Hi, Chen. Thanks for the patch. It's good to see scalar/vector cost patch since I was planning to add it long time ago but I failed to do that.
1. - I think it's better to specify the ratio by tune info (-mtune/-mcpu), I don't think we need to add param (not sure whether other RISC-V folks want it). - For non-integer ratio, I don't it's the common case that we should worry about. But if you really want to handle such cases, I think fractional-cost.h in aarch64 may be the good solution. 2. For gather_load/scatter_store tests, it's surprising that I didn't add -fno-vect-cost-model when I added those testcases （I think I wanted to introduce no-cost-model for such cases previously). So adding -fno-vecto-cost-model will be fine.
