The bitmanip extensions (Zba, Zbb, Zbc, Zbs) have been ratified some months ago, and would be very useful in how we generate instructions for certain operations. These would have to be detected at runtime. Once indicated as supported, we could generate much simpler instructions instead of the current overly-verbose implementations.
Bitmanip (Zba, Zbb, Zbc, Zbs) spec: https://github.com/riscv/riscv-bitmanip/releases/download/1.0.0/bitmanip-1.0.0-38-g865e7a7.pdf
<rdar://problem/90753636>