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

[via llvm-commits]

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@@ -527,6 +549,14 @@ void VPBasicBlock::execute(VPTransformState *State) {
 
   // 2. Fill the IR basic block with IR instructions.
   executeRecipes(State, NewBB);
+
+  // If this block is a latch, update CurrentParentLoop.
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ayalz wrote:

Checking if current canonical block `isLatch` could be done by checking if its 2nd successor `isHeader`?
(Preheader has a single successor whereas latch of canonicalized vector loop has two, with header as 2nd).

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