Xtext grammar for LLVM MC assembler.

Hi,

I've developed a Machine Code assembler for an in-house micro-controller.
I would like to have an Eclipse integrated editor aware of the syntax of this controller.
For this, I have to write the Xtext grammar of this assembler.
This grammar is composed of two the parts: the controller instructions set (and addressing modes) but also the generic LLVM MC assembler directives('.equ','.byte,'.fill','.align',...).
I've already written the grammar for the instruction set.
I'm ready to start some reverse engineering on 'llvm/lib/MC/MCParser/AsmParser.cpp' to identify all the generic grammar rules.

But before starting this activity, is there already Xtext grammar for the generic directives of MC AsmParser?
Most of these directives are compatible with GNU toolchain, but I'm also looking for the documentation for these directives.

Regards, Dominique Torette.