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

[Philip Reames via llvm-commits]

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@@ -482,11 +481,10 @@ InstructionCost RISCVTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
       //   vmsne.vi  v0, v8, 0
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preames wrote:

Unrelated codegen opportunity

 vmv.x.s a0, v8
 andi    a0, a0, 1
 vmv.v.x v8, a0

Could be a vrgather.vi 

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