What a coincidence, I was trying to compile it yesterday but for instance, the `fp` register is not recognized. I can rename it to `s0` (a synonym) but I'm wondering what should I do to avoid this error:

    jonesforth.S:540: Error: illegal operands `addi fp,fp,-8'

Any idea?

For those interested, I'm using the nixpkgs cross-toolchain. Some documentation is here[0]. Here is a possible `shell.nix` file content:

    { pkgs ? import <nixpkgs> {} }:
    let
      riscv64-pkgs = import <nixpkgs> {
        crossSystem = (import <nixpkgs/lib>).systems.examples.riscv64;
      };
    in
    {
      riscv64 = riscv64-pkgs.mkShell {
        buildInputs = [
        ];
        nativeBuildInputs = [
          riscv64-pkgs.buildPackages.gdb
        ];
      };
    }

This works well enough to compile my hello-world example (available here[1]) but I'd like to use that `fp` register naming...

[0]: https://nixos.wiki/wiki/Cross_Compiling

[1]: https://github.com/noteed/riscv-hello-asm