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

[Philip Reames via llvm-commits]

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@@ -523,9 +523,9 @@ InstructionCost RISCVTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
     if (LT.second.isFixedLengthVector())
       // vrsub.vi has a 5 bit immediate field, otherwise an li suffices
       LenCost = isInt<5>(LT.second.getVectorNumElements() - 1) ? 0 : 1;
-    // FIXME: replace the constant `2` below with cost of {VID_V,VRSUB_VX}
-    InstructionCost GatherCost =
-        2 + getRISCVInstructionCost(RISCV::VRGATHER_VV, LT.second, CostKind);
+    InstructionCost GatherCost = getRISCVInstructionCost(
+        {RISCV::VID_V, RISCV::VRSUB_VX, RISCV::VRGATHER_VV}, LT.second,
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preames wrote:

This bit isn't right.  In particular, it ignore the code two lines above which talks about different cases for costing the index sequence.  

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