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

[via llvm-commits]

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@@ -7859,6 +7855,9 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
       BestVPlan, BestVF,
       TTI.getRegisterBitWidth(TargetTransformInfo::RGK_FixedWidthVector));
   VPlanTransforms::removeDeadRecipes(BestVPlan);
+
+  VPBasicBlock *MiddleVPBB =
+      BestVPlan.getVectorLoopRegion() ? BestVPlan.getMiddleBlock() : nullptr;
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ayalz wrote:

Introduce closer to use - why hoist (from line 7964 below)?
If set to null, will its uses still work ok?
Should getMiddleBlock() return null in the absence of a vector loop region?

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