Ilasm

From Mono Wiki

The Mono IL assembler. Comparable to the Microsoft ilasm.exe tool.

"we are only looking to change the backend engine for it (to Cecil).

But changing the back-end is not in the list for Mono 2.0, its a long-term strategy and will not have an impact in most of your work and contributions, it is just an internal goal of ours to consolidate around Cecil." [1]