Gcode++

There is actually a "machine code" interpreter for LinuxCNC:

sim/axis/canterp will load a pluggable interpreter that sends "canonical motion commands" direct to the motion controller.

The input files look like this:
github.com/LinuxCNC/linuxcnc/blob/master.../canterp_example.can

However, much of the discussion of interpreter speed earlier is moot. The LinuxCNC interpreter has quite often interpreted and fully queued all the the machine motion before the cutter even touches the workpiece. The physical machine is so slow compared to the computer that there wouldn't be a problem parsing even a much more complex input language, such as STEP-NC.