From what I read the reason these use flags are masked is because llvm-3.3 was not yet in ~amd64. Now it is in ~amd64 so it should be unmasked. I will test it in the next 5 minutes and report back Reproducible: Always the line is =media-libs/mesa-9.1* r600-llvm-compiler video_cards_radeonsi
unmasked the use flags and llvm-3.3 failed to build :( but it was pulled in properly
radeonsi/r600-llvm-compiler flags have been unmasked some time ago already.