[llvm] [VPlan] Dispatch to multiple exit blocks via middle blocks. (PR #112138)

[via llvm-commits]

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@@ -3884,10 +3887,10 @@ class VPlan {
   /// whether to execute the scalar tail loop or the exit block from the loop
   /// latch.
   const VPBasicBlock *getMiddleBlock() const {
-    return cast<VPBasicBlock>(getVectorLoopRegion()->getSingleSuccessor());
+    return cast<VPBasicBlock>(getScalarPreheader()->getSinglePredecessor());
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ayalz wrote:

Works as long as the scalar preheader has a single predecessor, i.e., until runtime guards are introduced as additional predecessors.

https://github.com/llvm/llvm-project/pull/112138