[llvm] [RISCV][CostModel] Updates reduction and shuffle cost (PR #77342)

[Luke Lau via llvm-commits]

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@@ -482,11 +481,10 @@ InstructionCost RISCVTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
       //   vmsne.vi  v0, v8, 0
 
       return LT.first *
-             (TLI->getLMULCost(LT.second) + // FIXME: this should be 1 for andi
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lukel97 wrote:

To chime in here, it's defined in TargetTransformInfo.h as being a broadcast of element zero:

```c++
enum ShuffleKind {
    SK_Broadcast,        ///< Broadcast element 0 to all other elements.
```


https://github.com/llvm/llvm-project/pull/77342