[llvm] [VPlan] Model branch cond to enter scalar epilogue in VPlan. (PR #92651)

[via llvm-commits]

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@@ -448,11 +449,15 @@ VPBasicBlock::createEmptyBasicBlock(VPTransformState::CFGState &CFG) {
 }
 
 void VPIRBasicBlock::execute(VPTransformState *State) {
-  assert(getHierarchicalSuccessors().empty() &&
-         "VPIRBasicBlock cannot have successors at the moment");
-
+  assert(getHierarchicalSuccessors().size() <= 2);
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ayalz wrote:

```suggestion
  assert(getHierarchicalSuccessors().size() <= 2 &&
           "VPIRBasicBlock can have at most two successors at the moment");
```
can any block have more than 2? ...

https://github.com/llvm/llvm-project/pull/92651