Bit manipulation extension[1] is finishing the public review and waiting for the rest of the ratification process, I believe that will become a ratified extension soon, so I think it's time to submit to upstream for review now :)
As the title included RFC, it's not a rush to merge to trunk yet, I would like to merge that until it is officially ratified. This patch set is the implementation of bit-manipulation extension, which includes zba, zbb, zbc and zbs extension, but only included in instruction/md pattern only, no intrinsic function implementation. Most work is done by Jim Willson and many other contributors on https://github.com/riscv-collab/riscv-gcc. [1] https://github.com/riscv/riscv-bitmanip/releases/tag/1.0.0