[llvm] [RISCV][TTI] Add shuffle costing for masked slide lowering (PR #128537)

[Luke Lau via llvm-commits]

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@@ -203,6 +203,15 @@ bool getShuffleDemandedElts(int SrcWidth, ArrayRef<int> Mask,
                             const APInt &DemandedElts, APInt &DemandedLHS,
                             APInt &DemandedRHS, bool AllowUndefElts = false);
 
+/// Does this shuffle mask represent either one slide shuffle or a pair of
+/// two slide shuffles, combined with a select on some constant vector mask?
+/// A slide is a shuffle masks which shifts some set of elements up or down
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lukel97 wrote:

```suggestion
/// A slide is a shuffle mask which shifts some set of elements up or down
```

https://github.com/llvm/llvm-project/pull/128537