[VPlan] Set predecessor of DispatchVPBB early (NFC). (#195480)

This allows finding the containing plan earlier, which helps when trying
to print DispatchVPBB in a debugger.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -4162,6 +4162,7 @@ void VPlanTransforms::handleUncountableEarlyExits(VPlan &Plan,
   VPBasicBlock *DispatchVPBB =
       Exits.size() == 1 ? VectorEarlyExitVPBBs[0]
                         : Plan.createVPBasicBlock("vector.early.exit.check");
+  DispatchVPBB->setPredecessors({LatchVPBB});
   VPBuilder DispatchBuilder(DispatchVPBB, DispatchVPBB->begin());
   VPValue *FirstActiveLane = DispatchBuilder.createFirstActiveLane(
       {Combined}, DebugLoc::getUnknown(), "first.active.lane");
@@ -4283,7 +4284,6 @@ void VPlanTransforms::handleUncountableEarlyExits(VPlan &Plan,
                        {IsAnyExitTaken, IsLatchExitTaken}, LatchDL);
   LatchVPBB->clearSuccessors();
   LatchVPBB->setSuccessors({DispatchVPBB, MiddleVPBB, HeaderVPBB});
-  DispatchVPBB->setPredecessors({LatchVPBB});
 }
 
 /// This function tries convert extended in-loop reductions to