In case it’s useful, I’ve recently posted a RISC-V assembler written in Lisp on GitHub:
It’s designed for use with my Lisp interpreter, uLisp, that runs on RISC-V processors, to allow you to generate and run RISC-V machine code functions alongside Lisp. It currently supports the Sipeed Maixduino:
I hope to support the SiFive HiFive1 boards when Arduino support is available.