Should this live in RISCVISAInfo.h rather than be a Clang-specific thing given it's just for squeezing version info into the preprocessor? I can't think of a use for it outside that at the moment.
This patch has the version value calculation in RISCVISAInfo.h, so sorry I don't quite get what you mean. Do you mean specifically __riscv_v_intrinsic macro?
If you mean to have macro information under the RISCVExtensionInfo, I don't see the need here as there are macro like __riscv_v_min_vlen that can be implied by multiple macro-s.