Shameless plug: http://cwerg.org http://cwerg.org Cwerg has backends for x86-64, Aarch64, Arm32 (non-thumb) and can produce executables, i.e. comes with an as

Shameless plug: http://cwerg.org http://cwerg.org Cwerg has backends for x86-64, Aarch64, Arm32 (non-thumb) and can produce executables, i.e. comes with an assembler. It is however fairly opinionated in many ways.