[llvm] [RISCV][GISEL] Legalize and regbankselect vector typed G_IMPLICIT_DEF (PR #84553)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

> Did you try legalization of illegal types, e.g., LLT::scalable_vector(30, s1)?

Are you suggesting to allow or disallow illegal types? The current patch does not legalize them. I could add a test to demonstrate.

https://github.com/llvm/llvm-project/pull/84553