[llvm] [VPlan] Add VPIRWrapperBlock, use to model pre-preheader. (PR #93398)

[via llvm-commits]

================
@@ -442,6 +442,58 @@ VPBasicBlock::createEmptyBasicBlock(VPTransformState::CFGState &CFG) {
   return NewBB;
 }
 
+void VPIRWrapperBlock::execute(VPTransformState *State) {
+  for (VPBlockBase *PredVPBlock : getHierarchicalPredecessors()) {
----------------
ayalz wrote:

Pre-preheader block has no predecessors, can assert, next to asserting it has no successors (currently).

https://github.com/llvm/llvm-project/pull/93398