Books/articles about gcc internals (compiler backends, machine description, RTL)?

Question

Programming

I need to fix gcc to add some new instructions to my cpu.
I have read info gccint, but the information there is rather scarce. While she let me do what I wanted, I still have a lot of questions about patterns in .md files.
Are there any books/articles that describe the gcc backend development process, detailing which constructs to use when in .md?
Using the link from ftp.axis.se/pub/users/hp/pgccfd/pgccfd-0.5.pdf I found Stallman's book "Using and Porting Gnu CC" , quite old though. This is the same gccint. Anything else?

Answer 1

https://gcc.gnu.org/onlinedocs/ -off documentation
www.cse.iitb.ac.in/grc/slides/cgotut-gcc/topic5-md... -small manual
www.redhat.com/magazine/ 002dec04/features/gcc
S.Muchnick. Advanced compiler design and implementation. Morgan Kaufmann, 1997.
GCC internal documentation. gcc.gnu.org/onlinedocs/gccint
Presentations on GCC internals. www.airs.com/dnovillo/200711-GCC-Internals
Proceedings of the 2nd HIPEAC GCC Conference. www.hipeac.net/node/746
Proceedings of the GCC Developers Conference. www.gccsummit.org