[PATCH] D99142: [RISCV] Add basic cost modelling for fixed vector gather/scatter.

Craig Topper via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Mar 23 08:56:53 PDT 2021


craig.topper added a comment.

In D99142#2644239 <https://reviews.llvm.org/D99142#2644239>, @frasercrmck wrote:

> I've not done much in this area of RISC-V, but I take it the non-vector costs are suitably higher than the vector costs? We'd still prefer to vectorize these?

The non-vector cost I think is just the same getMemoryOpCost call we're using here multiplied by VF. X86 adds a gather/scatter overhead cost on top of the element*getMemoryOpCost. It doesn't look like AArch64 adds any extra cost and they only support scalable vectors.

I think we'll compute the same cost for scalar loads/stores and gather/scatter with this patch. Hopefully vectorizing the GEP is accounted for separately.


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