[llvm] [VPlan] Explicitly unroll replicate-regions without live-outs by VF. (PR #170212)

[Andrei Elovikov via llvm-commits]

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@@ -263,6 +263,13 @@ class VPBlockUtils {
     Old->clearSuccessors();
   }
 
+  /// Clone the CFG for all nodes reachable from \p Entry, including cloning
+  /// the blocks and their recipes. Operands of cloned recipes will NOT be
+  /// updated. Remapping of operands must be done separately. Returns a pair
+  /// with the new entry and exiting blocks of the cloned region. If \p Entry
+  /// isn't part of a region, return nullptr for the exiting block.
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eas wrote:

I understand this is just a copy, but why such weird semantics for the regions? Can we just change it to require to pass the region itself if we want to clone one?

https://github.com/llvm/llvm-project/pull/170212