About GCJ compiler

[Mao Ito]

To whom may it concern,

Nice to meet you. I am Mao Ito and a graduate student at the University of Wisconsin-Madison.
I am working on a course project. My topic is something like "High Performance Architecture for Java Programming Language on mobile phones". On this project, I am planning to use GCJ to cross-compile Java for ARM.
I am planning to add some extra ISAs(Instruction Set Architecture). But, if I add an extra ISAs, as you know, I have to generate binary codes corresponding to my new architecture. My question is if I can modify GCJ for my purpose. Is it possible to get source codes and customize it?

Sincerely,
Mao Ito