[llvm] [VPlan] Run addMiddleCheck before early exit handling. NFC (PR #206244)

[Florian Hahn via llvm-commits]

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@@ -4568,13 +4568,15 @@ static bool handleUncountableExitsWithSideEffects(
   // against the full trip count, since we may be exiting the vector loop early.
   // If we didn't take an early exit, we should get the equivalent of VF from
   // the FirstActiveLane.
-  VPBuilder MiddleBuilder(MiddleVPBB, MiddleVPBB->end());
+  VPBuilder MiddleBuilder(MiddleVPBB->getTerminator());
   VPValue *ScalarIV = MiddleBuilder.createNaryOp(VPInstruction::ExtractLane,
                                                  {Zero, IV}, DebugLoc());
   VPValue *ExitIV = MiddleBuilder.createAdd(ScalarIV, FirstActive);
   VPValue *FullTC =
       MiddleBuilder.createICmp(CmpInst::ICMP_EQ, ExitIV, Plan.getTripCount());
-  MiddleBuilder.createNaryOp(VPInstruction::BranchOnCond, {FullTC});
+  assert(match(MiddleVPBB->getTerminator(), m_BranchOnCond()) &&
+         "Expected BranchOnCond terminator for MiddleVPBB");
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fhahn wrote:

nit: can assert early, before constructing `MiddleBuilder`

https://github.com/llvm/llvm-project/pull/206244