I must admit that my knowledge of llvm is very limited. I did make the (perhaps wrong) assumption that it would be easier to understand on that basis alone (well, and the fact that the people writing it know how to code C++ properly, I guess for major projects like Gcc and llvm you may expect well engineered code). I felt that the whole macro business isn't as solid nowadays as what templates could allow in terms of type checking (and perhaps some macros involved for syntactic sugar alone; caveat with the cryptic error messages for errors in templates), hence my previously stated opinion.

Note that I am not complaining about the DSL, just how things are quite difficult to figure out (and untyped macros, as stated above).