Need help on GCC GIMPLE

I have been looking into GCC's GIMPLE and building a front-end. I have been looking through the codebase, however wrapp开发者_高级运维ing my head around all the concepts is taking more time than I would like due to what appears to be a lack of documentation. Are there resources online that explain how GIMPLE works?

I have found the following, where the PDF was quite informative: http://gcc.gnu.org/wiki/GIMPLE

have a look here: GCC Frontend HOWTO...
and here: from the gcc resource center, IIT Bombay.

Some useful information on GIMPLE and GIMPLE-SSA can be found here: http://www.cri.ensmp.fr/classement/doc/A-381.pdf