[llvm] [VPlan] Extract reverse operation for reverse accesses (PR #146525)

[Mel Chen via llvm-commits]

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@@ -1541,6 +1541,12 @@ RISCVTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
                           cast<VectorType>(ICA.getArgTypes()[0]), {}, CostKind,
                           0, cast<VectorType>(ICA.getReturnType()));
   }
+  case Intrinsic::experimental_vp_reverse: {
+    return getShuffleCost(TTI::SK_Reverse,
+                          cast<VectorType>(ICA.getReturnType()),
+                          cast<VectorType>(ICA.getArgTypes()[0]), {}, CostKind,
+                          0, cast<VectorType>(ICA.getReturnType()));
+  }
   }
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Mel-Chen wrote:

Not worked. I still need this change to avoid getting Invalid cost. Do you know the reason?
```Cost of Invalid for VF vscale x 1: WIDEN-INTRINSIC vp<%9> = call llvm.experimental.vp.reverse(ir<%tmp>, ir<true>, vp<%5>)```


https://github.com/llvm/llvm-project/pull/146525