[llvm] [LV] Use vscale for tuning to improve branch weight estimates (PR #144733)

[David Sherwood via llvm-commits]

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@@ -7330,9 +7330,11 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
   VPlanTransforms::runPass(VPlanTransforms::unrollByUF, BestVPlan, BestUF,
                            OrigLoop->getHeader()->getContext());
   VPlanTransforms::runPass(VPlanTransforms::materializeBroadcasts, BestVPlan);
-  if (hasBranchWeightMD(*OrigLoop->getLoopLatch()->getTerminator()))
+  if (hasBranchWeightMD(*OrigLoop->getLoopLatch()->getTerminator())) {
+    std::optional<unsigned> VScale = CM.getVScaleForTuning();
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david-arm wrote:

NOTE: I'm forced to create a temporary variable here because `runPass` takes values by reference.

https://github.com/llvm/llvm-project/pull/144733