[llvm] [SLP] More accurately cost RISCV scalar splats (PR #213104)

[Ryan Buchner via llvm-commits]

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@@ -22858,6 +22669,9 @@ ResTy BoUpSLP::processBuildVector(const TreeEntry *E, Type *ScalarTy,
     // Gather unique scalars and all constants.
     SmallVector<int> ReuseMask(GatheredScalars.size(), PoisonMaskElem);
     TryPackScalars(GatheredScalars, ReuseMask, /*IsRootPoison=*/true);
+    if constexpr (std::is_same_v<BVTy, ShuffleCostEstimator>)
+      ShuffleBuilder.checkForFoldingSplat(E, ReuseMask);
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bababuck wrote:

Thanks for the clarification, this helps lots, working on the updates!

https://github.com/llvm/llvm-project/pull/213104