[llvm] [RISCV][CostModel] Estimate cost of Extract/InsertElement with non-constant index when vector instructions are not available (PR #67334)

[Philip Reames via llvm-commits]

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@@ -1456,6 +1456,24 @@ InstructionCost RISCVTTIImpl::getVectorInstrCost(unsigned Opcode, Type *Val,
       Opcode != Instruction::InsertElement)
     return BaseT::getVectorInstrCost(Opcode, Val, CostKind, Index, Op0, Op1);
 
+  // Extract/InsertElement with non-constant index is very costly without
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preames wrote:

Placement wise, this should probably be under the  if (!LT.second.isVector()) check below.

https://github.com/llvm/llvm-project/pull/67334