[PATCH] D152001: [RISCV][SLP] Inflate insert/extract costs on very small vectors

[ShihPo Hung via Phabricator via llvm-commits]

arcbbb added inline comments.


================
Comment at: llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp:1526
+    BaseCost += 2;
+
   return BaseCost + SlideCost;
----------------
arcbbb wrote:
> Is it needed for CostKind == TTI::TCK_CodeSize ?
> 
> I was thinking the total cost was composed of vmv instruction (BaseCost) and vslide instruction (SlideCost).
> IIUC, BaseCost includes vector-scalar communication cost, and the addend `2` here accounts for this.
Considering that the addend accounts for the communication cost, it may not be necessary to impose limitations on the VF.


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  https://reviews.llvm.org/D152001/new/

https://reviews.llvm.org/D152001