Compilation speed improvements in LLVM:
Optimize link stage by writing a single LLVM program to do llvm-link + dce/other linktime opts we do + llvm-dis. That would just avoid serializing/desearializing the whole LLVM module between the steps, which we currently do twice unnecessarily.
Write an LLVM minifier IR pass. Does not need to be perfect, but reducing identifier size as early as possible would reduce overall compilation memory use and likely give a nice speedup
Finish libcxx test suite passing.
Proper port of the SDL2 codebase from source (currently we have an SDL1.3 implementation of our own, which has various limitations, and SDL2's source has a license we can accept).
Finish Regal integration, to potentially replace or be an option alongside our current GL emulation support for legacy GL stuff.