LLVM: popcnt instruction doesn't compile in LLVM 3.0
LLVM 3.0 compiles the popcnt instruction in a way unsupported by the Mac OSX system assembler. After talking to the LLVM folks it seems that they don't support the OSX system assembler anymore and suggested I use clang.
So this ticket is to track changing over to clang. Clang is included with OSX 10.6 and later.