[llvm] [RISCV][TTI] Implement vector costs for `llvm.fpto{u|s}i.sat()`. (PR #143655)

[Matt Arsenault via llvm-commits]

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@@ -1497,6 +1497,33 @@ RISCVTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
                           cast<VectorType>(ICA.getArgTypes()[0]), {}, CostKind,
                           0, cast<VectorType>(ICA.getReturnType()));
   }
+  case Intrinsic::fptoui_sat:
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arsenm wrote:

I don't really understand this giant mess of TTI interfaces. The default should include an estimate based on the default expansion, but that doesn't mean the default should be assume the cost is the default expansion. It needs to account for the target making the base operation legal 

https://github.com/llvm/llvm-project/pull/143655