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

[Alexey Bataev via llvm-commits]

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@@ -22334,10 +22384,28 @@ 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);
-    Value *BV = ShuffleBuilder.gather(GatheredScalars, ReuseMask.size());
-    ShuffleBuilder.add(BV, ReuseMask);
+    auto GatherUserOps = [&](SmallVectorImpl<TTI::BuildVectorUseOp> &UserOps) {
+      UserOps.clear();
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alexey-bataev wrote:

```suggestion
      UserOps.clear();
      if (NeedFreeze)
        return;
```

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