[llvm] [RISCV][CostModel] Correct the cost of some reductions (PR #118072)

[Luke Lau via llvm-commits]

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@@ -1556,15 +1563,15 @@ RISCVTTIImpl::getArithmeticReductionCost(unsigned Opcode, VectorType *Ty,
     break;
   case ISD::OR:
     SplitOp = RISCV::VOR_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDOR_VS, RISCV::VMV_X_S};
+    Opcodes = {RISCV::VREDOR_VS, RISCV::VMV_X_S};
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lukel97 wrote:

Can you update the comment above as well, or add a comment here just to point out that we can reuse the vs2 for vs1

https://github.com/llvm/llvm-project/pull/118072