Maybe this is me coming from a C++ background rather than C, but that sounds like a horrible idea. That would mean that any code removed by a branch determinat

Maybe this is me coming from a C++ background rather than C, but that sounds like a horrible idea. That would mean that any code removed by a branch determination (e.g. if(0) in a macro/template expression) would be assumed to still exist for the further purpose of removing unused variables. Also, this would prevent one of the main benefits of function inlining. Once you have inlined a function, the values of some of the parameters may be known at compile time, resulting in lots of those if(0) parameters. But that is something that was relied on in previous passes, even though it is known to be a static value in the current pass.