Address review comment

Author: david-arm

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -7552,10 +7552,14 @@ VectorizationFactor LoopVectorizationPlanner::computeBestVF() {
   VPCostContext CostCtx(CM.TTI, *CM.TLI, Legal->getWidestInductionType(), CM,
                         CM.CostKind);
   precomputeCosts(BestPlan, BestFactor.Width, CostCtx);
-  assert((BestFactor.Width == LegacyVF.Width ||
-          (BestPlan.getVectorLoopRegion() &&
-           BestPlan.getVectorLoopRegion()->getSingleSuccessor() !=
-               BestPlan.getMiddleBlock()) ||
+  // Set PlanForEarlyExitLoop to true if the BestPlan has been built from a
+  // loop with an uncountable early exit. The legacy cost model doesn't
+  // properly model costs for such loops.
+  bool PlanForEarlyExitLoop =
+      BestPlan.getVectorLoopRegion() &&
+      BestPlan.getVectorLoopRegion()->getSingleSuccessor() !=
+          BestPlan.getMiddleBlock();
+  assert((BestFactor.Width == LegacyVF.Width || PlanForEarlyExitLoop ||
           planContainsAdditionalSimplifications(getPlanFor(BestFactor.Width),
                                                 CostCtx, OrigLoop) ||
           planContainsAdditionalSimplifications(getPlanFor(LegacyVF.Width),