[PATCH] D159190: [RISCV]Combine to make the fixed vector vadd of splats are scalarized

[Luke Lau via Phabricator via llvm-commits]

luke added a comment.

In D159190#4634302 <https://reviews.llvm.org/D159190#4634302>, @luke wrote:

> But on RISC-V we'll need a vmv.x.s, so I don't think that qualifies as "free". But this is only if it's coming from a vector_shuffle if I understand correctly: build_vector splats and splat_vector splats should indeed be free because the extract_vector_elt will be combined away.

I gave this a try, and it sadly results in a lot of regressions: https://github.com/llvm/llvm-project/commit/0dee41b1ea16a022495a06680410090a25b5bb66
I haven't looked into it yet, but I'm definitely missing something


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