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

[via llvm-commits]

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@@ -3869,6 +3866,10 @@ class VPRegionBlock : public VPBlockBase {
   /// Clone all blocks in the single-entry single-exit region of the block and
   /// their recipes without updating the operands of the cloned recipes.
   VPRegionBlock *clone() override;
+
+  /// Remove the current region from its VPlan, connecting its predecessor to
+  /// its entry and exiting block to its successor.
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ayalz wrote:

```suggestion
  /// its entry, and its exiting block to its successor.
```

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