Using the gcc c compiler with a custom set of mnemonics

[Daniel]

As I have written a register machine 

(see github.com/daknuett/py_register_machine ) 
I want to use a c compiler to compile programs for it.
I _do_ know, that I will have to face several issues with my machine,
but the main problem now ist, that I need a compiler.

So my question is: is there a easy way to use gcc with a custom set of
mnemonics/directives?

By the way: I need gcc just to compile the code to assembler.

As I my instruction set is different to the x86 set, I am not able to 
use the standart configuration.

Thank you in advance,
Daniel

PS: If it is too much effort to modify gcc, I will try to write a new
compiler (just for fun) .