One of the currently proposed draft ISA extensions for RISC-V is the Bit Manipulation Instructions extension (from henceonwards referred to as the “Bitmanip” or “BMI” extension.) It proposes to provide fast and direct instructions for commonly-used bitwise operations, often found in cryptographic, logarithmic, bit-counting, and logical operations. The GCC toolchain work has been developed by the community with contributions from SiFive and myself at Embecosm, providing bug fixes, regression tests, and benchmarks.
article: https://www.embecosm.com/2019/10/22/gcc-risc-v-bit-manipulation-extension/