Commit
a6805a0e02c98c1065038c0c75a25c45ee29b932
by kai.wang[RISCV] Define vadd/vsub/vrsub intrinsics and lower to V instructions.
This patch is based on the proposal from Roger Ferrer Ibanez.
http://lists.llvm.org/pipermail/llvm-dev/2020-October/145850.html
Differential Revision: https://reviews.llvm.org/D93013