If you're pursuing a Ph.D. project why would you commit to doing work for the creaky gcc infrastructure when it's clear that LLVM offers far more exciting opportunities?
gcc is dead. It served us very well, but it is time to move on.
As I understand it, a lot of researchers work on Clang/LLVM just because it allows them to focus on the aspect of the system they're interested in. For example, if you want to make a static analysis tool, you can do that with LLVM, but not with GCC. Also, and let's not mince words here, the LLVM codebase is a lot cleaner.
It seems like the open source community is working as it should here: someone designed a better mousetrap, and the world beat a path to his door. This is the way things should be, and the net result is going to be better open source software for everyone. Nobody wants to keep COBOL alive or CVS, so let's not be overly sentimental about gcc.
gcc is dead. It served us very well, but it is time to move on.