[RISCV] Add cost for @llvm.vector.splice.{left,right}#179219

lukel97 merged 4 commits into

llvm:mainllvm/llvm-project:mainfrom

lukel97:riscv/splice-variable-offset-costmodellukel97/llvm-project:riscv/splice-variable-offset-costmodelCopy head branch name to clipboard