Dumping Low Level Intermediate Representation for Another Compiler

[Wei Qin <weiqin at gmail dot com>]

Hello GCC developers, 

I am avid user of gcc and have 5 cross-gcc's installed on my machine.
Thanks for your great work. Recently I want to do some compiler work
that involves analyzing low level intermediate representation. I
thought about using research compilers such as SUIF or SUIF II but
those lack maintenance and cannot even be built without much hacking.
So I am now considering using gcc. But since I am not familiar with
its source code structure, I am not comfortable to work directly on
it. Instead, I am thinking of dumping the MIPS RTL prior to the first
scheduling pass and then use an RTL parser to read it into another
compiler such as mach-SUIF. But the document says that RTL does not
contain all information of a source program, e.g. global variables. So
I wonder if there is a way for me to get complete low level MIPS IR
that is largely optimized but not register allocated. Or should I give
up this thought? Expert please advise.

Thanks in advance,

Wei