[llvm] [VPlan] Introduce explicit ExtractFromEnd recipes for live-outs. (PR #100658)

[via llvm-commits]

================
@@ -8660,6 +8757,14 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
   // After here, VPBB should not be used.
   VPBB = nullptr;
 
+  assert(isa<VPRegionBlock>(Plan->getVectorLoopRegion()) &&
+         !Plan->getVectorLoopRegion()->getEntryBasicBlock()->empty() &&
+         "entry block must be set to a VPRegionBlock having a non-empty entry "
+         "VPBasicBlock");
----------------
ayalz wrote:

```suggestion
         "Vector loop region must be set to a VPRegionBlock having a non-empty entry "
         "VPBasicBlock");
```
independent, while we're here

https://github.com/llvm/llvm-project/pull/100658