[llvm] [LoopVectorizer] Prune VFs based on plan register pressure (PR #132190)

[Sander de Smalen via llvm-commits]

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@@ -5027,6 +5025,9 @@ calculateRegisterUsage(VPlan &Plan, ArrayRef<ElementCount> VFs,
         if (isa<VPVectorPointerRecipe, VPVectorEndPointerRecipe,
                 VPBranchOnMaskRecipe>(R))
           continue;
+        if (auto *Phi = dyn_cast<VPReductionPHIRecipe>(R);
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sdesmalen-arm wrote:

nit: could you add a short comment describing the reason for this?

https://github.com/llvm/llvm-project/pull/132190