[llvm] [VPlan] Replace VPRegionBlock with explicit CFG before execute (NFCI). (PR #117506)

[via llvm-commits]

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@@ -424,13 +450,19 @@ void VPBasicBlock::connectToPredecessors(VPTransformState &State) {
   if (ParentLoop && !State.LI->getLoopFor(NewBB))
     ParentLoop->addBasicBlockToLoop(NewBB, *State.LI);
 
+  auto Preds = to_vector(getHierarchicalPredecessors());
+  if (VPBlockUtils::isHeader(this, State.VPDT)) {
+    // There's no block for the latch yet, connect to the preheader only.
+    Preds = {Preds[0]};
+  }
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ayalz wrote:

Can alternatively do:
```suggestion
    Preds = getPredecessors()[0];
  } else {
    Preds = to_vector(getPredecessors());
  }
```

https://github.com/llvm/llvm-project/pull/117506