[llvm] [RISCV] Fix missing scaling by LMUL in cost model (PR #73342)

[Philip Reames via llvm-commits]

================
@@ -1163,7 +1165,7 @@ RISCVTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
     auto LT = getTypeLegalizationCost(RetTy);
     if (const auto *Entry = CostTableLookup(VectorIntrinsicCostTable,
                                             ICA.getID(), LT.second))
-      return LT.first * Entry->Cost;
+      return LT.first * TLI->getLMULCost(LT.second) * Entry->Cost;
----------------
preames wrote:

The cost table may be *wrong* and need updating, but the structure already accounts for LMUL scaling.  We could also rethink the table (i.e. have a table for linearly scaled cases, and one for all others), but that's different from the way this patch approaches it.

https://github.com/llvm/llvm-project/pull/73342