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

[via llvm-commits]

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@@ -851,6 +879,23 @@ void VPRegionBlock::print(raw_ostream &O, const Twine &Indent,
 }
 #endif
 
+void VPRegionBlock::removeRegion() {
+  auto *Header = cast<VPBasicBlock>(getEntry());
+  VPBlockBase *Preheader = getSinglePredecessor();
+  auto *Exiting = cast<VPBasicBlock>(getExiting());
+
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ayalz wrote:

```suggestion
```

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