch has more than one successor");
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ayalz wrote:

```suggestion
  assert(Succ && "Latch expected to be left with a single successor");
```
?

https://github.com/llvm/llvm-project/pull/137709